Isolation and genetic characterization of viable Toxoplasma gondii from tissues and feces of cats from the central region of China

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Highlights

Abstract

Cats are important in the epidemiology of toxoplasmosis because they are the only definitive hosts that excrete environmentally resistant Toxoplasma gondii oocysts. Little is known of feline toxoplasmosis in China and most of the literature is in Chinese. Here we summarized all published reports on feline toxoplasmosis in English and report first identification of oocyst excretion by naturally infected cats in China. Unfrozen tissues of 42 cats and feces of 360 cats from China were bioassayed in mice for isolation of T. gondii. Antibodies to T. gondii were found in 21 of 42 (50%) of cats by the modified agglutination test (cut-off 1:25). Viable T. gondii was isolated from tissues of eight of 21 seropositive but not from 21 seronegative (<1:25) cats. Viable T. gondii was isolated from feces of one cat. DNA derived from cell cultured tachyzoites of all nine T. gondii isolates was characterized by PCR–RFLP at 10 loci (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). Four genotypes were found; the genotypes of tissue isolates were ToxoDB #9 in six, ToxoDB #2 in one, and ToxoDB #17 in one. The fecal isolate was ToxoDB #1.To our knowledge, the present study is the first isolation of T. gondii from cat feces from China.

Introduction

The protozoan parasite Toxoplasma gondii infects virtually all warm-blooded animals, including birds, humans, livestock, and marine mammals (Dubey, 2010). The ingestion of tissue cysts from undercooked meat or consuming food or water contaminated with oocysts are the two most important modes of transmission of T. gondii. Felids are the most important hosts in the epidemiology of toxoplasmosis because they are the only hosts known to excrete environmentally resistant oocysts in feces. Additionally, cats are also a source of food for humans in some regions.

China has an estimated 53 million domestic cats (http://www.mapsofworld.com/world-top-ten/countries-with-most-pet-cat-population.html) and an unknown number of wild cats.

Comparatively little is known of toxoplasmosis in cats in China (Fig. 1, Table 1, Table 2) and there is no information on the excretion of T. gondii oocysts by cats in China. Here, we report seroprevalence, isolation, and genetic characterization of T. gondii in cats from Central China, and the first isolation of T. gondii oocysts from cat in China.

Section snippets

Naturally infected cats and sampling

Samples from 42 cats were collected by personnel of Veterinary Pathology Laboratory, Henan Agriculture University. Apparently healthy cats were bought in two batches in summer of 2014 (31 from Henan Province in May and 11 in July from Zhejiang Province) from pet market or farms. Available background information is summarized in Table 3. The cats were killed humanely according to PRC laws for slaughtering of food animal. From each cat, serum, tongues and hearts were obtained for T. gondii

Results

Antibodies to T. gondii were found in 21 of 42 cats (50%) with titers of 100 in two, 800 in three, 1600 in two, 3200 in four, 6400 in four, and 12,800 in six. Seropositivity rates did not vary with respect to gender, and source of cats; antibodies were detected in 10 of 21 males, 11 of 21 females, in nine of 19 in pets, 10 of 19 in stray cats, and two of four farm cats.

Viable T. gondii were isolated from eight of 21 seropositive cats, but not from 21 seronegative cats by bioassay in mice (Table

Discussion

Data summarized in Table 1, Table 2 and Fig. 1 indicate a highly variable prevalence, much depending on the cats surveyed and the methods employed for testing. Seroprevalence data indicate exposure rates of up to 100% (Table 1, Table 2). Earlier surveys from China employed locally available ELISA and IHA kits but these tests have not been critically evaluated for the specificity. We have summarized all reports in Table 1 for the benefit of readers because most of these were published in

Conflict of interest

None.

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