Biology subjects

Lutomiah, J.

Publications and source records attributed to Lutomiah, J..

7 recordsLinked to original sources

bioRxiv2026

Isolation and characterisation of novel fruit bat alphaherpesvirus from Rousettus aegyptiacus bats in Coastal Kenya

BackgroundHerpesviruses are a group of double-stranded DNA viruses known to infect a wide range of vertebrates and establish life-long latent infections. While bats serve as natural reservoir hosts for numerous viral families, relatively few bat herpesviruses have been successfully isolated. In this study, we report the isolation and characterization of two novel alphaherpesvirus strains obtained from Rousettus aegyptiacus bats in Coastal Kenya. MethodsThe samples of oral and rectal swabs were collected from three different species of bats from coastal Kenya between October 2024 and April 2025; the bat species collected include Hipposideros spp., Coleura afra, and Rousettus aegyptiacus. Virus isolation was performed by inoculation of samples in Vero E6 cells and subsequent monitoring for cytopathic effects (CPE). Total nucleic acids were extracted from CPE positive cultures and subjected to library preparation to enable unbiased detection of both RNA and DNA viruses. The libraries were sequenced using next-generation sequencing with Illumina MiSeq platform. Subsequently, bioinformatic analysis was carried out to identify the virus, generate consensus genomes as well as phylogenetic analysis to determine the placement of identified viruses. ResultsTwo samples from R. aegyptiacus (KIK_460_O and KIK_465_O) induced typical CPE within five days. Sequencing and assembly yielded partial consensus sequences of approximately 60 kb (KIK_460_O) and 70 kb (KIK_465_O), representing extended genomic data for a bat-associated alphaherpesvirus. This virus has a genome of about 140kb, indicating that our partial assemblies account for about 43-50% of the total genome. Both isolates were found to be closely related to Dzifa herpesvirus, an alphaherpesvirus previously identified in Kilifi, Kenya. Alphaherpesvirus was identified based on partial sequencing of UL19 (3,787bp) and UL30 (2,846bp) genes. The two isolates were found to be identical at the UL19 gene, showing that they belonged to the same virus strain. Phylogenetic analysis showed that the novel alphaherpesvirus belongs to primate alphaherpesviruses under the subfamily Alphaherpesvirinae. ConclusionThis study reports the isolation and genomic characterization of a novel fruit bat alphaherpesvirus from Kenyan Rousettus aegyptiacus bats. The partial genome assembly (60-70 kb) represent the first extended genomic data for this virus, covering approximately 43-50% of the estimated 140 kb complete genome. The phylogenetic placement of this alphaherpesvirus near primate viruses, especially Pteropodid alphaherpesvirus 1, suggests bat-association and needs further investigation into its zoonotic potential.

microbiology↗

bioRxiv2026

Pyrethroid Resistance Status and Multiple kdr Mutations (F1534C/L) in Aedes aegypti Populations from Zika-prone Areas in Lamu County, Kenya

Aedes aegypti mosquitoes are the primary vectors for dengue, yellow fever, chikungunya and zika virus transmission, posing significant public health risks. In Kenya, these viruses drive disease outbreaks especially, dengue and chikungunya with coastal Kenya being the most affected. Low-level circulation of the Zika virus has been reported in parts of the Kenyan coast, with confirmed cases reported in Lamu County between August to September 2024. Except for yellow fever, there are no approved vaccines or therapeutics, hence vector control remains the most effective means of protection. However, prolonged exposure to insecticides can lead to resistance, threatening these interventions. Therefore, monitoring resistance in mosquito populations is critical to allow for appropriate interventions using effective chemical classes to prevent disease outbreaks. This study aimed to establish the levels of resistance to pyrethroids, and associated markers, among Ae. aegypti populations in sections of Lamu County where there had been a recent localized outbreak of Zika. Mosquito eggs were collected from Mkomani, Kashmir, and Kandahar villages in Lamu County, reared and tested for susceptibility to three pyrethroid insecticides (0.75% permethrin, 0.05% Alpha-cypermethrin and 0.05% deltamethrin) using WHO tube assays. Genotyping of knockdown resistance (kdr) mutations L982W, S989P, A1007G, V1016G/I, and F1534C was done using Sanger sequencing. Association between resistant phenotypes and genotypes were inferred. The results varied between the three pyrethroids with high resistance to permethrin observed (6-15% mortality), for deltamethrin mortality ranged between 53-57%, while for alphacypermethrin 88%-99% mortality was observed. Two mutation types and six genotypes were identified at F1534. No other kdr mutations were detected. The CC genotype was significantly associated with 0.75% permethrin resistance in Ae. aegypti populations (OR = 2.87, 95% CI: 1.34-6.17, P = 0.0036). The current data show that Ae. aegypti from Kandahar, Kashmir and Mkomani villages in Lamu County have developed very high resistance to permethrin, and varying resistance to other pyrethroids, thus threatening pyrethroid-based control strategies in this region, highlighting the need for alternative strategies to control the vector for arboviruses.

evolutionary biology↗

bioRxiv2024

Genomic sequence analysis of the first mpox virus detected in Kenya

Mpox is a zoonotic disease caused by the Monkeypox virus (MPXV) in the family: Poxviridae, genus: Orthopoxvirus. Historically, the disease was restricted mostly to Africa with cases being reported in Central Africa (mostly caused by clade I) and in West Africa (caused by clade II). However, there has been a recent shift in the virus range with outbreaks being reported in Europe and America, and in countries where the virus was initially not endemic. This multi-country outbreak was driven mostly by clade IIb lineage of MPXV. Since December 2023, there has been an ongoing mpox outbreak in the Democratic Republic of Congo (DRC), driven by a new clade I lineage of the virus, designated clade Ib. The DRC outbreak has persisted, with an increase in cases being reported over the past few months. Spillover of these outbreak-related cases to the neighbouring countries have also been reported in multiple countries including Uganda and Rwanda. Here, we report the rapid application of unbiased metagenomic next generation sequencing (mNGS) to reconstruct the genome sequence of the first reported case of MPXV in Kenya. Our findings show that the Kenyan case clusters together with clade Ib MPXV strains, associated with the sustained outbreak in the DRC. Clade Ib lineage has been associated with continuing geographical expansion of the virus to previously unaffected areas, high incidence of the disease as well as high case fatality (CFR 4.9-6.7%). Similar to other clade Ib strains, the Kenyan strain carries predominant APOBEC3-type mutations which is characteristic feature of human-to-human transmission, highlighting the need for surveillance to curtail any potential expansion of this MPXV strain. The lack of information on genomes associated with cases reported in different East African countries, is a gap that urgently needs to be addressed to aid in the monitoring of this MPXV strain. This case investigation, therefore, underscores the need for sequencing efforts to be enhanced across the continent to help improve our understanding of the geographical range and diversity of the MPXV strains, especially those belonging to clade I which is currently under-represented.

genomics↗

bioRxiv2024

Discovery and characterization of chromosomal inversions in the arboviral vector mosquito Aedes aegypti

Chromosomal inversions play a fundamental role in evolution and have been shown to regulate epidemiologically important traits in malaria mosquitoes. However, they have never been characterized in Aedes aegypti, the major vector of arboviruses, because of the poor structure of its polytene chromosomes. In this study, we applied a Hi-C proximity ligation approach to identify chromosomal inversions in 25 strains of Ae. aegypti, acquired from its worldwide distribution, as well as in one strain of Ae. mascarensis. The study identified 21 multi-megabase inversions with uneven distributions along the three chromosomes. All chromosomal inversions, including one specific for Ae. mascarensis, were polymorphic. Nevertheless, geographic origin separated the strains into two clusters carrying African and non-African inversions suggesting their potential association with Ae. aegypti subspecies. Some of the inversions colocalized with chemoreceptor genes and quantitative trait loci associated with pathogen infection, implicating the potential role of inversions in host choice and disease transmission.

evolutionary biology↗

bioRxiv2023

Extensive variation and strain-specificity in dengue virus susceptibility among African Aedes aegypti populations

African populations of the mosquito Aedes aegypti are usually considered less susceptible to infection by human-pathogenic flaviviruses than globally invasive populations found outside Africa. Although this contrast has been well documented for Zika virus (ZIKV), it is unclear to what extent it is true for dengue virus (DENV), the most prevalent flavivirus of humans. Addressing this question is complicated by substantial genetic diversity among DENV strains, most notably in the form of four genetic types (DENV1 to DENV4), that can lead to genetically specific interactions with mosquito populations. Here, we carried out a continent-wide survey of DENV susceptibility using a panel of field-derived Ae. aegypti colonies from across the African range of the species and a colony from Guadeloupe, French West Indies as non-African reference. We found considerable variation in the ability of African Ae. aegypti populations to acquire and replicate a panel of six DENV strains spanning the four DENV types. Although African Ae. aegypti populations were generally less susceptible than the reference non-African population from Guadeloupe, in several instances some African populations were equally or more susceptible than the Guadeloupe population. Moreover, the relative level of susceptibility between African mosquito populations depended on the DENV strain, indicating genetically specific interactions. We conclude that unlike ZIKV susceptibility, there is no clear-cut dichotomy in DENV susceptibility between African and non-African Ae. aegypti. DENV susceptibility of African Ae. aegypti populations is highly heterogeneous and largely governed by the specific pairing of mosquito population and DENV strain. Author summaryAfrican populations of the mosquito Aedes aegypti are usually thought to be less likely to get infected by flaviviruses compared to Ae. aegypti mosquitoes found outside Africa. While this has been well-demonstrated for Zika virus, it is not clear if the same is true for dengue virus, which is the most common flavivirus in humans. Studying this is complicated by the strain diversity of dengue virus, including four main genetic types, potentially causing different interactions. In this study, we compared several mosquito populations and found that, in general, African mosquitoes were less likely to get infected by dengue virus compared to mosquitoes from outside Africa. However, in some cases, African mosquitoes were just as or even more likely to get infected. The specific strain of dengue virus also influenced how likely African mosquitoes were to get infected, showing that the relationship between African mosquitoes and dengue virus is complex.

microbiology↗

bioRxiv2023

Genetic variability and vector competence of Aedes aegypti populations from Kisumu and Busia Counties, Western Kenya, for Chikungunya and Zika viruses

Aedes aegypti is the primary vector of several arboviruses, including dengue virus (DENV), chikungunya virus (CHIKV), yellow fever virus (YFV), and Zika virus (ZIKV). This vector is widespread globally in tropical and subtropical areas, but also found in temperate areas. Kenya experienced its first chikungunya outbreaks in Lamu County in 2004 and later in Mandera: 2016, and Mombasa: 2017. While there is yet to be a report of Zika outbreaks in Kenya, sero-surveillance studies indicate low-level transmission of this virus in coastal and northern parts of the country. Despite the presence of Ae. aegypti in Kisumu and Busia counties in sufficient densities, and free movement of people between the coast and the two western Kenya counties, no outbreaks of either disease have been reported in these regions. To investigate this phenomenon, we collected Ae. aegypti mosquitoes from county headquarter towns near railway stations connecting the coast and western Kenya and reared them under controlled laboratory conditions. The mosquitoes were then assessed for genetic variability using CO1 genes as well as their efficiency to transmit viruses using Laboratory colonies (F1) of the field mosquitoes challenged with an infectious blood meal containing CHIKV and ZIKV. Genetic analysis revealed the presence of both Ae. aegypti subspecies, (Ae. aegypti aegypti [Aaa] and Ae. aegypti formosus [Aaf]) in the two western Kenya counties, with Aaf being dominant (19:8 for Kisumu samples and 25:6 for Busia samples). Additionally, pairwise comparison revealed minimal genetic differentiation (0.62%) between the study populations, with a high genetic variation (99.38%) observed within each population, indicating significant diversity within individual populations. Ae. aegypti populations from Kisumu and Busia counties exhibited competence for CHIKV, with infection, dissemination, and transmission rates of 55.2%, 85.5%, and 27.1% for Kisumu; and 57.8%, 71.8%, and 25% for Busia populations, respectively. There was no significant difference in vector competence between these two populations. Interestingly, neither population was competent for ZIKV. In conclusion, the data shows that the Ae. aegypti populations in the two cities were homogeneous. This could explain the observed similarity in vector competence for CHIKV and ZIKV. Author SummaryOur study investigated the genetic variability and vector competence of Ae. aegypti mosquito populations in Kisumu and Busia Counties to CHIKV and ZIKV; revealing the presence and even distribution of both Aaa and Aaf subspecies. We also found that the Ae. aegypti populations from the two counties were not genetically differentiated. Furthermore, our study revealed that the Ae. aegypti mosquitoes from Kisumu and Busia counties were competent for CHIKV but may be refractory to ZIKV infection. These findings highlight the importance of continued monitoring of Ae. aegypti populations and their potential for arboviral disease transmission in the region.

microbiology↗

bioRxiv2020

Climate and urbanization drive mosquito preference for humans

The majority of mosquito-borne illness is spread by a few mosquito species that have evolved to specialize in biting humans, yet the precise causes of this behavioral shift are poorly understood. We address this gap in the arboviral vector Aedes aegypti. We first characterize the behaviour of mosquitoes from 27 sites scattered across the species ancestral range in sub-Saharan Africa, revealing previously unrecognized diversity in female preference for human versus animal odor. We then use modelling to show that this diversity can be almost fully predicted by two ecological factors - dry season intensity and human population density. Finally we integrate this information with whole genome sequence data from 345 individual mosquitoes to identify a single underlying ancestry component linked to human preference, with genetic changes concentrated in a few key chromosomal regions. Our findings strongly suggest that human-biting in this important disease vector originally evolved as a by-product of breeding in human-stored water in areas where doing so provided the only means to survive the long, hot dry season. Our model also predicts that changes in human population density are likely to drive future mosquito evolution. Rapid urbanization may drive a shift to human-biting in many cities across Africa by 2050.

evolutionary biology↗