1. Gel Treatment
Using Gel is a newer and better method of controlling cockroaches. It has revolutionized
pest control in modern times. You don't have the unpleasant smell of insecticides. You don't
have to remove anything from the kitchen. You don't have to close your house and go away
and there is no mess caused by spraying of insecticides, to be cleared.
Method of Treatment:
Minute amounts of Gel are applied in strategic locations with the help of a syringe.
Cockroaches are mostly in the kitchen and pantries and we concentrate on these areas,
although the Gel is applied in the toilet and the entire premises. The method of application
of Gel is such that it is inaccessible to infants and pets.
How Gel Works:
Gel has an edible product specially attractive to cockroaches. Gel has a cascading effect.
Once some cockroaches have eaten Gel they contaminate other cockroaches also and the
result is better control over the population of cockroaches.
Gel can be applied to sensitive areas such as electrical control boxes, kitchen appliances,
computers etc. on which water based insecticide cannot be sprayed.
Back to Products & Services
Life Cycle / Egg / Larva / Pupa / Adult
There are over 2500 different species of mosquitoes throughout the world of which 150
species occur in the United States. 52 species occur in California, and 19 species occur
in Alameda County. In the course of the District's operation about 10 species are

2. commonly found in the County. Eight of the species account for over 99% of complaints
from the public.
Each of the species has a scientific name that is latin, such as Culex tarsalis. These
names are used in a descriptive manner so that the name tells something about this
particular mosquito. Some species have what is called "common names" as well as
scientific names, such as Anopheles freeborni, the "Western malaria mosquito".
All mosquitoes must have water in which to complete their life cycle. This water can
range in quality from melted snow water to sewage effluent and it can be in any
container imaginable. The type of water in which the mosquito larvae is found can be an
aid to the identification of which species it may be. Also, the adult mosquitoes show a
very distinct preference for the types of sources in which to lay their eggs. They lay their
eggs in such places such as tree holes that periodically hold water, tide water pools in
salt marshes, sewage effluent ponds, irrigated pastures, rain water ponds, etc. Each
species therefore has unique environmental requirements for the maintenance of its life
cycle.
The feeding habits of mosquitoes are quite unique in that it is only the adult females that
bite man and other animals. The male mosquitoes feed only on plant juices. Some
female mosquitoes prefer to feed on only one type of animal or they can feed on a
variety of animals. Female mosquitoes feed on man, domesticated animals, such as
cattle, horses, goats, etc; all types of birds including chickens; all types of wild animals
including deer, rabbits; and they also feed on snakes, lizards, frogs, and toads.
Most female mosquitoes have to feed on an animal and get a sufficient blood meal
before she can develop eggs. If they do not get this blood meal, then they will die
without laying viable eggs. However, some species of mosquitoes have developed the
means to lay viable eggs without getting a blood meal.
The flight habits of mosquitoes depend again on the species with which we are dealing.
Most domestic species remain fairly close to their point of origin while some species
known for their migration habits are often an annoyance far from their breeding place.
The flight range for females is usually longer than that of males. Many times wind is a
factor in the dispersal or migration of mosquitoes. Most mosquitoes stay within a mile or
two of their source. However, some have been recorded as far as 75 miles from their
breeding source.
The length of life of the adult mosquito usually depends on several factors: temperature,
humidity, sex of the mosquito and time of year. Most males live a very short time, about
a week; and females live about a month depending on the above factors.
Return to Information Directory

3. Mosquito Life Cycle
The mosquito goes through four separate and distinct stages of its life cycle and they
are as follows: Egg, Larva, pupa, and adult. Each of these stages can be easily
recognized by their special appearance. There are four common groups of mosquitoes
living in the Bay Area. They are Aedes, Anopheles, Culex, and Culiseta.
Egg : Eggs are laid one at a time and they float on the surface of the water. In the case
of Culex and Culiseta species, the eggs are stuck together in rafts of a hundred or more
eggs. Anopheles and Aedes species do not make egg rafts but lay their eggs
separately. Culex, Culiseta, and Anopheles lay their eggs on water while Aedes lay their
eggs on damp soil that will be flooded by water. Most eggs hatch into larvae within 48
hours.
Larva : The larva (larvae - plural) live in the water and come to the surface to breathe.
They shed their skin four times growing larger after each molting. Most larvae have
siphon tubes for breathing and hang from the water surface. Anopheles larvae do not
have a siphon and they lay parallel to the water surface. The larva feed on micro-
organisms and organic matter in the water. On the fourth molt the larva changes into a
pupa.
Pupa: The pupal stage is a resting, non-feeding stage. This is the time the mosquito
turns into an adult. It takes about two days before the adult is fully developed. When
development is complete, the pupal skin splits and the mosquito emerges as an adult.
Adult: The newly emerged adult rests on the surface of the water for a short time to
allow itself to dry and all its parts to harden. Also, the wings have to spread out and dry
properly before it can fly.

4. The egg, larvae and pupae stages depend on temperature and species characteristics
as to how long it takes for development. For instance, Culex tarsalis might go through
its life cycle in 14 days at 70 F and take only 10 days at 80 F. Also, some species have
naturally adapted to go through their entire life cycle in as little as four days or as long
as one month.
The following pages show a typical mosquito egg raft, larva, pupa, and adult, and
explains more about each stage.
Return to Information Directory
Mosquito Egg Raft
Culex mosquitoes lay their eggs on the surface of fresh or stagnant water. The water
may be in tin cans, barrels, horse troughs, ornamental ponds, swimming pools, puddles,
creeks, ditches, or marshy areas. Mosquitoes prefer water sheltered from the wind by
grass and weeds.
Culex mosquitoes usually lay their eggs at night. A mosquito may lay a raft of eggs
every third night during its life span.
Culex mosquitoes lay their eggs one at a time, sticking them together to form a raft of
from 200- 300 eggs. A raft of eggs looks like a speck of soot floating on the water and is
about 1/4 inch long and 1/8 inch wide.
Tiny mosquito larvae emerge from the eggs within 24 hours.
Notes: Anopheles mosquitoes lay their eggs singly on the water, not in rafts. Aedes
mosquitoes lay their eggs singly on damp soil. Aedes eggs hatch only when flooded
with water (salt water high tides, irrigated pastures, treeholes, flooded stream bottoms,
etc.).
Return to Information Directory

5. Mosquito Larva
Mosquito larvae, commonly called "wigglers" or "wrigglers", must live in water from 7 to
14 days depending on water temperature.
Larvae must come to the surface at frequent intervals to obtain oxygen through a
breathing tube called a siphon. The larva eats algae and small organisms which live in
the water.
During growth, the larva molts (sheds its skin) four times. The stages between molts are
called instars. At the 4th instar, the larva reaches a length of almost 1/2 inch.
When the 4th instar larva molts it becomes a pupa.
Note : Anopheles are unlike Culex and Aedes larvae since they do not have a breathing
tube, they must lie parallel to the water surface in order to get a supply of oxygen
through a breathing opening.
Return to Information Directory
Mosquito Pupa
Mosquito pupae, commonly called "tumblers", must live in water from 1 to 4 days,
depending upon species and temperature.
The pupa is lighter than water and therefore floats at the surface. It takes oxygen

6. through two breathing tubes called "trumpets". When it is disturbed it dives in a jerking,
tumbling motion and then floats back to the surface. The pupa does not eat.
The metamorphosis of the mosquito into an adult is completed within the pupal case.
The adult mosquito splits the pupal case and emerges to the surface of the water where
it rests until its body can dry and harden.
Return to Information Directory
Mosquito Adult
Only female mosquitoes bite animals and drink blood. Male mosquitoes do not bite, but
feed on the nectar of flowers.
Aedes mosquitoes are painful and persistent biters, attacking during daylight hours (not
at night). They do not enter dwellings, and they prefer to bite mammals like humans.
Aedes mosquitoes are strong fliers and are known to fly many miles from their breeding
sources.
Culex mosquitoes are painful and persistent biters also, but prefer to attack at dusk and
after dark, and readily enter dwellings for blood meals. Domestic and wild birds are
preferred over man, cows, and horses. Culex tarsalis is known to transmit encephalitis
(sleeping sickness) to man and horses. Culex are generally weak fliers and do not move
far from home, although they have been known to fly up to two miles. Culex usually live
only a few weeks during the warm summer months.
Those females which emerge in late summer search for sheltered areas where they
"hibernate" until spring. Warm weather brings her out in search of water on which to lay
her eggs.
Culiseta mosquitoes are moderately aggressive biters, attacking in the evening hours
or in shade during the day.
Anopheles mosquitoes are the only mosquito which transmits malaria to man.
Mosquito adult, larva and pupa drawings modified from Aquatic Entomology , by W. Patrick
McCafferty; Illustrations by Arwin V. Provonsha; Jones and

7. demiology
Frequency
United States
In the United States, approximately 4 million people are believed to be infected.[1] High-risk
groups include international travelers, recent immigrants (especially from Latin America and
Asia), refugees, and international adoptees. Ascariasis is indigenous to the rural southeast, where
cross-infection by pigs with the nematode Ascaris suum is thought to occur. (Children aged 2-10
years are thought to be more heavily infected in this and all other regions.)
International
Worldwide, 1.4 billion people are infected with A lumbricoides, with prevalence among
developing countries as low as 4% in Mafia Island, Zanzibar,[2] to as high as 90% in some areas
of Indonesia. Local practices (eg, termite mound–eating in Kenya[3] ) may predispose to
ascariasis in some populations. Other risk factors like dog/cat ownership, presence of pets within
the house, and a previous history of geophagia have been noted. In some regions, Ascaris
infection is thought to contribute significantly to the burden of abdominal surgical emergencies.
Mortality/Morbidity
The rate of complications secondary to ascariasis ranges from 11-67%, with intestinal and biliary
tract obstruction representing the most common serious sequelae. Although infection with A
lumbricoides is rarely fatal, it is responsible for an estimated 8,000-100,000 deaths annually,
mainly in children, usually from bowel obstruction or perforation in cases of high parasite
burden. Due to similarities in the means of infection, many individuals infected with Ascaris are
also co-infected with other intestinal parasites.
Race
No racial predilection is known. A genetic predisposition has been described in a study of
families from Nepal.[4]
Sex
Male children are thought to be infected more frequently, owing to a greater propensity to eat
soil.
Age
Children, because of their habits (eg, directly or indirectly consuming soil), are more commonly
and more heavily infected than adults. Neonates may be infected by transplacental infection.

8. Frequently, families may be infected and reinfected in group fashion due to shared food and
water sources as well as hygiene practices.
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14. The Mosquito Life Cycle
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By sharkarama
A Look into the Life Cycle of the Mosquito Species and
What Makes Them Treat You the Way That They Do
Have you ever actually thought about the mosquito anatomy or how mosquitoes turn into the
blood sucking creatures that everyone loves to hate? For most, the answer to that question is
probably an extra large NO. With the world's largest mosquito reaching 1.5 inches in length and
the smallest being almost invisible to the eye, mosquitoes and mosquito facts can be just as

15. riveting as any other subject's story. Understanding the life cycle of a mosquito and what makes
these mosquitoes tick can also help you be prepared for when they decide to invade your territory
which includes your own skin.
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The Life Cycle of a Mosquito
Like most creatures of the Earth, the mosquito goes through various stages before it becomes a
full, grown adult. While the mosquito life span may not be very long - a female mosquito may
only live for 3 to 100 days while a male mosquito may last for about 10 to 20 days - they go
through a lot to get to the point where your blood is their favorite course. This life cycle can be
broken up into a few basic parts which are:
The Egg Stage
The Larva Stage
The Pupa Stage
The Adult Stage
These four main stages follow the mosquito lifespan from beginning to end. Thankfully, as you
already know, this life won't last long enough to do mass amounts of damage, but is just long
enough to possibly aggravate your life.

16. A Mosquito Laying Eggs
Mosquito Eggs
As one may expect, the egg stage for the mosquito is the first stage. Also as one may expect,
these eggs do not just appear out of thin air. Yep you guessed it; they come from a mother
mosquito that can produce up to 250 eggs at a time. These 250 eggs can only come about after
the female mosquito feasts on at least one blood meal in order to have enough nutrients for the
mass amount of mosquito eggs to be born. Once enough nutrients are consumed, possibly from
your very own blood, it is time to watch out.
Watch out because within 48 to 72 hours, those eggs will be hatching into the next stage of the
mosquito lifecycle. Before you start really getting scared, there are a few common places that
female mosquitoes love to lay their eggs. You just may be able to find the root of a mosquito
infestation without having to look too hard. Here are the most common places you will find a
mosquito eggs waiting to hatch and take over the world:
The top surface of any stagnant water
A depression or ridge of a container where rain water collects
Close to small bodies of water such as ponds or moats
Inside marshlands
The inside of an outdoor flower pot
Basically, wherever there is an ideal aquatic location, a mosquito habitat will be formed. If you
do find a nest, then it is most certainly time to get to work. You can spray down the area with an
aerosol mosquito killer, but that is not the best thing to do for the environment. Instead, you may
want to use a product like a Mosquito Trap, a safe and technologically proven device that will
get rid of those pesky insects in your life.

17. Mosquito Larvae
Mosquito Larvae
Mosquito larvae and mosquito larva pictures are an interesting sight to see. Commonly referred
to as "Wrigglers", these newly hatched insects can be seen wriggling up and down from the
surface of the water. Get too close, though, and they will seemingly disappear. This is because
the larvae are on a mission to protect themselves from mosquito predators. So to keep themselves
safe, they quickly dive to the bottom of whatever water they were born into.
Within five to six days, the mosquito larvae stage is complete. In this time period, the insects
start to take form. A nicely shaped head and legs can been detected along with a wider thorax
stemming from the abdomen. At the tip of the abdomen is where the siphon is found, which
allows the larvae to breathe air from the surface. Some mosquito larvae do not have this siphon
and get their air from the dorsal surface of the abdomen.
There are many mosquito types, but no matter how they get their air, these larvae are on the
verge of stepping into their next stage which is known as the Pupa stage. This means that they
are also almost ready to introduce themselves into the living world and maybe to your flesh.
The Pupa Stage
When it comes to mosquito pictures, the pupa stage is not the most photographed of the
mosquito stages. While an adult mosquito picture may be common, yet hard to get, the pupa
stage is pretty much impossible to capture. This is mostly due to the fact that the pupa stage of
mosquitoes causes these forming insects to somersault through the water. Staying close to the

18. surface for air until they are disturbed, mosquito pupae finish this stage in about two to three
days.
Adult Female Mosquito
The Adult Stage
After their brief stint with metamorphosis, the hatched eggs are finally ready to step into
adulthood. And seeming we are not considered mosquito eaters, that is bad news for us. While
vegans may value mosquito life, most would rather dispose of these adult bugs before they
become too big of a problem.
When it comes down to it though, it is the female mosquito that is really the arch nemesis of
humankind. Here is what the female mosquitoes of the world love to eat:
Plant Nectar
Honey Dew
Sugar Sources
Your Blood
Depending on their species, some females do indulge themselves on other animals such as birds
and horses. So for all of you who are just expecting to go and stick mosquito eating birds in your
backyard, think again. The same goes for male mosquitoes, minus the feasting on blood.
So how exactly does the female get to your blood? Does it have teeth and if so how many teeth
does a mosquito have? The answers to these questions are simple, yet at the same time tricky.
Mosquitoes technically do not have teeth but do have serrated teeth that surround a pair of thin
tubes. The tubes are used for:
Dripping a Pain Suppressor
Sucking Blood
And those are two things that could most certainly start your day off all wrong. The mosquitoes
most commonly found around homes will follow this protocol in order to get the nutrients they
need from your blood:

19. 1. Stab the skin
2. Saw into the skin
3. Shoot saliva mixed with an anesthetic so you will never notice
4. Shoot an anticoagulant into you in order for the blood to keep flowing freely
Once the female feeds off of you, the life cycle of the mosquito is almost through. All that is left
is for her to go lay her eggs and begin the cycle for a new batch of blood thirsty villains all over
again.
DEET Spray
What You Can Do
The best thing that you can do to protect yourself from mosquito bites and potential mosquito
borne diseases is be prepared for the worst. You don't have to know mosquito identification,
mosquito classification, or the scientific name in order to stop the pesky buggers from flying
your way. All you really need is a mosquito control product like DEET spray for your skin, a
mosquito net for your yard, or a Mega-Catch mosquito trap for your yard or hallway. As long as
you have these products by your side, you won't have to worry about having nightmares about
mosquito eyes lurking in the night. A sensible and safe plan is all you really need.

20. Mosquito Trap
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21. WUMCD Menu
District Information
- About the District
- Integrated Mosquito Management
- Management / Key Personnel
- Board of Trustees
- Budget Committee
- District History
- Professional Affiliations
- Directions to Office
- Contact Us
Mosquito Information
- Introduction
- The Name "Mosquito"
- Mosquito Life Cycle
- Mosquito Egg Raft
- Mosquito Larvae
- Mosquito Pupae
- Mosquito Adult
Disease Information
- West Nile Virus
- St. Louis Encephalitis
- Western Equine Encephalitis
- Lyme Disease
- Canine Heartworm

22. Mosquito Fish
Service Requests
- Mosquito Control
- No Spray
Mosquito Surveillance
Adult Surveillance
- Mosquito Light Traps
- Mosquito Landing Rates
Disease Surveillance
- Sentinel Chickens
- Mosquito Pools
- Wild Bird Testing
- If You Find a Dead Bird...
Mosquito Control
- Larval Mosquito Control
- Adult Mosquito Control
Videos
Press Releases
WUMCD Home Page
MOSQUITO LIFE CYCLE
The mosquito goes through four separate and distinct stages of its life
cycle: Egg, Larva, Pupa, and Adult. Each of these stages can be easily
recognized by its special appearance.
Egg: Eggs are laid one at a time or attached together to form "rafts."
They float on the surface of the water. In the case of Culex and
Culiseta species, the eggs are stuck together in rafts of up to 200.
Anopheles, Ochlerotatus and Aedes , as well as many other genera, do
not make egg rafts, but lay their eggs singly. Culex, Culiseta, and
Anopheles lay their eggs on the water surface while many Aedes and
Ochlerotatus lay their eggs on damp soil that will be flooded by water.
Most eggs hatch into larvae within 48 hours; others might withstand
subzero winters before hatching. Water is a necessary part of their
habitat.

23. Larva: The larva (plural - larvae) lives in the water and comes to the
surface to breathe. Larvae shed (molt) their skins four times, growing
larger after each molt. Most larvae have siphon tubes for breathing
and hang upside down from the water surface. Anopheles larvae do
not have a siphon and lie parallel to the water surface to get a supply
of oxygen through a breathing opening. Coquillettidia and Mansonia
larvae attach to plants to obtain their air supply. The larvae feed on
microorganisms and organic matter in the water. During the fourth
molt the larva changes into a pupa.
Pupa: The pupal stage is a resting, non-feeding stage of development,
but pupae are mobile, responding to light changes and moving
(tumble) with a flip of their tails towards the bottom or protective
areas. This is the time the mosquito changes into an adult. This
process is similar to the metamorphosis seen in butterflies when the
butterfly develops - while in the cocoon stage - from a caterpillar into
an adult butterfly. In Culex species in the southern United States this
takes about two days in the summer. When development is complete,
the pupal skin splits and the adult mosquito (imago) emerges.
Adult: The newly emerged adult rests on the surface of the water for a
short time to allow itself to dry and all its body parts to harden. The
wings have to spread out and dry properly before it can fly. Blood
feeding and mating does not occur for a couple of days after the adults
emerge.
How long each stage lasts depends on both temperature and species
characteristics. For instance, Culex tarsalis, a common California
(USA) mosquito, might go through its life cycle in 14 days at 70� F
and take only 10 days at 80� F. On the other hand, some species
have naturally adapted to go through their entire life cycle in as little
as four days or as long as one month.
The following pictures show a typical mosquito egg raft, larva, pupa,
and adult, and explain more about each stage.

24. West Umatilla Mosquito Control District
3005 South 1st Street, Hermiston, OR 97838
info@w

25. at Life Cycle
Only the life cycle of the Roof Rat (rattus rattus) is discussed on this page, since this is the
only rat that is common here in central Florida.
Roof Rats are born in a nest, in a litter of 6-8
young. The nest is often in a secure place with
nesting debris such as in an attic in the
insulation. They are born tiny and hairless
(pinkies), with eyes sealed shut. After two
weeks of nursing, their eyes open, and within 4
weeks, they are weaned. After three months of
life, they are independent and on their own,
although they typically use the same habitat as
their birthplace (i.e. they live in the same home
or attic).
Here we can see a photo of a juvenile rat and a
mature adult rat. Older ones sometimes tend to
brown a bit, although most of the rats we catch
are gray. A lot of the rats that we catch are small
rats. This is because they breed in such high
numbers, and there are so many young ones.
When we're trapping rats in an attic, we'll often
get a big one or two, and a number of small
ones. This is not the rule, but it does happen
from time to time, indicating a possible family
of rats.
Rats don't live particularly long in the wild.
Like all rodents, they rely upon breeding in high
numbers and eating a lot and growing quickly.
In this respect, they are somewhat like insects,
and thus can sometimes swell to large numbers
given the right conditions. In normal
circumstances, disease and predators keep their
numbers in check. Rarely do rats live for more
than a year in the wild. During that year,
however, they can create a lot of new rats and a
lot of damage. Just one adult female can create
more than 40 new rats in a year. In their

26. lifetime, rats tend to stick to
familiar territory. They are not explorers. They find an area that suits their needs, with shelter
and food (human homes and attics quite often fit the bill) and rarely venture more than a few
hundred feet from that area. They rarely die naturally, but when they do, it's often in safe
place like your attic, and you'll notice the smell. Most will be killed by predators or
OrlandoRats, Inc. However, they'll leave their damage and their offspring behind.
© 2011 OrlandoRats - site content, photos, & maintenance by Orlando Rat Removal,
original site by Moonrise Group, Inc
Tel: 407-284-7081 • Fax: 407-264-8890 • gregg@orlandorats.com • Residential
(Redirected from Brown Rat)
"Rattus norvegicus" redirects here. For the album, see Rattus Norvegicus (album).
Brown rat
Conservation status
Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia

27. Family: Muridae
Subfamily: Murinae
Genus: Rattus
Species: R. norvegicus
Binomial name
Rattus norvegicus
(Berkenhout, 1769)
Brown rat range
The brown rat, common rat, sewer rat, Hanover rat, Norway rat, Brown Norway rat,
Norwegian rat, or wharf rat (Rattus norvegicus) is one of the best known and most common
rats.
One of the largest muroids, it is a brown or grey rodent with a body up to 25 cm (10 in) long, and
a similar tail length; the male weighs on average 350 g (12 oz) and the female 250 g (9 oz).
Thought to have originated in northern China, this rodent has now spread to all continents,
except Antarctica, and is the dominant rat in Europe and much of North America—making it the
most successful mammal on the planet after humans.[2] Indeed, with rare exceptions the brown
rat lives wherever humans live, particularly in urban areas.
Selective breeding of Rattus norvegicus has produced the laboratory rat, an important model
organism in biological research, as well as pet rats.
Contents
[hide]
1 Naming and etymology
2 Description
3 Biology and behavior
o 3.1 Communication
 3.1.1 Chirping
 3.1.2 Audible communication
o 3.2 Diet
o 3.3 Reproduction and life cycle
o 3.4 Social behavior
o 3.5 Burrowing
4 Distribution and habitat

28. o 4.1 Alaska
o 4.2 Alberta, Canada
o 4.3 New Zealand
5 Diseases
6 In captivity
o 6.1 Uses in science
o 6.2 As pets
7 References
8 External links
[edit] Naming and etymology
Originally called the "Hanover rat" by people wishing to link problems in 18th century England
with the House of Hanover,[3] it is not known for certain why the brown rat is named Rattus
norvegicus (Norwegian rat) as it did not originate from Norway. However, the English naturalist
John Berkenhout, author of the 1769 book Outlines of the Natural History of Great Britain, is
most likely responsible for popularizing the misnomer. Berkenhout gave the brown rat the
binomial name Rattus norvegicus believing that it had migrated to England from Norwegian
ships in 1728, although no brown rat had entered Norway at that time.
By the early to middle part of the 19th century, British academics were aware that the brown rat
was not native to Norway, hypothesizing (incorrectly) that it may have come from Ireland,
Gibraltar or across the English Channel with William the Conqueror.[4] As early as 1850,
however, a more correct understanding of the rat's origins was beginning to develop.[5] The
British novelist Charles Dickens acknowledged the misnomer in the 2 June 1888 edition of his
weekly journal, All the Year Round, writing:
"Now there is a mystery about the native country of the best known species of rat, the common
brown rat. It is frequently called, in books and otherwise, the 'Norway rat,' and it is said to have
been imported into this country in a ship-load of timber from Norway. Against this hypothesis
stands the fact that when the brown rat had become common in this country, it was unknown in
Norway, although there was a small animal like a rat, but really a lemming, which made its home
there."[6]
Academics began to understand the origins and corrected etymology of the brown rat towards the
end of the 19th century, as seen in the 1895 text Natural History by American scholar Alfred
Henry Miles:
"The brown rat is the species common in England, and best known throughout the world. It is
said to have travelled from Persia to England less than two hundred years ago and to have spread
from thence to other countries visited by English ships."[7]
Though the assumptions surrounding this species' origins were not yet entirely accurate, by the
20th century it was established among naturalists that the brown rat did not originate in Norway,

29. rather that the species came from central Asia and (likely) China.[8] Despite this, this species'
common name of "Norway rat" is still in use today.
[edit] Description
Comparison of the physique of a black rat (Rattus rattus) with a brown rat (Rattus norvegicus)
The fur is coarse and usually brown or dark grey, while the underparts are lighter grey or brown.
The length can be up to 25 cm (10 in), with the tail a further 25 cm (10 in), the same length as
the body. Adult body weight averages 550 g (19 oz) in males and about 350 g (12 oz) in females,
but a very large individual can reach 900 g (32 oz). Rats weighing over 1 kg (2.2 lb) are
exceptional, and stories of rats as big as cats are exaggerations, or misidentifications of other
rodents such as the coypu and muskrat.
Brown rats have acute hearing, are sensitive to ultrasound, and possess a very highly developed
olfactory sense. Their average heart rate is 300 to 400 beats per minute, with a respiratory rate of
around 100 per minute. The vision of a pigmented rat is poor, around 20/600, while a non-
pigmented (albino) with no melanin in its eyes has both around 20/1200 vision and a terrible
scattering of light within its vision. Brown rats are dichromates who perceive colours rather like
a human with red-green colorblindness, and their colour saturation may be quite faint. Their blue
perception, however, also has UV receptors, allowing them to see ultraviolet lights that some
species cannot.[9]
[edit] Biology and behavior

30. Brown rat skull
The brown rat is usually active at night and is a good swimmer, both on the surface and
underwater, but unlike the related Black Rat (Rattus rattus) they are poor climbers. Brown rats
dig well, and often excavate extensive burrow systems. A 2007 study found brown rats to
possess metacognition, a mental ability previously only found in humans and some primates,[10]
but further analysis suggested that they may have been following simple operant conditioning
principles.[11]
[edit] Communication
Brown rats are capable of producing ultrasonic vocalizations. As pups, young rats use different
types of ultrasonic cries to elicit and direct maternal search behavior,[12] as well as to regulate
their mother's movements in the nest.[13] Although pups will produce ultrasounds around any
other rats at 7 days old, by 14 days old they significantly reduce ultrasound production around
male rats as a defensive response.[14] Adult rats will emit ultrasonic vocalizations in response to
predators or perceived danger;[15] the frequency and duration of such cries depending on the sex
and reproductive status of the rat.[16][17] The female rat will also emit ultrasonic vocalizations
during mating.[18]
[edit] Chirping
Rats may also emit short, high frequency, ultrasonic, socially induced vocalization during rough
and tumble play, before receiving morphine, or mating, and when tickled. The vocalization is
described as a distinct "chirping", has been likened to laughter, and is interpreted as an
expectation of something rewarding.[19] Like most rat vocalizations, the "chirping" is too high in

31. pitch for humans to hear without special equipment. Bat detectors are often used by pet owners
for this purpose.
In clinical studies, the chirping is associated with positive emotional feelings, and social bonding
occurs with the tickler, resulting in the rats becoming conditioned to seek the tickling. However,
as the rats age, there appears to be a decline in the tendency to chirp.[20]
Rat chirp also can be utilized for mosquito control.[citation needed]
Other ultrasonic vocalisations, including a lower-frequency 'boom' or 'whoom' noise can be
produced by bucks in a calm state, when grooming or settling down to sleep.[citation needed]
[edit] Audible communication
Brown rats also produce communicative noises capable of being heard by humans. The most
commonly heard in domestic rats is bruxing, or tooth-grinding, which is most usually triggered
by happiness, but can also be 'self-comforting' in stressful situations, such as a visit to the vet.
The noise is best described as either a quick clicking or 'burring' sound, varying from animal to
animal.
In addition, they commonly squeak along a range of tones from high, abrupt pain squeaks to soft,
persistent 'singing' sounds during confrontations.
[edit] Diet
The brown rat is a true omnivore and will consume almost anything, but cereals form a
substantial part of its diet.
Brown rat eating sunflower seeds
Martin Schein, founder of the Animal Behavior Society in 1964, studied the diet of brown rats
and came to the conclusion that the most-liked foods of brown rats were (in order) scrambled
eggs, macaroni and cheese, and cooked corn kernels. According to Schein, the least-liked foods
were raw beets, peaches, and raw celery.[21]
Foraging behavior is often population-specific, and varies by environment and food source.[2]
Brown rats living near a hatchery in West Virginia catch fingerling fish.[22] Some colonies along
the banks of the Po river in Italy will dive for mollusks,[23][24] a practice demonstrating social

32. learning among members of this species.[25] Rats on the island of Norderoog in the North Sea
stalk and kill sparrows and ducks.[26]
[edit] Reproduction and life cycle
The brown rat can breed throughout the year if conditions are suitable, a female producing up to
five litters a year. The gestation period is only 21 days and litters can number up to fourteen,
although seven is common. They reach sexual maturity in about 5 weeks. The maximum life
span is up to three years, although most barely manage one. A yearly mortality rate of 95% is
estimated, with predators and interspecies conflict as major causes.
When lactating, female rats display a 24 hour rhythm of maternal behavior, and will usually
spend more time attending to smaller litters than large ones.[27]
Brown rats live in large hierarchical groups, either in burrows or subsurface places such as
sewers and cellars. When food is in short supply, the rats lower in social order are the first to die.
If a large fraction of a rat population is exterminated, the remaining rats will increase their
reproductive rate, and quickly restore the old population level.[citation needed]
[edit] Social behavior
It is common for rats to groom each other and sleep together.[28] As with dogs, rats create a social
hierarchy, and each rat has its own place in the pack. Rats are said to establish an order of
hierarchy and so one rat will be dominant over another one.[29] Groups of rats tend to "play
fight", which can involve any combination of jumping, chasing, tumbling, and boxing. Play
fighting involves rats going for each other's necks, while serious fighting involves strikes at the
others' back ends.[30]
[edit] Burrowing
Rats are known to burrow extensively, both in the wild and in captivity, if given access to a
suitable substrate.[31] Rats generally begin a new burrow adjacent to an object or structure, as this
provides a sturdy "roof" for the section of the burrow nearest to the ground's surface.[32] Burrows
usually develop to eventually include multiple levels of tunnels, as well as a secondary
entrance.[31] Older male rats will generally not burrow, while young males and females will
burrow vigorously.[31][33]
Burrows provide rats with shelter and food storage as well as safe, thermoregulated nest sites.[31]
Rats use their burrows to escape from perceived threats in the surrounding environment—for
example, rats will retreat to their burrows following a sudden, loud noise or while fleeing an
intruder.[34] Burrowing can therefore be described as a "pre-encounter defensive behavior", as
opposed to a "post-encounter defensive behavior", such as flight, freezing, or avoidance of a
threatening stimulus.
[edit] Distribution and habitat

33. Likely originating from the plains of Asia, Northern China and Mongolia, the brown rat spread
to other parts of the world sometime in the Middle Ages.[35][36][37] The question of when brown
rats became commensal with humans remains unsettled, but as a species they have spread and
established themselves along routes of human migration and now live almost everywhere
humans do.[38]
The brown rat may have been present in Europe as early as 1553, a conclusion drawn from an
illustration and description by Swiss naturalist Conrad Gesner in his book Historiae animalium,
published 1551-1558.[39] Though Gesner's description could apply to the black rat, his mention of
a large percentage of albino specimens—not uncommon among wild populations of brown
rats—adds credibility to this conclusion.[40] Reliable reports dating to the 18th century document
the presence of the brown rat in England in 1730, France in 1735, Germany in 1750, and Spain
in 1800,[40] becoming widespread during the Industrial Revolution.[41] It did not reach North
America until around 1750-1755.[39][42]
As it spread from Asia, the brown rat generally displaced the black rat in areas where humans
lived. In addition to being larger and more aggressive, the change from wooden structures and
thatched roofs to bricked and tiled buildings favored the burrowing brown rats over the arboreal
black rats. In addition, brown rats eat a wider variety of foods, and are more resistant to weather
extremes.[43]
In the absence of humans, brown rats prefer damp environments such as river banks.[41]
However, the great majority are now linked to man-made environments, such as sewage systems.
Brown rat in a flower box in the East Village of New York City.
It is often said that there are as many rats in cities as people, but this varies from area to area
depending on climate, living conditions, etc. Brown rats in cities tend not to wander extensively,
often staying within 20 m (66 ft) of their nest if a suitable concentrated food supply is available,
but they will range more widely where food availability is lower. In New York City there is great
debate over the size of the rat population with estimates from almost 100 million rats to as few as
250,000.[44] Experts suggest New York is a particularly attractive place for rats because of its
aging infrastructure, high moisture and poverty rates.[44] In addition to sewers, rats are very
comfortable living in alleyways and residential buildings, as there is usually a large and
continuous food source in those areas.[45]

34. In the United Kingdom some figures show that the rat population has been rising, with
estimations that 81 million rats reside in the UK.[46] Those figures would mean that there are 1.3
rats per person in the country. High rat populations in the UK are often attributed to the mild
climate, which allow them higher survival rates during the winter months.
The only brown rat-free zones in the world are the Arctic, the Antarctic, some especially isolated
islands, the province of Alberta in Canada,[47] and certain conservation areas in New
Zealand[48][49]
Antarctica is almost completely covered by ice and has no permanent human inhabitants, making
it uninhabitable by rats. The Arctic has extremely cold winters that rats cannot survive outdoors,
and the human population density is extremely low making it difficult for rats to travel from one
habitation to another. When the occasional rat infestation is noticed and eliminated, the rats are
unable to re-infest it from an adjacent one. Isolated islands are also able to eliminate rat
populations because of low human population density and geographic distance from other rat
populations.
[edit] Alaska
Rat Island in Alaska was infested with brown rats after a Japanese shipwreck in 1780. They had
a devastating effect on the native bird life. An eradication program was started in 2007 and the
island was declared rat free in June 2009.
[edit] Alberta, Canada
Alberta, Canada, is unusual in that rat infestation was eliminated by aggressive government
action. Although it is a major agricultural area, it is far from any seaport and only a portion of its
eastern boundary with Saskatchewan provides a favorable entry route for rats. They cannot
survive in the boreal forest to the north, the Rocky Mountains to the west, nor the semi-arid High
Plains of Montana to the south. The first brown rat did not reach Alberta until 1950, and in 1951
the province launched a rat-control program that included shooting and poisoning rats, and
bulldozing, burning down, and blowing up rat-infested buildings. The effort was backed by
legislation that required every person and every municipality to destroy and prevent the
establishment of designated pests. If they failed, the provincial government could carry out the
necessary measures and charge the costs to the landowner or municipality.[50]
In the first year of the program, 64 tonnes (71 short tons) of arsenic trioxide were spread
throughout 8,000 buildings on farms along the Saskatchewan border. In 1953 the much less toxic
and more effective poison, Warfarin, was introduced. By 1960 the number of rat infestations in
Alberta dropped to below 200 per year.[51]
Currently, only zoos, universities, and research institutes are allowed to own caged rats in
Alberta, and possession of an unlicensed rat (including pet rats) is punishable by a $5,000 fine or
60 days in jail. The adjacent and similarly landlocked province of Saskatchewan initiated a rat
control program in 1972, and has managed to reduce the number of rats in the province
substantially, although they have not been eliminated.[52]

35. [edit] New Zealand
First arriving before 1800 (perhaps on James Cook's vessels),[53] brown rats have posed a serious
threat to many of New Zealand's native animals. Rat eradication programmes within New
Zealand have led to rat-free zones on offshore islands and even on fenced "ecological islands" on
the mainland. Before an eradication effort was launched in 2001, the sub-Antarctic Campbell
Island had the highest population density of brown rats in the world.[54]
[edit] Diseases
Similar to other rodents, brown rats may carry a number of pathogens[55] which can result in
disease, including Weil's disease, rat bite fever, cryptosporidiosis, Viral hemorrhagic fever
(VHF), Q fever and hantavirus pulmonary syndrome. In the United Kingdom, brown rats are an
important reservoir for Coxiella burnetii, the bacteria that cause Q fever, with seroprevalence for
the bacteria found to be as high as 53% in some wild populations.[56]
This species can also serve as a reservoir for Toxoplasma gondii, the parasite that causes
toxoplasmosis, though the disease usually spreads from rats to humans when domestic cats feed
on infected brown rats.[57] The parasite has a long history with the brown rat, and there are
indications that the parasite has evolved to alter an infected rat's perception to cat predation,
making it more susceptible to predation and increasing the likelihood of transmission.[58]
Surveys and specimens of brown rat populations throughout the world have shown that this
species is often associated with outbreaks of trichinosis,[59][60] but the extent to which the brown
rat is responsible in transmitting Trichinella larvae to humans and other synanthropic animals is
at least somewhat debatable.[61] Trichinella pseudospiralis, a parasite previously not considered
to be a potential pathogen in humans or domestic animals, has been found to be pathogenic in
humans and carried by brown rats.[62]
Brown rats are sometimes mistakenly thought to be a major reservoir of bubonic plague, a
possible cause of The Black Death. However, the bacterium responsible, Yersinia pestis, is
commonly endemic in only a few rodent species and is usually transmitted zoonotically by rat
fleas—common carrier rodents today include ground squirrels and wood rats. However, brown
rats may suffer from plague, as can many non-rodent species including dogs, cats, and
humans.[63] The original carrier for the plague-infected fleas thought to be responsible for the
Black Death was the black rat, and it has been hypothesized that the displacement of black rats
by brown rats led to the decline of bubonic plague.[64] This theory has, however, been
deprecated, as the dates of these displacements do not match the increases and decreases in
plague outbreaks.[65]
[edit] In captivity
[edit] Uses in science
Main article: Laboratory rat

36. Selective breeding of albino brown rats rescued from being killed in a now-outlawed sport called
rat-baiting has produced the albino laboratory rat.[66] Like mice, these rats are frequently
subjects of medical, psychological and other biological experiments and constitute an important
model organism. This is because they grow quickly to sexual maturity and are easy to keep and
to breed in captivity. When modern biologists refer to "rats", they almost always mean Rattus
norvegicus.
[edit] As pets
Main article: Fancy rat
The brown rat is kept as a pet in many parts of the world. Australia, the United Kingdom, and the
United States are just a few of the countries that have formed fancy rat associations similar in
nature to the American Kennel Club, establishing standards, orchestrating events, and promoting
responsible pet ownership.
There are many different types of domesticated brown rats. These include variations in coat
patterns as well as the style of the coat, such as Hairless or Rex, and more recently developed
variations in body size and structure including dwarf and tailless fancy rats.
[edit] References
uestion: What is the life and life cycle of the flea, & why is flea control so
difficult?
Fleas. They make pets' lives miserable, and humans begin to itch just at the thought of them.
Vets are often asked what pill, drop, dip, collar, or shampoo works the best to get rid of these
persistent parasites. The answer is that there is no single method or insecticide that will
completely eradicate (or at least control) a flea problem. The flea life cycle is fairly complex, and
understanding the various stages will make it easier to get rid of them.
Answer: Collectively, all of the species of fleas are categorized under the order name of
Siphonaptera. The cat flea, Ctenocephalides felix, is the most commonly found flea in the US
and infests cats, dogs, humans, and other mammalian and avian hosts.
Fleas thrive in warm, moist environments and climates. The main flea food is blood from the
host animal. Host animals are many species - cats, dogs, humans, etc. Fleas primarily utilize
mammalian hosts (about 95%). Fleas can also infest avian species (about 5%). Flea saliva, like
other biting skin parasites, contains an ingredient that softens, or "digests" the host's skin for
easier penetration and feeding. The saliva of fleas is irritating and allergenic -- the cause of all
the itching, scratching, and other signs seen with Flea Allergy Dermatitis, or FAD.
Fleas have four main stages in their life cycle: egg, larva, pupa, and adult. The total flea life
cycle can range from a couple weeks to several months, depending on environmental conditions.

37. ADULT: The adult flea is very flat side to side. There are hair-like bristles on the flea body and
legs to aid in their navigation through pet hair. Fleas have 3 pairs of legs, the hindmost pair
designed for jumping. Fleas are well known for their jumping abilities.
Adult fleas prefer to live on the animal and their diet consists of blood meals courtesy of the host
animal. The female flea lays white, roundish eggs. The adult female flea can lay up to 50 eggs
per day1, 500-600 eggs2 over several months.
EGG: The eggs are not sticky (like some parasites), and they usually fall off of the animal into
the carpet, bedding, floorboards, and soil. When the flea egg hatches varies -- anywhere from
two days to a few weeks, depending on environmental conditions. The larva emerges from the
egg using a chitin tooth, a hard spine on the top of the head that disappears as the flea matures.
LARVA (plural = larvae): The larval stage actually has three developmental stages within this
stage. Larvae are about 1/4" (6.35 mm) long, and semi-transparent white. They have small hairs
along their body and actively move. They eat the feces of adult fleas (which is mostly dried
blood) and other organic debris found in the carpet, bedding, and soil. Depending on the amount
of food present and the environmental conditions, the larval stage lasts about 5 to 18 days (longer
in some cases) then the larva spins a silken cocoon and pupates.
PUPA (plural = pupae): The pupa is the last stage before adult. The adult flea can emerge from
the cocoon as early as 3 to 5 days, or it can stay in the cocoon for a year or more, waiting for the
right time to emerge. When is the right time? (Never, say pet lovers everywhere!) Stimuli such as
warm ambient temperatures, high humidity, even the vibrations and carbon dioxide emitted from
a passing animal will cause the flea to emerge from the cocoon faster. This brings us back to the
adult flea.
The entire life cycle is quite variable, as evidenced by the variability in each life stage
progression. As mentioned above, the cycle can be as short as two weeks or as long as two years.
That is why it is so important to remain vigilant, even when a flea problem is thought to be under
control!
Related Reading:
he Life Cycle of Fleas
By Cat Carson, eHow Contributor
Print this article

38. The Life Cycle of Fleas
A flea is a parasite that goes through four primary stages in its life cycle: egg, larva, pupa and
adult. The entire flea life cycle ranges from two weeks to eight months depending on
environmental factors such as temperature, food sources and humidity.
Related Searches:
Fleas Bites
Treat Fleas
1. Egg
o An adult female flea begins laying eggs about two days after mating. These eggs
are loosely laid on a host, and usually fall off into the environment where they
hatch in about two to three days.
Larva
o A flea goes through three larval phases that last one week to several months. Flea
larvae feed on adult flea feces, hair, feathers, dead skin and other organic debris.
Pupa
o Flea pupae mature to adulthood inside of a cocoon they weave in their larval
phase. Pupa live in the cocoon for five days to two weeks.
Adult
o Adult fleas emerge from their cocoons when they sense warmth, carbon dioxide,
motion and vibrations, all of which tell it that an animal host is nearby. Adult
fleas must find a blood meal within their first 30 days of life in order to survi

39. Read more: The Life Cycle of Fleas | eHow.com http://www.ehow.com/facts_5188387_life-cycle-
fleas.html#ixzz4SHhCspz0
Life Cycle of Lice
By an eHow Contributor
Print this article
Head lice are insects that feed off the of the blood of their host. One louse can produce hundreds
of eggs during its lifespan. Head lice live for nearly two months and have three stages of life.
Related Searches:
Lice Pictures
Lice Comb
1. Nits
o A head lice egg is called a nit. Nits are laid by female lice at the base of the hair
shaft. Once laid, nits take five to 10 days to hatch. Eggs, which are about the size
of sesame seeds, are yellowish-brown to white in color.
Nymphs
o When the nits hatch, they release nymphs. Nymphs look like adult lice, but are
smaller in size. Nymphs molt (outgrow their exoskeleton) three times before
becoming an adult. The nymph stage lasts up to seven days.
Adults
o The adult is the third stage of head lice. Adults can live up to 30 days and feed off
the host up to five times a day. Adult females will lay up to a dozen eggs a day.
Hosts Needed
o Adults and nymphs can live only two or three days without a host. Nits can
survive up to two weeks without a host.
Transmission

40. o Head lice are often transmitted from host to host via objects that come in contact
with hair. Head lice can go two or three days without feeding and can live on
detached hair strands, clothing, hats, combs, towels and bedding.
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Read more: Life Cycle of Lice | eHow.com http://www.ehow.com/facts_5137724_life-cycle-
lice.html#ixzz4SHfXzh4V
allery Index: Lice - Lice Pictures
Lice Life Cycle - Lice Pictures
Lice Pictures
Updated October 20, 2010
About.com Health's Disease and Condition content is reviewed by the Medical Review Board
Having a hard time figuring out what you are looking for when you think your kids have lice? This picture
of the 3 stages of the head lice life cycle can help.
11 of 11
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41. Sponsored Link
Embroidery LibraryThe best designs, the best prices! 70,000+ designs, all
downloadable.www.emblibrary.com
Head Lice Life Cycle Stages
Photo courtesy of the Centers for Disease Control and Prevention
This picture shows the three stages of the head lice life cycle, including the head lice egg or nit,
nymph, and adult louse, as compared to the size of a penny for scale.
Lice Life Cycle
A mature or adult head louse can lay up to 10 eggs or nits each day.
These nits, or lice eggs, hatch in about 7 to 12 days. Baby lice or nymphs are about the size of a
pinhead when they hatch, and quickly mature into adult lice in about a 9 to 12 days.
In just a few days, adult lice are ready mate, starting this lice life cycle all over again during their
3 to 4 week lifespan.
Of course, a proper lice treatment regimen can interrupt the lice life cycle and help you get rid of
the lice on your child's hair.
Sources:
American Academy of Pediatrics Clinical Report. Head Lice. PEDIATRICS Vol. 126 No. 2 August 2010, pp. 392-403.
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42. Readers Respond:

44. Ascaris Lumbricoides
Ascaris lumbricoides , common saying “round worm of man”, is the largest of the
intestinal nematodes parasitizing humans. It is the most common worm found in
human. It is worldwide in distribution and most prevalent through out the tropics,
sub-tropics and more prevalent in the countryside than in the city.
I. Morphology

45. 1. Adult: The adults are cylindrical in shape, creamy-white and pinkish in color. The
female averages 20~35cm in length, the largest 49cm. The male is smaller, averaging
15~31cm in length and distinctly more slender than the female. The typical curled
tail with a pair sickle like copulatory spine readily distinguishes males. On the tip of
the head there are three lips, arranged as a Chinese word “ 品 ”. They have a
complete digestive tract. Reproductive organs are tubular. male has a single
reproductive tubule. The female has two reproductive tubules and the vulva is
ventrally located at the posterior part of the anterior 1/3 of the body.
2. Egg: There are three kind of the eggs. They are fertilized eggs, unfertilized eggs
and decorticated eggs. We usually describe a egg in 5 aspects: size, color, shape,
shell and content.
Fertilized eggs: broad oval in shape, brown in color, an average size 60 x45µm . The
shell is thicker and consists of ascaroside, chitinous layer, fertilizing membrane and
mammillated albuminous coat. The content is a fertilized ovum. There is a new-
moon shaped space at the each end inside the shell.
Unfertilized egg: Longer and slender than a fertilized egg. The chitinous layer and
albuminous coat are thinner than those of the fertilized eggs without ascaroside and
fertilizing membrane. The content is made of many refractable granules various in
size.
Decorticated eggs: Both fertilized and unfertilized eggs sometimes may lack their
outer albuminous coats and are colorless.
II. Life Cycle

46. 1. Site of inhabitation: small intestine
2. Infetive stage: embryonated eggs
3. Route of infection: by mouth
4. No intermediate and reservoir hosts
5. Life span of the adult: about 1 year
III. Diagnosis
The symptoms and signs are for reference only. The confirmative diagnosis
depends on the recovery and identification of the worm or its egg.
1. Ascaris pneumonitis: Examination of sputum for Ascaris larvae is sometimes
successful.
2. Intestinal ascariasis: Feces are examined for the ascaris eggs.
(1) Direct fecal film: It is simple and effective. The eggs are easily found using this
way due to a large number of the female oviposition, approximately 240,000 eggs
per worm per day. So this method is the first choice.
(2) Brine-floatation method:
(3) Recovery of adult worms: When adults or adolescents are found in feces or vomit
and tissues and organs from the human infected with ascarids , the diagnosis may be
defined.
IV. Requirements
1. Study the morphological characters of ova and adult worms of Ascaris.

47. 2. Realize the life cycle of the worm.
3. Master the methods of the diagnosis.
V. Individual observation
Fertilized eggs and unfertilized eggs
VI. work
Draw a fertilized and unfertilized Ascaris egg.
Trichuris trichiura ( Whipworm )
I. Morphology:
Adult: The worm looks like a buggy whip, the anterior 3/5 is slender and the
posterior 2/5 is thick. It is pinkish gray in color.
The female worm is 3-5 cm in length and has a long slender esophageal region. The
male is smaller than the female and has a curved tail.
Egg: It is barrel or spindle in shape and 50 x 20µm µm in size. It is brownish and has
a translucent polar plug at either ends. The content of the egg is an undeveloped
cell.
II. Life Cycle:
1. Site of inhabitation: cecum
2. Infective stage: embryonic egg

48. 3. Infectve mode and route: passively swallowed by the mouth
III.. Diagnosis:
Discover the eggs in feces by floatation method or direct fecal smear.
IV.Requirements
1.Study the morphological characters of ova and adult worms of T. trichiura.
2.Realize the life cycle of the worm.
3.Master the methods of the diagnosis.
V. Individual observation
The eggs and the adults
VI.work
[Last Modified: 07/20/2009
07:14:39]
[Ancylostoma braziliense] [Ancylostoma caninum] [Ancylostoma duodenale] [Necator
americanus]
Causal Agents:
The human hookworms include the nematode species, Ancylostoma duodenale and Necator americanus. A larger
group of hookworms infecting animals can invade and parasitize humans (A. ceylanicum) or can penetrate the
human skin (causing cutaneous larva migrans), but do not develop any further (A. braziliense, A. caninum,
Uncinaria stenocephala). Occasionally A. caninum larvae may migrate to the human intestine, causing eosinophilic
enteritis. Ancylostoma caninum larvae have also been implicated as a cause of diffuse unilateral subacute
neuroretinitis.
Life Cycle (intestinal hookworm infection):

49. Eggs are passed in the stool , and under favorable conditions (moisture, warmth, shade),
larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the
soil , and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae
that are infective . These infective larvae can survive 3 to 4 weeks in favorable
environmental conditions. On contact with the human host, the larvae penetrate the skin
and are carried through the blood vessels to the heart and then to the lungs. They
penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are
swallowed . The larvae reach the small intestine, where they reside and mature into
adults. Adult worms live in the lumen of the small intestine, where they attach to the
intestinal wall with resultant blood loss by the host . Most adult worms are eliminated in
1 to 2 years, but the longevity may reach several years.
Some A. duodenale larvae, following penetration of the host skin, can become dormant (in
the intestine or muscle). In addition, infection by A. duodenale may probably also occur by
the oral and transmammary route. N. americanus, however, requires a transpulmonary
migration phase.
Life Cycle (cutaneous larval migrans):

50. Cutaneous larval migrans (also known as creeping eruption) is a zoonotic infection with hookworm species that do
not use humans as a definitive host, the most common being A. braziliense and A. caninum. The normal
definitive hosts for these species are dogs and cats. The cycle in the definitive host is very
similar to the cycle for the human species. Eggs are passed in the stool , and under
favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released
rhabditiform larvae grow in the feces and/or the soil , and after 5 to 10 days (and two
molts) they become filariform (third-stage) larvae that are infective . These infective
larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the
animal host , the larvae penetrate the skin and are carried through the blood vessels to
the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the
bronchial tree to the pharynx, and are swallowed. The larvae reach the small intestine,
where they reside and mature into adults. Adult worms live in the lumen of the small
intestine, where they attach to the intestinal wall. Some larvae become arrested in the
tissues, and serve as source of infection for pups via transmammary (and possibly
transplacental) routes . Humans may also become infected when filariform larvae penetrate the
skin . With most species, the larvae cannot mature further in the human host, and migrate aimlessly within the
epidermis, sometimes as much as several centimeters a day. Some larvae may persist in deeper tissue after finishing
their skin migration.
Geographic Distribution:
Hookworm is the second most common human helminthic infection (after ascariasis).
Hookworm species are worldwide in distribution, mostly in areas with moist, warm climate.
Both N. americanus and A. duodenale are found in Africa, Asia and the Americas. Necator

51. americanus predominates in the Americas and Australia, while only A. duodenale is found in
the Middle East, North Africa and southern Europe.
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Life cycle
Hookworm life cycle
See the image for the biological life cycle of the hookworms where it thrives in warm earth
where temperatures are over 18°C. They exist primarily in sandy or loamy soil and cannot live in
clay or muck. Rainfall averages must be more than 1000 mm (40 inches) a year. Only if these
conditions exist can the eggs hatch. Infective larvae of Necator americanus can survive at higher
temperatures, whereas those of Ancylostoma duodenale are better adapted to cooler climates.
Generally, they live for only a few weeks at most under natural conditions, and die almost
immediately on exposure to direct sunlight or desiccation.
Infection of the host is by the larvae, not the eggs. While A. duodenale can be ingested, the usual
method of infection is through the skin; this is commonly caused by walking barefoot through
areas contaminated with fecal matter. The larvae are able to penetrate the skin of the foot, and
once inside the body, they migrate through the vascular system to the lungs, and from there up
the trachea, and are swallowed. They then pass down the esophagus and enter the digestive
system, finishing their journey in the intestine, where the larvae mature into adult worms.[4][5]
Once in the host gut, Necator tends to cause a prolonged infection, generally 1–5 years (many
die within a year or two of infecting), though some adult worms have been recorded to live for
15 years or more. On the other hand, Ancylostoma adults are short lived, surviving on average
for only about 6 months. However, infection can be prolonged because dormant larvae can be
"recruited" sequentially from tissue "stores" (see Pathology, above) over many years, to replace
expired adult worms. This can give rise to seasonal fluctuations in infection prevalence and
intensity (apart from normal seasonal variations in transmission).

52. Civilian Public Service workers built and installed 2065 outhouses for hookworm eradication in
Mississippi and Florida from 1943 to 1947.
They mate inside the host, females laying up to 30,000 eggs per day and some 18 to 54 million
eggs during their lifetime, which pass out in feces. Because it takes 5–7 weeks for adult worms
to mature, mate and produce eggs, in the early stages of very heavy infection, acute symptoms
might occur without any eggs being detected in the patient's feces. This can make diagnosis very
difficult.
Summary of Biological Life Cycle
N. americanus and A. duodenale eggs can be found in warm, moist soil where they will
eventually hatch into first stage larvae, or L1. L1, the feeding non-infective rhabditoform stage,
will feed on soil microbes and eventually molt into second stage larvae, L2. L2, which is also in
the rhabditoform stage, will feed for approximately 7 days and then molt into the third stage
larvae, or L3. L3 is the filariform stage of the parasite, that is, the non-feeding infective form of
the larvae. The L3 larvae are extremely motile and will seek higher ground to increase their
chances of penetrating the skin of a human host. The L3 larvae can survive up to 2 weeks
without finding a host. While N. americanus larvae only infect through penetration of skin, A.
duodenale can infect both through penetration as well as orally. After the L3 larvae have
successfully entered the host, the larvae then travel through the subcutaneous venules and
lymphatic vessels of the human host. Eventually, the L3 larvae enter the lungs through the
pulmonary capillaries and break out into the alveoli. They will then travel up the trachea to be
coughed and swallowed by the host. After being swallowed, the L3 larvae are then found in the
small intestine where they molt into the L4, or adult worm stage. The entire process from skin
penetration to adult development takes about 5–9 weeks. The female adult worms will release
eggs (N. Americanus about 9,000-10,000 eggs/day and A. duodenale 25,000-30,000 eggs/day)
which are passed in the feces of the human host. These eggs will hatch in the environment within
several days and the cycle with start anew.[3][4][6]

53. Incubation Period
The incubation period can vary between a few weeks to many months and is largely dependent
on the number of Hookworm parasites an individual is infected with.[7]