Besnoitia neotomofelisn. sp. (Protozoa: Apicomplexa) from the southern plains woodrat (Neotoma micropus)

Abstract

SUMMARYCertain species of the protozoan genusBesnoitiacause clinical disease in livestock and wildlife. In the present paper a new species,Besnoitia neotomofelisis 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 isolateToxoplasma gondii. Initially, the organism was misdiagnosed asT. gondiibecause it was highly pathogenic for mice and its tachyzoites resembledT. gondiitachyzoites. Further studies revealed that it differed structurally and biologically fromT. gondii.Tachyzoites were successfully cultivated and maintainedin vitroin bovine monocytes and African green monkey kidney cells, andin vivoin mice. Non-dividing, uninucleate tachyzoites were approximately 1×5μm in size. Longitudinally-cut bradyzoites in tissue sections measured 1·5–1·6×7·7–9·3μm. Tissue cysts were microscopic, up to 210μm long, and were infective orally to mice. Cats fed tissue cysts shed unsporulated 13×14μm sized oocysts. All mice inoculated withB. neotomofelisdied 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 40×50μm) first-generation schizonts developed in the lamina propria of the small intestine of cats. A second generation of small sized (8μm) 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 thatB. neotomofeliswas related to otherBesnoitiaspecies from rodents, rabbits, and opossums.Besnoitia neotomofelisis distinct from the 3 other species ofBesnoitia, B. wallacei, B. darlingiandB. oryctofelisithat utilize cats as a definitive host.