African swine fever virus (Malta/78) in pigs

Abstract

African swine fever was produced in all members of a group of 17 pigs by exposure to donor pigs infected with the Malta/78 isolate of ASF virus. The first clinical sign was an increased rectal temperature to more than 40°C, first observed 3 to 5 days post-exposure (DPE) in 16 pigs. Fever persisted until death, with a duration of 2 to 10 days. The mortality rate in 15 pigs was 93·3 per cent; 7 died 7 to 18 DPE and 7 were killed in extremis 9 to 22 DPE. Loss of appetite and fever were invariable clinical signs and some pigs also had nasal bleeding, conjunctivitis, anaemia and (rarely) skin lesions and respiratory signs. The most frequent post mortem lesion was haemorrhage in the visceral lymph nodes. Other lesions included excess fluid in the abdominal cavity, petechial haemorrhages in the kidneys and purple discolouration of the spleen. Viraemia was first observed 1 day before the onset of fever and maximum titres of > 10 8 HAD 50 per ml occurred 4 to 7 DPE. Virus distribution was generalized by 1 day after the onset of fever.