92 research outputs found
Zoom in at African Country level: Potential Climate Induced Changes in Areas of Suitability for Survival of Malaria Vectors
Predicting anopheles vectors’ population densities and boundary shifts is crucial in preparing for malaria risks and unanticipated outbreaks. Although shifts in the distribution and boundaries of the major malaria vectors (Anopheles gambiae s.s. and An. arabiensis) across Africa have been predicted, quantified areas of absolute change in zone of suitability for their survival have not been defined. In this study, we have quantified areas of absolute change conducive for the establishment and survival of these vectors, per African country, under two climate change scenarios and based on our findings, highlight practical measures for effective malaria control in the face of changing climatic patterns. We develop a model using CLIMEX simulation to estimate the potential geographical distribution and seasonal abundance of these malaria vectors in relation to climatic factors 9temperature, rainfall and relative humidity). The model yielded an eco climatic index (EI) describing the total favorable geographical locations for the species. The EI value were classified and exposed to a GIS package. Using ArcGIS, the EI shape points clipped to the extent of Africa and then converted to a raster layer using inverse Distance Weighted (IDW) interpolation method. Generated maps wre then transformed into polygon-based geo-referenced data set and areas computed and expressed in square kilometers (km2). Five classes of EI were derived indicating the level of survivorship of these malaria vectors. The proportion of areas increasing or decreasing in level of survival of these malaria vectors will be more pronounced in eastern and southern African countries than those in western Africa. Angola, Ethiopia, Kenya, Mozambique, Tanzania, South Africa and Zambia appear most likely to be affected in terms of absolute change of malaria vectors suitability zones under the selected climate change scenarios. The potential shifts of these malaria vectors have implications for human exposure to malaria, as recrudescence of the disease is likely to be recorded in several new areas and regions. Therefore, the need to develop, compile and share malaria preventive measures, which can be adapted to different climatic scenarios, remains crucial. \u
Risk assessment of urban yellow fever virus transmission in Kenya : is Aedes aegypti an efficient vector?
The absence of urban yellow fever epidemics in East Africa remains a mystery amidst the proliferation of Aedes aegypti in
this region. To understand the transmission dynamics of the disease, we tested urban (Mombasa, Kisumu, and Nairobi)
Aedes mosquito populations in Kenya for their susceptibility to an East African yellow fever virus (YFV) genotype. Overall,
22% (n = 805) of the Ae. aegypti that were orally challenged with an infectious dose of YFV had a midgut infection, with
comparable rates for Mombasa and Kisumu (χ2= 0.35, df = 1, P = 0.55), but significantly lower rates for Nairobi (χ2 ≥ 11.08,
df = 1, P ≤ 0.0009). Variations in YFV susceptibility (midgut infection) among Ae. aegypti subspecies were not associated
with discernable cytochrome c oxidase subunit 1 gene haplotypes. Remarkably, no YFV dissemination or transmission
was observed among the orally challenged Ae. aegypti populations. Moreover, Ae. aegypti mosquitoes that were
intrathoracically inoculated with YFV failed to transmit the virus via capillary feeding. In contrast, dissemination (oral
exposure) and transmission (intrathoracic inoculation) of YFV was observed among a few peri-domestic Ae. bromeliae
mosquitoes (n = 129) that were assessed from these urban areas. Our study highlights an inefficient urban Ae. aegypti
population, and the potential for Ae. bromeliae in sustaining an urban YFV transmission in Kenya. An assessment of
urban Ae. aegypti susceptibility to other YFV genotypes, and vector potential of urban Ae. bromeliae populations in
Kenya is recommended to guide cost-effective vaccination.The German Academic Exchange Service (DAAD); a Wellcome Trust International Intermediate Fellowship; National Institutes of Health (NIH); and the project, Combatting Arthropod Pests for better Health, Food and Climate Resilience funded by Norwegian Agency for Development Cooperation (Norad). Financial support for this research by: Swedish International Development Cooperation Agency (Sida), Swiss Agency for Development and Cooperation (SDC), Federal Democratic Republic of Ethiopia and the Government of the Republic of Kenya.https://www.tandfonline.com/journals/TEMIam2023Zoology and Entomolog
Bacteria associated with Parthenium hysterophorus root exudate influence olfactory oviposition responses of Anopheles gambiae
IntroductionPreviously, we documented that the malaria vector Anopheles gambiae responds to volatile emissions from the root exudate water of the invasive plant, Parthenium hysterophorus. However, the origin of the volatiles remains to be investigated. Here, we isolated bacteria from the root exudate water of the plant, test the influence of their volatiles in gravid An. gambiae oviposition, and examined relationships between volatile profiles and oviposition.MethodsBacteria from root exudate water of P. hysterophorus were isolated using culture on Luria Bertani medium and identified by sequencing the 16S rRNA gene. Cultures of individual isolates were evaluated for egg laying response by gravid An. gambiae and number of eggs laid compared using generalized linear models relative to those in crude bacteria-mixture. Headspace volatile emissions of the bacterial isolates were analyzed by gas chromatography coupled to mass spectrometry (GC-MS) and relationships between volatile organic compound (VOC) profiles and gravid mosquito oviposition examined using Random Forest Analysis. Proximate analysis was performed to assess the difference in volatile chemistry among the different isolates.ResultsThree isolates were identified as Gram-negative bacteria belonging to two families: Enterobacteriaceae (Enterobacter sp. and Enterobacter mori) and Alcaligenaceae (Alcaligens aquatilis). An. gambiae laid 3-fold more eggs in cultures of A. aquatilis than in those of Enterobacter sp. In turn, approx. 4-fold more eggs were laid in cultures of E. mori than A. aquatilis. Overall, 16 VOCs were identified in the headspace of the isolates belonging to the chemical classes benzenoids, pyrazines, aldehydes, terpenes, alcohols, alkanes, and indoles. Random Forest Analysis identified 10 compounds contributing the most to the attraction of odors of the bacteria isolates to oviposition. Specifically, dodecane and indole were emitted in higher amounts in odors of Enterobacter sp than the other two species. Proximate analysis revealed differential attraction of the isolates on the gravid mosquito to be associated with their volatile profiles.ConclusionOur results provide first report of E. mori or A. aquatilis mediating attractive oviposition responses in An. gambiae in support of the important role microbes play in insect oviposition. The potential use of the microbes and associated volatiles in malaria vector management needs further investigation
The combined impact of LLINs, house screening, and pull‑push technology for improved malaria control and livelihoods in rural Ethiopia : study protocol for household randomised controlled trial
ADDITIONAL FILE 1. Ethics Review approval letter.ADDITIONAL FILE 2. Ethics information sheet and consent form.BACKGROUND : The combined application of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are
commonly used malaria interventions that target indoor Anopheles vectors. Recent studies on the effects of house
screening (HS) and LLINs have demonstrated a reduction in indoor vector densities and malaria when the interventions
are combined. In addition, complementary interventions are needed to curb co-occurring pest populations
which pose menace to agricultural crop productivity and food security. However, interventions that impact malaria
mainly centre on public health strategies, overlooking subtle but important component of agricultural measures.
Addressing the coexisting risks of malaria and crop pests could contribute to improved livelihood of communities.
METHODS : A four-armed household, cluster-randomized, controlled study will be conducted to assess the combined
impact of HS, LLINs and push-pull agricultural technology (PPT) against clinical malaria in children in Ethiopia. The
unit of randomization will be the household, which includes a house and its occupants. A total of 838 households will
be enrolled in this study. In this trial 246 households will receive LLINs and HS, 250 will receive LLINs, HS and PPT, 175
households will receive LLINs and PPT. The remaining 167 houses which receive LLINs only will be used as control.
One child aged ≤14 years will be enrolled per household in each treatment and followed for clinical malaria using
active case detection to estimate malaria incidence for two malaria transmission seasons.
DISCUSSION : Episodes of clinical malaria, density of indoor biting malaria vectors, sporozoite infection rate, improved
crop infestation rate, crop yield gain, livestock productivity and cost effectiveness analysis will be the end points of
this study. Socio-economic, social demographic, cost-effectiveness analysis will be conducted using qualitative and
participatory methods to explore the acceptability of HS and PPT. Documenting the combined impact of LLINs, HS
and PPT on the prevalence of clinical malaria and crop pest damage will be the first of its kind.
TRIAL REGISTRATION : Pan African Clinical Trials Registry, PACTR202006878245287. 24/06/2020.Norwegian Agency for Development Cooperation (NORAD) through the
project Combating Arthropod Pests for Better Health, Food and Resilience to Climate Change (CAP-Africa).http://www.biomedcentral.com/bmcpublichealtham2023School of Health Systems and Public Health (SHSPH)UP Centre for Sustainable Malaria Control (UP CSMC
Outdoor malaria vector species profile in dryland ecosystems of Kenya
Outdoor biting by anopheline mosquitoes is one of the contributors to residual malaria transmission, but the profile of vectors driving this phenomenon is not well understood. Here, we studied the bionomics and genetically characterized populations of An. gambiae and An. funestus complexes trapped outdoors in three selected dryland areas including Kerio Valley, Nguruman and Rabai in Kenya. We observed a higher abundance of Anopheles funestus group members (n = 639, 90.6%) compared to those of the An. gambiae complex (n = 66, 9.4%) with An. longipalpis C as the dominant vector species with a Plasmodium falciparum sporozoite rate (Pfsp) of 5.2% (19/362). The known malaria vectors including An. funestus s.s. (8.7%, 2/23), An. gambiae (14.3%, 2/14), An. rivulorum (14.1%, 9/64), An. arabiensis (1.9%, 1/52) occurred in low densities and displayed high Pfsp rates, which varied with the site. Additionally, six cryptic species found associated with the An. funestus group harbored Pf sporozoites (cumulative Pfsp rate = 7.2%, 13/181). We detected low frequency of resistant 119F-GSTe2 alleles in An. funestus s.s. (15.6%) and An. longipalpis C (3.1%) in Kerio Valley only. Evidence of outdoor activity, emergence of novel and divergent vectors and detection of mutations conferring metabolic resistance to pyrethroid/DDT could contribute to residual malaria transmission posing a threat to effective malaria control
Phlebovirus diversity in ticks from livestock in arid ecologies in Kenya
DATA AVAILABILITY : Data will be made available on request.Phleboviruses are emerging pathogens of public health importance. However, their association with ticks is
poorly described, particularly in Africa. Here, adult ticks infesting cattle, goats and sheep were collected in two
dryland pastoralist ecosystems of Kenya (Baringo and Kajiado counties) and were screened for infection with
phleboviruses. Ticks mainly belonged to the species Rhipicephalus appendiculatus, Hyalomma impeltatum, and
Hyalomma rufipes. A fragment of the RNA-dependent RNA polymerase (RdRp) gene was identified in thirty of 671
tick pools, of which twenty-nine were from livestock sampled in Baringo county. Phylogenetic analyses revealed
that twenty-five sequences were falling in three clades within the group of tick-associated phleboviruses. The
sequences of the three clades showed nucleotide distances 8%, 19% and 22%, respectively, to previously known
viruses suggesting that these sequence fragments may belong to three distinct viruses. Viruses of the group of
tick-associated phleboviruses have been found in several countries and continents but so far have not been
associated with disease in humans or animals. In addition, five sequences were found to group with the sandflyassociated
phleboviruses Bogoria virus, Perkerra virus and Ntepes virus recently detected in the same region.
Further studies are needed to investigate the transmission and maintenance cycles of these viruses, as well as to
assess their potential to infect vertebrates.The Deutsche Forschungsgemeinschaft, the German Center for Infection Research (DZIF), Germany, a German Academic Exchange Service (DAAD) through the icipe ARPPIS-DAAD scholarship and a UP postgraduate bursary, a Wellcome Trust International Intermediate Fellowship, the Norad-funded project Combatting Arthropod Pests for better Health, Food and Climate Resilience, Swedish International Development Cooperation Agency (Sida), Swiss Agency for Development and Cooperation (SDC), Australian Centre for International Agricultural Research (ACIAR), Federal Democratic Republic of Ethiopia and the Government of the Republic of Kenya.https://www.elsevier.com/locate/ttbdisam2024Zoology and EntomologySDG-03:Good heatlh and well-bein
Circulation of Ngari virus in livestock, Kenya
DATA AVAILABILITY : The four isolates (KE_C166, KE_O93, KE_B02, and KE_B35) L, M, and S segments sequences were deposited in GenBank under the accession numbers ON755192 (https://www.ncbi.nlm.nih.gov/nuccore/ON755192) to ON755203 (https://www.ncbi.nlm.nih.gov/nuccore/ON755203).Ngari virus (NRIV) is a mosquito-borne reassortant orthobunyavirus that causes severe febrile illness and hemorrhagic fever in humans and small ruminants. Due to limited diagnostics and surveillance, NRIV has only been detected sporadically during Rift Valley fever virus outbreaks. Little is known on its interepidemic maintenance and geographic distribution. In this study, sera from cattle, goats, and sheep were collected through a cross-sectional survey after the rainy seasons between 2020 and 2021 in two pastoralist-dominated semiarid ecosystems, Baringo and Kajiado counties in Kenya. NRIV was detected in 11 apparently healthy animals (11/2,039, 0.54%) by RT-PCR and isolated in cell culture from seven individuals. Growth analyses displayed efficient replication in cells from sheep and humans in contrast to weak replication in goat cells. NRIV infection of a wide variety of different vector cells showed only rapid replication in Aedes albopictus cells but not in cells derived from other mosquito species or sandflies. Phylogenetic analyses of complete-coding sequences of L, M, and S segments of four viruses showed that the Kenyan sequences established a monophyletic clade most closely related to a NRIV sequence from a small ruminant from Mauritania. NRIV neutralizing reactivity in cattle, goats, and sheep were 41.6% (95% CI = 30 to 54.3), 52.4% (95% CI = 37.7 to 66.6), and 19% (95% CI = 9.7 to 33.6), respectively. This is the first detection of NRIV in livestock in Kenya. Our results demonstrate active and undetected circulation of NRIV in the three most common livestock species highlighting the need for an active one-health surveillance of host networks, including humans, livestock, and vectors.
IMPORTANCE : Surveillance of vectors and hosts for infection with zoonotic arthropod-borne viruses is important for early detection and intervention measures to prevent outbreaks. Here, we report the undetected circulation of Ngari virus (NRIV) in apparently healthy cattle, sheep, and goats in Kenya. NRIV is associated with outbreaks of hemorrhagic fever in humans and small ruminants. We demonstrate the isolation of infectious virus from several animals as well as presence of neutralizing antibodies in 38% of the tested animals. Our data indicate active virus circulation and endemicity likely having important implications for human and animal health.The German Research Foundation (DFG); the Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya.https://journals.asm.org/journal/mspherehj2023Medical Virolog
Viral diversity and blood-feeding patterns of Afrotropical Culicoides biting midges (Diptera: Ceratopogonidae)
DATA AVAILABILITY STATEMENT : The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/supplementary material.INTRODUCTION : Culicoides biting midges (Diptera: Ceratopogonidae) are
vectors of arboviral pathogens that primarily affect livestock represented by
Schmallenberg virus (SBV), epizootic hemorrhagic disease virus (EHDV) and
bluetongue virus (BTV). In Kenya, studies examining the bionomic features of
Culicoides including species diversity, blood-feeding habits, and association
with viruses are limited.
METHODS : Adult Culicoides were surveyed using CDC light traps in two semiarid
ecologies, Baringo and Kajiado counties, in Kenya. Blood-fed specimens
were analysed through polymerase chain reaction (PCR) and sequencing
of cytochrome oxidase subunit 1 (cox1) barcoding region. Culicoides pools
were screened for virus infection by generic RT-PCR and next-generation
sequencing (NGS).
RESULTS : Analysis of blood-fed specimens confirmed that midges had fed
on cattle, goats, sheep, zebra, and birds. Cox1 barcoding of the sampled
specimens revealed the presence of known vectors of BTV and epizootic
hemorrhagic disease virus (EHDV) including species in the Imicola group
(Culicoides imicola) and Schultzei group (C. enderleni, C. kingi, and
C. chultzei). Culicoides leucostictus and a cryptic species distantly related
to the Imicola group were also identified. Screening of generated pools
(11,006 individuals assigned to 333 pools) by generic RT-PCR revealed
presence of seven phylogenetically distinct viruses grouping in the genera
Goukovirus, Pacuvirus and Orthobunyavirus. The viruses showed an overall
minimum infection rate (MIR) of 7.0% (66/333, 95% confidence interval (CI)
5.5-8.9). In addition, full coding sequences of two new iflaviruses, tentatively
named Oloisinyai_1 and Oloisinyai_2, were generated by next-generation sequencing (NGS) from individual homogenate of Culicoides pool.
CONCLUSION : The results indicate a high genetic diversity of viruses in Kenyan
biting midges. Further insights into host-vector-virus interactions as well as
investigations on the potential clinical significance of the detected viruses
are warranted.The Deutsche Forschungsgemeinschaft, a German Academic Exchange Service (DAAD) through the icipe ARPPIS-DAAD scholarship, a UP postgraduate bursary, the Norad-funded project Combatting Arthropod Pests for better Health, Food and Climate Resilience and ICIPE core donors: Swiss Agency for Development and Cooperation (SDC), Switzerland; Swedish International Development Cooperation Agency (Sida), Sweden; Australian Centre for International Agricultural Research (ACIAR), Federal Democratic Republic of Ethiopia and the Government of the Republic of Kenya.http://www.frontiersin.org/Microbiologyam2024Zoology and EntomologySDG-03:Good heatlh and well-beingSDG-15:Life on lan
Jingmen tick virus in ticks from Kenya
Jingmen tick virus (JMTV) is an arbovirus with a multisegmented genome related to those
of unsegmented flaviviruses. The virus first described in Rhipicephalus microplus ticks collected in
Jingmen city (Hubei Province, China) in 2010 is associated with febrile illness in humans. Since
then, the geographic range has expanded to include Trinidad and Tobago, Brazil, and Uganda.
However, the ecology of JMTV remains poorly described in Africa. We screened adult ticks (n = 4550,
718 pools) for JMTV infection by reverse transcription polymerase chain reaction (RT-PCR). Ticks
were collected from cattle (n = 859, 18.88%), goats (n = 2070, 45.49%), sheep (n = 1574, 34.59%),
and free-ranging tortoises (Leopard tortoise, Stigmochelys pardalis) (n = 47, 1.03%) in two Kenyan
pastoralist-dominated areas (Baringo and Kajiado counties) with a history of undiagnosed febrile
human illness. Surprisingly, ticks collected from goats (0.3%, 95% confidence interval (CI) 0.1–0.5),
sheep (1.8%, 95% CI 1.2–2.5), and tortoise (74.5%, 95% CI 60.9–85.4, were found infected with JMTV,
but ticks collected from cattle were all negative. JMTV ribonucleic acid (RNA) was also detected in
blood from tortoises (66.7%, 95% CI 16.1–97.7). Intragenetic distance of JMTV sequences originating
from tortoise-associated ticks was greater than that of sheep-associated ticks. Phylogenetic analyses
of seven complete-coding genome sequences generated from tortoise-associated ticks formed a
monophyletic clade within JMTV strains from other countries. In summary, our findings confirm
the circulation of JMTV in ticks in Kenya. Further epidemiological surveys are needed to assess the
potential public health impact of JMTV in Kenya.DATA AVAILABILITY STATEMENT : Sequences generated were deposited to GenBank under accession numbers ON158817–ON158867, ON186499–ON186526, ON220154–ON220159 and ON212401–ON212405.
Other data presented in the study are available in the article and as supplements.SUPPLEMENTARY MATERIAL : FIGURE S1. Phylogenetic relationship of Amblyomma ticks collected from tortoises (that could not be identified at the species level using morphological keys), and other Amblyomma congeners, FIGURE S2. JMTV distance matrix, FIGURE S3. Jingmenviruses distance matrixes, TABLE S1: Primers, probes and PCR conditions used in the study [38,55,56], TABLE S2: Sequences generated in this study submitted to GenBank, TABLE S3: Relative abundance of ticks sampled from different hosts.The Deutsche Forschungsgemeinschaft; the German Center for Infection Research (DZIF), Germany; a German Academic Exchange Service (DAAD) through the icipe ARPPISDAAD scholarship; a UP postgraduate bursary; a Wellcome Trust International Intermediate Fellowship; the Norad-funded project Combatting Arthropod Pests for better Health, Food and Climate Resilience; Swedish International Development Cooperation Agency (Sida); Swiss Agency for Development and Cooperation (SDC); Federal Democratic Republic of Ethiopia, and the Government of the Republic of Kenya.https://www.mdpi.com/journal/virusesam2023Zoology and Entomolog
Detection of rift valley Fever virus interepidemic activity in some hotspot areas of kenya by sentinel animal surveillance, 2009-2012
Rift Valley fever virus causes an important zoonotic disease of humans and small ruminants in Eastern Africa and is spread primarily by a mosquito vector. In this region, it occurs as epizootics that typically occur at 5–15-year intervals associated with unusual rainfall events. It has hitherto been known that the virus is maintained between outbreaks in dormant eggs of the mosquito vector and this has formed the basis of understanding of the epidemiology and control strategies of the disease. We show here that seroconversion and sporadic acute disease do occur during the interepidemic periods (IEPs) in the absence of reported cases in livestock or humans. The finding indicates that previously undetected low-level virus transmission during the IEPs does occur and that epizootics may also be due to periodic expansion of mosquito vectors in the presence of both circulating virus and naïve animals
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