The role of rice fields, fish ponds and water canals for transmission of fish-borne zoonotic trematodes in aquaculture ponds in Nam Dinh Province, Vietnam

BACKGROUND: Fish-borne zoonotic trematodes (FZT), such as Clonorchis sinensis, Opistorchis viverini (Opisthorchiidae) and intestinal trematodes of the family Heterophyidae, constitute a public health hazard in Vietnam and infections with these trematodes has been linked to consumption of raw or undercooked fish from aquaculture. The FZT transmission pathways, however, are more complicated than just the presence of intermediate snail hosts in aquaculture ponds as ponds may exchange water with surrounding habitats such as rice fields and irrigation canals and thereby these surrounding habitats may be a source of snails and cercariae and contribute to FZT infection in cultured fish. METHODS: This is a longitudinal descriptive study on selected farms (n = 30) in Nam Dinh Province which is endemic for FZT. At each farm, we sampled one pond, a small irrigation canal used to supply the pond with water, and a nearby rice field. At each of these three sites, we estimated the density of the FZT intermediate snail hosts and determined their trematode infection status. Comparative analysis was performed for the prevalence and density of FZT infections in fish and snails. RESULTS: Species of the Thiaridae, and most notably Melanoides tuberculata, the most important host species for FZT belonging to the Heterophyidae, were particularly abundant in ponds and small canals, i.e. M. tuberculata was found in 27 ponds and 13 small canals. Bithynia fuchsiana, a potential host for both Heterophyidae and Opisthorchiidae, was rarely found in fish ponds but common in rice fields. A total of 12 types of cercariae were found in the snails and pleurolophocercous cercariae, primarily FZT, constituted about 40 % of all cercarial infections. The fish species cultured were mainly carp species and Haplorchis pumilio was the dominating trematode species infecting fish. Clonorchis spp. were not recorded in any of the ponds. FZT transmission to fish was intense during the summer period (May-June to November) but less intense during the winter months (December-January) partly because cercarial emergence ceases due to the low temperature. CONCLUSION: Our findings highlight the complexity of FZT transmission within aquaculture farm settings and suggest that efforts to control these infections must take a holistic approach using interventions against all stages of the transmission cycle

MỐI QUAN HỆ DI TRUYỀN CỦA MỘT SỐ QUẦN THỂ CHIM YẾN SỐNG NGOÀI ĐẢO VÀ TRONG ĐẤT LIỀN Ở VIỆT NAM

Edible-nest Swiftlets (A. fuciphagus) create nests using their solidified saliva. The nests have long been harvested because of their high economic value. This research addresses the phylogenetic relationships of several bird populations in Vietnam based on a portion of the cytochrome b gene with 606bp in length. Phylogenetic analyses show that populations inhabiting islands and mainland belong to different subspecies of A. fuciphagus. Wild swiftlets on islands are assigned to subspecies A. f. germani, while house swiftlets (birds on mainland) are recovered as A. f. amechanus with mean genetic divergence of 1.9%. There are some specific sites for nucleotide substitutions between the two groups (group resident on islands and mainland, respectively): 36 (C-T), 93 (G-C), 96 (C-T), 117 (T-C), 306 (G-A), 468 (G-A), 489 (A-G), 531 (T-C). Our results suggest that the recently recorded house swiftlet populations (subspecies A. f. amechanus) in Vietnam are probably originated from the southern region of Southeast Asia. We recommend that future studies should include nuclear genes (chromosome genes) to evaluate cross-hybrid between the populations.TÓM TẮT Chim yến (Aerodramus fuciphagus) hiện là loài chim có khả năng tạo ra tổ chim hoàn toàn bằng nước bọt được con người khai thác với giá trị kinh tế cao. Các loài trong giống Aerodramus thuộc nhóm chim bay liên tục và rất khó phân biệt về hình thái. Những năm gần đây, số lượng chim yến làm tổ trong nhà yến ở đất liền ngày một gia tăng trải rộng các tỉnh ven biển từ Cà Mau ra tận Thanh Hóa. Phân tích trình tự một phần gen cytochrome b với chiều dài 606bp cho thấy các quần thể chim yến cư trú ngoài đảo (chim yến đảo) thuộc phân loài Aerodramus fuciphagus germani và chim yến làm tổ trong nhà ở đất liền (chim yến nhà) thuộc phân loài A. f. amechanus, vì giữa chúng có sự khác biệt về di truyền trung bình khá cao, tới 1,9%. So sánh phân tích di truyền cho thấy quần thể yến nhà A.f.amechanus ở nước ta được hình thành chủ yếu từ các quần thể chim yến khác nhau ở Thái Lan và Malaysia di cư đến trong khoảng hơn một thập kỉ qua

An internationally standardized species identification test for use on suspected seized rhinoceros horn in the illegal wildlife trade

Published by Elsevier Ireland Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).Rhinoceros (rhino) numbers have dwindled substantially over the past century. As a result, three of the five species are now considered to be critically endangered, one species is vulnerable and one species is near-threatened. Poaching has increased dramatically over the past decade due to a growing demand for rhino horn products, primarily in Asia. Improved wildlife forensic techniques, such as validated tests for species identification of seized horns, are critical to aid current enforcement and prosecution efforts and provide a deterrent to future rhino horn trafficking. Here, we present an internationally standardized species identification test based on a 230 base pair cytochrome-b region. This test improves on previous nested PCR protocols and can be used for the discrimination of samples with <20 pg of template DNA, thus suitable for DNA extracted from horn products. The assay was designed to amplify water buffalo samples, a common ‘rhino horn’ substitute, but to exclude human DNA, a common contaminant. Phylogenetic analyses using this partial cytochrome-b region resolved the five extant rhino species. Testing successfully returned a sequence and correct identification for all of the known rhino horn samples and vouchered rhino samples from museum and zoo collections, and provided species level identification for 47 out of 52 unknown samples from seizures. Validation and standardization was carried out across five different laboratories, in four different countries, demonstrating it to be an effective and reproducible test, robust to inter laboratory variation in equipment and consumables (such as PCR reagents). This is one of the first species identification tests to be internationally standardized to produce data for evidential proceedings and the first published validated test for rhinos, one of the flagship species groups of the illegal wildlife trade and for which forensic tools are urgently required. This study serves as a model for how species identification tests should be standardized and disseminated for wildlife forensic testing

Seasonal change of Lymnaeid snails intermediate host of Fasciola gigantica in North and Central Vietnam

Objective: The present study was undertaken to investigate the population dynamics of the intermediate hosts of Fasciola gigantica and the levels of infection in the snails. This would allow identifying the most important transmission periods and suggesting optimal snail control for the area. Methods: Lymnaeid snails were monthly collected by hand picking in Ha Noi (Northern Vietnam) during the period from March 2010 to December 2011 and in Binh Dinh province (Central Vietnam) during the period May and September 2012. Collected snails from different sites were identified based on morphology and the partial 16S rDNA sequence and ITS-2 sequence. Snails were examined for the presence of Fasciola larval by the crushing method and confirmation by multiplex PCR analyses with PCR primer for Fasciola gigantica cathepsin L in parallel with the snail rDNA species specific primer. Result: The density of Lymnaeid populations underwent great changes in relation to the geographical locations and seasons. In Central Vietnam, the Lymnaeid populations reached the peak in the dry/rainy season (May) and decreased sharply in rainy/dry season (September). In contrast, in Hanoi, it reached the peaks in 2 periods (February to April and August to November) of rice cultivation or early stage of growing of rice, and greatly deceased when the rice becomes fully developed. Transmission of fascioliasis in Ha Noi were high when rice cultivation is performed, while the permanent transmission can takes place through the year in Binh Dinh with peak transmission during the dry season

Morphological and Molecular Characterization of Lymnaeid Snails and Their Potential Role in Transmission of Fasciola spp. in Vietnam

Freshwater snails of the family Lymnaeidae play an important role in the transmission of fascioliasis worldwide. In Vietnam, 2 common lymnaeid species, Lymnaea swinhoei and Lymnaea viridis, can be recognized on the basis of morphology, and a third species, Lymnaea sp., is known to exist. Recent studies have raised controversy about their role in transmission of Fasciola spp. because of confusion in identification of the snail hosts. The aim of this study is, therefore, to clarify the identities of lymnaeid snails in Vietnam by a combination of morphological and molecular approaches. The molecular analyses using the second internal transcribed spacer (ITS2) of the nuclear ribosomal DNA clearly showed that lymnaeids in Vietnam include 3 species, Austropeplea viridis (morphologically identified as L. viridis), Radix auricularia (morphologically identified as L. swinhoei) and Radix rubiginosa (morphologically identified as Lymnaea sp.). R. rubiginosa is a new record for Vietnam. Among them, only A. viridis was found to be infected with Fasciola spp. These results provide a new insight into lymnaeid snails in Vietnam. Identification of lymnaeid snails in Vietnam and their role in the liver fluke transmission should be further investigated

Correction: A rapid multiplex PCR assay for presumptive species identification of rhinoceros horns and its implementation in Vietnam.

[This corrects the article DOI: 10.1371/journal.pone.0198565.]

A rapid multiplex PCR assay for presumptive species identification of rhinoceros horns and its implementation in Vietnam

<div><p>Rhinoceros (rhinos) have suffered a dramatic increase in poaching over the past decade due to the growing demand for rhino horn products in Asia. One way to reverse this trend is to enhance enforcement and intelligence gathering tools used for species identification of horns, in particular making them fast, inexpensive and accurate. Traditionally, species identification tests are based on DNA sequence data, which, depending on laboratory resources, can be either time or cost prohibitive. This study presents a rapid rhino species identification test, utilizing species-specific primers within the cytochrome b gene multiplexed in a single reaction, with a presumptive species identification based on the length of the resultant amplicon. This multiplex PCR assay can provide a presumptive species identification result in less than 24 hours. Sequence-based definitive testing can be conducted if/when required (e.g. court purposes). This work also presents an actual casework scenario in which the presumptive test was successfully utlitised, in concert with sequence-based definitive testing. The test was carried out on seized suspected rhino horns tested at the Institute of Ecology and Biological Resources, the CITES mandated laboratory in Vietnam, a country that is known to be a major source of demand for rhino horns. This test represents the basis for which future ‘rapid species identification tests’ can be trialed.</p></div

Multiplex PCR assay protocol: Identifying an unknown rhino specimen.

<p>Multiplex PCR assay protocol: Identifying an unknown rhino specimen.</p