Manual of basic techniques for a health laboratory - libdoc.who.int

4. Parasitology 1054.Parasitology4.1 IntroductionA parasite is an organism that lives in or on another living organism of a differentspecies. The organism from which the parasite takes its food is called the host. Aparasite such as a tick that lives on its host is called an ectoparasite. A parasite thatlives in its host, such as a hookworm or an amoeba, is called an endoparasite.Many diseases are caused by infection with parasites. They are an important causeof diarrhoea (see Table 4.1), which is a major health problem in developingcountries.If acute diarrhoea is caused by parasitic infection, this can be determined byexamination of a stool specimen.Table 4.1 Common causes of diarrhoeal diseaseType of causeInfectiousProtozoaBacteriaVirusesHelminthsNon-infectiousMalabsorption syndromesIntoxicationsInborn errors of metabolismMetabolic disordersSpecific causeAmoebaeGiardia spp.Balantidium coliIsospora belliCryptosporidium spp.Plasmodium spp.Salmonella spp.Shigella spp.Escherichia coliVibrio choleraeStaphylococcus spp.Campylobacter spp.RotavirusesFasciolopsis spp.Strongyloides stercoralisTrichuris trichiuraHymenolepis nanaHeterophyes heterophyesTropical sprueCrohn diseaseWhipple diseaseFood poisoningChemicalsDrugsCarbohydrate intoleranceGluten enteropathyAdrenal disease105