Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 22, 1999
Publication Date: N/A
Interpretive Summary: Neospora caninum is a single celled parasite of livestock and companion animals. It causes abortion in cattle and paralysis in companion animals. It's life cycle and sources of infection were not known until 1998 when the resistant stage of the parasite (oocyst) was found in the feces of dogs. Scientists at the Beltsville Agricultural Research Center and Virginia Tech, Blacksburg now provide full morphologic description of the Neospora oocyst. These results will be of interest to parasitologists, diagnosticians and pathologists.
Oocysts of Neospora caninum were collected from the faeces of a dog fed mouse brains containing tissue cysts of the NC-beef strain of N. caninum. Sporulated oocysts were spherical to subspherical and were 11.7 by 11.3 Am. The length/width ratio was 1.04. No micropyle or oocyst residuum was present. Polar granules were not present, although occasionally tiny refractile granules were seen among sporocysts. Sporocysts were ellipsoidal, did not contain a Stieda body, and were 8.4 x 6.1 gm. The length/width ratio for sporocysts was 1.37. A spherical or subspherical sporocyst residuum was present and was composed of a cluster of small, compact granules, 4.3 x 3.9 um or represented by many dispersed granules of similar size. Sporozoites were elongate and 7.0-8.0 x 2.0-3.0,um in situ. No refractile bodies were present and the nucleus was centrally or slightly posteriorly located. The features of the oocyst of Neospora caninum are similar to Hammondia heydorni oocysts from dog faeces and Toxoplasma gondi and H. hammondi oocysts from cat faeces.