parasitology- ancylostoma duodenalale,necator americanus

1. Hookworm
Durga Satheesh

2. HISTORY AND DISTRIBUTION
• ancient times-ebers papyrus
• tropics and subtropics
• Ancylostoma duodenale and Necator americanus are
human parasites.
• A.duodenale described by Dubini in 1843 in Italy. Life
cycle described by Looss 1898 in Egypt
• N.americanus identified by Stiles 1902 in USA
• A.duodenale was distributed to north and
N.americanus to the south in endemic zones
• Ancylostoma was prevalent along Mediterranean coast
of Europe and Africa,North India,China,Japan
• Necator was prevalent in central and South America
Central and south Africa, South India
• Now it has a blurred geographical distribution

3. ANCYLOSTOMA DUODENALE
MORPHOLOGY
o Stout, Cylindroidal
o Pale pink or greyish white but appear
reddish brown due to ingested blood
o Body is curved, dorsal concave, ventral convex
o Ant. end is constricted and bent dorsally
o Mouth is directed dorsally

4. A prominent buccal
capsule, reinforced
with chitin like
substance – carries
two pairs of hook like
teeth ventrally,
dental plate with a
median cleft dorsally

5. o Male worm 8-11mm long, 0.4mm thick
o Posterior end of male is expanded into a
copulatory bursa supported by fleshy rays
o Rays help in differentiating between species
o rectum and genital canal open into Cloaca in the
bursa
o 2 long retractile bristle like copulatory spicules,
tips of which project from the bursa

6. o Female worm  Larger, 10-13mm long, 0.6mm
thick, hind end conoid, subterminal anus situated
ventrally
o Vulva opens ventrally, at the junction of middle
and posterior thirds of the body
o Vagina leads to 2 intricately coiled ovarian tubes
o During copulation, copulatory bursa attaches to
the vulva Y shaped appearance

9. o Eggs are oval or elliptical, 60 x 40 µm, colourless,
not bile stained, with a thin transparent hyaline
shell membrane
o Egg contains unsegmented ovum
o During its passage down intestine, ovum
develops
o contain 4-8 blastomeres when passed in faeces
o Clear space between segmented ovum & egg
shell.eggs float in sat. NaCl
o 25,000-30,000 eggs a day and 18-54 million
during its life time

11. LIFE CYCLE
o Humans are the only natural host
o Adult worm lives in small intestine of infected persons-
jejunum
o Eggs passed in faeces-not infective
o Embryo develops inside eggs when deposited in soil
o In about 2 days, Rhabditiform larva hatches out,
250µm long
o Grows in size by feeding bacteria and organic matter
and it moults twice on 3rd and 5th days after hatching
o Third stage- filariform larva- infective form
o 500-600µm long with a sharp pointed tail, it is non
feeding form
o Live in soil for 5 weeks –heads waving in air

12. o When a person walks barefooted, they
penetrate the skin-enter subcutaneous tissue
o Skin b/w toes, dorsum of foot, medial aspect
of sole are common sites of entry
o In subcutaneous tissue larvae enter the
venules and reaches right heart and lungs
o Break out of capillaries to reach alveoli-
migrate up the respiratory tract to the
epiglottis
o They crawl over epiglottis to pharynx and are
swallowed

13. o In jejunum, they moult and develop a
temporary buccal capsule-get attaches to gut
o Feed and grow in size, undergo 4th and final
moulting, develop buccal capsule and grow into
adults
o From time of infection, it takes 6 wks for the
worm to become sexually mature
o Rarely infection occurs through buccal route
o Transmammary and transplacental
transmission has been reported

14. LIFE CYCLE OF ANCYLOSTOMA

15. NECATOR AMERICANUS
MORPHOLOGY
o Adult worms are slightly smaller than
A.duodenale
o Male 7-9 mm long and 0.3mm thick
o Female 9-11mm long and 0.4mm thick
o Anterior end is bent in the opposite direction
of general curvature of body
o They have a smaller buccal capsule with two
pairs of semilunar cutting plates

17. o Copulatory bursa is long and wide
o Copulatory spicules are fused at the ends to
form a barbed tip
o In the female vulva is placed in the middle of
the body
o Eggs are identical with those of A.duodenale
o Life cycle is also similar. Life span is much
longer about 4-20 yrs
o 2-7 yrs in A duodenale

18. necator

19. DISTINGUISHING FEATURES B/W
ANCYLOSTOMA AND NECATOR
ANCYLOSTOMA NECATOR
ADULT ANTERIOR CURVATURE ANTERIOR CURVATURE IN
UNIFORM WITH BODY OPPOSITE DIRECTION
FEMALE CURVE
VULVA OPENS AT JUNCTION OF OPENS A LITTLE IN FRONT OF THE
MIDDLE AND POSTERIOR MIDDLE
THIRD
BUCCAL 2 PAIRS OF HOOK LIKE 2 PAIRS OF SEMILUNAR CUTTING
TEETH VENTRALLY AND A PLATES INSTEAD OF TEETH
CAPSULE DENTAL PLATE WITH
MEDIAN CLEFT DORSALLY
COPULATOR THE DORSAL RAY IS SINGLE HAS A PAIRED DORSAL RAY
WITH A SPLIT END
Y BURSA
COPULATOR SEPERATE FUSED AT TIP
Y SPICULES

20. PATHOGENESIS AND CLINICAL FEATURES
o When filariform larva enters the skin, they
cause severe local itching
o Erythematous papular rash may develop
o Scratching and secondary bacterial infection
may follow
o This condition is called Ground itch, occurs
when large number of larvae penetrate the
skin, more common with necator
o Larvae sometimes cause creeping eruption-
more common in animal hookworms

21. • Larvae migrate
between
stratum
germinativum &
S.
corneumserpi
genous
vesicular lesion

22. o When larvae enters the alveoli, they may cause
minute local haemorrhages.
o Clinical pneumonitis develops only in massive
infections
o Important manifestations of ancylostomiasis is in the
intestine
o Worms attach to gut mucosa by their buccal capsules
o Suck a portion of intestinal villi, utilise gut epithelial
cells and plasma for their food
o The worm sucks in blood, which passes out
undigested through its intestines
o Adult ancylostome can suck about 0.2ml blood and
necator sucks 0.03ml per day
o The worms frequently leave one site and attaches to
another site

23. o Bleeding from the site continue for sometime
due to the anticoagulant activity of the secretions
of the worm
o Blood loss over a period of time leads to
microcytic hypochromic iron deficiency anaemia
o Degree of anaemia is directly proportional to
worm burden
o Worm loads upto 100 worms cause no
symptoms,500-1000 or more cause significant
blood loss and anaemia
o Egg count less than 5 eggs per mg of faeces cause
no clinical disease,20 eggs or more significant
anaemia, 50 or more massive infection

24. o In hookworm disease, intestinal absorption of
iron is normal so oral administration of iron
can correct anemia
o Hookworm infection cause intestinal
syndrome resembling peptic ulcer- with
epigastric pain, dyspepsia and vomiting.
o Reddish or black stool, diarrhoea may be seen
in acute stage
o Anaemia leads to lassitude and dullness,
hypoprotenemia etc
o Severe hookworm anemia leads to cardiac
failure

25. DIAGNOSIS
o Demonstration of eggs in faeces by direct
microscopy or by concentration methods
o Rhabditiform larvae may present in samples
which are examined 24 hrs or more after
collection
TREATMENT
o MEBENDAZOLE
o PYRANTEL PAMOATE
o THIABENDAZOLE is less effective
o BEPHENIUM HYDROXYNAPHTHOATE is active
against Ancylostoma but not against Necator

26. EPIDEMIOLOGY AND PREVENTION
o Conditions required for maintenance of endemic
hookworm infection are
2. Presence of infected persons
3. Dispersal of eggs in soil
4. Appropriate environmental factors facilitating
development of eggs
5. Opportunity for the larvae to infect people through
exposed skin surface
o These conditions prevail throughout the year-in tropics
but in subtropics it exist only seasonally-in warmer
months
o Prevention of SOIL POLLUTION WITH FAECES,USE OF
FOOTWEAR,GLOVES,TREATMENT OF PATIENTS AND
CARRIERS etc can limit the infection

27. THANK YOU