Correlation between Breteau index and mosquito oviposition index in surveillance for Aedes albopictus larvae density

  Objective   To observe the trend of continuous density of Aedes albopictus larvae by using Breteau Index (BI) and the Mosquito Oviposition Index (MOI), and compare the grey correlation, spearman correlation and risk grade consistency of the two density indexes in different habitats.

  Methods   The densities of Aedes albopictus in Wuxing district (place A) and in Nanxun district (place B) in Huzhou were monitored every ten days by using BI and MOI from April to December in 2020. The correlation between BI and MOI were analyzed by grey correlation and spearman correlation. The two density indexes were classified according to the risk assessment criteria of Aedes vector surveillance guidelines. And the consistency of risk grade of two methods was compared by Kappa test.

  Results   The density of Aedes albopictus indicated by BI and MOI increased first and then decreased from April to December. When the density was very low or very high (BI<5, BI>20), the BI was higher than MOI. When the density index was between 5 and 20, the BI and MOI fluctuated. The BI was higher than the MOI from April to July. However, the MOI was higher than the BI from August to October. The grey correlation degree of the BI and the MOI were 0.601 and 0.682 in urban and rural residential areas respectively in place A and 0.696 and 0.671 in urban and rural residential areas respectively in place B, and the spearman correlation coefficients of the BI and the MOI were 0.461 and 1.000 in urban and rural residential areas in place A and 0.531 and 0.444 respectively in place B, the differences were all significant (P<0.05). The Kappa value of two index risk grade in urban residential area was 0.160, the Kappa value in rural residential area was −0.143 in place A and the Kappa value in urban residential area was 0.186 in place B, but there were no significant difference, while the kappa value in rural residential area was 0.180 in B place, the difference was significant (P<0.05).

  Conclusion   The density of Aedes albopictus larvae increased and decreased seasonally. There was a certain correlation between BI and MOI in the surveillance for the seasonal density of Aaedes Aalbopictus larvae, but the consistency of risk level was not good. The sensitivity of BI is better than that of MOI when the density of Aedes is very low or high.