Seroprevalence of Toxoplasma gondii in cats in mainland China 2016-2020: a meta-analysis

RPA-CRISPR/Cas12a-LFA combined with a digital visualization instrument to detect Toxoplasma gondii in stray dogs and cats in Zhejiang province, China

Toxoplasma gondii, which causes toxoplasmosis, is prevalent in warm-blooded animals, such as cats, dogs, and humans. T. gondii causes economic losses to livestock production and represents a potential risk to public health. Dogs and cats are common hosts in the epidemiology of toxoplasmosis. The current molecular diagnostic tools for T. gondii infection require high technical skills, a laboratory environment, and complex instruments. Herein, we developed a recombinase polymerase amplification (RPA)-clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 12a (Cas12a) assay to detect T. gondii. The lowest limit of detection of the assay was 31 copies/μL for the T. gondii B1 gene. In addition, we established a visual RPA-CRISPR/Cas12a lateral flow band assay (RPA-CRISPR/Cas12a-LFA) combined with a digital visualization instrument, which minimized the problem of false-negative results for weakly positive samples and avoided misinterpretation of the results by the naked eye, making the LFA assay results more accurate. The assay established in this study could identify T. gondii within 55 min with high accuracy and sensitivity, without cross-reaction with other tested parasites. The developed assay was validated by establishing a mouse model of toxoplasmosis. Finally, the developed assay was used to investigate the prevalence of T. gondii in stray cats and dogs in Zhejiang province, Eastern China. The positive rates of T. gondii infection in stray cats and dogs were 8.0% and 4.0%, respectively. In conclusion, the RPA-CRISPR/Cas12a-LFA is rapid, sensitive, and accurate for the early diagnosis of T. gondii, showing promise for on-site surveillance.

IMPORTANCE

Toxoplasma gondii is a virulent pathogen that puts millions of infected people at risk of chronic disease reactivation. Hosts of T. gondii are distributed worldwide, and cats and dogs are common hosts of T. gondii. Therefore, rapid diagnosis of early T. gondii infection and investigation of its prevalence in stray dogs and cats are essential. Here, we established a visual recombinase polymerase amplification-clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 12a-assay combined with a lateral flow band assay and a digital visualization instrument. Detailed analyses found that the assay could be used for the early diagnosis of T. gondii without false-negative results. Moreover, we detected the prevalence of T. gondii in stray cats and dogs in Zhejiang province, China. Our developed assay provides technical support for the early diagnosis of T. gondii and could be applied in prevalence surveys of T. gondii in stray dogs and cats.

Serological and molecular survey of Toxoplasma gondii infection and associated risk factors in urban cats in Kunming, Southwest China

Toxoplasma gondii (T. gondii) is a worldwide zoonotic parasite that can infect almost warm-blood animals, including humans, which seriously affect the health of host. Cats are known to be the only definitive host of T. gondii and continuously excrete highly infectious oocysts. This parasite carried by the companion animals leads to a great public health risk. However, there is little information on epidemiology of T. gondii in urban cats in Kunming, Southwest China. In the present study, a total of 231 serum and fecal samples were collected in Kunming aera, and then seroprevalence of T. gondii IgG antibodies in serum and molecular investigation in feces were analyzed to elucidate T. gondii infection in urban cats. The results revealed that 168 of 231 cats (72.7%) were positive for T. gondii antibodies, and 1 of 74 cat feces (1.4%) also showed a positive PCR for T. gondii DNA. The positive fecal sample was sequenced and then phylogenetically analyzed, and the isolate of T. gondii in the present study was closely related to T. gondii strain CN. In addition, the food, water and age of cats were identified as the risk factor for seropositivity. Overall, our findings indicate the widespread occurrence of T. gondii infection in urban cats in Kunming, Southwest China and identify food, water and age are the risk factors associated with T. gondii infection, which can provide effective information for developing strategies to prevent and control this zoonosis.

Proteomics analysis of Toxoplasma gondii merozoites reveals regulatory proteins involved in sexual reproduction

Sexual reproduction plays a crucial role in the transmission and life cycle of toxoplasmosis. The merozoites are the only developmental stage capable of differentiation into male and female gametes, thereby initiating sexual reproduction to form oocysts that are excreted into the environment. Hence, our study aimed to perform proteomic analyses of T. gondii Pru strain merozoites, a pre-sexual developmental stage in cat IECs, and tachyzoites, an asexual developmental stage, using the tandem mass tag (TMT) method in order to identify the differentially expressed proteins (DEPs) of merozoites. Proteins functions were subjected to cluster analysis, and DEPs were validated through the qPCR method. The results showed that a total of 106 proteins were identified, out of which 85 proteins had quantitative data. Among these, 15 proteins were differentially expressed within merozoites, with four exhibiting up-regulation and being closely associated with the material and energy metabolism as well as the cell division of T. gondii. Two novel DEPs, namely S8GHL5 and A0A125YP41, were identified, and their homologous family members have been demonstrated to play regulatory roles in oocyte maturation and spermatogenesis in other species. Therefore, they may potentially exhibit regulatory functions during the differentiation of micro- and macro-gametophytes at the initiation stage of sexual reproduction in T. gondii. In conclusion, our results showed that the metabolic and divisional activities in the merozoites surpass those in the tachyzoites, thereby providing structural, material, and energetic support for gametophytes development. The discovery of two novel DEPs associated with sexual reproduction represents a significant advancement in understanding Toxoplasma sexual reproduction initiation and oocyst formation.

Seroprevalence of Toxoplasma gondii in water buffaloes and cats in Guangxi, China

Toxoplasma gondii is a pathogen that poses a serious threat to human health and causes significant economic losses to the global livestock industry. The prevalence of toxoplasmosis infection has been reported to be high in humans and animals around the world, but the occurrence of the disease has not yet been reported in water buffaloes in Guangxi Zhuang Autonomous Region, southern China. To understand the overall seroprevalence of T. gondii infection in Guangxi, a total of 1041 water buffalo and 114 cat serum samples were examined using an indirect enzyme-linked immunosorbent assay (I-ELISA). Of the 1041 water buffaloes analyzed, an overall seroprevalence of 52.9% (551/1041) was obtained, with year, season, and city location being significant factors affecting the rate of T. gondii infection in water buffaloes (P < 0.001). The results also revealed a high seroprevalence of 57% (65/114) in cats. Given that buffalo milk and meat products are vital food sources, these findings suggest that toxoplasmosis in water buffaloes may be a public health threat. This study provides the first T. gondii seroprevalence data in Guangxi, which could contribute to the prevention and control of toxoplasmosis in the region.

Rapid and Visual Detection of Toxoplasma gondii in Blood Samples from Pet Cats and Dogs by Loop-Mediated Isothermal Amplification

Background: Toxoplasma gondii is an obligate intracellular parasite that invades nearly all nucleated cells of a broad spectrum of vertebrate hosts, and which may cause serious disease in immunocompromised patients, as well as in the immunologically incompetent fetus. This study aimed to establish a loop-mediated isothermal amplification (LAMP) technique to rapidly detect T. gondii in the blood infection by targeting the 529 bp repeat element of T. gondii. Methods: A turbidity monitoring system, together with visual reagent, was used to test the amplification result of the LAMP assay. In addition, the specificity and sensitivity of the LAMP assay were measured. Results: The results suggest that the successfully established LAMP assay profile can detect the DNA of T. gondii at 67°C within 40 min. The limit of detection of the LAMP assay was 10¹ copies/μL. No cross reaction occurred with Plasmodium vivax, Toxocara cati, Clonorchis sinensi, Spirometra mansoni or Cryptosporidium parvum. We validated the developed LAMP assay by detecting T. gondii in DNA extracted from 353 blood samples collected from domestic cats and dogs. The percentages of positive results in detecting these blood samples by LAMP and conventional PCR were 5.38% and 2.83%, respectively. Conclusions: Our findings show that the developed LAMP assay offers higher analytical sensitivity than conventional PCR and good analytical specificity, minimizes aerosol contamination, and can be applied to on-site rapid detection of T. gondii.

Seroprevalence and risk factors of Toxoplasma gondii in urban cats from China

BACKGROUND

Toxoplasma gondii infects almost all warm-blooded animals, and cats play a crucial role in the epidemiology of T. gondii as the definitive host. Despite sporadic reports on the seroprevalence of T. gondii in domestic cats, systematic surveys are lacking and some regions remain in China uninvestigated.

METHODS

A total of 1,521 serum samples were collected from 10 regions of China and analyzed by antibodies against T. gondii by ELISA with the purpose of identifying risk factors of T. gondii infection in cats across China and obtaining seroprevalence data from some previously uninvestigated areas.

RESULTS

Antibodies to T. gondii were detected in 62 of 1,478 (4.2%) urban pet cats and in 9 of 43 (20.9%) stray cats. Among the regions examined, the prevalence was 13% in Sichuan, 12.8% in Chongqing, 6.4% in Hunan, 2.5% in Hubei and 0.9% in Guangdong. Additionally, this is the first report on the seroprevalence of T. gondii in urban pet cats from Qinghai (6.2%), Anhui (3.1%), Jiangxi (2.5%), Shaanxi (2.4%) and Ningxia (1.6%). The age and lifestyle (stray or pet) of cats were identified as the risk factors for seropositivity by multivariate analysis of the data.

CONCLUSIONS

Our findings improve our understanding of seroprevalence and risk factors of T. gondii infection in cats across China, and provide useful information for the formulating of preventive and control measures against this widespread zoonotic parasite.

Toxoplasma gondii and Neospora caninum Infections in Stray Cats and Dogs in the Qinghai–Tibetan Plateau Area, China

Simple Summary

Diseases caused by parasites have introduced serious threats to human health and the development of animal husbandry in the Qinghai–Tibetan Plateau Area (QTPA), such as toxoplasmosis caused by Toxoplasma gondii and neosporosis caused by Neospora caninum. However, information on the epidemiology of toxoplasmosis and neosporosis in stray cats and dogs which are the definitive hosts of T. gondii and N. caninum in the QTPA is limited. The aim of this study was to establish a detailed record of the seroprevalence of T. gondii and N. caninum-specific IgG and IgM antibodies in serum samples and the molecular epidemiology in feces from stray cats and dogs in the plateau area. The results revealed that stray cats and dogs in the QTPA, China present both T. gondii and N. caninum infection through the antibodies and antigen detection of the indirect ELISA tests and qPCRs. The present study suggests the prevalence of acute neosporosis and chronic re-emergence of toxoplasmosis in stray cats and dogs in the testing area. To the best of our knowledge, this is the first report of T. gondii and N. caninum infection in cats and dogs in the QTPA, and the first determination of N. caninum infection in cats in China. In conclusion, stray cats and dogs play key roles in the transmission and prevalence of T. gondii and N. caninum in the plateau area.

Abstract

Toxoplasma gondii and Neospora caninum belong to the Apicomplexan protozoa which is an obligate intracellular parasite, causing toxoplasmosis and neosporosis throughout the world. Cats and dogs are the definitive hosts of these two parasites. However, information on the epidemiology of toxoplasmosis and neosporosis in stray cats and dogs in the Qinghai–Tibetan Plateau Area (QTPA) is limited, and little is known about the diversity of the diseases. Therefore, the aim of this study was to perform indirect ELISA tests based on recombinant TgSAG1, TgGRA1, NcSAG1 and NcGRA7 proteins to establish a detailed record of the seroprevalence of T. gondii and N. caninum-specific IgG and IgM antibodies in serum samples and to develop qPCR amplification based on TgB1 and NcNc5 genes to conduct molecular epidemiology in feces from stray cats and dogs in the QTPA. In the current study, a total of 128 cat serum samples were analyzed through serological tests in which 53 (41.4%) and 57 (44.5%) samples were found positive for T. gondii specific-IgG and IgM antibodies, and 2 (1.6%) and 74 (57.8%) samples were confirmed positive for N. caninum specific-IgG and IgM antibodies, respectively. Out of 224 stray dog sera, 59.8% and 58.9% were recorded as positive against anti-Toxoplasma IgG and IgM antibodies, 17.9% and 64.7% were detected positive against Neospora IgG and IgM. On the other hand, 1 of 18 cat fecal samples was successfully amplified within the Ct value of 10 to 30 while no cat was positive for neosporosis. Moreover, a higher prevalence of toxoplasmosis in stray dogs (14.5%, 16/110) than of neosporosis (5.5%, 6/110) with different parasite numbers were found. Further analysis showed that no significant sex differences were found nor between the overall infection rates of T. gondii and N. caninum in this study. This study suggests that stray cats and dogs play key roles in the transmission and prevalence of T. gondii and N. caninum in the plateau area.