Current gaps and challenges regarding vector control in the Americas Anubis Vega Rúa Institut Pasteur of Guadeloupe MEETING OF THE INSTITUT PASTEUR INTERNATIONAL NETWORK (RIIP) – AMERICAN REGION (Sao Paulo, 3-5 July, 2019)
Vector-borne diseases (VBD): a major and global problem 17% of the estimated global burden of infectious diseases (> 700 000 deaths/year) 80% of the world's population is at risk of one or more vector-borne disease. Malaria, Lymphatic filariasis, dengue, leishmaniasis, japanese encephalitis, yellow fever, Chagas disease, human African trypanosomiasis and onchocerciasis WHO(2017) 2
Vector-borne diseases in the Americas Leishmaniasis Malaria Lymphatic filariasis • 21 countries • 19 countries • Endemic in 4 countries • 145 million at risk • 64,000 cases/year • 12.6 million at risk • 469,000cases (2012) • 7% fatality rate Chagas disease Yellow fever Dengue • 21 countries Since 2016: • 500 million at risk • 65 million at risk • 5 countries reporting • 2.3 million cases (2013) • 6-8 million cases • ~2210 cases • Hyperendemic • ~760 deaths Chikungunya West Nile Zika virus USA (1999-2011): • >43 countries/territories • 48 countries/territories • ~4 millions cases • > 1 million cases • > 750 000 cases • 1261 deaths Randolph & Rogers Nat Rev Microbiol (2010), PAHO(2019), WHO (2019), Espinal et al Rev Panam Salud Publica (2019)
Vector-borne diseases in the Americas Leishmaniasis Malaria Lymphatic filariasis • 21 countries • 19 countries • Endemic in 4 countries • 145 million at risk • 64,000 cases/year • 12.6 million at risk • 469,000cases (2012) • 7% fatality rate Chagas disease Yellow fever Dengue • 21 countries Since 2016: • 500 million at risk • 65 million at risk • 5 countries reporting • 2.3 million cases (2013) • 6-8 million cases • ~2210 cases • Hyperendemic • ~760 deaths Chikungunya West Nile Zika virus USA (1999-2011): • >43 countries/territories • 48 countries/territories • ~4 millions cases • > 1 million cases • > 750 000 cases • 1261 deaths Randolph & Rogers Nat Rev Microbiol (2010), PAHO(2019), WHO (2019), Espinal et al Rev Panam Salud Publica (2019)
The common point: the vector
The common point: the vector
Vector Control Integrated Vector Management (IVM) William Crawford Gorgas Rationale : optimal use of resources for vector control. Overcome the challenges experienced with single-intervention approaches Cost-effectiveness Sustainability Efficacy Ecological soundness WHO (2019), Vega-Rúa & Okeh (2019)
The structure of an IVM programme
Examples of major successes achieved through vector control Global Vector Control Response 2017 – 2030, WHO , (2017)
Examples of major successes achieved through vector control Global Vector Control Response 2017 – 2030, WHO , (2017)
Contemporary increase of certain VBDs in the Americas DENV Suspected cases Deaths caused by dengue PAHO(2019)
Challenges for IVM are greater today Commercial/touristic air travel network ZIKV spread by air travel network Urbanization-Population growth Gardner et al Plos Neg Trop Dis (2018)
Challenges for IVM are greater today Global trade Colonization of the Americas by Ae. albopictus Carvalho et al Mem Inst Osw Cruz (2018)
Challenges for IVM are greater today Climate change Potential distribution of vectors under current and future climate scenarios in Ecuador Escobar et al. Sci Rep (2016)
Contemporary context increases the cost of IVM
Contemporary context increases the cost of IVM
Physical vector control: the oldest method Mechanical elimination of breeding-sites (source reduction) Improvement of water supply and water-storage systems Waste management
Anti-Vectorial housing: alternative for simultaneous VBD reduction Housing Vector house Humidity entry [CO 2 ] Temperature Housing Improvement Program for Chagas Disease Control Gambia: Well-fitted doors reduced An. gambiae house entry by 96% Velleda dos Santos et al. Rev Soc Bras Med Trop (2016) Jatta et al. Lancet Planet Health (2018)
Anti-Vectorial housing : gaps and challenges Published and grey literature between Jan 1, 1980, and Nov 30, 2015 (updated on April 2, 2017) Horstick & Runge-Ranzinger Lancet Inf Dis (2017)
Anti-Vectorial housing : gaps and challenges Published and grey literature between Jan 1, 1980, and Nov 30, 2015 (updated on April 2, 2017) Few trials with appropriate efficacy assessment GAP GAP Horstick & Runge-Ranzinger Lancet Inf Dis (2017)
Anti-Vectorial housing : gaps and challenges Impacts simultaneously several vectors Increase the number of trials-combination with other vector control methods Standardization of the efficiency assessments Costly Strong Political and Community economical involvement support Large-scale implementation difficult Horstick & Runge-Ranzinger Lancet Inf Dis (2017)
Chemical vector control methods: history and limits Lack of specificity Negative effects on the environment/human health Resistance … XVII e 1965 1980’s 2002 2013-2015 2016 Sautet, 1951 Jousset, 1981 Quirin et al, 2004 Leparc-Goffart et al, 2014 Nicolas et al, 2003 1986: Deltamethrin 1951: DDT 1969: Malathion & 2009 & 2010: Temephos & Temephos Malathion Interdiction
Multiple insecticide resistance in Ae. aegypti from Guadeloupe Ae. aegypti resistance levels Resistance: RR50 > 1 or KRR50 > 2 Goindin et al. J Inf Dis Pov (2017)
Insecticide resistance is widespread in the Caribbean CARPHA IVM Toolkit (2017)
Insecticide resistance is widespread also in the Americas The level of Ae. aegypti resistance to The frequency of resistance to temephos, 2006 – 2015 deltamethrin in Ae. aegypti , 2006 – 2015. Adult mortality Resistance index (LC 50 ) (%) Reference strain: Rockefeller susceptible strain Moyes et al. Plos Neg Trop Dis (2017)
Insecticide resistance mechanisms in the Americas Vézilier et al. Evol Applic (2012) , Moyes et al. Plos Neg Trop Dis (2017)
Distribution of Ae. aegypti and Ae. albopictus ion the Americas Ae. aegypti Ae. albopictus Kraemer et al. eLIFE (2015)
Locations of bioassay data for the organophosphates and pyrethroids 2006 to 2015 Moyes et al. Plos Neg Trop Dis (2017)
Insecticide resistance poorly studied for Ae. albopictus GAP GAP Moyes et al. Plos Neg Trop Dis (2017)
What have we learned? Major questions we should ask: Was the strategy we used for chemical vector control appropriate? Which have been the results? Did we collect all the needed data regarding vector populations before the interventions? Do we know which strategies have worked the best and where? Did we monitor the populations to see if adaptations or modifications of the strategies are needed? Do we know how resistance evolved or may evolve? GAP GAP
Challenges of chemical vector control methods in the Caribbean GAP GAP Legislation not adapted to local needs Lack of standardized resistance Different vector Different legislations assessment and surveillance control strategies “Isolation” - Information sharing (i.e. good practices, feedback) Transfer of competence for capacity building Networks (i.e. WIN)
Insecticide resistance can modify vector competence and behavior Insecticide resistance Behavior Vector competence Activity (early or late biting) Increase of biting events outdoors Differential perception of human odors Susceptible Resistant Stanczyk et al. Sci Rep (2019) Carrasco et al Curr Op Ins Cont (2019) Alout et al. Plos One (2013) IVM strategies should evolve along with their vectors
Biological vector control methods targeting immature vector stages Larvicides and Oviposition deterrents Predators of immature stages Benelli et al. Insects (2016)
Biological vector control methods: pros, cons and knowledge gaps Larvicides and Oviposition deterrents Predators of immature stages .>80 species .Limited information .Low remanence .Specificity? .Resistance .Nanomosquitocides .Large breeding-sites characterization? GAP GAP Benelli et al. Insects (2016)
Biological vector control methods: pros, cons and knowledge gaps Larvicides and Oviposition deterrents .Used in 60 countries .Vietnam (2003-2000)! .Small breeding-sites . Mosquito habitats .Mass-rearing suitability Predators of immature stages Specificity? Benelli et al. Insects (2016)
Biological vector control methods: pros, cons and knowledge gaps Cryptic breeding-sites? Larvicides and Oviposition deterrents Predators of immature stages Benelli et al. Insects (2016)
Biological vector control methods: pros, cons and knowledge gaps Entomopathogenic fungi « One Health » Different mosquito lethal toxins Less selective pressure for Releasing “modified insects” resistance Resistance evolution slower than resistance to chemical insecticides . Natural variations of viability, infectivity, and persistence of fungal GAP GAP spores in field populations . Delivery methods for increased specificity and large-scale application Benelli et al. Insects (2016) Scholte et al. Acta Trop (2007), Knols et al. Future Microbiol (2010), Benelli et al. Insects (2016)
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