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Renewed push to strengthen vector control globally

Dr Pedro Alonso, Director, WHO Global Malaria Programme,
Dr Dirk Engels, Director, WHO Department of Control of Neglected Tropical Diseases (NTDs), and
Dr John Reeder, Director, TDR, Special Programme for Research and Training in Tropical Diseases

Commentary
6 June 2017

Vector control is the main method for tackling many of the world's major infectious diseases. When effective methods of targeting mosquitoes, flies, ticks, bugs, and other vectors that transmit pathogens are well implemented, lives have been saved and the health of millions has been protected.

Pedro Alonso, Director, WHO Global Malaria Programme
Pedro Alonso, Director, WHO Global Malaria Programme
WHO/M. Missioneiro

Between 2001 and 2015, two core methods of vector control—insecticide-treated bednets and indoor residual spraying of insecticides—prevented an estimated 663 million cases of malaria in sub-Saharan Africa (1). Major reductions in onchocerciasis, visceral leishmaniasis, and Chagas disease have also been achieved through large-scale vector control (2).

However, controlling vectors is a constant challenge, and both old and emerging diseases are exposing new threats. The recent outbreak of Zika virus disease (3) and the re-emergence of yellow fever (4), along with an increase in cases of dengue and chikungunya, have highlighted the importance of sustainable vector control and the urgency of boosting global capacity to respond to these threats.

Today more than 80% of the world's population is at risk of vector-borne disease, with half at risk from two or more diseases (5). Many of these diseases are concentrated in the poorest communities in tropical and subtropical regions; they cause unacceptable mortality and morbidity and impede economic growth (6), (7).

Dirk Engels, Director, WHO Department of Control of Neglected Tropical Diseases (NTDs)
Dirk Engels, Director, WHO Department of Control of Neglected Tropical Diseases (NTDs)
WHO

The pathogens of malaria, dengue, lymphatic filariasis, chikungunya, Zika virus disease, yellow fever, Japanese encephalitis, and West Nile fever are transmitted to humans by mosquitoes. Onchocerciasis is carried by blackflies; leishmaniasis by sandflies; Chagas disease by triatomine bugs; Lyme borreliosis and encephalitis by ticks; human African trypanosomiasis by tsetse flies; and schistosomiasis by snails.

Addressing the World Health Assembly in 2016, WHO's Director-General expressed grave concern over the poor state of vector control globally (8). A new and comprehensive approach to preventing diseases and responding to outbreaks was clearly needed—one that engages multiple sectors and communities and is based on the best available data.

1 year later on May 30, 2017, the 70th World Health Assembly welcomed the strategic approach outlined in a new WHO Global Vector Control Response (GVCR) for 2017–2030 (9). The response aims to reduce the burden and threat of vector-borne diseases through effective, locally adapted, and sustainable vector control. It is not a blueprint for attacking a single disease but, rather, a method for tackling multiple vectors and diseases that requires action across many sectors beyond health, including environment, urban planning, and education. We believe this approach will use resources more cost-effectively and yield more sustainable results.

John Reeder, Director, TDR, Special Programme for Research and Training in Tropical Diseases
John Reeder, Director, TDR, Special Programme for Research and Training in Tropical Diseases
WHO/I. Suder-Dayao

Success will depend on strengthening the capacity and capability of country programmes, which have suffered from staff reductions and an erosion of vector control expertise in recent decades. Basic and applied research also need a boost to supply the evidence base required for disease control and elimination.

Continued investment in innovation is essential; promising new interventions at various stages of development include new insecticides, spatial repellents, odour-baited traps, improved house screening, Wolbachia-based biocontrol, and transgenic mosquitoes. Once WHO confirms their safety, efficacy, quality, and utility, these interventions should be deployed in the field and integrated into vector-control programmes to maximise benefit.

"Controlling vectors is a constant challenge, and both old and emerging diseases are exposing new threats."

Pedro Alonso, Director, WHO Global Malaria Programme,
Dirk Engels, Director, WHO Department of Control of Neglected Tropical Diseases (NTDs), and
John Reeder, Director, TDR, Special Programme for Research and Training in Tropical Diseases

The GVCR prioritises necessary country actions under four pillars. First, strengthening intersectoral and intrasectoral action because vector-borne disease control is a shared responsibility of all members of society, and collaboration beyond the health sector is crucial. Second, engaging and mobilising communities for sustainability and to build resilience against future disease outbreaks. Third, enhancing surveillance and monitoring to trigger early action if vector populations increase, and to identify if interventions are not working as expected. Finally, evidence-driven scale-up and integration of vector-control interventions to maximise impact on disease while minimising impact on the environment.

Such action is reliant on strong country leadership and support. Vector control should become a core element of national health strategies in affected and at-risk countries and an integral part of national plans to implement the 2030 Agenda for Sustainable Development. Effective communication across ministries, increased financing, capacity building and staff retention, and revision of legislative controls for public health are also important.

The GVCR has ambitious but attainable goals: to reduce mortality from vector-borne diseases by at least 75% and incidence by at least 60% by 2030, and to prevent epidemics in all countries. The cost of priority activities to boost staffing, surveillance, monitoring, and coordination is estimated at just 5 cents per person at risk per year, or about US$330 million annually worldwide (9). Compare this fairly modest amount to the more than $4 billion required each year globally for vector control against malaria, dengue, and Chagas disease alone (2), (10). Integrated and locally adapted vector control is expected to not only save lives and reduce ill health, but also to improve efficiency and ultimately save money.

The GVCR was unanimously supported by WHO Member States at the 2017 World Health Assembly and promises a new dawn for the control and elimination of vector-borne diseases. WHO is committed to lead this effort and protect the health of populations around the world.


References

(1) Cibulskis, RE, Alonso, P, Aponte, J et al. Malaria: global progress 2000–2015 and future challenges. Infect Dis Poverty. 2016; 5: 61

(2) WHO. ((accessed May 31, 2017).)Investing to overcome the global impact of neglected tropical diseases. Third WHO report on neglected tropical diseases. World Health Organization, Geneva; 2015
http://www.who.int/neglected_diseases/9789241564861/en/

(3) Pan America Health Organization and WHO. Zika epidemiological update. ((accessed May 31, 2017).)
http://www2.paho.org/hq/index.php?option=com_content&id=11599&Itemid=41691

(4) Pan America Health Organization and WHO. Yellow fever epidemiological update. ((accessed May 31, 2017).)
http://www2.paho.org/hq/index.php?option=com_docman&task=doc_view&Itemid=270&gid=39764&lang=en

(5) Golding, N, Wilson, AL, Moyes, CL et al. Integrating vector control across diseases. BMC Med. 2015; 13: 249

(6) WHO. World malaria report. 2016. World Health Organization, Geneva; 2016

(7)WHO. Integrating neglected tropical diseases in global health and development. Fourth WHO report on neglected tropical diseases. World Health Organization, Geneva; 2017

(8) Chan, M. Address to the Sixty-ninth World Health Assembly. ((accessed May 31, 2017).)
http://www.who.int/dg/speeches/2016/wha-69/

(9) WHO. ((accessed May 31, 2017).)Global vector control response 2017–2030. World Health Organization, Geneva; 2016
http://www.who.int/malaria/global-vector-control-response/

(10) Patouillard, E, Griffin, JT, Bhatt, S, Ghani, AC, and Cibulskis, R. Global investment targets for malaria control and elimination 2016-2030. BMJ Global Health. 2017; 2: e000176