Seroprevalence of Toxoplasma gondii infection in dairy goats in Shaanxi Province, Northwestern China

  • Guang-Hui Zhao1, 2,

    Affiliated with

    • Miao-Tao Zhang1,

      Affiliated with

      • Li-Hui Lei3,

        Affiliated with

        • Chuan-Chuan Shang1,

          Affiliated with

          • Duo-Yao Cao1,

            Affiliated with

            • Ting-Ting Tian1,

              Affiliated with

              • Jie Li1,

                Affiliated with

                • Jun-Yan Xu1,

                  Affiliated with

                  • Yun-liang Yao1,

                    Affiliated with

                    • De-Kun Chen1Email author and

                      Affiliated with

                      • Xing-Quan Zhu2, 4, 5Email author

                        Affiliated with

                        Contributed equally
                        Parasites & Vectors20114:47

                        DOI: 10.1186/1756-3305-4-47

                        Received: 30 January 2011

                        Accepted: 1 April 2011

                        Published: 1 April 2011

                        Abstract

                        Background

                        Toxoplasma gondii is an important zoonotic pathogen causing significant human and animal health problems. Infection in dairy goats not only results in significant reproductive losses, but also represents an important source of human infection due to consumption of infected meat and milk. In the present study we report for the first time seroprevalence of T. gondii infection in Guanzhong and Saanen dairy goats in Shaanxi province, Northwestern China.

                        Results

                        Sera from 751 dairy goats from 9 farms in 6 counties were examined for T. gondii antibodies with an indirect haemagglutination (IHA) test. Antibodies to T. gondii were detected in 106 (14.1%) serum samples, with antibody titres ranging from 1:64 to 1:1024. Seropositive goats were found in all 9 farms and seroprevalences in Guanzhong (16.3%, 75/461) and Saanen (10.7%, 31/290) dairy goats were not statistically significantly different. All the factors (sex, age and location) reported in the present study affected prevalence of infection, and seroprevalence increased with age, suggesting postnatal acquisition of T. gondii infection.

                        Conclusions

                        The results of the present survey indicate that infection by T. gondii is widely prevalent in dairy goats in Shaanxi province, Northwestern China, and this has implications for prevention and control of toxoplasmosis in this province.

                        Background

                        Toxoplasma gondii can infect nearly all the warm-blooded animals, including mammals and birds throughout the world [14]. Infection in dairy goats not only results in significant reproductive losses, but also represents an important source of human infection due to consumption of infected meat and milk constituting zoonotic transmission [3, 58]. The seroprevalence of T. gondii in goats has been surveyed in many countries, and these worldwide reports were recently summarized [3]. Viable T. gondii was isolated from goats killed for human consumption [9, 10].

                        The People's Republic of China (PRC) is one of the largest producers of dairy goats in the world, and Shaanxi Province is the major dairy goat producer in the PRC. Table 1 summarizes reports of T. gondii infection in goats from the PRC because these papers were published in the Chinese language in local journals and are not easily accessible to foreign scholars. In the present study we report seroprevalence of T. gondii infection in dairy goats in Shaanxi province, Northwestern China for the first time.
                        Table 1

                        Prevalence of Toxoplasma gondii infection in goats in People's Republic of China (PRC)

                        Usage

                        Provinces/cities

                        No. tested

                        Positive (%)

                        Serologic testa

                        Cut-off value

                        Time tested (year)

                        References

                        Meat

                        Gansu (Tianzhu)

                        1028

                        26.1

                        IHA

                        1:64

                        1995

                        [11]

                        Meat

                        Yunnan (Honghe)

                        3925

                        30.8

                        IHA

                        1:64

                        Unknown

                        [12]

                        Meat

                        Beijing

                        230

                        39.1

                        PA

                        +b

                        Unknown

                        [13]

                        Meat

                        Qinghai (Datong)

                        1128

                        24.9

                        IHA

                        1:64

                        Unknown

                        [14]

                        a IHA: indirect hemagglutination test, PA: Plate agglutination.

                        b Occurrence of particle agglutination.

                        Methods

                        Study animals

                        Blood samples were obtained from 751 dairy goats in September and October, 2010 from 9 randomly selected farms in 6 counties/district in Shaanxi Province. Details of management, source and breeds of goats, and other characteristics are summarized in Table 2. Animals were farmed in extensive production systems for meat and milk and were generally kept in small herds of 20-100 animals. Natural breeding was the sole means of reproduction and goats from outside breeding stocks was rarely purchased. Goats were fed in-house with no grazing. In local practice, both Guanzhong and Saanen dairy goats were crossed with Saanen male goats, therefore, our study included only male goats for the Saanen breed. Of the 9 sampled farms, only one farm (Qianyang county) was for breeding goats.
                        Table 2

                        Factors associated with seroprevalence of Toxoplasma gondii infection in dairy goats in Shaanxi Province, Northwestern China

                        Factor

                        Category

                        No. examined

                        No. positive (%)

                        Exp (95% CI)

                        P

                        Breed

                        Saanen dairy goat

                        290

                        31 (10.7)

                        --

                         
                         

                        Guanzhong dairy goat

                        461

                        75 (16.3)

                        2.233 (0.406, 12.269)

                        0.356

                        Sex

                             
                         

                        Male

                        70

                        11 (15.7)

                        0.259 (0.080, 0.833)

                        0.023

                         

                        Female

                        681

                        95 (14.0)

                        --

                         

                        Age

                             
                         

                        <1 year

                        175

                        17 (9.7)

                        0.363 (0.189, 0.696)

                        0.696

                         

                        1-2 year

                        67

                        6 (9.0)

                        0.612 (0.227, 1.646)

                        0.331

                         

                        >2 year

                        509

                        83 (16.3)

                        --

                        0.126

                        Location (farms)

                             
                         

                        Zhuangli town, Fuping county

                        89

                        5 (5.6)

                        --

                         
                         

                        Wangliao town, Fuping county

                        114

                        42 (36.8)

                        13.031 (4.830, 35.158)

                        0.000

                         

                        Dongshangguan, Fuping county

                        126

                        19 (15.1)

                        3.105 (1.108, 8.698)

                        0.483

                         

                        Mizi town, Fuping county

                        157

                        12 (7.6)

                        1.474 (0.499, 4.349)

                        0.585

                         

                        Yangling district

                        123

                        14 (11.4)

                        5.479 (0.938, 31.997)

                        0.059

                         

                        Qianyang county

                        39

                        2 (5.1)

                        1.584 (0.195, 12.834)

                        0.667

                         

                        Fengxiang county

                        31

                        5 (16.1)

                        9.030 (1.093, 74.597)

                        0.041

                         

                        Baishui county

                        29

                        2 (6.9)

                        2.823 (0.265, 30.105)

                        0.390

                         

                        Chunhua county

                        43

                        5 (11.6)

                        5.213 (0.638, 42.576)

                        0.123

                         

                        Total

                        751

                        106 (14.1)

                          

                        Blood sampling and serological examination

                        Approximately 3 ml of blood were obtained via a jugular vein, centrifuged at 2000 g for 5 min and stored at -20°C. Antibodies to T. gondii were determined in sera using an indirect hemagglutination antibody (IHA) test with a commercially available kit (Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, China) according to the manufacturer's instructions. In brief, sera were added to 96 well V bottomed polystyrene plates, and diluted in a four-fold series from 1:4 to 1:2048. The plates were shaken for 2 min and then incubated at 37°C for 2 h without shaking. The test was considered positive when a layer of agglutinated erythrocytes was formed in wells at dilutions of 1:64 or higher, and positive and negative controls were included in each test.

                        Statistical analysis

                        Differences in seroprevalence of infected goats between the two breeds and among associated factors were analyzed using the binary logistic regression in SPSS for Windows (Release 17.0 standard version, SPSS Inc., Chicago, IL, USA), 95% confidence intervals (CI) are given. The Differences between levels within factors and interactions were considered to be statistically significant and highly significant when P < 0.05 and P < 0.01, respectively.

                        Results and discussion

                        Antibodies to T. gondii were found in 106 (14.1%) of 751 goats with titres of 1:64 in 79 dairy goats, 1:256 in 16 dairy goats and 1:1024 in 11 dairy goats. Both Saanen and Guanzhong dairy goats were positive for T. gondii antibody, with higher prevalence in Guanzhong dairy goats than in Saanen dairy goats. The binary logistic regression showed that all the factors (sex, age and location) reported in the present study affected prevalence of infection. The seroprevalence in male goats (15.7%) was higher than that in females (14.0%), and the difference was statistically significant (Exp = 0.259, CI = 0.080-0.833, P = 0.023) (Table 2). Seroprevalence in goats increased progressively with age, and prevalence in older goats (>2-year-old) was higher than that in animals below 2-year-old. Seroprevalence at the individual farms ranged from 5.1% to 36.8% and seropositive goats were found in all 9 farms (Table 2).

                        In the present study, the overall seroprevalence was 14.1%, which was far less than other reports from the PRC (Table 1). The difference could be associated with ecological conditions, life styles of inhabitants, climates, husbandry practice and the numbers of cats and rodents present. The present study showed that the breeding dairy goats had the lowest prevalence (Table 2), possibly because breeding goats have better welfare and relatively less chance to come into contact with cats and rodents that play a significant role in the transmission of T. gondii. The Guanzhong dairy goat is a unique goat breed in Shaanxi province. The prevalence in Guanzhong dairy goats was different among individual farms, ranging from 5.6% to 36.8%, which is slightly higher than that in Saanen dairy goats. The differences may be attributed to breed differences in susceptibility to T. gondii. The present study showed that older dairy goats (>2-year-old) were more likely to be seropositive than goats under 2-year-old, which provided further evidence for the increased risk of T. gondii infection with acquisition of age through ingestion of infective oocysts from the environment.

                        Conclusions

                        The results of the present survey indicated that infection of dairy goats with T. gondii is widespread in Shaanxi Province, China, which is of public health concern and has implications for prevention and control of toxoplamosis in this province. Therefore, integrated control strategies and measures are recommended to prevent and control T. gondii infection in dairy goats.

                        Authors' information

                        1College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province 712100, PR China. 2State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, CAAS, Lanzhou, Gansu Province 730046, PR China. 3Department of Animal Husbandry and Veterinary Medicine, Beijing Vocational College of Agriculture, Beijing 102442, PR China. 4College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province 163319, PR China. 5College of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan Province 650201, PR China.

                        Notes

                        Declarations

                        Acknowledgements

                        Project support was provided in part by grants from the Special Fund for Agro-scientific Research in the Public Interest (Grant No. 201103038) to JL; the State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0723) and the Special Fund for Agro-scientific Research in the Public Interest (Grant No. 200803017) to XQZ; and the Special Funds for Talents in Northwest A & F University to GHZ.

                        Authors’ Affiliations

                        (1)
                        College of Veterinary Medicine, Northwest A & F University
                        (2)
                        State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, CAAS
                        (3)
                        Department of Animal Husbandry and Veterinary Medicine, Beijing Vocational College of Agriculture
                        (4)
                        College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University
                        (5)
                        College of Animal Science and Technology, Yunnan Agricultural University

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                        © Zhao et al; licensee BioMed Central Ltd. 2011

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