Mohd. Ngesom, A. M. | bioRxiv Science

bioRxiv2020

Implications of the COVID-19 lockdown on dengue transmission and the occurrence of Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) in Malaysia

The impact of movement restrictions during the COVID-19 lockdown on the existing endemic infectious disease dengue fever has generated considerable research interest. We compared the Malaysia weekly epidemiological records of dengue incidences during the period of lockdown to the trend of previous years (2015 to 2019) and a simulation at the corresponding period that expected no movement restrictions. We found that the dengue incidence declined significantly with a greater magnitude at phase 1 of lockdown, with a negative gradient of 3.2-fold steeper than the trend observed in previous years and 6.5-fold steeper than the simulation, indicating that the control of population movement did reduce dengue transmission. However, starting from phase 2 of lockdown, the dengue incidences demonstrated an elevation and earlier rebound by at least 4 weeks and grew with an exponential pattern compared to the simulation and previous years. Together with our data on Aedes mosquitoes from a district of Penang, Malaysia, we revealed that Aedes albopictus is the predominant species for both indoor and outdoor environments. The abundance of the mosquito was increasing steadily during the period of lockdown, and demonstrated strong correlation with the locally reported dengue incidences; therefore, we proposed the possible diffusive effect of vector that led to a higher acceleration of incidence rate. These findings would help authorities review the direction and efforts of the vector control strategy.

zoology↗

bioRxiv2020

Small-scale field assessment of efficacy of the autodissemination approach against Aedes sp. in an urban area.

This is the first study to evaluate the efficacy of an autodissemination approach, as suggested by WHO. Therefore, the efficacy of an autodissemination approach in small-scale field trials against wild Aedes sp. population was evaluated in an urbanized setting, Malaysia. Lethal ovitraps enhanced with pyriproxyfen were used to control Aedes sp. populations at treatment sites, with the autodissemination activity was assessed using the WHO larval bioassays. Lethal ovitraps enhanced with pyriproxyfen effectively reduced of Aedes sp. population. All autodissemination stations were shown to be visited by Aedes sp. mosquitoes with 100% complete inhibition against eggs and larvae development. In the larvae bioassay, pupae mortality ranged from 14 to 40%. Statistically, a significant reduction of Aedes sp. population in the treatment sites compared to the untreated areas. The study proved for the autodissemination of pyriproxyfen to breeding habitats by wild Aedes sp. This technique is highly potentially for vector control activities. Future evaluation should focus on large-scale field trials. Author SummarySince 2012, Dataran Automobil, Seksyen 15, Shah Alam, was declared as one of the dengue hotspot areas. Major vector control activities were conducted by government, NGOs, social communities, and local authorities, but the number still rising. We conducted a new invention of autodissemination concepts in this area by an entomological study on mosquito populations reduction and dispersal abilities of the technique. We found that the technique has proven to control mosquito populations, but the other factors such as epidemiology link still unclear and need further clarification. Our finding highlighted the effectiveness of autodissemination strategies that can be considered as one of the alternative tools in vector control programme.

ecology↗