bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2020‒11‒29
sixteen papers selected by
Richard Halfpenny
Staffordshire University
  1. Identification of main malaria vectors and their insecticide resistance profile in internally displaced and indigenous communities in Eastern Democratic Republic of the Congo (DRC).
  2. Efficacy of extended release formulations of Natular™ (spinosad) against larvae and adults of Anopheles mosquitoes in western Kenya.
  3. Establishment of Aedes (Ochlerotatus) scapularis (Diptera: Culicidae) in Mainland Florida, With Notes on the Ochlerotatus Group in the United States.
  4. Linking mosquito surveillance to dengue fever through Bayesian mechanistic modeling.
  5. Long-lasting microbial larvicides for controlling insecticide resistant and outdoor transmitting vectors: a cost-effective supplement for malaria interventions.
  6. From Plasmodium vivax outbreak to elimination: lessons learnt from a retrospective analysis of data from Guantang.
  7. Insecticide susceptibility of Anopheles gambiae s.l and identification of some resistance mechanisms in Kwilu Province in the Democratic Republic of Congo.
  8. Last-come, best served? Mosquito biting order and Plasmodium transmission.
  9. Proposed Integrated Control of Zoonotic Plasmodium knowlesi in Southeast Asia Using Themes of One Health.
  10. Low temperature tolerance of three Aedes albopictus strains (Diptera: Culicidae) under constant and fluctuating temperature scenarios.
  11. A serological framework to investigate acute primary and post-primary dengue cases reporting across the Philippines.
  12. Seroprevalence, spatial dispersion and factors associated with flavivirus and chikungunha infection in a risk area: a population-based seroprevalence study in Brazil.
  13. Malaria epidemiology and stratification of incidence in the malaria elimination setting in Harari Region, Eastern Ethiopia.
  14. Capacity of National Malaria Control Programmes to implement vector surveillance: a global analysis.
  15. Building resilience to mosquito-borne diseases in the Caribbean.
  16. Description of the ovarian microbiota of Aedes aegypti (L) Rockefeller strain.
  1. Malar J. 2020 Nov 23. 19(1): 425
    Identification of main malaria vectors and their insecticide resistance profile in internally displaced and indigenous communities in Eastern Democratic Republic of the Congo (DRC).
    Jeanine A C M Loonen, Dominic B Dery, Bertin Z Musaka, Janvier B Bandibabone, Teun Bousema, Marit van Lenthe, Biserka Pop-Stefanija, Jean-François Fesselet, Constantianus J M Koenraadt.
      BACKGROUND: Malaria remains a major public health concern in the Democratic Republic of the Congo (DRC) and its control is affected by recurrent conflicts. Médecins Sans Frontières (MSF) initiated several studies to better understand the unprecedented incidence of malaria to effectively target and implement interventions in emergency settings. The current study evaluated the main vector species involved in malaria transmission and their resistance to insecticides, with the aim to propose the most effective tools and strategies for control of local malaria vectors.METHODS: This study was performed in 52 households in Shamwana (Katanga, 2014), 168 households in Baraka (South Kivu, 2015) and 269 households in Kashuga (North Kivu, 2017). Anopheles vectors were collected and subjected to standardized Word Health Organization (WHO) and Center for Disease Control (CDC) insecticide susceptibility bioassays. Mosquito species determination was done using PCR and Plasmodium falciparum infection in mosquitoes was assessed by ELISA targeting circumsporozoite protein.
    RESULTS: Of 3517 Anopheles spp. mosquitoes collected, Anopheles gambiae sensu lato (s.l.) (29.6%) and Anopheles funestus (69.1%) were the main malaria vectors. Plasmodium falciparum infection rates for An. gambiae s.l. were 1.0, 2.1 and 13.9% for Shamwana, Baraka and Kashuga, respectively. Anopheles funestus showed positivity rates of 1.6% in Shamwana and 4.4% in Baraka. No An. funestus were collected in Kashuga. Insecticide susceptibility tests showed resistance development towards pyrethroids in all locations. Exposure to bendiocarb, malathion and pirimiphos-methyl still resulted in high mosquito mortality.
    CONCLUSIONS: This is one of only few studies from these conflict areas in DRC to report insecticide resistance in local malaria vectors. The data suggest that current malaria prevention methods in these populations are only partially effective, and require additional tools and strategies. Importantly, the results triggered MSF to consider the selection of a new insecticide for indoor residual spraying (IRS) and a new long-lasting insecticide-treated net (LLIN). The reinforcement of correct usage of LLINs and the introduction of targeted larviciding were also included as additional vector control tools as a result of the studies.
    Keywords:  Anopheles funestus; Anopheles gambiae; Democratic Republic of the Congo (DRC); Insecticide resistance; Internally displaced people; Malaria; Plasmodium falciparum; Pyrethroids
    DOI:  https://doi.org/10.1186/s12936-020-03497-x
  2. Malar J. 2020 Nov 26. 19(1): 436
    Efficacy of extended release formulations of Natular™ (spinosad) against larvae and adults of Anopheles mosquitoes in western Kenya.
    John E Gimnig, Maurice Ombok, Nabie Bayoh, Derrick Mathias, Eric Ochomo, William Jany, Edward D Walker.
      BACKGROUND: Larval source management is recommended as a supplementary vector control measure for the prevention of malaria. Among the concerns related to larviciding is the feasibility of implementation in tropical areas with large numbers of habitats and the need for frequent application. Formulated products of spinosad that are designed to be effective for several weeks may mitigate some of these concerns.METHODS: In a semi-field study, three formulations of spinosad (emulsifiable concentrate, extended release granules and tablet formulations) were tested in naturalistic habitats in comparison to an untreated control. Cohorts of third instar Anopheles gambiae (Diptera: Culicidae) were introduced into the habitats in screened cages every week up to four weeks after application and monitored for survivorship over three days. A small-scale field trial was then conducted in two villages. Two of the spinosad formulations were applied in one village over the course of 18 months. Immature mosquito populations were monitored with standard dippers in sentinel sites and adult populations were monitored by pyrethrum spray catches.
    RESULTS: In the semi-field study, the efficacy of the emulsifiable concentrate of spinosad waned 1 week after treatment. Mortality in habitats treated with the extended release granular formulation of spinosad was initially high but declined gradually over 4 weeks while mortality in habitats treated with the dispersable tablet formulation was low immediately after treatment but rose to 100% through four weeks. In the field study, immature and adult Anopheles mosquito populations were significantly lower in the intervention village compared to the control village during the larviciding period. Numbers of collected mosquitoes were lower in the intervention village compared to the control village during the post-intervention period but the difference was not statistically significant.
    CONCLUSIONS: The extended release granular formulation and the dispersible tablet formulations of spinosad are effective against larval Anopheles mosquitoes for up to four weeks and may be an effective tool as part of larval source management programmes for reducing adult mosquito density and malaria transmission.
    Keywords:  Larval source management; Malaria; Mosquitoes; Spinosad
    DOI:  https://doi.org/10.1186/s12936-020-03507-y
  3. J Med Entomol. 2020 Nov 23. pii: tjaa250. [Epub ahead of print]
    Establishment of Aedes (Ochlerotatus) scapularis (Diptera: Culicidae) in Mainland Florida, With Notes on the Ochlerotatus Group in the United States.
    Lawrence E Reeves, Johana Medina, Evaristo Miqueli, Kristin E Sloyer, William Petrie, Chalmers Vasquez, Nathan D Burkett-Cadena.
      Aedes scapularis (Rondani), a widespread neotropical vector mosquito species, has been included in the mosquito fauna of Florida on the basis of just three larval specimens that were collected in the middle Florida Keys in 1945. Here, we report numerous recent collections of immature and adult Ae. scapularis from multiple locations in two counties of southern Florida. These specimens represent the first records of Ae. scapularis from mainland Florida and the first records of the species in the state since the initial detection of the species 75 yr ago. Collections of both larvae and adults across several years indicate that Ae. scapularis is now established in Broward and Miami-Dade Counties. These contemporary records of this species in Florida may represent novel dispersal and subsequent establishment events from populations outside the United States or a recent reemergence of undetected endemic populations. To confirm morphological identification of Ae. scapularis specimens from Florida, the DNA barcoding region of the cytochrome c oxidase subunit I gene (COI) was sequenced and compared to all other Ochlerotatus Group species from the United States, specifically Aedes condolescens Dyar and Knab (Diptera: Culicidae), Aedes infirmatus Dyar and Knab (Diptera: Culicidae), Aedes thelcter Dyar (Diptera: Culicidae), Aedes tortilis (Theobald) (Diptera: Culicidae), and Aedes trivittatus (Coquillett) (Diptera: Culicidae). Molecular assays and sequencing confirm morphological identification of Ae. scapularis specimens. Maximum likelihood phylogenetic analysis of COI and ITS2 sequences place Florida Ae. scapularis in a distinct clade, but was unable to produce distinct clades for Florida specimens of Ae. condolescens and Ae. tortilis.
    Keywords:  DNA barcoding; invasive species; mosquito; vector
    DOI:  https://doi.org/10.1093/jme/tjaa250
  4. PLoS Negl Trop Dis. 2020 Nov 23. 14(11): e0008868
    Linking mosquito surveillance to dengue fever through Bayesian mechanistic modeling.
    Clinton B Leach, Jennifer A Hoeting, Kim M Pepin, Alvaro E Eiras, Mevin B Hooten, Colleen T Webb.
      Our ability to effectively prevent the transmission of the dengue virus through targeted control of its vector, Aedes aegypti, depends critically on our understanding of the link between mosquito abundance and human disease risk. Mosquito and clinical surveillance data are widely collected, but linking them requires a modeling framework that accounts for the complex non-linear mechanisms involved in transmission. Most critical are the bottleneck in transmission imposed by mosquito lifespan relative to the virus' extrinsic incubation period, and the dynamics of human immunity. We developed a differential equation model of dengue transmission and embedded it in a Bayesian hierarchical framework that allowed us to estimate latent time series of mosquito demographic rates from mosquito trap counts and dengue case reports from the city of Vitória, Brazil. We used the fitted model to explore how the timing of a pulse of adult mosquito control influences its effect on the human disease burden in the following year. We found that control was generally more effective when implemented in periods of relatively low mosquito mortality (when mosquito abundance was also generally low). In particular, control implemented in early September (week 34 of the year) produced the largest reduction in predicted human case reports over the following year. This highlights the potential long-term utility of broad, off-peak-season mosquito control in addition to existing, locally targeted within-season efforts. Further, uncertainty in the effectiveness of control interventions was driven largely by posterior variation in the average mosquito mortality rate (closely tied to total mosquito abundance) with lower mosquito mortality generating systems more vulnerable to control. Broadly, these correlations suggest that mosquito control is most effective in situations in which transmission is already limited by mosquito abundance.
    DOI:  https://doi.org/10.1371/journal.pntd.0008868
  5. Infect Dis Poverty. 2020 Nov 26. 9(1): 162
    Long-lasting microbial larvicides for controlling insecticide resistant and outdoor transmitting vectors: a cost-effective supplement for malaria interventions.
    Guofa Zhou, Eugenia Lo, Andrew K Githeko, Yaw A Afrane, Guiyun Yan.
      The issues of pyrethroid resistance and outdoor malaria parasite transmission have prompted the WHO to call for the development and adoption of viable alternative vector control methods. Larval source management is one of the core malaria vector interventions recommended by the Ministry of Health in many African countries, but it is rarely implemented due to concerns on its cost-effectiveness. New long-lasting microbial larvicide can be a promising cost-effective supplement to current vector control and elimination methods because microbial larvicide uses killing mechanisms different from pyrethroids and other chemical insecticides. It has been shown to be effective in reducing the overall vector abundance and thus both indoor and outdoor transmission. In our opinion, the long-lasting formulation can potentially reduce the cost of larvicide field application, and should be evaluated for its cost-effectiveness, resistance development, and impact on non-target organisms when integrating with other malaria vector control measures. In this opinion, we highlight that long-lasting microbial larvicide can be a potential cost-effective product that complements current front-line long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) programs for malaria control and elimination. Microbial larviciding targets immature mosquitoes, reduces both indoor and outdoor transmission and is not affected by vector resistance to synthetic insecticides. This control method is a shift from the conventional LLINs and IRS programs that mainly target indoor-biting and resting adult mosquitoes.
    Keywords:  Cost-effectiveness; Long-lasting microbial larvicide; Malaria control and elimination; Supplemental tool
    DOI:  https://doi.org/10.1186/s40249-020-00767-3
  6. Malar J. 2020 Nov 23. 19(1): 427
    From Plasmodium vivax outbreak to elimination: lessons learnt from a retrospective analysis of data from Guantang.
    Guo-Jing Yang, Ying Liu, Le-Yuan Shang, Hong-Wei Zhang, Xiao-Nong Zhou, Melissa A Penny, Thomas A Smith.
      BACKGROUND: Malaria was once a serious public health problem in China, with Plasmodium vivax the major species responsible for more than 90% of local transmission. Following significant integrated malaria control and elimination programmes, malaria burden declined, and since 2017 China has not recorded any indigenous case. To understand the historical malaria transmission patterns and epidemic characteristics in China and insights useful to guide P. vivax malaria control and elimination elsewhere, a retrospective study was carried out.METHODS: Historical data from a pilot study conducted in Guantang, Luyi in central China from 1971-1995, were digitized. The data included monthly numbers of reported cases, febrile cases, parasite carriage rates, the neonatal infection rate, and entomological data regarding Anopheles sinensis.
    RESULTS: Following 25 years of continuous integrated malaria control activities, malaria incidence in Guantang decreased from 4,333 cases per 10,000 in 1970 before integrated implementation to 0.23 cases per 10,000 in 1991, and no cases in 1992-1995. Some fluctuations in incidence were observed between 1977 and 1981. During the period parasite rates, antibody levels and the neonatal infection rate also decreased. The pattern of seasonality confirmed that P. vivax in Henan Province was primarily of the long incubation type (temperate) during non-transmission period. The findings retrospectively provide a scientific basis for the implementation of mass campaigns of liver stage hypnozoite clearance. Entomological studies indicated that An. sinensis was the only vector, and it preferred bovine to human hosts, predominantly biting and resting outdoors. Mosquito densities declined between 1971 and 1984.
    CONCLUSION: The integrated malaria control approach in Guantang effectively controlled malaria and achieved elimination. Analysis of the effectiveness of the programme can provide guidance to other regions or countries with similar ecological settings aiming to move from malaria control to elimination. There is a potential challenge in the maintenance of non-transmission status owing to imported cases and the long dormancy of liver stage hypnozoites.
    Keywords:  Central China; Elimination; Pattern; Plasmodium vivax
    DOI:  https://doi.org/10.1186/s12936-020-03501-4
  7. Pan Afr Med J. 2020 ;37 79
    Insecticide susceptibility of Anopheles gambiae s.l and identification of some resistance mechanisms in Kwilu Province in the Democratic Republic of Congo.
    Emery Metelo Matubi, Gillon Ilombe Kaounga, Josue Zanga, Guillaume Binene Mbuku, Jean Nguya Kalemba Maniania, Basimike Mulenda, Jonas Nagahuedi Mbongu Sodi, Jean Jacques Muyembe Tamfum, Paul Masiangi.
      Introduction: the control of the mosquito malaria vectors by the National Malaria Control Programme of the Democratic Republic of Congo (DRC) relies mainly on the use of long-lasting insecticide-treated nets (LLINs). However, the widespread emergence of resistance to pyrethroids is jeopardizing this control strategy. The objective of this study is to determine the status and resistance mechanisms involved in Anopheles gambiae s.l. population of DRC.Methods: pre-imaginal stages of An. gambiae s.l. were collected and standard WHO bioassays were performed on adult An. gambiae s.l. reared in the laboratory from larvae collected from different sites in the study area. The bioassays with the synergist PBO were also performed to determine the likely implication of oxydases in the resistance. The alleles of knock down resistance (Kdr) gene and species of anopheles were determined by PCR-RLFP.
    Results: all Anopheles mosquitoes tested belonged to the Anopheles gambiae complex. An. Gambiae (69.6%) was predominant, followed by An. Coluzzii (25.6%) and (4.8%) hybrids (An. gambiae/ An. coluzzii). Bioassays showed phenotypic resistance to the main insecticides used in the region, notably pyrethroids (deltamethrin, permethrin) and organochlorine (DDT). Only bendiocarb caused 100% mortality. Metabolic resistance involving oxidase enzymes was also detected using the synergist PBO after exposure to deltamethrin. The L1014F allele frequency of Kdr gene was detected in samples collected from all sites at varying frequencies (0.61-1.0).
    Conclusion: this study brings additional information on malaria vectors resistance to insecticides. It has shown cross-resistance to DDT and pyrethroids as well as the presence of Kdr gene. PBO significantly improved the effectiveness of deltamethrin. The results of this study can be helpful to policy makers in decision making for vector control programmes in the region.
    Keywords:  Anopheles gambiae; Democratic Republic of the Congo; Kwilu; insecticide resistance
    DOI:  https://doi.org/10.11604/pamj.2020.37.79.18635
  8. Proc Biol Sci. 2020 Nov 25. 287(1939): 20202615
    Last-come, best served? Mosquito biting order and Plasmodium transmission.
    J Isaïa, A Rivero, O Glaizot, P Christe, R Pigeault.
      A pervasive characteristic of parasite infections is their tendency to be overdispersed. Understanding the mechanisms underlying this overdispersed distribution is of key importance as it may impact the transmission dynamics of the pathogen. Although multiple factors ranging from environmental stochasticity to inter-individual heterogeneity may explain parasite overdispersion, parasite infection is also overdispersed in an inbred host population maintained under laboratory conditions, suggesting that other mechanisms are at play. Here, we show that the aggregated distribution of malaria parasites within mosquito vectors is partially explained by a temporal heterogeneity in parasite infectivity triggered by the bites of mosquitoes. Parasite transmission tripled between the mosquito's first and last blood feed in a period of only 3 h. Surprisingly, the increase in transmission is not associated with an increase in parasite investment in production of the transmissible stage. Overall, we highlight that Plasmodium is capable of responding to the bites of mosquitoes to increase its own transmission at a much faster pace than initially thought and that this is partly responsible for overdispersed distribution of infection. We discuss the underlying mechanisms as well as the broader implications of this plastic response for the epidemiology of malaria.
    Keywords:  Plasmodium; avian malaria; overdispersion; temporal heterogeneity; transmission
    DOI:  https://doi.org/10.1098/rspb.2020.2615
  9. Trop Med Infect Dis. 2020 Nov 20. pii: E175. [Epub ahead of print]5(4):
    Proposed Integrated Control of Zoonotic Plasmodium knowlesi in Southeast Asia Using Themes of One Health.
    Jessica Scott.
      Zoonotic malaria, Plasmodium knowlesi, threatens the global progression of malaria elimination. Southeast Asian regions are fronting increased zoonotic malaria rates despite the control measures currently implemented-conventional measures to control human-malaria neglect P. knowlesi's residual transmission between the natural macaque host and vector. Initiatives to control P. knowlesi should adopt themes of the One Health approach, which details that the management of an infectious disease agent should be scrutinized at the human-animal-ecosystem interface. This review describes factors that have conceivably permitted the emergence and increased transmission rates of P. knowlesi to humans, from the understanding of genetic exchange events between subpopulations of P. knowlesi to the downstream effects of environmental disruption and simian and vector behavioral adaptations. These factors are considered to advise an integrative control strategy that aligns with the One Health approach. It is proposed that surveillance systems address the geographical distribution and transmission clusters of P. knowlesi and enforce ecological regulations that limit forest conversion and promote ecosystem regeneration. Furthermore, combining individual protective measures, mosquito-based feeding trapping tools and biocontrol strategies in synergy with current control methods may reduce mosquito population density or transmission capacity.
    Keywords:  Integrated vector management; One Health; Zoonotic diseases; vector-borne disease
    DOI:  https://doi.org/10.3390/tropicalmed5040175
  10. Parasit Vectors. 2020 Nov 23. 13(1): 587
    Low temperature tolerance of three Aedes albopictus strains (Diptera: Culicidae) under constant and fluctuating temperature scenarios.
    Lisa Tippelt, Doreen Werner, Helge Kampen.
      BACKGROUND: Aedes albopictus, a vector of numerous viruses and filarial worms, has already established in 20 countries in Europe, mainly colonising subtropical regions. Continuing adaptation to climatic conditions in temperate areas would probably result in a spread to more northern European countries, producing an increasing risk of mosquito-borne pathogen transmission over a much greater area. Based on previous studies showing that Ae. albopictus is able to overwinter in Germany, this study aims to determine more exactly its ecological limits of enduring low temperatures.METHODS: Non-diapausing and experimentally induced diapausing eggs of three different Ae. albopictus strains (tropical, subtropical and temperate origins) were exposed to four different regimes with constant temperatures and three different regimes with fluctuating temperatures in a course of a day for a minimum of 2 and a maximum of 30 days. The hatching rate of larvae after cold exposure of the eggs was taken as a measure of cold tolerance.
    RESULTS: The experiments showed that the tropical Ae. albopictus strain had a lower cold tolerance than the subtropical and the temperate strains. The eggs of all used strains were able to survive constant temperatures as low as -5 °C for an exposure period of 30 days, while constant temperatures as low as -10 °C were endured for 2 days by the tropical strain and for 10 and 20 days by the subtropical and temperate strains, respectively. At fluctuating temperatures, both the subtropical and the temperate strains exhibited hatching under all temperature regimes, even with a minimum temperature of -10 °C, whereas the tropical strain ceased hatching after an exposure period of 30 days under the temperature regime with a minimum temperature of -10 °C. The analyses showed that the temperature played the major role in interpreting the hatching rates of the eggs. The condition, whether the eggs were diapausing or not, had no significant influence, although results indicated a slightly higher cold tolerance of diapausing eggs at -10 °C.
    CONCLUSIONS: It must be expected that subtropical and temperate strains of Ae. albopictus are able to withstand common central European winters and are able to establish in considerable parts of the continent.
    Keywords:  Asian tiger mosquito; Cold acclimation; Cold hardiness; Constant temperatures; Diapause; Fluctuating temperatures; Hatching; Overwintering; Temperature tolerance
    DOI:  https://doi.org/10.1186/s13071-020-04386-7
  11. BMC Med. 2020 Nov 27. 18(1): 364
    A serological framework to investigate acute primary and post-primary dengue cases reporting across the Philippines.
    Joseph R Biggs, Ava Kristy Sy, Oliver J Brady, Adam J Kucharski, Sebastian Funk, Mary Anne Joy Reyes, Mary Ann Quinones, William Jones-Warner, Yun-Hung Tu, Ferchito L Avelino, Nemia L Sucaldito, Huynh Kim Mai, Le Thuy Lien, Hung Do Thai, Hien Anh Thi Nguyen, Dang Duc Anh, Chihiro Iwasaki, Noriko Kitamura, Lay-Myint Yoshida, Amado O Tandoc, Eva Cutiongco-de la Paz, Maria Rosario Z Capeding, Carmencita D Padilla, Julius Clemence R Hafalla, Martin L Hibberd.
      BACKGROUND: In dengue-endemic countries, targeting limited control interventions to populations at risk of severe disease could enable increased efficiency. Individuals who have had their first (primary) dengue infection are at risk of developing more severe secondary disease, thus could be targeted for disease prevention. Currently, there is no reliable algorithm for determining primary and post-primary (infection with more than one flavivirus) status from a single serum sample. In this study, we developed and validated an immune status algorithm using single acute serum samples from reporting patients and investigated dengue immuno-epidemiological patterns across the Philippines.METHODS: During 2015/2016, a cross-sectional sample of 10,137 dengue case reports provided serum for molecular (anti-DENV PCR) and serological (anti-DENV IgM/G capture ELISA) assay. Using mixture modelling, we re-assessed IgM/G seroprevalence and estimated functional, disease day-specific, IgG:IgM ratios that categorised the reporting population as negative, historical, primary and post-primary for dengue. We validated our algorithm against WHO gold standard criteria and investigated cross-reactivity with Zika by assaying a random subset for anti-ZIKV IgM and IgG. Lastly, using our algorithm, we explored immuno-epidemiological patterns of dengue across the Philippines.
    RESULTS: Our modelled IgM and IgG seroprevalence thresholds were lower than kit-provided thresholds. Individuals anti-DENV PCR+ or IgM+ were classified as active dengue infections (83.1%, 6998/8425). IgG- and IgG+ active dengue infections on disease days 1 and 2 were categorised as primary and post-primary, respectively, while those on disease days 3 to 5 with IgG:IgM ratios below and above 0.45 were classified as primary and post-primary, respectively. A significant proportion of post-primary dengue infections had elevated anti-ZIKV IgG inferring previous Zika exposure. Our algorithm achieved 90.5% serological agreement with WHO standard practice. Post-primary dengue infections were more likely to be older and present with severe symptoms. Finally, we identified a spatio-temporal cluster of primary dengue case reporting in northern Luzon during 2016.
    CONCLUSIONS: Our dengue immune status algorithm can equip surveillance operations with the means to target dengue control efforts. The algorithm accurately identified primary dengue infections who are at risk of future severe disease.
    Keywords:  Dengue; Flavivirus; Immuno-epidemiology; Philippines; Post-primary; Primary; Serology; Surveillance
    DOI:  https://doi.org/10.1186/s12916-020-01833-1
  12. BMC Infect Dis. 2020 Nov 24. 20(1): 881
    Seroprevalence, spatial dispersion and factors associated with flavivirus and chikungunha infection in a risk area: a population-based seroprevalence study in Brazil.
    Francisca Kalline de Almeida Barreto, Carlos Henrique Alencar, Fernanda Montenegro de Carvalho Araújo, Rhaquel de Morais Alves Barbosa Oliveira, John Washington Cavalcante, Daniele Rocha Queiroz Lemos, Luís Arthur Brasil Gadelha Farias, Isac Lucca Frota Boriz, Leticia Queiroz Medeiros, Marcelo Nunes Pereira Melo, Fábio Miyajima, André Machado Siqueira, André Ricardo Ribas Freitas, Luciano Pamplona de Góes Cavalcanti.
      BACKGROUND: The State of Ceará, in Northeastern Brazil, suffers from a triple burden of arboviruses (dengue, Zika and chikungunya). We measured the seroprevalence of chikungunya, dengue and Zika and its associated factors in the population of Juazeiro do Norte, Southern Ceará State, Brazil.METHODS: A cross-sectional study of analytical and spatial analysis was performed to estimate the seroprevalence of dengue, Zika and chikungunya, in the year 2018. Participants were tested for IgM and IgG against these three viruses. Those with IgM and/or IgG positive tests results were considered positive. Poisson regression was used to analyze the factors associated with positive cases, in the same way that the spatial analysis of positive cases was performed to verify whether the cases were grouped.
    RESULTS: Of the 404 participants, 25.0% (103/404) were positive for CHIKV, 92.0% (373/404) for flavivirus (dengue or Zika) and of these, 37.9% (153/404) samples were classified as probable dengue infection. Of those who reported having had an arbovirus in the past, positive CHIKV cases had 58.7% arthralgia (PR = 4.31; 95% CI: 2.06-9.03; p = 0.000) mainly in the hands, ankles and feet. Age over 60 years had a positive association with cases of flavivirus (PR = 1.29; 95% CI: 1.09-1.54; p = 0.000). Fever, muscle pain, joint pain and skin rash were the most reported symptoms (46.1, 41.0, 38.3 and 28.41%, respectively). The positive cases of chikungunya and dengue or Zika were grouped in space and the city center was most affected area.
    CONCLUSIONS: Four years after the introduction of CHIKV, where DENV has been in circulation for over 30 years, 1/4 of the population has already been exposed, showing the extent of the epidemic. The measured prevalence was much higher than that reported by local epidemiological surveillance.
    Keywords:  Chikungunya virus; Dengue virus; Seroprevalence; Zika virus
    DOI:  https://doi.org/10.1186/s12879-020-05611-5
  13. Infect Dis Poverty. 2020 Nov 22. 9(1): 160
    Malaria epidemiology and stratification of incidence in the malaria elimination setting in Harari Region, Eastern Ethiopia.
    Endashaw Esayas, Asefa Tufa, Fekadu Massebo, Abdulhamid Ahemed, Ibssa Ibrahim, Dereje Dillu, Eyuel Asemahegn Bogale, Solomon Yared, Kebede Deribe.
      BACKGROUND: Ethiopia has shown notable progress in reducing the burden of malaria over the past two decades. Because of this progress, the country has shifted efforts from control to elimination of malaria. This study was conducted to analyse the malaria epidemiology and stratification of incidence in the malaria elimination setting in eastern Ethiopia.METHODS: A retrospective study was conducted to analyse the epidemiology of malaria by reviewing the district health office data from 2013 to 2019 in Harari Region. In addition, three years of sub-district level malaria data were used to stratify the malaria transmission intensity. Malaria interventions (Long-lasting insecticidal nets [LLIN] and indoor residual spraying [IRS]) employed were reviewed to analyse the intervention coverage at the Regional level. Descriptive statistics were used to show the malaria transmission in terms of years, season and species of the malaria parasite. Incidence rate per 1000 population and death rate per 1 000 000 population at risk were computed using the total population of each year.
    RESULTS: In the Harari Region, malaria incidence showed a more pronounced declining trend from 2017 to 2019. Plasmodium falciparum, P. vivax and mixed infections accounted for 69.2%, 30.6% and 0.2% of the cases, respectively. There was an increment in malaria intervention coverage and improved malaria diagnosis. In the year 2019 the coverage of LLIN and IRS in the Region were 93.4% and 85.1% respectively. The annual malaria incidence rate dropped from 42.9 cases per 1000 population in 2013 to 6.7 cases per 1000 population in 2019. Malaria-related deaths decreased from 4.7 deaths per 1 000 000 people annually in 2013 to zero, and there have been no deaths reported since 2015. The malaria risk appears to be heterogeneous and varies between districts. A higher number of malaria cases were recorded in Erer and Jenella districts, which constitute 62% of the cases in the Region. According to the sub-district level malaria stratification, there was shrinkage in the malaria transmission map and about 70% of the sub-districts have achieved elimination targets.
    CONCLUSIONS: In the Harari Region, malaria morbidity and mortality have been significantly declined. Thus, if this achievement is sustained and scaling-up of the existing malaria prevention and control strategies by focusing on those populations living in the higher malaria transmission districts and sub-districts, planning of malaria elimination from the study area might be feasible.
    Keywords:  Epidemiology; Ethiopia; Harari region; Incidence; Interventions; Malaria elimination; Stratification; Sub-district
    DOI:  https://doi.org/10.1186/s40249-020-00773-5
  14. Malar J. 2020 Nov 23. 19(1): 422
    Capacity of National Malaria Control Programmes to implement vector surveillance: a global analysis.
    Tanya L Russell, Robert Farlow, Myo Min, Effie Espino, Abraham Mnzava, Thomas R Burkot.
      BACKGROUND: Solving the problem of malaria requires a highly skilled workforce with robust infrastructure, financial backing and sound programme management coordinated by a strategic plan. Here, the capacity of National Malaria Control Programmes (NMCPs) was analysed to identify the strengths and weaknesses underpinning the implementation of vector surveillance and control activities by the core elements of programme capacity, being strategic frameworks, financing, human resources, logistics and infrastructure, and information systems.RESULTS: Across nearly every country surveyed, the vector surveillance programmes were hampered by a lack of capacity and capability. Only 8% of NMCPs reported having sufficient capacity to implement vector surveillance. In contrast, 57%, 56% and 28% of NMCPs had the capacity to implement long-lasting insecticidal nets (LLINs), indoor residual spraying (IRS) and larval source management (LSM) activities, respectively. Largely underlying this was a lack of up-to-date strategic plans that prioritize vector surveillance and include frameworks for decision-making and action.
    CONCLUSIONS: Strategic planning and a lack of well-trained entomologists heavily hamper vector surveillance. Countries on the path to elimination generally had more operational/field staff compared to countries at the stage of control, and also were more likely to have an established system for staff training and capacity building. It is unlikely that controlling countries will make significant progress unless huge investments also go towards increasing the number and capacity of programmatic staff.
    Keywords:  Anopheles; Capacity building; Logic framework; Malaria; Needs Assessment; Vector surveillance
    DOI:  https://doi.org/10.1186/s12936-020-03493-1
  15. PLoS Biol. 2020 Nov;18(11): e3000791
    Building resilience to mosquito-borne diseases in the Caribbean.
    Rachel Lowe, Sadie J Ryan, Roché Mahon, Cedric J Van Meerbeeck, Adrian R Trotman, Laura-Lee G Boodram, Mercy J Borbor-Cordova, Anna M Stewart-Ibarra.
      Small island developing states in the Caribbean are among the most vulnerable countries on the planet to climate variability and climate change. In the last 3 decades, the Caribbean region has undergone frequent and intense heat waves, storms, floods, and droughts. This has had a detrimental impact on population health and well-being, including an increase in infectious disease outbreaks. Recent advances in climate science have enhanced our ability to anticipate hydrometeorological hazards and associated public health challenges. Here, we discuss progress towards bridging the gap between climate science and public health decision-making in the Caribbean to build health system resilience to extreme climatic events. We focus on the development of climate services to help manage mosquito-transmitted disease epidemics. There are numerous areas of ongoing biological research aimed at better understanding the direct and indirect impacts of climate change on the transmission of mosquito-borne diseases. Here, we emphasise additional factors that affect our ability to operationalise this biological understanding. We highlight a lack of financial resources, technical expertise, data sharing, and formalised partnerships between climate and health communities as major limiting factors to developing sustainable climate services for health. Recommendations include investing in integrated climate, health and mosquito surveillance systems, building regional and local human resource capacities, and designing national and regional cross-sectoral policies and national action plans. This will contribute towards achieving the Sustainable Development Goals (SDGs) and maximising regional development partnerships and co-benefits for improved health and well-being in the Caribbean.
    DOI:  https://doi.org/10.1371/journal.pbio.3000791
  16. Acta Trop. 2020 Nov 24. pii: S0001-706X(20)31678-8. [Epub ahead of print] 105765
    Description of the ovarian microbiota of Aedes aegypti (L) Rockefeller strain.
    Wilber A Alvarado, Susana Ochoa Agudelo, Iván Darío Velez, Rafael José Vivero.
      Aedes aegypti is one of the vectors responsible for transmitting the viruses that cause dengue, Zika and chikungunya in the human population. Mosquitoes have bacterial communities in different organs, mainly in the midgut, but to a lesser extent in their reproductive organs, such as the ovaries, where replication and vertical transmission is decisive for dengue virus. These bacteria also influence metabolic and physiological processes such as ingestion and digestion of blood. In this study, aerobic bacterial communities associated with ovaries of A. aegypti Rockefeller strain were determined, describing their potential function during ovocitary development. The groups of mosquitoes were separated into three treatments: diet with 10% sugar solution, diet with blood supply, and blood feeding combined with tetracycline. The ovaries were extracted from the mosquitoes, and then put in enriched culture media (blood and nutritive agar) by direct inoculation, for subsequent isolation and macroscopic and microscopic characterization of the colonies. The taxonomic determination of bacterial isolates was achieved by sequence analysis of the 16S rRNA gene. A higher bacterial load was observed in the sugar feeding group (6 × 10³ CFU/ml) in contrast to the group fed only with blood, with and without an antibiotic (4.03-4.04 × 10³CFU/ml; 4.85-5.04 × 10³CFU/ml). As a result, a total of 35 colonies were isolated, of which 80% were gram-negative and 20% gram-positive; 72% were lactose negative and 8% lactose positive. Of the total bacteria, 83% had gamma hemolysis, 17% alpha hemolysis, and none presented beta hemolysis. After phenotypic and biochemical characterization, 17 isolates were selected for molecular identification. Only phyla Actinobacteria and Proteobacteria were found. Bacteria associated with ovaries of A. aegypti were mainly identified as belonging to the Serratia and Klebsiella genera. Some bacteria (Serratia marcescens, Pantoea dispersa and Klebsiella oxytoca) have wide biotechnological potential due to their entomopathogenic power and their bioactivity against different pathogens.
    Keywords:  Microbiota; biologic control; culturable fraction; ovary
    DOI:  https://doi.org/10.1016/j.actatropica.2020.105765
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