Vector Control Strategies

*Wilber Gómez-Vargas and Giovani Esteban Zapata-Úsuga*

#### **Abstract**

Vector-borne diseases, mainly dengue and malaria, are serious public health problems in the world; for the control of Aedes and Anopheles mosquitoes, there are several strategies such as biological, genetic, chemical, physical, and cultural. For the application of these control strategies, it is important to take into account the integrated vector management promoted by the World Health Organisation, taking into account the local context. This chapter shows the most important recent advances in vector control methods. The efforts of researchers in the development and evaluation of these and new control methods, the political will of governments, funding from the business sector, and community participation are essential to the success of these strategies.

**Keywords:** Aedes, Anopheles, new technologies, vector-borne diseases, vector control

#### **1. Introduction**

Globally, dengue remains a serious public health problem due to increasingly severe epidemics [1] and the emergence of new arboviruses, such as chikungunya and Zika, and the re-emergence of other arboviruses that were already under control, such as yellow fever, which has recorded cases in urban settings for the first time in more than 50 years [2]. As for malaria, although in recent years there has been progressing in its reduction, it still continues to affect many communities, especially children in Africa [3]. World Health Organisation (WHO) warns of the growing threat of resistance from malaria vectors and parasites, and the challenges of the COVID-19 pandemic [3].

Mosquito control of vectors *Aedes* and *Anopheles* measures include biological control, genetic control, chemical control, physical control, and cultural control.

Related to biological control, several studies have been reported recently that species of some fungal genera, for example, *Streptomyces*, *Pycnoporus, Pestalotiopsis*, *Culicinomyces*, *Leptoneglia*, *Beauveria Metarhizium, Cochliobolus and Aspergillus* and bacterial genera, for example, *Wolbachia*, *Bacillus,* and *Pseudomonas* display a potent ability to kill many species of mosquitoes, including those of the genera *Aedes* and *Anopheles*, mainly. Kairomones and pheromones are being developed. Nematode control for *Aedes* has been little studied, while for *Anopheles,* it has seen more development and interest in recent years.

As for genetic control, advances in the sterile insect technical (SIT), the insect incompatibility insect (IIT), and control by genetic manipulation are highlighted, mainly in *Aedes* control. SIT has been implemented mainly in *Anopheles arabiensis*.

In terms of chemical vector control, advances are directed towards the development of new insecticides extracted from plants and the use of the method Autodissemination Augmented by Males (ADAM) that can be useful for small and cryptic containers of *Aedes aegypti* and useful in the control of *Anopheles arabiensis*.

Physical control has been progressing in ovitraps and acoustic larvicides that are promising for control of *A. aegypti*. In Anopheles control, the use of mosquito nets is highlighted.

Concerning cultural control, communication for mobilisation and behavioural impact (COMBI), approaches to social participation and eco-health are of vital importance in control programmes.

The WHO in its global vector control response 2017–2030 [4], noted the urgent need for the development and integration of innovative mosquito control methods, mainly *Aedes* and *Anopheles* vectors. New control strategies targeting these species are being developed, but their impact on arboviral diseases and malaria transmitted by these vectors has not yet been demonstrated. To this end, the WHO has adopted Integrated Vector Management [IVM], defined as "a rational decision-making process for the optimal use of vector control resources" [5], which provides countries with long-term sustainable and ecologically sound control methods that can reduce dependence on insecticides and protect populations where vector-borne diseases are prevalent, improving the effectiveness and efficiency of national vector control programmes [6].

The objective of this chapter is to review the progress made over the last 10 years in the control of the *Aedes* and *Anopheles* vectors.

### **2. Control** *Aedes* **mosquitoes**

#### **2.1 Biological control**

#### *2.1.1 Traditional strategies*

Species *A. aegypti* and *Aedes albopictus* are the most prominent vectors in the transmission of arboviruses, such as dengue, chikungunya, yellow fever, and Zika [7]. Worldwide, biological control of these species, mainly *Ae. aegypti* has been specifically geared towards larvae, and the most commonly used control method has been biolarvicide *Bacillus thuringiensis* var. *israelensis* (*Bti*) and larvivores fish [8].

#### *2.1.2 Bacterial control*

An important and promising development dwells in the use of endosymbiont gram-negative bacteria *Wolbachia*. The strain being used in field trials is the wMel strain of *Wolbachia pipientis*. It consists of the artificial infection of *Ae. aegypti* (wAlbB) or *Ae. albopictus* (wPip) with the bacteria, mainly transmitted vertically, which intervenes in the manipulation of the host's reproduction to optimise its maternal transmission through eggs, favouring females, and inducing different distortion phenotypes among sexes of the progeny through mechanisms of parthenogenesis, feminization, and cytoplasmatic incompatibility (CI) [9–12]. *Wolbachia* is also present in somatic tissues, it can, therefore, be acquired from infected embryonic lineages or pass from cell to cell [13]. Furthermore, these bacteria can also block the replication of arboviruses (pathogenic interference) in populations of field mosquitoes [14, 15].

#### *Vector Control Strategies DOI: http://dx.doi.org/10.5772/intechopen.105026*

After *Wolbachia* is established in the local mosquito population, there is no need for further releases. It could also be genetically modified to prevent the vector from becoming infected, a phenomenon known as paratransgenesis [16]. Nevertheless, the use of *Wolbachia* as a control strategy is under scrutiny due to uncertainties related to the longevity of the viral suppression and the possibility of concomitant adaptative changes in the vector mosquito, the bacteria, or the virus [17]. Consequently, the use of mosquitoes infected with *Wolbachia* has not been approved in most countries due to insufficient knowledge of the potential dangers of this control method [18]. Pilot tests are currently being conducted by the World Mosquito Program in 12 countries in Asia, Central and South America, and the Pacific region [19].

Recently with the advances in nanotechnology, the bacterial products are produced from the synthesis of nanoparticles method that has been used with *B. thuringiensis* in third instar larvae of *Ae. aegypti* resulting in a 65% mortality [LC50: 0.10 ppm and LC90: 0.39 ppm] [20]. In another study, the ovicidal, pupicidal, and larvicidal efficacy of silver nanoparticles synthesised by *Bacillus marisflavi* strain isolated from marine habitat in species of *Ae. aegypti, Culex quinquefasciatus* and *Anopheles stephensi* have been demonstrated. The use of nanoparticles and their rapid synthesis of AgNPs against vectors, especially *Ae. aegypti*, would be a good biological control tool. However, the current research has some limitations, such as the cost-effective analysis and possible contamination of nanoparticles in the ambient or their effects on other useful microbes [21].

On the other hand, bacteria-derived metabolites may be a potential substitute for insecticides that have developed resistance. A study showed that secondary metabolites from extremophilic bacteria *Bacillus* and *Pseudomonas* sp., which caused larvae mortality of *Ae. aegypti* and *Cu. quinquefasciatus* of 100% at a concentration of 100 ppm [22].

#### *2.1.3 Fungal control*

Nowadays, there is an ample selection of fungal products with larvicide properties against vector *Ae. aegypti*. One of such products is chitinase enzymes from *Streptomyces cacaoi* subsp. *cacaoi-*M20 directed at the chitin required by the larvae, in which at the concentrations of 75 μl, 125 μl, 250 μl, and 500 μl no pupa formation and adult emergence were observed in experiments conducted [23]. Other promising products are ethyl acetate extracts from fungi, such as fungus *Pycnoporus sanguineus* which had a larvicidal activity of LC50 = 156.8 ppm and relative potency (0.612) and *Pestalotiopsis virgulate* with a larvicidal activity of LC50 = 101.8 ppm and relative potency (1.634), against *Ae. aegypti* larvae [24].

Studies with entomopathogenic fungi have proven promising in vector control such as *Culicinomyces clavisporus* that showed LC50 (≤ 3.6 × 105 conidia/ml) after a 3-day exposure and LT50 (≤ 1.3 days) at 106 conidia/ml against *Ae. aegypti* larvae [25] and *Leptoneglia chapmanii* where the persistence and pathogenicity decreased over time regardless of location, the assays showed that the mortality of *Ae. aegypti* larvae was significantly lower (p < 0.05) in containers located outside without sun protection (89% at first week and 9% at sixth week) compared with the containers located indoors (97% at first week and 42% at sixth week) and outside with shade (89% at first week and 29% at sixth week) [26, 27]. Another new fungus is *Isaria tenuipes* (formerly *Paecilomyces tenuipes*) a common fungal species that frequently affects major agricultural pests usually belonging to the group lepidopteran but this study showed that the fungus heavily damaged the internal gut cells and external physiology of *Ae. aegypti*

larvae and its non-toxic activity against aquatic predators, such as *Toxorhynchites splendens*, this fungus will add on to its biologically safe insecticides [28]*.*

As for adult control, particularly of *Ae. aegypti*, new methods of control have been developed in recent years, such as autodissemination of entomopathogenic fungi, mainly using isolates *Metarhizium anisoplae* and *Beaveria bassiana* in the laboratory [29, 30]. This process "uses a sexual or other attractants to concentrate individuals of one sex and spread the fungi in natural populations" [31]. *M. anisoplae* transmitted by males killed 85% of females in sexual encounters and reduced female fecundity by 99% [29]. *B. bassiana* killed 90% of the females confined with a fungus-contaminated male in 15 days and reduced female fecundity by 96% [30].

Recently with the advances in nanotechnology, products produced from the synthesis of nanoparticles aided by fungal are being studied. For example, the larvicide activity of silver nanoparticles (AgNPs) synthesised by fungus *Cochliobolus lunatus*, where a 100% mortality was observed at concentrations of 10 and 5 ppm against all instars treated [2nd, 3rd y 4th] [32]. In another study, cerium oxide nanoparticles were synthesised through *Aspergillus niger*, which resulted in 100% mortality of first instar larvae of *Ae. aegypti* at a dosage of 0.250 mg/L [33].

#### *2.1.4 Entomopathogenic nematodes*

Few studies are interested in the effect of nematodes on *Ae. aegypti* control, a study published in Argentina in 2014, was tested the infectivity of *Heterorhabditis bacteriophora* on *Ae. aegypti* larvae, and larval mortality rates ranges of 0–84% [34]. In another study conducted in Mexico, strains of *Heterorhabditis bacteriophora* and *Steinernema carpocapsae* were tested for their pathogenicity as infective juveniles (IJs) against larvae of *Ae. aegypti* (L.) of third- and fourth-instar mosquito larvae. Strain M5 of *S. carpocapsae* caused 100% mortality at the 200 IJ/larva concentration, with a median lethal concentration (LC50) of 42 IJ/larva (LC90 = 91 IJ/larva). Strain M18 of *Heterohabditis bacteriophora* caused 73% mortality at 200 IJ/larva, with an LC50 = 72 and LC90 = 319 IJ/larva [35]. In a study, the larvicidal potential against some mosquito species of several nematodes isolated from soil was evaluated under laboratory conditions. The nematode *Steinernema abassi* showed 97.33% of mortality against *Ae. aegypti* [36]. These researches would lead to the development of an eco-friendly mosquito control agent.

#### **2.2 Genetic control**

#### *2.2.1 Sterile insect technical (SIT)*

Over the last decades, the Sterile Insect Technique (SIT), one of the most important methods of genetic control, has greatly developed [37]. This technique, specific to each species, consists of mass-rearing of male insects, genetically modified or not [through chemicals or radiation], to be released in target areas in quantities sufficient for them to compete with wild males for wild females and mate with them. They will, therefore, sterilise the females or transfer to their progeny lethal modifications or modifications that prevent pathogenic transmission, contributing to the reduction of target populations. Sustained liberation of sterile males will reduce the target population or potentially eradicate isolated populations [16, 18, 38]. Since the 1960s and 1970s, SIT has been successfully used against *Cu. quinquefasciatus* in the USA [39], *An. albimanus* in El Salvador [40] and the control of tsetse fly in Africa [41]. Pilot trials

#### *Vector Control Strategies DOI: http://dx.doi.org/10.5772/intechopen.105026*

in the USA in which gamma-irradiated sterile male *Ae. aegypti* and *Anopheles quadrimaculatus* were released, showed no apparent suppression of populations after 43–48 weeks in the treated areas [42].

The application of SIT against mosquitoes must take into account mass-rearing procedures, sterilisation methods, transport and release methods, and trapping systems [43]. The application of SIT in vectors requires the release of males only because it maximises the effectiveness of releases, the efficiency of breeding efforts, and manages the public perception and stringent regulations that exist even for the release of small numbers of potentially disease-transmitting females. One of the advantages of releasing sterile males is the control of cryptic breeding sites, as these males locate their mates who then lay non-viable eggs, allowing for more effective control of these sites which are difficult to control with insecticides [43].

Nowadays, the viability of SIT for mosquitos *Aedes* is being evaluated with pilot trials by institutions and governments from different countries, such as Brazil, China, Cuba, French Polynesia, Italy, Mauritius, Mexico, Reunion, Singapore, Spain, Sudan, Thailand, and the United States [43].

#### *2.2.2 Incompatible insect technique (IIT)*

This technique of incompatible insects is related to SIT, as instead of releasing sterile males, Wolbachia-infected males are released which, after mating with a wild female, do not produce viable offspring [44]. This technique exploits the biological mechanism of cytoplasmic incompatibility present in *Wolbachia* to produce infected but not sterilised males as is the case with radiation and genetic modification which impose a large fitness burden or suffer from complicated regulatory pathways [44]. Recently, studies combining the SIT and Incompatible Insect Technique (IIT) have been carried out for *Ae. aegypti* and *Ae. albopictus* [45, 46]. This technique involves triple-infecting laboratory mosquitoes with *Wolbachia* strains (*Ae. albopictus* is naturally infected with wAlbA and wAlbB; the triple infection incorporates wPip) and irradiating the pupae to sterilise females. However, for this combination to be deemed the safest solution for the suppression of vector populations, perfect sexual identification mechanisms must be developed [46].

#### *2.2.3 Control by genetic manipulation*

Among the genetic control techniques, the most advanced strategy is the release of insects carrying a self-limiting gene (RISL) [10]. According to Zheng et al. [46], this method consists of inserting a self-limiting gene into the genome of the vector that interrupts its development, thus preventing it from reaching the adult stage, and then mass-producing them and releasing them into the wild to compete with wild populations. The purpose of this technique is to suppress the local populations and reduce the likelihood of disease transmission. It should be noted that sustained release of transgenic males is necessary to maintain suppression of wild *Ae. aegypti* populations. However, one of the disadvantages of this technique is that males carrying the lethal gene may be less competitive in mating than wild males, leading to low population suppression [10].

At the present time, mosquito control techniques, such as genetic handling strategies to produce "female killers", consisting of releasing males with a gene that is lethal to the females and will cause conditioned sterilisation or selective lethality, continue to evolve [47]. Another technique is Homing Endonuclease Genes (HEG),

which grant resistance to infection and determine fertility and sex differentiation in mosquitoes are also being used [48]. Finally, a genetic technique based on CRISPR, to propagate target genes through traditional Mendelian inheritance, is being developed under laboratory conditions. Its most recent advancement has a binary focus to simultaneously interrupt the genes that are essential for female viability and male fertility of *Ae. aegypti*, that can suppress and eliminate populations at any life stage resulting in the survival of sterile males. It requires two breeding strains, one expressing Cas9 and the other expressing guide RNAs (gRNAs) known as precision-guided sterile insect technique (pgSIT), which compared with SIT and IIT not require the use of radiation, *Wolbachia*, or antibiotics, and will not persist in the environment longterm [49].

### **2.3 Chemical control**

### *2.3.1 Traditional control*

Insecticides have played a predominant role in vector control programmes. Accordingly, controlled release larvicide temephos has been commonly used in *Ae. aegypti* larvae control. In regards to adult mosquito control, it has been carried out through ultra-low volume (ULV) spatial spraying with organophosphate insecticides, such as malathion and pyrimiphos-methil, and with pyrethroids, such as deltamethrin, cypermethrin, and cyfluthrin, in addition to personal protection with repellents [50]. Recently, PAHO has recommended indoor residual spraying (IRS) of insecticides in urban areas to control *Ae. aegypti*, a measure in place to control malaria vectors [51]. However, intensive use of insecticides has led to the development of resistance in vector populations [52], environmental pollution, destruction of beneficial fauna, and the subsequent loss of balance in different ecosystems [53].

#### *2.3.2 Control by autodissemination augmented by males (ADAM)*

At present, innovative strategies using biorational insecticides, which present minimal impacts on human beings and the environment, are evolving. The most interesting and promising strategy implemented has been the Autodissemination Augmented by Males (ADAM), which consists of the use of males *Ae. aegypti* or *Ae. albopictus* that have been mass-reared, dusted with pyriproxyfen (PPF) or methoprene (insect growth regulators) and then released and thus transfer lethal concentrations directly contaminate larval habitats or indirectly contaminate them via mating with females that then visit such sites [54]. This substance acts analogously to the juvenile hormone and interferes in the metamorphoses of *Aedes* larvae in breeding grounds or resting grounds during oviposition, thus, reducing mosquito populations [55]. These compounds have advantages that include their "high toxicity to immature mosquitoes, low toxicity to adult mosquitoes, a substantial amount of prior research and environmental assessment, and its classification as a low risk insecticide" [53]. This strategy has been successfully implemented under field conditions in *Ae. aegypti* control in Brazil, Peru, and the USA [54, 56–58]. Likewise, it has been tested for *Ae. albopictus* under laboratory and field conditions in the USA [53, 59]. Brelsfoard et al.; [58] clarify that this technique should be integrated into existing control programmes and can be overlaid onto existing autocidal methods (e.g., SIT and IIE) and can offer effective control to the small and cryptic containers.

### *2.3.3 Development of the new insecticides*

New insecticides have been developed to control mosquito resistance. Fludora Co-Max®, for example, combines two active ingredients with different modes of action (flupyradifurone, a butenolide, and transfluthrin, a pyrethroid), and has shown 100% mortality of resistant *Aedes* in the USA and Brazil through vehicle-mounted ULV spraying [60]. Another laboratory-tested insecticide that has shown 100% mortality in *Ae. aegypti* control is chlorfenapyr (CFP), a pyrrole insecticide repurposed from agriculture that could potentially be used for indoor residual spraying [60].

Studies have shown mortality of *Ae. aegypti*, *Ae. albopictus* and other vector's larvae with essential oils or plant extracts such as *Pergularia daemia* [61], *Plumeria rubra* [62], *Gmelina asiatica* [63], *Annnona squamosa* [64], *Polianthus tuberosa* [65], *Ambrosia arborescens* [66], *Solanum mammosum* [67], *Annona glabra* [68], *Plumbago auriculata* [69], and *Marsilea quadrifolia* [70]. All these studies show promise for the development of new insecticides for vector control.

### *2.3.4 Use of nanotechnology in the manufacture of plant-based products*

The development of new compounds from plants is motivated by increasing resistance to insecticides. As of late, there have been developments in mosquito larvicides made from silver nanoparticles [AgNPs] synthesised by plants, this method is rapid, cost-effective, environmentally friendly, and safe for humans and it has exceptional properties such as bacterial activity, high resistance to oxidation and high thermal conductivity. The larvicidal effect is still unknown but it is assumed that AgNPs penetrate through the larval membrane causing death [71].

#### **2.4 Physical control**

Several strategies for physical control of *Ae. aegypti* have been developed, that is, physically interrupting larvae and pupae respiration through disturbances in air contact above the water surface with oils, surfactants, and polystyrene pearls [72] and mechanical barriers, such as lids, curtains, mosquito nets, and ovitraps [73].

New ovitraps are promising tools for the control, recent studies in laboratory and field, showed that the autocidal gravid ovitraps (AGO) which attract and capture gravid females looking for a place to lay their eggs [74] and attractive toxic sugar bait (ATSB) that use the staple sugar feeding behaviour of males of *Ae. aegypti* in nature for their control [75] have been shown to reduce the *Ae. aegypti* population.

Acoustic larvicidal are innovative technologies designed for the physical control of *Ae. aegypti*. This system uses sound waves that transmit acoustic energy across the water by causing rapid and traumatic vibrations, thus breaking the walls of the dorsal tracheal trunk and resulting in instant death. Furthermore, the lowest resonating energies affect other structures, inhibiting the emergence of larvae. In conclusion, mortality is the result of both effects [76, 77]. The lowest frequencies (20–50 kHz) are known to be more effective as larvicidal than higher frequencies (>100 kHz) [77]. However, when other aquatic insects, such as Diptera, Hemiptera, and Coleoptera that have open tracheal systems, are exposed to the acoustic beam for a prolonged period they may be adversely affected [78]. But other studies in which this acoustic control system has been used have shown high larval mortality of *Ae. aegypti* and *Cu. quinquefasciatus* (100%), both laboratory and field conditions and did not affect

larvae predators, such as *Methanofollis formosanus*, *Poecilia reticulata* (Guppy fish), *Xiphophorus helleri* (Swordtail fish), *Micronecta grisea* (small water-boatmen) and *Indoplanorbis exustus* (freshwater snails) [76, 77, 79]. The promising nature of this system resides in the low risk of resistance development in target mosquito populations and this equipment can be used as a complement to the chemical or biological larvicides that have been used in control programmes under specific operational conditions [78].

#### **2.5 Cultural control**

### *2.5.1 Communication for mobilisation and behavioural impact (COMBI)*

Since 2003, WHO has promoted the integrated management strategy for dengue prevention and control. Within this strategy is Communication for Behavioural Impact (COMBI) methodology. According to Parks and Lloyd [80], COMBI plans communication and social mobilisation that promotes the acquisition of recommended healthy practices and encourages the adoption and maintenance of those behaviours by involving individuals and families through the promotion of objectives with integrated strategies that contribute to the achievement of such objectives. Behavioural change has been shown to be essential for the prevention of arboviruses, such as dengue, so it is important to have a better understanding of the perception of the risk of becoming ill. This approach has been implemented in Asia and the Americas for several years, leaving lasting lessons in which goals, achievements, and difficulties were identified [81–83]. Lessons learned in the Americas show that it has been evidenced that meeting behavioural objectives, integration of multidisciplinary teams, formative research, community mobilisation, and advocacy have favoured the implementation of COMBI, however, the constant change of personnel, lack of political will due to the fact that these programmes are difficult to implement because they take longer to reflect impact compared to a low-cost approach Information, Education and Communication (IEC), which is limited to communication through home visits, leaflets and different vertical actions [83].

#### *2.5.2 Approaches to social participation*

Community involvement is a key element for the successful control of Ae. aegypti, studies conducted mainly in the 2000s in several countries suggest that integrated community-based control of *Ae. aegypti* under different approaches reduced vector density and had an impact on dengue transmission [84–88]. These approaches, such as Socialisation of Evidence for Participatory Action [SEPA], have been used in mobilising communities for vector control in Nicaragua and Mexico, known as The Green Way, which is based on cluster randomised controlled trial added community engagement in dengue prevention. These studies aimed to prove the hypothesis that informed mobilisation adds to the effectiveness of programmes managed by local governments [89–93]. In Cuba, other approaches have been implemented, such as Rifkin's approaches to community participation in health programmes, Shediac-Rizkallah and Bone's approaches to sustainability [86, 94, 95], and the evaluation of community participation in health programmes and the theory of education [96–98]. In China, Bishop's five-step learning process approach for community empowerment in vector control was applied [99].

### *2.5.3 Ecosystem approaches to health*

In recent years, three approaches to community participation in *Ae. aegypti* control have gained relevance: eco-health, the socio-ecological system, and the political theory of health.

Eco-health integrates factors from the micro and macro contexts, that is, ecological [latitude, altitude, temperature, humidity, and precipitation], biological [natural and artificial surroundings related to vector and virus], and social factors [demographic, economic, political, and cultural, including programmes for the prevention and control of dengue] [100]. Studies have been carried out in the Americas and Asia [101, 102] to determine the weight of ecological and social factors in dengue vector infestation, and to analyse their implementation [103].

Based on systemic thinking, the socio-ecological system approach makes human beings a part of nature [104]. This model focuses on the interactions between human and natural systems along with a series of spatial, temporal, and organisational scales; for instance, the individual, the community, and the society [105]. It has been implemented, for the most part, in the city of Machala, Ecuador [106–109].

The political ecology of health analyses how health is positioned within socioenvironmental networks that lead to illness and examines the contextual realities in decision making for resource use in health matters. Constructs about health authored by individual participants and institutions through the relations between social and environmental systems emerge within these networks [110]. In Ecuador, researchers tried to establish the social and environmental interactions of illnesses transmitted by *Ae. aegypti*, and concluded that the vulnerability of the population to these arboviral diseases stems from the socio-political limitations of community action and poverty, combined with a fragile public health system that undertakes incomplete, sporadic efforts to control such diseases [111]. Another recent study that has used this approach in the city of Maputo, Mozambique [112], took into consideration the patterns of distribution and storage of water, as well as the biophysical characteristics that make stored water more attractive to vector *Ae. aegypti*. In Maputo, all families store water, but different communities do it in different ways depending on their socio-economic situation. Therefore, it is dependent on an explicit analysis of power relations. Poor people store water both inside and outside of their homes, while wealthier people do it in closed tanks on top of their residences. The latter do not see nor live close to the stored water.
