bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2023‒01‒01
seven papers selected by
Richard Halfpenny
Staffordshire University
  1. Survey of West Nile and Banzi Viruses in Mosquitoes, South Africa, 2011-2018.
  2. Survey of malaria vectors on the Cambodia, Thailand and China-Laos Borders.
  3. Malaria vector feeding, peak biting time and resting place preference behaviors in line with Indoor based intervention tools and its implication: scenario from selected sentinel sites of Ethiopia.
  4. Species of mosquitoes present in Abruzzo and Molise and their possible role as vecto of Usutu and West Nile viruses.
  5. Measures of malaria transmission, infection, and disease in an area bordering two districts with and without sustained indoor residual spraying of insecticide in Uganda.
  6. The malaria transmission in Anhui province China.
  7. Malaria in Angola: recent progress, challenges and future opportunities using parasite demography studies.
  1. Emerg Infect Dis. 2023 Jan;29(1): 164-169
    Survey of West Nile and Banzi Viruses in Mosquitoes, South Africa, 2011-2018.
    Caitlin MacIntyre, Milehna Mara Guarido, Megan Amy Riddin, Todd Johnson, Leo Braack, Maarten Scharama, Erin Gorsich, Antonio Paulo Gouveia Almeida, Marietjie Venter.
      We collected >40,000 mosquitoes from 5 provinces in South Africa during 2011-2018 and screened for zoonotic flaviviruses. We detected West Nile virus in mosquitoes from conservation and periurban sites and potential new mosquito vectors; Banzi virus was rare. Our results suggest flavivirus transmission risks are increasing in South Africa.
    Keywords:  Banzi virus; Culex; Culicidae; South Africa; West Nile virus; disease vectors; flavivirus; vector-borne infections; viruses; zoonoses
    DOI:  https://doi.org/10.3201/eid2901.220036
  2. Malar J. 2022 Dec 30. 21(1): 399
    Survey of malaria vectors on the Cambodia, Thailand and China-Laos Borders.
    Canglin Zhang, Rui Yang, Linbo Wu, Chunhai Luo, Yaming Yang, Yan Deng, Jing Wu, Yan Liu, Hongning Zhou.
      BACKGROUND: Anopheles maculatus, Anopheles minimus and Anopheles dirus are the major vectors of malaria transmission in the Greater Mekong Subregion (GMS). The malaria burden in this region has decreased significantly in recent years as all GMS countries progress towards malaria elimination. It is necessary to investigate the Anopheles diversity and abundance status and assess the Plasmodium infection rates to understand the malaria transmission potential of these vector species in GMS countries to guide the development of up-to-date vector control strategies and interventions.METHODS: A survey of mosquitoes was conducted in Stung Treng, Sainyabuli and Phongsaly Provinces on the Cambodia-Laos, Thailand-Laos and China-Laos borders, respectively. Mosquito collection was done by overnight trapping at sentinel sites in each province. After morphological identification, the 18S rRNA-based nested-PCR was performed to detect malaria parasites in the captured Anopheles mosquitoes.
    RESULTS: A total of 18 965 mosquitoes comprising of 35 species of 2 subgenera (Subgenus Anopheles and Subgenus Cellia) and 4 tribes (Tribes Culicini, Aedini, Armigerini and Mansoniini) were captured. Tribe Culicini accounted for 85.66% of captures, followed by Subgenus Anopheles (8.15%). Anopheles sinensis dominated the Subgenus Anopheles by 99.81%. Plasmodium-infection was found in 25 out of the 1 683 individual or pooled samples of Anopheles. Among the 25 positive samples, 19, 5 and 1 were collected from Loum, Pangkhom and Siem Pang village, respectively. Eight Anopheles species were found infected with Plasmodium, i.e., An. sinensis, Anopheles kochi, Anopheles vagus, An. minimus, Anopheles annularis, Anopheles philippinensis, Anopheles tessellatus and An. dirus. The infection rates of Plasmodium falciparum, Plasmodium vivax and mixture of Plasmodium parasite species were 0.12% (2/1 683), 1.31% (22/1 683) and 0.06% (1/1 683), respectively.
    CONCLUSIONS: Overall, this survey re-confirmed that multiple Anopheles species carry malaria parasites in the international border areas of the GMS countries. Anopheles sinensis dominated the Anopheles collections and as carriers of malaria parasites, therefore may play a significant role in malaria transmission. More extensive investigations of malaria vectors are required to reveal the detailed vector biology, ecology, behaviour, and genetics in GMS regions in order to assist with the planning and implementation of improved malaria control strategies.
    Keywords:  Border; Cambodia; China; Laos; Malaria; Malaria parasite; Mosquito; Nested-PCR; Thailand; Vectors
    DOI:  https://doi.org/10.1186/s12936-022-04418-w
  3. Heliyon. 2022 Dec;8(12): e12178
    Malaria vector feeding, peak biting time and resting place preference behaviors in line with Indoor based intervention tools and its implication: scenario from selected sentinel sites of Ethiopia.
    Alemnesh Hailemariam Bedasso, Abebe Asale Gutto, Abate Waldetensai, Araya Eukubay, Getachew Eticha Bokore, Solomon Kinde, Fekadu Gemechu, Yared Debebe, Mesfin Aklilu, Geremew Tasew, Fekadu Massebo, Abebe Teshome, Tilahun Kebede, Bedri Abdulatif, Achamyelesh Sisay, Hiwot Solomon, Eliningaya J Kweka.
      In Ethiopia, malaria incidence has significantly reduced in the past decade through the combined use of conventional vector control approaches and treatment using antimalarial drugs. However, the sustainability of this achievement is threatened by the shift in biting and resting behaviors and emergence of insecticide resistance by the primary malaria vector. Therefore, continuous monitoring of the behaviour of malaria mosquitoes in different sentinel sites is crucial to design effective prevention and control methods in the local context. Entomological investigations were conducted in three sentinel sites for five consecutive months during the major malaria transmission season. The species composition, population dynamics, biting and resting behaviours of malaria vectors were determined using center for disease control and prevention (CDC) light trap, human landing catch (HLC), pyrethrum spray catch (PSC) and Pitfall shelter collection (PFS). Accordingly, 10 households for CDC, 10 households for PSC, 10 households for PFS and 5 households for HLC from each site were randomly enrolled for mosquito collection. A total of 8,297 anopheline mosquitoes were collected from the three sites, out of which 4,525 (54.5 %) were An. gambiae, s.l. 2,028 (24.4 %) were An. pharoensis, 160 (1.9 %) were An. funestus and the rest 1,584 (19 %) were other anophelines (An. coustani, An. cinerus and An. tenebrosus). No significant variation (P = 0.476) was observed between indoor (25.2/trap-night and outdoor collections (20.1/trap-night). Six hundred seventy six (43.3%) of An. gambiae s.l. (primary vector) were collected between 18:00 and 22:00 h. Biting activity declined between 00:00 and 02:00 h. The national malaria control program should pay close attention to the shifting behavior of vector mosquitoes as the observed outdoor feeding tendency of the vector population could pose challenges to the indoor intervention tools IRS and LLINs.
    Keywords:  An. gambiae; Biting behavior; Ethiopia; Malaria; Resting behavior
    DOI:  https://doi.org/10.1016/j.heliyon.2022.e12178
  4. Vet Ital. 2022 Dec 30.
    Species of mosquitoes present in Abruzzo and Molise and their possible role as vecto of Usutu and West Nile viruses.
    Matteo De Ascentis, Michela Quaglia, Silvio Gerardo D'Alessio, Federica Iapaolo, Federica Pizzurro, Franco Ruggeri, Nicola Rossi, Mauro Blardi, Carla Ippoliti, Daniela Cioci, Ottavio Portanti, Maura Pisciella, Alessio Di Lorenzo, Eugenia Ciarrocchi, Roberta Irelli, Annamaria Conte, Daniela Morelli, Federica Monaco, Giovanni Savini, Maria Goffredo.
      In 2019, entomological survey on mosquitoes was carried out in Abruzzo and Molise regions in central Italy to obtain data on local mosquito fauna. Collection sites were selected based on a previous ecoregion classification of the territory.  From 2019 to 2021 virological surveillance for West Nile virus (WNV) and Usutu virus (USUV) on mosquitoes was carried out in the same regions, selecting ecoregions where virus circulation and vector presence were more likely,  all mosquitoes were collected and identified, and the female mosquitoes were sorted in 3046 pools and tested for the presence of WNV and USUV by Real-time PCR. All pools tested negative for WND, while USUV was detected in 7 pools of Aedes caspius collected in Molise region, 17 pools of Culex pipiens s.l. (2 collected in Molise, 15 in Abruzzo), and 1 pool of Culiseta longiareolata collected in Molise. These results suggests the presence of an USUV enzootic cycle, maintained by Culex pipiens s.l. and Aedes caspius in both Italian regions, as well as providing a useful picture in terms of species presence and abundance for both regions. Ecoregions proved to be a very valuable tool in determining high risk areas for vector borne diseases.
    DOI:  https://doi.org/10.12834/VetIt.3046.20276.1
  5. PLoS One. 2022 ;17(12): e0279464
    Measures of malaria transmission, infection, and disease in an area bordering two districts with and without sustained indoor residual spraying of insecticide in Uganda.
    Joaniter I Nankabirwa, Teun Bousema, Sara Lynn Blanken, John Rek, Emmanuel Arinaitwe, Bryan Greenhouse, Philip J Rosenthal, Moses R Kamya, Sarah G Staedke, Grant Dorsey.
      Tororo District, in Eastern Uganda, experienced a dramatic decline in malaria burden starting in 2014 following the implementation of indoor residual spraying of insecticide (IRS) in the setting of repeated long-lasting insecticide treated nets (LLINs) distribution campaigns. However, in 2020 malaria began to resurge in Tororo following a change in the active ingredient used for IRS. In this study, epidemiological measures of malaria were compared shortly after the resurgence between two parishes in Tororo District (Kayoro and Osukuru) and one contiguous parish in Busia District (Buteba), where IRS has never been implemented. A cohort of 483 residents from 80 randomly selected households were followed from August 2020 to January 2021. Mosquitoes were collected every 2 weeks using CDC light traps in rooms where participants slept; parasitemia and gametoctyemia measured every 4 weeks by microscopy and PCR; and symptomatic malaria measured by passive surveillance. The annual entomological inoculation rate was significantly higher in Buteba (108.2 infective bites/person/year), compared to Osukuru (59.0, p = 0.001) and Kayoro (27.4, p<0.001). Overall, parasite prevalence was 19.5% by microscopy and 50.7% by PCR, with no significant differences between the three parishes. Among infected individuals, gametocyte prevalence by PCR was 45.5% and similar between sites. The incidence of malaria was significantly higher in Osukuru (2.46 episodes PPY) compared to Buteba (1.47, p = 0.005) and Kayoro (1.09, p<0.001). For participants over 15 years of age, the risk of symptomatic malaria if microscopic parasitemia was present was higher in Osukuru (relative risk [RR] = 2.99, p = 0.03) compared to Buteba. These findings highlight the complex relationships between measures of malaria transmission, infection, and disease, and the potential for excess disease burden, possibly due to waning immunity, in areas where vector control interventions begin to fail after a sustained period of highly effective control.
    DOI:  https://doi.org/10.1371/journal.pone.0279464
  6. Infect Dis Model. 2023 Mar;8(1): 1-10
    The malaria transmission in Anhui province China.
    Eric Kamana, Di Bai, Heidi E Brown, Jijun Zhao.
      Plasmodium vivax and Plasmodium falciparum cases have opposite trends in Anhui China in the past decade. Long term and seasonal trends in the transmission rate of P. falciparum in Africa has been well studied, however that of P. vivax transmitted by Anopheles sinensis in China has not been investigated. There is a lot of work on the relationship between P. vivax cases and climatic factors in China, with sometimes contradicting results. However, how climatic factors affect transmission rate of P. vivax in China is unknown. We used Anhui province as an example to analyze the recent transmission dynamics where two types of malaria have been reported with differing etiologies. We examined breakpoints of the P. vivax and P. falciparum malaria long term dynamics in the recent decade. For locally transmitted P. vivax malaria, we analyzed the transmission rate and its seasonality using the combined human and mosquitos SIR-SI model with time-varied mosquito biting rate. We identified the effects of meteorological factors on the seasonality in transmission rate using a GAM model. For the imported P. falciparum malaria, we analyzed the potential reason for the observed increase in cases. The breakpoints of P. vivax and P. falciparum dynamics happened in a same year, 2010. The seasonality in the transmission rate of P. vivax malaria was high (42.4%) and was linearly associated with temperature and nonlinearly with rainfall. The abrupt increase in imported P. falciparum cases after the breakpoint was significantly related to the increased annual Chinese investment in Africa. Under the conditions of the existing vectors of malaria, long-term trends in climatic factors, and increasing trend in migration to/from endemic areas and imported malaria cases, we should be cautious of the possibility of the reestablishment of malaria in regions where it has been eliminated or the establishment of other vector-borne diseases.
    Keywords:  Biting rate; Breakpoint; Climatic factors; Seasonality; Transmission rate
    DOI:  https://doi.org/10.1016/j.idm.2022.11.009
  7. Malar J. 2022 Dec 28. 21(1): 396
    Malaria in Angola: recent progress, challenges and future opportunities using parasite demography studies.
    Wilson Tavares, Joana Morais, José F Martins, Ryan J Scalsky, Thomas C Stabler, Márcia M Medeiros, Filomeno J Fortes, Ana Paula Arez, Joana C Silva.
      Over the past two decades, a considerable expansion of malaria interventions has occurred at the national level in Angola, together with cross-border initiatives and regional efforts in southern Africa. Currently, Angola aims to consolidate malaria control and to accelerate the transition from control to pre-elimination, along with other country members of the Elimination 8 initiative. However, the tremendous heterogeneity in malaria prevalence among Angolan provinces, as well as internal population movements and migration across borders, represent major challenges for the Angolan National Malaria Control Programme. This review aims to contribute to the understanding of factors underlying the complex malaria situation in Angola and to encourage future research studies on transmission dynamics and population structure of Plasmodium falciparum, important areas to complement host epidemiological information and to help reenergize the goal of malaria elimination in the country.
    Keywords:  Angola; Elimination eight regional initiative; Malaria; Plasmodium falciparum
    DOI:  https://doi.org/10.1186/s12936-022-04424-y
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