Prevalence and Genotyping of Toxoplasma gondii in Cats, Rats, and Chickens in Border Areas of Yunnan Province, China

Investigation of Toxoplasma gondii Infection in Yunnan Semi-fine Wool Sheep (Ovis aries) and wild Rodents in Yunnan, China

BACKGROUND

Toxoplasma gondii, a globally distributed zoonotic obligate intracellular parasite, infects a wide array of mammals, including humans, sheep, and birds. As a unique sheep breed in southwestern China, Yunnan semi-fine wool sheep occupies an important position in animal husbandry in Zhaotong due to its strong adaptability, high reproductive rate, and excellent wool quality. Lambs infected with T. gondii are prone to neurological symptoms and growth retardation, while T. gondii infection in ewes can cause abortions, stillbirths, and deformities, thus affecting sheep reproduction and sheep product quality. Meanwhile, mutton and dairy products contaminated with T. gondii can become potential sources of human infection, potentially threatening public health and safety.

METHOD

To understand the T. gondii infection in semi-fine wool sheep in Zhaotong, Yunnan Province, 586 blood samples were collected and subjected to indirect hemagglutination assay (IHA) for T. gondii antibodies, and the infection-related factors were analyzed through cross-sectional analysis. In the meantime, nested PCR was conducted on a total of 217 samples collected from 31 rodents caught in and around the sheep breeding ground to test the T. gondii B1 gene in rodent tissues.

RESULTS

A total of 94 sera tested positive for T. gondii antibodies, with a total positive rate of 16.04% (94/586) (95% CI: 14.77-20.89). Cross-sectional statistical analysis on factors related to semi-fine wool sheep infection rate, including sampling season, sex, age, and weight, suggested that age (< 6 months: 23.81%; 6-12 months: 11.74%; > 12 months: 15.83%) was a significant factor explaining the infection rate differences (P = 0.003 < 0.05, χ2 = 11.62, df = 2). Thus, age was considered a key risk factor for T. gondii infection in this study (odds ratio, OR = 2.35, 95% CI: 1.42-3.87). Nested PCR analysis on 217 (heart, liver, spleen, lung, kidney, brain, and muscle) tissues from the 31 rodents indicated that 11 tested positive. The total infection rate of rodents in and around the breeding ground was 35.48% (11/31), and 14 samples tested positive, with a positive infection rate of 6.45% (14/217).

CONCLUSION

The T. gondii infection rates of semi-fine wool sheep and rodents from their breeding environment in Zhaotong, Yunnan Province, were high, necessitating enhanced prevention, control, and treatment measures to ensure the healthy breeding of semi-fine wool sheep and veterinary public health and safety.

The Detection of Toxoplasma gondii in Wild Rats (Rattus norvegicus) on Mink Farms in Shandong Province, Eastern China

Toxoplasma gondii is a worldwide distributed zoonotic pathogen that threatens public health. However, there have been limited data for T. gondii infection in wild rats (Rattus norvegicus) in China. In the present study, a total of 227 wild rats were captured from three mink farms to investigate T. gondii infection in Shandong Province, eastern China. The DNA was extracted from 25 mg rats' brain tissues and subjected to a PCR amplification by targeting to the T. gondii B1. In 227 wild rat samples, 18 samples (7.93%) were positive for T. gondii. Then, the positive samples were further genotyped based on eight genetic markers, including eight nuclear loci (SAG1, 5'-SAG2, and 3'-SAG2, alternative SAG2, SAG3, GRA6, c29-2, and L358) and an apicoplast locus (Apico) by using the multilocus PCR-restriction fragment length polymorphism technology. Of these samples, eight were genotyped at nine nuclear loci, and two were genotyped at eight nuclear loci, forming three known genotypes (ToxoDB no. 43, ToxoDB no. 91, and ToxoDB no. 189) and two new genotypes. The closest ToxoDB genotypes were observed in wild rats, suggesting the differences in the population structure of the T. gondii between breed farm animals and wild rats. These data revealed the genetic variability of T. gondii in wild rats on mink farms in Shandong Province, with possible implication for public health.

Epidemiological Significance of Toxoplasma Gondii Infections in Wild Rodents: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. Rodents are one of the most important intermediate hosts for T. gondii because they are preyed on by cats, who in turn excrete the environmentally resistant oocysts in their feces and thus spread the infection. Information on T. gondii infections is spread in numerous reports and is not easily accessible to readers. Here, we review prevalence, persistence of infection, clinical disease, epidemiology, and genetic diversity of T. gondii infections in wild rodents worldwide. Data are tabulated by country, by each rodent species alphabetically, and chronologically. Recent genetic diversity of T. gondii strains in rodents is critically evaluated.