Prevalence and Characterization of Salmonella spp. Isolated from Feral Pigs in Texas

Introduction: While it is well established that livestock are a key reservoir for Salmonella, the importance of wildlife species as reservoirs for this zoonotic foodborne pathogen is poorly defined. The population of feral pigs (Sus scrofa) in the United States might be as high as 8 million, with an estimated 2.6 million in Texas alone. Feral pigs are known to invade agricultural lands in search of food, which has led to the dissemination of zoonotic enteric pathogens through fecal contamination of crops in the past.

Purpose: Our aims were to determine the prevalence of Salmonella among feral pigs in Texas and to characterize the antimicrobial susceptibility of these isolates, thus facilitating an assessment of public health risk presented by this wildlife reservoir.

Methods: We have an ongoing active surveillance program for Salmonella fecal shedding among feral pigs in Texas. This program is supported by a collaboration with USDA-APHIS-Wildlife Services, which has a dedicated system in place for managing feral pig damage and disease concerns throughout the state. Fecal samples are being sent to Texas A&M University for Salmonella isolation using standard bacteriologic culture techniques. Antimicrobial susceptibility testing is performed on isolates using the Sensititre broth microdilution method. Date, geographic location, and data on each pig are collected.

Results: To date, fecal samples have been obtained from 99 feral pigs in 14 counties throughout Texas. Twenty-four (24.2%) samples from 10 counties were culture-positive for Salmonella spp. Those Salmonella isolates (n = 17) tested against a panel of 15 antimicrobial agents were pansusceptible.

Significance: This ongoing study is one of the first to shed light on the ecology and epidemiology of Salmonella among feral pigs in the U.S. Our data indicate that Salmonella is frequently found among feral pigs in Texas, with important implications for public health.