Seroprevalence of Toxoplasma gondii infection in dogs and cats in Zhenjiang City, Eastern China

Qing-Xin Liu, Shuai Wang, Li-Qun Wang, Jun Xing, Wen-Jue Gao, Guo-Fang Liu, Bin Zhao, Hai-Bin Zhang, Li-Hua Gao*

1Department of Animal Husbandry and Veterinary Medicine, Jiangsu Polytechnic College of Agriculture and Forestry, Jurong, Jiangsu, 212400, PR China

2College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, PR China

Seroprevalence of Toxoplasma gondii infection in dogs and cats in Zhenjiang City, Eastern China

Qing-Xin Liu1,2#, Shuai Wang2#, Li-Qun Wang1, Jun Xing1, Wen-Jue Gao1, Guo-Fang Liu1, Bin Zhao1, Hai-Bin Zhang2, Li-Hua Gao1*

1Department of Animal Husbandry and Veterinary Medicine, Jiangsu Polytechnic College of Agriculture and Forestry, Jurong, Jiangsu, 212400, PR China

2College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, PR China

PEER REVIEW

Peer reviewer

Dr. Guangwei Zhao, Department of Veterinary Medicine, Southwest University, Chongqing, 402460, PR China.

Tel: +86-18723186371

E-mail: stay612@163.com

Comments

This study provides fundamental epidemiological background regarding the prevalence of toxoplasmosis infection in dogs and cats, and at the same time it raises the concerns about risk factors associated with human exposure. Presentation of data in this manuscript is easily understandable and I feel the flow is good. Over all, the presentation is good and appealing.

Details on Page 727

Objective:To determine the seroprevalence of Toxoplasma gondii (T. gondii) infection in dogs and cats in Zhenjiang City, Jiangsu Province, Eastern China, and to evaluate the main associated risk factors relating to exposure to T. gondii in this region.

Toxoplasma gondii, Dog, Cat, Seroprevalence, Zhenjiang, China

1. Introduction

Toxoplasma gondii(T. gondii) is an important zoonotic intracellular protozoan parasite, which can affect all warm-blooded mammals and birds throughout the world, including humans[1,2].T. gondiiis transmitted by ingestion of tissue cysts from undercooked or raw meat, consumption of food or drink contaminated with oocysts, or ingestion of oocysts from the environment by accident[2-4]. AlthoughT. gondiiinfection rarely causes any clinical symptoms in healthy adults, it may lead to severe consequences in an immunocompromised person such as an AIDS patient or a pregnant woman[5].

Felids play a crucial role in the epidemiology of this parasitic disease because they are the only definitive host, shedding and excreting millions of infective oocysts in a short period of time in their faeces[6]. It is generally suggested that cats probably play a major role intransmittingT. gondiithrough environments contaminated by faeces.

T. gondiiinfections in dogs are important because the infection can cause serious illness in dogs. Dogs can be a transport host forT. gondiioocysts, and dog meat is consumed by humans in several countries[7].

Investigations of the prevalence of antibodies toT. gondiiin dogs and cats have been conducted extensively in the world[8-15]. In recent years, there have also been various surveys ofT. gondiiinfection in dogs and cats in the People’s Republic of China[7,16-22]. However, little is known ofT. gondiiseroprevalence in dogs and cats in Eastern China.

The objectives of the present survey were to determine the seroprevalence ofT.gondiiinfection in dogs sand cats in Zhenjiang City, Jiangsu Province, Eastern China, and to evaluate the main associated risk factors relating to exposure toT. gondiiin this region.

2. Materials and methods

2.1. The study site

The study was conducted in Zhenjiang City, Southwestern Jiangsu Province, covering an area of 3 847 km2in Eastern China. Zhenjiang is situated in the lower reaches of the Yangtze River, between 118°58’ E to 119°58’ E and 31°37’ N to 32°19’ N. The city is in the monsoon climate area of north subtropical zone, with clearly-divided four seasons. Its annual average temperature is 15.6 °C, and the annual average precipitation 1 088.2 mm.

2.2. Sampling of dogs and cats

Blood samples were collected from the leg veins of dogs and cats between Janurary and December 2013 in Zhenjiang City, respectively.

Stray dogs and cats were randomly selected from the Zhenjiang animal shelter, the selected household dogs and cats were pets admitted to several veterinary clinics. Biometric data for dogs and cats, including age, sex, and lifestyle, were recorded. The analysis information regarding stray dogs and cats was estimated based on body condition and by examining dentition. The information about household dogs and cats was taken from the owners.

Blood samples were kept at 37 °C for 2 h and centrifuged at 2 000gfor 5 min. The resulting sera samples were stored at -20 °C until further analysis.

2.3. Determination of antibodies to T. gondii

Antibodies toT. gondiiwere determined using the commercialT. gondiiIgG ELISA Kit (Combined Company, Shenzhen, Guangdong Province, China) according to the manufacturer’s instructions. Positive and negative control sera were provided in the kit. Briefly, theT. gondiispecific antigen was coated on a 96-well ELISA plate. After incubation of the diluted serum sample (1:100) in the test well and subsequent washing, a conjugate was added. The plate was washed again and then a chromogenic enzyme substrate was added. The optical density (OD) at 450 nm was read using a photometer (BIO-RAD, Hercules, CA, USA). A relative rate percent (IRPC) value was obtained using the following formula:

The sera were considered negative toT. gondiiif the IRPC＜2.1, and positive if IRPC＞2.1.

2.4. Statistical analysis

Differences inT. gondiiprevalence between stray and household groups, age groups, and genders were analyzed using aChi-square test. Statistical analysis was performed using Statistic Package for Social Science (SPSS) 16 software for Windows (SPSS Inc., Chicago, Illinois, USA).

2.5. Ethics statement

The collection of serum samples from dogs and cats in the present study was according to the Animal Ethics Procedures and Guidelines of the People’s Republic of China.

3. Results

In the present study, a total of 276 serum samples (160 dogs and 116 cats) were collected and analyzed by ELISA to detect the antibodies against theT. gondii.

3.1. Seroprevalence in dogs

An overall recorded seroprevalence was 13.1% in dogs. Seroprevalence in stray dogs (38.7%) was significantly higher than that in household dogs (6.9%,P＜0.001). The seroprevalence in males was 14.8%, whereas in females, the seroprevalence was 11.4%. Although the seroprevalence in males was higher than the females, the difference was not significant (P＞0.05). The highest prevalence ofT. gondiiinfection was 20.0%, which was detected in 3-6 years old dogs (Table 1).

Table 1 Seroprevalence of T. gondii infection in dogs.

3.2. Seroprevalence in cats

In this study, the overall seroprevalence in cats was 20.70%. Although cats in both areas were infected withT. gondii, the seroprevalence of infection in stray cats (28.60%) was significantly higher (P＜0.05) than that of in household cats (18.20%). The prevalence in males was 21.05%, 20.00% in females and the difference was not significant (P＞0.05). The highest prevalence ofT. gondiiinfection was 33.30%, which was detected in 0-1 year old cats (Table 2).

Table 2 Seroprevalence of T. gondii infection in cats.

4. Discussion

In the present study, the overall seroprevalence ofT. gondiiinfection in dogs in Zhenjiang City was 13.1%, which was lower than that observed in Guangzhou City (21.3%) and Xuzhou City (40.3%)[23,24], higher than that observed in Lanzhou City (10.8%)[18], Sichuan Province (3.5%) and Shanghai Municipality (3.2%)[25,26], and similar to that observed in Henan Province (12.3%) in China[7].

The overall prevalence ofT. gondiiinfection in cats in Zhenjiang City was 20.7%, which was higher than that reported in some other countries, such as in Peru (11.0%) and Thailand (10.1%)[8,13], higher than that in Shanghai Municipality (17.2%)[21], but lower than that observed in Guangzhou City (25.2%), Lanzhou City (21.3%), Beijing Municipality (57.8%) and Yunnan Province(25.1%) in China[20,22,27,28].

The differences in seroprevalences ofT. gondiiin dogs and cats are probably due to the differences in ecological and geographical factors, serologic tests used and the living conditions of dogs and cats.

In this study, female dogs and cats had lower prevalence than the males, although the difference was not significant (P＞0.05). The gender thus was not significantly associated with the presence of antiT. gondiiantibodies in the current study (P＞0.05). This was consistent with reports from some other countries or cities[7,11,16].

Free-living animals such as stray cats, dogs, and foxes can be surveyed as indicators of the environmental spread ofT. gondii[29]. Stray cats are especially important as they shed environmentally resistant oocysts in their feces, and they are increasing in numbers gradually. In this study, seroprevalence ofT. gondiiinfection in stray dogs and cats was significantly higher than that in household dogs and cats (P＜0.05), which was consistent with the reports from some other countries or cities[23,27,30]. Differences in their hunting habits, living conditions and animal welfare may attribute to the differences inT. gondiiseroprevalence between household dogs and cats and stray dogs and cats.

Conflict of interest statement

We have no conflict of interest related with this report.

Acknowledgements

This study was supported by the Project of Access Engineers of Higher Vocational Institutions in Jiangsu Province (Project No. 2013FG042) and the Project of Jiangsu Polytechnic College of Agriculture and Forestry.

Comments

Background

T. gondiiis an obligate intracellular parasite that causes a pathological status known as toxoplasmosis, which has a huge impact on human and animal health. With the improvement in people’s living standards and the awareness of good animal welfare, the number of pet dogs and cats has increased substantially. It’s very important to estimate the prevalence ofT. gondiiin dogs and cats.

Research frontiers

Application of epidemiological surveys to evaluate the status ofT. gondiiinfection with regard to the role of dogs and cats as pet animals in Zhenjiang City, Eastern China, in relation with associated risk factors.

Related reports

According to Yanet al.2012, Zhanget al.2010, Wuet al.2011, Liet al.2012, Qianet al.2012, and Tianet al.2014, surveys have been carried out to determine the status of toxoplasmosis in dogs and cats, but more surveys are required considering the environmental variations in countries like China.

Innovations & breakthroughs

The location targeted in this study, economically is one of the fastest growing cities in China. The popularity of pets, especially dogs and cats is rising; concerns about zoonotic diseases like toxoplasmosis are likely to be encountered. In this study the authors addressed the risk factors associated with the prevalence ofT. gondiiinfection in dogs and cats for the first time in that area, which has reflected important information about the disease.

Applications

As an important zoonotic disease, with a life cycle that involves many species of hosts, this study targeted two of the most important hosts, dogs and cats. Such studies have provided significant epidemiological information that would help evaluate the status of toxoplasmosis.

Peer review

This study provides fundamental epidemiological background regarding the prevalence of toxoplasmosis infection in dogs and cats, and at the same time raises the concerns about risk factors associated with human exposure. Presentation of data in this manuscript is easily understandable and I feel the flow is good. Over all, the presentation is good and appealing.

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10.12980/APJTB.4.2014APJTD-2014-0109

*Corresponding author: Li-Hua Gao, Department of Animal Husbandry and Veterinary Medicine, Jiangsu Polytechnic College of Agriculture and Forestry, Jurong, Jiangsu, 212400, PR China.

#Authors have the same contribution to this paper.

Tel: +86-13625265069

Fax: +86-511-87290000

E-mail: gaolihua660306@sina.com

Foundation Project: Supported by the Access Engineers of Higher Vocational Institutions in Jiangsu Province (Project No. 2013FG042) and Jiangsu Polytechnic College of Agriculture and Forestry.

Article history:

Received 16 Jun 2014

Received in revised form 21 Jun, 2nd revised form 26 Jun, 3rd revised form 1 Jul 2014

Accepted 6 Aug 2014

Available online 25 Aug 2014

Methods:Sera from 160 dogs and 116 cats from Zhenjiang City were tested for anti-T. gondii antibodies using ELISA. The seropositivity by area of activity, sex and age was analyzed.

Results:Overall, 21 dogs (13.1%) and 24 cats (20.7%) had antibodies to T. gondii. The infection rate in stray dogs (38.7%) and cats (28.6%) was significantly higher (P＜0.05) than in household dogs (6.9%) and cats (18.2%). The seroprevalence in male dogs (14.8%) and cats (21.05%) were slightly higher than their female counterparts (11.4% in dogs and 20.0% in cats), but were not significantly differenent (P＞0.05). A high proportion of dogs at 3 to 6 years of age were positive to T. gondii (20.0%) while cats with relatively high seropositivity rates were at 0 to 1 year of age (33.3%).

Conclusions:The prevalence of T. gondii infection in dogs and cats in Zhenjiang City was high, which is probably the main source of T. gondii infection in this area.