1. General characteristics
Round in cross-section
Unsegmented
Digestive system complete
Possess mouth, oesophagus , intestine and anus
Have separate sexes
Nemathelminths
2. Classification of Nemathelminths
INTESTINE NEMATODE
Small intestine
Ascaris
lumbricoides
Hook worm
Strongyloides
stercoralis
Large intestine
Trichuris trichuria
Enterobius
vermicularis
BLOOD & TISSUE
NEMATODE
Adults or larval stage in
tissue
Filaria –
Wuchereria bancrofti
Brugia malayi
Onchocerca volvulus
Loa loa
Trichinella spiralis,
Draconculus medinensis
4. INTESTINAL NEMATODES
General features
Live in gastro-intestinal tract
In humans, often spread by poor hygiene related to
feces
Most species are geo-helminths
Female worms are oviparous
Humans are the only or major host of intestinal nematode
5. Cont…
It includes
Ascaris lumbricoides
Trichuris trichiura
Enterobius vermicularis
Strongyloides stercoralis
Ancylostoma duodenale
Nectator amircanus
Before becoming adults in their human host, the larvae of A.
lumbricoides, S. stercoralis , and hookworms have heart lung
migration
6. Enterobius vermicularls
Common name: “Pin Worm” or “threadworm” or “
seat worm”
Epidimology
occurs world-wide
Children (5-14 years ) are more commonly
infected than adults
Occur in group living together
7. In Ethiopia : 5 % school children in rural
communities in Gondor region had
E. Vermicularis eggs under their finger nails
and that only 0.5% of them were found to shed
eggs in the stool
Recent studies done using routine stool
examination method, a prevalence rate up to 1%
were reported
9. Morphology of Enterobius vermicularis adult
female
They are small white worms with pointed tail
They are small white worms with pointed tail
swollen cuticle at anterior end prominent
swollen cuticle at anterior end prominent
esophageal end bulb
esophageal end bulb
10. Egg
Size: 50-60m
Shape: oval but flattened
on one side, rounded
on the other side
Shell : Smooth and thin
but with double shell
Content: either a small
granular mass or a
small curved up larvae
13. Transmission and Life cycle
Transmission
Person –to- person transmission(ingestion and
air borne)
Eggs remains viable 20 days
Autoinfection
Retro infection
14. Life cycle
Ingestion embryonated eggs, usually carried on
fingernails, clothing, bedding or house-dust.
Eggs hatch in stomach, larvae migrate to caecal
region where they mature into adults
Copulation takes place in the caecum
Gravid females migrate nocturnally outside the anus
and oviposit on the perianal area
1 pin worm lay over 10,000 -15,000 eggs /day
15. With in 4-6 hours being laid the egg contain
infective larvae
Perianal itching from the eggs Induces scratching,
and hence the eggs are transmitted to the mouth on
the fingers
Retroinfection, or the migration of newly hatched
larvae from the anal skin back into the rectum
Interval from ingestion of infective eggs to
oviposition by the adult females is about one month
The life span of the adults is about two months
18. Clinical features
Nocturnal anal pruritis
The cause of this is unknown, but may be related to the
intensity of the infestation, and/or an allergic reaction
to parasite
Sleeplessness, because of the irritation
Vulvovaginitis, and even urethritis may occur in
girls when migrating worms lay their eggs in these
sites
Abdominal pain or appendicitis resulting from
the worms are considered to be very rare
20. Egg of E. vermicularis and scotch tape preparation
21. Laboratory Diagnosis
1.Finding eggs from perianal skin using adhesive tape
or swab method
Done by pressing transparent adhesive tape
("Scotch test", cellulose-tape slide test) on the
perianal skin and then examining the tape placed
on a slide.
Alternatively, anal swabs or "Swube tubes" (a
paddle coated with adhesive material) can also be
used.
Collect sample in the morning, before defecation
and washing
22. The “Scotch Tape Test”
place a piece of Scotch Tape
on the anal area.
The tape is placed on a slide
and examined under a
microscope for the flat sided
eggs.
23. 2. Finding eggs in the faeces
Eggs can also be found stool, but less
frequently
Less then 10% found in stools, i.e. not a useful
examination;
Occasionally eggs can be found in the urine or
vaginal smears
24. 3. Finding of female worms from perianal skin or
faeces
Adult worms are also diagnostic, when found in
the perianal area, or during ano-rectal or vaginal
examinations
25. Treatment
Pyrental Pamoate or Mebendazole
Prevention and Control
1.Treating all members of a family in which infection
has occurred
2. Wearing tight-fitting cotton pants to infected
children
26. 3. Washing of the anal skin each morning
4.Washing of clothing worn at night
5. washing hands after using toilet and before
eating , avoidance of putting fingers in the mouth
& trimming finger
27. Are hematophagous nematodes
Two major species
Ancylomstoma duodenale
Necator americanus
Less important : A. ceylanicum, A.
braziliense ,A. caninum , A.tubaeforme, A.
buckleyi
Hook Worms
28. Epidimology
Widely distributed throughout the tropics and
subtropics
More than 1 billion people are infected world-
wide
Cause daily blood loss of 7 million liters
Most commonly infected are children, agricultural
workers and miners
29. Ancylostoma is found in Europe around the
Mediterranean, on the West coast of South
America and in parts of China and India
Necator is found over much of the western
hemisphere, Africa and South East Asia
31. In Ethiopia : Necator americanus are more common
than Ancylostoma duodenale
Highest infection rates: Ilubabor, Kefa ,Welega
A.duodonale is associated with areas of poor
soil coverage and high rate of drainage
N.americanus is found in red soil areas on flat
plain
32. Altitude and moisture is the major factor affecting
their distribution
Hook worm infection is absent in low,hot dry
areas of Ethiopia and above 2500m alt
33. Habitat
Adult: Jejunum and less often in the duodenum
of man
Eggs: In the faeces; not infective to man
Rhabditiform and filariform larvae: free in soil
and water
34. Morphology : Adult
A.duodenale N.americanus
pathogen city more pathogenic less pathogenic
Size longer and thicker short and thinner
male 8mm 7-9mm
female 10-13mm 9-11mm
Buccal capsule large and oval small and round
Jaw like teeth cutting plates
Buccal cavity short,10-15 m long ,15-16 m in
in length length
lumen is large lumen is short
35. Head is slightly bend
(hook) and
the mouth carries
characteristic teeth
(Ancylostoma) or plates
(Necator)
The posterior end of the
male worm is elaborated
into a copulatory bursa
37. Teeth in their buccal cavity enable their
attachment to intestinal mucosa - from where
they suck their host's blood
The worm's mean life span Is 1 - 3 years
38. Egg:
2x egg are produced by A. duodenale
(20,000egg/day) than N. americanus
Size : 65-40m
Shape: oval
Shell: very thin and appears as black line
Colour: the cells inside are pale gray
Content: contains an ovum which appears
segmented usually 4-8 blastomeres
41. Life cycle
Eggs are passed in the stool , and under favorable
conditions (moisture, warmth, shade),
Rhabditiform larva larvae hatch in 1 to 2 days in the
feces and/or the soil
After 5 to 10 days (and two molts) they become
become filariform (third-stage) larvae that are
infective
larvae can survive 3 to 4 weeks in favorable
environmental conditions.
42. On contact with the human host, the larvae
penetrate the skin and are carried through the
veins to the heart and then to the lungs
They penetrate into the pulmonary alveoli, ascend
the bronchial tree to the pharynx, and swallowed
The larvae reach the small intestine, where they
reside and mature into adults
they attach to the intestinal wall with resultant
blood loss by the host
44. Clincal features
Arise from a combination of intestinal
inflammation and progressive iron/protein-
deficiency anemia
Most individuals with hookworm infection are
asymptomatic (90%)
High loads of the parasite(20 - 100 worms)
coupled with poor nutrition (inadequate intake of
protein and iron) eventually lead to anemia
45. Skin penetration and associated secondary
bacterial infection can result in “ground itch”
Pulmonary phase is usually asymptomatic
Intestinal phase: adult worms attach to the
mucosa and feed on blood. Worms continuously
move to new places exacerbating bleeding
48. Hookworms
The main concern with hook
worm disease is blood loss
0.03 ml (N.a.) to 0.26 ml (A.d)
per worm,
up to 200 ml per day in heavy
infections
Chronic heavy infection results
in anemia and iron deficiency
Together with malnutrition
infection can severely stunt
growth and development in
children
Anemia leads to weakness and
fatigue in adults
49. Symptoms of hookworm infection depending on the site at which the
worm is present and the burden of worms
Table 2. Clinical features of hookworm disease
Site Symptoms Pathogenesis
Dermal
Local erythema, macules,
papules (ground itch)
Cutaneous invasion
and subcutaneous
migration of larva
Pulmon
ary
Bronchitis, pneumonitis
and, sometimes,
eosinophilia
Migration of larvae
through lung,
bronchi, and trachea
Gastro-
intestina
l
Anorexia, epigastric pain
and gastro-intestinal
hemorrhage
Attachment of adult
worms and injury to
upper intestinal
mucosa
Hematol
ogic
Iron deficiency, anemia,
hypoproteinemia, edema,
cardiac failure
Intestinal blood loss
50. Laboratory Diagnosis
1.Finding eggs in faeces
A.duodenale and N.americanus eggs
morphologically indistinguishable
Microscopic identification of eggs in the stool is the
most common method
The recommended procedure:
1. Collect a stool specimen.
2. Fix the specimen in 10% formalin.
3. Concentrate using the formalin–ethyl acetate
sedimentation technique
4. Examine a wet mount of the sediment.
51. The diagnostic stage is the egg in the feces.
Eggs of both species look the same
52. freshly passed faeces should be examined
If more than 12 hours old ,a larva may be seen
inside the egg
If more than 24 hours old ,the larva hatch
hookworm : deep buccal cavity
S. stercoralis : shorter buccal cavity
