Integrated Vector Control: Proven Methods or Miasmatic Vapors? A call to Action.

When it comes to malaria control, you need to talk tough.[i] That was the position Dr. Arata Kochi took shortly after accepting his posting as Director of the Malaria Division of the World Health Organization during the second half of the 1990s. Dr. Kochi was worried that in the war against malaria silver bullets inevitably morph into rubber ones as the parasite and its vectors develop resistance to every miracle drug and pesticide that comes along.[ii] He explained his position very eloquently when he said "What needs to be done to tackle malaria has been known for years. Now, the WHO Global Malaria Programme is developing relevant strategies, tools and guidelines on ‘how’ this should be done".[iii] He further argued that "a wide range of effective tools for malaria prevention" and control were available, "though not always where most needed". Shortly thereafter, the Roll Back Malaria Campaign began.

Two decades later, the World Malaria Report of 2015 reported a fifty percent reduction in malaria.[iv] Unfortunately, the World Malaria Report of 2017 stated that the overall decline in "the global malaria burden had unquestionably leveled off and reversals in the gains achieved were beginning in some countries and regions".[v] In short, decades after the launching of the Roll Back Malaria Campaign and spending over one billion US dollars annually, mostly in Africa, malaria seems poised to return and continues to be one of the major contributors to poverty. In fact, malaria costs between 0.5 to 9% of the gross domestic product of African economies annually.[vi] These numbers may seem acceptably low to many, but a closer look reveals some staggering figures. With Africa's GDP estimated around 2,500 billion US Dollars,[vii] this figure represents loses between 4.2 and 23.5 Billion USD annually for every African country. And that is just to malaria! Adding the billions already spent on malaria in Africa produces mind-blowing figures.

When it comes to Dengue fever, the total cost of Dengue worldwide in 2013 was estimated at $US 8.89 Billion.[viii] Its burden far exceeds that from other viral illnesses and reports may still underestimate its total economic consequences.[ix] This in spite of the remarkable successes of the campaigns of the 1950s and 1960s that eradicated Aedes aegypti and urban yellow fever in the Americas. Unfortunately, after those extraordinary successes, now all the countries of the Hemisphere except for Bermuda, Canada, and Chile are infested.[x]

Zika, the most recent mosquito-borne disease to become headline news across the globe generated hundreds of cases of microcephalia and other neurological and physiological conditions, and losses in the billions of US dollars in a very short time and is considered by many physicians a sleeping giant.[xi]

And these are just the three main mosquito-borne diseases!

Getting to this point seems to stem all the way back to a comment made by the Isthmian Canal Commission during the early stages of the construction of the Panama Canal that "spending time and money chasing after mosquitoes would be to squander time and money in a most irresponsible fashion".[xii] Fortunately, Dr. William Gorgas proved them wrong, but only after overcoming significant resistance and obstacles.

Unfortunately for those who carry the yoke of malaria and other vector-borne diseases well into the Twenty First Century, integrated vector control does not play the same role it did during the early part of the previous century, when the World was unified against malaria and its vector. Perhaps the most tragic event in global public health was that the elimination campaigns against Aedes aegypti in Latin America during the 1960s were not maintained or extended.[xiii] Instead, they were considered no longer necessary and disbanded soon after victory was declared. Today, "the spread of Zika is the price being paid for a massive policy failure on mosquito control. Experts dropped the ball in the 1970s with regards to getting a handle on disease-carrying insects".[xiv]

Early in the Twenty First Century, integrated vector control was defined as the use of mosquito nets and a "stratified approach to residual house spraying".[xv] Larviciding and environmental management, such as drainage or control of water flow of rivers and other water bodies, "could be used to destroy mosquito larvae, but only in areas where breeding sites are well defined".[xvi] This position is in direct contradiction with the Seventh Report of the WHO Expert Committee on Vector Biology and Control of 1983. In it, the Expert Committee described the concept of integrated vector control as a "rational decision-making process to determine the most appropriate mix of interventions" drawing from resources beyond health that include "environmental management and biological control".[xvii] The Committee's approach to IVM was a multi-pronged, multi-disciplinary approach to vector population suppression. The Seventh Report also stated that "the considerable amount of available knowledge on vector control techniques is not being properly applied" due to a number of reasons, including the lack of well qualified and trained personnel.

Many countries facing the resurgence of vector-borne diseases are in the unenviable position of having to implement vector population suppression methods with little guidance as to what the "rational decision-making process" entails or what the available "optimal resources" include. Moreover, the methods that eradicated malaria vectors from over one hundred countries during the first half of the Twentieth Century are today not considered viable by those purported to be providing the guidance and recommending the tools. A good example of this is larval source management and larviciding. WHO's publication titled A toolkit for vector control management in sub-Saharan Africa,[xviii] published in 2016 and Larval Source Management, a supplementary measure for malaria vector control,[xix] published in 2013 provide good examples of operational shifts in malaria vector control with potentially disastrous consequences. WHO's publication on larval source management, for instance, considers LSM and larviciding as a "useful supplement in specific locations where vectors tend to breed in permanent or semi-permanent water bodies that can be readily identified and accessed, i.e. breeding sites which are ‘few, fixed and findable’”.[xx] This statement fails to acknowledge the momentous success of William Gorgas, Israel Kligler and Fred Soper, just to name three.

Dr. Gorgas's work against mosquitoes in Panama was instrumental to the completion of the Panama Canal.

Professor Israel Kligler and his team developed and delivered an integrated vector control program that eliminated malaria from Mandate Palestine in 1921. His triumph was praised by the Malaria Commission of the League of Nations in 1925 "as one that could be applied to malarious areas in other parts of the world.[xxi]  

Fred Soper eradicated Anopheles gambiae s.l. from a region in northern Brazil roughly the size of Togo in just under eighteen months and almost exclusively with LSM and larviciding in the latter part of the 1930s.[xxii] Soper later helped the Pan American Health Organization design a plan for the control of Aedes aegypti in the Americas that called for "an eradication strategy that involved universal coverage of all mosquito-breeding sites in every house in every infested locality in the country for total elimination of the vector, and subsequent ongoing surveillance to prevent reinfestation".[xxiii] He succeeded against malaria in Brazil and eradicated aegypti from South America. Yet, he described the campaign against aegypti as accidental because the plan was only to reduce vector densities in large cities".[xxiv]

WHO Offset Publication Number 1, published in 1973 as Manual on Larval Control Operations in Malaria Programmes [xxv] and WHO Offset Publication Number 66, published in 1982 as Manual on Environmental Management for Mosquito Control with special emphasis on malaria vectors [xxvi] are loaded with information, diagrams and recommendations still valid for the control of almost all mosquito vectors around the world; not just those in Africa. Both publications provided a wealth of information on the subject and were instrumental in the eradication of malaria vectors and other mosquitoes from many countries and regions during the course of the Twentieth Century. However, though published after years of field work and contain invaluable information, both are currently considered outdated and have fallen off the pages of history. The use of bacteria, insect growth regulators, drones, satellite imagery, remote sensing and the vast majority of the current tools in the mosquito control tool bag were but a science fiction dreams when these documents were published. Many of the materials mentioned in them have been discontinued or are no longer available, but the methods and procedures described in them could prove very useful today if deployed using current materials and technology.

These contradictions confuse many vector control program managers, many of whom are not intimately familiar with the operational details of vector control campaigns. They fail to take into account that current materials are far more target-specific and environmentally friendly than those of decades ago and discard the value and potential impact a rational decision-making and multi-disciplinary approach that deploys as many tools as possible can have on a vector population. Especially when they are deployed with or augmented by satellite imagery, remote sensing, pinpoint application using drones, etc.

There is no magic bullet in vector control, but the dwindling vector control arsenal. The increasing cost of developing new molecules with insecticidal action make imperative the implementation of a truly multi-disciplinary IVM approach that attacks the vector from many flanks. To do this, the current definition of IVM[xxvii] must be modified to provide better guidance. Integrated Vector Management should be: "a rational decision-making process to determine the most appropriate mix of interventions drawing on resources beyond health, both public and private. These include the use of LLIN, IRS, Larval Source Management, larviciding, environmental manipulation, Information, Education and Communication (IEC), etc. Otherwise, suboptimal use of available resources will continue and millions of people will remain vulnerable".

In 2018, after over a decade of spending over one billion US dollars a year on malaria, it continues to affect half the World’s population, claims the equivalent of about six 747 Jumbo jets full of people every day, and seems to be poised to make a devastating comeback. Furthermore, there is direct evidence that scaling back vector control is likely to lead to resurgence and a return to pre-intervention levels.[xxviii]

The mosquito control tool bag contains a large number of tools that can be used against adult and larval mosquitoes, yet the same two continue to be deployed even after decades of use and seldom in the same area. Albert Einstein, one of the most privileged minds humanity has known defined insanity as doing the same thing over and over expecting different results each time.[xxix]

It is time to change. In the words of Ronald Ross, malaria will continue until the mosquito is taken seriously.[xxx]

[i]     Kaiser Health News, Jun2 11, 2009; https://khn.org/morning-breakout/dr00038165/

[ii]    https://www.nytimes.com/2006/06/27/health/27prof.html

[iii]    https://www.who.int/whr/1999/en/whr99_ch4_en.pdf

[iv]  ISBN: 978 92 4 156515 8  https://www.who.int/malaria/publications/world-malaria-report-2015/report/en/

[v]    ISBN: 978 92 4 156552 3 https://www.who.int/malaria/publications/world-malaria-report-2017/report/en/

[vi]    https://www.statista.com/statistics/240665/gdp-of-africa/

[vii]   IBID

[viii]   https://www.cidrap.umn.edu/news-perspective/2016/04/study-says-dengue-affects-58-million-costs-9-billion-year

[ix]   https://www.ajtmh.org/content/journals/10.4269/ajtmh.2011.10-0503

[x]    https://www1.paho.org/english/gov/cd/doc162.pdf

[xi]   https://www.caribbean360.com/tag/zika/

[xii]  In The Path Between the Seas, David McCullough (1977)

[xiii]  Killeen, et. al. Parasites & Vectors 2013, 6:172; www.parasites&vectors.com/content/6/1/172

[xiv]  Dr. Margaret Chan's World Health Assembly address of 2016 https://www.bbc.com/news/health-36361326

[xv]   https://www.who.int/whr/1999/en/whr99_ch4_en.pdf

[xvi]  https://www.nytimes.com/2006/06/27/health/27prof.html

[xvii]  WHO Technical Report Series 688, 1983 (page 7)

[xviii] https://apps.who.int/iris/bitstream/handle/10665/250267/9789241549653-eng.pdf?sequence=1; ISBN 978 92 4 154965 3

[xix] https://apps.who.int/iris/bitstream/handle/10665/85379/9789241505604_eng.pdf?sequence=1; ISBN 978 92 4 150560 4

[xx]   Larval source management: a supplementary measure for malaria vector control: an operational manual. WHO 2013 ISBN 978 92 4 150560 4 https://apps.who.int/iris/bitstream/handle/10665/85379/9789241505604_eng.pdf?sequence=1

[xxi] https://malariaworld.org/blog/why-2013-jerusalem-conference

[xxii]  Anopheles gambiae in Brazil: 1930 -1940. The Rockefeller Foundation, New York City 1943

[xxiii] https://www1.paho.org/english/gov/cd/doc162.pdf

[xxiv] Fred Soper (1967) Bull. World Health Org., 36, 645-647

[xxv]  Manual on Larval Control Operations in Malaria Programmes, WHO, Geneva, 1973

[xxvi] Manual on Environmental Management for Mosquito Control with special emphasis on malaria vectors, WHO 1982; ISBN 92 4 170066 1

[xxvii] https://www.who.int/malaria/publications/atoz/who_htm_ntd_vem_2008_2/en/

[xxviii] https://malariajournal.biomedcentral.com/articles/10.1186/s12936-017-2051-1

[xxix] Ideas and Opinions by Albert Einstein 1954 Crown Publishers, Inc.

[xxx] Mosquito Brigades and How to Organize Them Ronald Ross, Longmans, Green and Co., London: George Phillip & Son 1903