Impact of Aerial Humidity on Seasonal Malaria: An Ecological Study in Zambia

Abstract Background:. Seasonal outbreaks of malaria in many parts of Africa are generally associated with rainfall; in dry seasons malaria declines but does not always cease. We postulated that aerial moisture associated with transpiration of peri-domestic trees may provide conditions to sustain pockets of mosquitoes. This study was designed to investigate this probability. Methods: Using miniature loggers designed to record moisture and temperature, set in trees and vegetation around nine selected homesteads in rural Zambia, we have shown that local tree and plant transpiration affecting the home could support the mosquito where it rests during hot dry seasons. We assessed the conditions which supported resting mosquitoes by recording the malaria case incidence rate measured at nearby health centres and clinics during the dry months. The loggers were placed in trees near the homestead with permission from the householder. No personal data were collected.Results: Data were recorded daily for three contiguous dry seasons, 2017, 2018 and 2019. The results throw a light on conditions that impact the survival of malaria vectors in arid seasons particularly in African situations and suggests how Anopheles arabiensis and other species may survive the dry seasons. Periods of nocturnal aerial moisture correlated with increase in malaria case incidence rates recorded in the local health centres. Discussion: Data were recorded daily for three contiguous dry seasons, 2017, 2018 and 2019. The results throw a light on conditions that impact the survival of malaria vectors in arid seasons particularly in African situations and suggests how Anopheles arabiensis and other species may survive the dry seasons. Periods of nocturnal aerial moisture correlated with increase in malaria case incidence rates recorded in the local health centres. The data also support the idea that mosquito species exist sporadically in widespread population demes of vector species and this likely helps repopulate habitats when the rains return.

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Field Efficacy Evaluation of some Ethnomedicinal Plants Smoke Repellency Against Anopheles arabiensis and Aedes Aaegypt

10.21203/rs.3.rs-37049/v1 ◽

2020 ◽

Author(s):

Abenezer Wendimu ◽

Wondimagegnehu Tekalign

Keyword(s):

Anopheles Arabiensis ◽

Mosquito Species ◽

Latin Square ◽

Malaria Vectors ◽

Bed Nets ◽

Efficacy Evaluation ◽

Mixed Powder ◽

Plant Powders ◽

And Control ◽

Methods Of Application

Abstract Background: Plant products can either be used as an insecticide to kill larvae or adult mosquitoes or as defensive repellents against mosquito bites; depending on the type of activity they have. A present study was carried out to determine the repellence of smoke prepared from burning the plants in a traditional way in order to reduce human-mosquito. Methods: The candidate plant species (Azadirachta indica, Eucalyptus camaldulensis, and Ocimum forskolin) leave was grounded and mixed together in an equal amount. The mixed plant powders were checked by the thermal expulsion and burning on the traditional stoves in the field against two important malaria vectors (Anopheles arabiensis and Aedesaegypt). A four-by-four Latin-square design was used to randomly assign treatment and control experimental huts over different nights. In the treatment and control huts, the percentage repellence of the candidate plants mixed powder smoke on mosquito was determined from mosquito catches. Results: On direct burning of the plants' powder, the highest percentage repellency for An. arabiensis (94.7%, P<0.001) and Aedesaegypt (88.4%, P<0.001) recorded. On thermal expulsion also the highest against An. arabiensis (89%, P<0.001) and against Aedesaegypt (92%, P<0.001) were recorded. The plants' mixed powder tested by both methods of application offered significant protection (>85%) against two important mosquito species and thus has the potential to be used at least as an alternative way to control mosquito infestation in an easy manner in economic level.Conclusion: The two methods of application may offer cost-efficient alternatives as additional household protection and as a helpful addition to bed nets, especially for the early part of the evening before bedtime.

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Chromosome-level genome assemblies of the malaria vectors Anopheles coluzzii and Anopheles arabiensis

GigaScience ◽

10.1093/gigascience/giab017 ◽

2021 ◽

Vol 10 (3) ◽

Cited By ~ 1

Author(s):

Anton Zamyatin ◽

Pavel Avdeyev ◽

Jiangtao Liang ◽

Atashi Sharma ◽

Chujia Chen ◽

...

Keyword(s):

Anopheles Arabiensis ◽

De Novo ◽

Mosquito Species ◽

Sub Saharan Africa ◽

Malaria Vectors ◽

Anopheles Coluzzii ◽

Reference Quality ◽

Sub Saharan ◽

Genome Assemblies ◽

Chromosome Level

Abstract Background Anopheles coluzzii and Anopheles arabiensis belong to the Anopheles gambiae complex and are among the major malaria vectors in sub-Saharan Africa. However, chromosome-level reference genome assemblies are still lacking for these medically important mosquito species. Findings In this study, we produced de novo chromosome-level genome assemblies for A. coluzzii and A. arabiensis using the long-read Oxford Nanopore sequencing technology and the Hi-C scaffolding approach. We obtained 273.4 and 256.8 Mb of the total assemblies for A. coluzzii and A. arabiensis, respectively. Each assembly consists of 3 chromosome-scale scaffolds (X, 2, 3), complete mitochondrion, and unordered contigs identified as autosomal pericentromeric DNA, X pericentromeric DNA, and Y sequences. Comparison of these assemblies with the existing assemblies for these species demonstrated that we obtained improved reference-quality genomes. The new assemblies allowed us to identify genomic coordinates for the breakpoint regions of fixed and polymorphic chromosomal inversions in A. coluzzii and A. arabiensis. Conclusion The new chromosome-level assemblies will facilitate functional and population genomic studies in A. coluzzii and A. arabiensis. The presented assembly pipeline will accelerate progress toward creating high-quality genome references for other disease vectors.

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Spatial Anopheles arabiensis (Diptera: Culicidae) insecticide resistance patterns across malaria-endemic regions of Botswana

Malaria Journal ◽

10.1186/s12936-020-03487-z ◽

2020 ◽

Vol 19 (1) ◽

Author(s):

Mmabaledi Buxton ◽

Ryan J. Wasserman ◽

Casper Nyamukondiwa

Keyword(s):

Malaria Control ◽

Anopheles Arabiensis ◽

Prolonged Exposure ◽

Mosquito Species ◽

Intervention Strategy ◽

Virgin Female ◽

World Health ◽

Malaria Vectors ◽

Mosquito Vector ◽

Susceptibility Status

Abstract Background Since the advent of the Green Revolution, pesticides have played an important role in the global management of invertebrate pests including vector mosquitoes. Despite optimal efficacy, insects often display insensitivity to synthetic insecticides owing to prolonged exposure that may select for resistance development. Such insecticide insensitivity may regress national and regional coordination in mosquito vector management and indeed malaria control. In Botswana, prolonged use of synthetic insecticides against malaria vectors have been practiced without monitoring of targeted mosquito species susceptibility status. Methods Here, susceptibility status of a malaria vector (Anopheles arabiensis), was assessed against World Health Organization-recommended insecticides, across three malaria endemic districts. Adult virgin female mosquitoes (2–5 days old) emerging from wild-collected larvae were exposed to standardized insecticide-impregnated papers with discriminating doses. Results The results showed resistance dynamics were variable in space, presumably as a result of spatial differences in insecticide use across malaria endemic districts and the types of insecticides used in the country. Overall, there was a reduced susceptibility of An. arabiensis for the pyrethroid lambda-cyhalothrin and for dichloro diphenyl trichloroethane [DDT], which have similar modes of action and have been used in the country for many years. The Okavango district exhibited the greatest reduction in susceptibility, followed by Ngamiland and then Bobirwa, reflective of national intervention strategy spraying intensities. Vector mosquitoes were, however, highly susceptible to carbamates and organophosphates irrespective of region. Conclusions These results provide important findings of vector susceptibility to insecticides recommended for vector control. The results highlight the need to implement insecticide application regimes that more effectively including regionally integrated resistance management strategies for effective malaria control and elimination.

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Microbiota identified from preserved Anopheles

Malaria Journal ◽

10.1186/s12936-021-03754-7 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Bianca E Silva ◽

Zvifadzo Matsena Zingoni ◽

Lizette L. Koekemoer ◽

Yael L. Dahan-Moss

Keyword(s):

Microbial Diversity ◽

Vector Competence ◽

Mosquito Species ◽

Anopheles Funestus ◽

Cost Effective ◽

Diversity Indices ◽

Malaria Vectors ◽

Microbial Composition ◽

Culture Independent ◽

Culture Dependent

Abstract Background Mosquito species from the Anopheles gambiae complex and the Anopheles funestus group are dominant African malaria vectors. Mosquito microbiota play vital roles in physiology and vector competence. Recent research has focused on investigating the mosquito microbiota, especially in wild populations. Wild mosquitoes are preserved and transported to a laboratory for analyses. Thus far, microbial characterization post-preservation has been investigated in only Aedes vexans and Culex pipiens. Investigating the efficacy of cost-effective preservatives has also been limited to AllProtect reagent, ethanol and nucleic acid preservation buffer. This study characterized the microbiota of African Anopheles vectors: Anopheles arabiensis (member of the An. gambiae complex) and An. funestus (member of the An. funestus group), preserved on silica desiccant and RNAlater® solution. Methods Microbial composition and diversity were characterized using culture-dependent (midgut dissections, culturomics, MALDI-TOF MS) and culture-independent techniques (abdominal dissections, DNA extraction, next-generation sequencing) from laboratory (colonized) and field-collected mosquitoes. Colonized mosquitoes were either fresh (non-preserved) or preserved for 4 and 12 weeks on silica or in RNAlater®. Microbiota were also characterized from field-collected An. arabiensis preserved on silica for 8, 12 and 16 weeks. Results Elizabethkingia anophelis and Serratia oryzae were common between both vector species, while Enterobacter cloacae and Staphylococcus epidermidis were specific to females and males, respectively. Microbial diversity was not influenced by sex, condition (fresh or preserved), preservative, or preservation time-period; however, the type of bacterial identification technique affected all microbial diversity indices. Conclusions This study broadly characterized the microbiota of An. arabiensis and An. funestus. Silica- and RNAlater®-preservation were appropriate when paired with culture-dependent and culture-independent techniques, respectively. These results broaden the selection of cost-effective methods available for handling vector samples for downstream microbial analyses.

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Insecticide resistance status of Anopheles arabiensis in irrigated and non-irrigated areas in western Kenya

Parasites & Vectors ◽

10.1186/s13071-021-04833-z ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Pauline Winnie Orondo ◽

Steven G. Nyanjom ◽

Harrysone Atieli ◽

John Githure ◽

Benyl M. Ondeto ◽

...

Keyword(s):

Insecticide Resistance ◽

Vector Control ◽

Anopheles Arabiensis ◽

Crop Protection ◽

Indoor Residual Spraying ◽

Malaria Vectors ◽

Western Kenya ◽

Animal Protection ◽

Selection Of ◽

Selection Of Resistance

Abstract Background Malaria control in Kenya is based on case management and vector control using long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). However, the development of insecticide resistance compromises the effectiveness of insecticide-based vector control programs. The use of pesticides for agricultural purposes has been implicated as one of the sources driving the selection of resistance. The current study was undertaken to assess the status and mechanism of insecticide resistance in malaria vectors in irrigated and non-irrigated areas with varying agrochemical use in western Kenya. Methods The study was carried out in 2018–2019 in Homa Bay County, western Kenya. The bioassay was performed on adults reared from larvae collected from irrigated and non-irrigated fields in order to assess the susceptibility of malaria vectors to different classes of insecticides following the standard WHO guidelines. Characterization of knockdown resistance (kdr) and acetylcholinesterase-inhibiting enzyme/angiotensin-converting enzyme (Ace-1) mutations within Anopheles gambiae s.l. species was performed using the polymerase chain reaction (PCR) method. To determine the agricultural and public health insecticide usage pattern, a questionnaire was administered to farmers, households, and veterinary officers in the study area. Results Anopheles arabiensis was the predominant species in the irrigated (100%, n = 154) area and the dominant species in the non-irrigated areas (97.5%, n = 162), the rest being An. gambiae sensu stricto. In 2018, Anopheles arabiensis in the irrigated region were susceptible to all insecticides tested, while in the non-irrigated region reduced mortality was observed (84%) against deltamethrin. In 2019, phenotypic mortality was decreased (97.8–84% to 83.3–78.2%). In contrast, high mortality from malathion (100%), DDT (98.98%), and piperonyl butoxide (PBO)-deltamethrin (100%) was observed. Molecular analysis of the vectors from the irrigated and non-irrigated areas revealed low levels of leucine-serine/phenylalanine substitution at position 1014 (L1014S/L1014F), with mutation frequencies of 1–16%, and low-frequency mutation in the Ace-1R gene (0.7%). In addition to very high coverage of LLINs impregnated with pyrethroids and IRS with organophosphate insecticides, pyrethroids were the predominant chemical class of pesticides used for crop and animal protection. Conclusion Anopheles arabiensis from irrigated areas showed increased phenotypic resistance, and the intensive use of pesticides for crop protection in this region may have contributed to the selection of resistance genes observed. The susceptibility of these malaria vectors to organophosphates and PBO synergists in pyrethroids offers a promising future for IRS and insecticide-treated net-based vector control interventions. These findings emphasize the need for integrated vector control strategies, with particular attention to agricultural practices to mitigate mosquito resistance to insecticides. Graphic abstract

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A taxonomy of the scope and organization of local sexually transmitted disease services for policy and practice

International Journal of STD & AIDS ◽

10.1177/0956462418787621 ◽

2018 ◽

Vol 29 (14) ◽

pp. 1375-1383

Author(s):

Hector P Rodriguez ◽

Summer Starling ◽

Zosha Kandel ◽

Robert Weech-Maldonado ◽

Nicholas J Moss ◽

...

Keyword(s):

Cluster Analysis ◽

Discriminant Analysis ◽

Critical Role ◽

Transmitted Disease ◽

The United States ◽

Incidence Rates ◽

Contact Tracing ◽

Cluster Solution ◽

Local Health ◽

Sexually Transmitted

Local health departments (LHDs) and their organizational partners play a critical role in controlling sexually transmitted diseases (STDs) in the United States. We examine variation in the differentiation, integration, and concentration (DIC) of STD services and develop a taxonomy describing the scope and organization of local STD services. LHD STD programs (n = 115) in Alabama (AL) and California (CA) responded to surveys assessing STD services available in 2014. K-means cluster analysis identified LHD groupings based on DIC variation. Discriminant analysis validated cluster solutions. Differences in organizational partnerships and scope of STD services were compared by taxonomy category. Multivariable regression models estimated the association of the STD services organization taxonomy and five-year (2010–2014) gonorrhea incidence rates, controlling for county-level sociodemographics and resources. A three-cluster solution was identified: (1) low DIC (n = 74), (2) moderate DIC (n = 31), and (3) high DIC (n = 10). In discriminant analysis, 95% of jurisdictions were classiﬁed into the same types as originally assigned through K-means cluster analysis. High DIC jurisdictions were more likely (p < 0.001) to partner with most organizations than moderate and low DIC jurisdictions, and more likely (p < 0.001) to conduct STD needs assessment, comprehensive sex education, and targeted screening. In contrast, contact tracing, case management, and investigations were conducted similarly across jurisdictions. In adjusted analyses, there were no differences in gonorrhea incidence rates by category. Jurisdictions in CA and AL can be characterized into three distinct clusters based on the DIC of STD services. Taxonomic analyses may aid in improving the reach and effectiveness of STD services.

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Universal varicella vaccination in the Sicilian paediatric population: rapid uptake of the vaccination programme and morbidity trends over five years

Eurosurveillance ◽

10.2807/ese.14.35.19321-en ◽

2009 ◽

Vol 14 (35) ◽

Author(s):

G Giammanco ◽

S Ciriminna ◽

I Barberi ◽

L Titone ◽

M Lo Giudice ◽

...

Keyword(s):

Vaccination Programme ◽

Vaccine Coverage ◽

Varicella Vaccine ◽

Age Groups ◽

Vaccination Strategy ◽

Paediatric Population ◽

Incidence Rates ◽

Universal Vaccination ◽

Varicella Vaccination ◽

Local Health

Following the licensure of the Oka/Merck varicella vaccine in Italy in January 2003, the Sicilian health authorities launched a universal vaccination programme in all nine Local Health Units. A two-cohort vaccination strategy was adopted to minimise the shift of the mean age of varicella occurrence to older age groups, with the goal of vaccinating with one dose at least 80% of children in their second year of life and 50% of susceptible adolescents in their 12th year of life. Two studies were implemented in parallel to closely monitor vaccination coverage as well as varicella incidence. Overall, the programme achieved its target, with 87.5% vaccine coverage for the birth cohort 2005 and 90.2% for adolescents born in 1995 and 1996. Varicella surveillance data obtained from a total of 28,188 children (0-14 years-old) monitored by family paediatricians showed a decline in incidence rates from 95.7 (95% confidence interval (CI): 72.2-126.8) for 1,000 person-years (PY) in 2004 to 9.0 (95% CI: 6.4-12.6) for 1,000 PY in 2007. In Europe, the only similar experience is the routine childhood varicella vaccination programme in Germany that started in 2004 with a single dose at the age of 11-14 months. The two-cohort universal vaccination programme implemented in Sicily, as well as the network for the surveillance study, can offer a model to other European countries that are considering introducing universal childhood varicella vaccination.

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The rise and fall of Anopheles arabiensis (Diptera: Culicidae) in a Tanzanian village

Bulletin of Entomological Research ◽

10.1017/s0007485300051993 ◽

1995 ◽

Vol 85 (1) ◽

pp. 37-44 ◽

Cited By ~ 53

Author(s):

J.D. Charlwood ◽

J. Kihonda ◽

S. Sama ◽

P.F. Billingsley ◽

H. Hadji ◽

...

Keyword(s):

Life Cycle ◽

Survival Rate ◽

Anopheles Arabiensis ◽

Light Trapping ◽

Population Decline ◽

Malaria Vectors ◽

General Applicability ◽

Dry Spell ◽

The Village

AbstractThe continual recruitment of new individuals makes it difficult to study both the survival of multivoltine mosquitoes, and the size of the infectious reservoir in narural populations of malaria vectors. During long-term surveillance of a population of Anopheles gambiae Giles sensu lato in a Tanzanian village by daily light trapping, a temporary dry spell resulted in the cessation of recruitment for a period of 33 days, and a decline in numbers of A. arabiensis Patton caught from over 2000 to less than 10 in a sentinel house. Traps placed elsewhere in the village indicated similar proportionate declines although numbers caught varied according to location. A survival rate of 83% per day was estimated from the rate of population decline. Survival was unrelated to the size of the mosquitoes. The infectious reservoir (the chance of a mosquito acquiring an infection) was estimated to be 2% per feed. The exploitation of fortuitous events which temporarily eliminate a single stage in the life cycle has general applicability in the study of the bionomics of multivoltine insects.

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