bims-mosdis 2021-04-11 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2021‒04‒11
twenty-two papers selected by
Richard Halfpenny
Staffordshire University

Seasonal variations of dengue vector mosquitoes in rural settings of Thiruvarur district in Tamil Nadu, India.
Fighting mosquito bite during a crisis: capabilities of Florida mosquito control districts during the COVID-19 pandemic.
Abundance and Seasonality of Aedes aegypti (Diptera: Culicidae) in Two Suburban Localities of South Mexico, With Implications for Wolbachia (Rickettsiales: Rickettsiaceae)-Carrying Male Releases for Population Suppression.
Transcriptomic, proteomic and ultrastructural studies on salinity-tolerant Aedes aegypti in the context of rising sea levels and arboviral disease epidemiology.
The impact of sublethal permethrin exposure on susceptible and resistant genotypes of the urban disease vector, Aedes aegypti.
Larval habitat diversity and Anopheles mosquito species distribution in different ecological zones in Ghana.
Occurrence of major and potential malaria vector immature stages in different breeding habitats and associated biotic and abiotic characters in the district of Trincomalee Sri Lanka.
Critical Photoperiod and Its Potential to Predict Mosquito Distributions and Control Medically Important Pests.
Imported arboviral infections in New Zealand, 2001 to 2017: a risk factor for local transmission.
First report of N1575Y mutation in Anopheles gambiae in Sierra Leone.
Gametocyte carriage of Plasmodium falciparum (pfs25) and Plasmodium vivax (pvs25) during mass screening and treatment in West Timor, Indonesia: a longitudinal prospective study.
Mosquito Identification From Bulk Samples Using DNA Metabarcoding: a Protocol to Support Mosquito-Borne Disease Surveillance in Canada.
Emergence of the invasive Asian bush mosquito, Aedes (Finlaya) japonicus japonicus, in an urban area, Romania.
Efficacy of interceptor® G2, a long-lasting insecticide mixture net treated with chlorfenapyr and alpha-cypermethrin against Anopheles funestus: experimental hut trials in north-eastern Tanzania.
Species Composition, Parous Rate, and Infection Rate of Anopheles Mosquitoes (Diptera: Culicidae) in Bahir Dar City Administration, Northwest Ethiopia.
New vectors that are early feeders for Plasmodium knowlesi and other simian malaria parasites in Sarawak, Malaysian Borneo.
Preliminary analysis of whether mosquitoes can carry and transmit African swine fever.
Zika virus outbreak in Brazil-Lessons learned and perspectives for a safe and effective vaccine.
Devastating urban flooding and dengue outbreak during the COVID-19 pandemic in Pakistan.
Risk estimation of sexual transmission of Zika virus-United States, 2016-2017.
Rift Valley Fever - a Growing Threat To Humans and Animals.
Mosquito Net Ownership, Utilization, and Preferences among Mobile and Migrant Populations Sleeping in Forests and Farms in Central Vietnam: A Cross-Sectional Study.

J Vector Borne Dis. 2020 Jan-Mar;57(1):57(1): 63-70

Seasonal variations of dengue vector mosquitoes in rural settings of Thiruvarur district in Tamil Nadu, India.

Arpita Shukla, A Rajalakshmi, K Subash, S Jayakumar, N Arul, Pradeep Kumar Srivastava, Alex Eapen, Jayalakshmi Krishnan.

  BACKGROUND & OBJECTIVES: Mosquitoes are vectors of several important vector-borne diseases (VBDs) like malaria, dengue, chikungunya, Japanese encephalitis (JE) and lymphatic filariasis (LF). Globally, these VBDs are of major public health concern including India. The information on vector mosquitoes from Thiruvarur district in Tamil Nadu state remains largely either unknown or undocumented. The present study was, therefore, undertaken to find out the seasonal variation in mosquitoes with special reference to dengue vectors in rural areas of Thiruvarur district, Tamil Nadu, India.METHODS: Surveillance of immature vector mosquitoes was undertaken from March 2018 to February 2019. The emerged adults were identified to find out the composition of mosquito species prevalent in the district. The seasonal variations of the mosquitoes especially dengue vectors were analysed for summer (March-July) spring (August-November) and winter (December-February) seasons in all the blocks of Thiruvarur district.
RESULTS: A total of 4879 mosquitoes emerged from the immature collection and the species identification revealed the prevalence of both vector and non-vector species. Five important mosquito vectors collected were -Aedes albopictus, Ae. aegypti, Culex tritaeniorhynchus, Cx. gelidus, and Cx. quinquefasciatus. Other mosquito species collected were Lutzia fuscana, Anopheles barbirostris, An. subpictus, and Armigeres (Armigeres) subalbatus. During the spring season, the dengue vectors showed high indices of breateau index (BI), ranging from 16 to 120; besides, container index (CI) ranging from14.29 to 68.57 and pupal index (PI) from 53.33 to 295 among the study blocks. The major breeding sites were discarded plastic containers, discarded tyres, open sintex tanks (water storage tanks), cement tanks, discarded fibre box, pleated plastic sheets, tree holes, bamboo cut stumps, coconut spathe, and coconut shells.
INTERPRETATION & CONCLUSION: The immature vector surveillance revealed seasonal variations in the entomological indices of Aedes breeding potential. The high indices observed indicate high Aedes breeding density and, therefore, a higher risk for dengue/chikungunya outbreaks in rural areas of Thiruvarur district. The present finding warrants intensive surveillance and follow up vector control measures to avert outbreaks and prevent vector-borne diseases. Health education and the community participation in awareness camps prior to monsoon and societal commitment will help in strengthening source reduction, anti-larval operations and anti-adult measures to tackle vector-borne diseases especially dengue.

Keywords:  Breeding sites; Thiruvarur district; seasonal variation; vector surveillance; vector-borne diseases

DOI:  https://doi.org/10.4103/0972-9062.308803
BMC Public Health. 2021 Apr 08. 21(1): 687

Fighting mosquito bite during a crisis: capabilities of Florida mosquito control districts during the COVID-19 pandemic.

Imelda K Moise, Lola R Ortiz-Whittingham, Vincent Omachonu, Marah Clark, Rui-De Xue.

  BACKGROUND: The stay-at-home orders imposed in early April 2020 due to the COVID-19 pandemic in various states complicated mosquito control activities across the United States (US), and Florida was no exception. Mosquito control programs are the first line of defense against mosquito-borne pathogens. The purpose of this study was to examine the capabilities of Florida mosquito programs to implement key mosquito measures during the COVID-19 pandemic lockdown.METHODS: Using a self-administered online survey, we examined the capabilities of all Florida mosquito control programs (both state-approved mosquito districts, N = 63; and open programs, N = 27) at a time when the state of Florida was still under heightened awareness of, stay-at-home orders and planning a phase 1 reopening over the COVID-19 pandemic (June to July 2020). The final sample included mosquito control programs structured as the Board of County Commissioners (BOCC) (n = 42), independent tax district (n = 16), municipal (n = 10), and health or emergency department (n = 5). We used descriptive statistics to summarize information about the characteristics of responding programs, their implemented mosquito control and surveillance activities. wWe used bivariate analysis to compare the characteristics of responding programs and the self-reported mosquito measures.
RESULTS: Of the recruited mosquito control programs, 73 completed the survey (81.1% response rate; 73/90). Of these, 57.5% (n = 42) were Board of County Commissioners (BOCC) mosquito control programs, 21.9% (n = 16) were independent tax district programs, 13.7% (n = 10) were municipal mosquito control programs, and only 6.8% (n = 5) were either health or emergency department mosquito control programs. Except for arbovirus surveillance, most programs either fully or partially performed larval (61.8%) and adult (78.9%) surveillance; most programs conducted species-specific control for Aedes aegypti (85.2%, n = 54), Aedes albopictus (87.3%, n = 55), Culex quinquefasciatus (92.1%, n = 58), and Culex nigripalpus (91.9%, n = 57).
CONCLUSIONS: Findings underscore the importance of ongoing mosquito control activities, and suggest that Florida mosquito control programs are vigilant and have significant capability to handle potential mosquito-borne disease threats, but arbovirus surveillance systems (laboratory testing of mosquito pools and testing of human and nonhuman specimens for arboviruses) are needed during pandemics as well.

Keywords:  Aedes; Arbovirus; Culex; Fight the bite; GIS; Staffing; Survey; United states; Zika

DOI:  https://doi.org/10.1186/s12889-021-10724-w
J Med Entomol. 2021 Apr 02. pii: tjab052. [Epub ahead of print]

Abundance and Seasonality of Aedes aegypti (Diptera: Culicidae) in Two Suburban Localities of South Mexico, With Implications for Wolbachia (Rickettsiales: Rickettsiaceae)-Carrying Male Releases for Population Suppression.

Azael Che-Mendoza, Abdiel Martin-Park, Juan Manuel Chávez-Trava, Yamili Contreras-Perera, Hugo Delfín-González, Gabriela González-Olvera, Jorge Leirana-Alcocer, Guillermo Guillermo-May, Daniel Chan-Espinoza, Norma Pavia-Ruz, Rosa Eugenia Méndez-Vales, Alberto Alcocer-Gamboa, Fabian Correa-Morales, Jorge Palacio-Vargas, Dongjing Zhang, Gonzalo Vazquez-Prokopec, Zhiyong Xi, Pablo Manrique-Saide.

  We conducted a baseline characterization of the abundance and seasonality of Aedes aegypti (Linnaeus, 1762)-a vector of dengue, chikungunya, and Zika-in two suburban localities of Yucatan, Mexico, as the first step in the implementation of an integrated vector management (IVM) plan combining 'traditional Aedes control' (source reduction/truck-mounted ultra-low volume [ULV] spraying) and incompatible insect technique/sterile insect technique for population suppression in Yucatan, Mexico. Weekly entomological collections with ovitraps and BG-sentinel traps were performed in 1-ha quadrants of both localities for 1 yr. Three distinct periods/phases were identified, closely associated with precipitation: 1) a phase of low population abundance during the dry season (weekly average of Aedes eggs per ovitrap and adults per BG trap = 15.51 ± 0.71 and 10.07 ± 0.88, respectively); 2) a phase of population growth and greatest abundance of Aedes (49.03 ± 1.48 eggs and 25.69 ± 1.31 adults) during the rainy season; and finally 3) a phase of decline among populations (20.91 ± 0.97 eggs and 3.24 ± 0.21 adults) after the peak of the rainy season. Seasonal abundance and dynamics of Ae. aegypti populations suggest that it is feasible to develop and implement time-specific actions as part of an IVM approach incorporating integrating novel technologies (such as rear-and-release of Wolbachia-infected males) with classic (insecticide-based) approaches implemented routinely for vector control. In agreement with the local vector control program, we propose a pilot IVM strategy structured in a preparation phase, an attack phase with traditional vector control, and a suppression phase with inundative releases, which are described in this paper.

Keywords:   Aedes aegypti ; Wolbachia ; incompatible insect technique; population suppression; sterile insect technique

DOI:  https://doi.org/10.1093/jme/tjab052
BMC Genomics. 2021 Apr 09. 22(1): 253

Transcriptomic, proteomic and ultrastructural studies on salinity-tolerant Aedes aegypti in the context of rising sea levels and arboviral disease epidemiology.

Ranjan Ramasamy, Vaikunthavasan Thiruchenthooran, Tibutius T P Jayadas, Thampoe Eswaramohan, Sharanga Santhirasegaram, Kokila Sivabalakrishnan, Arunasalam Naguleswaran, Marilyne Uzest, Bastien Cayrol, Sebastien N Voisin, Philippe Bulet, Sinnathamby N Surendran.

  BACKGROUND: Aedes aegypti mosquito, the principal global vector of arboviral diseases, lays eggs and undergoes larval and pupal development to become adult mosquitoes in fresh water (FW). It has recently been observed to develop in coastal brackish water (BW) habitats of up to 50% sea water, and such salinity tolerance shown to be an inheritable trait. Genomics of salinity tolerance in Ae. aegypti has not been previously studied, but it is of fundamental biological interest and important for controlling arboviral diseases in the context of rising sea levels increasing coastal ground water salinity.RESULTS: BW- and FW-Ae. aegypti were compared by RNA-seq analysis on the gut, anal papillae and rest of the carcass in fourth instar larvae (L4), proteomics of cuticles shed when L4 metamorphose into pupae, and transmission electron microscopy of cuticles in L4 and adults. Genes for specific cuticle proteins, signalling proteins, moulting hormone-related proteins, membrane transporters, enzymes involved in cuticle metabolism, and cytochrome P450 showed different mRNA levels in BW and FW L4 tissues. The salinity-tolerant Ae. aegypti were also characterized by altered L4 cuticle proteomics and changes in cuticle ultrastructure of L4 and adults.
CONCLUSIONS: The findings provide new information on molecular and ultrastructural changes associated with salinity adaptation in FW mosquitoes. Changes in cuticles of larvae and adults of salinity-tolerant Ae. aegypti are expected to reduce the efficacy of insecticides used for controlling arboviral diseases. Expansion of coastal BW habitats and their neglect for control measures facilitates the spread of salinity-tolerant Ae. aegypti and genes for salinity tolerance. The transmission of arboviral diseases can therefore be amplified in multiple ways by salinity-tolerant Ae. aegypti and requires appropriate mitigating measures. The findings in Ae. aegypti have attendant implications for the development of salinity tolerance in other fresh water mosquito vectors and the diseases they transmit.

Keywords:  Aedes aegypti; Arboviral diseases; Climate change; Coastal salinity; Cuticle proteomics; Cuticle ultrastructure; Insecticide resistance; Rising sea levels; Salinity tolerance; Transcriptomics

DOI:  https://doi.org/10.1186/s12864-021-07564-8
Pest Manag Sci. 2021 Apr 05.

The impact of sublethal permethrin exposure on susceptible and resistant genotypes of the urban disease vector, Aedes aegypti.

Lisa M Rigby, Brian J Johnson, Christopher L Peatey, Nigel W Beebe, Gregor J Devine.

  BACKGROUND: In urban environments, some of the most common control tools used against the mosquito disease vector, Aedes aegypti, are pyrethroid insecticides applied as aerosols, fogs, or residual sprays. Their efficacy is compromised by patchy deployment, aging residues and the evolution and invasion of pyrethroid-resistant mosquitoes. A large proportion of mosquitoes in a given environment will therefore receive sublethal doses of insecticide. The potential impact of this sublethal exposure on the behaviour and biology of Ae. aegypti carrying commonly-reported resistance alleles, is poorly documented.RESULTS: In susceptible insects, sublethal exposure to permethrin resulted in reductions in egg viability (13.9%), blood avidity (16.7%) and male mating success (28.3%). It caused a 70% decrease in the lifespan of exposed susceptible females and a 66% decrease in the insecticide-resistant females from the parental strain. Exposure to the same dose of insecticide in the presence of the isolated kdr genotype resulted in a smaller impact on female longevity (a 58% decrease) but a 26% increase in eggs per female and a 37% increase in male mating success. Sublethal permethrin exposure reduced host location success by 20-30% in all strains.
CONCLUSION: The detrimental effects of exposure on susceptible insects were expected, but resistant insects demonstrated a less predictable range of responses including negative effects on longevity and host location but increases in fecundity and mating competitiveness. Overall, sublethal insecticide exposure is expected to increase the competitiveness of resistant phenotypes, acting as a selection pressure for the evolution of permethrin resistance.

Keywords:  Aedes aegypti; Fitness costs; Knockdown resistance; Mating competition; Permethrin; Sublethal exposure

DOI:  https://doi.org/10.1002/ps.6398
Parasit Vectors. 2021 Apr 07. 14(1): 193

Larval habitat diversity and Anopheles mosquito species distribution in different ecological zones in Ghana.

Isaac A Hinne, Simon K Attah, Benedicta A Mensah, Akua O Forson, Yaw A Afrane.

  BACKGROUND: Understanding the ecology of larval malaria and lymphatic filariasis mosquitoes in a changing environment is important in developing effective control tools or programmes. This study characterized the breeding habitats of Anopheles mosquitoes in rural communities in different ecological zones in Ghana during the dry and rainy seasons.METHODS: The spatio-temporal distribution, species composition, and abundance of larval Anopheles mosquitoes in breeding habitats were studied in five locations in three ecological zones of Ghana. These were Anyakpor (coastal savannah area), Duase (forest area), and Libga, Pagaza, and Kpalsogu (Sahel savannah area). Larvae were collected using standard dippers and were raised in the insectary for identification.
RESULTS: Out of a total of 7984 mosquito larvae collected, 2152 (27.26%) were anophelines and were more abundant in the rainy season (70.82%) than in the dry season (29.18%). The anophelines comprised 2128 (98.88%) An. gambiae s.l., 16 (0.74%) An. rufipes, and 8 (0.37%) An. pharoensis. In the coastal savannah and forest zones, dug-out wells were the most productive habitat during the dry (1.59 larvae/dip and 1.47 larvae/dip) and rainy seasons (11.28 larvae/dip and 2.05 larvae/dip). Swamps and furrows were the most productive habitats in the Sahel savannah zone during the dry (0.25 larvae/dip) and rainy (2.14 larvae/dip) seasons, respectively. Anopheles coluzzii was the most abundant sibling species in all the ecological zones. Anopheles melas and An. arabiensis were encountered only in the coastal savannah and the Sahel savannah areas, respectively. Larval habitat types influenced the presence of larvae as well as larval density (p < 0.001). The land-use type affected the presence of Anopheles larvae (p = 0.001), while vegetation cover influenced larval density (p < 0.05).
CONCLUSION: The most productive habitats were dug-out wells in the coastal savannah and forest zones, and furrows from irrigated canals in the Sahel savannah zone. Anopheles coluzzii was the predominant vector species in all the ecological zones. The abundance of Anopheles breeding habitats and larvae were influenced by anthropogenic activities. Encouraging people whose activities create the larval habitats to become involved in larval source management such as habitat manipulation to stop mosquito breeding will be important for malaria and lymphatic filariasis control.

Keywords:  Anopheles; Ecological zones; Ghana; Larval abundance; Larval habitats

DOI:  https://doi.org/10.1186/s13071-021-04701-w
J Vector Borne Dis. 2020 Jan-Mar;57(1):57(1): 85-95

Occurrence of major and potential malaria vector immature stages in different breeding habitats and associated biotic and abiotic characters in the district of Trincomalee Sri Lanka.

R M T B Ranathunge, D N Kannangara, P A D H N Gunatilaka, W Abeyewickreme, M D Hapugoda.

  BACKGROUND & OBJECTIVES: Understanding the effect of biotic and abiotic factors on the biology and ecology of immature stages of anopheline larvae is very important in controlling malaria vector mosquitoes. Therefore, this study was focused on the monitoring of ecological factors affecting the distribution, dynamics, and density of malaria vector mosquitoes in the District of Trincomalee, Sri Lanka.METHODS: Permanent and temporary breeding habitats were identified and selected from five possible malaria sensitive sites in the district of Trincomalee. Anopheles larvae and macro-invertebrates were collected using standard methods for 16 months (from October 2013 to January 2015) and they were identified microscopically. Eight physico-chemical parameters of the breeding habitats were measured.
RESULTS: Overall, a total of 4815 anopheline larvae belonging to 13 species were collected from 3,12,764 dips from 18 permanent and temporary breeding habitats. The abundance of anopheline larvae showed a significant positive correlation (p <0.05) with physico-chemical parameters in breeding habitats, such as temperature, dissolved oxygen, and turbidity. A total of 35 macro-invertebrate taxa were collected from the anopheline mosquito breeding habitats.
INTERPRETATION & CONCLUSION: This study represents the first systematic update of water quality parameters, macro-invertebrate communities associated with Anopheles mosquito oviposition sites in the District of Trincomalee, Sri Lanka. Rainfall intensity and wind speed are critical meteorological factors for the distribution and abundance of malaria vectors. Knowledge generated on the ecology of Anopheles mosquitoes will help to eliminate malaria vectors in the country.

Keywords:  Macro-invertebrates; Sri Lanka; malaria vectors; physico-chemical parameters

DOI:  https://doi.org/10.4103/0972-9062.308806
J Med Entomol. 2021 Apr 09. pii: tjab049. [Epub ahead of print]

Critical Photoperiod and Its Potential to Predict Mosquito Distributions and Control Medically Important Pests.

Caitlin S Peffers, Laura W Pomeroy, Megan E Meuti.

  Diapause, a period of arrested development that allows mosquitoes to survive inhospitable conditions, is triggered by short daylengths in temperate mosquitoes. Different populations of mosquitoes initiate diapause in response to a specific photoperiod, or daylength, resulting in population-specific differences in annual cycles of abundance. The photoperiod that causes approximately 50% of a population to initiate diapause is known as the critical photoperiod (CPP). The autumn daylength corresponding to the CPP in the field likely marks the day beyond which the photoperiods would trigger and maintain 50% or more diapause incidence in a population, although temperature, diet, and other factors can impact diapause initiation. In the Northern Hemisphere, northern populations of mosquitoes experience lower temperatures earlier in the year and must be triggered into diapause by longer daylengths than southern populations. CPP is genetically based, but also adapts over time responding to the population's environment. Therefore, CPP has been shown to lengthen with increasing latitude and altitude. While the positive correlation between CPP and latitude/altitude has been established in a few mosquito species, including Aedes albopictus (Skuse, Diptera: Culicidae), Aedes triseriatus, Aedes sierrensis, and Wyeomyia smithii (Coquillett, Diptera: Culicidae), we do not know when most other species initiate their seasonal responses. As several of these species transmit important diseases, characterizing the CPP of arthropod vectors could improve existing control by ensuring that surveillance efforts align with the vector's seasonally active period. Additionally, better understanding when mosquitoes and other vectors initiate diapause can reduce the frequency of chemical applications, thereby ameliorating the negative impacts to nontarget insects.

Keywords:  climate change; diapause; invasive species

DOI:  https://doi.org/10.1093/jme/tjab049
Travel Med Infect Dis. 2021 Apr 02. pii: S1477-8939(21)00088-0. [Epub ahead of print] 102047

Imported arboviral infections in New Zealand, 2001 to 2017: a risk factor for local transmission.

Sherif E Ammar, Mary Mclntyre, Michael G Baker, Simon Hales.

  BACKGROUND/AIMS: Over the last decade and following international trends, cases of mosquito-borne arboviral infections, notably dengue fever, chikungunya and Zika, have increased among travellers arriving in New Zealand, but no locally acquired cases have been identified. Imported cases are characterised and examined to identify trends and features that might assist in reducing transmission risk from travellers.METHODS: Information on traveller arrivals, notified cases and risk factors for disease acquisition were obtained from national sources. Trends in importation rates, seasonality are described and relationships of notifications with traveller arrivals were examined with a negative binomial regression model.
RESULTS: There was a significant increase in dengue notifications combined with the emergence of Zika and chikungunya. Most notifications were from arrivals in Auckland from Pacific Islands during summer and early autumn.
CONCLUSION/IMPLICATIONS: Overseas travel from New Zealand, particularly to the Pacific Islands and Southeast Asia, involves a risk of arboviral infection. The repeated introduction of arboviruses to New Zealand also increases the risk of local transmission in a country that has vector capable and vector potential mosquitoes, as well as an increasingly suitable climate for new vectors to establish.

Keywords:  New Zealand; Risk; arboviruses; dengue; notifications; travel

DOI:  https://doi.org/10.1016/j.tmaid.2021.102047
Infect Genet Evol. 2021 Apr 05. pii: S1567-1348(21)00149-0. [Epub ahead of print] 104852

First report of N1575Y mutation in Anopheles gambiae in Sierra Leone.

Jianhai Yin, Frederick Yamba, Canjun Zheng, Samuel Juana Smith, Lili Wang, Hongmei Li, Zhigui Xia, Shuisen Zhou, Ning Xiao.

  The resistance of mosquito vectors to insecticides is one of the biological obstacles in the fight against malaria. Understanding of the status and mechanisms underlying the insecticide resistance in Anopheles gambiae species is necessary for success of vector control efforts. The study aimed to determine the molecular forms of An. gambiae from four districts in Sierra Leone during May and June 2018, and the level of N1575Y mutation. The molecular form identification of adult female An. gambiae mosquitoes reared from larvae were carried out using polymerase chain reaction and sequencing. And the N1575Y mutations were detected using SNaPshot and sequencing. As a result, significant differences were found in the distribution of An. gambiae molecular forms among regions (P < 0.001). And a total of 638 An. gambiae sensu stricto, 106 An. coluzzi, and 4 hybrid individuals were identified. Moreover, the overall N1575Y mutation frequency was 10.2% with no statistical difference among regions (χ2 = 3.009, P = 0.390). In addition, no significant differences in N1575Y mutation frequency were found among different An. gambiae molecular forms (P = 0.383). In conclusion, the N1575Y mutation in An. gambiae populations in Sierra Leone was reported for the first time in the present study. It provides key evidence for the necessity of monitoring vector susceptibility levels to insecticides used in this country.

Keywords:  Anopheles gambiae; Molecular forms; N1575Y mutation; SNaPshot; Sierra Leone

DOI:  https://doi.org/10.1016/j.meegid.2021.104852
Malar J. 2021 Apr 09. 20(1): 177

Gametocyte carriage of Plasmodium falciparum (pfs25) and Plasmodium vivax (pvs25) during mass screening and treatment in West Timor, Indonesia: a longitudinal prospective study.

Ayleen Kosasih, Cristian Koepfli, M Sopiyudin Dahlan, William A Hawley, J Kevin Baird, Ivo Mueller, Neil F Lobo, Inge Sutanto.

  BACKGROUND: A goal of malaria epidemiological interventions is the detection and treatment of parasite reservoirs in endemic areas-an activity that is expected to reduce local transmission. Since the gametocyte is the only transmissible stage from human host to mosquito vector, this study evaluated the pre and post presence of gametocytes during a mass screening and treatment (MST) intervention conducted during 2013 in East Nusa Tenggara, Indonesia.METHODS: RT-qPCR targeting pfs25 and pvs25 transcripts-gametocyte molecular markers for Plasmodium falciparum and Plasmodium vivax, respectively, was performed to detect and quantify gametocytes in blood samples of P. falciparum and P. vivax-infected subjects over the course of the MST study. The presence of both asexual and sexual parasites in microscopic and submicroscopic infections was compared from the start and end of the MST, using proportion tests as well as parametric and non-parametric tests.
RESULTS: Parasite prevalence remained unchanged for P. falciparum (6% = 52/811 versus 7% = 50/740, p = 0.838), and decreased slightly for P. vivax (24% = 192/811 versus 19% = 142/740, p = 0.035) between the MST baseline and endpoint. No significant difference was observed in gametocyte prevalence for either P. falciparum (2% = 19/803 versus 3% = 23/729, p = 0.353, OR = 1.34, 95%CI = 0.69-2.63), or P. vivax (7% = 49/744 versus 5% = 39/704, p = 0.442, OR = 0.83, 95%CI = 0.52-1.31). Even though there was an insignificant difference between the two time points, the majority of parasite positive subjects at the endpoint had been negative at baseline (P. falciparum: 66% = 29/44, P. vivax: 60% = 80/134). This was similarly demonstrated for the transmissible stage-where the majority of gametocyte positive subjects at the endpoint were negative at baseline (P. falciparum: 95% = 20/21, P. vivax: 94% = 30/32). These results were independent of treatment provided during MST activities. No difference was demonstrated in parasite and gametocyte density between both time points either in P. falciparum or P. vivax.
CONCLUSION: In this study area, similar prevalence rates of P. falciparum and P. vivax parasites and gametocytes before and after MST, although in different individuals, points to a negligible impact on the parasite reservoir. Treatment administration based on parasite positivity as implemented in the MST should be reevaluated for the elimination strategy in the community. Trial registration Clinical trials registration NCT01878357. Registered 14 June 2013, https://www.clinicaltrials.gov/ct2/show/NCT01878357.

Keywords:  Gametocyte; Mass screening and treatment; Pfs25; Pvs25

DOI:  https://doi.org/10.1186/s12936-021-03709-y
J Med Entomol. 2021 Apr 02. pii: tjab046. [Epub ahead of print]

Mosquito Identification From Bulk Samples Using DNA Metabarcoding: a Protocol to Support Mosquito-Borne Disease Surveillance in Canada.

S Mechai, G Bilodeau, O Lung, M Roy, R Steeves, N Gagne, D Baird, D R Lapen, A Ludwig, N H Ogden.

  Approximately 80 species of mosquitoes (Diptera: Culicidae) have been documented in Canada. Exotic species such as Aedes albopictus (Skuse) (Diptera: Culicidae) are becoming established. Recently occurring endemic mosquito-borne diseases (MBD) in Canada including West-Nile virus (WNV) and Eastern Equine Encephalitis (EEE) are having significant public health impacts. Here we explore the use of DNA metabarcoding to identify mosquitoes from CDC light-trap collections from two locations in eastern Canada. Two primer pairs (BF2-BR2 and F230) were used to amplify regions of the cytochrome c oxidase subunit I (CO1) gene. High throughput sequencing was conducted using an Illumina MiSeq platform and GenBank-based species identification was applied using a QIIME 1.9 bioinformatics pipeline. From a site in southeastern Ontario, Canada, 26 CDC light trap collections of 72 to >300 individual mosquitoes were used to explore the capacity of DNA metabarcoding to identify and quantify captured mosquitoes. The DNA metabarcoding method identified 33 species overall while 24 species were identified by key. Using replicates from each trap, the dried biomass needed to identify the majority of species was determined to be 76 mg (equivalent to approximately 72 mosquitoes), and at least two replicates from the dried biomass would be needed to reliably detect the majority of species in collections of 144-215 mosquitoes and three replicates would be advised for collections with >215 mosquitoes. This study supports the use of DNA metabarcoding as a mosquito surveillance tool in Canada which can help identify the emergence of new mosquito-borne disease potential threats.

Keywords:  DNA metabarcoding; biodiversity; mosquito; taxonomy; vector-borne disease

DOI:  https://doi.org/10.1093/jme/tjab046
Parasit Vectors. 2021 Apr 07. 14(1): 192

Emergence of the invasive Asian bush mosquito, Aedes (Finlaya) japonicus japonicus, in an urban area, Romania.

Cintia Horváth, Cristina Daniela Cazan, Andrei Daniel Mihalca.

  BACKGROUND: A study conducted at the International Airport of Cluj-Napoca, Romania, with the aim of investigating the presence/absence of invasive Aedes mosquito species resulted in finding Aedes japonicus japonicus (Theobald 1901) eggs in one of the ovitraps placed on site.METHODS: The study was carried out between 30 June and 29 September 2020. On 24 August, 26 eggs were collected and later hatched at the University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca's insectary. On 15 October another adult female Ae. japonicus was caught entering a building in the center of the city, about 7 km from the first sampling spot.
RESULTS: The mosquitoes were identified morphologically and confirmed by molecular analysis, based on the genetic analysis of the mitochondrial gene cytochrome c oxidase subunit 1 (COI).
CONCLUSION: This is the first report of the species in Romania, highlighting the need for surveillance and implemented control methods. However, in Romania to our knowledge only Aedes albopictus has been established; further studies are required to learn about this new invasive species' status in Romania.

Keywords:  Aedes japonicus; Airport; Asian bush mosquito; Invasive species; Surveillance

DOI:  https://doi.org/10.1186/s13071-021-04698-2
Malar J. 2021 Apr 09. 20(1): 180

Efficacy of interceptor® G2, a long-lasting insecticide mixture net treated with chlorfenapyr and alpha-cypermethrin against Anopheles funestus: experimental hut trials in north-eastern Tanzania.

Patrick K Tungu, Elisante Michael, Wema Sudi, William W Kisinza, Mark Rowland.

  BACKGROUND: The effectiveness of long-lasting insecticidal nets (LLIN), the primary method for preventing malaria in Africa, is compromised by evolution and spread of pyrethroid resistance. Further gains require new insecticides with novel modes of action. Chlorfenapyr is a pyrrole insecticide that disrupts mitochrondrial function and confers no cross-resistance to neurotoxic insecticides. Interceptor® G2 LN (IG2) is an insecticide-mixture LLIN, which combines wash-resistant formulations of chlorfenapyr and the pyrethroid alpha-cypermethrin. The objective was to determine IG2 efficacy under controlled household-like conditions for personal protection and control of wild, pyrethroid-resistant Anopheles funestus mosquitoes.METHODS: Experimental hut trials tested IG2 efficacy against two positive controls-a chlorfenapyr-treated net and a standard alpha-cypermethrin LLIN, Interceptor LN (IG1)-consistent with World Health Organization (WHO) evaluation guidelines. Mosquito mortality, blood-feeding inhibition, personal protection, repellency and insecticide-induced exiting were recorded after zero and 20 washing cycles. The trial was repeated and analysed using multivariate and meta-analysis.
RESULTS: In the two trials held in NE Tanzania, An. funestus mortality was 2.27 (risk ratio 95% CI 1.13-4.56) times greater with unwashed Interceptor G2 than with unwashed Interceptor LN (p = 0.012). There was no significant loss in mortality with IG2 between 0 and 20 washes (1.04, 95% CI 0.83-1.30, p = 0.73). Comparison with chlorfenapyr treated net indicated that most mortality was induced by the chlorfenapyr component of IG2 (0.96, CI 0.74-1.23), while comparison with Interceptor LN indicated blood-feeding was inhibited by the pyrethroid component of IG2 (IG2: 0.70, CI 0.44-1.11 vs IG1: 0.61, CI 0.39-0.97). Both insecticide components contributed to exiting from the huts but the contributions were heterogeneous between trials (heterogeneity Q = 36, P = 0.02). WHO susceptibility tests with pyrethroid papers recorded 44% survival in An. funestus.
CONCLUSIONS: The high mortality recorded by IG2 against pyrethroid-resistant An. funestus provides first field evidence of high efficacy against this primary, anthropophilic, malaria vector.

Keywords:  Anopheles funestus; Chlorfenapyr; Experimental huts; Insecticide resistance; Interceptor G2; Long-lasting insecticidal nets; Tanzania

DOI:  https://doi.org/10.1186/s12936-021-03716-z
J Med Entomol. 2021 Apr 03. pii: tjab034. [Epub ahead of print]

Species Composition, Parous Rate, and Infection Rate of Anopheles Mosquitoes (Diptera: Culicidae) in Bahir Dar City Administration, Northwest Ethiopia.

Abel Getaneh, Mulat Yimer, Megbaru Alemu, Zelalem Dejazmach, Michael Alehegn, Banchamlak Tegegne.

  Anopheles mosquitoes are the main vectors of malaria. There is little information on the current entomological aspects of Anopheles mosquitoes in Amhara region of northwestern Ethiopia. Therefore, the aim of this study was to assess the prevailing species composition, parous rate, and infection rate of Anopheles mosquitoes in the Bahir Dar city administration. A community-based cross-sectional study was conducted from January through July 2020. For this, six Centers for Disease Control and Prevention light traps (three traps indoor and three traps outdoor) were used to collect adult female Anopheles mosquitoes. The species were morphologically identified, and the parous and infection rates were determined via dissection of ovaries and salivary gland, respectively. A total of 378 adult female Anopheles mosquitoes comprised of three species (Anopheles d'thali, Anopheles rhodesiensis, and Anopheles gambiae complex) were collected and identified at the study sites. Anopheles rhodesiensis was the predominant species accounting for 90% of all collections at the Zenzelima site, followed by An. gambiae complex (6.5%). In contrast, An. gambiae complex was the predominant species at the Tis Abay site, comprising 94% of captures. The overall parous and infection rates were 35 (62.5%) and 1 (2.9%), respectively.

Keywords:   Anopheles ; infection rate; mosquitoes; parous rate; species composition

DOI:  https://doi.org/10.1093/jme/tjab034
Sci Rep. 2021 Apr 08. 11(1): 7739

New vectors that are early feeders for Plasmodium knowlesi and other simian malaria parasites in Sarawak, Malaysian Borneo.

Joshua Xin De Ang, Khatijah Yaman, Khamisah Abdul Kadir, Asmad Matusop, Balbir Singh.

Plasmodium knowlesi is the main cause of malaria in Sarawak, where studies on vectors of P. knowlesi have been conducted in only two districts. Anopheles balabacensis and An. donaldi were incriminated as vectors in Lawas and An. latens in Kapit. We studied a third location in Sarawak, Betong, where of 2169 mosquitoes collected over 36 days using human-landing catches, 169 (7.8%) were Anopheles spp. PCR and phylogenetic analyses identified P. knowlesi and/or P. cynomolgi, P. fieldi, P. inui, P. coatneyi and possibly novel Plasmodium spp. in salivary glands of An. latens and An. introlatus from the Leucosphyrus Group and in An. collessi and An. roperi from the Umbrosus Group. Phylogenetic analyses of cytochrome oxidase subunit I sequences indicated three P. knowlesi-positive An. introlatus had been misidentified morphologically as An. latens, while An. collessi and An. roperi could not be delineated using the region sequenced. Almost all vectors from the Leucosphyrus Group were biting after 1800 h but those belonging to the Umbrosus Group were also biting between 0700 and 1100 h. Our study incriminated new vectors of knowlesi malaria in Sarawak and underscores the importance of including entomological studies during the daytime to obtain a comprehensive understanding of the transmission dynamics of malaria.

DOI: https://doi.org/10.1038/s41598-021-86107-3
BMC Vet Res. 2021 Apr 09. 17(1): 152

Preliminary analysis of whether mosquitoes can carry and transmit African swine fever.

Weiyun Qin, Zhongcheng Gao, Shenglong Wu, Wenbin Bao.

  BACKGROUND: Mosquitoes are important insect vectors, but whether they can carry and transmit African swine fever virus (ASFV) in large-scale pig farms in China is unknown.RESULTS: In this study, probe-based qPCR analysis was performed on mosquitoes from five pig farms with ASF virus (ASFV). Analysis of ASFV in 463 mosquitoes yielded negative cycle threshold (CT) value), and detection remained negative after mixing samples from all five pig farms.
CONCLUSIONS: Therefore, mosquitoes appear unlikely to transmit ASFV, and pose little threat to large-scale pig farms. Thus, farms should continue to follow normal mosquito control procedures when formulating strategies for the prevention and control of ASF.

Keywords:  African swine fever; Insect vector; Mosquito; Pig farms; Probe‐based qPCR; Virus transmission

DOI:  https://doi.org/10.1186/s12917-021-02865-2
Anat Rec (Hoboken). 2021 Apr 08.

Zika virus outbreak in Brazil-Lessons learned and perspectives for a safe and effective vaccine.

Marco Aurélio Palazzi Sáfadi, Flavia J Almeida, Renato de Ávila Kfouri.

  Zika virus (ZIKV) is an emerging pathogen of public health concern, associated with a dramatic burden in places where the virus caused outbreaks between 2015 and 2017. In the Americas, the ZIKV was first reported in Brazil and rapidly spread through the Americas. Since its first report, a number of studies have been published as we continue to learn, not only about modes of transmission, but also clinical manifestations, risk of congenital anomalies, including microcephaly and neurological malformations in fetuses born from mothers infected during pregnancy. Interventions to reduce the burden of ZIKV infection are restricted to mosquito control, and for Aedes spp mosquitoes the strategies implemented to that end proved to be unsuccessful so far. Hence the lessons we can learn following the ZIKV epidemics become of paramount importance in the development of drug treatments and in search for a vaccine.

Keywords:  Guillain-Barré syndrome; Zika; congenital; congenital Zika syndrome; microcephaly; neurological

DOI:  https://doi.org/10.1002/ar.24622
Med J Islam Repub Iran. 2020 ;34 169

Devastating urban flooding and dengue outbreak during the COVID-19 pandemic in Pakistan.

Muhammad Junaid Tahir, Ahsun Rizwan Siddiqi, Irfan Ullah, Ali Ahmed, Juman Dujaili, Muhammad Saqlain.

  Pakistan has recently been overwhelmed by extreme torrential rains, with its most populous city of Karachi experiencing its worst floods in almost a century. Poor flood control and water disposal facilities have led to an immense risk of another dengue outbreak, with multiple cases being reported recently. The enormous accumulation of stagnant water in urban areas is a major source of mosquito breeding and transmission. Historical data has shown the correlation between the number of dengue cases and average rainfall in the region. The monsoon rains have pounded at a time where health authorities are battling to contain the Coronavirus (COVID-19) pandemic. There is a need to implement centralized dengue control strategies to undertake large scale water drainage, sanitation, and disinfection drives in disaster-stricken areas alongside public health awareness programs to combat the after-effects of this natural calamity.

Keywords:  COVID-19; Dengue; Floods; Pakistan; Rain

DOI:  https://doi.org/10.47176/mjiri.34.169
J Infect Dis. 2021 Apr 02. pii: jiab173. [Epub ahead of print]

Risk estimation of sexual transmission of Zika virus-United States, 2016-2017.

Chelsea G Major, Gabriela Paz-Bailey, Susan L Hills, Dania M Rodriguez, Brad J Biggerstaff, Michael Johansson.

  BACKGROUND: Zika virus (ZIKV) can be transmitted sexually, but the risk of sexual transmission remains unknown. Most evidence of sexual transmission is from partners of infected travelers returning from areas with ZIKV circulation.METHODS: We used data from the U.S. national arboviral disease surveillance system (ArboNET) on travel- and sexually-acquired ZIKV disease cases during 2016-2017 to develop individual-level simulations for estimating risk of male-to-female, male-to-male, and female-to-male sexual transmission of ZIKV via vaginal and/or anal intercourse. We specified parametric distributions to characterize individual-level variability of parameters for ZIKV persistence and sexual behaviors.
RESULTS: Using ZIKV RNA persistence in semen/vaginal fluids to approximate infectiousness duration, male-to-male transmission had the highest estimated probability [1.3% (95% CI: 0.4-6.0) per anal sex act], followed by male-to-female and female-to-male transmission [0.4% (95% CI: 0.3-0.6) per vaginal/anal sex act and 0.1% (95% CI:0-0.8) per vaginal sex act, respectively]. Models using viral isolation in semen vs. RNA detection to approximate infectiousness duration predicted greater risk of sexual transmission.
CONCLUSIONS: While likely insufficient to maintain sustained transmission, the estimated risk of ZIKV transmission through unprotected sex is not trivial and is especially important for pregnant women, as ZIKV infection can cause severe congenital disorders.

Keywords:  Zika; risk estimation; sexual transmission; simulation model

DOI:  https://doi.org/10.1093/infdis/jiab173
J Vet Res. 2021 Mar;65(1): 7-14

Rift Valley Fever - a Growing Threat To Humans and Animals.

Małgorzata Kwaśnik, Wojciech Rożek, Jerzy Rola.

  Rift Valley fever (RVF) is a zoonotic, vector-borne infectious disease of ruminants and camels transmitted mainly by the Aedes and Culex mosquito species. Contact with the blood or organs of infected animals may infect humans. Its etiological factor is the Rift Valley fever virus (RVFV) of the Phlebovirus genus and Bunyaviridae family. Sheep and goats are most susceptible to infection and newborns and young individuals endure the most severe disease course. High abortion rates and infant mortality are typical for RVF; its clinical signs are high fever, lymphadenitis, nasal and ocular secretions and vomiting. Conventional diagnosis is done by the detection of specific IgM or IgG antibodies and RVFV nucleic acids and by virus isolation. Inactivated and live-attenuated vaccines obtained from virulent RVFV isolates are available for livestock. RVF is endemic in sub-Saharan Africa and the Arabian Peninsula, but in the last two decades, it was also reported in other African regions. Seropositive animals were detected in Turkey, Tunisia and Libya. The wide distribution of competent vectors in non-endemic areas coupled with global climate change threaten to spread RVF transboundarily. The EFSA considers the movement of infected animals and vectors to be other plausible pathways of RVF introduction into Europe. A very low risk both of introduction of the virus through an infected animal or vector and of establishment of the virus, and a moderate risk of its transmission through these means was estimated for Poland. The risk of these specific modes of disease introduction into Europe is rated as very low, but surveillance and response capabilities and cooperation with the proximal endemic regions are recommended.

Keywords:  Rift Valley fever virus; haemorrhagic fever; mosquitoes; vector-borne disease

DOI:  https://doi.org/10.2478/jvetres-2021-0009
Am J Trop Med Hyg. 2021 Apr 05. pii: tpmd200711. [Epub ahead of print]

Mosquito Net Ownership, Utilization, and Preferences among Mobile and Migrant Populations Sleeping in Forests and Farms in Central Vietnam: A Cross-Sectional Study.

Sara E Canavati, Gerard C Kelly, Thuan Huu Vo, Long Khanh Tran, Thang Duc Ngo, Duong Thanh Tran, Kimberly A Edgel, Nicholas J Martin.

Strengthening vector control measures among mobile and migrant populations (MMPs) is crucial to malaria elimination, particularly in areas with multidrug-resistant malaria. Although a global priority, providing access and ensuring high coverage of available tools such as long-lasting insecticidal nets (LLINs) among these vulnerable groups remains a significant challenge. We assessed mosquito net ownership, utilization, and preference among individuals who slept in a forest and/or on a farm against those residing only in village "home" settings in a priority malaria elimination area of Vietnam. Proportions of respondents owning bed nets were similar among forest, farm, and home sleeping sites, ranging between 96% and 98%. The proportion of respondents owning hammock nets was higher for the forest group (92%), whereas ownership of hammocks in general was significantly lower for the home group (55%). Most respondents (97%) preferred to bring hammock nets to their remote sleeping site, whereas a smaller proportion (25%) also considered bed nets as an option. Respondent preferences included thick hammock nets with zippers (53%), hammocks with a flip cover (17%), and thin hammock nets with zippers (15%), with none choosing polyethylene (hard) LLINs. Although there is high coverage and access to nets for this high-priority MMP, there was a noted gap between coverage and net use, potentially undermining the effectiveness of net-related interventions that could impact malaria prevention and elimination efforts in Vietnam. The design and material of nets are important factors for user preferences that appear to drive net use.

DOI: https://doi.org/10.4269/ajtmh.20-0711