Further evidence of the host plasticity of porcine circovirus-2: detection of the virus in domestic dogs in Namibia

Porcine circovirus 2 (PCV-2) is a major pathogen of swine, causing significant production losses in the pig industry worldwide. Several studies have detected the virus in different species, both in asymptomatic and diseased subjects, highlighting PCV-2 host plasticity. As PCV-2 has been identified in carnivores, the present study was undertaken to investigate the susceptibility of domestic dogs to PCV-2 infection by testing archived blood samples originating from low-income rural areas in Namibia. The population was selected considering the high exposure probability to PCV-2 due to direct contact and/or feeding with raw pig meat or by-products. Thirty-eight of the samples (6.61%) tested positive for PCV-2, and the complete ORF2 of 7 strains was sequenced, revealing the presence of the three major PCV-2 genotypes (i.e. PCV-2a, -2b, and -2d). Convincing epidemiological links with other Namibian and South African strains were established for PCV-2a and PCV-2b strains, while the PCV-2d strains were part of a broader clade that included sequences of viruses collected worldwide, especially in Asia. Although PCV-2 was reported in diseased dogs, no statistically significant or robust causal association between infection and disease manifestation was demonstrated. In conclusion, PCV-2 infection has been identified in Namibian dogs, most likely due to the ingestion of contaminated meat and by-products. However, the epidemiological and clinical consequences are still unclear and further investigations are necessary. Nevertheless, the high proportion of infected dogs showing clinical signs raises concern about the potential of PCV-2's role as a relevant viral pathogen in Namibia. The use of raw meat for dog nutrition should be discouraged, considering the known risks to animal and human health through disease transmission.