bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2022‒12‒18
eleven papers selected by
Richard Halfpenny
Staffordshire University
  1. Abandoned boats contribute to spread of Aedes and Culex vector mosquitoes in coastal belt, Galle District, Southern Sri Lanka.
  2. High vectorial transmission of malaria in urban and rural settings in the northern, western and eastern regions of Côte d'Ivoire.
  3. New Records of Mosquitoes in Bolivia and Northwestern Argentina.
  4. Anopheles stephensi in Africa: vector control opportunities for cobreeding An. stephensi and Aedes arbovirus vectors.
  5. Natural plant diet impacts phenotypic expression of pyrethroid resistance in Anopheles mosquitoes.
  6. Spatial distribution and insecticide resistance profile of Aedes aegypti and Aedes albopictus in Douala, the most important city of Cameroon.
  7. Ecology of Aedes vittatus (Diptera: Culicidae) in rock pools across agroecosystem in Northern Savanna, Nigeria.
  8. Molecular survey of Zika virus in the animal-human interface in traditional farming.
  9. Suppression of flavivirus transmission from animal hosts to mosquitoes with a mosquito-delivered vaccine.
  10. Dengue Fever Outbreak Investigation in Werder Town, Dollo Zone, Somali Region, Ethiopia.
  11. Impact of malaria control interventions on malaria infection and anaemia in low malaria transmission settings: a cross-sectional population-based study in Sudan.
  1. J Vector Borne Dis. 2022 Jul-Sep;59(3):59(3): 285-292
    Abandoned boats contribute to spread of Aedes and Culex vector mosquitoes in coastal belt, Galle District, Southern Sri Lanka.
    Dinithi Shamalee Dissanayake, Chandana Dammika Wijekoon, Hemantha Wegiriya.
      BACKGROUND & OBJECTIVES: Although, the number of considerable cases of dengue and lymphatic filariasis have been reported from Galle District, Sri Lanka in the past several years, contribution of abandoned boats to spread vector mosquitoes of Aedes and Culex in the coast is not well studied. Our aim was to assess the positive composition of different types of abandoned boats by larval vector mosquitoes to investigate their occurrence and habitat preference, and the monsoonal and co-existence variation of Aedes mosquitoes.METHODS: The 4th instar larvae of Aedes and Culex species from three different abandoned boat types in nine subsampling sites at three municipal areas in Galle District were collected during 2017-2019. In total, 15 sampling rounds were conducted in each site for three years duration as five sample rounds per year. Larval collections and identifications were carried out using standard techniques and identification keys according to WHO guidelines. The occurrence of mosquito larvae was analysed by boat type, locations within area and year. Further, the average infestation variation of Aedes mosquitoes were compared with monsoonal and co-existence changers. Results; Out of the total abandoned boats, majority (51%) were engine boats and, 32.7%, 16.35% were troller boats and canoe boats, respectively. Troller boats were highly infested boat type for vector mosquitoes. Aedes albopictus was the dominant vector in abandoned boats other than recorded Ae. aegypti and Culex quinquefasciatus. Culex quinquefasciatus showed comparatively low infestation percentages. The average infestation of Ae. albopictus showed a consistent pattern with monsoon variation. A competitive rapid invasion of Aedes aegypti was observed with the suppressing Ae. albopictus in abandoned boats after 2018.
    INTERPRETATION & CONCLUSION: Abandoned boats contribute noteworthy to spread of Aedes and Culex vector mosquitoes in coastal belt, Galle District. These study findings would be helpful for researchers and health authorities to design appropriate vector control measures and to mitigate future dengue and filariasis outbreaks.
    Keywords:  Abandoned boats; Galle District; Sri Lanka; vector mosquitoes
    DOI:  https://doi.org/10.4103/0972-9062.353252
  2. J Vector Borne Dis. 2022 Jul-Sep;59(3):59(3): 275-284
    High vectorial transmission of malaria in urban and rural settings in the northern, western and eastern regions of Côte d'Ivoire.
    Akré M Adja, Konan F Assouho, Serge-Brice Assi, Négnorogo Guindo-Coulibaly, Emmanuel Tia, André B Sagna, Dounin D Zoh, Affoué C Moro, Ahoua Yapi.
      BACKGROUND & OBJECTIVES: Malaria remains a public health problem in Côte d'Ivoire. To cope with this issue, the Ministry of Health established strategies through Long-Lasting Insecticidal Nets (LLINs) and artemisinin-based medicines. To better understand the influence of periodic mass distribution of LLINs on malaria transmission, this entomological survey was conducted in three regions of Côte d'Ivoire.METHODS: Mosquitoes were sampled by Human Landing Catches (HLC) in urban and rural settings of Korhogo, Man and Abengourou. Mosquitoes were identified morphologically and by molecular methods. Plasmodium falciparum infection was assessed by ELISA, and the Entomological Inoculation Rates (EIR) were calculated for each species and setting.
    RESULTS: Only An. gambiae s.l. was identified in Korhogo and in Abengourou while An. gambiae s.l. and An. funestus s.l. was reported in Man. An. coluzzii was the most abundant species of the An. gambiae siblings collected in Abengourou, and in Man while An. gambiae was most abundant in Korhogo. In urban settings, malaria vectors showed high aggressiveness (>11 bites per person per night) and the annual EIR was high (83.22-438.44 infectious bites per person per year). In rural settings, malaria vectors showed also high aggressiveness (19-52 b/p/n). The annual EIR is very high (>94 ib/p/yr). However, the weakest EIR was recorded in the northern region with 94.90 ib/p/yr.
    INTERPRETATION & CONCLUSION: This work indicates that malaria transmission remains high and heterogeneous across Côte d'Ivoire, despite repeated mass distribution of LLINs. Also, in Man, malaria transmission is more intense with the involvement of two main vectors. Furthermore, in the village of Korhogo, the EIR remained relatively low.
    Keywords:  Anopheles funestus; Anopheles gambiae; Côte d’; Ivoire; rural; urban
    DOI:  https://doi.org/10.4103/0972-9062.355967
  3. J Am Mosq Control Assoc. 2022 Dec 01. 38(4): 276-279
    New Records of Mosquitoes in Bolivia and Northwestern Argentina.
    Maria J Dantur Juri, Edecio I Villarroel Martínez, Paul L Duque, Marina Stein, Maria Anice Mureb Sallum.
      Two mosquito species, Culex (Culex) hepperi and Culex (Culex) maxi are reported for the first time for Bolivia, in Tarija department. Aedes (Ochlerotatus) stigmaticus and Mansonia (Mansonia) indubitans are the first records in Aniceto Arce province, in Tarija department, southern Bolivia. In addition, Aedes (Protomacleaya) alboapicus and Culex (Phytotelmatomyia) renatoi are reported for the first time in the northwestern region of Argentina. Anopheles (Nyssorrhynchus) nuneztovari s.l. is reported for the first time in Jujuy and Tucumán provinces, and Aedes (Ochlerotatus) raymundi and Anopheles (Anopheles) neomaculipalpus are the first reports in Tucumán province. The 3 species are extending their geographical distribution in these provinces. Data on the collection localities and comments about the medical relevance of some species are also presented.
    Keywords:  Culicidae; South America; distribution; mountainous rainforest
    DOI:  https://doi.org/10.2987/22-7085
  4. Trends Parasitol. 2022 Dec 13. pii: S1471-4922(22)00284-7. [Epub ahead of print]
    Anopheles stephensi in Africa: vector control opportunities for cobreeding An. stephensi and Aedes arbovirus vectors.
    Elizabeth Hemming-Schroeder, Ayman Ahmed.
      Anopheles stephensi is an urban malaria vector native in some Asian countries and recently emerged in Africa as an invasive vector competent in transmitting Plasmodium falciparum and P. vivax. The coexistence of An. stephensi and Aedes arboviral vectors offers an optimal opportunity for successful integrated vector management with limited resources.
    Keywords:  Aedes vectors; Africa; Anopheles stephensi; arboviruses; invasive; malaria
    DOI:  https://doi.org/10.1016/j.pt.2022.11.011
  5. Sci Rep. 2022 Dec 12. 12(1): 21431
    Natural plant diet impacts phenotypic expression of pyrethroid resistance in Anopheles mosquitoes.
    Prisca S L Paré, Domonbabele F D S Hien, Koama Bayili, Rakiswendé S Yerbanga, Anna Cohuet, David Carrasco, Edwige Guissou, Louis-Clément Gouagna, Koudraogo B Yaméogo, Abdoulaye Diabaté, Rickard Ignell, Roch K Dabiré, Thierry Lefèvre, Olivier Gnankiné.
      Success in reducing malaria transmission through vector control is threatened by insecticide resistance in mosquitoes. Although the proximal molecular mechanisms and genetic determinants involved are well documented, little is known about the influence of the environment on mosquito resistance to insecticides. The aim of this study was to assess the effect of plant sugar feeding on the response of Anopheles gambiae sensu lato to insecticides. Adults were fed with one of four treatments, namely a 5% glucose control solution, nectariferous flowers of Barleria lupulina, of Cascabela thevetia and a combination of both B. lupulina + C. thevetia. WHO tube tests were performed with 0.05% and 0.5% deltamethrin, and knockdown rate (KD) and the 24 h mosquito mortality were measured. Plant diet significantly influenced mosquito KD rate at both concentrations of deltamethrin. Following exposure to 0.05% deltamethrin, the B. lupulina diet induced a 2.5 fold-increase in mosquito mortality compared to 5% glucose. Species molecular identification confirmed the predominance of An. gambiae (60% of the samples) over An. coluzzii and An. arabiensis in our study area. The kdr mutation L1014F displayed an allelic frequency of 0.75 and was positively associated with increased phenotypic resistance to deltamethrin. Plant diet, particularly B. lupulina, increased the susceptibility of mosquitoes to insecticides. The finding that B. lupulina-fed control individuals (i.e. not exposed to deltamethrin) also displayed increased 24 h mortality suggests that plant-mediated effects may be driven by a direct effect of plant diet on mosquito survival rather than indirect effects through interference with insecticide-resistance mechanisms. Thus, some plant species may weaken mosquitoes, making them less vigorous and more vulnerable to the insecticide. There is a need for further investigation, using a wider range of plant species and insecticides, in combination with other relevant environmental factors, to better understand the expression and evolution of insecticide resistance.
    DOI:  https://doi.org/10.1038/s41598-022-25681-6
  6. PLoS One. 2022 ;17(12): e0278779
    Spatial distribution and insecticide resistance profile of Aedes aegypti and Aedes albopictus in Douala, the most important city of Cameroon.
    Aurelie P Yougang, Christophe R Keumeni, Theodel A Wilson-Bahun, Armel N Tedjou, Flobert Njiokou, Charles Wondji, Basile Kamgang.
      Prevention and control of Aedes-borne viral diseases such as dengue rely on vector control, including the use of insecticides and reduction of larval sources. However, this is threatened by the emergence of insecticide resistance. This study aimed to update the spatial distribution, the insecticide resistance profile of A. aegypti and A. albopictus and the potential resistant mechanisms implicated in the city of Douala. Immature stages of Aedes were collected in August 2020 in eight neighbourhoods in Douala and reared to adult stages. Adult bioassays, and piperonyl butoxide (PBO) synergist assays were carried out according to World Health Organization recommendations. Expression of some candidate metabolic genes including Cyp9M6F88/87, Cyp9J28a, Cyp9J10 and Cyp9J32 in A. aegypti, and Cyp6P12 in A. albopictus were assessed using qPCR. A. aegypti adults G0 were screened using real time melting curve qPCR analyses to genotype the F1534C, V1016I and V410L Aedes kdr mutations. Overall, A. aegypti is the predominant Aedes species, but analyses revealed that both A. albopictus and A. aegypti coexist in all the prospected neighbourhoods of Douala. High level of resistance was observed to three pyrethroids tested in both Aedes species. In A. aegypti a lower mortality rate was reported to permethrin (5.83%) and a higher mortality rate to deltamethrin (63.74%). Meanwhile, for A. albopictus, lower (6.72%) and higher (84.11%) mortality rates were reported to deltamethrin. Similar analysis with bendiocarb, revealed for A. aegypti a loss of susceptibility. However, in A. albopictus samples, analyses revealed a susceptibility in Logbessou, and confirmed resistance in Kotto (59.78%). A partial recovery of mortality was found to insecticides after pre-exposure to PBO. Cyp6P12 was found significantly overexpressed in A. albopictus permethrin resistant and Cyp9M6F88/87 for A. aegypti deltamethrin resistant. F1534C, V1016I and V410L mutations were detected in A. aegypti from different neighbourhoods and by considering the combination of these three kdr 14 genotypes were found. These findings provide relevant information which should be capitalised in the implementation of arbovirus vector control strategies and insecticide resistance management.
    DOI:  https://doi.org/10.1371/journal.pone.0278779
  7. J Vector Borne Dis. 2022 Jul-Sep;59(3):59(3): 265-274
    Ecology of Aedes vittatus (Diptera: Culicidae) in rock pools across agroecosystem in Northern Savanna, Nigeria.
    Okechukwu A Obi, David A Adebote, Ishaya H Nock, James G Josiah.
      BACKGROUND & OBJECTIVES: This study focuses on modulating dexterity of some ecological variables of Aedes vittatus classically breeding in rocky habitats. The study provides a useful insight into ecological variables that underpin or hinder profuse breeding of Ae. vittatus in rock pools and its probable role in disease transmission.METHODS: HANNA HI98129 pH/EC/TDS/TEMP meter was used in situ while standard protocols were used to determine other hydro-chemical variables. Aedes vittatus larvae were obtained with soup ladle and modified ladle dippers. D-frame net was used to capture macroinvertebrates while plankton net was used to obtain samples of microalgae. Tadpoles and water turtles were collected with fine mesh invertebrate net. Macrophytes were uprooted and identified at the Herbarium Unit, Department of Botany, Ahmadu Bello University, Zaria. The influence of physicochemical variables was correlated with distribution of Ae. vittatus using Principal Component Analysis. Regression and ANOVA were used to test for association between predictor variables and mosquito abundance and for the difference amongst inselbergs.
    RESULTS: Linear larval density of Ae. vittatus in rock pools which tapered across Guinea savanna were obtained from twenty-one sites with average density of 139.6 in Sudan savanna. Guinea savanna had an average larval density of 75.5 with lower subsets of moving average densities compared to Sudan savanna. One hundred and sixty-one aquatic insects belonging to four insect orders cohabited rock pools with Ae. vittatus. Toads and frogs' tadpoles were of Bufonidae and Pyxicephalidae families while water turtles belong to Emydidae. pH, TDS (ppm), EC (μs/cm) and alkalinity (mg/l) differed significantly (p<0.05) with the abundance of Ae. vittatus in rock pools. Temperature, depth, water hardness and total suspended solid had direct influence on the distribution of Ae. vittatus in rock pools across sites. Significant positive correlation exists between aquatic insects and abundance of Ae. vittatus. Hydroperiod length, concentration of nitrate and pH were determinants that leverage profuse breeding of Ae. vittatus and survival of rock pool biota.
    INTERPRETATION & CONCLUSION: Results revealed that the bearing influence of rock pool variables is inevitable for breeding of Ae. vittatus. A well defined measure of efficacy incorporating indigenous communities for sustained vector control on inselbergs will go a long way in decimating population of Ae. vittatus and limit the risk of spread of yellow fever hitherto areas not thriving.
    Keywords:  Aedes vittatus; abundance patterns; biota composition; physicochemical variables; rock pools; yellow fever
    DOI:  https://doi.org/10.4103/0972-9062.342395
  8. Front Vet Sci. 2022 ;9 1057686
    Molecular survey of Zika virus in the animal-human interface in traditional farming.
    Laura Ivone Lopez-Apodaca, Heliot Zarza, Emily Zamudio-Moreno, Daniel Nuñez-Avellaneda, Carlos Marcial Baak-Baak, Guadalupe Del Carmen Reyes-Solis, Torres-Chablé Oswaldo Margarito, Ingris Peláez-Ballestas, David Roiz, Gerardo Suzán, Benjamin Roche, Carlos Ignacio Machain-Williams.
      Backyard animal husbandry is common in rural communities in developing countries and, given the conditions in which it occurs, it can increase the risk of disease transmission, such as arboviruses. To determine the presence of the Zika virus (ZIKV) and abundance of its arthropod vectors we evaluated the socioeconomic implications involved in its transmission in two highly vulnerable Mayan communities in the state of Yucatan that practice backyard farming. An analytical cross-sectional study was carried out throughout 2016 to understand socioeconomic variables and seasonal patterns in mosquito populations. We selected 20 households from each community. Social exclusion indicators were analyzed, human and domestic animals were sampled, and mosquitoes were collected and identified. Four out of eight indicators of social exclusion were higher than the reported national averages. We captured 5,825 mosquitoes from 16 species being Culex quinquefasciatus and Aedes aegypti the most abundant. The presence of chickens and human overcrowding in dwellings were the most significant factors (P = 0.026) associated with the presence of Ae. aegypti. Septic tanks (odds ratio = 6.64) and chickens (odds ratio = 27.41) in backyards were the main risk factors associated with the presence of immature states of Ae. aegypti in both communities. Molecular analysis to detect ZIKV was performed in blood samples from 416 humans, 1,068 backyard animals and 381 mosquito pools. Eighteen humans and 10 pig pools tested positive for ZIKV. Forty-three mosquito pools tested positive for flavivirus. Ten of the 43 pools of positive mosquitoes were sequenced, corresponding 3/10 to ZIKV and 1/10 to Dengue virus type 2. The findings obtained indicate the continuous circulation of Flavivirus (including ZIKV) in backyard environments in vulnerable communities, highlighting the importance of studying their transmission and maintenance in these systems, due that backyard animal husbandry is a common practice in these vulnerable communities with limited access to health services.
    Keywords:  Yucatan (Mexico); Zika virus; arbovirus; backyard animal rearing; flavivirus; human-animal interface; mosquitoes; vulnerable communities
    DOI:  https://doi.org/10.3389/fvets.2022.1057686
  9. Nat Commun. 2022 Dec 16. 13(1): 7780
    Suppression of flavivirus transmission from animal hosts to mosquitoes with a mosquito-delivered vaccine.
    Dan Wen, Limin S Ding, Yanan Zhang, Xiaoye Li, Xing Zhang, Fei Yuan, Tongbiao Zhao, Aihua Zheng.
      Zoonotic viruses circulate in the natural reservoir and sporadically spill over into human populations, resulting in endemics or pandemics. We previously found that the Chaoyang virus (CYV), an insect-specific flavivirus (ISF), is replication-defective in vertebrate cells. Here, we develope a proof-of-concept mosquito-delivered vaccine to control the Zika virus (ZIKV) within inaccessible wildlife hosts using CYV as the vector. The vaccine is constructed by replacing the pre-membrane and envelope (prME) proteins of CYV with those of ZIKV, assigned as CYV-ZIKV. CYV-ZIKV replicates efficiently in Aedes mosquitoes and disseminates to the saliva, with no venereal or transovarial transmission observed. To reduce the risk of CYV-ZIKV leaking into the environment, mosquitoes are X-ray irradiated to ensure 100% infertility, which does not affect the titer of CYV-ZIKV in the saliva. Immunization of mice via CYV-ZIKV-carrying mosquito bites elicites robust and persistent ZIKV-specific immune responses and confers complete protection against ZIKV challenge. Correspondingly, the immunized mice could no longer transmit the challenged ZIKV to naïve mosquitoes. Therefore, immunization with an ISF-vectored vaccine via mosquito bites is feasible to induce herd immunity in wildlife hosts of ZIKV. Our study provides a future avenue for developing a mosquito-delivered vaccine to eliminate zoonotic viruses in the sylvatic cycle.
    DOI:  https://doi.org/10.1038/s41467-022-35407-x
  10. Infect Drug Resist. 2022 ;15 7207-7217
    Dengue Fever Outbreak Investigation in Werder Town, Dollo Zone, Somali Region, Ethiopia.
    Zerihun Mesfin, Ahmed Ali, Abdulnasir Abagero, Zewdu Asefa.
      Background: Dengue fever (DF) is a mosquito-borne disease caused by the dengue virus. DF is endemic to many tropical and subtropical countries around the world. In Ethiopia, DF emerged in 2013 and caused a serious public health problem.Objective: We investigated the outbreak to describe by time, place, person, and to identify risk factors associated with the outbreak in Werder town, Dollo Zone, Somali Region, Ethiopia.
    Methods: Descriptive and case-control studies (1:2 ratio) were conducted. We used the World Health Organization (WHO) case definition to identify cases in Werder town from December 10, 2020, to January 4, 2021. Controls were selected from the same town that did not suffer from DF. Serum samples were tested by reverse transcription polymerase chain reaction (RT-PCR) to detect the dengue virus and to identify serotypes. A structured questionnaire was used to collect socio-demographic, behavioural, and environmental characteristics.
    Results: We identified a total of 57 cases and 114 controls. The overall attack rate was 334.41/100,000 with a zero case fatality rate. Six out of twenty serum samples tested positive for the DEN-3 serotype. In multivariate analysis, not hearing of DF (Adjusted odd ratio (AOR): 2.2, 95% CI: 1.015-4.701), not knowing the mode of transmission (AOR: 2.9, 95% CI: 1.338-6.831), not using long-lasting insecticidal net (LLITN) (AOR: 4.4, 95% CI: 1.592-12.330) and not spraying insecticide (AOR: 3.6, 95% CI: 1.591-8.098) were statistically significant risk factors associated with DF outbreak. However, wearing long sleeves (AOR: 0.435, 95% CI: 0.206-0.918) was a protective factor for the DF outbreak.
    Conclusion: DF outbreak in Werder town has been confirmed. The present study provides evidence-based information regarding the identified risk factors that have contributed to the occurrence of DF outbreaks. We recommended implementing vector control measures and strengthening dengue surveillance systems is strongly advised.
    Keywords:  Werder; case-control study; dengue fever; outbreak; risk factors
    DOI:  https://doi.org/10.2147/IDR.S368562
  11. BMC Infect Dis. 2022 Dec 10. 22(1): 927
    Impact of malaria control interventions on malaria infection and anaemia in low malaria transmission settings: a cross-sectional population-based study in Sudan.
    Khalid Abdelmutalab Elmardi, Ishag Adam, Elfatih Mohamed Malik, Hmooda Toto Kafy, Mogahid Sheikheldien Abdin, Immo Kleinschmidt, Stef Kremers, Jessica Sophia Gubbels.
      BACKGROUND: The past two decades were associated with innovation and strengthening of malaria control interventions, which have been increasingly adopted at large scale. Impact evaluations of these interventions were mostly performed in moderate or high malaria transmission areas. This study aimed to evaluate the use and performance of malaria interventions in low transmission areas on malaria infections and anaemia.METHODS: Data from the 2016 Sudan malaria indicator survey was used. Multi-level logistic regression analysis was used to assess the strength of association between real-life community-level utilization of malaria interventions [diagnosis, artemisinin-based combination therapies (ACTs) and long-lasting insecticidal nets (LLINs)] and the study outcomes: malaria infections and anaemia (both overall and moderate-to-severe anaemia).
    RESULTS: The study analysis involved 26,469 individuals over 242 clusters. Malaria infection rate was 7.6%, overall anaemia prevalence was 47.5% and moderate-to-severe anaemia prevalence was 4.5%. The average community-level utilization was 31.5% for malaria diagnosis, 29.9% for ACTs and 35.7% for LLINs. The odds of malaria infection was significantly reduced by 14% for each 10% increase in the utilization of malaria diagnosis (adjusted odds ratio (aOR) per 10% utilization 0.86, 95% CI 0.78-0.95, p = 0.004). However, the odds of infection was positively associated with the utilization of LLINs at community-level (aOR per 10% utilization 1.20, 95% CI 1.11-1.29, p < 0.001). No association between malaria infection and utilization of ACTs was identified (aOR per 10% utilization 0.97, 95% CI 0.91-1.04, p = 0.413). None of the interventions was associated with overall anaemia nor moderate-to-severe anaemia.
    CONCLUSION: There was strong evidence that utilization of malaria diagnosis at the community level was highly protective against malaria infection. No protective effect was seen for community utilization of ACTs or LLINs. No association was established between any of the interventions and overall anaemia or moderate-to-severe anaemia. This lack of effectiveness could be due to the low utilization of interventions or the low level of malaria transmission in the study area. Identification and response to barriers of access and low utilization of malaria interventions are crucial. It is crucial to ensure that every suspected malaria case is tested in a timely way, notably in low transmission settings.
    Keywords:  Anaemia; Impact of malaria interventions; Low malaria transmission; Malaria control interventions; Malaria infection; Sudan
    DOI:  https://doi.org/10.1186/s12879-022-07926-x
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