Cystoisospora (Isospora) belli is a coccidian parasite of humans. It can cause serious digestive disorders involving infection of intestines, biliary tract and gallbladder, especially in those with depressed immunity. It has a direct fecal–oral transmission cycle. After ingestion of sporulated oocysts, the parasite multiplies asexually and sexually within host epithelial cells, resulting in unsporulated oocysts that are excreted in feces. The details of asexual and sexual stages are not known and certain inclusions in epithelial cells in biopsy samples have been erroneously identified recently as C. belli. Here, we provide details of developmental stages of C. belli in two patients, in duodenal biopsy of one and biliary epithelium of the other. Immature and mature asexual stages (schizonts/meronts) were seen in epithelial cells. The merozoites were seen singly, in pairs and in groups in single parasitophorous vacuole (pv) in host cytoplasm. Immature and mature meronts were seen together in the same pv; up to eight nuclei were seen in meronts that retained elongated crescent shape; round multinucleated schizonts, seen in other coccidians, were not found. Meronts were up to 25 µm long and contained up to ten merozoites that were 8–11 µm long. The merozoites and meronts contained PAS-positive granules. Microgamonts (male) contained up to 30 nuclei that were arranged at the periphery and had condensed chromatin; 1–3 PAS-positive, eosinophilic, residual bodies were left when microgametes were formed. The microgametes were 4 µm long and PAS-negative. All stages of macrogamonts, including oocysts were PAS-positive. The detailed description of the life cycle stages of C. belli reported here should facilitate in histopathologic diagnosis of this parasite.

Certain species of the protozoan genus Besnoitia cause clinical disease in livestock and wildlife. In the present paper a new species, Besnoitia neotomofelis is described from the southern planes woodrat (Neotoma micropus). The parasite was detected by bioassay of woodrat tissues in outbred Swiss Webster mice in an attempt to isolate Toxoplasma gondii. Initially, the organism was misdiagnosed as T. gondii because it was highly pathogenic for mice and its tachyzoites resembled T. gondii tachyzoites. Further studies revealed that it differed structurally and biologically from T. gondii. Tachyzoites were successfully cultivated and maintained in vitro in bovine monocytes and African green monkey kidney cells, and in vivo in mice. Non-dividing, uninucleate tachyzoites were approximately 1×5 μm in size. Longitudinally-cut bradyzoites in tissue sections measured 1·5–1·6×7·7–9·3 μm. Tissue cysts were microscopic, up to 210 μm long, and were infective orally to mice. Cats fed tissue cysts shed unsporulated 13×14 μm sized oocysts. All mice inoculated with B. neotomofelis died of acute besnoitiosis, irrespective of the dose, and Norwegian rats became infected but remained asymptomatic. Entero-epithelial stages (schizonts, gamonts) were found in cats fed tissue cysts. Large (up to 40×50 μm) first-generation schizonts developed in the lamina propria of the small intestine of cats. A second generation of small sized (8 μm) schizonts containing 4–8 merozoites was detected in enterocytes of the small intestine. Gamonts and oocysts were seen in goblet cells of the small intestinal epithelium. Tachyzoites were present in mesenteric lymph nodes of cats. Phylogenetic analysis indicated that B. neotomofelis was related to other Besnoitia species from rodents, rabbits, and opossums. Besnoitia neotomofelis is distinct from the 3 other species of Besnoitia, B. wallacei, B. darlingi and B. oryctofelisi that utilize cats as a definitive host.

A species of Besnoitia from naturally infected rabbits from Argentina was propagated experimentally in mice, gerbils, rabbits, cats, and cell cultures. Cats fed tissue cysts from rabbits shed oocysts with a prepatent period of nine to 13 days. Sporulated oocysts were infective to gerbils, rabbits, outbred Swiss Webster and interferon gamma gene knockout mice. Bradyzoites were infective orally to gerbils and cats. Tachyzoites were successfully cultivated and maintained in vitro in bovine monocytes and African green monkey kidney cells. Schizonts were seen in the lamina propria of the small intestine of cats fed tissue cysts; the largest ones measured 52×45 μm. Schizonts were also present in mesenteric lymph nodes, livers, and other extra-intestinal organs of cats fed tissue cysts. Oocysts were 10–14×10–13 μm in size. This rabbit-derived species of Besnoitia resembled B. darlingi of the North American opossum, Didelphis virginiana with an opossum-cat cycle, but it was not transmissible to D. virginiana, and B. darlingi of opossums was not transmissible to rabbits. Based on biological, serological, antigenic, and molecular differences between the rabbit and the opossum Besnoitia, a new name, B. oryctofelisi is proposed for the parasite from domestic rabbits from Argentina.

The North American opossum, Didelphis virginiana, is a definitive host for at least 3 species of Sarcocystis:S. falcatula Stiles 1983, S. neurona Dubey, Davis, Speer, Bowman, de Lahunta, Granstrom, Topper, Hamir, Cummings, Suter 1991, and S. speeri Dubey and Lindsay 1999. In order to identify species of Sarcocystis in the South American opossum, D. marsupialis, Sarcocystis sporocysts from the intestines of a naturally infected opossum (D. marsupialis) from Brazil were fed to 4 gamma-interferon knockout (KO) mice, a nude mouse, and 2 budgerigars (Melopsittacus undulatus). All 4 KO mice became ill and 1 died 42 days post-feeding (p.f.) of sporocysts, 1 was killed 44 days p.f. because of neurological signs, and 2 were killed 52 and 53 days p.f. because of abnormal gaits. Numerous sarcocysts were seen in the skeletal muscles of all 4 KO mice and they were structurally identical to S. speeri seen in KO mice fed sporocysts from D. virginiana from the United States and D. albiventris from Argentina. The nude mouse was killed 41 days p.f. because it appeared weak; schizonts were seen in sections of its liver and sarcocysts were seen in sections of skeletal muscles. Sarcocystis speeri was cultured in bovine turbinate cells inoculated with liver homogenate from this mouse. Sarcocystis neurona was not demonstrable in tissues of mice. The two budgerigars remained asymptomatic and S. falcatula was not found in their tissues when they were killed 29 days p.i. This is the first report of S. speeri from D. marsupialis.

The development of Sarcocystis falcatula merozoites in bovine turbinate (BT) cell cultures is described and compared with development of Sarcocystis neurona merozoites. Merozoites of S. falcatula entered BT cell cultures and increased in size until 3 days post-inoculation when the nucleus of some merozoites developed lobes. Developing schizonts present at 4 days contained a lobed nucleus or appeared multinucleate. A single mature schizont was observed 4 days p.i. Schizonts were numerous 5 and 6 days p.i. Merozoites were produced from blastophores on the schizont. S. neurona merozoites developed to mature schizonts by 3 days p.i. in BT cells and a residual body was often present. Transmission electron microscopy revealed that S. falcatula merozoites possessed more micronemes than did S. neurona merozoites. Our study demonstrates that S. falcatula and S. neurona are not the same parasite.

Examination of Giemsa stained smears made from the peripheral blood, liver and spleen of hand-caught lizards from West Pokot area showed the presence of seven out of the nine Plasmodium species of lizards which have been previously described in Africa. These species are redescribed using a set of biological characters and procedure which enabled a large quantity of each stage of any species to be studied, measured and compared. The utilization of these characters and procedure was a reaction to the multiple infections in individual lizards and a wide host range of each species among lizard species. The adoption of the criteria is recommended for future taxonomie work on lizard Plasmodia in Africa.

A key which brings together all the previously described species of lizard Plasmodia and the new species encountered in the present investigation is presented. The key is simplified so that it can be of use to epidemiologists and pathologists who may work on saurian malaria in Africa.

During investigations on the malaria parasites of lizards in the West Pokot district of Kenya, haemoproteids, haemogregarines, pirhemocyton-like and anaplasma-like organisms were found in the blood. Microscopic examination showed that some of these are new species and they are described in this paper. The new described species are Haemoproteus mungutii (haemoproteid), Karyolysus poleensis, Schellakia mabuyai (haemogregarines), Pirhemocyton kongelai, Haematractidium omogoi, Sauroplasma kachelibaensis (Pirhemocyton-like organisms), Eperythrozoon ngokai and Aegyptianella elgonensis (anaplasma-like organisms). K. poleensis and S. mabuyai are regarded as the first report of the genera in lizards in Africa while A. elgonensis is regarded as the first report of the genus Aegyptianella in lizards.

During investigations into the epidemiology of malaria of lizards in Kenya, Giemsa-stained smears made from the peripheral blood, liver and spleen of hand-caught lizards from West Pokot district were examined for the presence of Plasmodium species. Ten new species were found and described. These are Plasmodium sapaaensis, P. kyaii, P. kachelibaensis, P. icipeensis, P. gloriai, P. odhiamboi, P. bowiei, P. kaninii, P. kadogoi and P. adunyinkai.

P. sapaaensis was found to be related to P. mabuiae, P. kadogoi to P. rhadinurum, P. kaninii to P. minasense (s. Telford) and P. adunyinkai to P. maculilabre. P. kyaii and P. kachelibaensis have distinct characteristics which distinguish them from the Plasmodium species in the tropiduri group reported so far.

Four species i.e. P. icipeensis, P. odhiamboi, P. gloriai and P. bowiei, exhibited peculiar characteristics most especially their effect on the white cells. They were therefore constituted into the “Kenyan” group.