Biology subjects

Masiga, D.

Publications and source records attributed to Masiga, D..

9 recordsLinked to original sources

bioRxiv2025

Anatomy and mechanics of tsetse fly blood feeding

African trypanosomiasis is a neglected tropical disease transmitted by tsetse flies (Glossina spp.) in sub-Saharan Africa. The flys saliva carries parasitic unicellular trypanosomes, such as Trypanosoma brucei, leading to infections in humans, domestic animals, and wildlife. Tsetse flies feed on a broad spectrum of hosts, including humans, elephants, buffaloes, rhinos, hippos, turtles and monitor lizards. To understand how the insects can penetrate such diverse skin types, we detailed the anatomical structures involved in tsetse blood feeding, their mechanical properties and the forces exerted by the fly during probing. We found that the tsetse flys feeding apparatus does not rely on exceptionally unique structures or extraordinary forces. Instead, the tsetse fly has evolved subtle yet highly efficient adaptations, which include a labellum equipped with arrays of small teeth. When combined with a robust retraction movement of the proboscis, these structures create lesions on various types of skin, thus facilitating blood pool feeding on a broad host spectrum.

biophysics↗

bioRxiv2025

Changes in the Anopheles arabiensis transcriptome and gut microbiota profiles associated with Microsporidia MB

Microsporidia MB is an endosymbiotic microbe found in Anopheles mosquito populations. This symbiont can block Plasmodium transmission in mosquitoes, and it can spread through mosquito populations and be sustained over generations by vertical and horizontal transmission. These characteristics make Microsporidia MB a potential candidate for symbiont-based malaria vector control. However, the mechanistic basis of interactions between Microsporidia MB and Anopheles arabiensis is poorly characterized. We investigated how the presence of Microsporidia MB affects transcriptomics profiles and the gut microbiota composition and diversity in non-blood-fed and blood-fed (24, 48 and 72 hours post blood meal) An. arabiensis mosquitoes. We observed that mosquito infection with Microsporidia MB upregulated farnesoic acid O-methyltransferase, a gene linked to juvenile hormone biosynthesis in the non-blood-fed mosquitoes. In addition, blood feeding in Microsporidia MB positive mosquitoes was associated with an activation of immune-related genes 24 hours after a blood meal, where several genes including the lipopolysaccharide tumor necrosis factor gene were upregulated. Interestingly, we also observed that Microsporidia MB positivity was associated with a microbiota shift to favor the proliferation of microbes including Pseudomonas and Serratia 24 hours post blood meal. There were indications of immune system activation in Microsporidia MB positive mosquitoes up to 48 hours after a blood meal where factors such as the peptidoglycan recognition SC2-like and lysozyme c-1 were upregulated. Notably, an upregulated immune system at this time point was associated with downregulation of genes associated with metabolism and the restoration of Serratia, Pseudomonas and other key microbes to relative abundances similar to those recorded in non-blood-fed mosquitoes. At the 72-hour time point, Microsporidia MB positive mosquitoes exhibited a downregulation of genes associated with immunity, including cecropins and defensins, while metabolic processes were predominantly upregulated. Our results provide insights into the effect of Microsporidia MB infection on the An. arabiensis gene expression and gut microbiota profiles. This work will contribute to mechanistic insights into symbiont-mediated malaria transmission blocking.

systems biology↗

bioRxiv2024

Biological tick control: modeling the potential impact of entomopathogenic fungi on the transmission of East Coast fever in cattle

Biological control of ticks using entomopathogenic fungi (EPF) is a highly desired alternative to chemical acaricides for the control of tick-borne pathogens. For Metarhizium anisopliae isolate ICIPE 7, one of these EPFs, efficacy against multiple tick species has been demonstrated in laboratory and field settings. However, we currently have little quantitative understanding of how EPFs can impact transmission. We developed a deterministic model of tick-host-pathogen interactions to explore how the effects of EPF on Rhipicephalus appendiculatus ticks may impact the transmission dynamics of East Coast fever (ECF) in cattle populations. We parameterized the multi-faceted effects of EPFs on tick dynamics using experimental data on Tickoff(R) biopesticide (a novel formulation of M. anisopliae ICIPE 7) and related EPFs. The epidemiological impact of EPF was evaluated across a range of product profiles and implementation strategies. Model results indicate that, for the explored product profiles, EPF derives most of its epidemiological impact through the delayed mortality effect. This EPF-induced mortality could not only reduce the onward Theileria parva transmission to cattle (both treated and untreated) but could also cause a reduction in the tick-to-host ratio and thus cattle exposure to ticks. The effects of EPF on reproduction fitness and engorgement of ticks elicit negligible impact. High levels of population coverage and treatment frequency are needed to reduce the tick population size and reach meaningful epidemiological impact in cattle populations. Additionally, increasing the persistence time of fungal conidia on cattle skin - through technological improvements to the EPF formulation - can substantially reduce acute infections when combined with appreciable population coverage levels, treatment frequency, and efficient spraying techniques. Our model analysis provides insights into the potential impact of EPF when deployed at a population level, and lends support to further research and development of this biological tick control tool.

microbiology↗

bioRxiv2024

Exploring the dynamic ticks-camel-pathogens interaction

The ability of ticks to interact and adapt to different ecologies and hosts determines their vectorial competence for various pathogens, however ticks-livestock-pathogens interaction studies are limited. With our ticks-hosts-pathogens interface studies, we found 14 species of ticks feeding on various livestock. Ticks showed a strong preference for one-humped camels (Camelus dromedarius). The camel nostril was the most preferred predilection site. The most prevalent tick species on camels was Hyalomma rufipes. We found two novel Amblyomma gemma variants which are distinct both morphologically and genetically from previously described Amblyomma gemma. The signature odors from camel breath and body were attractive to H. rufipes; demonstrating ticks utilize camel-derived metabolites to find their host. Our research shows that H. rufipes and camel hosts have unique and shared pathogens showing H. rufipes vector and camels reservoir host qualities. Our study unravels the dynamic interactions between ticks, pathogens, and camels that all influence the likelihood of pathogen adaptation and transmission dynamics. IMPORTANCETicks are obligatory hematophagous arachnids, serving as vectors for a wide array of pathogens that can be transmitted to animals and humans. The ability of ticks to acquire and transmit various pathogens depends on its attraction to quality reservoir host and the survival of the pathogens in ticks gut and other tissues. However, the complex dynamics of tick-pathogens interaction and host-seeking behavior remains understudied. This investigation revealed notable variation in tick preference for domestic animals, camel being the most preferred host. Moreover, our spatial analysis about tick attachment sites showed nostril is the most preferred sites by various tick species. Our epidemiology data showed variation in the pathogens harbored by camel (host) and vector (H. rufipes), demonstrating the camels efficiency as reservoir host and ticks vector competence for various pathogens. With our behavioral experiment using H. rufipes and its preferred hosts (camel) breath and body signature odors, we identified novel attractants for H. rufipes, thus offering new avenues for combating TBDs. Overall, our study presents novel insights into how multiple factors shape tick-host-pathogens interaction.

ecology↗

bioRxiv2024

Multimodal interactions in Stomoxys navigation reveals synergy between olfaction and vision.

Stomoxys flies exhibit an attraction towards objects that offer no rewards, such as traps and targets devoid of blood or nectar incentives. This behavior provides an opportunity to develop effective tools for vector control and monitoring. However, for these systems to be sustainable and eco-friendly, the visual cues used must be selective in attracting the target vector(s). In this study, we modified the existing blue Vavoua trap, originally designed to attract biting flies, to create a deceptive host attraction system specifically biased towards attracting Stomoxys. Our research reveals that Stomoxys flies are attracted to various colors, with red proving to be the most attractive and selective color for Stomoxys compared to other colors tested. Interestingly, our investigation on cattle-Stomoxys interaction demonstrates that Stomoxys flies do not have preference for a specific livestock fur color phenotype, despite variation in spectrum. To create a realistic sensory impression of the trap in the Stomoxys nervous system, we incorporated olfactory cues from livestock host odors that significantly increased trap catches. The optimized novel nanopolymer bead dispenser capable of effectively releasing the attractive odor, carvone + p-cresol, with strong plume strands, longevity. Overall, red trap baited with nano polymer beads dispenser is environmentally preferred.

ecology↗

bioRxiv2021

Transmission of Candidatus Anaplasma camelii to laboratory animals by camel-specific keds, Hippobosca camelina

Anaplasmosis, caused by infection with bacteria of the genus Anaplasma is an important veterinary and zoonotic disease. The characterization of transmission has concentrated on ticks and little is known about non-tick vectors of livestock anaplasmosis. This study investigated the presence of Anaplasma spp. in camels in northern Kenya and whether the hematophagous camel ked, Hippobosca camelina, acts as a vector. Camels (n = 976) and > 10,000 keds were sampled over a three-year study period and the presence of Anaplasma species was determined by PCR-based assays targeting the Anaplasmataceae 16S rRNA gene. Camels were infected by Candidatus Anaplasma camelii occurring from 63 - 78% during the dry (September 2017), wet (June-July 2018), and late wet seasons (July-August 2019). 10 - 29% of camel keds harbored Ca. Anaplasma camelii acquired from infected camels during blood feeding. We determined whether Anaplasma positive camel keds could transmit Ca. Anaplasma camelii to small laboratory animals via blood-feeding. We show competence in pathogen transmission and subsequent infection in mice and rabbits by both direct detection in blood smears and subsequent molecular identification by PCR. Transmission of Ca. Anaplasma camelii to mice (8 - 47%) and rabbits (25%) occurred readily after ked bites. Hence, we demonstrate, for the first time, the potential of H. camelina as a vector of anaplasmosis. This key finding provides the basis for establishing ked control programmes for improvement of livestock and human health. Author summaryHematophagous flies such as Tabanids and Stomoxys, among other biting flies, are mechanical transmitters of various pathogens such as African trypanosomes and Anaplasma species. However, little is known about the role of common camel-specific biting keds (also known as camel flies or louse flies, genus Hippobosca) in pathogen transmission. Keds inflict painful bites to access host blood, and in the process may transmit bacterial hemopathogens frequently detected in both camels and their keds. We confirmed by experimental blood-feeding, gene amplification, and amplicon sequencing that camel keds can transmit "Candidatus Anaplasma camelii" from naturally-infected camels to healthy mice and rabbits. The high prevalence of camel anaplasmosis throughout the year in northern Kenya could be explained by the infestation camel-specific H. camelina, whose capacity as efficient fliers, unlike ticks, promotes disease transmission and maintenance within and among camel herds. Although this study focused on the transmission of Anaplasma sp. by camel keds, it is possible that other hemopathogens could also be transmitted by these flies through a similar mechanism. Notably, in the absence of their preferred hosts, keds occasionally bite humans and other vertebrates they come across in order to acquire bloodmeals, and in the process could transmit zoonotic pathogens.

microbiology↗

bioRxiv2020

Repurposing the orphan drug nitisinone to control the transmission of African trypanosomiasis

Tsetse transmit African trypanosomiasis, which is a disease fatal to both humans and animals. A vaccine to protect against this disease does not exist so transmission control relies on eliminating tsetse populations. Although neurotoxic insecticides are the gold standard for insect control, they negatively impact the environment and reduce insect pollinator species. Here we present a promising, environment-friendly alternative that targets insect tyrosine metabolism pathway. A bloodmeal contains high levels of tyrosine, which is toxic to haematophagous insects if it is not degraded. RNAi silencing of either the first two enzymes in the tyrosine degradation pathway (TAT and HPPD) was lethal to tsetse. Furthermore, nitisinone (NTBC), an FDA-approved tyrosine catabolism inhibitor, killed tsetse regardless if the drug was orally or topically applied. However, it did not affect bumblebee survival. A mathematical model shows that NTBC could reduce the transmission of African trypanosomiasis in sub-Saharan Africa, thus accelerating current elimination programmes.

biochemistry↗

bioRxiv2019

Blood meal analysis of tsetse flies (Glossina pallidipes: Glossinidae) reveals a reduction in host fidelity when feeding on domestic compared to wild hosts

Changes in climate and land use can alter risk of transmission of parasites between domestic hosts and wildlife, particularly when mediated by vectors that can travel between populations. Here we focused on tsetse flies (genus Glossina), the cyclical vectors for both Human African Trypanosomiasis (HAT) and Animal African Trypanosomiasis (AAT). The aims of this study were to investigate: 1) the diversity of vertebrate hosts that flies fed on; 2) whether host feeding patterns varied in relation to type of hosts, tsetse feeding behaviour, site or tsetse age and sex; and 3) if there was a relationship between trypanosome detection and host feeding behaviours or host types. Sources of blood meals of Glossina pallidipes were identified by sequencing of the mitochondrial cytochrome b gene and analyzed in relationship with previously determined trypanosome detection in the same flies. In an area dominated by wildlife but with seasonal presence of livestock (Nguruman), 98% of tsetse fed on single wild host species, whereas in an area including a mixture of resident domesticated animals, humans and wildlife (Shimba Hills), 52% of flies fed on more than one host species. Multiple Correspondence Analysis revealed strong correlations between feeding pattern, host type and site but these were resolved along a different dimension than trypanosome status, sex and age of the flies. Our results suggest that individual G. pallidipes in interface areas may show higher feeding success on wild hosts when available but often feed on both wild and domesticated hosts. This illustrates the importance of G. pallidipes as a vector connecting the sylvatic and domestic cycles of African trypanosomes.

evolutionary biology↗

bioRxiv2019

The Glossina Genome Cluster: Comparative Genomic Analysis of the Vectors of African Trypanosomes

BackgroundTsetse flies (Glossina sp.) are the sole vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood specific diet by both sexes and obligate bacterial symbiosis. This work describes comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans (G.m. morsitans), G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes) and Fusca (G. brevipalpis) which represent different habitats, host preferences and vectorial capacity. ResultsGenomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex linked scaffolds show increased rates of female specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse specific genes are enriched in protease, odorant binding and helicase activities. Lactation associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other characterized insects. Vision associated Rhodopsin genes show conservation of motion detection/tracking functions and significant variance in the Rhodopsin detecting colors in the blue wavelength ranges. ConclusionsExpanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.

genomics↗