Public health

9.1. Disease and Water
• What is pathogenic?
– refers to the ability of an organism to cause disease.

This direct and indirect action of pathogens
allows water-related diseases.

Water-borne Water-washed Water-based Water-related
diseases diseases diseases diseases

I- Water-borne diseases

• Water-borne diseases are any ilness cause by drinking water
contaminated by human or animal faeces, which contain
pathogenic microorganisms.

• The classical water-borne diseases are mainly low-infective dose
infections, such as cholera, typhoid, and leptospirosis.

• All the remaining diseases are high-infective dose infections and
include infectious hepatitis and bacillary dysentery.

Clinical Syndromes

Type I
• Noninﬂammatory
(enterotoxin, etc.)
• Proximal small bowel
• Watery diarrhea
Giardia lamblia
• Examples:
– Rotavirus
– Vibrio cholerae
– Giardia lamblia
– Cryptosporidium parvum
– Cyclopsora cayetanensis
Cholera toxin


Type II
Clinical Syndromes

• Inﬂammatory (invasive, cytotoxin)
• Colon
• Dysentery (bloody diarrhea)
• Examples:
– Salmonella enteriditis
– Clostridium difﬁcile
– Campylobacter pylori Enatmeba histolytica
– Enatmeba histolytica

Clinical Syndromes

Type III
• Penetrating
• Distal small bowel
• Examples:
– Salmonella typhi
– Yersinia enterococolithica
Salmonella typhi

II- Water-washed diseases

• Caused by a lack of personal hygiene because of water scarcity.

• These are diseases of mainly tropical areas and include infections
of the intestinal tract, the skin, and the eyes.

• The intestinal infections are all faecal in origin and include all the
water-borne diseases that are contracted because of poor
personal hygiene.


• The germs in the faeces can
cause the diseases by even
Transmission

slight contact and transfer.

• This contamination may
occur due to
floodwaters, water runoff
from landfills, septic
fields, and sewer pipes. Faecal-oral routes of
diseases transmission.

Transmission

• The only way to break the continued transmission is to
improve the people’s hygienic behaviour and to provide
them with certain basic needs:
– drinking water,
– washing and bathing facilities and
– sanitation.


• Most of the intestinal infections are diarrhoeal diseases
responsible for the high mortality rates among infants in the
developing world.

• The infections of the skin and mucous membranes are
non-faecal in origin and include bacterial skin
sepsis, scabies, and cutaneous fungal infections (such as
ringworm).
• Diseases spread by ﬂeas, ticks, and lice are
also included in this category, such as
epidemic typhus, rickettsial typhus, and
louse-borne fever.

III- Water-based diseases

• Water-based diseases are caused by pathogens that have a
complex life-cycle and which require an intermediate aquatic
host.

• All these diseases are caused by parasitic worms with the
severity of the infection depending on the number of worms
infecting the host.


• The two commonest water-based diseases are Schistosomias is
carried by the trematode Schistosoma spp. and Guine a worm
which is the nematode Dracunculus medimensis.

• Schistosoma worms use aquatic snails
as intermediate hosts and are
estimated as infecting as many as 200
million people, and the Guine a worm
uses the small crustacean Cyclops spp.
as its intermediate host.
Guine worm


Human Schistosomiasis

IV- Water-related diseases

• Caused by pathogens carried by insects that act as mechanical
vectors and which live near water.
• All these diseases are very severe and control of the insect
vectors is extremely diﬃcult.

• The most important water-related diseases include two viral
diseases,
– yellow fever, transmitted by the mosquito Aedes spp.
– dengue, which is carried by the mosquito Aedes aegypti which breeds in
water.

9.2. Water-borne diseases

• Industrial waste waters rarely contain pathogens, whereas
pathogens are common in food processing wastes.

• The pathogens found are directly related to the original plant or
animal materials being processed.

• In sewage, it is the diseases excreted by
man via faeces and urine that are of
primary importance to public health.

9.2. Water-borne diseases

• Pathogens in sewage are able to infect man and animals by oral
ingestion, via the skin or by respiratory routes.
• The commonest infection route for pathogens is oral ingestion,
which generally causes gastro-enteric disorders.

Water-borne diseases
-9.2.2. Bacteria -
Salmonellosis
• Gram-negative, rod-shaped and facultative
anaerobe in the family Enterobacteriaceae.

• Primary sources of salmonellae are intestinal
tracts of animals (domestic and wild) and
humans; shed in feces.
– Feces can contaminate soil and water (irrigation and processing)
– Salmonellae can survive in some soils for months to years; in water for
weeks to months

- 9.2.2. Bacteria -
Salmonellosis
• Some serotypes are largely specific to a single host, and these
include the typhoid organism
– S. typhi, specific to man;
– S. dublin, specific for cattle;
– S. abortus-ovis, specific for sheep; and
– S. cholerae-suis, specific for pigs.

• Other serotypes are not host-specific, for example,
– S. typhimurium which can infect a wide range of animals, including man.

- 9.2.2. Bacteria -
Salmonellosis
• The pathogen produces an endotoxin causing the typical
symptoms of salmonellosis such as
– acute gastro-enteritis with diarrhoea, and is often associated with
– abdominal cramps,
– fever,
– nausea,
– vomiting,
– headache, and
– in severe cases, even collapse and possible death.
• In pregnant animals, abortion may occur.

- 9.2.2. Bacteria -
Salmonellosis

- 9.2.2. Bacteria -
Salmonellosis
• Incubation period: 1-3d
• Signs and symptoms: diarrhea, fever, cramps, vomiting, s. typhi and
paratyphi cause chills, myalgia, headache, with rare diarrhea
• Duration: 4-7d
• Food Source: eggs, poultry, unpasteurized milk or juice, raw fruits
and vegetables, street venders, fecal water contamination
• Lab testing: stool cultures
• Treatment: ciprofloxacin or TMP-SMX. Antibiotics for severe cases
only

Necessitates typhoid immunization for travelers

- 9.2.2. Bacteria -
Campylobacter
• Gram-negative
• spirally shaped
• ﬂagellated
• oxidase-positive,
• reduce nitrates
• unable to produce acid in the presence of carbohydrates
• isolated from both fresh and estuarine waters
• causes acute gastro-enteritis (i.e. fever, nausea, adominal
pains, diarrhoea and vomiting)

- 9.2.2. Bacteria -
Campylobacter
• Water is either contaminated
directly by sewage which is rich in
Campylobacter or indirectly from
animal faeces.

• Household pets, farm animals and
birds are all known to be carriers of
the disease.

- 9.2.2. Bacteria -
Campylobacter
• Signs and symptoms: bloody or watery diarrhea, cramps, fever
• Duration: 2-10d
• Food Source : Poultry, milk, water
• Lab testing: special stool culture
• Treatment: erythromycin or ciprofloxacin-antibiotic for severe
cases only

- 9.2.2. Bacteria -
Shigellosis
• Gram-negative
• non-motile
• rods shaped
• oxidase-negative
• Shigella causes bacterial dysentery or
shigellosis
• Shigellosis is a problem of both developed and developing
countries with the Eastern Mediterranean countries
considered as an endemic region for the disease.

- 9.2.2. Bacteria -
Shigellosis
• When the disease is present as an epidemic, it appears to be
spread mainly by person to person contact, especially between
children, shigellosis being a typical institutional disease
occurring in over-crowded conditions.

• It may also be carried asymptomatically in the intestinal tract.

- 9.2.2. Bacteria -
Leptospirosis
• A potentially serious illness that can affect many parts of the
body

• Caused by Leptospira interrogans, a corkscrew-shaped
bacterium (spirochete)

• Leptospirosis-causing bacteria are common
worldwide, especially in tropical countries with heavy rainfall.

- 9.2.2. Bacteria -
Leptospirosis

Infected rodents and other wild and domestic
animals pass the bacteria in their urine.

The bacteria can live for a long time in fresh water, damp
soil, vegetation, and mud.
Flooding after heavy rainfall helps
spread the bacteria in the
environment.

- 9.2.2. Bacteria -
Leptospirosis
• People get leptospirosis by contact with fresh water, damp
soil, or vegetation contaminated by the urine of infected
animals.

• People who canoe, raft, wade, or swim in contaminated
lakes, rivers, and streams can get leptospirosis.

• Symptoms include fever, headache, chills, nausea and
vomiting, eye inflammation, and muscle aches.

- 9.2.2. Bacteria -
Leptospirosis
• In more severe cases, the illness
can result in liver damage and
jaundice (yellowing of the skin
and whites of the eyes), kidney
failure, and internal bleeding.

• People who are seriously ill with leptospirosis often need to be
hospitalized.

- 9.2.2. Bacteria -
Leptospirosis
• Symptoms usually begin about 10 days after infection.
• Diagnosed by a special blood test.
• Leptospirosis is treatable with antibiotics.

- 9.2.2. Bacteria -
Escherichia coli
• Gram-negative,
• non-sporulating
• rod-shaped bacterium
• either nonmotile or motile
• commonly found in the lower intestine
of warm-blooded organisms (endotherms).
• A number of strains of E.coli are pathogenic and cause
characteristic gastro-enteritis.

- 9.2.2. Bacteria -
Escherichia coli
• Pathogenic E.coli are classiﬁed into four main groups based on
– virulence properties,
– clinical syndrome,
– epidemiology,
– O:H serogrouping.
• causes of many common bacterial
infections, including cholecystitis, bacteremia, cholangitis, urin
ary tract infection (UTI), and traveler's diarrhea, and other
clinical infections such as neonatal meningitis and
pneumonia..

- 9.2.2. Bacteria -
Escherichia coli
• Most E. coli infections come from:
– Eating undercooked ground beef (the inside is pink)
– Drinking contaminated (impure) water
– Drinking unpasteurized (raw) milk
– Working with cattle

- 9.2.2. Bacteria -
Escherichia coli
• Signs and symptoms: watery diarrhea, vomiting, cramps
• Duration: 3-10d
• Food Source: fecal contamination of food
• Lab testing: specific stool culture
• Treatment: ciprofloxacin-antibiotic for severe cases only or
TMP-SMX

- 9.2.2. Bacteria -
Cholera
• Cholera is an infection of the small
intestine that causes a large amount
of watery diarrhea.

• Cholera is caused by the
bacterium Vibrio cholerae.

• The bacteria releases a toxin that causes increased release of
water in the intestines, which produces severe diarrhea.

- 9.2.2. Bacteria -
Cholera
• Cholera occurs in places with poor
sanitation, crowding, war, and famine. Common locations for
cholera include:
– Africa
– Asia
– India
– Mexico
– South and
Central America
– The Mediterranean

- 9.2.2. Bacteria -
Cholera

- 9.2.2. Bacteria -
Cholera
• Upto106–107 organisms are required to cause the illness, so
cholera is not normally spread by person-to-person contact.

• It is readily transmitted by drinking contaminated water either
by eating food handled by a carrier or which has been washed
with contaminated water.

- 9.2.2. Bacteria -
Cholera
• An infected person or symptom less carrier of the disease
excretes up to 1013 bacteria daily, enough to theoretically infect
107 people!

• It is an intestinal disease with characteristic symptoms, that is
sudden diarrhoea with copious watery
faeces, vomiting, suppression of urine, rapid
dehydration, lowered temperature and blood pressure, and
complete collapse.

- 9.2.2. Bacteria -
Cholera
• Without therapy the disease has a 60% mortality rate, the
patient dying within a few hours of ﬁrst showing the
symptoms, although with suitable treatment the mortality rate
can be reduced to less than one percent.

- 9.2.2. Bacteria -
Cholera
• Incubation period: 24-72h
• Signs and symptoms: severe watery diarrhea and vomiting
• Duration: 3-7d death from dehydration
• Food Source: contaminated water, fish, shellfish, street
vendors
• Lab testing: specific stool cultures
• Treatment: ciprofloxacin in adults, TMP-SMX in children

- 9.2.2. Bacteria -
Tularemia
• Tularemia is a serious infectious disease caused by the
bacterium Francisella tularensis.

• A Gram-negative, nonmotile coccobacillus, the bacterium has
several subspecies with varying degrees of virulence.

• F. tularensis can infect many animals, especially small rodents,
rabbits and hares.

- 9.2.2. Bacteria -
Tularemia
• Tularemia infections occur
throughout the Northern
Hemisphere.

• There are two types of the
bacterium, both of which can
infect humans.
A tularemia lesion on the dorsal skin
Type A Type B of right hand.
tularemia tularemia

- 9.2.2. Bacteria -
Tularemia
• Type A infects animals and ticks in North America. Infection is
often sporadic and severe and can be fatal in humans. Type A
infections have not been described as occurring naturally
outside North America.

• Type B occurs in animals throughout the northern hemisphere
including North America, causes milder symptoms than type
A, and does not cause fatal infections. Large outbreaks have
occurred.

- 9.2.2. Bacteria -
Tularemia
• Person to person transmission of F.
tularensis has never been documented.
Infection may occur by:
– Bite of an insect, e.g. tick or
mosquito, which has fed on an infected
– animal.
Direct contact with the tissues/secretions of infected animals.
– Inhaling or ingesting bacteria.
– Contact with or consumption of contaminated food or water.

- 9.2.2. Bacteria -
Tularemia
• Symptoms:
– Chills, Fever, Headache, Joint stiffness, Muscle pains, Possible
conjunctivitis, Red spot on the skin, enlarging to a sore (ulcer),
Shortness of breath, Sweating, Weight loss
• Exams and Tests:
– Blood culture for tularemia, Blood test measuring the body's immune
response to the infection (serology for tularemia), Chest x-ray,
Polymerase chain reaction (PCR) test of a sample from an ulcer
• Treatment:
– Streptomycin, tetracycline, gentamycin..

- 9.2.2. Bacteria -
Mycobacteria
• Tuberculosis or TB is a common and often deadly infectious
diease caused by mycobacteria, usually Mycobacterium
tuberculosis in humans.

• Tuberculosis usually attacks the lungs but can also affect other
parts of the body.

• The classic symtoms are a chronic cough with blood-tinged
sputum, fever, night sweats, and weight loss.

- 9.2.2. Bacteria -
Mycobacteria
• The primary cause of TB, Mycobacterium tuberculosis, is a
small aerobic non-motile bacillus.

• The M. tuberculosis complex includes four other TB causing
mycobacteria:
– M. bovis, M. africanum, M. canetti and M. microti.

• M. africanum is not widespread, but in parts of Africa it is a
significant cause of tuberculosis.

- 9.2.2. Bacteria -
Mycobacteria
• M.tuberculosis is frequently isolated in wastewater from
hospitals and meat-processing plants.

• Like Leptospira, the bacilli are able to survive for several weeks
at low temperatures in water contaminated with organic
matter.

• Clearly, drinking contaminated water must be a source of
infection.

- 9.2.2. Bacteria -
Mycobacteria

Lepromatous Leprosy (Early/Late Stages)

- 9.2.2. Bacteria -
Brucellosis
• Caused by various Brucella
species, which mainly infect
cattle, swine, goats, sheep and dogs.

• Humans generally acquire the disease
through direct contact with infected
animals, by eating or drinking
contaminated animal products, or by
inhaling airborne agents.

- 9.2.2. Bacteria -
Brucellosis
• The majority of cases are caused by ingesting unpasteurized
milk or cheese from infected goats or sheep.

• Person-to-person transmission is rare.

• The disease causes flu-like symptoms, including
fever, weakness, malaise and weight loss.

- 9.2.2. Bacteria -
Brucellosis

Swollen “knee” joint of caribou due
to brucellosis.

- 9.2.2. Bacteria -
Brucellosis
• Signs and symptoms:
fever, chills, headache, myalgias, arthralgias, bloody diarrhea
• Duration : weeks
• Food Source: raw milk, goat cheese, meats
• Lab testing: blood, serology
• Treatment: rifampin and doxycycline

- 9.2.2. Bacteria -
Aeromonads
• Ubiquitous oxidase-positive,
• glucose-fermenting,
• motile,
• not curved gram-negative rods
• widely distributed in fresh and
salt water environments Aeromonas hydrophila adhering to
• Isolated from produce and human epithelial cells.
meat sources

- 9.2.2. Bacteria -
Aeromonads
• Aeromonas gastroenteritis usually results from consumption of
contaminated seafood, especially raw oysters or clams;

• illness usually self-limiting, except in very young and old
populations.

• Wound infections usually from
Aeromonas hydrophilia resulting
from traumatic water-related
wound.

Human leg infected with
Aeromonas hydrophila

- 9.2.2. Bacteria -
Helicobacter pylori
• Gram-negative
• Spiral-shaped
• Flagellated
• Microaerophilic
• Colonize the gastric
epithelium of humans.

- 9.2.2. Bacteria -
Helicobacter pylori
• causing
– peptic ulcers,
– chronic type B gastro-enteritis,
– and as a risk factor for gastric cancer
– gastric lymphoma
– coronary heart disease

- 9.2.2. Bacteria -
Helicobacter pylori
• isolated in a wide range of natural waters as well as drinking
water and wastewater using PCR.
• can be transferred via drinking water and food.
• its natural niche is the human stomach,
• needs to survive in the natural environment in order to be a
life-long infection.
• nothing is known of its survival or ecology in the natural
environment

-9.2.3. Viruses -

• There are over 140 distinct known types of human pathogenic
viruses.
• Of most concern are those which cause gastrointestinal illness
known as the enteric viruses which includes ;
» enteroviruses,
» rotaviruses,
» astroviruses,
» calciviruses,
» hepatitis A virus,
» Norwalk virus and
» other ‘small round’ viruses

- 9.2.3. Viruses -

Common waterborne enteric viruses and
the disease they cause (Bitton 1994)

- 9.2.3. Viruses -

• Human viruses present in sewage are almost entirely derived
from faecal matter.

• Viral contamination arises when
sewage containing pathogenic
viruses contaminates surface
and ground waters which are
subsequently used as sources of
drinking waters (West 1991).

- 9.2.3. Viruses -
• Large outbreaks of viral disease
occur when massive sewage
contamination takes place
overwhelming existing water
treatment mechanisms.

• Infectious hepatitis, entroviruses, reovirus and adenovirus are
all thought to be transmitted via water.

- 9.2.3. Viruses -

• Of most concern in Europe is viral hepatitis.

• There are three subgroups:
– Hepatitis A Virus (HAV) which is transmitted by water;
– Hepatitis B which is spread by infected blood or sexual contact is
endemic in certain countries such as Greece
– Hepatitis C which is a non- A or B type hepatitis virus

- 9.2.3. Viruses -
• Hepatitis A is a 27 nm RNA entrovirus
that is spread by faecal contamination of
food, drinking water, and areas that are
used for bathing and swimming (Jehl-
Pietri 1992).
• There is no treatment for hepatitis
A, with the only eﬀective protection good
personal hygiene, and the proper
protection and treatment of drinking
water.

- 9.2.3. Viruses -

• Hepatitis A virus accounts for 87% of all viral water borne
disease outbreaks in the USA (Craun 1986).

• In June 1979, a large water borne outbreak of gastroenteritis
and hepatitis occurred in Georgetown, Texas, aﬀecting
approximately 79% of individuals supplied by the
contaminated water following a period of heavy rain fall that
washed sewage into the ground water supply.

- 9.2.3. Viruses -

• The best documented outbreak of water borne viral disease
occurred in New Delhi, India in 1955/56, when 35,000 cases of
infectious hepatitis were reported following gross
contamination of the water supply by sewage (Dennis 1959).

• Brugha et al. (1998) reported that those who are regularly
exposed to sewage have a signiﬁcant risk factor for HAV
infection and should be vaccinated.

- 9.2.3. Viruses -

• Warm-blooded animals appear able to carry viruses
pathogenic to man.

• For example, 10% of beagles have been shown to carry human
enteric viruses; therefore, there appears a danger of infection
from waters not contaminated by sewage but by other sources
of pollution, especially storm water from paved areas.

- 9.2.3. Viruses -

• Most viruses are able to remain viable for several weeks in
water at low temperatures, so long as there is some organic
matter present.

• Viruses are found in both surface and groundwater sources.

• Two viruses which have caused recent outbreaks of illness due
to drinking water contamination are Norwalk virus and
rotavirus

- 9.2.3. Viruses -

• Norwalk virus results in severe diarrhoea and vomiting. It is of
particular worry to the water industry in that it appears not to
be aﬀected by normal chlorination levels.

• Also it seems that infection by the virus only gives rise to
short-term immunity, while lifelong immunity is conferred by
most other enteric viruses.

- 9.2.3. Viruses -

Examples of waterborne outbreaks due to the Norwalk virus
(Bitton 1994).

The largest of these outbreaks occurred in Rome, Georgia
(USA) in 1980, when contaminated water from a textile
factory came into contact with a community water supply.

- 9.2.3. Viruses -
• Rotavirus is a major contributor to child
diarrhoea syndrome.
• This causes the death of some six
million children in developing countries
each year.
• Outbreaks do occur occasionally in
hospitals, and although associated with
child diarrhoea, can be much more
serious if contracted by an adult.

- 9.2.3. Viruses -

• A large outbreak of gastro-enteritis aﬀecting 900 people due
to contamination of a water supply by sewage containing
rotaviruses was reported in Arizona in 1991.

• Other major outbreaks include 11,600 infected in East
Germany in 1981–1982 when ﬂood water contaminated
wells, and a year later in China when 13,311 were infected
with rotavirus due to a contaminated water supply (Williams
and Akin 1986).

Angola, Burundi, Cameroo
n, the Democratic
Republic of
Congo, Djibouti, Ethiopia,
Ghana, Madagascar, Mala
wi, Niger, Rwanda and
Tanzania.

Sudan became the first African country to introduce the rotavirus
vaccine with GAVI Alliance funding last July -- only two years after
the World Health Organization recommended all countries
introduce rotavirus vaccines into their immunization programs.

- 9.2.3. Viruses -

• Astroviruses are another common cause of
gastroenteritis in young children, with 75 % of
those aged between 5–10 years shown to have
the astrovirus antibody in the UK (Kurtz and Lee
1978), with astrovirus is the major infection
causing serotype (Lee and Kurtz 1994).

• As with bacterial infections, many incidents of viral disease asociated with
drinking water have been attributable to untreated or inadequately
treated water or to defects within the distribution system (Craun1988).

» Gerba and Rose (1990) have produced an excellent review
on viruses in source and drinking waters.

- 9.2.3. Viruses -

• Out breaks of water borne viral disease, other than infectious
hepatitis, are diﬃcult to recognize because viruses tend to
cause non-apparent or latent infections (Tyler1985).

• Each year a large percentage of reported cases of water borne
disease are of unknown aetiology (Herwaldt etal. 1992;
Galbraith etal. 1987).

- 9.2.3. Viruses -

• One possible explanation for such defects in the data is that
epidemiological methods are not adequate enough to detect
low level transmission of viral diseases via water.

• This is because a single viral type may produce a wide variety
of symptoms which may not be attributable to a single
aetiologic agent, also diﬀerent viruses can produce similar
symptoms (Tyler 1985).

- 9.2.3. Viruses -

• Sewage treatment, virus dilution, natural inactivation, water
treatment, and other factors combine to reduce viral numbers
to a few survivors in large volumes of water (Metcalf 1978).

• In the more developed regions of the world, the possibility of
viral transmission of water borne disease depends on the
ability of minimum quantities of virus causing infections (APHA
1992).

- 9.2.3. Viruses -

• Detecting viruses in water through the recovery of infectious
virus involves three steps:
– (i) Collecting of representative
samples.

– (ii) Concentrating the viruses in the
sample.

– (iii) Identifying and estimating
quantities of the concentrated virus
(APHA 1992).

- 9.2.3. Viruses -

• Viral numbers are generally so low that their detection is
virtually impossible unless they are first concentrated.

• Many of the concentration techniques available are based on
one of two principles;
– either the filter adsorption-elution systems or
– ultra filtration systems (Sobsey 1975).

- Viruses -

- 9.2.3. Viruses -

• For many years chlorination was
considered to be eﬀective in preventing
contamination of water supplies by viruses.

• This conclusion was drawn from the results of epidemiological
studies, where it has been repeatedly shown that outbreaks
due to viral contamination occurred largely in situations where
there was in adequate or no chlorination (Galbraith et al.
1987; Herwaldt et al. 1992).

- 9.2.3. Viruses -

• However, in recent years there has been a
noticeable change in this situation.

• Enteric viruses have been isolated from
drinking waters which have been treated by
chlorination or other processes such as
ozonation and chemical coagulation.

- 9.2.3. Viruses -

• Initially the ability to survive chlorination was thought to be
due to a lack of contact time with chlorine (Melnick and Gerba
1980).

• It is now well established that some enteric viruses are more
resistant to chlorination than coliforms (Shaﬀer et al. 1980).

- 9.2.3. Viruses -

• Entero viruses have been recovered from waters which are
free from indicator organisms.

• There has been considerable debate over whether or not
there is continual low-level viral contamination of drinking
water which subsequently results in sporadic viral infections
among consumers (Sellwood and Dadswell 1991).

- 9.2.4. Protozoa -
• Protozoan pathogens of man are almost exclusively conﬁned
to tropical and sub-tropical areas, which is why the increased
occurrence of Cryptosporidium and Giardia cysts in
temperate areas is causing so much concern..

- 9.2.4. Protozoa -
Giardiasis
• Giardia lamblia is a flagellated protozoan belonging to the class
Zomastigophorasida, order Diplomonadonda and family
Hexamitidae.

• It was first recorded in 1681 by Leeuwenhoek who discovered
the organism in his own stools.

• It was later named Giardia lamblia after Giard who studied the
parasite and Lamb who first described it.

- 9.2.4. Protozoa -
Giardiasis
• For more than a century after its initial
discovery, the pathogenic potential of
Giardia was not fully appreciated.

• Indeed up to the 1960s, it was widely
believed to be a commensal parasite of
doubtful pathogenicity. Giardia lamblia

- 9.2.4. Protozoa -
Giardiasis
• Giardia lamblia exists in a trophozoite and cyst form.
Trophozoites are easily
recognised. Their bodies
are pear or kite
shaped, approximately 9–
21 µm long by 6 µm wide
with an anterior sucking
disc on the ﬂattened
ventral surface.

Cysts are ovoid,14–16 µm long and 6–12
µm wide and are quadrinucleate.

Giardiasis

Giardia cysts are
relatively resistant
to environmental
conditions and are
capable of survival
once excreted for
long periods,
especially in winter.

- 9.2.4. Protozoa -
Giardiasis
• Giardia is one of the most common waterborne parasites in the
United States.

• Giardia has been blamed for illnesses from both recreational
and drinking water.

• Giardia exists within every region of the United States and it is
also found worldwide.

- 9.2.4. Protozoa -
Giardiasis
• A study of raw water supplies in the USA by Le Chevallier et al.
(1991) found that Giardia cysts are present in as many as 81%
of raw water supplies largely due to the introduction of sewage
eﬄuents and in 17% of ﬁnished water supplies (Le Chevallier et
al. 1991).

• A similar survey in Scotland found that 48% of raw waters and
23% of treated water supplies sampled contained cysts (Gray
1994).

- 9.2.4. Protozoa -
Giardiasis
• Giardiasis is quite contagious. Just one infected human or
animal can release millions of Giardia parasites into the
environment through fecal matter.
• As few as 10 microscopic Giardia parasites in a glass of water
can cause a severe case of Giardiasis in the human being who
drinks it.

• The parasites are often found alive in soil, food, water, and
contaminated surfaces.

- 9.2.4. Protozoa -
Giardiasis
• While you can be infected by Giardia by swallowing the
parasite, Giardia is not spread through blood contact.
• Here are some common ways the Giardia parasite is
transmitted:
– Swallowing contaminated water while swimming in
pools, fountains, hot tubs, lakes, rivers, ponds, streams, springs, and
water parks.
– Eating uncooked food that has been contaminated with Giardia (i.e.
through unsanitary food preparation).
– Accidentally picking up Giardia from contaminated surfaces like
diapers, bathroom fixtures, or toys

- 9.2.4. Protozoa -
Giardiasis
• The symptoms of giardiasis usually appear about 1 to 2 weeks
after infection by the Giardia parasite. The symptoms of
giardiasis include:

– Diarrhea – Upset stomach
– Intestinal gas – Nausea
– Stomach cramps – Dehydration and weight loss
– Abdominal pain above the navel – Greasy stools

- 9.2.4. Protozoa -
Giardiasis
• To prevent infection, do not drink (or accidently swallow)
untreated water from lakes, rivers, streams, springs or shallow
wells.
• In countries where the water supply may not be
safe, untreated drinking water or ice should be avoided.
• All raw vegetables or fruits should be washed before eating in
water known to be uncontaminated.
• Good hygiene, such as hand washing, can help prevent
infection and reduce spreading giardiasis to other people.

- 9.2.4. Protozoa -
Cryptosporidiosis
• What is Cryptosporidiosis?

• Cryptosporidiosis is a disease caused
by an intestinal parasite called
Cryptosporidium commonly found in
lakes and rivers, especially when the
water is contaminated with sewage
and animal wastes.

- 9.2.4. Protozoa -
Cryptosporidiosis
• How do you get cryptosporidiosis?
• The parasite Cryptosporidium parvum is found in the feces of
infected animals and people.

• The parasite, which can be present in sewage or runoff from
feed lots, can contaminate water sources, and several large
waterborne outbreaks have occurred.

• Outbreaks also have occurred in child day care centers. In
Illinois, 75-100 cases of cryptosporidiosis are reported annually.

- 9.2.4. Protozoa -
Cryptosporidiosis
Persons, dogs and cats become infected
when they swallow this parasite.

This is one reason why hands should be
washed after contact with pets.

Hands also should be washed after changing a
child's diaper and after using the toilet.

- 9.2.4. Protozoa -
Cryptosporidiosis
• How serious is cryptosporidiosis?
• Symptoms can last for up to 30 days in persons who are
otherwise healthy.
• In persons with weakened immune systems, including people
with HIV/AIDS and cancer, transplant patients taking
immunosuppressive drugs and people with genetically
weakened immune systems, symptoms can persist indefinitely.
• Persistent diarrhea due to cryptosporidiosis in these persons
can lead to death.

- 9.2.4. Protozoa -
Other protozoans
• Entamoeba histolytica is carried by about 10% of the
population in Europe and 12% in the USA.

• In countries where the disease is wide spread the highest rate
of incidence occurs in those groups with unprotected
water supplies, in adequate waste disposal facilities, and poor
personal hygiene.

- 9.2.4. Protozoa -
Other protozoans
• Naegleria are free living protozoans widely found in variety of
surface and waste waters, especially surface waters that are
heated (Marciano-Cabaral et al. 1988).

- 9.2.4. Protozoa -
Other protozoans
• Naegleria fowleri is the main human pathogenic species which
was ﬁrst reported in 1965 in Australia.

• It normally enters
the body through the
nasal cavities while
swimming in infected
water.

- 9.2.4. Protozoa -
Other protozoans

- 9.2.5. Parasitic worms -

• The incidence of worm infection in European countries is
generally low and is limited to Taenia and Ascaris.

• Infection is normally contracted from animals reared for
food, although many incidents of infection from contaminated
water have been reported.

• Ova of both genera are commonly isolated from sewage.


• There are a number of other parasitic worms that can also be
transmitted by faecal contamination of water supplies.

• These include several hookworms, schistossomes, and a
number of tapeworms, such as the ﬁsh tapeworm
Diphyllobothrium latum.

- 9.3. Indicator Organisms -

• Group of microorganism use to reflect the quality and safety of
a process food product
– In water
• Vibrio cholera
• Salmonella typhi
• Shigella spp
• Hepatitis
– In food
• Coliform


Criteria for use of an organism as an indicator

• Must be associated with feces
• Should not be a natural contaminant
• Easy to detect
• Test should be less complex than test for pathogen
• Growth limit under conditions
• Should not survive processing
• Processing should have same effect on pathogens


Suggested indicator organisms

• Fecal organism
– Fecal coliform
– Escherichia coli
• Enteric bacteria
– Shigella spp.
– Salmonella spp


Coliforms

• Coliform indicates processing contamination !
• Coliform can grow on food processing equipment or !
• in environment
• Several genera are considered to be coliforms !
• Escherichia
• Enterobactor
• Klepsiella
• Citrobactor

Coliforms

• Source of coliform
– Fecal group --GI tract of humans and animals !
– Non-fecal group --Soil and plant
• Coliform group
– Gram negative, rod shape, aerobic or facultative aerobic
– non endospore former
– ferments lactose at 30-37 ° C for 24-48 hrs


Coliforms
• Fecal coliform
– found only in GI tract
– can grow at elevated test temperature
– ferment LST at 44.5 ° C for 24 hrs


Coliforms
• Methods for isolation of coliforms
– Presumptive test
• Liquid media (MPN)
– LST (Lauryl Sulfate Tryptose)
• Solid media
– VRBA (Violet red bile agar)


Coliforms
• Confirm test
– Liquid media (MPN)
• BGLB (Brillant Green Lactose Bile broth)
• EC (EC broth)


Presumptive test of coliforms
• LST
– triplicate tubes for each dilution
– incubate at 32-35 °C for 24-48 hrs
– coliform grow---turbidity and gas
• VRBA
– surface plate method---spread on plate !
– C for 24-48 hrs ° incubate at 32-35 !
– red, purple colonies with ring of precipitate bile !
– salt around colonies


Confirmation of coliforms
• BGLB
– Incubate at 32-35° C for 24-48 hrs
– Coliform report as MPN
• EC
– Incubate at 44.5 ° C for 24 hrs
– Fecal coliform report as MPN

Identification of coliforms
• Select colony or positive tubes and streak onto PCA slants
• Identify the microorganism
– Gram stain
– Biochemical test
» IMViC test
• Indole test
• Methyl red
• Voges-Proskauer
• Citrate utilization
– Selective media
• EMB agar (Eosin Methylene Blue Agar)

• IMViC test: use to differentiate between the coliform
group
– Indoletest
• Bacteria degrade tryptophan to indole
– Methyl red
• Bacteria produce acid from glucose
– Voges-Proskauer
• Detect acetylmethylcarbinol from glucose
– Citrate utilization
• Bacterial utilize citrate as a carbon source


IMViC test

Public health

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (20)

Destacado

Destacado (20)

Similar a Public health

Similar a Public health (20)

Más de Fatih University

Más de Fatih University (20)

Último

Último (20)

Public health