bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2021‒03‒07
seventeen papers selected by
Richard Halfpenny
Staffordshire University

  1. PLoS One. 2021 ;16(3): e0248026
      Novel chemistry for vector control is urgently needed to counter insecticide resistance in mosquitoes. Here a new meta-diamide insecticide, broflanilide (TENEBENALTM), was evaluated in East African experimental huts in Moshi, northern Tanzania. Two consecutive experimental hut trials with broflanilide 50WP were conducted; the first evaluating the efficacy of three concentrations, 50 mg/m2, 100 mg/m2, and 200 mg/m2 using a prototype formulation, and the second trial evaluating an improved formulation. The IRS treatments were applied on both mud and concrete surfaces and efficacy was monitored over time. The mortality, blood-feeding inhibition and exiting behaviour of free-flying wild mosquitoes was compared between treatment arms. Additionally, cone assays with pyrethroid-susceptible and resistant mosquito strains were conducted in the huts to determine residual efficacy. The first trial showed a dosage-mortality response of the prototype formulation and 3-8 months of residual activity, with longer activity on concrete than mud. The second trial with an improved formulation showed prolonged residual efficacy of the 100 mg/m2 concentration to 5-6 months on mud, and mosquito mortality on the concrete surface ranged between 94-100% for the full duration of the trial. In both trials, results with free-flying, wild Anopheles arabiensis echoed the mortality trend shown in cone assays, with the highest dose inducing the highest mortality and the improved formulation showing increased mortality rates. No blood-feeding inhibition or insecticide-induced exiting effects were observed with broflanilide. Broflanilide 50WP was effective against both susceptible and pyrethroid-resistant mosquito strains, demonstrating an absence of cross resistance between broflanilide and pyrethroids. The improved formulation, which has now been branded VECTRONTM T500, resulted in a prolonged residual efficacy. These results indicate the potential of this insecticide as an addition to the arsenal of IRS products needed to maintain both control of malaria and resistance management of malaria-transmitting mosquitoes.
  2. Malar J. 2021 Mar 04. 20(1): 127
      BACKGROUND: Implementation and upscale of effective malaria vector control strategies necessitates understanding the multi-factorial aspects of transmission patterns. The primary aims of this study are to determine the vector composition, biting rates, trophic preference, and the overall importance of distinguishing outdoor versus indoor malaria transmission through a study at two communities in rural Mali.METHODS: Mosquito collection was carried out between July 2012 and June 2016 at two rural Mali communities (Dangassa and Koïla Bamanan) using pyrethrum spray-catch and human landing catch approaches at both indoor and outdoor locations. Species of Anopheles gambiae complex were identified by polymerase chain reaction (PCR). Enzyme-Linked -Immuno-Sorbent Assay (ELISA) were used to determine the origin of mosquito blood meals and presence of Plasmodium falciparum sporozoite infections.
    RESULTS: A total of 11,237 An. gambiae sensu lato (s.l.) were collected during the study period (5239 and 5998 from the Dangassa and Koïla Bamanan sites, respectively). Of the 679 identified by PCR in Dangassa, Anopheles coluzzii was the predominant species with 91.4% of the catch followed by An. gambiae (8.0%) and Anopheles arabiensis (0.6%). At the same time in Koïla Bamanan, of the 623 An. gambiae s.l., An. coluzzii accounted for 99% of the catch, An. arabiensis 0.8% and An. gambiae 0.2%. Human Blood Index (HBI) measures were significantly higher in Dangassa (79.4%; 95% Bayesian credible interval (BCI) [77.4, 81.4]) than in Koïla Bamanan (15.9%; 95% BCI [14.7, 17.1]). The human biting rates were higher during the second half of the night at both sites. In Dangassa, the sporozoite rate was comparable between outdoor and indoor mosquito collections. For outdoor collections, the sporozoite positive rate was 3.6% (95% BCI [2.1-4.3]) and indoor collections were 3.1% (95% BCI [2.4-5.0]). In Koïla Bamanan, the sporozoite rate was higher indoors at 4.3% (95% BCI [2.7-6.3]) compared with outdoors at 2.4% (95% BCI [1.1-4.2]). In Dangassa, corrected entomological inoculation rates (cEIRs) using HBI were 13.74 [95% BCI 9.21-19.14] infective bites/person/month (ib/p/m) at indoor, and 18.66 [95% BCI 12.55-25.81] ib/p/m at outdoor. For Koïla Bamanan, cEIRs were 1.57 [95% BCI 2.34-2.72] ib/p/m and 0.94 [95% BCI 0.43-1.64] ib/p/m for indoor and outdoor, respectively. EIRs were significantly higher at the Dangassa site than the Koïla Bamanan site.
    CONCLUSION: The findings in this work may indicate the occurrence of active, outdoor residual malaria transmission is comparable to indoor transmission in some geographic settings. The high outdoor transmission patterns observed here highlight the need for additional strategies to combat outdoor malaria transmission to complement traditional indoor preventive approaches such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) which typically focus on resting mosquitoes.
    Keywords:  An. gambiae complex; Entomological Inoculation Rate (EIR); Human landing catch; Malaria transmission; Outdoor; Pyrethrum spray catch
  3. PLoS One. 2021 ;16(3): e0240771
      BACKGROUND: Long Lasting Insecticidal Nets (LLINs) and indoor residual spraying (IRS) represent powerful tools for controlling malaria vectors in sub-Saharan Africa. The success of these interventions relies on their capability to inhibit indoor feeding and resting of malaria mosquitoes. This study sought to understand the interaction of insecticide resistance with indoor and outdoor resting behavioral responses of malaria vectors from Western Kenya.METHODS: The status of insecticide resistance among indoor and outdoor resting anopheline mosquitoes was compared in Anopheles mosquitoes collected from Kisumu and Bungoma counties in Western Kenya. The level and intensity of resistance were measured using WHO-tube and CDC-bottle bioassays, respectively. The synergist piperonyl butoxide (PBO) was used to determine if metabolic activity (monooxygenase enzymes) explained the resistance observed. The mutations at the voltage-gated sodium channel (Vgsc) gene and Ace 1 gene were characterized using PCR methods. Microplate assays were used to measure levels of detoxification enzymes if present.
    RESULTS: A total of 1094 samples were discriminated within Anopheles gambiae s.l. and 289 within An. funestus s.l. In Kisian (Kisumu county), the dominant species was Anopheles arabiensis 75.2% (391/520) while in Kimaeti (Bungoma county) collections the dominant sibling species was Anopheles gambiae s.s 96.5% (554/574). The An. funestus s.l samples analysed were all An. funestus s.s from both sites. Pyrethroid resistance of An.gambiae s.l F1 progeny was observed in all sites. Lower mortality was observed against deltamethrin for the progeny of indoor resting mosquitoes compared to outdoor resting mosquitoes (Mortality rate: 37% vs 51%, P = 0.044). The intensity assays showed moderate-intensity resistance to deltamethrin in the progeny of mosquitoes collected from indoors and outdoors in both study sites. In Kisian, the frequency of vgsc-L1014S and vgsc-L1014F mutation was 0.14 and 0.19 respectively in indoor resting malaria mosquitoes while those of the outdoor resting mosquitoes were 0.12 and 0.12 respectively. The ace 1 mutation was present in higher frequency in the F1 of mosquitoes resting indoors (0.23) compared to those of mosquitoes resting outdoors (0.12). In Kimaeti, the frequencies of vgsc-L1014S and vgsc-L1014F were 0.75 and 0.05 respectively for the F1 of mosquitoes collected indoors whereas those of outdoor resting ones were 0.67 and 0.03 respectively. The ace 1 G119S mutation was present in progeny of mosquitoes from Kimaeti resting indoors (0.05) whereas it was absent in those resting outdoors. Monooxygenase activity was elevated by 1.83 folds in Kisian and by 1.33 folds in Kimaeti for mosquitoes resting indoors than those resting outdoors respectively.
    CONCLUSION: The study recorded high phenotypic, metabolic and genotypic insecticide resistance in indoor resting populations of malaria vectors compared to their outdoor resting counterparts. The indication of moderate resistance intensity for the indoor resting mosquitoes is alarming as it could have an operational impact on the efficacy of the existing pyrethroid based vector control tools. The use of synergist (PBO) in LLINs may be a better alternative for widespread use in these regions recording high insecticide resistance.
  4. J Arthropod Borne Dis. 2020 Sep;14(3): 270-276
      Background: The incidence and area of arbovirus infections is increasing around the world. It is largely linked to the spread of the main arbovirus vectors, invasive mosquito of the genus Aedes. Previously, it has been reported that Aedes aegypti reemerged in Russia after a 50-year absence. Moreover, in 2011, Ae. albopictus was registered in the city of Sochi (South Russia, Black Sea coast) for the first time. In 2013, Asian Ae. koreicus was found in Sochi for the first time.Methods: Mosquitoes were collected using the following methods: larvae with a dip net, imago on volunteers and using bait traps. The mosquitoes were identified using both morphology and sequencing of the second internal transcribed spacer of the nuclear ribosomal RNA gene cluster.
    Results: In August 2016, Ae. koreicus larvae and imago and a single male of Ae. aegypti were found on the southern coast of the Crimean Peninsula, where they were not registered before. Newly obtained DNA sequences were registered in GenBank with the accession numbers MF072936 and MF072937.
    Conclusion: Detection of invasive mosquito species (Ae. aegypti and Ae. koreicus) implies the possibility of their area expansion. Intensive surveillance is required at the Crimean Peninsula to evaluate the potential for the introduction of vector-borne diseases.
    Keywords:  Aedes aegypti; Aedes koreicus; Arbovirus vectors; DNA; Mosquito monitoring
  5. Trop Med Infect Dis. 2021 Feb 17. pii: 25. [Epub ahead of print]6(1):
      Exotic mosquitoes, especially container-inhabiting species such as Aedes aegypti and Aedes albopictus, pose a risk to Australia as they bring with them potentially significant pest and public health concerns. Notwithstanding the threat to public health and wellbeing, significant economic costs associated with the burden of mosquito control would fall to local authorities. Detection of these mosquitoes at airports and seaports has highlighted pathways of introduction but surveillance programs outside these first ports of entry are not routinely conducted in the majority of Australian cities. To assist local authorities to better prepare response plans for exotic mosquito incursions, an investigation was undertaken to determine the extent of habitats suitable for container-inhabiting mosquitoes in over 300 residential properties adjacent to the Port of Newcastle, Newcastle, NSW. More than 1500 water-holding containers were recorded, most commonly pot plant saucers, roof gutters, and water-holding plants (e.g., bromeliads). There were significantly more containers identified for properties classified as untidy but there was no evidence visible that property characteristics could be used to prioritise property surveys in a strategic eradication response. The results demonstrate that there is potential for local establishment of exotic mosquitoes and that considerable effort would be required to adequately survey these environments for the purpose of surveillance and eradication programs.
    Keywords:  Aedes aegypti; Aedes albopictus; Aedes notoscriptus; exotic mosquito surveillance; urban ecology; water-holding containers
  6. Infect Dis Poverty. 2021 Mar 01. 10(1): 20
      BACKGROUND: Lymphatic filariasis (LF) elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020. Evidence shows a persistent LF transmission despite more than a decade of mass drug administration (MDA). It is advocated that, regular monitoring should be conducted in endemic areas to evaluate the progress towards elimination and detect resurgence of the disease timely. This study was therefore designed to assess the status of Wuchereria bancrofti infection in Culex quinqefasciatus and Anopheles species after six rounds of MDA in Masasi District, South Eastern Tanzania.METHODS: Mosquitoes were collected between June and July 2019 using Center for Diseases Control (CDC) light traps and gravid traps for indoor and outdoor respectively. The collected mosquitoes were morphologically identified into respective species. Dissections and PCR were carried out to detect W. bancrofti infection. Questionnaire survey and checklist were used to assess vector control interventions and household environment respectively. A Poisson regression model was run to determine the effects of household environment on filarial vector density.
    RESULTS: Overall, 12 452 mosquitoes were collected of which 10 545 (84.7%) were filarial vectors. Of these, Anopheles gambiae complex, An. funestus group and Cx. quinquefasciatus accounted for 0.1%, 0.7% and 99.2% respectively. A total of 365 pools of Cx. quinquefasciatus (each with 20 mosquitoes) and 46 individual samples of Anopheles species were analyzed by PCR. For Cx. quinquefasciatus pools, 33 were positive for W. bancrofti, giving an infection rate of 0.5%, while the 46 samples of Anopheles species were all negative. All 1859 dissected mosquitoes analyzed by microscopy were also negative. Households with modern latrines had less mosquitoes than those with pit latrines [odds ratio (OR) = 0.407, P < 0.05]. Houses with unscreened windows had more mosquitoes as compared to those with screened windows (OR = 2.125, P < 0.05). More than 80% of the participants own bednets while 16.5% had no protection.
    CONCLUSIONS: LF low transmission is still ongoing in Masasi District after six rounds of MDA and vector control interventions. The findings also suggest that molecular tools may be essential for xenomonitoring LF transmission during elimination phase.
    Keywords:  Anopheles funestus; Anopheles gambiae; Culex quinquefasciatus; Infection rate; Lymphatic filariasis; Mass drug administration; Wuchereria bancrofti
  7. Lancet. 2021 Feb 27. pii: S0140-6736(21)00250-6. [Epub ahead of print]397(10276): 805-815
      BACKGROUND: New vector control tools are required to sustain the fight against malaria. Lethal house lures, which target mosquitoes as they attempt to enter houses to blood feed, are one approach. Here we evaluated lethal house lures consisting of In2Care (Wageningen, Netherlands) Eave Tubes, which provide point-source insecticide treatments against host-seeking mosquitoes, in combination with house screening, which aims to reduce mosquito entry.METHODS: We did a two-arm, cluster-randomised controlled trial with 40 village-level clusters in central Côte d'Ivoire between Sept 26, 2016, and April 10, 2019. All households received new insecticide-treated nets at universal coverage (one bednet per two people). Suitable households within the clusters assigned to the treatment group were offered screening plus Eave Tubes, with Eave Tubes treated using a 10% wettable powder formulation of the pyrethroid β-cyfluthrin. Because of the nature of the intervention, treatment could not be masked for households and field teams, but all analyses were blinded. The primary endpoint was clinical malaria incidence recorded by active case detection over 2 years in cohorts of children aged 6 months to 10 years. This trial is registered with ISRCTN, ISRCTN18145556.
    FINDINGS: 3022 houses received screening plus Eave Tubes, with an average coverage of 70% across the intervention clusters. 1300 eligible children were recruited for active case detection in the control group and 1260 in the intervention group. During the 2-year follow-up period, malaria case incidence was 2·29 per child-year (95% CI 1·97-2·61) in the control group and 1·43 per child-year (1·21-1·65) in the intervention group (hazard ratio 0·62, 95% CI 0·51-0·76; p<0·0001). Cost-effectiveness simulations suggested that screening plus Eave Tubes has a 74·0% chance of representing a cost-effective intervention, compared with existing healthcare activities in Côte d'Ivoire, and is similarly cost-effective to other core vector control interventions across sub-Saharan Africa. No serious adverse events associated with the intervention were reported during follow-up.
    INTERPRETATION: Screening plus Eave Tubes can provide protection against malaria in addition to the effects of insecticide-treated nets, offering potential for a new, cost-effective strategy to supplement existing vector control tools. Additional trials are needed to confirm these initial results and further optimise Eave Tubes and the lethal house lure concept to facilitate adoption.
    FUNDING: The Bill & Melinda Gates Foundation.
  8. Malar J. 2021 Mar 02. 20(1): 123
      BACKGROUND: Larval source management was historically one of the most effective malaria control methods but is now widely deprioritized in Africa, where insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are preferred. However, in Tanzania, following initial successes in urban Dar-es-Salaam starting early-2000s, the government now encourages larviciding in both rural and urban councils nationwide to complement other efforts; and a biolarvicide production-plant has been established outside the commercial capital. This study investigated key obstacles and opportunities relevant to effective rollout of larviciding for malaria control, with a focus on the meso-endemic region of Morogoro, southern Tanzania.METHODS: Key-informants were interviewed to assess awareness and perceptions regarding larviciding among designated health officials (malaria focal persons, vector surveillance officers and ward health officers) in nine administrative councils (n = 27). Interviewer-administered questionnaires were used to assess awareness and perceptions of community members in selected areas regarding larviciding (n = 490). Thematic content analysis was done and descriptive statistics used to summarize the findings.
    RESULTS: A majority of malaria control officials had participated in larviciding at least once over the previous three years. A majority of community members had neutral perceptions towards positive aspects of larviciding, but overall support for larviciding was high, although several challenges were expressed, notably: (i) insufficient knowledge for identifying relevant aquatic habitats of malaria vectors and applying larvicides, (ii) inadequate monitoring of programme effectiveness, (iii) limited financing, and (iv) lack of personal protective equipment. Although the key-informants reported sensitizing local communities, most community members were still unaware of larviciding and its potential.
    CONCLUSIONS: The larviciding programme was widely supported by both communities and malaria control officials, but there were gaps in technical knowledge, implementation and public engagement. To improve overall impact, it is important to: (i) intensify training efforts, particularly for identifying habitats of important vectors, (ii) adopt standard technical principles for applying larvicides or larval source management, (iii) improve financing for local implementation and (iv) improve public engagement to boost community awareness and participation. These lessons could also be valuable for other malaria endemic areas wishing to deploy larviciding for malaria control or elimination.
    Keywords:  Biolarvicides; Ifakara Health Institute; Larval source management; Larviciding; Malaria control; Malaria elimination; Public perception; Stakeholders; Tanzania
  9. J Am Mosq Control Assoc. 2020 Jun 01. 36(2): 81-88
      Military bases are important areas for mosquito surveillance to maintain active duty combat readiness and protect training exercises. The aim of this study was to assist Camp Gruber National Guard training facility personnel to assess their mosquito community and West Nile virus (WNV) risk using biweekly sampling of 50 sites. Between May and October 2018, 10,259 adult female mosquitoes consisting of 6 genera and 26 species were collected over 662 trap-nights using 2 trap types. The most commonly collected genus was Culex (72.2% of total), followed by Psorophora (13.3%) and Aedes (10.2%). Of note, most of the medically important species were collected in the area containing troop living quarters, including 1 WNV-positive pool of Culex tarsalis. Two specimens of Aedes aegypti were collected around a vehicle storage area. While smaller in land mass size than many other active military bases in Oklahoma, the diversity of species at Camp Gruber was comparable to collections from 4 larger bases in Oklahoma. These data demonstrate the need for regular season-long mosquito monitoring of training bases to protect the health of active duty and reserve military personnel.
    Keywords:   Aedes ; Culex ; National Guard bases; military training sites; surveillance
  10. J Am Mosq Control Assoc. 2020 Dec 01. 36(4): 264-268
      Collections of mosquitoes were conducted as part of the entomological vector surveillance in Quintana Roo State, Mexico, during September 2015. Species collected included Anopheles gabaldoni, An. darlingi, Psorophora columbiae, Culex inflictus, Cx. trifidus, Cx. lactator, and Wyeomyia guatemala s.l. All the specimens were identified by morphological and molecular characters (DNA-barcoding). This is the 1st time these species are reported in the Mexican state of Quintana Roo. This research updates and increases the list of species of mosquitoes in Quintana Roo from 79 to 86.
    Keywords:  Mosquito updates; Quintana Roo; mosquito surveillance; new records
  11. J Am Mosq Control Assoc. 2020 Dec 01. 36(4): 257-260
      The overwintering strategy of the mosquito Culex modestus, an important West Nile virus (WNV) vector in Europe, was explored under field conditions in reedbed (Phragmites australis) ecosystems in early 2019. A total of 30 Cx. modestus females were found in a BG-Sentinel trap placed in a plastic greenhouse as well as in a reference BG-Sentinel trap placed under the open sky, both set up within the reedbeds and inspected every 2-3 days from February 27 to April 10, 2019. Moreover, 186 females of Cx. pipiens, 3 females of Anopheles hyrcanus, and 3 females of Culiseta annulata were trapped in the monitored time span. While all Cx. modestus females tested negative for the presence of WNV and other arboviruses circulating in Central Europe, we confirmed WNV lineage 2 and Ťahyna virus infection in several pools of the collected Cx. pipiens, demonstrating arbovirus overwintering. This pilot study highlights the need for large-scale monitoring activities covering different regions to identify the overwintering strategy of both mosquito-borne viruses and their vectors in Central Europe.
    Keywords:   Anopheles hyrcanus ; Culex modestus ; Culex pipiens ; Culiseta annulata ; arboviruses; overwintering
  12. J Am Mosq Control Assoc. 2020 Dec 01. 36(4): 261-263
      Identifying the array of vectors that play a role in perpetuating West Nile virus (WNV) infection in endemic foci will help in controlling the disease. Aedes japonicus has the potential to be a vector in the wild of at least 3 kinds of encephalitis, including WNV. Aedes japonicus is a nonnative species in the USA that is temperature tolerant and a potential human biter. Detection of WNV in mosquito pools of this field-collected invasive species, combined with their ability to feed on humans, make this mosquito species a possible public health concern. In this study, we collected mosquito abundance data and tested them for WNV-positive mosquito samples from 3 counties in New York State. We found a significant association between the season and land demography and the likelihood of the virus in Ae. japonicus.
    Keywords:   Aedes japonicus ; West Nile virus; invasive mosquito species; vector-borne disease; zoonotic disease
  13. PLoS One. 2021 ;16(3): e0247803
      Lack of tools for detailed, real-time observation of mosquito behavior with high spatio-temporal resolution limits progress towards improved malaria vector control. We deployed a high-resolution entomological lidar to monitor a half-kilometer static transect positioned over rice fields outside a Tanzanian village. A quarter of a million in situ insect observations were classified, and several insect taxa were identified based on their modulation signatures. We observed distinct range distributions of male and female mosquitoes in relation to the village periphery, and spatio-temporal behavioral features, such as swarming. Furthermore, we observed that the spatial distributions of males and females change independently of each other during the day, and were able to estimate the daily dispersal of mosquitoes towards and away from the village. The findings of this study demonstrate how lidar-based monitoring could dramatically improve our understanding of malaria vector ecology and control options.
  14. J Am Mosq Control Assoc. 2020 Jun 01. 36(2): 127-130
      Military forces and the recreational industry rely on the repellent properties of permethrin-treated fabrics and N,N-diethyl-meta-toluamide (deet)-based lotions to provide protection from disease vectors and hematophagous organisms. Concerns regarding efficacy have been raised as pyrethroid resistance becomes more common and recent publications present contradictory conclusions. In this preliminary study, consenting volunteers were exposed to pyrethroid-susceptible and pyrethroid-resistant Aedes aegypti strains while wearing sleeves of untreated or permethrin-treated army uniform fabric as well as with untreated or deet-treated exposed forearms. Deet was nearly 100% effective against both susceptible and resistant strains. However, permethrin treatment provided no significant protection against the resistant Puerto Rico strain relative to untreated control sleeves. These results confirm that pyrethroid-resistant vectors can negate the efficacy of permethrin-treated uniforms. Additional testing with resistant field strains is needed to better understand the risk to service members.
    Keywords:   Aedes aegypti ; permethrin; pyrethroids; resistance; uniforms
  15. MMWR Surveill Summ. 2021 Mar 05. 70(1): 1-15
      PROBLEM/CONDITION: West Nile virus (WNV) is an arthropodborne virus (arbovirus) in the family Flaviviridae and is the leading cause of domestically acquired arboviral disease in the contiguous United States. An estimated 70%-80% of WNV infections are asymptomatic. Symptomatic persons usually develop an acute systemic febrile illness. Less than 1% of infected persons develop neuroinvasive disease, which typically presents as encephalitis, meningitis, or acute flaccid paralysis.REPORTING PERIOD: 2009-2018.
    DESCRIPTION OF SYSTEM: WNV disease is a nationally notifiable condition with standard surveillance case definitions. State health departments report WNV cases to CDC through ArboNET, an electronic passive surveillance system. Variables collected include patient age, sex, race, ethnicity, county and state of residence, date of illness onset, clinical syndrome, hospitalization, and death.
    RESULTS: During 2009-2018, a total of 21,869 confirmed or probable cases of WNV disease, including 12,835 (59%) WNV neuroinvasive disease cases, were reported to CDC from all 50 states, the District of Columbia, and Puerto Rico. A total of 89% of all WNV patients had illness onset during July-September. Neuroinvasive disease incidence and case-fatalities increased with increasing age, with the highest incidence (1.22 cases per 100,000 population) occurring among persons aged ≥70 years. Among neuroinvasive cases, hospitalization rates were >85% in all age groups but were highest among patients aged ≥70 years (98%). The national incidence of WNV neuroinvasive disease peaked in 2012 (0.92 cases per 100,000 population). Although national incidence was relatively stable during 2013-2018 (average annual incidence: 0.44; range: 0.40-0.51), state level incidence varied from year to year. During 2009-2018, the highest average annual incidence of neuroinvasive disease occurred in North Dakota (3.16 cases per 100,000 population), South Dakota (3.06), Nebraska (1.95), and Mississippi (1.17), and the largest number of total cases occurred in California (2,819), Texas (2,043), Illinois (728), and Arizona (632). Six counties located within the four states with the highest case counts accounted for 23% of all neuroinvasive disease cases nationally.
    INTERPRETATION: Despite the recent stability in annual national incidence of neuroinvasive disease, peaks in activity were reported in different years for different regions of the country. Variations in vectors, avian amplifying hosts, human activity, and environmental factors make it difficult to predict future WNV disease incidence and outbreak locations.
    PUBLIC HEALTH ACTION: WNV disease surveillance is important for detecting and monitoring seasonal epidemics and for identifying persons at increased risk for severe disease. Surveillance data can be used to inform prevention and control activities. Health care providers should consider WNV infection in the differential diagnosis of aseptic meningitis and encephalitis, obtain appropriate specimens for testing, and promptly report cases to public health authorities. Public health education programs should focus prevention messaging on older persons, because they are at increased risk for severe neurologic disease and death. In the absence of a human vaccine, WNV disease prevention depends on community-level mosquito control and household and personal protective measures. Understanding the geographic distribution of cases, particularly at the county level, appears to provide the best opportunity for directing finite resources toward effective prevention and control activities. Additional work to further develop and improve predictive models that can foreshadow areas most likely to be impacted in a given year by WNV outbreaks could allow for proactive targeting of interventions and ultimately lowering of WNV disease morbidity and mortality.
  16. J Am Mosq Control Assoc. 2020 Jun 01. 36(2s): 56-60
      Hurricane Katrina devastated the Mississippi Gulf Coast on August 29, 2005, causing an ecological disaster. Mississippi State Department of Health (MSDH) entomologists established a vector control program in affected areas with the following objectives: 1) helping local vector control agencies reestablish services, 2) performing mosquito surveillance, and 3) establishing mosquito larviciding and adulticiding where necessary. The MSDH personnel also helped write Action Request Forms requesting assistance from the Federal Emergency Management Agency (FEMA) for increased ground spraying in the 6 lower counties. Mosquito surveillance was conducted daily for 2 wk after the storm, then weekly for another month. Sanitation lagged, with people using makeshift latrines or simply piles of rubbish for bathrooms. Filth flies contaminated food and food surfaces. Responders lived in tent cities, many allowing filth fly access. Approximately 2 wk after hurricane landfall, due to increasing mosquito numbers, MSDH entomologists requested FEMA for an aerial spraying of insecticide to reduce nuisance mosquito biting in the area. A private vendor made 1 application of naled (Dibrom®) insecticide in the 3 coastal counties, yielding over 90% control in entire counties in 1 night. No complaints or medical or environmental problems from the increased ground spraying and aerial spraying were reported. Overall, important lessons in disaster vector control were learned, including how to work effectively with Centers for Disease Control, FEMA, and the US Public Health Service personnel, how to manage the public relations/educational aspects, and how to avoid or mitigate political interference in the disaster response.
    Keywords:  Disasters; health department; hurricanes; mosquito control; public health response
  17. Pathog Glob Health. 2021 Feb 28. 1-9
      Mayaro virus, which can often go undetected due to its clinical manifestations and intimate alignment with dengue and chikungunya viruses, is one of the most neglected arboviruses. The virus has been found in several outbreaks, where a moderate-to-severe and potentially incapacitating joint disease has been observed. MAYV usually circulates in a sylvan cycle of forest mosquitoes and vertebrates, causing sporadic sylvatic infections to humans, and some outbreaks in sub-urban areas. This study focuses on the demonstration of the possible co-circulation of Mayaro virus with chikungunya virus and Zika virus during the outbreaks that occurred in Trinidad and Tobago in 2014 and 2016, respectively. Acute samples from patients who previously tested negative for chikungunya, dengue, and Zika, and specifically exhibiting joint pain were selected and investigated for the presence of Mayaro virus genome using real-time RT-PCR techniques. Nine persons were shown to be positive for Mayaro virus during the chikungunya outbreak of 2014, while no one during the Zika outbreak in 2016. Five results correspond to persons living in highly urbanized areas across Trinidad. These findings provide evidence that multiple arboviral circulations are possible and could easily go undetected especially during outbreak situations. Our study is the first to demonstrate the possible co-circulation of Mayaro and chikungunya viruses and the occurrence of human cases for both diseases during an outbreak in the Caribbean. A possible change in the pattern of distribution of human cases to more urbanized areas is also discussed.
    Keywords:  Mayaro virus; arboviruses; arthralgias; rt-PCR; trinidad and Tobago