Infection of pigs with the Cameroon isolate (Cam/82) of African swine fever virus

Abstract

African swine fever (ASF) was produced in eight pigs by exposure to donors infected with the Cameroon/82 isolate of African swine fever virus. The primary clinical sign was pyrexia of more than 40 degrees C first observed 10 to 13 days post-exposure (dpe) in all pigs; other clinical signs were rarely observed. The most frequent post-mortem lesion was haemorrhage in the visceral lymph nodes. Other lesions included excess fluid in the abdominal cavity and petechial haemorrhages in the kidneys. Viraemia was first observed 1 to 2 days before the onset of pyrexia and maximal titres of more than 10(7.5) HAD50 per ml occurred 11 to 14 dpe. Virus excretion by the pharyngeal route was observed at 2 to 4 days before the onset of pyrexia and continued throughout the course of infection. Susceptible pigs, mixed directly with infected ones, contracted infection within 2 h; transmission time increased to 2 to 6 h when recipient pigs were separated by wire mesh from the infected pigs. The comparatively low mortality, ill-defined clinical signs and clinical recovery of many of the infected pigs show that the Cam/82 ASF virus is of relatively low virulence and thereby resembles recent European, South American and Caribbean isolates.