Global Environmental Health: Parasitic Diseases

Parasitism is the relationship between one partner (the parasite) harms or lives on the expense of the other (the host). Parasites usually live in a very intimate relationship with their host not only depending on the host for nutrient, but also for a habitat. Parasites are a diverse set of eukaryotic pathogens such as protozoa, platyhelminthes (flatworms), nematodes (elongated worms with rigid cuticula), and arthropods (insects, ticks, and mites). Several diseases caused by parasites are found in the tropic (temperature climates), but the correlation is not with temperature it is with levels of sanitation and general public health (usually poor areas).

Parasitic Diseases

This is a list of predominant parasites that is a concern for each continent of the world. Continents are list alphabetically.

Disease (Causative agent= protozoal or helminthic)

Antarctica

Monogenea sp.

Africa

Malaria (Plasmodium falciparum)

Typanosomiasis (Trypanosoma brucei)

Schistosomiasis (Schistosoma haematobium, Schistosoma mansoni, and Schistosoma intercalatum )

Lymphatic filariasis (Wucheria bancrofti)

Onchocerciasis (Onchocerca volvulus)

Leishmaniasis (Leishmania spp.)

Asia

Malaria (Plasmodium falciparum)

Lymphatic filariasis (Brugia malayi)

Schistosomiasis (Schistosoma japonicum)

Leishmaniasis (Leishmania spp.)

Australia

Malaria (Plasmodium falciparum)

Lymphatic filariasis (Wucheria bancrofti)

Leishmaniasis (Leishmania spp.)

Europe

Lymphatic filariasis (Wucheria bancrofti)

Leishmaniasis (Leishmania spp.)

North America

Toxoplasmosis (Toxoplasma gondii)

Diarrhaeal diseases

Giardiasis (Giardia intestinalis)

Cryptosporidosis (Cryptospordium parvum)

Cyclosporiasis (Cyclospora cayetanensis)

South America

Chagas disease (Trypanosoma cruzi)

Malaria (Plasmodium falciparum)

Leishmaniasis (Leishmania spp.)

Schistosomiasis (Schistosoma mansoni)

Lymphatic filariasis (Wucheria bancrofti)

Onchocerciasis (Onchocerca volvulus)

Chagas Disease

Parasite: Trypanosoma cruzi

Distribution:

The disease is endemic in Latin America, most frequently in Argentina, Bolivia, Brazil, Chile, Uruguay, and Venezuela

20 million infected
40 million at risk
>50,000 deaths per year

Transmission:

Reduviid: It is transmitted naturally through the bite of the reduviid bug which defecated during feeding and parasites are eliminated with feces.

T. cruzi host-cell interaction:

Life Cycle:

Chagas Disease:

The parasite enters the cells at the initial site of entry. Transforms into amastigote and duplicates. The cell ruptures and release more parasites. The combination of the parasitized cells plus the inflammatory reaction of the host is responsible for the initial pathology observed.

Acute form:

7-10 days incubation period
Often in children: chagoma, Romaña sign, flu-like symptoms, myocarditis, encephalitis, lymphadenoathy, enlargement of liver and spleen