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Taxonomy of Helminths

Medically important Helminths

Medically important Protozoa

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 Diagnosing Medical Parasites: A Public Health Officers Guide to Assisting Laboratory and Medical Officers 

Medically Important Parasitic Diseases - Lifecycles

  WHO Training Manual on Diagnosis of Intestinal Parasites
  Medically important Helminths       
  Medically important Protozoa     

Many of the helminth parasites common to both animals and humans have an indirect life cycle that is interrupted in the laboratory environment and thus limits the zoonotic potential of these organisms. Laboratory housed primates are the most likely source of parasitic infection for animal handlers. Helminths are POTENTIALLY zoonotic in the laboratory environment, but they represent a significantly smaller problem than bacterial or viral diseases. Exceptions are those with a direct life cycle. In General: proper quarantine, surveillance and treatment to decrease endoparasitic burden, routine sanitation to eliminate parasitic ova before they can become infective, and education of personnel on standard hygiene practices are measures that can be taken to prevent transmission of these diseases.

Protozoa and Helminths

The medically important protozoa and helminths require the invasion of a suitable host to complete all or part of their life cycle. Such organisms are therefore termed parasites and medical parasitology is the study of protozoa and helminth infections of man. The exception are some free-living amoebae that normally live and replicate in the environment but under certain circumstances can infect man. They are not therefore parasites but are included here as examples of protozoa causing human disease.

Parasite infections affect millions of people world-wide afflicting considerable human suffering and economic hardship. Far from declining, many parasite infections are increasing throughout the world. The impact of Human Immunodeficiency Virus (HIV) and AIDS has seen the emergence of "new" opportunistic parasites as well as the increased prevalence of other recognized types. Climatic changes induced through global warming has aided the spread of many parasite diseases, while starvation and the breakdown in sanitation that accompanies war has seen the re-emergence of others. The appearance of drug resistance has also dramatically influenced the ability to treat and control many parasite diseases. In the United States and the United Kingdom parasite infections are relatively uncommon. However, outbreaks of cryptosporidiosis associated with drinking water supplies has been of major concern, and toxoplasmosis remains a serious infection for the fetus when acquired during pregnancy.

It is beyond the scope of this website to characterize all protozoal and helminth infections of man. For those of you wishing to obtain further information on these fascinating and largely unexplored microbes, many World Wide Web sites contain useful information as well as diagrams and picture images of the protozoa and helminths discussed below. Find them through key word searches using one of the several search engines available.