title: Vectors and malaria transmission in deforested, rural communities in north-central Vietnam.
abstract: BACKGROUND
  Malaria is still prevalent in rural communities of central Vietnam even though, due to deforestation, the primary vector Anopheles dirus is uncommon. In these situations little is known about the secondary vectors which are responsible for maintaining transmission. Basic information on the identification of the species in these rural communities is required so that transmission parameters, such as ecology, behaviour and vectorial status can be assigned to the appropriate species.
  
  
  METHODS
  In two rural villages--Khe Ngang and Hang Chuon--in Truong Xuan Commune, Quang Binh Province, north central Vietnam, a series of longitudinal entomological surveys were conducted during the wet and dry seasons from 2003-2007. In these surveys anopheline mosquitoes were collected in human landing catches, paired human and animal bait collections, and from larval surveys. Specimens belonging to species complexes were identified by PCR and sequence analysis, incrimination of vectors was by detection of circumsporozoite protein using an enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Over 80% of the anopheline fauna was made up of Anopheles sinensis, Anopheles aconitus, Anopheles harrisoni, Anopheles maculatus, Anopheles sawadwongporni, and Anopheles philippinensis. PCR and sequence analysis resolved identification issues in the Funestus Group, Maculatus Group, Hyrcanus Group and Dirus Complex. Most species were zoophilic and while all species could be collected biting humans significantly higher densities were attracted to cattle and buffalo. Anopheles dirus was the most anthropophilic species but was uncommon making up only 1.24% of all anophelines collected. Anopheles sinensis, An. aconitus, An. harrisoni, An. maculatus, An. sawadwongporni, Anopheles peditaeniatus and An. philippinensis were all found positive for circumsporozoite protein. Heterogeneity in oviposition site preference between species enabled vector densities to be high in both the wet and dry seasons allowing for year round transmission.
  
  
  CONCLUSIONS
  In rural communities in north central Vietnam, malaria transmission was maintained by a number of anopheline species which though collected feeding on humans were predominantly zoophilic, this behaviour allows for low level but persistent malaria transmission. The important animal baits--cattle and buffalo--were kept in the village and barrier spraying around these animals may be more effective at reducing vector densities and longevity than the currently used indoor residual spraying.
authors.affiliation: Entomology Department, Military Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Cuong Do
authors.initials: CD
authors.lastname: Manh
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Beebe
authors.forename: Van Nguyen Thi
authors.initials: VN
authors.lastname: Van
authors.forename: Tao Le
authors.initials: TL
authors.lastname: Quang
authors.forename: Chau Tran
authors.initials: CT
authors.lastname: Lein
authors.forename: Dung Van
authors.initials: DV
authors.lastname: Nguyen
authors.forename: Thanh Nguyen
authors.initials: TN
authors.lastname: Xuan
authors.forename: Anh Le
authors.initials: AL
authors.lastname: Ngoc
authors.forename: Robert D
authors.initials: RD
authors.lastname: Cooper
mesh_terms: D000818:Animals; D000852:Anopheles / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000469:parasitology*; D002020:Buffaloes; D002417:Cattle; D002648:Child; D002675:Child, Preschool; D004199:Disease Vectors; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008288:Malaria / Q000453:epidemiology* / Q000635:transmission*; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins / Q000032:analysis*; D012424:Rural Population; D012621:Seasons; D017422:Sequence Analysis, DNA; D014744:Vietnam / Q000453:epidemiology
chemical_list: D015800:Protozoan Proteins; C041595:circumsporozoite protein, Protozoan