Euglenozoa

Map of Africa Showing the Epidemiological Status of Countries Considered Endemic for Human African Trypanosomiasis

Trypanosoma forms in blood smear from patient with African trypanosomiasis

Life cycle of Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, cause of African Sleeping SicknessDuring a blood meal on the mammalian host, an infected tsetse fly (genus Glossina) injects metacyclic trypomastigotes into skin tissue (trypomastigotes are the characteristic developmental stage that infects humans. The parasites enter the lymphatic system and pass into the bloodstream (1). Inside the host, they transform into bloodstream trypomastigotes (2), are carried to other sites throughout the body, reach other blood fluids (e.g., lymph, spinal fluid), and continue to replicate by binary fission (3). The entire life cycle of this parasite is represented by extracellular stages. The tsetse fly becomes infected with bloodstream trypomastigotes when taking a blood meal on an infected mammalian host (4,5). In the fly’s midgut, the parasites transform into procyclic trypomastigotes, multiply by binary fission (6), leave the midgut, and transform into epimastigotes (7). The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission (8). The cycle in the fly takes approximately 3 weeks. Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in animals. Wild game animals are the main reservoir of T. b. rhodesiense. The subspecies Trypanosoma brucei brucei infects domestic and wild animals but usually not humans (but see the phylogeographic analysis by Balmer et al. 2011, which concludes that the three "subspecies"of T. brucei are not actually genetically or historically distinct lineages).From Centers for Disease Control Parasites and Health website.

Life cycle of Leishmania protozoans, the cause of leishmaniasis in humansProtozoans in the family Leishmania are well known as the cause of leishmaniasis in humans. Leishmaniasis is transmitted by the bite of infected female phlebotomine sandflies (Psychodidae:Phlebotominae). The sandflies inject the infective stage (i.e., promastigotes) from their proboscis during blood meals (1). Promastigotes that reach the puncture wound are phagocytized by macrophages (2) and other types of mononuclear phagocytic cells. Progmastigotes transform in these cells into the tissue stage of the parasite (i.e., amastigotes) (3), which multiply by simple division and proceed to infect other mononuclear phagocytic cells (4). Parasite, host, and other factors affect whether the infection becomes symptomatic and whether cutaneous or visceral leishmaniasis results. Sandflies become infected by ingesting infected cells during blood meals (5,6). In sandflies, amastigotes transform into promastigotes, develop in the gut (7) (in the hindgut for leishmanial organisms in the Viannia subgenus; in the midgut for organisms in the Leishmania subgenus), and migrate to the proboscis (8).From Centers for Disease Control Parasites and Health website.

This 1962 photograph depicted a man’s extended left arm, the volar surface of which displayed a leishmanial lesion due to his leishmaniasis infection. Leishmaniasis is transmitted by the bite of female phlebotomine sandflies. The sandflies inject the infective stage, promastigotes, during blood meals. Promastigotes that reach the puncture wound are phagocytized by macrophages and transform into amastigotes. Amastigotes multiply in infected cells and affect different tissues, depending in part on the Leishmania species. This originates the clinical manifestations of leishmaniasis. Sandflies become infected during blood meals on an infected host when they ingest macrophages infected with amastigotes. In the sandfly's midgut, the parasites differentiate into promastigotes, which multiply and migrate to the proboscis.Created: 1962

This is an illustration of the life cycle of Leishmania spp., the causal agents of Leishmaniasis.Created: 2002

This micrograph revealed the presence of a number of leptomonad-staged, i.e. promastigote, Leishmania sp. protozoa.Leishmaniasis, a vector-borne disease that is transmitted by sandflies, and caused by these obligate intracellular protozoa, is a human leishmanial infections, which can result in 2 main forms, cutaneous leishmaniasis and visceral leishmaniasis (kala-azar). The forms depend upon the leishmanial species, geographic location, and immune response of the host.Cutaneous leishmaniasis is characterized by one or more cutaneous lesions on areas where sandflies have fed. Patients manifest one or more sores on their skin. The sores can change in size and appearance over time. They often end up looking somewhat like a volcano, with a raised edge and central crater. A scab covers some sores. The sores can be painless or painful. Some people have swollen glands near the sores (for example, in the armpit if the sores are on the arm or hand).Created: 1974

This micrograph revealed the presence of a number of leptomonad-staged, i.e. promastigote, Leishmania sp. protozoa.Leishmaniasis, a vector-borne disease that is transmitted by sandflies, and caused by these obligate intracellular protozoa, is a human leishmanial infections, which can result in 2 main forms, cutaneous leishmaniasis and visceral leishmaniasis (kala-azar). The forms depend upon the leishmanial species, geographic location, and immune response of the host.Cutaneous leishmaniasis is characterized by one or more cutaneous lesions on areas where sandflies have fed. Patients manifest one or more sores on their skin. The sores can change in size and appearance over time. They often end up looking somewhat like a volcano, with a raised edge and central crater. A scab covers some sores. The sores can be painless or painful. Some people have swollen glands near the sores (for example, in the armpit if the sores are on the arm or hand).Created: 1974

This micrograph revealed the presence of a number of leptomonad-staged, i.e. promastigote, Leishmania sp. protozoa.Leishmaniasis, a vector-borne disease that is transmitted by sandflies, and caused by these obligate intracellular protozoa, is a human leishmanial infections, which can result in 2 main forms, cutaneous leishmaniasis and visceral leishmaniasis (kala-azar). The forms depend upon the leishmanial species, geographic location, and immune response of the host.Cutaneous leishmaniasis is characterized by one or more cutaneous lesions on areas where sandflies have fed. Patients manifest one or more sores on their skin. The sores can change in size and appearance over time. They often end up looking somewhat like a volcano, with a raised edge and central crater. A scab covers some sores. The sores can be painless or painful. Some people have swollen glands near the sores (for example, in the armpit if the sores are on the arm or hand).Created: 1973

This Giemsa-stained photomicrograph revealed a Leishmania sp. protozoan, which had been taken from a smear of a suspected leishmanial lesion, and magnified 1125X.Geographic DistributionHuman leishmanial infections can result in 2 main forms of disease, cutaneous leishmaniasis and visceral leishmaniasis (kala-azar). The factors determining the form of disease include leishmanial species, geographic location, and immune response of the host. Cutaneous leishmaniasis is characterized by one or more cutaneous lesions on areas where sandflies have fed. Persons who have cutaneous leishmaniasis have one or more sores on their skin. The sores can change in size and appearance over time. They often end up looking somewhat like a volcano, with a raised edge and central crater. A scab covers some sores. The sores can be painless or painful. Some people have swollen glands near the sores (for example, in the armpit if the sores are on the arm or hand).Created: 1972

This Giemsa-stained photomicrograph revealed a Leishmania sp. protozoan, which had been taken from a smear of a suspected leishmanial lesion, and magnified 1125X.Human leishmanial infections can result in 2 main forms of disease, cutaneous leishmaniasis and visceral leishmaniasis (kala-azar). The factors determining the form of disease include leishmanial species, geographic location, and immune response of the host. Cutaneous leishmaniasis is characterized by one or more cutaneous lesions on areas where sandflies have fed. Persons who have cutaneous leishmaniasis have one or more sores on their skin. The sores can change in size and appearance over time. They often end up looking somewhat like a volcano, with a raised edge and central crater. A scab covers some sores. The sores can be painless or painful. Some people have swollen glands near the sores (for example, in the armpit if the sores are on the arm or hand).Created: 1972

This illustration depicts the life cycle of Trypanosoma cruzi, the causal agent of American Trypanosomiasis.Created: 2002