Trypanosomatids

TRYPANOSOMATIDS

The family Trypanosomatidae consists of two genera, Trypanosoma and Leishmania. These are important pathogens of humans and domestic animals and the diseases they cause constitute serious medical and economic problems. Because these protozoans have a requirement for haematin obtained from blood, they are called haemoflagellates. The life cycles of both genera involve insect and vertebrate hosts and have up to eight life cycle stages, which differ in the placement and origin of the flagellum. Trypanosomatids have a unique organelle called the kinetoplast. This appears to be a special part of the mitochondrion and is rich in DNA. Two types of DNA have been found in the kinetoplast: maxicircles that encode many mitochondrial enzymes, and minicircles, which serve a function in the process of RNA editing. Replication of trypanosomatids occurs by single or multiple fission, involving first the kinetoplast, then the nucleus, and finally the cytoplasm. There are four major diseases associated with this group: Chagas disease is caused by Trypanosoma cruzi; sleeping sickness (African trypanosomiasis) is associated with T. brucei; cutaneous and mucocutaneous leishmaniasis are caused by a range of species including Leishmania tropica, L. major, L. mexicana, L. amazonensis and L. braziliensis; and visceral leishmaniasis, which is also known as kalaazar, is typically caused by L. donovani.