Flies and beetles-mediated transmission of pathogens in domestic pigs: a systematic review

The presence of flies and beetles in pig farms is common and raises concerns about their potential role in pathogen transmission. These concerns become even more significant when live insect larvae are used as animal feed. If not fully consumed by pigs, the larvae may remain on the farm, develop into adults, and thereby pose health risks. In order to implement effective biosecurity measures on farms, it is important to have a comprehensive understanding of how these insects contribute to pathogen transmission. This systematic review, conducted in accordance with PRISMA guidelines, seeks to evaluate the available evidence regarding the role of flies and beetles in transmitting pathogens to domestic pigs. A comprehensive search of PubMed®, Scopus, and Web of Science databases, focusing on peer-reviewed literature published between 2007 and 2023 in Europe and North America was conducted. The search identified 1,062 initial records, of which 39 articles met the inclusion criteria after screening and evaluation. Among the selected studies, 87% (34/39) focused exclusively on flies, 3% (1/39) focused on beetles, and 10% (4/39) included both. Flies were mainly identified as mechanical vectors for 27 pathogenic agents, including viruses, bacteria, and parasites while beetles were associated with the potential transmission of two viruses and one bacterium. Overall, only three studies provided evidence of pathogen transmission, which were based on experimental studies involving flies (African Swine Fever Virus, Porcine Reproductive and Respiratory Syndrome Virus, and Vesicular Stomatitis New Jersey Virus), and one study documented canthariasis caused by Tenebrio molitor larvae. In conclusion, this review identified a number of pathogenic agents that may be transmitted by insects to domestic pigs. The review also demonstrated a scarcity of studies that have convincingly proven the role of insects in pathogen transmission.