Abstract
Porcine circovirus 3 (PCV-3) has been suggested as a putative causal agent of swine reproductive disease. A number of different studies have pointed out this association, but there is still a lack of information regarding the normal rates of PCV-3 infection in farms with normal reproductive parameters. The objective of the present study was to assess the frequency of PCV-3 detection in primiparous and multiparous sows and in tissues from their respective fetuses from farms with average reproductive parameters. Sera from 57 primiparous and 64 multiparous sows from 3 different farms were collected at two time points. Brain and lung tissues from 49 mummies and 206 stillborn were collected at farrowing. Samples were tested by PCR, and when positive, quantified by quantitative PCR. Thirty-nine complete genomes were obtained and phylogenetically analyzed. All sera from multiparous sows were negative, while 19/57 (33.3%) primiparous sows were PCV-3 PCR positive. From the 255 tested fetuses, 86 (33.7%) had at least one tissue positive to PCV-3. The frequency of detection in fetuses from primiparous sows (73/91, 80.2%) was significantly higher than those from multiparous ones (13/164, 7.9%). It can be concluded that PCV-3 is able to cause intrauterine infections in absence of overt reproductive disorders.
Highlights
Porcine circoviruses (PCVs) are small DNA viruses and have four representatives, PCV-1, PCV-2, Porcine circovirus 3 (PCV-3), and tentatively, PCV-4
One was collected at sampling point 1 (S1) and 18 were collected at sampling point 2 (S2) (P-value = 0.001); the positive sample at S1 was negative at S2
In China, a study found a higher frequency of the PCV-3 genome in sera from sows with a reproductive failure history (39/85, 45.9%) compared to healthy ones (23/105, 21.9%) [15]
Summary
Porcine circoviruses (PCVs) are small DNA viruses and have four representatives, PCV-1, PCV-2, PCV-3, and tentatively, PCV-4. PCV-1 is known as non-pathogenic for pigs [1], while PCV-2 has been. Pathogens 2020, 9, 533 associated with several conditions known as porcine circovirus diseases (PCVDs) [2]. PCV-2 systemic disease (PCV-2-SD), PCV-2 reproductive disease (PCV-2-RD), porcine dermatitis and nephropathy syndrome (PDNS), and PCV-2 subclinical infection (PCV-2-SI) [2]. In 2015, PCV-3 was firstly described in sows displaying reproductive failure and PDNS [4], as well as in pigs with multisystemic inflammation [5]. PCV-4 is the newest tentative member of the Circoviridae family and was described in pigs displaying respiratory and digestive clinical signs as well as PDNS [9]. It is already known that PCV-1, PCV-2, and PCV-3 are ubiquitous pathogens [1,2,7], while PCV-4 has been only detected in China so far [9,10]
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