Toxoplasma gondii seroprevalence and genotype diversity in select wildlife species from the southeastern United States

Abstract

Background Toxoplasma gondii is a widespread protozoan parasite that infects humans and other animals. Previous studies indicate some genotypes of T. gondii are more frequently isolated in wildlife than agricultural animals, suggesting a wild/feral animal diversity model. To determine seroprevalence and genetic diversity of T. gondii in southeastern US wildlife, we collected sera from 471 wild animals, including 453 mammals and 18 birds, between 2011 and 2014. These serum samples were assayed for T. gondii infection using the modified agglutination test (MAT). Heart or tongue tissues from 66 seropositive animals were bioassayed in mice and 19 isolates were obtained. The isolated parasites were genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method employing 10 genetic markers.ResultsOne hundred and ninety-six of 471 samples (41.6%) had a titer ≥1:32 and were considered positive for T. gondii infection. Of 453 mammals, 195 (43%) were seropositive, whereas only one (5.6%) of 18 birds was seropositive. The seroprevalence in mammals was significantly higher than in the birds. Mammalian hosts with adequate samples size (≥ 20) comprised white-tailed deer (n = 241), feral hogs (n = 100), raccoons (n = 34) and coyotes (n = 22), with seroprevalences of 41.0%, 51.0%, 50.0% and 72.7%, respectively. Coyotes had significantly higher seroprevalence than the white-tailed deer. Genotyping revealed five distinct genotypes, including the ToxoDB PCR-RFLP genotype #5 (a.k.a type 12) for 15 isolates, genotype #3 (a.k.a. type II) for 1 isolate, and genotypes #154, #167 and #216, each for 1 isolate. The results showed moderate to high infection rates of T. gondii in white-tailed deer, feral hogs, raccoons and coyotes. Genotyping results indicated limited genetic diversity and a dominance of genotype #5, which has been reported as a major type in wildlife in North America.ConclusionsWe conclude that T. gondii infection is common in game animals (white-tailed deer and feral hogs) in the southeastern US, which may pose a food safety risk to humans. Further research is necessary to understand T. gondii transmission from wildlife to farm animals and humans.

Toxoplasmosis: The Heart of the Diagnosis

“…This case of acute toxoplasmosis, with a related suspected case, was acquired after ingestion of the undercooked heart of a white-tailed deer (WTD). The heart likely contained Toxoplasma cysts, as has previously been demonstrated in WTD [1]. This led to infection with Toxoplasma upon ingestion of the heart without it being adequately cooked.…”

“…Although most cases of toxoplasmosis are subclinical or present with mild flu-like symptoms, Toxoplasma gondii was the second deadliest foodborne pathogen in the United States between 2000 and 2008, with 327 deaths estimated annually [7, 8]. More severe cases of toxoplasmosis may be associated with atypical genotypes, some of which have been identified in wildlife in the United States, including WTD [1].…”

“…As common game animals with high Toxoplasma seroprevalence, WTD have significant potential for transmission of Toxoplasma to humans, representing an important public health issue [1, 2]. Few cases of direct deer-to-human transmission have been previously reported, and, to our knowledge, there have been no prior reports of toxoplasmosis contracted specifically from the ingestion of the heart of a WTD [4, 5].…”

“…Toxoplasma gondii , a single-celled parasite able to infect many animals, can be transmitted to humans via ingestion of contaminated water or food containing Toxoplasma cysts [1, 2]. Seroprevalence in humans is estimated at ~11% in the United States.…”

“…Seroprevalence in humans is estimated at ~11% in the United States. In white-tailed deer ( Odocoileus virginianus ), seroprevalence is estimated at 30%–60% specifically in the Southeastern United States [1, 3]. In rare case reports, deer have been implicated in the transmission of Toxoplasma to hunters after consumption of raw or undercooked venison [4, 5].…”