Molecular detection and genome characterization of porcine circovirus type 2 in rats captured on commercial swine farms

Abstract

Porcine circovirus type 2 (PCV2) is considered the major etiological pathogen of porcine circovirus-associated diseases (PCVADs) in pigs. Recently, PCV2 was also found in non-porcine animals such as cattle, rats, and mice. However, there was no record of PCV2 in rats in China. The goal of this study was to investigate whether PCV2 was present in rats (Rattus norvegicus, RN) on three swine farms, using molecular tools. PCR results showed that 30 of 95 (31.6 %) rat samples were positive for PCV2. Moreover, further genotype analysis suggested that 10 of 30 (33.3 %) were positive for PCV2a, 19 of 30 (63.3 %) were positive for PCV2b, and only one sample (1/30, 3.33 %) was co-infected by PCV2a and PCV2b. To determine the possible origin of PCV2, 60 serum samples were also collected from weaned pigs on those swine farms, and 23 out of 60 samples were positive for PCV2. In addition, two distinct RN-origin and two distinct porcine-origin PCV2 full-length nucleotide sequences were obtained from the farms. Sequence and phylogenetic analysis indicated that they had the highest nucleotide similarity and closest genetic relationships to each other. In this study, we report the infection and genome characterization of PCV2 in rats and compare RN-origin and porcine-origin PCV2 sequences obtained from the same pig farm, revealing possible cross-species transmission of PCV2.

Reservoirs of Porcine Circoviruses: A Mini Review

“…In the study from Brazil, PCV2 antigen was identified in the spleen, lungs and kidneys of rodent species Mus musculus and Rattus rattus using immunohistochemistry assay (37). 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).…”

“…However, only a few studies have conformed PCV infection in field rodent samples. Since 2010, several research teams from Hungary, Brazil, Korea and China have provided molecular evidence of PCV2 in rodents circulating on swine farms (36)(37)(38)(39). In the study from Brazil, PCV2 antigen was identified in the spleen, lungs and kidneys of rodent species Mus musculus and Rattus rattus using immunohistochemistry assay (37).…”

Surveillance for respiratory and diarrheal pathogens at the human-pig interface in Sarawak, Malaysia

“…Sites where employees reported seeing rodents "daily", as opposed to "weekly", "rarely", or "never", were also more likely to have PCV2-positive results in humans. This is notable, as recent studies have shown molecular detection of PCV2 in rats and other rodents, suggesting cross-species transmission [36,37]. While a positive association with rodents was observed for PCV2, this finding was not consistent when aggregating the nasal wash viral positive results.…”

Reappearance of buffalo-origin-like porcine circovirus type 2 strains in swine herds in southern China

“…Possible cross-species transmission of PCV2 is reported in several previous studies [6], [8], [9], [10], [11], [12], [13], [14], which included pig–rodent transmission, pig–mink transmission, pig–human transmission and pig–insect transmission. In this study, we confirmed those buffalo-origin-like PCV2 strains in swine herds in southern China, which further supported the possible cross-species infection of PCV2 between buffalo and pig in this region.…”

“…Genetic analysis showed that they belonged to three different PCV2 genotypes [7]. During the epidemiological survey of 2016, we obtained two significantly different PCV2 sequences (designated GDAH16 and GDSE16) from lung samples of dead pigs with respiratory disease according to a previously described method [7], [8]. GDAH16 was 1768 nucleotides in length and had two major open reading fragments (ORFs).…”