Biology subjects

Snow, R. W.

Publications and source records attributed to Snow, R. W..

3 recordsLinked to original sources

bioRxiv2025

Ecological diversity of Anopheles gambiae s.l. and insecticide resistance across refugee camps in Kenya

Malaria remains a major threat during humanitarian crises, necessitating targeted vector control strategies informed by local vector dynamics. Between May and July 2023, we conducted larval surveys in refugee settlements across Dadaab, Kakuma, and Kalobeyei (Kenya), collecting Anopheles larvae. Genotyping of 728 specimens revealed spatial variations in species composition. Overall, Anopheles arabiensis was the dominant species (59%, n=426), followed by Anopheles coluzzii (35%, n=252), and Anopheles rufipes (1%, n=7). In Dadaab, An. arabiensis was overwhelmingly dominant (94%, n=352/374). In contrast, the Kakuma/Kalobeyei complex was characterized by the co-occurrence of An. coluzzii (72%, n=252/350) and An. arabiensis (22%, n=74/350), with An. rufipes exclusively found in Kalobeyei (7%, n=6/89) (Figure 2B). Notably, no members of the Anopheles funestus group or Anopheles stephensi were detected. However, approximately 5% of the larvae across the sites could not be resolved molecularly. High frequencies of the L1014F kdr mutation, a pyrethroid resistance marker, were detected in An. coluzzii (Kakuma: 50%; Kalobeyei: 63%) and An. arabiensis (Kakuma: 10%; Kalobeyei: 30%) populations in Turkana County. Interestingly, no kdr mutations were observed in the An. arabiensis population from Dadaab. These findings highlight significant spatial diversity in vector species composition and resistance profiles, with An. coluzzii emerging as a dominant, pyrethroid-resistant vector in the Kakuma/Kalobeyei complex. The results underscore the urgent need for targeted interventions, including resistance monitoring and alternative insecticide-based strategies, to mitigate malaria transmission risks in fragile, humanitarian settings. Further studies are warranted to address unidentified larval species and seasonal transmission dynamics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=125 SRC="FIGDIR/small/682237v1_fig2.gif" ALT="Figure 2"> View larger version (12K): org.highwire.dtl.DTLVardef@1f3788forg.highwire.dtl.DTLVardef@1701f58org.highwire.dtl.DTLVardef@19d566org.highwire.dtl.DTLVardef@95716_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 2.C_FLOATNO Species composition of Anopheles mosquitoes in Kakuma, Kalobeyei, and Dadaab refugee camps, Kenya. (A) Overall relative abundance of Anopheles species identified by PCR and ITS2 sequencing. (B) Spatial distribution and abundance of the predominant species, An. coluzzii and An. arabiensis, across individual sampling sites. C_FIG

ecology↗

bioRxiv2025

Malaria shaped human spatial organisation for the last 74 thousand years

The mechanisms driving the spatial organisation of early human societies in Africa are typically addressed through climate variables 1-3. However, genetic and archaeological studies have also suggested diseases as a major source of selection in the Pleistocene. Here, we explore whether P. falciparum-induced malaria, a major world disease, drove habitat choice in human societies between 74 and 5 thousand years ago (kya). Using species distribution models of three main mosquito complexes with palaeoclimatic reconstructions and combining the results with epidemiological information, we estimated an index of malaria transmission risk in sub-Saharan Africa through time. We then correlated it with an independent reconstruction of the human niche over the same time period and region. Our results show that humans strongly avoided or were unsuccessful in potential malaria hotspots. The effects of these choices shaped human demography for the last 74 kya, and likely much earlier, by fragmenting human societies over time and contributing to the formation of modern population structure. Our results highlight the importance of considering disease distributions when modelling estimates of past human demography, demonstrating that factors beyond climate underlay patterns of human habitat choice, exchange, and dispersal. Sentence summaryMalaria shaped human habitat choice, exchange, and dispersal since the late Pleistocene in sub-Saharan Africa.

evolutionary biology↗

bioRxiv2019

Evaluating the performance of malaria genomics for inferring changes in transmission intensity using transmission modelling

Advances in genetic sequencing and accompanying methodological approaches have resulted in pathogen genetics being used in the control of infectious diseases. To utilise these methodologies for malaria we first need to extend the methods to capture the complex interactions between parasites, human and vector hosts, and environment. Here we develop an individual-based transmission model to simulate malaria parasite genetics parameterised using estimated relationships between complexity of infection and age from 5 regions in Uganda and Kenya. We predict that cotransmission and superinfection contribute equally to within-host parasite genetic diversity at 11.5% PCR prevalence, above which superinfections dominate. Finally, we characterise the predictive power of six metrics of parasite genetics for detecting changes in transmission intensity, before grouping them in an ensemble statistical model. The best performing model successfully predicted malaria prevalence with mean absolute error of 0.055, suggesting genetic tools could be used for monitoring the impact of malaria interventions.

genetics↗