Parasite Sarcocystis Research Articles

Plastid segregation and cell division in the apicomplexan parasiteSarcocystis neurona

Apicomplexan parasites harbor a secondary plastid that is essential to their survival. Several metabolic pathways confined to this organelle have emerged as promising parasite-specific drug targets. The maintenance of the organelle and its genome is an equally valuable target. We have studied the replication and segregation of this important organelle using the parasite Sarcocystis neurona as a cell biological model. This model system makes it possible to differentiate and dissect organellar growth, fission and segregation over time, because of the parasite's peculiar mode of cell division. S. neurona undergoes five cycles of chromosomal replication without nuclear division, thus yielding a cell with a 32N nucleus. This nucleus undergoes a sixth replication cycle concurrent with nuclear division and cell budding to give rise to 64 haploid daughter cells. Interestingly, intranuclear spindles persist throughout the cell cycle, thereby providing a potential mechanism to organize chromosomes and organelles in an organism that undergoes dramatic changes in ploidy. The development of the plastid mirrors that of the nucleus, a continuous organelle, which grows throughout the parasite's development and shows association with all centrosomes. Pharmacological ablation of the parasite's multiple spindles demonstrates their essential role in the organization and faithful segregation of the plastid. By using several molecular markers we have timed organelle fission to the last replication cycle and tied it to daughter cell budding. Finally, plastids were labeled by fluorescent protein expression using a newly developed S. neurona transfection system. With these transgenic parasites we have tested our model in living cells employing laser bleaching experiments.

Diagnosis of human sarcocystis infection from biopsies of the skeletal muscle

Sarcocystis is an uncommon parasitic infection. We report four cases that presented with lumps, pain in the limbs or a discharging sinus of unknown etiology. Microscopic examination of the excised tissue in all cases showed characteristic cysts of the sarcocystis parasite. A discussion of the identification and recognition of this uncommon infection from muscle biopsies is given.

The Frequency of Sarcocystis spp. and Its Effect on Winter Carcass Composition of Mottled Ducks

Macrocysts of the protozoan parasite Sarcocystis spp. occurred in 34 of 241 (14%) adult and 6 of 70 (8.6%) immature mottled ducks (Anas fulvigula) that were collected in southwestern Louisiana from 1987 to 1989. The prevalence of Sarcocystis spp. among immature ducks was higher than previously reported, possibly because of a longer exposure period. No differences in carcass composition variables were found between heavily infected and uninfected adult mottled ducks during the winter period of the annual cycle. We concluded that macrocysts of Sarcocystis spp. did not influence carcass composition and probably exert negligible effects on survival of parasitized mottled ducks during winter.

Immunohistochemical Diagnosis of Protozoan Parasites in Lesions of Equine Protozoal Myeloencephalitis

asite also differed structurally from Caryospora sp. because gamonts were not found and schizonts and merozoites were much larger than those of Caryospora sp. In structure, the parasite in the present case resembles the Sarcocystis parasite that causes fatal encephalomyelitis in horses, cattle, and sheep. Although the central nervous system in the infected dog was not examined, its litter-mate died of protozoan encephalomyelitis. 4 Acknowledgements. We thank John Jenkins and Eva Kovats for technical assistance. Montana State University, Agricultural Experiment Station Journal series No. 525847.

Asymptomatic Salmonellosis in Healthy Adult Horses

onts were seen in the brain and were not associated with parasite in the present case resembles a Sarcocystis parasite inflammation. that causes fatal encephalomyelitis in horses, cattle, and Although the diagnosis was initially mistaken as toxosheep. plasmosis, the parasite in the present study is definitely not either T. gondii or N. caninum because T. gondii and N. References caninum divide by endodyogeny, whereas in the present 1. case, the parasite divided by schizogony. In endodyogeny, Dubey JP, Beattie CP: 1988, Toxoplasmosis of animals and man. CRC Press, Boca Raton, Florida. 220 pp. the parasite divides into 2, and there is no multinucleated 2. Dubey JP, Carpenter JL, Speer CA, et al.: 1988, Newly recogstage. Examination for bacteria, and rabies and distemper nized fatal protozoan disease of dogs. J Am Vet Med Assoc 192: viruses were negative. 1269-1285. Both tachyzoites and tissue cysts of T. gondii and N. ca3. Dubey JP, Speer CA, Fayer R: 1989, Sarcocystosis of animals ninum are distinct from the parasite found in the present and man. CRC Press, Boca Raton, Florida. 215 pp. case. Tissue cysts of T. gondii and N. caninum contain PAS4. Lindsay DS, Dubey JP: 1989, Immunohistochemical diagnosis positive bradyzoites enclosed in a well-defined cyst wall. No of Neospora caninum in tissue sections. Am J Vet Res 50:198lsuch stage was found in the present case. In structure, the 1983.

Effects of the Protozoan Parasite Sarcocystis rauschorum on Open-Field Behaviour of Its Intermediate Vertebrate Host, Dicrostonyx richardsoni

Behaviour and activity levels were measured in varying lemmings experimentally infected with the heteroxenous parasite, Sarcocystis rauschorum to test the hypothesis that the parasite alters behaviour of this intermediate host and thereby increases probability of transmission to the definitive host, the snowy owl (Nyctea scandiaca). Measures of short-term activity levels on a running wheel indicated no effect of the parasite, either directly, or indirectly as a result of illness. We observed behaviour of infected lemmings placed in an "open field" (arena). Lemmings would increase their susceptibility to predators if they spent more time away from cover, used crypsis (stationary postures) less, spent more time exploring (especially in unfamiliar areas), or responded inappropriately to threats from predators. We found that only exploratory activity showed significant change after infection. The frequency of exploratory activity increased and became disassociated from the usual fear response. This may increase the lemmings' susceptibility to aerial predation. The mechanism for this effect is unknown, but neurological lesions have been observed. The examination of the modes of transmission of the S. rauschorum parasite within lemming populations and of a possible fecundity compensation strategy adopted by the lemmings, and their relevance to population control, are suggested as areas for future study.

Granulomatous Myositis in Association with Sarcocystis sp. Infection in Wild Ducks

Macroscopic cysts of species of the parasite Sarcocystis were found in 18 of 205 wild ducks of 11 species examined histologically, and microscopic cysts were found in nine of the 205. Focal granulomatous myositis was present in two of the 18 birds with macroscopic cysts. A progression of changes was evident, beginning with degeneration of the cyst wall and ending with granuloma formation. The inflammation appeared to occur in response to degeneration of the cysts.

Sarcocystosis: A Clinical Outbreak in Dairy Calves

Death and illness in a pen of eight yearling dairy heifers was caused by the protozoan parasite Sarcocystis. All animals had weight loss, weakness, marginal anemia, and elevated serum enzymes. Affected animals had high hemagglutinating antibody titers to Sarcocystis antigen. Affected tissues of the two animals that died demonstrated schizonits and young cysts during pathologic examination. The resident farm dog was shedding Sarcocystis sporocysts and was incriminated as the source of infection.

The Occurrence of the Parasite Sarcocystis in Mexican Birds

The Occurrence of the Parasite Sarcocystis in Mexican Birds