Distribution of Mosquitoes and Mosquito-Borne Arboviruses in Yunnan Province near the China–Myanmar–Laos Border

Abstract

Abstract. Economic development and increased tourism in the southern region of Yunnan Province in China, adjacent to several countries in Southeast Asia, has increased the likelihood of import and export of vectors and vector-borne diseases. We report the results of surveillance of mosquitoes and mosquito-borne arboviruses along the border of ChinaMyanmar-Laos in 2005 and 2006, and information associating several arboviruses with infections and possibly disease in local human populations. Seventeen mosquito species representing four genera were obtained, and 14 strains of mosquito-borne viruses representing six viruses in five genera were isolated from Culex tritaeniorhynchus . In addition, IgM against Japanese encephalitis virus, Sindbis virus, Yunnan orbivirus and novel Banna virus was detected in acute-phase serum samples obtained from hospitalized patients with fever and encephalitis near the areas where the viruses were isolated. This investigation suggests that Japanese encephalitis virus, Sindbis virus, and lesser-known arboviruses circulate and may be infecting humans in the China-Myanmar-Laos border region. immune ascites against alphaviruses, specific antisera to SINV, Getah virus, Mayaro virus, chikungunya virus, and Simliki Forest virus, and antisera against the flaviviruses JEV, dengue virus, and West Nile virus. Antisera were diluted 1:50 in PBS before use. After subsequent rinses in PBS and sterile water, the slides were probed with the secondary rabbit anti-mouse monoclonal fluorescein isothiocyanate conjugate (Sigma, St. Louis, MO) at 37°C for 30 minutes before visualization with a fluorescent microscopy. Positive and negative controls of immune ascites against alphaviruses were SINV (YN87448) and JEV (P3), respectively. Positive and negative controls of immune ascites against flavivirus antisera were JEV (P3) and SINV (YN87448), respectively.Polyacrylamide gel electrophoresis, RNA extraction, cDNA synthesis, reverse transcription-polymerase chain reaction, and sequence analysis. RNA extraction and polyacrylamide gel electrophoresis were performed as described. 18 Briefly, doublestranded RNA was extracted from approximately 400 μL of cell suspension with phenol/chloroform. Each RNA sample was mixed with sample buffer and subjected to electrophoresis at room temperature on a standard discontinuous 7%, 10%, or 15% acrylamide (acrylamide/bisacrylamide 29:1; Bio-Rad Laboratories, Hercules, CA) slab gel (18 × 16 × 0.075 cm) (Hoefer Pharmacia Biotech Inc., San Francisco, CA) with a 3.5% acrylamide stacking gel in Tris-glycine buffer (25 mM Tris, 192 mM glycine, pH 8.3) (Bio-Rad Laboratories). After electrophoresis, virus double-stranded RNAs were visualized by staining with silver nitrate. Viral RNA was extracted by using the QIAamp Viral RNA Mini Kit (Qiagen, Valencia, CA), and cDNA was synthesized by using Ready-To-Go You-Prime First Strand Beads (Amersham Pharmacia Biotech, Piscataway, NJ) according to the manufacturer's procedure. Samples were tested by polymerase chain reaction (PCR) with flavivi...

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Genome sequencing and phylogenetic analysis of Banna virus (genus Seadornavirus, family Reoviridae) isolated from Culicoides

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