弓形虫生活史.doc

ORIGINAL ARTICLE

Seroprevalence of Toxoplasma gondii Infection in Stray and Household Cats in Guangzhou, China

H. Zhang1, D. H. Zhou1, P. Zhou1, Z. R. Lun2, X. G. Chen3, R. Q. Lin1,
Z. G. Yuan1 and X. Q. Zhu1

1 Laboratory of Parasitology, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Street, Tianhe District, Guangzhou, Guangdong Province 510642, People’s Republic of China
2 Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, Guangdong Province 510275, People’s Republic of China
3 Department of Parasitology, School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, Guangdong Province 510515, People’s Republic of China

Running Head: Toxoplasma gondii infection in cats in Guangzhou, China

Correspondence:
X.Q. Zhu. College of Veterinary Medicine, South China Agricultural University, 483 Wushan Street, Tianhe District, Guangzhou, Guangdong Province 510642, People’s Republic of China. Tel: [phone]; Fax: [phone];
E-mail: xingquanzh@

Impacts

l This article shows new figures on the present situation of Toxoplasma gondii infection in stray and household cats in metropolitan Guangzhou, China.
l The data presented provide the most comprehensive picture of the prevalence of T. gondii in stray and household cats in Guangzhou, which also indicates the zoonotic significance of the prevalence.
l The data presented provide “base-line” information for assessing the effectiveness of future control strategies against T. gondii infection in cats in Guangzhou, China.
Summary

The prevalence of anti-Toxoplasma gondii specific IgG in stray and household cats in Guangzhou, China was determined by ELISA on serum samples from 206 cats (117 strays and 89 households), and the overall infection rate was 25.24%. The infection rate in stray cats (30.77%) was significantly higher (p < 0.05) than in household cats (17.98%). The rate of infection between male and female cats of both groups was not significantly different (p≥0.05), 28.13% versus 32.61% for male and female in stray cats, respectively, and 18% versus 17.95% in household cats. The present investigation demonstrated that the prevalence of T. gondii infection in cats in Guangzhou was high, especially in stray cats, which are probably the main source of T. gondii infection in this area. Integrated control strategies and measures should be implemented to prevent and control T. gondii infection in both stray and household cats, which will have significant implications for the control of human infection with T. gondii.

Keywords:
Cat; ELISA; Guangzhou; Seroepidemiology; Toxoplasma gondii; Toxoplasmosis
Introduction
Toxoplasma gondii is an obligate intracellular protozoa parasite that can infect a variety of cell types from a wide range of mammals and birds throughout the world, including humans and nonhuman primates (Jacobs et al. 1998). T. gondii infection does not usually produce clinical symsptoms. However, the primary infection during pregnancy in women and animals may cause abortion, fetal abnormalities or prenatal death (Cook et al., 2000). More importantly, T. gondii infection is considered one of the main reasons of death for the AIDS patients and other immunocompromised patients (Montoya and Liesenfeld, 2004).
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 (Dubey, 1994) in their faeces. It is generally suggested that cats probably play a major role in transmitting T. gondii through environments contaminated by faeces. It is not convenient and may have difficulty in detecting T. gondii oocysts in faecal examination of cats. Therefore, serologic investigation of cats is important for determining the epidemiological significance of T. gondii infection.
Antibodies to T. gondii have been reported in cats worldwide. There have also been some surveys of T. gondii infections in cats in some provinces of China in recent years (Lu et al. 1997; Yu et al., 2006; Yuan et al. 2004; unfortunately, these reports were published only in the Chinese language). However, the difference of T. gondii infection between stray and household cats and the infection rates between male ad female cats are not quite clear. In order to provide a foundation for the improved control of T. gondii infection in cats, the aim of the present investigation was to estimate the prevalence of T. gondii in stray and household cats in metropolitan Guangzhou, China.

Material and methods
Animals
Biometric data for cats including age, sex and lifestyle were recorded. The information about household cats was taken from the owners and the information about stray cats was estimated based on body condition and by examining dentition.

Blood sampling and serum preparation

Blood samples (1.5 ml) were collected from each cat into sterile plain tube by jugular puncture. The samples were left to clot at room temperature for 3 h and then centrifuged at 800 g for 10 min. Each serum sample was transferred into a 0.5 ml sterile tube and preserved at –20℃ until needed for ELISA.
Determination of antibodies to T. gondii
Antibodies to T. gondii were determined using the CIVTEST T. gondii ELISA Kit (Shenzhen, China) according to the manufacturer’s instructions. Positive and negative control sera were provided in the kit. The tests were performed in the Veterinary College of South China Agricultural University. Briefly, the T. gondii specific 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).
A relative rate percent (IRPC) value was obtained using the following formula:

The sera were considered negative to T. gondii if the IRPC < 2.1, and positive if IRPC > 2.1. It is to take as 0.7 when the value (meanOD450 negative control - meanOD450 blank control) was less than 0.7.
Statistical analysis
Differences in the seroprevalence of infected cats between stray and household groups, between male and female cats were analyzed using Chi Square Test in SPSS for Windows, (Release 11.0 standard version, SPSS Inc.). The correlation between the rates of infection in different age groups was calculated with Excel (Microsoft® Excel 2003).
Results and discussion
In this investigation, the ELISA method was utilized due to the ease of its application, and its high sensitivity and specificity when compared with other test methods (Lappin and Powell, 1991). In this study, 206 cats (117 households and 89 strays were examined. Of these, 82 were male, 85 were female and 39 unknown sex (Table 1). As shown in Table 1, the overall seroprevalence rate was 25.24%. Seroprevalence for all different groups was 30.77% in stray cats and 17.98% in household cats (Table 1), and ranging from 12.50% to 30.77% in different age groups (Table 2).
The seroprevalence of T. gondii in cats has been studied in many countries. In the present study, the overall seroprevalence in cats was 25.24%, which was lower than that reported in other countries (Miro et al., 2004; Haddadzadeh et al., 2006), and in Shanghai and Hebei province in China (Lu et al. 1997; Yuan et al. 2004), but similar to that reported in Beijing (Yu et al., 2006).
In the present investigation, although both groups of cats were infected with T. gondii, the seroprevalence of infection in stray cats (30.77%) was significantly higher (p < 0.05) than that of household cats (17.98%). This is comparable to the results of Haddadzadeh et al. (2006), which showed a significant difference between strays (a seroprevalence of 90%) and household cats (36%) in Tehran, Iran. Results obtained by Gauss et al. (2003) also found significant differences, with a seroprevalence of 51.9% in stray cats, compared to 34.8% in household cats in Barcelona, Spain. The higher seroprevalence in stray and farm cats than in household cats may due to the hunting habits of the stray groups, and their diet includs wild birds, rodents, and Toxoplasma-infected placentas and stillborn fetuses (Frenkel 1990; Hill et al. 2000). However, studies done in the United States did not show significant differences between household cats and stray cats (Hill et al., 2000; DeFeo et al., 2002).
Many studies have shown that sex is not considered to be a determining factor for infection with T. gondii. For example, Sumner and Ackland (1999) tested 103 serum samples from domestic cats in Melbourne, Australia using ELISA and found no significant differences in the T. gondii antibody titres between males and females. Similar findings were reported by Haddadzadeh et al. (2006) in Iran. Our results show that the infection rate between male and female is different (Table 1), with prevalence in male cats being 21.95% (18 of 82), and the prevalence in female cats being 25.88% (22 of 85), but the difference was not significant (p≥0.05) (Table 1). However, there was a significantly higher seroprevalence in male strays than in females reported by Miró et al. (2004).
Amongst cats whose ages were known, a significantly higher (30.77%) prevalence of infection was detected in >3 years category of cats compared with a seropositive rate of 12.50% in cats <1 years old. As shown in table 2, seroprevalence varies in different age groups, ranging from 12.50% to 30.77%. The difference in prevalence found with respect to age (adults versus juveniles) coincides with other studies where higher prevalence is observed in the adult group than in the juvenile one (Smith et al., 1992; Gauss et al., 2003), showing that with the increase of age the risk of exposure to T. gondii increases (Frenkel, 1990; Hill et al., 2000).

Conclusions

The present investigation revealed that the prevalence of T. gondii infection in cats in Guangzhou was quite higher, especially in stray cats, which are probably the main source of T. gondii infection in this area. Integrated control strategies and measures should be implemented to prevent and control T. gondii infection in both stray and household cats, which will have significant implications for the control of human infection with T gondii.

Acknowledgements

This work is supported, in part, by grants from the National Basic Research Program of China (Grant No. 2007CB116301), the National Special Research Programs for Non-Profit Trades (Agriculture) (Grant No. 200803017), the Key Research Programs in Natural Sciences for Institutions of Higher Education in Guangdong Province (Grant No. 06Z004), and the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0723).

References

Cook, A. J., R. E. Gilbert, W. Buffolano, J. Zufferey, E. Petersen, P. A. Jenum, W. Foulon, A. E. Semprini, and D. T. Dunn, 2000: Sources of Toxoplasma infection in pregnant women: European multicentre case-control study. Br. Med. J. 312, 142–147.
DeFeo, M. L., J. P. Dubey, T. N. Mather, and R. C. Rhodes III, 2002: Epidemiologic investigation of seroprevalence of antibodies to Toxoplasma gondii in cats and rodents. Am. J. Vet. Res. 63, 1714–1717.
Dubey, J. P., 1994: Toxoplasmosis. J. Am. Vet. Med. Assoc. 205, 1593–1598.
Frenkel, J. K., 1990: Transmission of toxoplasmosis and the role of immunity in limiting transmission and illness. J. Am. Vet. Med. Assoc. 196, 233–240.
Gauss, C. B., S Almeria, A. Ortuno, F. Garcia, and J. P. Dubey, 2003: Seroprevalence of Toxoplasma gondii antibodies in domestic cats from Barcelona, Spain. J. Parasitol. 89, 1067–1068.
Haddadzadeh, H. R., P. Khazraiinia, M. Aslani, M. Rezaeian, S. Jamshidi, M. Taheri, and A. Bahonar, 2006: Seroprevalence of Toxoplasma gondii infection in stray and household cats in Tehran. Vet. Parasitol. 138, 211–216.
Hill, S. L., J. M. Cheney, G. F. Taton-Allen, J. S. Reif, C. Bruns, and M. R. Lappin, 2000: Prevalence of enteric zoonotic organisms in cats. J. Am. Vet. Med. Assoc. 216, 687–692.
Jacobs, D., J. F. Dubremetz, A. Loyens, F. Bosman, and E. Saman, 1998: Identification and heterologous expression of a new dense granule protein (GRA7) from Toxoplasma gondii. Mol. Biochem. Parasitol. 91, 237–249.
Lappin, M. R., and C. C. Powell, 1991: Comparison of latex agglutination, indirect hemagglutination, and ELISA techniques for the detection of Toxoplasma gondii-specific antibodies in the serum of cats. J. Vet. Intern. Med. 5, 299–301.
Lu, Q., A. M. Huang, Y. M. Yang, H. Z. Yang, and J. H. Yang, 1997: Serological investigation of Toxoplasma gondii infection in pet cats in Shanghai. Chin. J. Zoon. 13 (2), 69 (in Chinese).
Miró, G., A. Montoya, S. Jimenez, C. Frisuelos, M. Mateo, and I. Fuentes, 2004: Prevalence of antibodies to Toxoplasma gondii and intestinal parasites in stray, farm and household cats in Spain. Vet. Parasitol. 126, 249–255.
Montoya, J. G., and O. Liesenfeld, 2004: Toxoplasmosis. The Lancet 363, 1965–1976.
Smith, K. E., J. J. Zimmerman, S. Patton, G. W. Beran, and H. T. Hill, 1992: The epidemiology of toxoplasmosis on Iowa swine farms with an emphasis on the roles of free-living mammals. Vet. Parasitol. 42, 199–211.
Sumner, B., and M. L. Ackland, 1999: Toxoplasma gondii antibody in domestic cats in Melbourne. Aust. Vet. J. 77, 447–449.
Yu, Y. L., L. J. Fu, M. Wang, 2006: Serological survey of Toxoplasma gondii infection in dogs and cats in Beijing. Chin. J. Vet. Med. 42, 7–9 (in Chinese).
Yuan, W. Y., K. Ma, and H. L. Yang, 2004: Survey of Toxoplasma infection in animals in Hebei province. Chin. J. Schisto. Cont. 16, 72–76 (in Chinese).

Table 1. Prevalence of antibodies to Toxoplasma gondii in stray and household cats by gender

Gender Stray cats Household cats Total cats
Total Positive Total Positive Total Positive
No. No. % No. No. % No. No. %
_________________________________________________________________________________
Male 32 9 28.13 50 9 18.00 82 18 21.95
Female 46 15 32.61 39 7 17.95 85 22 25.88
Unknown 39 12 30.77 0 0 0 39 12 30.77
Total 117 36 30.77 89 16 17.98 206 52 25.24

Table 2. Prevalence of antibodies to Toxoplasma gondii in stray and household cats by ages