Taxonomical insights and ecology of sandfly (Diptera, Psychodidae) species in six provinces of Northern Vietnam.

We studied sandfly (Diptera: Psychodidae) populations in six provinces of Vietnam. This work explores the diversity of sandfly species according to the province, as well as environment, and updated information on public health since leishmaniasis cases were reported in two provinces. Sandflies were collected using 428 CDC light traps from May 30 to October 13, 2016 and identified based on the morphology of the cibarium, pharynx and/or male genitalia or female spermathecae. A total of 2585 sandflies belonging to five genera and 13 identified species were collected. The main species were: the Sergentomyia barraudi group (12.53%), Se. sylvatica (9.63%) and Phlebotomus stantoni (3.95%). In all, 294 Sergentomyia specimens classified as Se. sp2 and Se. sp3 and a heterogeneous group, herein called Se. und_sp., showed unknown morphological characteristics requiring further studies. We provide detailed comments about morphological description and taxonomical identification in order to help standardization of sandfly classification in Southeast Asia. We observed differentiation according to the provinces in terms of density and species richness, with Lang Son having the highest density and Ninh Binh having the highest species richness. The majority of specimens were collected in rock caves and outdoors, suggesting mainly cavernicolous and exophilic characters of sandfly species in Northern Vietnam. However, specimens were also collected in intra- and peri-domiciliary sites. It is worth noting that Ph. stantoni was the main species found in dog sheds and indoors, and in particular in a leishmaniasis patient's house.

TITLE: Aperçu taxonomique et écologie des espèces de phlébotomes (Diptera, Psychodidae) dans six provinces du nord du Vietnam. ABSTRACT: Nous avons étudié les populations de phlébotomes (Diptera : Psychodidae) dans six provinces du Vietnam. Ce travail explore la diversité des espèces de phlébotomes selon les provinces, les environnements et les informations mises à jour sur la santé publique depuis que des cas de leishmanioses ont été signalés dans deux provinces. Des phlébotomes ont été collectés à l'aide de 428 pièges lumineux CDC du 30 mai au 13 octobre 2016 et identifiés sur la base de la morphologie du cibarium, du pharynx et/ou des organes génitaux des mâles ou des spermathèques des femelles. Au total, 2585 phlébotomes, appartenant à cinq genres et 13 espèces identifiées, ont été collectés. Les principales espèces étaient : le groupe Sergentomyia barraudi (12,53 %), Se. sylvatica (9,63 %) et Phlebotomus stantoni (3,95 %). 294 spécimens de Sergentomyia classés comme Se. sp2 et Se. sp3 et un groupe hétérogène ici appelé Se. und_sp. ont montré des caractéristiques morphologiques inconnues nécessitant des études complémentaires. Nous fournissons des commentaires détaillés sur la description morphologique et l'identification taxonomique afin d'aider à la normalisation de la classification des phlébotomes en Asie du Sud-Est. Nous avons observé une différenciation selon les provinces en termes de densité et de richesse en espèces, avec Lang Son ayant la plus forte densité et Ninh Binh ayant la plus grande richesse en espèces. La majorité des spécimens ont été collectés dans des grottes rocheuses et à l'extérieur, suggérant principalement des caractères cavernicoles et exophiles des espèces de phlébotomes du nord du Vietnam. Cependant, des spécimens ont également été collectés dans des sites intra et péri-domiciliaires. Il convient de noter que Ph. stantoni était la principale espèce trouvée dans les abris pour chiens et à l'intérieur, notamment dans la maison d'un patient atteint de leishmaniose.

Field evaluation of the establishment potential of wMelPop Wolbachia in Australia and Vietnam for dengue control.

BACKGROUND: Introduced Wolbachia bacteria can influence the susceptibility of Aedes aegypti mosquitoes to arboviral infections as well as having detrimental effects on host fitness. Previous field trials demonstrated that the wMel strain of Wolbachia effectively and durably invades Ae. aegypti populations. Here we report on trials of a second strain, wMelPop-PGYP Wolbachia, in field sites in northern Australia (Machans Beach and Babinda) and central Vietnam (Tri Nguyen, Hon Mieu Island), each with contrasting natural Ae. aegypti densities. METHODS: Mosquitoes were released at the adult or pupal stages for different lengths of time at the sites depending on changes in Wolbachia frequency as assessed through PCR assays of material collected through Biogents-Sentinel (BG-S) traps and ovitraps. Adult numbers were also monitored through BG-S traps. Changes in Wolbachia frequency were compared across hamlets or house blocks. RESULTS: Releases of adult wMelPop-Ae. aegypti resulted in the transient invasion of wMelPop in all three field sites. Invasion at the Australian sites was heterogeneous, reflecting a slower rate of invasion in locations where background mosquito numbers were high. In contrast, invasion across Tri Nguyen was relatively uniform. After cessation of releases, the frequency of wMelPop declined in all sites, most rapidly in Babinda and Tri Nguyen. Within Machans Beach the rate of decrease varied among areas, and wMelPop was detected for several months in an area with a relatively low mosquito density. CONCLUSIONS: These findings highlight challenges associated with releasing Wolbachia-Ae. aegypti combinations with low fitness, albeit strong virus interference properties, as a means of sustainable control of dengue virus transmission.

New strategy against Aedes aegypti in Vietnam.

The container-breeding mosquito, Aedes aegypti, is the major global vector of dengue viruses, causing around 50 million infections annually. We have developed a mosquito control strategy, incorporating four elements: (1) a combined vertical and horizontal approach that depends on community understanding; (2) prioritised control according to the larval productivity of major habitat types; (3) use of predacious copepods of the genus Mesocyclops as a biological control agent; delivered by (4) community activities of health volunteers, schools, and the public. We have previously reported that, from 1998 to 2003, community-based vector control had resulted in A aegypti elimination in six of nine communes, with only small numbers of larvae detected in the others. Here, we report eradication in two further communes and, as a result of local expansion after the project in three northern provinces, elimination from 32 of 37 communes (309730 people). As a result, no dengue cases have been detected in any commune since 2002. These findings suggest that this strategy is sustainable in Vietnam and applicable where the major sources of A aegypti are large water storage containers.

Elimination of dengue by community programs using Mesocyclops(Copepoda) against Aedes aegypti in central Vietnam.

From September 2000 to June 2003, a community-based program for dengue control using local predacious copepods of the genus Mesocyclops was conducted in three rural communes in the central Vietnam provinces of Quang Nam, Quang Ngai, and Khanh Hoa. Post-project, three subsequent entomologic surveys were conducted until March 2004. The number of households and residents in the communes were 5,913 and 27,167, respectively, and dengue notification rates for these communes from 1996 were as high as 2,418.5 per 100,000 persons. Following knowledge, attitude, and practice evaluations, surveys of water storage containers indicated that Mesocyclops spp. already occurred in 3-17% and that large tanks up to 2,000 liters, 130-300-liter jars, wells, and some 220-liter metal drums were the most productive habitats for Aedes aegypti. With technical support, the programs were driven by communal management committees, health collaborators, schoolteachers, and pupils. From quantitative estimates of the standing crop of third and fourth instars from 100 households, Ae. aegypti were reduced by approximately 90% by year 1, 92.3-98.6% by year 2, and Ae. aegypti immature forms had been eliminated from two of three communes by June 2003. Similarly, from resting adult collections from 100 households, densities were reduced to 0-1 per commune. By March 2004, two communes with no larvae had small numbers but the third was negative; one adult was collected in each of two communes while one became negative. Absolute estimates of third and fourth instars at the three intervention communes and one left untreated had significant correlations (P = 0.009-< 0.001) with numbers of adults aspirated from inside houses on each of 15 survey periods. By year 1, the incidence of dengue disease in the treated communes was reduced by 76.7% compared with non-intervention communes within the same districts, and no dengue was evident in 2002 and 2003, compared with 112.8 and 14.4 cases per 100,000 at district level. Since we had similar success in northern Vietnam from 1998 to 2000, this study demonstrates that this control model is broadly acceptable and achievable at community level but vigilance is required post-project to prevent reinfestation.