High prevalence of Clonorchis sinensis infection in Guangxi, Southern China.

BACKGROUND: Soil-transmitted helminths (STHs), such as hookworm, roundworm and whipworm, and food-borne trematodiases, including Clonorchis sinensis, remain a public health problem worldwide, especially in tropical and subtropical regions. OBJECTIVE: We aimed to determine the current prevalence of these parasites in Guangxi, China, which is located in a subtropical region. METHODS: A cross-sectional study and a 4-year longitudinal surveillance study were carried out. Stool samples were collected and examined microscopically for parasite eggs using the modified Kato-Katz thick smear method. RESULTS: The study subjects selected using stratified random cluster sampling for the cross-sectional study and longitudinal surveillance study numbered 15,683 and 24,429, respectively. In the cross-sectional study, hookworm, roundworm, whipworm, pinworm, C. sinensis, and tapeworm were found. The total prevalence of soil-transmitted helminths (STHs) was 6.4% (95% CI, 6.0-6.8). The prevalences of C. sinensis, hookworm, roundworm, whipworm, and pinworm were 10.6%, 4.2%, 0.3%, 0.3%, and 1.8%, respectively. The prevalence of C. sinensis in males (14.0%, 95% CI, 13.3-14.8) was significantly higher than in females (7.2%, 95% CI, 6.7-7.8) (P = 0.0001). The prevalence also was significantly higher in the medical worker group (20.8%, 95% CI, 12.9-28.7) than in all other occupational groups (10.5%, 95% CI, 10.0-11.0) (P = 0.0001). The prevalence of hookworm in females (5.3%, 95% CI, 4.8-5.8) was significantly higher than in males (3.0%, 95% CI, 2.6-3.3) (P = 0.0001). In the longitudinal surveillance study, the prevalence of C. sinensis and STHs in 2016, 2017, 2018, and 2019 were 12.0%, 6.0%, 11.0%, and 10.0% and 2.6%, 2.8%, 1.5%, and 1.5%, respectively. CONCLUSIONS: Adult male and occupation of and medical workers are risk factors for infection with C. sinensis and hookworm. The prevalence rate of C. sinensis remains high while those of the other STHs are decreasing, suggesting that enhanced health education should be focused on C. sinensis in Guangxi.

Identification and Analysis of the Tegument Protein and Excretory-Secretory Products of the Carcinogenic Liver Fluke Clonorchis sinensis.

Liver fluke proteins, including excretory-secretory products (ESPs) and tegument proteins, are critical for the pathogenesis, nutrient metabolism, etiology and immune response of liver cancer. To understand the functions of various proteins in Clonorchis sinensis physiology and human clonorchiasis, the ESPs and tegument proteins of C. sinensis were identified. Supernatants containing ESPs from adult C. sinensis after culture for 6 h were harvested and concentrated. The tegument was detached using a freeze/thaw method and successively extracted using various extraction buffers. The outer surface proteins of C. sinensis were labeled with biotin, and the biotinylated proteins were purified. The ESP, tegument and labeled outer surface proteins were identified and analyzed by high-resolution LC-MS/MS. The identified proteins were compared with those of other flukes, and the protein functions associated with pathogenesis, carcinogenesis and potential vaccine antigens and drug targets were predicted and analyzed. A total of 175 proteins were identified after the 6-h culture of C. sinensis ESPs. A total of 352 tegument proteins were identified through sequential solubilization of the isolated teguments, and a subset of these proteins were localized to the surface membrane of the tegument by labeling with biotin. Thirty identified proteins, including annexins, actin and tetraspanins, were identified as potential immunomodulators and promising vaccine antigens. Interestingly, among the 352 tegument proteins, as many as 155 were enzymes, and most were oxidoreductases, hydrolases or transferases. A comparison of the outer surface proteins of C. sinensis with those of other flukes indicated that flukes have some common outer surface proteins, such as actin, tetraspanin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and annexin. Granulin, thioredoxin peroxiredoxin, carbonyl reductase 1 and cystatin were identified in the C. sinensis proteome and predicted to be related to liver disease and cancer. The analysis of the C. sinensis proteome could contribute to a more in-depth understanding of complex parasite-host relationships, improve the diagnosis of clonorchiasis and benefit research on the pathogenesis and development of novel interventions, drugs and vaccines to control C. sinensis infection.

Distribution, genetic characteristics and public health implications of Triatoma rubrofasciata, the vector of Chagas disease in Guangxi, China.

BACKGROUND: Triatomines are natural vectors of Chagas disease and are mainly prevalent in the Americas. In China, previous data from decades ago showed that there were two species of triatomine bugs, Triatoma rubrofasciata and T. sinica. However, the distribution, genetic characteristics and public health implications of triatomines in China are still relatively unknown. In order to gain knowledge on the distribution, genetic characteristics and public health implications of the triatomines in Guangxi, China, an entomological-epidemiological study and genetic research was conducted. METHODS: Different methods were used to elucidate the distribution of triatomines in Guangxi including consultations with county-level Center for Disease Prevention and Control staff and village doctors, the distribution of educational material on triatomines though the internet and social media apps such as Wechat and QQ, and conducting manual inspections and light trapping to collect triatomines. The morphological characteristics of the collected triatomines were identified under light microscopy. The mitochondrial 16S rRNA, cytochrome b (cytb) genes and nuclear 28S rRNA gene were amplified, sequenced and used in phylogenetic analyses. RESULTS: A total of 305 triatomines were captured from 54 different sites in 13 cities in Guangxi. All collected bugs were identified as T. rubrofasciata based on morphology. Most triatomine collection sites were around or inside houses. Four triatomines bite cases were observed during the investigation indicating that triatomine bites are common, the bites can cause serious anaphylaxis and skin papules and urticaria, suggesting a systemic skin response. The 16S rRNA, 28S rRNA and cytb sequence analyses of T. rubrofasciata from Guangxi and other countries showed that T. rubrofasciata sequences from different regions exhibit a high similarity, with no geographical differences. The phylogenetic tree based on the 16S rRNA and cytb genes showed that T. rubrofasciata sequences from different regions and continents were in the same cluster, indicating no differentiation among different geographical populations. CONCLUSIONS: Our study showed that T. rubrofasciata is widely distributed in Guangxi and that people are commonly bitten by this insect in some regions. This highlights the need to enhance surveillance for and control of T. rubrofasciata and to strengthen the monitoring of imported Trypanosoma cruzi in China. The 16S rRNA, 28S rRNA and cytb sequence analyses of T. rubrofasciata from different regions and continents suggested that T. rubrofasciata populations exhibit high similarity, and the clustering in the phylogenetic analyses indicates that T. rubrofasciata has a close ancestor originating in the Americas.

[Discovery of a residual focus of bancroftian filariasis after declaration of its transmission interruption in Guangxi].

OBJECTIVE: To describe the discovery of a residual foci of bancroftian filariasis in Fuchuan County where the disease was announced to have been eliminated, and reveal its epidemiologic feature. METHODS: The investigation was carried out from August 2007 to March 2008 among residents in Changtang village where the first case of filariasis was found and the neighboring villages. They were screened with two thick blood smears. Immunochromatographic technology (ICT) was conducted for those going out but returned and those in surrounding areas. Vector mosquitoes were collected and dissected to find filaria larvae. Historical documents were reviewed and relevant people were interviewed. RESULTS: In Changtang administrative village, 1052 residents were screened and 19 cases with microfilaremia were found in 2 natural villages, with a Mf-positive rate of 1.8% (5.1% in Gangshang and 1.4% in Yinshan respectively). No Mf-positive case was found in 4119 residents screened in other 3 villages. The average microfilaria density in the 19 cases was 17.37/60 +/- 1 blood. All the 19 cases belonged to 12 families, and 13 cases were relatives to each other, which showed a feature of spatial clustering and family clustering. More patients were identified in the age groups of 20-29 and 50-59, and 57.9% of them were older than 50 years. No larvae were found in 54 Culex pipiens fatigans dissected. CONCLUSION: The Changtang village is identified as a residual focus of bancroftian filariasis with a low, limited endemicity. More cases have been among the elderly with a low average microfilaremia.