2Introduction to Parasitology By Sh. GhaffariSeptember 2012
3Parasitology: definition Parasitology: study of parasitesAnimals:Free-livingSymbioticSymbiosisPhoresis(to carry)Commensalism(eating at the same table)Mutualismpositive reciprocal relationshipParasitismMetabolic dependence
4ParasitismParasite (parasitos “para: beside; sitos: grain or food”)HostParasitism: a form of symbiosis in which one organism (parasite) benefits at the expense of another organism of different species (host).Must be:AnimalsDifferent species
5Life cycle 1.Direct life cycle 2.Indirect life cycle Medical ParasitologyLife cycle 1.Direct life cycle 2.Indirect life cycleParasiteAdult form/ Sexual reproductionLarva/ Asexual reproductionHost1-Definitive or final host2-Intermediate hostLarvaAdultEggTransfer or paratenic host
6Medical Parasitology Host specificity Host: Reservoir host Incidental hostZoonosisTransmission :Direct contactIndirect contactVector (carrier): often an arthropod,Biological V.Mechanical V.
7Medical Parasitology Medical Parasites: Protozoa Helminthes: Nematodes(Roundworms)Trematodes(flukes)Cestodes(tapeworms)ArthropodaPlatyhelminthesEctoparasitesEndoparasites
8ClassificationKingdom (Animal) Phylum (Platyhelminthes) Class (Trematoda) Order (Digenea) Family (Schistosomidae) Genus (Schistosoma) Species (heamatobium)
9Binomial 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,
20Adult 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.
21Fertilized eggs oval to round , albumin thick outer shell Unfertilized eggsNeed wet warm soilResistant to cold weatherResistant to acids and alkalis as well as other chemicals
29Ascariasis: Symptoms and signs Adult worms outside of the intestine (wandering worms: High infection, Only male / Fever, Drugs) :carry intestinal bacteria to these sitesBile duct: jaundice, hepatitisAppendix and peritonea: appendicitis, peritonitisMigrate forward through the intestinal tract: vomited up or emerging through the nose.
39Enterobius vermicularis World wide distributionThe most prevalent worm in USA and Western EuropeIncidense: 11.4% among people of all ages in USAMost in School-age children (30-60%)Not associated with social class, or culture
42Enterobius eggs Contains developing embryo or a larva Colorless Adheres to environmental objectsEnterobius eggs
43remain active up to three weeks Infective in 4-6 hremain active up to three weeks11
44Clinical manifestations No symptoms in most peopleAnal itching in childrenRestless sleepItching and vaginal discharge in girlsIrritated or infected skin around the anus
45Diagnosis Treatment Tape test (Scotch ) Mebendazole Albendazole transparent adhesive tapeDone in the morning, before defecation and washingAdult worms in perianal skinMebendazoleAlbendazolepyrantel pamoatesingle doseentire household be treatedrepeated after 2 weeks
46ControlEggs 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 airbornepersonal hygiene.laundering of bedding
47Finger sucking and nail biting close contactFinger sucking and nail bitingAutoinfection(infection from the original host to itself):anus-to-mouth routretroinfection,(larvae may hatch on the anal mucosa, and migrate up the bowel)