Effectiveness of Joint 3+1 Malaria Strategy Along China-Myanmar Cross Border Areas

Abstract Background: Cross-border malaria in Laiza City of Myanmar seriously affected Yingjiang County of China and compromised the national malaria elimination goal. A pilot project on 3+1 strategy of joint cross-border malaria prevention and control was carried out in building border malaria buffer area in the both sides since 2017; Here, 3 was the three preventive lines in Yingjiang County to strengthen targeted measures of elimination malaria in China and +1 was a defined border area in Laiza City to adopt the integrated measures of malaria control in Myanmar.Methods: A retrospective analysis from 2015 to 2019 was conducted that included case detection, parasite prevalence and vector surveillance. Descriptive statistics was used and the incidence or rates were compared. The annual parasite incidence in +1 area of Myanmar, the annual importation rate in Yingjiang County of China and the density of An.Minimus were statistically significant indictors to assess the effect of the joint interventions.Results: In +1 area of Myanmar from 2015 to 2019, the average of annual parasite incidence was (59.11±40.73) / 1000 and plasmodium vivax accounted for 96.27 % of total confirmed cases. After the pilot project, the annual parasite incidence, microscopic parasite prevalence rate and density of An. Minimus reduced by 89%,100% and 93.93% respectively, but the submicroscopic parasite prevalence rate was no significant difference between the two surveys (p =0.084). In Yingjiang County of China, neither indigenous nor introduced case was reported and 100% cases were imported from Myanmar since 2017. The average of annual importation rate from 2015 to 2019 was (0.47±0.15)/1000. After the pilot project, it reduced by 53% of whole county, 67% of the first preventive line, 52% of the second preventive line and 36% of the third preventive line respectively. The density of An. Minimus in the first preventive line reduced by 94.51% and did not have significant difference between that of+1 area of Myanmar (Z value=-1.18，p value=0.24). Conclusion: The pilot project on 3+1 strategy has made remarkable effectiveness and a buffer area of border malaria was successfully established between Laiza City of Myanmar and Yingjiang County of China. The combined use and expanded coverage of indoor residual spraying and long-lasting insecticidal nets (LLINs) was more effective than only use of LLINs in reducing the transmission of plasmodium vivax caused by An. Minimus. It is necessary to adopt submicroscopic infection interventions to eliminate potential sources of infection in Laiza City of Myanmar.