F. C. Zou

Seroprevalence of Toxoplasma gondii in pigs in Southwestern China.

The seroprevalence of toxoplasmosis in pigs was investigated in Yunnan province, Southwestern China between March 2008 and January 2009. A total of 831 serum samples were collected from 9 counties and assayed for Toxoplasma gondii antibodies by indirect haemagglutination (IHA) test. Antibodies to T. gondii were found in 16.97% (141/831) with slaughter pigs having the highest rate (22.28%), followed by breeding sows (16.59%). The results of the present survey indicated that infection with T. gondii in pigs is widely spread in China, including the Yunnan province, and is of public health concern.

Genetic variation among Clonorchis sinensis isolates from different geographic regions in China revealed by sequence analyses of four mitochondrial genes.

The present study examined sequence variation in four mitochondrial (mt) genes, namely cytochrome c oxidase subunits 1 (cox1) and 2 (cox2), and NADH dehydrogenase subunits 1 and 2 (nad1 and nad2) among Clonorchis sinensis isolates from different endemic regions in China, and their phylogenetic relationships with other zoonotic trematodes were reconstructed. A portion of the cox1 and cox2 genes (pcox1 and pcox2), and nad1 and nad2 genes (pnad1 and pnad2) were amplified separately from individual liver flukes by polymerase chain reaction (PCR) and the amplicons were subjected to sequencing from both directions. The intra-specific sequence variations within C. sinensis were 0-1.6% for pcox1, 0-1.4% for pcox2, 0-0.9% for pnad1 and 0-1.0% for pnad2. Phylogenetic analyses based on the combined sequences of pcox1, pcox2, pnad1 and pnad2 revealed that all the C. sinensis isolates grouped together and were closely related to Opisthorchis felineus. These findings revealed the existence of intra-specific variation in mitochondrial DNA (mtDNA) sequences among C. sinensis isolates from different geographic regions, and demonstrated that mtDNA sequences provide reliable genetic markers for phylogenetic studies of zoonotic trematodes.

Molluscicidal activity of the plant Eupatorium adenophorum against Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum.

Abstract The potential molluscicidal activities of aqueous extracts of Eupatorium adenophorum have recently been evaluated against Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum. The snails were continuously exposed to extracts of the leaves, roots or stems [each at concentrations of 0.27%, 0.50% and 0.86% (w/v)], with survival recorded 6, 12, 24, 30, 36, 48, 52, 58, 70, 76, 82 and 96 h after the start of the exposure. Even at the lowest concentration tested (0.27%), the leaf extract caused mortality in excess of 50% after 58 h and 100% mortality after 82 h. This extract was significantly more effective against O. hupensis than the stem or root extract (P<0.05) but there was no statistically significant difference between the root and stem extracts in their molluscicidal effects (P>0.05). These preliminary results indicate that E. adenophorum may potentially provide a new molluscicide that could give effective and environmentally-friendly control of schistosomiasis in humans and livestock. The toxicity of E. adenophorum extracts, or molluscicidal compounds isolated from such extracts, to other snail hosts of human parasites and to non-target species of aquatic life will be investigated.

Seroprevalence of Toxoplasma gondii antibodies from slaughter pigs in Chongqing, China

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.

Sequence variability in four mitochondrial genes among Bunostomum trigonocephalum isolates from four provinces in China.

The present study examined sequence variability in four mitochondrial genes, namely cytochrome c oxidase subunit (cox1), cytochrome b (cytb) and NADH dehydrogenase subunits 1 and 5 (nad1 and nad5), among Bunostomum trigonocephalum isolates from four different geographic regions in China. Ten B. trigonocephalum samples were collected from each of the four provinces (Heilongjiang, Jilin, Shaanxi and Yunnan), China. A part of the cox1 (pcox1), cytb (pcytb), nad1 and nad5 genes (pnad1 and pnad5) were amplified separately from individual hookworms by polymerase chain reaction (PCR) and were subjected to direct sequencing in order to define sequence variations and their phylogenetic relationships. The intra-specific sequence variations within B. trigonocephalum were 0-1.9% for pcox1, 0-2.0% for pcytb, 0-1.6% for pnad1 and 0-1.7% for pnad5. The A+T contents of the sequences were 69.6-70.4% (pcox1), 71.9-72.7 (pcytb), 70.4-71.1% (pnad1) and 72.0-72.6% (pnad5). However, the inter-specific sequence differences among members of the family Ancylostomatidae were significantly higher, being 12.1-14.2% for pcox1, 13.7-16.0 for cytb, 17.6-19.4 for nad1 and 16.0-21.6 for nad5. Phylogenetic analyses based on the combined partial sequences of cox1, cytb, nad1 and nad5 using three inference methods, namely Bayesian inference (Bayes), maximum likelihood (ML) and maximum parsimony (MP), revealed that all the B. trigonocephalum samples form monophyletic groups, but samples from the same geographical origin did not always cluster together, suggesting that there was no obvious geographical distinction within B. trigonocephalum based on sequences of the four mtDNA genes. These results demonstrated the existence of low-level intra-specific variation in mitochondrial DNA (mtDNA) sequences among B. trigonocephalum isolates from different geographic regions.

Variability in intron sequences of housekeeping and antigen-coding genes among Schistosoma japonicum isolates in mainland China.

The accurate characterization of Schistosoma japonicum has important implications for analyzing genetic variation and would provide basic data for disease control. Previous studies using proteins, coding sequences, and especially antigen-coding genes showed lower genetic variation among S. japonicum isolates from mainland China. Therefore, the present study focused on variations in intron sequences of housekeeping and antigen-coding genes, which may be more informative for genetic analysis. We compared sequence variation between introns of two housekeeping genes and two antigen-coding genes. All 4 genes were polymorphic among all the S. japonicum isolates in mainland China, with 103, 158, 47, and 19 polymorphic (segregating) sites per kilobase in intron sequences of Actin, FBPA, 22.6kDa antigen and GST-26, respectively. Introns of housekeeping genes were slightly more polymorphic than coding and non-coding regions of antigen-coding genes examined in the present study within or among lake/marshland and mountainous types. Phylogenetic analysis based on sequences of single gene or combined sequences of multiple genes showed no specific clustering comprising parasites from single geographical or endemic regions. These results demonstrated that introns of housekeeping and antigen-coding genes were polymorphic, but the intron sequences examined in the present study were not suitable markers for examining genetic relationship among different isolates from endemic regions in mainland China.

Seroprevalence of Mycoplasma hyopneumoniae in pigs in subtropical southern China

Enzootic pneumonia caused by Mycoplasma hyopneumoniae is a severe disease of pigs, causing significant economic losses to the pig industry worldwide, including the tropical and subtropical regions. In order to obtain the baseline prevalence of M. hyopneumoniae in pigs from intensive farms in southern China, double-sandwich enzyme-linked immunosorbent assay (ELISA) was used to detect M. hyoneumoniae antibodies in 460 pig serum samples collected from 12 administrative cities in China’s southern Guangdong province. According to the proportions of the infected animals, among the 12 intensive farms, only two of them showed no infection of M. hyoneumoniae and the seroprevalence ranged from 0% to 90%, with an averaged prevalence of 45.7%. The highest prevalence was found in breeding boars (68.8%), followed by sows (54.5%). These data showed that the infection of pigs with M. hyopneumoniae is severe, and boars might be more important carriers and transfers of M. hyoneumoniae than sows. Integrated strategies and measures should be taken to control the infection of pigs with M. hyopneumoniae in southern China.

Prevalences of Schistosoma japonicum infection in reservoir hosts in south-western China.

The human schistosomiases are major communicable parasitic diseases that, in the developing world, have public-health and socio–economic importance. Together, they affect approximately 200 million people worldwide, of whom approximately 20 million suffer from severe illness (Gryseels et al., 2006; Ribeiro-dos-Santos et al., 2006; Friedman et al., 2007). In mainland China, human schistosomiasis caused by Schistosoma japonicum was once a devastating disease that killed millions of people (Ross et al., 2001; Utzinger et al., 2005). Despite five decades of progress in the control and prevention of this problem in China, schistosomiasis is still regarded as the country’s most important parasitic zoonosis and one of the three most important communicable diseases (Guo and Yu, 2005; Zhou et al., 2005; Zhou et al., 2008). Of the three schistosome species that cause most cases of human schistosomiasis, S. japonicum is recognised as the most difficult to control because several common mammals serve as its ‘reservoir’ hosts (Utzinger et al., 2005). In China, while many wild mammals serve as natural hosts for S. japonicum, buffaloes and cattle are commonly infected and act as the main reservoir hosts for human infection (Li and Lin, 2007). As well as attracting large numbers of tourists, the province of Yunnan, in south– western China, holds more ethnic minorities than any other Chinese province. This area remains endemic for human schistosomiasis, despite the considerable progress made nationally in the control and prevention of the disease (Chen, 1999; Dong et al., 2008). Within the last decade, 15 of the 18 counties where the disease was once common in Yunnan met the national criteria for either transmission interruption (12 counties) or transmission control (Dali, Heqing and Nanjian), leaving only three counties in the province (Weishan, Eryuan and Yongsheng) where the disease remained poorly controlled. Unfortunately, over the last few years, schistosomiasis has re-emerged in some counties (such as Dali, Heqing and Nanjian) where control once appeared effective, probably because of increases in the mobility of the human populations and poor socio–economic conditions. The main aim of the present study was to evaluate the current problem posed by S. japonicum in all 18 counties of Yunnan that were formerly endemic for the parasite, by determining the prevalences of infection in the local livestock. The data collected should provide a foundation for the improved control of S. japonicum infection in the human populations and livestock of Yunnan.