Fecal Shedding of Zoonotic Food-Borne Pathogens by Wild Rodents in a Major Agricultural Region of the Central California Coast

Abstract

ABSTRACTRecent outbreaks of food-borne illness associated with the consumption of produce have increased concern over wildlife reservoirs of food-borne pathogens. Wild rodents are ubiquitous, and those living close to agricultural farms may pose a food safety risk should they shed zoonotic microorganisms in their feces near or on agricultural commodities. Fecal samples from wild rodents trapped on 13 agricultural farms (9 produce, 3 cow-calf operations, and 1 beef cattle feedlot) in Monterey and San Benito Counties, CA, were screened to determine the prevalence and risk factors for shedding of several food-borne pathogens. Deer mice (Peromyscus maniculatus) were the most abundant rodent species trapped (72.5%).Cryptosporidiumspecies (26.0%) andGiardiaspecies (24.2%) were the predominant isolates from rodent feces, followed bySalmonella entericaserovars (2.9%) andEscherichia coliO157:H7 (0.2%). Rodent trap success was significantly associated with detection ofSalmonellain rodent feces, while farm type was associated with fecal shedding ofCryptosporidiumandGiardia. Seasonal shedding patterns were evident, with rodents trapped during the spring and summer months being significantly less likely to be sheddingCryptosporidiumoocysts than those trapped during autumn. Higher rodent species diversity tended to correlate with lower fecal microbial prevalence, and most spatiotemporal pathogen clusters involved deer mice. Rodents in the study area posed a minimal risk as environmental reservoirs ofE. coliO157:H7, but they may play a role in environmental dissemination ofSalmonellaand protozoa. Rodent control efforts that potentially reduce biodiversity may increase pathogen shedding, possibly through promotion of intraspecific microbial transmission.