Blood and Lymphatic Parasites

Blood and lymphatic parasites are those that inhabit the host circulatory system and could be transmitted to another host through blood (blood transfusion, sharing needles, organ transplant, and tissue graft). Most but not all of these parasites are transmitted through vectors. Blood-borne parasites are found worldwide, causing thousands of deaths annually, especially in developing countries. Blood parasites could cause the following: hepatosplenomegaly seen during infection with Trypanosoma, Leishmania donovani, Toxoplasma, Plasmodium, Babesia, and filarial worms; brain edema, coma, and meningoencephalitis produced by Plasmodium and Trypanosoma; bone marrow depression caused by Trypanosoma and Leishmania donovani; and lymphangitis and lymphadenitis (lymphatic filariasis) caused by Wuchereria bancrofti, Brugia malayi, and Brugia timori. Meanwhile, leukopenia and anemia are manifested during infection with Plasmodium, Babesia, Trypanosoma, and Leishmania donovani, in addition to the general symptoms and signs of infection (fever, malaise, headache, muscle ache, loss of appetite) caused by most blood-borne parasites during their acute stage of infection. Parasites affecting the blood and lymphatics could be one of the following: parasites that spend most or all of their life cycle in the bloodstream, e.g., Plasmodium and Babesia; parasites inhabiting other body organs and migrating through the blood, e.g., Trypanosoma, Leishmania donovani, and Toxoplasma; or parasites inhabiting lymphatic vessels and organs, e.g., Wuchereria bancrofti, Brugia malayi, and Brugia timori, in addition to the non-blood-borne parasites producing changes of the blood picture of the host, e.g., hookworms (A. duodenale and N. americanus), Schistosoma, Fasciola, and Trichuris trichiura.