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Homogenous metacyclic promastigotes of Leishmania chagasi were isolated by buoyant density from in vitro heterogeneous cultures and used for biochemical characterization of isoforms of the major surface protease (MSP). Compared to stationary phase promastigotes, metacyclic cells had three times more MSP, produced 3-fold higher parasite loads in a mouse model in vivo, and were more resistant to complement-mediated lysis in vitro. These metacyclic L. chagasi expressed both the virulence-associated 59-kDa, and the constitutively expressed 63-kDa, isoforms of MSP.

Tritrichomonas foetus is a very intriguing trichomonad protozoan with respect to its varied choice of residence in the different host species. It is an obligate parasite of the reproductive and the gastrointestinal tract of bovine and feline host respectively, leading to trichomonosis. Bovine trichomonosis is a sexually transmitted disease whereas feline trichomonosis is a disease with a purported fecal-oral route of spread. Further, the trichomonad is a commensal in the nasal passages, stomach, cecum and colon of swine host. Advances have been exponential in understanding the trichomonad biology and specifically feline trichomonosis since late 1990s and early 2000s when T. foetus was soundly determined to be a causative agent of chronic diarrhea in the domestic cat. It is a challenging task, even for a skilled investigator not to mention the busy clinical veterinarian, to keep up with the vast volume of information. Here we comprehensively reviewed the trichomonad biology, clinical manifestations, pathogenesis, host immunity, world map of distribution, risk factors, diagnosis and treatment. Risk factors associated with T. foetus-positive status in the domestic cat include young age, purebred, history of diarrhea, co-infections with other enteral pathogens. In addition, molecular similarity of bovine and feline isolates of T. foetus in DNA sequence was concisely discussed. The data presented serve as an information source for veterinarians, and investigators who are interested in biology of T. foetus and feline trichomonosis.

Trypanosomatids are a very diverse group of protozoa including many species of medical, veterinary, and/or economical importance. Leishmania spp. cause disease on the continents of Asia, Africa, Europe, and North and South America; Trypanosoma cruzi is the etiology of Chagas' disease in South and Central America; and Trypanosoma brucei infections result in African sleeping sickness. Four genera of heteroxenous trypanosomatids transmitted by insect vectors infect a wide range of hosts including humans, animals, and plants. Six genera of monoxenous trypanosomatids parasitize numerous species of insects. Due to this diversity, the life cycle of Leishmania spp. is presented as a model to which other heteroxenous and monoxenous groups will be briefly contrasted.During their life cycle, Leishmania spp. shuttle between a flagellated promastigote stage in the sand fly vector and a nonmotile amastigote stage in a mammalian host. During blood meals on infected hosts, the sand fly vectors ingest amastigote-laden macrophages (Mø). These amastigotes transform to procyclic promastigotes in the sand fly gut, multiply by binary fission, and eventually develop into metacyclic promastigotes, the infective stage for mammalian hosts including humans. The sand fly vectors, upon taking another blood meal, inoculate the metacyclic promastigotes into the dermis, where they are phagocytized by Mø of the mammalian hosts. Amastigotes, transformed from metacyclic promastigotes, multiply in parasitophorous vacuoles (PV) of the host's Mø. Multiplication of amastigotes eventually leads to rupture of the infected Mø and release of amastigotes, which infect additional Mø, perpetuating the cycle of replication (38).Other , Crithidia, Leptomonas, Herpetomonas, Rhynchoidomonas, and Phytomonas (87). Leishmania spp. harbor a zinc metalloprotease, discovered in the mid-1980s, on their surfaces (14,15,36,37,88). This enzyme, accounting for about 1% of the total protein in promastigotes of Leishmania major and Leishmania mexicana (2, 10) and being potentially important during different stages of the life cycle, soon became the object of much investigation (8,70,71,107). Although referred to here as major surface protease (MSP), this zinc metalloprotease has also been termed GP63, surface acid protease, promastigote surface protease, EC 3.4.24.36, and leishmanolysin.MSPs of Leishmania spp. belong to the M8 family of endopeptidases, sharing several characteristics with mammalian matrix metalloproteases. Similarities include degradation of the extracellular matrix, cell surface localization, protease activity requiring Zn 2ϩ , and inhibition of protease activity by * Mailing address: