Spontaneous Frenkelia Infection in a Laboratory-Reared Rat
Abstract. Numerous, lobulated, thin-walled protozoan cysts were found in the brain and cervical spinal cord of a male Fischer rat with granulomatous encephalitis. The cysts were compartmented, 470-1000 pm in diameter, and packed with crescent-shaped organ-isms. Light- and electron-microscopic featur...
| Main Authors: | , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1000.3360 http://vet.sagepub.com/content/13/5/337.full.pdf |
| Summary: | Abstract. Numerous, lobulated, thin-walled protozoan cysts were found in the brain and cervical spinal cord of a male Fischer rat with granulomatous encephalitis. The cysts were compartmented, 470-1000 pm in diameter, and packed with crescent-shaped organ-isms. Light- and electron-microscopic features of the organism were characteristic of the protozoan Frenkelia, a parasite usually found in the brain of wild rodents. Many cysts were replaced by granulomas, whereas others elicited no inflammation. Perivascular and meningeal mononuclear cell infiltrates and gliosis were common. Protozoan parasites of the genus Frenkelia [2], previously called M-organism [5] and Toxoplasma microti [4], form compartmented thin-walled cysts up to lo00 pm in diameter in the brain of wild rodents. The cysts are macroscopic and may be seen as whitish bodies on the surface of the cerebral cortex [l, 71. In field voles and meadow mice (Microtus sp.), lemmings (Lemmus lemmus) and muskrats (Ondatra zibethica) the cysts are lobulated, but in all other hosts are rounded [14]. Signs of infection are usually absent even though cysts may involve up to 3.69, of the brain [3]. Significant encephalitis has not been described [4, 71. Attempts to artificially induce infection in mice, hamsters, guinea pigs, voles, and rabbits were unsuccessful or inconclusive [l, 4,5,14]. Recently, however, the life cycle of one Frenkelia sp. was described [lo]. Brains of bank voles (Clethrionomys glareolus) con-taining Frenkelia cysts were fed to a number of experimental hosts. One week after infection sporocysts appeared in the feces of the buzzards (Buteo buteo) only. When sporocysts isolated from buzzard feces were fed to bank voles, Frenkelia cysts occurred in the brain 7-10 weeks later. It was concluded that the sporocysts of Zsospora buteonis of B. buteo are developmental stages of Frenkelia sp. of the bank vole. |
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