Detection and sequencing of porcine circovirus 3 in commercially sourced laboratory mice

Abstract

Porcine circovirus 3 ( PCV 3), a recently discovered virus, has spread widely in pigs throughout the world. In order to investigate the possibility of mice used to study the infection of PCV 3, commercially sourced Balb/C and ICR mice were screened for PCV 3 infection. Blood samples were collected from 20 mice (10 each of Balb/c and ICR ), DNA was extracted, and subjected to PCR with PCV 3 specific primers. We found all 20 serum samples tested positive for PCV 3 DNA . From four mice, the complete genomes of PCV 3 were amplified and sequenced, and a phylogenetic tree was constructed. The results showed that the amplified genome was 2000 bp, and sequence comparison showed that the homology of the complete genome and ORF 2 gene with those of porcine PCV 3 are 97.9%–98.8% and 96.9%–98.3%, respectively. Amino acids alignment results showed that the Cap protein of the mouse PCV 3 isolates share 90.7%–96.3% amino acid homology with that of the references strains derived from pigs. Phylogenetic analysis based on ORF 2 sequences showed that all PCV 3 strains clustered together and were clearly separate from other circovirus species. We detected PCV 3 in experimental mice in China for the first time, which is an opportunity to use mice to study the infection of PCV 3 and a potential hazard to swine industry.

Lack of Evidence on the Susceptibility of Ticks and Wild Rodent Species to PCV3 Infection

“…Accordingly, PCV3, similar to other PCVs, shows plasticity in host tropism and has also been reported in nonporcine species such as dogs, ruminants and mice [ 15 , 16 , 17 , 18 ]. Moreover, previous studies on PCV2 and PCV3 demonstrated that arthropods and rodents could also be involved in the spread of these viruses [ 11 , 19 , 20 ].…”

“…For instance, PCV2 was proven to infect mice in experimental conditions and also synanthropic rodents that lived close to swine farms, where they could have been infected due to the direct contact with positive swine [ 24 , 25 , 26 ]. To date, only one study has reported a considerable PCV3 prevalence in laboratory rodents, which neither had contact with swine populations nor were experimentally infected [ 16 ].…”

“…All this evidence is based on laboratory or synanthropic animals, likely exposed to a much higher infectious pressure, thus preventing any extension of these results to related wild species [ 16 , 19 , 24 ]. However, other authors have put emphasis on this potential part of the viral biological cycle and ecology based on our previous speculations [ 5 ].…”

Reservoirs of Porcine Circoviruses: A Mini Review

“…In addition, rodent-origin PCV2 genome sequences had remarkable similarity with gene sequences of PCV2 isolated from pigs (37,39). It is noteworthy that one recent study identified PCV3 in commercially sourced laboratory mice including BALB/c and ICR mice (40). This is in contrast with from the Hungarian study, which claims that rodents need certain contact with pigs, without which PCV2 is negative in rodents (36).…”

Genotyping Porcine Circovirus 3 (PCV-3) Nowadays: Does It Make Sense?

“…Besides domestic pigs, PCV-3 has been detected in other domestic species, including dogs [10,11], cattle [12], and mice [13], and wild species, including wild boars [14][15][16], chamois, roe deer, and associated ticks [15]. However, only wild boar seems to be infected at high prevalence and might play a significant role in PCV-3 epidemiology.…”