Thekhawet Weluwanarak

Seasonal abundance and potential of Japanese encephalitis virus infection in mosquitoes at the nesting colony of ardeid birds, Thailand

OBJECTIVE To investigate the abundance and seasonal dynamics of mosquitoes, and to detect Japanese encephalitis virus (JEV) in these mosquitoes at the nesting colony of ardeid birds. METHODS Mosquitoes were collected bimonthly from July 2009 to May 2010 by Centers for Disease Control. Light traps and dry ice, as a source of CO2, were employed to attract mosquitoes. Mosquitoes were first identified, pooled into groups of upto 50 mosquitoes by species, and tested for JEV infection by viral isolation and reverse transcriptase polymerase chain reaction. RESULTS A total of 20 370 mosquitoes comprising 14 species in five genera were collected. The five most abundant mosquito species collected were Culex tritaeniorhynchus (95.46%), Culex vishnui (2.68%), Culex gelidus (0.72%), Anopheles peditaeniatus (0.58%) and Culex quinquefasciatus (0.22%). Mosquito peak densities were observed in July. All of 416 mosquito pools were negative for JEV. CONCLUSIONS This study provides new information about mosquito species and status of JEV infection in mosquitoes in Thailand. Further study should be done to continue a close survey for the presence of this virus in the ardeid birds.

Molecular epidemiology of bovine Babesia spp. and Theileria orientalis parasites in beef cattle from northern and northeastern Thailand.

Beef cattle production represents the largest cattle population in Thailand. Their productivity is constrained by tick-borne diseases such as babesiosis and theileriosis. In this study, we determined the prevalence of Babesia bigemina, Babesia bovis and Theileria orientalis using polymerase chain reaction (PCR). The genetic markers that were used for detection of the above parasites were sequenced to determine identities and similarity for Babesia spp. and genetic diversity of T. orientalis. Furthermore the risk factors for the occurrence of the above protozoan parasites in beef cattle from northern and northeastern parts of Thailand were assessed. A total of 329 blood samples were collected from beef cattle in 6 provinces. The study revealed that T. orientalis was the most prevalent (30.1%) parasite in beef cattle followed by B. bigemina (13.1%) and B. bovis (5.5%). Overall, 78.7% of the cattle screened were infected with at least one of the above parasites. Co-infection with Babesia spp. and T. orientalis was 30.1%. B. bigemina and T. orientalis were the most prevalent (15.1%) co-infection although triple infection with the three parasites was observed in 3.0% of the samples. Sequencing analysis revealed that B. bigemina RAP1 gene and B. bovis SBP2 gene were conserved among the parasites from different cattle samples. Phylogenetic analysis showed that the T. orientalis MPSP gene from parasites isolated from cattle in north and northeast Thailand was classified into types 5 and 7 as reported previously. Lack of tick control program was the universal risk factor of the occurrence of Babesia spp. and T. orientalis infection in beef cattle in northern and northeastern Thailand. We therefore recommend training of farmers on appropriate tick control strategies and further research on potential vectors for T. orientalis and elucidate the effect of co-infection with Babesia spp. on the pathogenicity of T. orientalis infection on beef in northern and northeastern Thailand.

Mosquito distribution and West Nile virus infection in zoos and in important sites of migratory and resident birds, Thailand

Objective To investigate the distribution of mosquito species in the zoos and in important sites of migratory and resident birds and evaluate West Nile virus (WNV) infection in mosquito species.

Stomoxyini fly fauna of the Khao Yai National Park, Thailand

Objective To determine species diversity, relative population abundance and diurnal activity of the Stomoxyini flies at the Khao Yai National Park.

Landmark and outline-based geometric morphometrics analysis of three Stomoxys flies (Diptera: Muscidae).

Adult flies of the genus Stomoxys Geoffroy, 1762 (Diptera: Muscidae), especially S. pullus Austen, 1909, S. uruma Shinonaga et Kano, 1966 and S. indicus Picard, 1908, are morphologically similar and sometimes difficult to distinguish when using external morphological characteristics. These species may act as vectors and/or potential vectors of many pathogens (virus, bacteria and protozoa). Their correct identification is important to target the vectors involved in the transmission of the pathogens and also helps in the fly control program.The aim of the present study was to distinguish three species which are difficult to separate using traditional diagnostic characters for species of Stomoxys such as colour patterns and body proportions. Modern morphometrics, both landmark and outline-based, was used to access wing geometry of S. pullus, S. uruma and S. indicus. A total of 198 and 190 wing pictures were analysed for landmark- and outline-based approaches, respectively. Wing shape was able to separate species and sexes of the three Stomoxys flies with highly significant difference of Mahalanobis distances. The cross-validated classification scores ranged from 76% to 100% for landmark and 77% to 96% for outline-based morphometrics. The geometry of wing features appears to be a very useful, low-cost tool to distinguish among the vectors S. pullus, S. uruma and S. indicus.

Species identification of horse flies (Diptera: Tabanidae) in Thailand using DNA barcoding

Horse flies (Diptera: Tabanidae) are of medical and veterinary importance because they are known to transmit pathogens. Approximately 80 species of horse flies have been reported in Thailand. Monitoring the distribution of horse fly species is important to control the spread of diseases transmitted by them. Currently, the species identification of horse flies is based on their morphology; this requires considerable skills and taxonomic expertise, and it may be difficult to identify morphologically similar species. DNA-based identification methods are increasingly being developed for rapid and accurate identification of various insect species. In this study, we used mitochondrial cytochrome oxidase subunit I (COI) for species identification of horse flies in Thailand. A 658 bp fragment of COI was amplified from 145 adult horse flies belonging to 48 morphologically distinct species and sequenced. Sequence analysis revealed an intraspecific divergence of 0.0%-4.4% and an interspecific divergence of 0.0%-16.2%. Our results showed that COI barcodes were effective in discriminating a majority of horse flies in Thailand on the basis of the barcoding gap and phylogenetic analyses. However, COI barcodes were unable to distinguish among members of the Tabanus striatus complex and some species within the T. ceylonicus group.