Abstract
Toxoplasmosis is a disease caused by the protozoan Toxoplasma gondii which infects most genera of warm-blooded animals, including humans. The objective of this investigation is to evaluate the seroprevalence of toxoplasmosis in pigs in Chongqing Municipality, southwest China. Slaughterhouse pigs’ serum samples collected from six different regions in Chongqing were assayed for T. gondii antibodies by an indirect hemagglutination test. The average seroprevalence of T. gondii were found in 30.6% (278/908) in slaughter pigs, ranging from 21.6% to 40.9% among different sampling sites. The results indicated that toxoplasmosis in swine of Chongqing Municipality was relatively serious, and the pork may be an important source for human infection with T. gondii. Comprehensive measures are needed to strengthen further prevention and control of the disease in Chongqing.
Avoid common mistakes on your manuscript.
Introduction
Toxoplasma gondii infection is widespread in humans and other warm-blooded animals (Montoya and Liesenfeld 2004). Toxoplasmosis is an important cause of neonatal deaths and abortion in animals (Dubey and Urban 1990). Usually, undercooked pork is considered an important source of human infection for T. gondii (Dubey 2004; Torda 2001). The parasite may lead an immunocompromised person such AIDS patients or pregnant women to become seriously ill, though it rarely causes any clinic symptoms in otherwise healthy adults (Dubey and Jones 2008).
Chongqing is one of four municipalities of China where the live pig output is one of the largest in the country, and the annual output value of live pigs achieved 15.1 billion, accounting for 60.6% of the total output value of animal husbandry (National Bureau of Statistics of China 2006). Pork is the staple meat in Chongqing, however, little is known of the prevalence of T. gondii infection in the pigs in the municipality.
It was reported that T. gondii IgM and IgG antibodies and TOX-DNA in pregnant women of Chongqing were found as 7.0%, 11.0%, and 7.9%, respectively (Ding et al. 2002). The seroprevalence of TORCH (toxoplasma, rubella virus, cytomegalovirus, and herpes virus) in pregnancy women was examined by ELISA, and the Toxo-IgM positive rate was 0.8% (Yue et al. 2005). Therefore, the objective of the present survey was to examine the seroprevalence of T. gondii infection in pigs in Chongqing. The results would provide the fundamental data for the execution of prevention and control of T. gondii infection in humans and other animals in this municipality.
Materials and methods
Regions
Six different areas including Zhongxian, Rongchang, Dazu, Bishan, Jiangbei, and Beibei were selected for samples collection (Table 1). All of the above regions are the main suppliers of pork to Chongqing and the neighboring regions.
Blood samples
A total of 908 blood samples were collected from the pig slaughterhouse from the above six regions in Chongqing, and about 10 mL blood was collected from each pig before butchering. The blood samples were sent to the laboratory for serological examination and centrifuged (3,000 rpm) for 5 min, and the serum was collected to assay for antibodies to T. gondii.
Serological assay
Antibodies to T. gondii were detected in sera by an indirect hemagglutination antibody (IHA) test using a commercially available kit (Veterinary Research Institute, Jiangsu Academy of Agricultural Sciences, Nanjing, China) according to the manufacturer’s instructions; the method is a kind of national standard (GB/T 18448.2-2008) of China for detection animal toxoplasmosis. Positive and negative control sera were provided in the kit. In brief, sera were added to 96 multi-well V-bottomed polystyrene plates and diluted in a fourfold series from 1:16, 1:32, 1:64, 1:128, 1:256, 1:512, and 1:1024; the plates were shaken gently 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.
Results and discussion
From a total of 908 pigs’ blood samples, 278 (30.6%) were seropositive to T. gondii, and the prevalence rates ranged from 21.6% (Beibei) to 40.9% (Bishan). There seems to be a trend for more samples with the titer of 1:1024 (Table 1). Serological test result indicated that these pigs were likely to carry the Toxoplasma pathogen. The likely reasons for differences in prevalences among different areas could be many, such as difference in the protection and management of stray cats (which are the important final host for T. gondii) as well as difference in the management and animal welfare for pigs.
Comparing with other survey areas from neighboring provinces, the present survey data show that 30.6% is a little higher than Sichuan (29.5%) (Shu et al. 2011), and it is slightly lower than that in Guizhou (33.3%) (Ou et al. 2003) and Hubei (35.2%) (Jiang et al. 2007). The prevalence of toxoplasmosis was almost same in Chongqing and the surrounding provinces, the primary reasons could be the frequent trading of live pigs among these areas.
Anyway, the results of the present study show that T. gondii infection in pigs in Chongqing was relatively high, and consumption of pork may be a risk factor for human infection with T. gondii in this municipality. Therefore, it is important that improved integrated measures for the control toxoplasmosis should be practice to reduce the prevalence levels in the surveyed areas.
References
Ding, X.P., He, K.G., Wang, A.Q., and Yue, X.L. 2002. Investigation and analysis on abnormal pregnant women infection T.gondii in Chongqing. Chongqing Medical, 31, 246-247(in Chinese).
Dubey, J.P. 2004. Toxoplasmosis—a waterborne zoonosis. Veterinary Parasitology, 126, 57–72.
Dubey, J.P., and Jones, J.L. 2008. Toxoplasma gondii infection in humans and animals in the United States. International Journal for Parasitology, 38, 1257–1278.
Dubey, J.P., and Urban, J. F. Jr. 1990. Diagnosis of transplacentally induced toxoplasmosis in pigs.America Journal of Veterinary Research, 51, 1295–1299.
Jiang, T., He, H.S., Zhao, N.B., Han, Y.Y., and Zhao, J.L.2007. Seroprevalence of Toxoplasma gondii antibodies in pigs from some pig farm. Hubei Journal of Animal and Veterinary Sciences, 6, 22–25(in Chinese).
Montoya, J.G., and Liesenfeld, O. 2004. Toxoplasmosis. The Lancet, 363, 1965–1976.
Ou, X.Y., Long, Z.K., Peng, Y.H., Qian, D.X., and Long, W.B. 2003. Epidemiological investigation of swine toxoplasmosis in Sanhui county, Guizhou Province. Chinese Journal of Veterinary Parasitology, 11, 37(in Chinese).
Shu, F.F., Wu,D.Y., Zhou, Z.Y., Lv, R.Q., Yang, J.F., Nie, K., Duan,G.., and Zou, F.C. 2011. Seroprevalence of Toxoplasma gondii Infection in Slaughter Pigs in Sichuan, China. Journal of Animal and Veterinary Advances, 13, 1638–1639.
Torda, A. 2001. Toxoplasmosis. Are cats really the source? Australian Family Physician, 30, 743–747.
Yue, X.L., Ding, X.P., Ren, Y.Q., and Zhang, L. 2005. Clinical observation of the TORCH infection in pregnant women in Chongqing. Chinese Journal of Birth Health and Heredity, 13, 83, 93(in Chinese).
Acknowledgments
The Project is supported, in part, by the Yunnan Provincial Program for Introducing High-level Scientists (2009CI125 awarded to XQZ and FCZ), the State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (SKLVEB2011KFKT010). The authors are grateful to those staff of the Veterinary Stations in the six surveyed counties who assisted in the collection of pig blood samples.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Wu, D., Lv, R., Sun, X. et al. Seroprevalence of Toxoplasma gondii antibodies from slaughter pigs in Chongqing, China. Trop Anim Health Prod 44, 685–687 (2012). https://doi.org/10.1007/s11250-011-9965-3
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11250-011-9965-3