Abstract: The present investigation aimed to examine the prevalence of Chlamydia infection in pigs in Guangdong Province, Southern China. Between March 2008 and May 2009, a total of 1,017 serum samples were collected from 15 intensive farms, which are distributed in 12 administrative cities of Guangdong Province and assayed for Chlamydia antibodies by Indirect Hemagglutination Assay (IHA). The results showed that almost all of the investigated farms showed seroprevalence (93.33%, 14/15). The average seroprevalence of pigs with Chlamydia antibodies was 30.78% (ranged between 0-88%) with breeding boars having the highest prevalence (63.38%, 45/71), which was followed by breeding sows (41.10%, 60/146) and fattening pigs (36.25%, 29/80). These results indicated that prevalence of Chlamydia infection in pigs from intensive farms in Southern China is high, therefore integrated and improved control strategies and measures should be implemented to prevent and control Chlamydia infection in pigs.

INTRODUCTION

Chlamydia sp. is an obligate intracellular infectious agent with a broad host spectrum and causes a wide range of diseases including enteritis, perinatal mortality, pneumonia and reproductive disorders, particularly abortion and endometritis in humans and Chlamydia abortion syndrome in animals, such as abortion, stillbirth and fetal mummification (Kauffold et al., 2006; Zhong, 2009).

It also causes serious diseases in pigs including epididymitis and vesiculitis in breeding boars, vaginitis and endometritis in breeding sows, chronic pneumonia and keratitis in piglets and death in young pigs (Busch et al., 2000; Longbottom, 2004; Pantchev et al., 2009; Reinhold et al., 2009).

Prevalence of Chlamydia infection in pigs has been reported in many countries such as Australia, Germany, Switzerland (Eggemann et al., 2000; Vanrompay et al., 2004; Kauffold et al., 2006; Pantchev et al., 2009) and in a number of provinces in China (Cao and Zhang, 2007; He et al., 1995; Wang and Zhou, 2009), while there was limited investigations in South China. Guangdong Province is located in southern China, which is the largest producer of intensively raised pigs in China and a significant proportion of the pigs were sold to Hong Kong and Macao Special Administrative Regions of China for human consumption. The objective of the present investigation was to examine the seroprevalence of Chlamydia infection in pigs in Guangdong Province and the expected results would provide base-line data for the improved prevention and control of swine infection with Chlamydia.

MATERIALS AND METHODS

Pig serum samples: From March 2008-May 2009, a total of 1,017 pig blood samples were collected from 15 intensive farms distributed in 12 administrative cities of Guangdong Province, including 71 breeding boars, 146 breeding sows, 113 growing pigs, 80 fattening pigs, 55 piglets and 552 slaughter pigs. Serum samples were obtained by centrifugation at 3,000 g for 10 min and stored at -20 C until analysis by Indirect Hemagglutination Assay (IHA).

Detection reagents: Pig antibodies to Chlamydia were determined using a commercially marketed IHA kit purchased from Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences.

Detection procedure: The detection procedure followed the manufacturer’s instructions. In brief, 75 μL of IHA dilution solution was transferred into a 96-well V bottomed reaction plate with 25 μL of serum sample added and mixed gently with pipette. About 25 μL of the mixture was 4-fold gradually diluted into another 2 holes and 25 μL mixture in the third hole was discarded at last to maintain 75 μL system. The dilution in the 3 wells was 1:4, 1:16 and 1:64, respectively. Positive, negative and blank controls were included at the same plate. After 25 μL Chlamydia antigen was added to each well, the plate was shaken slightly with a vibrator for 2 min followed by incubation at 37°C for 2 h. The test was considered positive, when a layer of agglutinated erythrocytes was formed in wells at dilutions of 1:16 or higher.

RESULTS AND DISCUSSION

Prevalence of Chlamydia infection in different farms: The survey of pigs from 15 different farms by IHA showed that only one farm (Zengcheng) was Chlamydia negative, while the others were positive (93.33%, 14/15). Prevalence of pigs with Chlamydia infection was 30.8% in average and 0-88% in range. Huazhou farm had the highest prevalence of 88%, which was followed by Qingyuan and Jiangmen farms with prevalence of 66.18 and 50.82%, respectively. Three cities named Zengcheng (0), Lianjiang (1.59) and Yunfu (1.79%) had low prevalence (Table 1).

Prevalence of Chlamydia infection in different categories of pigs: Among the 1,017 tested pig serum samples, breeding boars showed the highest prevalence of 63.38%, followed by breeding sows (41.10%) and the fatting pigs (36.25%). The growing pigs had the lowest prevalence of 6.19% (Table 2).

The prevalence of Chlamydia infection in pigs in southern China’s Guangdong Province (30.78%) reported in the present study was lower than that of Henan (54.1%) (Lang et al., 2005), similar to that of Hubei (31.77%) (Qiu et al., 1998) and Gansu (34.4%) (Gao et al., 2003) but higher than that of Ningxia (24.14%) (He et al., 1995).

The investigation revealed that the prevalence of Chlamydia infection in pigs in southern China is high, especially in breeding boars. Previous studies have shown that Chlamydia could spread through semen and pigs can also be infected by contaminated faeces. The high prevalence in breeding boars may cause the wide transmission of Chlamydia in breeding sows and other pigs, similar to what have been observed in cattle and horses (Kauffold et al., 2006).

Table 1:	Prevalence of Chlamydia infection in different pig farms examined by Indirect Hemagglutination Assay (IHA)

Table 2:	Prevalence of Chlamydia infection in different categories of pigs by Indirect Hemagglutination Assay (IHA)

CONCLUSION

The results of the present investigation indicated that prevalence of Chlamydia infection in pigs from intensive farms in southern China is high, in particular in breeding boars. Therefore, integrated and improved control strategies and measures should be implemented to prevent and control Chlamydia infection in pigs.

ACKNOWLEDGEMENTS

Research support was provided in part by the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0723) and the State Key Laboratory of Veterinary Etiological Biology to XQZ and China Postdoctoral Science Foundation (Grant No. 20090460064) to MJX.