Parasite and it importance

1. PARASITES OF MEDICAL
IMPORTANCE
GREGORY LUGULA

2. Ascaris Lumbricoides
and Trichuris
Trichiura

3. Learning Objectives
• List intestinal nematodes
• Describe the characteristics of ascaris
lumbricoides and trichuris trichiura
• Describe the life cycle of ascaris lumbricoides
and trichuris trichiura
• Describe the medical importance of ascaris
lumbricoides and trichuris trichiura

4. Intestinal nematodes are round worms that infest the
gastrointestinal tract of human and other animals.
• They are characterized by having separate-sexes and
unsegmented body, body cavities and complete
digestive, reproductive and nervous systems.
• Examples of intestinal nematodes include Ascaris
lumbricoides, Trichuris trichiura, Necator
americanus/ Ankylostoma duodenale (hook worm),
Enterobius vermicularis, Trichuris trichiura and
Strongiloides stercoralis

5. Characteristics of Ascaris
Lumbricoides (True Round Worm)
• Large size of about 15 – 31cm length and 2-4
mm width, where females are relatively larger
than males
• The mouth is surrounded by three prominent
lips
• Males have the posterior end which is curved
ventrally and the tail is curled with two
prominent specules
• The female tail is straight and pointed

6. Morphology of Adult Ascaris
Lumbricoides

7. Eggs
• Size 45-70 x 35-50 µm
• There are three types of eggs
• Fertilized egg
• Decorticated and
• Unfertilized
• The fertilized egg is layered with outer albuminous covering
which is coarsely mammilated (= warty), thick egg shell,
unsegmented embryo when laid.
• Decoticated egg is devoid of the mammilated coat. Can
easily be confused with the hookworm ova.
• Unfertilized egg is has all the layers fused together and
resemble vegetable fibres

8. Morphological Features of Different
Types of Ascaris Lumbricoides Ova

9. A fertilized egg of Ascaris lumbricoides
Note: The egg is covered with a thick shell that appears lumpy
(bumpy) or mammillated

10. A "decorticated," fertilized egg of
Ascaris lumbricoides

11. Unfertilized egg of
A. lumbricoides

12. • Ascaris lumbricoides is transmitted through
ingestion of eggs from food, water or fingers
contaminated with faeces (Faecal oral route).

13. Life Cycle of Ascaris Lumbricoides
• Adult worms live in the lumen of the small intestine
• A female may produce approximately 200,000 eggs
per day, which are passed with the faeces
• Eggs are not infective immediately when passed in the
faeces
– Unfertilized eggs may be ingested but are not infective
– Fertile eggs develop an embryo and become infective after
18 days to several weeks depending on the environmental
conditions (optimum: moist, warm, shaded soil)
• Infective eggs are swallowed
• The egg hatches to release the larvae

14. • The larvae invade the intestinal mucosa, and are carried via
the portal vein to the systemic circulation, to the heart and
eventually reach to the lungs (heart lung migration)
– The larvae mature further in the lungs (10 to 14 days)
• They break out from the blood capillaries and appear in
the alveoli, ascend the inverted bronchial tree to the throat,
and are swallowed again
• Upon reaching the small intestine, they develop into adult
worms in the period of 2 to 3 months after ingestion of the
infective eggs
• The male fertilizes the females and the female’s starts
oviposition
• Adult worms can live from 1 to 2 years

15. Life Cycle of Ascaris Lumbricoides

16. Medical Importance of Ascaris
Lumbricoides
• Ascaris lumbricoides causes
– Ascaris pneumonitis (Loeffler’s syndrome)
– Allergic manifestations (asthma)
– Migrating larvae may reach the brain and cause encephalitis and
meningitis
– Adult worms can cause:
❖ Intestinal ascariasis
❖ Malnutrition and general body debility
❖ Intestinal obstruction
❖ Appendicitis
❖ Intestinal perforation
❖ Migrating adults may reach the brain and cause encephalitis
(rarely occurs)

17. Diagnosis
• Specimen
– Stool
• Technique
– Microscopy
– Wet mount and concentration method to detect
ova
– Clinical observation of worms passed

18. Drugs of Choice:
• Albendazole
• Mebendazole
• Levamisole
• Pyrantel pamoate
• Piperazine

19. Characteristics of Trichuris trichiura
(Whipworm)
• The adult worm is greyish white or pinkish and lives in the caecum with
the slender anterior end embedded in the mucosa between intestinal villi
• The male
– Is 3 – 4.5 cm long
– Has a thin anterior portion which is half as long as the thicker posterior portion
– The tail end is curved and terminates in a spicule
• The female
– Is 3.5 – 5.5 cm long
– Has a thin anterior portion which is twice as long as the thick posterior half
containing a stout uterus packed with eggs
• The eggs
– Measures 50x22 µm is brown and has characteristically barrel shaped
– Has a single thick egg shell with a translucent plug at each end (bipolar plug)
– It contains an unsegmented embryo at oviposition

20. Trichuris trichiura - Adult Worms and
Eggs

21. The egg of Trichuris trichiura

22. Mode of Transmission
❑ Trichuris trichiura is transmitted through
ingestion of eggs from food, water or fingers
contaminated with faeces (Faecal oral route).

23. Life Cycle of Trichuris trichiura
1. The undeveloped (unembryonated) eggs are passed with
the stool
• In the soil,
2. The eggs develop into a 2-cell stage,
3. An advanced cleavage stage,
4. Then develop an embryo
– The whole process from oviposition to infective stage takes about
15 to 30 days
5. After ingestion, the eggs hatch in the small intestine, and
release larvae
6. The larvae mature and establish themselves as adults in
the colon

24. Life Cycle of Trichuris trichiura
• The adult worms (approximately 4 cm in length)
live in the cecum and ascending colon
• The adult worms are fixed in that location, with
the anterior portions threaded into the mucosa
• The females begin to oviposit 60 to 70 days after
infection
• Female worms in the cecum shed between 3,000
and 20,000 eggs per day
• The life span of the adults is about 1 year

25. Life Cycle of Trichuris trichiura

26. Medical Importance of Trichuris
Trichiura
• Adult worms causes:
– Intestinal Trichuriasis
– Appendicitis
– Dysentery
– Rectal prolapse
– Anaemia

27. Medical Importance of Trichuris
Trichiura
Diagnosis
• Specimen
– Stool
• Technique
– Microscopy :
▪ Wet mount and concentration method to detect
ova
– Clinical observation of worms when the rectum
has prolapsed

28. Medical Importance of Trichuris
trichiura
Drugs of Choice
• Albendazole
• Mebendazole
• Levamisole
• Pyrantel pamoate
• Piperazine

29. Key Points
• Ascaris lumbricoides and Trichuris trichiura are intestinal
round worms which are transmitted through ingestion of
eggs from food, water and fingers contaminated with
faeces.
• Acaris lumbicoides causes Ascariasis (Ascaris pneumonitis,
allergic manifestations, encephalitis and meningitis).
• The life cycle of Ascaris lumbricoides follows heart-lung
migration.
• Infection of Trichuris trichiura leads to dysentery and rectal
prolapse.
• Diagnosis of both Ascaris lumbricoides and Trichuris
trichiura depend on recovery and identification of eggs in
the faeces.

30. Evaluation Quiz
• What are the morphological characteristics of
Ascaris lumbricoides?
• What are the differences between ova of
Ascaris lumbricoides and that of Trichuris
trichiura?
• What are the laboratory techniques used to
identify both Ascaris lumbricoides and
Trichuris trichiura?

31. Ancylostoma Duodenale,
Necator Americanus and
Enterobius Vermicularis

32. Learning Objectives
• List characteristics of Ancylostoma duonale,
Necator americanus and Enterobius vermicularis
• Describe the life cycle of Ancylostoma duodenale,
Necator americanus and Enterobius vermicularis
• Describe the medical importance of Ancylostoma
duodenale, Necator americanus and Enterobius
vermicularis

33. Characteristics of Ancylostoma duodenale, Necator
americanus [Hookworms]
The Hookworms
• Hookworms are parasitic round worms that
lives in the small intestine of its host, which
may be a mammal such as a dog, cat, or
human.
• Two species of hookworms which are
pathogenic to human are:
❖ Ancylostoma duodenale
❖ Necator americanus

34. Morphological Characteristics
Ancylostoma duodenale
• Are small grayish white or pink with the head slightly
bent in relation to the rest of the body. This bend
forms a definitive hook shape at the anterior end for
which hookworms are named.
• They possess well developed mouths with two pairs of
ventral teeth.
• Males measure approximately one centimeter by 0.5
millimeter, the females are often longer and stouter.
• Additionally, males can be distinguished from females
based on the presence of a prominent posterior
copulatory bursa.

35. Morphological Characteristics
Necator americanus
• Is very similar in morphology to Ancylostoma
duodenale.
• Is generally smaller than Ancylostoma duodenale
with males usually 5 to 9 mm long and females
about 1 cm long.
• Possesses a pair of semi lunar cutting plates in the
buccal capsule.
• Additionally, the hook shape is much more
defined in Necator than in Ancylostoma

36. Morphological Characteristics
Eggs :
• The eggs are oval or elliptical, measuring 60 µm by 40 µm,
colorless, not bile stained with a single thin transparent
hyaline shell membrane.
• When released by the worm in the intestine, the egg
contains an unsegmented ovum.
• During its passage down the intestine, the ovum develops;
thus the eggs passed in faeces have a segmented ovum,
usually with 4 to 8 blastomeres.
• As the eggs of both Ancylostoma and Necator (and most
other hookworm species) are indistinguishable, to identify
the genus, they must be cultured in the lab to allow larvae
to hatch out.

37. Morphology of Hookworm
Mouth parts (teeth) of Ancylostoma duodenale

38. Morphology of Hookworm
Mouth parts (cutting plates) of Necator americanus

39. Morphology of Hookworm
Rhabditiform larva of hookworm

40. Morphology of Hookworm
Hookworm ova

41. Mode of Transmission
• Through skin penetration of infective
filariform larvae (third stage larvae or L3)
contained in the soil. In addition, infection by
A. duodenale may probably also occur by the
oral route.
• In rare cases, trans-mammary transmission
(mother to child) can occur via breast milk
when a mother is heavily infected.

42. Life Cycle of Hookworms
1. Eggs are passed in the stool and under favorable
conditions (moisture, warmth, shade), larvae hatch in
1 to 2 days.
2. The released rhabditiform larvae grow in the faeces
and/or the soil.
- The rhabditiform larvae are active and feed on
dead organic matter in the soil.
3. After 5 to 10 days (after two molts) they become
filariform (third-stage) larvae that are infective.
o The filariform larvae are not active and do not feed
o They can survive 3 to 4 weeks in favorable
environmental conditions in the soil.

43. 4. Upon contact with the human host, the larvae penetrate the skin,
invade the blood capillaries and are carried through the blood
vessels to the heart and then to the lungs.
o They break from the blood capillaries and appear into the
pulmonary alveoli, ascend the inverted bronchial tree to the
pharynx, and are swallowed.
5. The larvae reach the small intestine, where they reside and
mature into adults.
o Adult worms live in the lumen of the small intestine, where they
attach to the intestinal wall.
• The life span of adult worms in the small intestines is about 1 to 2
years.

44. Life Cycle of Hookworms

45. Medical Importance of Hookworms
Disease they Cause
• Ground itch at the time of skin penetration:
irritating vesicular rash limited to the site of
invasion, usually in the sole of feet or hands
• Pneumonia during heart lung migration
• Iron deficiency anemia, secondary to loss of
iron (and protein) in the gut

46. Medical Importance of Hookworms
Diagnosis
• Specimen
- Stool
• Technique:
❑ Microscopy :
-Wet mount and concentration technique to detect
ova.
❑ Culture (Kato Katz technique) for recovery of
rhabditiform larvae (but not routine)
❑ Clinical technique to when the worms are passed

47. Medical Importance of Hookworms
Drug of choice
• Albendazole
• Mebendazole
• Pyrantel pamoate

48. Characteristics of Enterobius
vermicularis [Pinworm, Seat Worm]
Female
• They are small, 9-12 mm x 0.4 mm
• Has a cervical alae (wing like expansion) at the anterior end
• There is a bucal cavity that terminates into a prominent
oesophageal bulb
• Has a long pointed tail
• The uteri of the gravid female are distended with eggs
Male
• 2-5 mm with a curved tail and a single spicule
• Males are seldom seen
Egg
• 50-54 x 20-27 µm with characteristic shape – flattened on one
side. Almost colourless with bean-shaped double contour shell

49. Eggs of Enterobius vermicularis in wet
mount

50. Eggs of Enterobius vermicularis in
cellulose preparation

51. Mode of Transmission
• Ingestion of eggs from contaminated fingers,
bedding and formites
• Inhalation of eggs from dust
• Autoinfection
• Retroinfection

52. Life Cycle of Enterobius vermicularis
1. Eggs are deposited on perianal folds. Self-infection
occurs by transferring infective eggs to the mouth with
hands that have scratched the perianal area
(Autoinfection).
2. The ingested eggs hatch in the small intestine to
produce larva
3. (4& 5). The larva matures and become adult in the
large intestine where the male fertilizes the female.
1. The female migrates to the perianal folds where
deposit eggs on perianal skin folds. The female worm
dies after laying eggs.

53. Life Cycle of Enterobius vermicularis
• These would be swallowed and follow the same
development
• Sometimes eggs hatch at the perianal area and the
larva migrates to the caecum where they mature to
become adults and fertilization takes place
(Retroinfection)
o Under optimal conditions, it takes 4 to 6 hours for
the eggs become infective.
• The time 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.

54. Life Cycle of Enterobius vermicularis

55. Medical Importance of Enterobius
vermicularis
Disease they Cause
• Pruritus ani is the main symptom and varies from
mild itching to acute pain which occurs mainly at
night.
o The pruritus provides scratching of the perianal
region resulting in excoriation and secondary
infection.
• Vulvitis may be caused by pinworms entering the
vulva causing a mucoid discharge and pruritus
vulvi.

56. Medical Importance of Enterobius
vermicularis
Diagnosis
• Specimen :
❑ Scotch tape swab
❑ Stool
• Technique :
❑ Microscopy
-Wet mount and concentration technique to
detect ova
❑ Examination of the tape swab for ova and adult
worm

57. Drugs of Choice
• Albendazole
• Mebendazole

58. Key Points
• Hookworm and Enterobius vermicularis are intestinal small
round worms
• Hookworm follows heart lung migration in its life cycle
while Enterobius vermicularis follows direct life cycle
without heart lung migration.
• Hookworm is transmitted through skin penetration by
filariform larvae in the soil
• Enterobius vermicluaris is transmitted through
o Ingestion of eggs from contaminated fingers, bedding, and
formites
o Autoinfection
o Retroinfection

59. Evaluation Quiz
• What is the mode of transmission of
hookworm?
• Mention the most common complication of
hookworm infection.
• Mention drugs of choice for enterobiasis and
hookworms.

60. medicines for health
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