**7. Change in vector control strategy**

There are 465 *Anopheles* mosquitoes in the world, of which many members have sibling species complexes. Approximately 70 of them are capable for human malaria transmission [23]. Application of public health insecticides is the main strategy for vector control. DDT is the main insecticide and is partially responsible for most malaria elimination in Europe and Americas along with general improvement of living standards, and an effective detection and treatment program. Other countries missed out this opportunity to achieve this feat. Prolongation of its use lead to the development of resistance in the mid-1970s and also recorded the highest number of malaria cases. Other insecticides namely malathion (organophosphorous) and subsequently synthetic pyrethroids (deltamethrin, alphacypermethrin, lambdacyhalothrin, cyfluthrin, etc.) are used in the program. In some endemic areas, triple resistance has been recorded against the main rural vector *An. culicifacies*. Currently long lasting insecticidal nets (LLINs) impregnated with synthetic

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 difficult in managing vector control operations [24].

#### **7.1 Outdoor and residual transmission**

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 be avoided [26].

#### **7.2 Removing shrubs around houses**

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 composition [27].

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

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 community engagement for proper implementation [29].

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 place to avoid such residual transmission and outbreaks.

**43**

*New Ways to Tackle Malaria*

**7.4 Gene editing**

*DOI: http://dx.doi.org/10.5772/intechopen.89467*

**7.5 Fungal application for vector control**

*coluzzii* and *An. gambiae s.l* [33].

**7.7 Paratransgenesis**

**7.8 Jhum cultivation**

**7.6 Bioenvironmental control of disease vectors**

education and community engagement is an integral part [34].

way for the involvement of gene modification technology [36].

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

Entomopathogenic transgenic fungus *Metarhizium pingshaense* expressing the spider neurotoxin hybrid (met-hybrid) killed 99% of the mosquito population in a controlled trial in Burkina Faso. The study was conducted in a trial village of 600 square meters area or `mosquito sphere'. The test mosquitoes were killed within 45 days. The researchers hope to find out a new tool to eliminate malaria when insecticide resistance is a major problem [32]. Before this field trial, extensive laboratory experiments were carried out on the two important malaria species *An.* 

This is a holistic approach of vector control practiced in the beginning of the 20th century. The main aim of this approach is source reduction of larval breeding habitats. In other words, larval source management is the key strategy that mitigates challenges of larval control. Minor engineering, filling up of pools and puddles near human habitats, and biological control are some methods of this strategy. Since the mid-1980s the ICMR- National Institute of Malaria Research, New Delhi, India has made pioneering work on this front with great successes. In this strategy, health

Paratransgenesis is a process by which the genetically modified symbionts from a target insect express molecules within the vector that show refraction to pathogens they transmit. This is a novel approach, now used for the control of malaria, trypanosomiasis and dengue. Recently, for the first time, we found *Veillonella* sp. in the gut of *An. stephensi* which may play an important role in paratransgenesis. A diverse microbial community was recorded in the salivary glands in *An. culicifacies* the main malaria vector in rural India [35]. However, this strategy has to go a long

Jhum or jhoom cultivation or slash and burn cultivation is a common practice of cultivation among tribal populations of northeast India and also in some hilly districts of Bangladesh. This practice of cultivation is linked with malaria transmission [37]. Besides using LLINs, it is important to find the main breeding habitats of vector species mainly *An. dirus* s.l. during the dry season. Control of such vector

endemic species to maintain the conservation of biodiversity [1].
