PCV3 infections in aborted fetuses; a case series of two
Sjoerd Klarenbeek1, Reinie Dijkman1, Emile Gijsen2, Chretien Gielen3, Rene Brunthaler4, Tijs Tobias1
1 Royal GD, Deventer, the Netherlands
2 VarkensArtsenZuid, Panningen, the Netherlands
3 De Varkenspraktijk, Oss, the Netherlands
4 Veterinärmedizinische Universität Wien, Vienna, Austria
Background and Introduction
Causal inference for Porcine Circo Virus type 3 (PCV3) to induce reproductive problems in sows is debated. Recently, in two cases for which diagnostics was requested, PCV3 was found as the sole probable cause for abortions and increased number of stillborn piglets and mummified fetus. This case series describes the clinical and diagnostic work up and aims to contribute to the scientific debate about the relevance and impact of PCV3 in swine.
Material and Methods
Case descriptions
Case 1: a 1,300 head multiplier farm with self-rearing of gilts reported an increased number of a terme born litters of gilts with higher numbers of mummified and still born pigs over an 8 week period.
Case 2: a 450 head multiplier farm experienced incidental late term abortions and premature farrowing (around day 108 post insemination) in ~10 gilts over a 3 week period. In both farms, besides anorexia, there was no evidence of respiratory or gastro-intestinal disease, nor of systemic disease in sows or gilts. In both farms, gilt rearing and housing was strictly separated from the sows and adaptation procedures before service was limited in time.
Methods
For both cases, two foetuses, and in case 2 also foetal membranes, were submitted for pathological and microbiological investigations. Routine PCR tests were run for Porcine Parvo Virus, PCV2 and Porcine Reproductive and Respiratory Syndrome virus (PRRSv). In addition, PCR for PCV3 as well as In Situ Hybridisation (ISH) for PCV3 was performed
Results
Case 1 and 2: No macroscopic abnormalities were found in foetuses or fetal membranes.
Bacterial culture of gastric content was negative. Initial PCR tests on foetal tissues for parvovirus, PCV2 and PRRSv returned negative results.
Case 1: histopathologic examinations revealed a lymphocytic and neutrophilic perivascular inflammation in the myocardium.
Case 2: no evidence of myocarditis was observed by histopathology. For both cases, PCV3 PCR returned positive with low Ct values (~14 and ~21 respectively).
In both cases, ISH revealed evidence for multifocal presence of PCV3 DNA in the nuclei of cardiomyocytes and in the tunica media of myocardial arterioles (Fig. 1 to 4). However, in the second case ISH was positive for PCV3 only in tissue of one of the two submitted foetuses, investigations on tissue of the other fetus turned out negative.
Discussion and conclusion
PCV3 was present in foetal tissues and found as sole probable cause for the preterm farrowing and abortions in both cases. Case 2 illustrates that PCV3 DNA may be detected in the myocardium in the absence of detected myocarditis by histopathology. Also, absence of PCV3 in one of the investigated foetuses indicates that multiple foetuses may need to be investigated for diagnosing PCV3 infection in cases of abortion. This case series contributes to the scientific discussion on the role of PCV3 in disease in pigs.
Fig 1.: Image of In Situ Hybridisation consistent with detection of intranuclear PCV3 DNA in myocard (brown colour) (enlarged 10x)
Fig 2.: Image of In Situ Hybridisation consistent with detection of intranuclear PCV3 DNA in myocard (brown colour) (enlarged 20x; scale bar = 80 µm).
Fig 3.: Image of In Situ Hybridisation consistent with detection of intranuclear PCV3 DNA in myocard (brown colour) (enlarged 40x; scale bar = 40 µm).
Fig 4.: Image of In Situ Hybridisation consistent with detection of intranuclear PCV3 DNA in myocard (brown colour) (enlarged 40x).