Leishmania species cause leishmaniasis. The disease is spread by the bite of sandflies in which part of the organism's life cycle is completed. In man, the promastigotes from the bite of the sandfly become ingested by macrophages and multiply within them as amastigotes. Cutaneous
leishmaniasis occurs if the region of infection remains localized to the dermis as an open sore. In the Old World (Southern Europe, the Middle East, India, former USSR and parts of Africa) L. major, L. tropica, L. aethiopica and certain subtypes of L. infantum are responsible. In the New World (Mexico southwards and through South America) species responsible include L. braziliensis, L. mexicana and L. amazonensis. If the organism spreads, then mutocutaneous leishmaniasis can occur in which the nose, mouth and palate becomes destroyed. Infection with members of the L. donovani-L.infantum complex produce the systematic disease of visceral leishmaniasis often known as kala-azar that occurs with a global distribution seen in Old and New World leishmaniasis. The parasites multiply within the macrophages of the liver, spleen, bone marrow and other organs. Untreated, the disease is usually fatal. As with trypanosomiasis, leishmaniasis is a zoonosis as many mammals harbor the parasite.
Ciliates
These possess rows of cilia around the outside of the body that aid motility. The only member of this group known to infect man is Balantidium coli. This is a cyst forming parasite that is a commensal ("table-sharing" and meaning here a non-pathogenic parasite) of domestic and wild pigs. It does, however, cause severe diarrhea in humans.
Apicomplexa
This is a unique group because all members are parasitic. The group includes parasites causing malaria, cryptosporidiosis and toxoplasmosis. They lack any visible means of locomotion (most are intracellular) and have complex life cycles involving sexual and asexual reproduction.. The common feature of all members is the presence of an apical complex in one or more stages of the life cycle. Although the exact components of the apical complex varies among members, it contains enzymes used to penetrate host tissues.
Malaria. Plasmodium species cause malaria. The four principal species are P. falciparum, P. vivax, P. ovale and P. malariae. Malaria means "bad air" and dates from the time when the disease was thought to be spread from stagnant, foul smelling water. The disease is in fact transmitted by the female Anopheles mosquito that inhabits such environments. In the stomach of the female Anopheles male (micro-) and female (macro-) gametocytes fuse to form a zygote. This in turn forms a motile ookinete that penetrates the midgut wall and develops into an oocyst within which are many thousands of sporozoites. When mature, the sporozoites rupture the oocyst and penetrate the salivary glands. When the mosquito next feeds on man, the sporozoites are passed via the blood stream to infect parenchymal cells of the liver. Here they form pre-erythrocytic schizonts in which several thousand daughter cells, called merozoites. These merozoites enter red blood cells to start the asexual intraerythrocytic cycle and form new gametocytes. The asexual red cell stages are responsible for the pathological changes that occur in malaria (fever, chills, anemia, liver enlargement, encephalitis renal damage and death).
leishmaniasis occurs if the region of infection remains localized to the dermis as an open sore. In the Old World (Southern Europe, the Middle East, India, former USSR and parts of Africa) L. major, L. tropica, L. aethiopica and certain subtypes of L. infantum are responsible. In the New World (Mexico southwards and through South America) species responsible include L. braziliensis, L. mexicana and L. amazonensis. If the organism spreads, then mutocutaneous leishmaniasis can occur in which the nose, mouth and palate becomes destroyed. Infection with members of the L. donovani-L.infantum complex produce the systematic disease of visceral leishmaniasis often known as kala-azar that occurs with a global distribution seen in Old and New World leishmaniasis. The parasites multiply within the macrophages of the liver, spleen, bone marrow and other organs. Untreated, the disease is usually fatal. As with trypanosomiasis, leishmaniasis is a zoonosis as many mammals harbor the parasite.
Ciliates
These possess rows of cilia around the outside of the body that aid motility. The only member of this group known to infect man is Balantidium coli. This is a cyst forming parasite that is a commensal ("table-sharing" and meaning here a non-pathogenic parasite) of domestic and wild pigs. It does, however, cause severe diarrhea in humans.
Apicomplexa
This is a unique group because all members are parasitic. The group includes parasites causing malaria, cryptosporidiosis and toxoplasmosis. They lack any visible means of locomotion (most are intracellular) and have complex life cycles involving sexual and asexual reproduction.. The common feature of all members is the presence of an apical complex in one or more stages of the life cycle. Although the exact components of the apical complex varies among members, it contains enzymes used to penetrate host tissues.
Malaria. Plasmodium species cause malaria. The four principal species are P. falciparum, P. vivax, P. ovale and P. malariae. Malaria means "bad air" and dates from the time when the disease was thought to be spread from stagnant, foul smelling water. The disease is in fact transmitted by the female Anopheles mosquito that inhabits such environments. In the stomach of the female Anopheles male (micro-) and female (macro-) gametocytes fuse to form a zygote. This in turn forms a motile ookinete that penetrates the midgut wall and develops into an oocyst within which are many thousands of sporozoites. When mature, the sporozoites rupture the oocyst and penetrate the salivary glands. When the mosquito next feeds on man, the sporozoites are passed via the blood stream to infect parenchymal cells of the liver. Here they form pre-erythrocytic schizonts in which several thousand daughter cells, called merozoites. These merozoites enter red blood cells to start the asexual intraerythrocytic cycle and form new gametocytes. The asexual red cell stages are responsible for the pathological changes that occur in malaria (fever, chills, anemia, liver enlargement, encephalitis renal damage and death).
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