Prevalence of Neospora caninum Exposure in Wild Pigs (Sus scrofa) from Oklahoma with Implications of Testing Method on Detection

SIMPLE SUMMARY: Neospora caninum causes abortion and other reproductive challenges in livestock and leads to large economic losses every year. Wild pigs were evaluated for their potential role in the transmission of N. caninum, the parasite that causes neosporosis in cattle and other animals. Three assays were used to identify past or current exposure to N. caninum in wild pigs and histology was performed to determine if there was a pathology consistent with a N. caninum infection in the tissues that were evaluated. The following assays reported positive results: Kit A—67.8%, Kit B—12.5%, Indirect Fluorescent Antibody Test—84.1%, and Histology—0%. Importantly, the assays used in this study were not congruent with all duplicate samples or between test types and demonstrate the need for a more reliable test to identify N. caninum infections in wild pigs to better assess their potential role in disease transmission. ABSTRACT: Neospora caninum is a protozoan parasite, reported as a leading cause of cattle abortions and reproductive failure worldwide, costing the cattle industry approximately $1.3 billion annually. With wild pig (Sus scrofa) populations estimated at over six million in the United States, contact between wild pigs and livestock is inevitable, mainly because of the widespread geographic co-occurrence of the two species. As a known reservoir for numerous fungal, bacterial, viral and parasitic diseases, wild pigs are of particular importance for human and veterinary health relative to the prevention of infectious diseases. The seroprevalence of N. caninum in wild pig populations was previously documented in the United States, raising the question as to their exposure point of prevalence. This research screened 116 individual wild pigs for N. caninum using a variety of available assays. Using two different commercially available ELISA test kits, seroprevalence ranged from 12.5% to 67.8%. The Indirect Fluorescent Antibody Test resulted in our highest percent seroprevalence for these samples, at 84.1%. However, none of our samples showed any presence of N. caninum or associated pathologies via histological evaluation of representative tissues. Importantly, the assays used in this study were not congruent with all duplicate samples or between the test types used. The implications of these non-congruent results demonstrates that currently available testing assays produce variable results, underscoring the need for more reliable testing kits and a standardized methodology when assessing disease prevalence in wildlife, particularly for N. caninum in wild pigs, which impacts prevalence and comparability across studies.