BackgroundZIKV is a new addition to the arboviruses circulating in the New World, with more than 1 million cases since its introduction in 2015. A growing number of studies have reported vector competence (VC) of Aedes mosquitoes from several areas of the world for ZIKV transmission. Some studies have used New World mosquitoes from disparate regions and concluded that these have a variable but relatively low competence for the Asian lineage of ZIKV.Methodology/Principal findingsTen Aedes aegypti (L) and three Ae. albopictus (Skuse) collections made in 2016 from throughout Mexico were analyzed for ZIKV (PRVABC59—Asian lineage) VC. Mexican Ae. aegypti had high rates of midgut infection (MIR), dissemination (DIR) and salivary gland infection (SGIR) but low to moderate transmission rates (TR). It is unclear whether this low TR was due to heritable salivary gland escape barriers or to underestimating the amount of virus in saliva due to the loss of virus during filtering and random losses on surfaces when working with small volumes. VC varied among collections, geographic regions and whether the collection was made north or south of the Neovolcanic axis (NVA). The four rates were consistently lower in northeastern Mexico, highest in collections along the Pacific coast and intermediate in the Yucatan. All rates were lowest north of the NVA. It was difficult to assess VC in Ae. albopictus because rates varied depending upon the number of generations in the laboratory.Conclusions/SignificanceMexican Ae. aegypti and Ae. albopictus are competent vectors of ZIKV. There is however large variance in vector competence among geographic sites and regions. At 14 days post infection, TR varied from 8–51% in Ae. aegypti and from 2–26% in Ae. albopictus.
Background Effective Aedes aegypti control is limited, in part, by the difficulty in achieving sufficient intervention coverage. To maximise the effect of vector control, areas with persistently high numbers of Aedes-borne disease cases could be identified and prioritised for preventive interventions. We aimed to identify persistent Aedes-borne disease hotspots in cities across southern Mexico.Methods In this spatial analysis, geocoded cases of dengue, chikungunya, and Zika from nine endemic Mexican cities were aggregated at the census-tract level. We included cities that were located in southern Mexico (the arbovirus endemic region of Mexico), with a high burden of dengue cases (ie, more than 5000 cases reported during a 10-year period), and listed as high priority for the Mexican dengue control and prevention programme. The Getis-Ord Gi*(d) statistic was applied to yearly slices of the dataset to identify spatial hotspots of each disease in each city. We used Kendall's W coefficient to quantify the agreement in the distribution of each virus.
A survey was carried out in 51 households within a suburban area of Merida, Yucatan, Mexico, for 5 consecutive days. Adult collections were performed using Prokopack aspirators (indoors) and human-landing mosquito catches (HLC) outdoors, and larval sites (artificial containers) were revised for larvae collection. A total of 259 Aedes albopictus were collected, 246 from artificial larval sites, 8 by indoor aspiration, and 5 by HLC. This is the first record of Ae. albopictus in Merida, Yucatan, Mexico.
Fitting long-lasting insecticidal nets (LLIN) as screens on doors/windows has a significant impact on indoor-adult Aedes aegypti (L.), with entomological reductions measured in a previous study being significant for up to 2 yr post-installation, even in the presence of pyrethroid-resistant Aedes populations. To better understand the mode of LLIN protection, bioassays were performed to evaluate the effects of field deployment (0, 6, and 12 mo) and damage type (none, central, lateral, and multiple) on LLIN efficacy. Contact bioassays confirmed that LLIN residual activity (median knockdown time, in minutes, or MKDT) decreased significantly over time: 6.95 (95% confidence interval [CI]: 5.32–8.58) to 9.24 (95% CI: 8.69–9.79) MKDT at 0- and 12-mo age, respectively, using a pyrethroid-susceptible Aedes strain. Tunnel tests (exposing human forearm for 40 min as attractant) showed that deployment time affected negatively Aedes passage inhibition from 54.9% (95% CI: 43.5–66.2) at 0 mo to 35.7% (95% CI: 16.3–55.1) at 12 mo and blood-feeding inhibition from 65.2% (95% CI: 54.2–76.2) to 48.9% (95% CI: 26.4–71.3), respectively; both the passage/blood-feeding inhibition increased by a factor of 1.8–2.9 on LLINs with multiple and central damages compared with nets with lateral damage. Mosquito mortality was 74.6% (95% CI: 65.3–83.9) at 0 mo, 72.3% (95% CI: 64.1–80.5) at 6 mo, and 59% (95% CI: 46.7–71.3) at 12 mo. Despite the LLIN physical integrity could be compromised over time, we demonstrate that the remaining chemical effect after field conditions would still contribute to killing/repelling mosquitoes.
The public health importance of the endophilic mosquito Aedes aegypti increased dramatically in the recent decade, because it is the vector of dengue, chikungunya, Zika and yellowfever.Theuseoflong-lastinginsecticidalnets(LLINs)fixedondoorsandwindows, as insecticide-treated screening (ITS), is one innovative approach recently evaluated for AedescontrolinSouthMexico.From2009to2014,cluster-randomisedcontrolled trials were conducted in Acapulco and Merida. Intervention clusters received Aedes-proof houses ('Casas a prueba de Aedes')withITSandwerefollowedupduring2years.Overall, resultsshowedsignificantandsustainedreductionsonindooradultvectordensitiesin thetreatedclusterswithITSafter2years:ca.50%onthepresence(OR≤0.62,P<0.05) andabundance(IRR≤0.58,P<0.05).ITSondoorsandwindowsare'user-friendly'tool, withhighlevelsofacceptance,requiringlittleadditionalworkorbehaviouralchangeby householders.Factorsthatfavouredtheseinterventionswere(a)houseconstruction,(b) highcoverageachievedduetotheexcellentacceptancebythecommunityand(c)collaboration of the vector control services; and only some operational complaints relating to screen fragility and the installation process. ITS is a housing improvement that should be part of the current paradigms for urban vector-borne disease control.infections and reducing the global burden of malaria [8] but also can be effective for lymphaticfilariasis,Japaneseencephalitisandotherarboviruses [9].TheuseofLLINsisconsideredahighlyeffective,safe,affordable,low-tech,long-lastingand simpleinterventionwitheffectsbothattheindividual(i.e.bednetspreventingthevectorfrom blood feeding) and community levels (i.e. by reducing the vector lifespan and population). Dengue -Immunopathology and Control Strategies 94Dengue -Immunopathology and Control Strategies 104
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