**7.4 Gene editing**

*Vector-Borne Diseases - Recent Developments in Epidemiology and Control*

difficult in managing vector control operations [24].

**7.1 Outdoor and residual transmission**

pyrethroids are widely used in the program. In general, behavioral changes of vector mosquitoes are a common phenomenon due to continuous use of IRS insecticides. This leads to outdoor resting and feeding behavior which are responsible for outdoor transmission. Some species change their biting time also, and thus becomes

Generally outdoor and residual transmissions are considered as the same phenomenon. But these are separate issues and would be dealt separately. Outdoor transmission occurs when local community engages on outdoor duties due to professional compulsion. This is most prevalent in forest fringe areas. For example, *An. dirus s.l*. is the most dominant species in Southeast Asia region. Here LLINs have very limited role. Many methods have been suggested, but none have been used for any practical purposes. Several traps have been developed in recent years; some are lightbased, some CO2- based, some octanol, commercial attractants based, and some with combination of all. Many experts recommend covering the whole body with proper clothing especially for security personnel, use of mosquito repellents and chemoprevention [1]. Recently Center for Disease control and Prevention (CDC) has approved the lemon eucalyptus oil for general use as mosquito repellent [25]. The most disturbing fact is that in most village settings human and cattle have mixed dwellings. This encourages the zoophagic mosquitoes to move from the bovine host to the humans. Here, a community-level action is needed. Experts recommend that all cattle dwellings should be located on the periphery of the village so there would be a spatial barrier between the foraging mosquitoes and humans. In this way, a strong zooprophylaxis would be established and direct human biting can

Outdoor transmission can be effectively contained when flowering shrubs around houses are removed. A study in Mali supports such concepts. The selected villages where flowering branches of invasive shrub *Prosopis juliflora* were removed experienced a 69.4% drop in *Anopheles* population density and a shifting of species

Like removing shrubs, ATSB is an alternate strategy to eliminate mosquitoes. Sugar bait of 10% sucrose mixed with 0.01% ivermectin soaked in sponge bait knocked down over 95% of *An. arabiensis* population [28]. But it requires commu-

Studies should be carried out to define the bionomics of local vectors. This will provide valuable information for planning proper vector control strategies. This should be an ongoing program. In the malaria elimination program, routine monitoring of vectors will allow appropriate decisions for effective control. Residual transmission is a resultant of presence of sub-microscopic level of malarial parasites in the community. This happens when intensive control measures overlook the residual presence of parasites. Such a situation happens when a type of complacency prevails and the surveillance system becomes fatigued. Many local-level focal outbreaks happen, and the public health response activities for vector control fail to decimate such foci [30]. It is, thus important to have a strict surveillance system in

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be avoided [26].

composition [27].

**7.2 Removing shrubs around houses**

**7.3 Attractive toxic sugar bait (ATSB)**

nity engagement for proper implementation [29].

place to avoid such residual transmission and outbreaks.

The recent advances in genetic engineering technology of CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/Cas9), a system targets specific stretches of DNA and edit genomes at specific locations. This tool of gene editing/drive technology can revolutionize malaria elimination efforts by identifying and targeting the local vectors. The aim should be to create transgenic mosquitoes that will not be able to carry the malaria parasites. Some success to create transgenic species of the main malaria vector of African countries, *An. Gambiae,* has been achieved [31]. Gene-driven mosquitoes do not follow the Mendelian law of inheritance. This technology can be effectively applied to eliminate the invasive and endemic species to maintain the conservation of biodiversity [1].
