HEAL ▶▶▶TH attention paid to this virus is enough.”

Is PCV3 causing pig health problems? As a link between PCV3 and reproductive failure seems likely, that topic has received attention in the CReSA-IRTA studies. One of the studies presented at ESPHM was carried out in co- operation with Zoetis, the São Paulo State University and the Universitat Autònoma de Barcelona. It zoomed in on the question of to what degree PCV3 could be vertically transmit- ted from sows to piglets. To that end they assessed the fre- quency of PCV3 in sera from gilts and sows from farms with- out reproductive problems, as well as in tissues of their respective stillborn piglets. Sera from 60 primiparous and 64 multiparous sows belonging to three different farms without reproductive problems were collected at two points in time: around mating and close to farrowing. In addition, the team tested tissues from 264 stillborn piglets from these sows, ei- ther from the brain or from the lungs. All sera from multiparous sows were PCV3 PCR negative, while 19 of the 60 (32%) primiparous sows tested positive for PCV3 at either of the two sampling points. From the 264 stillborns, 90 (34%) had at least one tissue positive to PCV3.

PCV3 was also found in lymph nodes, as can be seen in this microscopic image.

Primiparous vs multiparous sows The team wrote: “The rate of detection of the virus in still- borns from primiparous sows (77/98, or 79%) was significant- ly higher than that from multiparous sows (13/166, or 8%).” In addition, they reported, the percentage of lungs being PCV3 PCR positive was higher (84/258, or 33%), than that of the brain (68/261, 26%). The researchers concluded, “PCV3 DNA was detected only in sera from primiparous but not from multiparous sows of the

studied herds. The prevalence of PCV3 in both tissues was sig- nificantly higher in stillborns from primiparous than from multiparous sows. Overall, these results indicated that PCV3 can be vertically transmitted causing intrauterine infections in absence of reproductive problems in the farm.”

PCV3 found in lesions of young pigs Having established the infection rate in cases without repro- ductive problems, the CReSA-IRTA team zoomed in deeper on farms with reproductive failure, in a different study in cooperation with animal health company Hipra. The team investigated 53 cases of foetuses and stillborn pig- lets from Spanish farms. Apart from PCV3, the team also checked for presence of, for example, Porcine Reproductive and Respiratory Syndrome virus (PRRSv) and PCV2. In 18 out of 53 cases (34%), PCV3 was detected. The main labelled cells were smooth muscle cells of arterioles from different tissues such as heart, kidney and spleen; macrophage-like cells in lung and kidney were also labelled. The team found mild arteritis and peri-arteritis in multiple tissues of the positive cases. Of this trial, the researchers wrote: “Since the simple viral detection of an endemic virus does not imply the causality of the clinical condition, detection of PCV3 within lesions provides a stronger evidence of putative association between the presence of the virus and the clinical outcome.”

Arthrogryposis and pre-weaning disease Other papers published at ESPHM investigated further poten- tial implications of PCV3 infection. Would there for instance also be a link between the virus and stillborn and pre-weaned pigs with nervous disease? To that end, the CReSA-IRTA team cooperated with the Animal and Plant Health Agency (APHA) in the United Kingdom. The outcome there was that “detection of high amount of PCV3 in tissues in stillbirths with arthrogryposis and in pre- weaning piglets with nervous disease and multisystemic in- flammation provides good evidence of its likely causal associa- tion with disease on two breeding herds.” The team added that these cases were believed to be the first such report in Europe.

Does PCV3 occur in pork meat? In another trial by CReSA-IRTA in combination with Zoetis, the question researched was whether DNA for PCV3 was found in both fresh and processed pork products. The answer was “yes” in both cases – PCV3 was found in 20 out of 30 samples (67%). Remarkably, the team found the virus on all fresh pork prod- ucts: “All non-processed samples (loin and sausages) were pos- itive for PCV3 and contained the highest viral load.” They wrote: “Since the percentage of samples from non-pro- cessed meat was higher than from processed, it is likely that curation procedures may exert an effect on PCV3 genome in- tegrity… Overall, these data likely reflect the ubiquity of PCV3 in the swine industry.” Dr Sibila and Dr Segalés added that this

16 ▶ PIG PROGRESS | Volume 37, No. 7, 2021

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