Differences in serologic responses to North American and European subtypes of PCV2 virus isolates

摘要

Porcine circovirus type 2 (PCV2) has been troubling swine producers throughout North America and Europe since the mid-1990s. The virus can cause numerous clinical signs and syndromes, most notably post-weaning multisystemic wasting syndrome (PMWS), PCVAD, and various dermal, respiratory, and reproductive conditions.1 Vertical transmission of the virus has been demonstrated in the field and may be associated with abortions, mummified fetuses, still births and weak born pigs, however, it is believed the main route of infection is via the fecal-oral route.1 PCV2 is a small circular, single-stranded DNA virus. Phylogenetic analyses have separated PCV2 into two subtypes: North American and European2, also known as PCV2a and PCV2b, respectively. Until asrecently 2004 in Canada and 2005 in the USA, only the North American strain had been reported in North America, although recent reports of the European strain have become more common and associated with high clinical mortality.2'3 In the past year, commercial vaccines against PCV2 have become available and widely adopted by producers. Vaccination has been demonstrated to be efficacious in preventing disease mortality; however, these commercial vaccines are all based on North American isolates. Questions continue to arise as to the epidemiology of PCV2b isolates and the ability of PCV2 vaccines to prevent the shed of PCV2b isolates.3