Introduction to Parasitology

By Sh. Ghaffari

September 2012

Parasitology: definition Parasitology: study of parasites Animals:

Free-living Symbiotic

Symbiosis

Phoresis(to carry)

Commensalism(eating at the same table)

Mutualismpositive reciprocal relationship

ParasitismMetabolic

dependence

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:1. Animals2. Different species

Medical Parasitology

Life cycle1.Direct life cycle2.Indirect life cycle Parasite

Adult form/ Sexual reproduction

Larva/ Asexual reproduction

Larva

Adult

Egg

Transfer or paratenic

host

Medical Parasitology Host specificity

Host:1. Reservoir host 2. Incidental host

Zoonosis

Transmission : Direct contact Indirect contact Vector (carrier): often an arthropod,

1. Biological V.2. Mechanical V.

Medical ParasitologyMedical Parasites:1. Protozoa

2. Helminthes:1. Nematodes(Roundworms)2. Trematodes(flukes)3. Cestodes(tapeworms)

3. ArthropodaEctoparasitesEndoparasites

Platyhelminthes

Classification

Kingdom (Animal)

Phylum (Platyhelminthes)

Class (Trematoda)

Order (Digenea)

Family (Schistosomidae)

Genus (Schistosoma)

Species (heamatobium)

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,

Nematodes

Parasitic nematodes

Life cycle:

Cylindrical, Complete

digestive system,

Male < Female Large (parsites) Long life

L3

L4

Adultsegg

L1

L2

molting

molting

molting

Ascaris lumbricoides

Ascariasis

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

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

Importance

Worldwide Very common parasitic worm in human: 1/6 of

world population Tropical and subtropical, poverty

worms

Need wet warm soil Resistant to cold weather Resistant to acids and alkalis

as well as other chemicals

Fertilized eggs oval to round , albumin thick outer shell

Unfertilized eggs

Small intestine: Ascaris larva emerging from egg

Ascariasis

Infection or disease?

Number of worms

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

Ascariasis: Symptoms and signs

2- Adult parasites in the intestine: A vague abdominal discomfort. Nausea. Colic Lactose Malnutrition Intestinal obstraction

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.

Diagnosis Stool Examination: appearance of the eggs in

feces

Treatment Albendazole : single dose 400 mg/ 200 mg under 2

years Mebendazole: 100mg Bid x3 days Ivermectin pyrantel pamoate: single dose

Biliary ascariasis

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

Control

Effective sewage disposal systems. Wash, peel, or cook all raw vegetables and

fruits grown in soil Periodic treatment

Enterobius vermicularis Pinworm, Oxyur

Enterobiasis

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

Enterobius vermicularis Female:

about 1 cm sharply pointed tail

Male: About 0.5 cm curved tail

http://www.wikihow.com/Image:Enterobius-vermicularis-LifeCycle-306.gif

Contains developing embryo or a larva Colorless Adheres to environmental objects

Enterobius eggs

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

11

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

Diagnosis Treatment

Tape test (Scotch ) 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

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

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)

THE END