Diagnosis of Swine Toxoplasmosis by PCR and Genotyping of Toxoplasma gondii from pigs in Henan, Central China

Abstract

Background: Toxoplasma gondii, a widely prevalent protozoan parasite, causes serious toxoplasmosis infections in humans and other animals. Among livestock, pigs are susceptible to T. gondii infection. Despite Henan being one of the biggest pig-raising provinces in China, little information exists on the epidemiology of toxoplasmosis in this location. Therefore, we molecularly characterized DNA samples from pigs in Henan. A total of 1647 samples, including 952 from dead piglets, 478 from seriously sick fattening pigs and 217 from abortion sows, were collected from different animal hospitals or pig farms from 10 different cities in Henan (2006-2008). Each pig corresponded to a separate pig farm. DNA was extracted from 3 to 5 g of the most severely affected pig tissue (liver, spleen, lung, hilar lymph nodes and amniotic fluid) after postmortem examination. The presence of the T. gondii B1 gene was detected using nested polymerase chain reactions (PCR). Genotyping was performed directly on DNA from the PCR-positive tissue samples using 11 PCR restriction fragment length polymorphism markers (SAG1, 5'- and 3'-SAG2, alternative SAG2, SAG3, BTUB, GRA6, L358, PK1, c22-8, c29-2, and Apico).

Results: Of all samples, thirty-four were positive for the T. gondii B1 gene (2.06%, 95% CI: 1.86%-2.26%) from four cities, including 31 from NanYang city, one (PgXY 1) from Xinyang City, one (PgZZ 1) from Zhengzhou City and one (PgZK1) from Zhoukou City. The prevalence was found to be highest in piglets than in fattening pigs and sows. And the difference was statistically significant (P<0.01). The following 32 samples were genotyped with complete data: 13 hilar lymph node tissue samples, seven liver tissue samples, seven lung tissue samples, four spleen tissue samples, and one amniotic fluid sample. Only one genotype, belonging to ToxoDB Genotype #9, was identified.

Conclusions: This is the first large-scale survey molecularly characterizing T. gondii from pigs in Henan. The results of the present study revealed that T. gondii infection is present in swine in Henan and is a potential source of foodborne toxoplasmosis in the investigated areas. Implementation of effective control measures for T. gondii to reduce the chance of zoonotic toxoplasmosis spreading from pig farms may be warranted. The results show that the ToxoDB #9 genotype may be the dominant T. gondii lineage in mainland China. These findings strengthen the limited Chinese T. gondii epidemiology database.

Keywords: Diagnosis; Henan; Molecular characterization; PCR assay; Swine; Toxoplasmosis.

Fig. 1

Map showing Henan(HN), central China, where pigs from different animal hospitals or farms were sampled from Anyang City (AY), Xinxiang City (XX), Jiaozuo City (JZ), Luoyang City (LY), Zhengzhou City (ZZ), Pingdingshan City (PDS), Luohe City (LH), Zhoukou City (ZK), Nanyang City (NY) and Xinyang City (XY). The shadowed area of Henan is enlarged for clarity. The figure was generated using the softwares of MapInfo Professional 7.0, Microsoft PowerPoint 2007 and Adobe Photoshop 13.0