Novel virus related to neurologic signs in cattle
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A recently discovered astrovirus has been connected with neurologic disease in infected cattle.
The virus was detected in four cattle that had lived in California and had unexplained neurologic signs.
“While this particular new virus is unlikely to pose a threat to human health or the food supply, the new findings are critically important because they provide researchers with a relatively simple diagnostic tool that can reassure both ranchers and consumers by ruling out bovine spongiform encephalopathy—mad cow disease—as the cause of neurologic symptoms when they appear in cattle,” according to an announcement from the University of California-Davis.
The effects of the virus are described in a scientific article, “Divergent astrovirus associated with neurologic disease in cattle” (Emerg Infect Dis 2013;19:1385-1392), which was published in September. The researchers are or were affiliated with the Blood Systems Research Institute in San Francisco; University of California in Davis and San Francisco; Bishop Veterinary Hospital in Bishop, Calif.; University of South Florida in St. Petersburg; and Stanford University.
The article abstract indicates the astrovirus first was discovered in a crossbred yearling steer with an acute onset of lateral recumbency that included opisthotonus and extensor rigidity. A retrospective analysis of 32 cattle that had died with encephalitis revealed three others that had also been infected with the astrovirus.
The astrovirus RNA was limited to the nervous system and was found in the cytoplasm of affected neurons of the spinal cord, brainstem, and cerebellum, the article states. All infected cattle had lesions of widespread neuronal necrosis, microgliosis, and perivascular cuffing.
The article indicates that tests for the astrovirus RNA could be used to more rapidly exclude bovine spongiform encephalopathy as the cause of neurologic disease.
The affected cattle were of various ages and breeds, but the article states: “Further research will be required to determine whether development of the neurologic signs seen here required other factors, including co-infections and/or a genetic or acquired immunodeficiency. PCR testing and genomic analysis of bovine fecal isolates also may provide information about the incidence and duration of virus shedding, which—as for other asymptomatic intestinal astrovirus infections—is expected to be short.”