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

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.

Toxoplasma gondii and Neospora caninum in invasive wild boars (Sus scrofa) and hunting dogs from Brazil

“…They noted discrepancies between duplicate sample results within and among test assays, with seroprevalence rates of the same samples ranging from 12.5% to 67.8% and 84.1%. Consistent with our findings, they also found no histopathological evidence of N. caninum in tissue samples ( Haydett et al, 2021 ). A recent review highlighted the lack of comprehensive documentation regarding the histopathological diagnosis of T. gondii in pigs ( Dubey et al, 2020 ).…”

“…Furthermore, the lack of consistent and reliable test assays for detecting infections in wild boars could contribute to heterogeneity within and among studies ( Rostami et al, 2017 ; Haydett et al, 2021 ). For instance, to determine the seroprevalence of N. caninum in wild boars, Haydett et al (2021) employed two different commercially available ELISA test kits and IFAT. They noted discrepancies between duplicate sample results within and among test assays, with seroprevalence rates of the same samples ranging from 12.5% to 67.8% and 84.1%.…”

Molecular detection of Toxoplasma gondii, Neospora caninum and Sarcocystis spp in tissues of Sus scrofa slaughtered in southern Brazil

“…Little is known about the exact role of wild boars in the introduction and maintenance of N. caninum infection in the wild and its possible transmission to domestic animals ( Haydett et al, 2021 ). In Brazil, studies have demonstrated the presence of antibodies against N. caninum in wild boars ( Soares et al, 2016 ), but there are still no reports on the application of molecular diagnostic techniques.…”

“…Although the DNA detection rate was 5.06%, it is important to highlight that wild boars could be intermediate hosts for this agent ( Cerqueira-Cézar et al, 2016 ). These animals may be infected through the ingestion of sporulated oocysts that remain viable in the soil, food, and water for long periods ( Haydett et al, 2021 ).…”

“…Another closely related Apicomplexa protozoan, Neospora spp., was originally described as causing neuromuscular disease in dogs but is currently a major cause of neonatal mortality, abortion, and encephalitis in ruminants ( Lindsay et al, 1995 ; Lindsay & Dubey, 2020 ). Although there is no zoonotic evidence, wild boars, which are omnivorous animals, can act as intermediate hosts by developing cysts with bradyzoites in their muscles that can infect domestic or wild canids and other species of intermediate hosts ( Haydett et al, 2021 ).…”