Exposure of a population of invasive wild pigs to simulated toxic bait containing biomarker: implications for population reduction.

BACKGROUND: An international effort to develop an acute and humane toxic bait for invasive wild pigs (Sus scrofa) is underway to curtail their expansion. We evaluated the ability to expose a population of wild pigs to a simulated toxic bait (i.e., placebo bait containing a biomarker, rhodamine B, in lieu of the toxic ingredient) to gain insight on potential population reduction. We used 28 GPS-collars and sampled 428 wild pigs to examine their vibrissae for evidence of consuming the bait. RESULTS: We estimated that 91% of wild pigs within 0.75 km of bait sites (total area = 16.8 km2 ) consumed the simulated toxic bait, exposing them to possible lethal effects. Bait sites spaced 0.75-1.5 km apart achieved optimal delivery of the bait, but wild pigs ranging ≥ 3 km away were susceptible. Use of wild pig-specific bait stations resulted in no non-target species directly accessing the bait. CONCLUSION: Results demonstrate the potential for exposing a large proportion of wild pigs to a toxic bait in similar ecosystems. Toxic baits may be an effective tool for reducing wild pig populations especially if used as part of an integrated pest management strategy. Investigation of risks associated with a field-deployment of the toxic bait is needed. © 2018 Society of Chemical Industry.

Survey of Feral Swine ( Sus scrofa ) Infection with the Agent of Chagas Disease ( Trypanosoma cruzi ) in Texas, 2013-14.

: Feral swine ( Sus scrofa ) are an invasive species and reservoir of numerous zoonotic pathogens in the US, and Texas leads the nation in the estimated population size of feral hogs. Texas also harbors enzootic transmission cycles of the protozoan parasite Trypanosoma cruzi , agent of Chagas disease. Given previous evidence that swine can serve as reservoirs of T. cruzi in Latin America and new evidence of triatomines (kissing bugs) feeding on swine in Texas, we measured the prevalence of T. cruzi infection in feral swine in Texas. From 2013 to 2014, we sampled blood and/or cardiac tissue from 78 feral swine across 14 Texas counties (seven with and seven without prior documentation of kissing bug occurrence) and used PCR and histopathology to detect T. cruzi infection. We determined an overall infection prevalence of 6% (3 of 54) based on PCR evaluation of cardiac tissue, and no blood samples were positive (n=72). All three positive pigs were from counties where kissing bugs are documented. No T. cruzi amastigotes were noted on histopathology (n=54). Sarcocysts were observed in 10 (18%) of the samples, five of which also had mild focal areas of degeneration and inflammatory cell infiltration. Eco-epidemiologic investigations can provide an assessment of contributions of feral hogs to maintenance of T. cruzi across a landscape to help protect human and animal health.

Prevalence and Diversity of Cryptosporidium and Giardia Identified Among Feral Pigs in Texas.

The population size and geographic range of feral pigs in the United States are rapidly expanding. Nevertheless, the role of this invasive species in the ecology and transmission of zoonotic enteric pathogens is poorly understood. Our objectives were to describe the prevalence and diversity of Cryptosporidium and Giardia shedding among feral pigs throughout Texas and to identify risk factors for infection. Fecal samples were collected from feral pigs in Texas from February 2014 through May 2015. Cryptosporidium oocysts and Giardia cysts were detected using a direct immunofluorescence assay, and genotyping of positive samples was performed. The prevalence of Cryptosporidium shedding was 1.6% (6/370), and C. scrofarum and C. suis were identified. The prevalence of Giardia shedding was 4.3% (16/370), and assemblages A and E were identified. Cryptosporidium shedding was significantly more common among juvenile and subadult pigs than among adult pigs, but age group was not associated with Giardia shedding status. Feral pigs may serve as a source of Cryptosporidium and Giardia transmission to humans and livestock.

Impact of baiting on feral swine behavior in the presence of culling activities.

We studied the effects of baiting on feral swine (Sus scrofa) movements and corresponding likelihood of disease spread under real and simulated culling pressure. Our objectives were to determine the proportion of feral swine that used the bait station site, and if baiting of feral swine altered areas of utilization, distances from location centroids to treatment location (control or bait station), and movement rates by survivors during culling activities. We hypothesized that the bait station would increase the sedentary nature of feral swine, thus reducing the potential for dispersal and hence disease dispersal. Our experiment was conducted between February and May 2011 on the Rob and Bessie Welder Wildlife Foundation (WWF) in San Patricio County, Texas. We trapped 83 feral swine and placed GPS collars on 21 animals. We established and maintained a centralized bait station on one side of the WWF from 13 March to 27 April. We conducted population-wide culling activities, including trapping, controlled shooting, drive shooting, and aerial gunning, from 3 to 27 April and removed 143 feral swine (4.6feral swine/km(2)). Areas of utilization did not differ between treatments (control or bait station). However, we found location centroids of bait station site feral swine to be closer to the treatment location than those of control site animals and daily movement rates of bait station site feral swine to be 39% greater than movement rates of control site animals. Based on our observation that only 62% of feral swine trapped in proximity to the bait station used it, we cannot recommend baiting as an alternative to fences for containing animals during culling activities. However, there is value in using bait stations to describe patterns of feral swine movements, facilitate observation, and improve efficacy when conducting removals.