Coinfection of Mycoplasma suis and porcine circovirus type 3 is linked to reproductive failure in pig farms

Background and Aim: Reproductive disorders in swine herds pose significant challenges to pig breeding due to both infectious and non-infectious factors. In large-scale pig farming, coinfections are increasingly common, affecting sow health and herd productivity. This study aimed to determine occurrence and coinfection patterns of Mycoplasma suis and porcine circovirus type 3 in Vietnamese pig farms and to evaluate their association with reproductive disorders and clinical signs in affected herds. Materials and Methods: We collected 291 samples from 15 farms, composed of whole blood and various tissues from fetuses and weak-born piglets. Molecular biological testing was conducted to detect key pathogens of interest. Consistently, porcine circovirus type 3 (PCV3) and porcine Hemoplasma were detected and sequenced for the whole genome and partial 16S rRNA, respectively. The genetic diversity of PCV3 and Mycoplasma suis was analyzed. Results: Various clinical signs, including abortion, stillborn, mummified, and weak-born piglets, and dermatitis, were recorded. M. suis was detected in 252/291 (86.59%) samples from all 15 surveyed farms, with an occurrence of 100%. PCV3 was detected in 35.05% (102/291) samples and 73.3% (11/15) of farms. PCV3 and M. suis coinfections were observed in 29.21% of the positive samples. It should be noted that most PCV3 Ct-values were above 30, indicating the existence of PCV3 in the herd but with insufficient data to confirm its pathogenic potential. The complete genomes of 10 PCV3 strains identified in this study exhibited high sequence homology, with >97% nucleotide identity. In addition, the eight partial 16S rRNA porcine Hemoplasma sequences shared absolute identity with M. suis isolates from pigs in China and Germany. Conclusion: This report on the occurrence of M. suis and PCV3 in pigs from farms with reproductive failure provides important insights into the expanding global distribution of these pathogens. Our findings warrant further investigations of the pathogenic potential and economic implications of M. suis and PCV3 in pigs with reproductive failure in Vietnam. Keywords: coinfection, Mycoplasma suis, porcine circovirus type 3, reproductive failure.