2. Introduction to Parasitology
By Sh. Ghaffari
September 2012

3. Parasitology: definition
Parasitology: study of parasites
Animals:
Free-living
Symbiotic
Symbiosis
Phoresis
(to carry)
Commensalism
(eating at the same table)
Mutualism
positive reciprocal relationship
Parasitism
Metabolic dependence

4. Parasitism
Parasite (parasitos “para: beside; sitos: grain or food”)
Host
Parasitism: a form of symbiosis in which one organism (parasite) benefits at the expense of another organism of different species (host).
Must be:
Animals
Different species

5. Life cycle 1.Direct life cycle 2.Indirect life cycle
Medical Parasitology
Life cycle 1.Direct life cycle 2.Indirect life cycle
Parasite
Adult form/ Sexual reproduction
Larva/ Asexual reproduction
Host
1-Definitive or final host
2-Intermediate host
Larva
Adult
Egg
Transfer or paratenic host

6. Medical Parasitology Host specificity Host: Reservoir host
Incidental host
Zoonosis
Transmission :
Direct contact
Indirect contact
Vector (carrier): often an arthropod,
Biological V.
Mechanical V.

7. Medical Parasitology Medical Parasites: Protozoa Helminthes:
Nematodes(Roundworms)
Trematodes(flukes)
Cestodes(tapeworms)
Arthropoda
Platyhelminthes
Ectoparasites
Endoparasites

8. Classification
Kingdom (Animal) Phylum (Platyhelminthes) Class (Trematoda) Order (Digenea) Family (Schistosomidae) Genus (Schistosoma) Species (heamatobium)

9. Binomial nomenclature
The scientific naming of species whereby each species receives a Latin or Latinized name of two parts, the first indicating the genus and the second being the species. the genus (capitalized) and species (lowercase) names, both written in italics. For example: Sarcocyctis bovis, Leishmania donovani,

10. Nematodes

11. Parasitic nematodes Life cycle: Cylindrical,
Adults
egg L1 L2
molting
Life cycle:
Cylindrical,
Complete digestive system,
Male < Female
Large (parsites)
Long life

12. Ascaris lumbricoides
Ascariasis

13. Ascaris lumbricoides: like Lumbricus
Female: 20-35cm, Male: 10-20

15. Anterior end of Ascaris lumbricoides showing mouth, esophagus, and intestine.

18. Importance
Worldwide
Very common parasitic worm in human: 1/6 of world population
Tropical and subtropical,
poverty

19. worms

20. Adult worms live in the lumen of the small intestine
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 feces .  Unfertilized eggs may be ingested but are not infective.  Fertile eggs embryonate and become infective after 18 days to several weeks , depending on the environmental conditions (optimum: moist, warm, shaded soil).  After infective eggs are swallowed , the larvae hatch , invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed .  Upon reaching the small intestine, they develop into adult worms .  Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female.  Adult worms can live 1 to 2 years.

21. Fertilized eggs oval to round , albumin thick outer shell
Unfertilized eggs
Need wet warm soil
Resistant to cold weather
Resistant to acids and alkalis as well as other chemicals

23. Small intestine: Ascaris larva emerging from egg

25. Ascariasis
Infection or disease?
Number of worms

26. Ascariasis: Symptoms and signs
1- Migrating larvae: allergic and respiratory symptoms (Loffler syndrome):
Cough
Sever hemorrhagic pneumonia
allergic hypersensitivity reactions(parasite proteins are allergenic):
Asthmatic attacks.
Pulmonary infiltration.
Urticaria .
Edema of the lips.
Eosinophilia

27. Ascariasis: Symptoms and signs
2- Adult parasites in the intestine:
A vague abdominal discomfort.
Nausea.
Colic
Lactose
Malnutrition
Intestinal obstraction

29. Ascariasis: Symptoms and signs
Adult worms outside of the intestine (wandering worms: High infection, Only male / Fever, Drugs) :
carry intestinal bacteria to these sites
Bile duct: jaundice, hepatitis
Appendix and peritonea: appendicitis, peritonitis
Migrate forward through the intestinal tract: vomited up or emerging through the nose.

31. Diagnosis Treatment Stool Examination: appearance of the eggs in feces
Albendazole : single dose 400 mg/ 200 mg under 2 years
Mebendazole: 100mg Bid x3 days
Ivermectin
pyrantel pamoate: single dose

33. Biliary ascariasis

34. Transmission Children 5-9 years old poor sanitation (sewage disposal)
places where human feces are used as fertilizer
poor personal hygiene
consuming contaminated vegetables or fruits

36. Control Effective sewage disposal systems.
Wash, peel, or cook all raw vegetables and fruits grown in soil
Periodic treatment

37. Enterobius vermicularis Pinworm, Oxyur
Enterobiasis

39. Enterobius vermicularis
World wide distribution
The most prevalent worm in USA and Western Europe
Incidense: 11.4% among people of all ages in USA
Most in School-age children (30-60%)
Not associated with social class, or culture

40. Enterobius vermicularis
Female:
about 1 cm
sharply pointed tail
Male:
About 0.5 cm
curved tail

42. Enterobius eggs Contains developing embryo or a larva Colorless
Adheres to environmental objects
Enterobius eggs

43. remain active up to three weeks
Infective in 4-6 h
remain active up to three weeks 11

44. Clinical manifestations
No symptoms in most people
Anal itching in children
Restless sleep
Itching and vaginal discharge in girls
Irritated or infected skin around the anus

45. Diagnosis Treatment Tape test (Scotch ) Mebendazole Albendazole
transparent adhesive tape
Done in the morning, before defecation and washing
Adult worms in perianal skin
Mebendazole
Albendazole
pyrantel pamoate
single dose
entire household be treated
repeated after 2 weeks

46. Control
Eggs can be transferred from fingers to clothing, bedding, towels, toilets, and other objects in the environment.
Spread by children to schoolmates or family members.
Dust containing eggs can become airborne
personal hygiene.
laundering of bedding

47. Finger sucking and nail biting
close contact
Finger sucking and nail biting
Autoinfection(infection from the original host to itself):
anus-to-mouth rout
retroinfection,(larvae may hatch on the anal mucosa, and migrate up the bowel)

48. THE END