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°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 HAD 50 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 the 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.