Japanese Encephalitis Vectors in India

  • Japanese encephalitis virus isolation has been made from a variety of mosquito species.
  • Culicine mosquitoes mainly Culex vishnui group (Culex tritaeniorhynchus, Culex vishnui and Culex pseudovishnui) are the chief vectors of JE in different parts of India.
Sl. No. Species No. of Isolations State*
1 Cx. tritaeniorhynchus 79 TN, KA, KL
2 Cx. vishnui 30 TN, KA, WB
3 Cx. pseudovishnui 8 KA, GOA
4 Cx. bitaeniorhynchus 3 KA, WB
5 Cx. epidesmus 1 WB
6 Cx. fuscocephala 7 TN, KA
7 Cx. gelidus 8 TN, KA
8 Cx. quinquefasciatus 1 KA
9 Cx. whitmorei 4 TN, KA, AP, WB
10 An. barbirostris 1 WB
11 An. paeditaeniatus 1 KA
12 An. subpictus 9 TN, KA, KL
13 Ma. annulifera 2 KL, ASSAM
14 Ma. indiana 3 KL
15 Ma. uniformis 4 KA, KL
  * AP= Andhra Pradesh; TN= Tamil Nadu; KA= Karnataka; KL= Kerala; WB= West Bengal    
  • Life cycle consists of egg, four instars of larvae, pupa and adult. The whole cycle takes more than a month, however, duration depends on temperature and other ecological conditions.
  • Culex vishnui subgroup is very common, widespread and breed in water with luxuriant vegetation mainly in paddy fields and the abundance is related to rice cultivation, shallow ditches and pools.
  • These vectors are primarily outdoor resting in vegetation and other shaded places but in summer may also rest in indoors.
  • They are in principally cattle feeders, though human and pig feeding are also recorded in some areas.