The role of arthropods in the transmission of diseases to humans was first elucidated in the late 19th and early 20th centuries. Since effective vaccines or drugs were not always available for the prevention or treatment of these diseases, control of transmission often had to rely principally on control of the vector. Early control activities included the screening of houses, the use of mosquito nets, the drainage or filling of swamps and other water bodies used by insects for breeding, and the application of oil or Paris green to breeding places. Following the discovery of the insecticidal properties of dichlorodiphenyltrichloroethane (DDT) in the 1940s and subsequent discovery of other insecticides, the focus of malaria vector control shifted to the deployment of insecticides to target both the larval and adult stages of mosquito vectors.
Nowadays, it is well established that effective vector control programmes can make a major contribution towards advancing human and economic development. Aside from direct health benefits, reductions in vector- borne diseases enable greater productivity and growth, reduce household poverty, increase equity and women’s empowerment, and strengthen health systems (6). Despite the clear evidence in broad support of vector control efforts, the major vector-borne diseases combined still account for around 17% of the estimated global burden of communicable diseases, claiming more than 700 000 lives every year (7). Recognizing the great potential to enhance efforts in this area, WHO led the development of the Global vector control response 2017–2030, which is outlined in the subsequent section.
MALARIA VECTOR CONTROL GUIDELINES
The control of malaria, unlike that of most other vector-borne diseases, has seen a major increase in financial resources since 2000, leading to a significant reduction in the global burden. Between 2000 and 2015, the infection prevalence of P. falciparum in endemic Africa was halved and the incidence of clinical disease fell by 40% (8). Malaria control interventions averted an estimated 663 (credible interval (CI) 542–753) million clinical cases in Africa, with ITNs making the largest contribution (68% of cases averted). IRS contributed an estimated 13% (11–16%), with a larger proportional contribution where intervention coverage was high (7).
Global vector control response 2017–2030
In 2017, the World Health Assembly welcomed the Global vector control response 2017–2030 (6) and adopted a resolution to promote an
integrated approach to the control of vector-borne diseases. The approach builds on the concept of integrated vector management (IVM),5 but with renewed focus on improved human capacity at national and subnational levels, and an emphasis on strengthening infrastructure and systems, particularly in areas vulnerable to vector-borne diseases.
The vision of WHO and the broader infectious diseases community is a world free of human suffering from vector-borne diseases. The ultimate aim of the Global Vector Control Response is to reduce the burden and threat of vector-borne diseases through effective, locally adapted, sustainable vector control in full alignment with Sustainable Development Goal 3.3. The 2030 targets are: to reduce mortality due to vector-borne diseases globally by at least 75% (relative to 2016); to reduce case incidence due to vector-borne diseases globally by at least 60% (relative to 2016); and to prevent epidemics of vector-borne diseases in all countries. Detailed national and regional priority activities and associated interim targets for 2017–2022 have also been defined.
Effective and locally adaptive vector control systems depend on two foundational elements: i) enhanced human, infrastructural and health system capacity within all locally relevant sectors for vector surveillance and vector control delivery, monitoring and evaluation; and ii) innovation for the development of new tools, technologies and approaches and increased basic and applied research to underpin optimized vector control.
Both elements are required to ensure the maximum impact of sustainable vector control by using an evidence-based approach to planning and implementation.
5 WHO defines IVM as a rational decision-making process to optimize the use of resources for vector control.
Effective and sustainable vector control is achievable only with sufficient human resources, an enabling infrastructure and a functional health system. Countries should conduct a vector control needs assessment (9) to help appraise current capacity, define the requisite capacity to conduct proposed activities, identify opportunities for improved efficiency in vector control delivery, and guide resource mobilization to implement the national strategic plan.
Action is required in four key areas (pillars) that are aligned with IVM:
i) strengthening inter- and intra-sectoral action and collaboration;
ii) engaging and mobilizing communities; iii) enhancing vector surveillance and monitoring and evaluation of interventions; and iv) scaling up and integrating tools and approaches.
In some settings, vector control interventions can reduce transmission and disease burden of more than one disease. Examples include ITNs against malaria and lymphatic filariasis (in settings where Anopheles mosquitoes are the principal vector), IRS against malaria and leishmaniasis in India, and larval control for malaria and dengue vectors in cities with particular vector habitats. Approaches effective against Aedes spp. mosquitoes can have an impact on dengue, chikungunya, Zika virus disease and possibly yellow fever where their vectors and distributions overlap. However,
programmes should avoid an approach that overlays multiple interventions to compensate for deficiencies in implementation of any one intervention;
this may divert resources and attention away from reaching the full impact of existing interventions and lead to resource wastage.
The decision to use a vector control intervention in a particular setting or situation should be based on clear evidence of its epidemiological efficacy. Implementation must be to a high standard and aim to achieve and maintain universal coverage of at-risk populations. Covering at- risk populations with evidence-based and cost-effective vector control interventions offers the greatest immediate opportunity to reduce infections and disease.