Seroprevalence, isolation, and co-infection of multiple Toxoplasma gondii strains in individual bobcats (Lynx rufus) from Mississippi, USA

Authors: VERMA, SHIV - Non ARS Employee; SWEENEY, AMY - National Instiute Of Allergy And Infectious Diseases (NIAID, NIH); LOVALLO, MATTHEW - Pennsylvania Game Commission, Bureau Of Wildlife Management; CALERO-BERNAL, RAFAEL - Non ARS Employee; Kwok, Oliver; SU, CHUNLEI - University Of Tennessee; GRIGG, MICHAEL - National Instiute Of Allergy And Infectious Diseases (NIAID, NIH); Dubey, Jitender

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2017
Publication Date: 2/24/2017
Citation: Verma, S., Sweeney, A., Lovallo, M., Calero-Bernal, R., Kwok, O.C., Su, C., Grigg, M., Dubey, J.P. 2017. Seroprevalence, isolation, and co-infection of multiple Toxoplasma gondii strains in individual bobcats (Lynx rufus) from Mississippi, USA. International Journal for Parasitology. 47:297-303.

Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating under cooked meat from infected animals and food and water contaminated with oocyst. Why some people become ill and even die from toxoplasmosis whereas others remain asymptomatic is largely unknown. The genetic characteristics of T. gondii strains are considered a factor in the pathogenesis on clinical disease. Both the prevalence of T. gondii infections and the severity of clinical toxoplasmosis are higher in children in Brazil than in USA and Europe. Repeated infections with different T. gondii strains is thought to be a factor for the severity of toxoplasmosis. The underlying mechanism for the parasite virulence is also not fully understood. Sexual recombination of T. gondii strains (that can occur only in intestine of cats) could enhance T. gondii virulence. In the present study the authors found for the first time that bobcats in total wilderness in Mississippi were infected with more than 1 strain of T. gondii. The results will be useful for parasitologists, biologists, and epidemiologists.

Technical Abstract: Toxoplasma gondii causes lifelong chronic infection in both feline definitive hosts and intermediate hosts. Multiple exposures of the parasite are likely to occur in nature because of high environmental contamination. Here, we present data of high seroprevalence and multiple T. gondii strain co-infections in individual bobcats (Lynx rufus). Unfrozen samples (blood, heart, tongue, and feces) were collected from 35 bobcats hunted for food and fur from total wilderness in Mississippi, USA. Toxoplasma gondii antibodies were detected in serum by the modified agglutination test (1:_200) in all 35 bobcats. Hearts from all bobcats were bioassayed in mice and viable T. gondii was isolated from 21; these strains were further propagated in cell culture. Additionally, DNA was extracted from digests of tongues and hearts of all 35 bobcats; T. gondii DNA was detected in tissues of all 35 bobcats. Genetic characterization of DNA from cell culture-derived isolates was performed by multiplex PCR using 10 PCR-RFLP markers. Results showed that ToxoDB genotype #5 predominated (in 18 isolates) with a few other types (#24 in two isolates, and #2 in one isolate). PCR-DNA sequencing at two polymorphic markers GRA6 and GRA7 detected multiple strains co-infecting the tissues of bobcats; most possessing Type II or drifted Type II (designated IIa) alleles at GRA7 versus Type X (HG-12) alleles largely at GRA6. Our results suggest that individual bobcats have been exposed more than one parasite strains during their life time.