Sarcocystis - Clinical: Non Human

Clinical: Non Human

Four recognised species infect cattle: S. bovifelis, S. bovihominis (S. hominis) S. cruzi (S. bovicanis) and S. hirsuta. S. cruzi is the only species known to be pathogenic in cattle. A number of clinical syndromes have been reported in connection with this parasite: eosinophilic myositis; abortions, stillbirths and deaths in pregnant cows; two cases of necrotic encephalitis in heifers have also been reported. Typical clinical signs of acute bovine sarcocystosis are: anorexia, pyrexia (42C or more), anemia, cachexia, enlarged palpable lymph nodes, excessive salivation and loss of hair at the tip of the tail.

Sheep may be infected by four recognized species of Sarcocystis: S. arieticanis and S. tenella (S. ovicanis) are pathogenic; S. gigantea (S. ovifelis) and S. medusiformis are non-pathogenic. Infection with these parasites is common in the US with over 80% of sheep examined showing evidence of infection. S. arieticanis and S. tenella both produce extra intestinal disease. Anemia, anorexia, ataxia, and abortions are the chief clinical signs. Myositis with flaccid paralysis has been reported as a consequence of infection. Ovine protozoan myeloencephalitis is a recognised syndrome that may occur in outbreaks. The usual pathological findings in such cases are multifocal spinal cord white matter oedema and necrosis, glial nodules and mild to moderate nonsuppurative encephalomyelitis. The diagnosis may be established finding protozoan bodies (12.7-23.0 micrometres) that stain immunocytochemically for Sarcocystis epitopes.

Four recognised species infect pigs: S. medusiformis, S. meischeriana (S. suicanis), S. porcifelis and S. suihominis. S. porcifelis is pathogenic for pigs causing diarrhea, myositis and lameness.

Five species infect horses: S. asinus, S. bertrami, S. equicanis, S. fayeri and S. neurona (S. falcatula). All utilize canids as definitive hosts: transplacental infection has also been reported. S. neurona causes equine protozoal myeloencephalitis. Exposure to this parasite appears to be common in the United States with serological surveys indicating that 50-60% percent of all horses in the Midwest United States have been exposed to it. Clinical signs include gait abnormalities including ataxia, knuckling and crossing over. Muscle atrophy, usually unilateral, may occur. The lesions are typically focal. Brain-stem involvement is common. Depression, weakness, head tilt and dysphagia also occur.

S. fayeri may cause myositis in horses.

Fatal infection of an alpaca (Lama pacos) with an unnamed species has been reported. Findings included disseminated eosinophilic myositis, abortion and haemoabdomen. The myositis was associated with hameorrhage, necrosis and degeration. Infection by S. tilopodi of muscle tissue in the Guanaco has been reported.

S. hemionilatrantis infects mule deer. Death from experimental inoculation have been reported.

These parasites can also infect birds producing three different clinical forms: an acute pulmonary disease, muscular disease and neurological disease. Symptoms include lethargy, shortness of breath, tail bobbing, yellow tinted droppings and sudden death.

The presence of the cysts in the muscle of wild birds is known as "rice breast".