Detection of Parvoviridae and Circoviridae family species from blood of gilts in central Mexico backyard farms

Objective: To determine the DNA prevalence of Parvoviridae family species (PPV1, PPV2, PPV5, and PPV6) and Circoviridae family species (PCV2 and PCV3) in PCV2-unvaccinated backyard farms in central Mexico through gilt blood samples. Design/Methods/Approach: Blood samples were collected from 60 gilts raised in backyard farms located in the State of Mexico, Hidalgo, and Querétaro. Genomic DNA was extracted using a commercial kit. Nested PCR was performed on each sample using previously reported primers and amplification conditions for PPV1, PPV2, PPV5, and PPV6, PCV2, and PCV3. Results: Positive cases were detected for each viral species tested: 5.2% (3/58) for PPV1, 89.6% (52/58) for PPV2, 67.2% (39/58) for PPV5, 25.9% (15/58) for PPV6, 50% (29/58) for PCV2, and 69% (40/58) for PCV3. The most prevalent species was PPV2, followed by PCV3 and PPV5, while PPV1 showed the lowest prevalence. Overall, 96.5% of the samples exhibited co-infection with at least one other species, with triple assortments being the most frequent, particularly in backyard farms from the State of Mexico. However, double assortments were predominant in Querétaro. The most common viral combinations were PPV2/PCV3 and PPV2/PPV5. The former was dominant in Querétaro, while the latter was widespread in Hidalgo and the State of Mexico. Additionally, PCV2 was significantly associated with co-infections in Querétaro, whereas both PCV2 and PCV3 were predominant in the State of Mexico and Hidalgo. Study Limitations/Implications: Backyard farms have a low number of sows and limited accessibility for sampling. Increasing the sample size would provide a more comprehensive understanding of the interactions between these viral species in non-industrial farms. Findings/Conclusions: All viral species analyzed were detected in the blood of backyard sows. Prevalence and co-infection patterns varied by state and farm. Notably, PPV5 was the predominant virus in Hidalgo and the State of Mexico, often co-occurring with PPV2, PCV2, and PCV3, in that order. In contrast, PPV2 and PPV5 were the most frequent double co-infections in Querétaro. This is the first report documenting the DNA prevalence of PPV2, PPV5, PPV6, and PCV3 in backyard farms. Given the high co-infection rates observed in reproductive sows, further studies are necessary to assess their impact on swine health and productivity.