Global Health Impacts of Vector-Borne Diseases Workshop Summary (2016) / Chapter Skim
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A3 - The Intensifying Storm: Domestication of Aedes aegypti, Urbanization of Arboviruses, and Emerging Insecticide Resistance - Barry J. Beaty, William C. Black IV, Lars Eisen, Adriana E. Flores, Julin E. Garca-Rejn, Mara Loroo-Pino, and Karla Saavedra-Rodriguez
A3 - The Intensifying Storm: Domestication of Aedes aegypti, Urbanization of Arboviruses, and Emerging Insecticide Resistance - Barry J. Beaty, William C. Black IV, Lars Eisen, Adriana E. Flores, Julin E. Garca-Rejn, Mara Loroo-Pino, and Karla Saavedra-Rodriguez
Pages 126-160
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. The situation is further complicated by the concomitant reduction in medical entomologists, vector biologists, and vector control personnel available to address VBD emergencies.
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The emergence and spread of epidemic dengue and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) in the Americas in the 1980s and the emergence of CHIKV in the Caribbean in 2013 and its rapid spread throughout tropical America are examples of the extraordinary potential of urbanized, Ae.
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aegypti will likely exacerbate this situation. In the following, we will principally focus upon entomological factors in the super nidus that conditioned emergence of epidemic dengue and DHF/DSS and chikungunya in Latin America.
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Vector competence is a component of the vectorial TABLE A3-1 Aedes aegypti -- Behavioral and Biological Factors Contributing to the Extraordinary Vectorial Capacity for Arboviruses Anthropophily: Feeds preferentially on humans, and when humans are available, zoophily is minimal. In addition, sugar feeding is very limited.
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The super nidus with its hyperabundant Ae. aegypti and burgeoning susceptible human populations provides unprecedented receptivity to arbovirus spillover into the urban cycle and also promotes opportunities for spillback into sylvatic cycles.
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. Clearly the expanding super nidus is even more receptive to emergence and urbanization of DENV from sylvatic cycles.
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and its explosive spread throughout Latin America are the latest manifestations of urbanization and spread of the virus. Considering the size of the super nidus in Latin America, it is likely that CHIKV will become endemic in the tropical Americas as it has in Asia following its emergence there (Nasci, 2014; Weaver, 2014)
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The dramatic expansion of the super nidus and its increasing encroachment on sylvatic cycles of other important arboviruses provides unprecedented opportunities for arbovirus urbanization. For example, Ae.
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Viral Determinants of Dengue Hyperendemicity Molecular epidemiological studies were conducted to investigate the viral determinants of the emergence of epidemic dengue and DHF/DSS as major public health problems in Mexico (Diaz et al., 2006)
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The collapse of sustainable vector control 2. Introduction and trafficking of vectors 3.
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aegypti, and current vector control programs have not stemmed the rising tide of the dengue pandemic. These control programs typically include activities to control both immature and adult stages of Ae.
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. Such trafficking potential threatens sustainability of vector control.
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Competence of vectors for virus transmission Vector competence is a critical component of the transmission potential of an arbovirus and may contribute significantly to the heterogeneities seen in DENV transmission. Concomitantly with our breeding structure studies, we characterized heterogeneities in vector competence of Mexican populations of Ae.
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. The mosquito populations north and south of the NVA also differed in their vector competence for DENV-2 (Lozano-Fuentes et al., 2009)
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Efficient and rapid productive infection of vectors could be major determinants of the genetic sweep of the newly introduced genotypes. Identification of genetic markers for vector competence in mosquitoes could be exploited as a marker for risk assessment and surveillance programs for improved and targeted vector control.
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aegypti breeding sites were common. In contrast, in the Mexican City, there were many DENV infections, but mosquito breeding site control was more effective than in the U.S.
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aegypti, and initiate an intradomiciliary cycle. Schools are clearly an important target for dengue vector control.
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showed promise in reducing DENV infections (Kroeger, et al., 2006) , we conducted a Casa Segura study in Mérida City to determine the potential to reduce intradomiciliary DENV transmission through ITC use in individual homes (Loroño-Pino et al., 2013)
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aegypti females, emphasizing again the potential importance of highly infested homes in DENV transmission (Loroño-Pino et al., 2013)
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the potential for ITCs for DENV vector control remain to be determined, especially in the face of emerging insecticide resistance, which could reduce ITC efficacy (see Table A3-4)
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Comment Vacant lots, storm water drains and sewer systems, and other cryptic breeding sites clearly must be included in the efforts to control Ae. aegypti in source reduction and larviciding control programs.
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, which has exploded in Ae. aegypti in Mexico and the Yucatán, a pattern that is being documented throughout the pantropical super nidus.
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Point mutations are designated based on the house fly sodium channel gene (GenBank accession number X96668)
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In An. gambiae, kdr alleles have become fixed and have had limited impact upon vector control; however, there continues to be evolution of metabolic resistance mechanisms in the mosquito, which may increase resistance by 1,000 fold (Hemingway, 2014)
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Identification of one or a few metabolic genes that are predictably asso ciated with permethrin adaptation may very be difficult, but such information would be invaluable for incorporation into mosquito surveillance and control programs. Potential Factors Conditioning the Increase in Knockdown Resistance Public health insecticide usage The selective pressures that produced the observed dramatic increase in Ile1,016 frequencies in Mexico remain a subject of discussion.
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. Such control efforts are much less extensive in rural areas and villages, and the importance of vector control in selection for resistance is likely reflected in the fact that kdr frequencies are significantly less in rural areas surrounding Mérida City, where public health vector control is much less intensive than in Mérida City.
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Clearly, there is a large market and incentive for companies to provide effective consumer products for vector control. The constant exposure to pyrethroid-based insecticides resulting from public health control efforts and the use of consumer products could promote insecticide resistance in the mosquito populations.
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The new insecticides will provide the potential for rotational or mosaic applications to minimize development of insecticide resistance and thereby provide improved stewardship of existing and new pesticides and sustainable vector control. Needs and Opportunities The pantropical urban super nidus for Ae.
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. These strategies are environmentally sensitive and particularly suited to dengue vector control in the super nidus, as in using mosquitoes to find cryptic breeding sites and deliver the control agent.
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PLoS Neglected Tropical Diseases 7(3)
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2009. Proactive vector control strategies and improved monitoring and evaluation practices for dengue preventional strategies and improved monitoring and evaluation practices for dengue prevention.
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2013. Fever versus fever: The role of host and vector susceptibility and interspecific competition in shaping the current and future distributions of the sylvatic cycles of dengue virus and yellow fever virus.
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2009. The neovolcanic axis is a barrier to gene flow among edes A aegypti populations in Mexico that differ in vector competence for dengue 2 virus.
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2006. Dengue prevention and 35 years of vector control in Singapore.
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2009. Gene flow, sub species composition, and dengue virus-2 susceptibility among Aedes aegypti collections in Senegal.
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