Biology subjects

Ochola-Oyier, L. I.

Publications and source records attributed to Ochola-Oyier, L. I..

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

Uncovering the genetic diversity of the malaria parasite antigen MSP2 across Sub-Saharan Africa

Genetic diversity in Plasmodium falciparum poses a significant challenge to malaria control and elimination. This is particularly important for developing fully efficacious vaccines, which should include valuable blood stage antigens. Several antigen candidates are highly diverse and require further understanding. We surveyed the genetic diversity of the highly polymorphic merozoite surface protein 2 (MSP2) in 2761 P. falciparum isolates collected across Sub-Saharan Africa. Using PCR-based genotyping and long-read sequencing, we identified extensive diversity among msp2 size variants and sequences. Some size variants were more prevalent than others across different geographical regions, transmission intensities, and time points. These variants comprised multiple unique sequences, of which several were geographically and temporally widespread. Our study reveals greater msp2 sequence diversity than previously known, while also identifying interesting similarities in sequence and gene length across Sub-Saharan Africa. These findings support the further exploration of common msp2 variants in relation to parasite virulence and vaccine development.

microbiology↗

bioRxiv2022

Validation of saline, PBS and a locally produced VTM at varying storage conditions to detect the SARS-CoV-2 virus by qRT-PCR

Coronavirus Disease-2019 tests require a Nasopharyngeal (NP) and/or Oropharyngeal (OP) specimen from the upper airway, from which virus RNA is extracted and detected through quantitative reverse transcription-Polymerase Chain Reaction (qRT-PCR). The viability of the virus is maintained after collection by storing the NP/OP swabs in Viral Transport Media (VTM). We evaluated the performance of four transport media: locally manufactured ("REVITAL") Viral Transport Media (RVTM), Standard Universal Transport Media (SUTM), PBS and 0.9% (w/v) NaCl (normal saline). We used laboratory cultured virus to evaluate: i) viral recovery and maintaining integrity at different time periods and temperatures; ii) stability in yielding detectable RNA consistently for all time points and conditions; and iii) their overall accuracy. Four vials of SARS-CoV-2 cultured virus (2 high and 2 low concentration samples) and 1 negative control sample were prepared for each media type (SUTM, RVTM, PBS and normal saline) and stored at the following temperatures, -80{degrees}C, 4{degrees}C, room temperature (25{degrees}C) and 37{degrees}C for 7 days. Viral Ribonucleic acid (RNA) extractions and qRT-PCR were done on the following days after inoculation with the cultured virus, days 1, 2, 3, 4 and 7 to assess virus stability and viral recovery. CT values fell over time at room temperature, but normal saline, PBS, RVTM and SUTM all showed comparable performance in maintaining virus integrity and stability allowing for the detection of SARS-CoV-2 viral RNA. Overall, this study demonstrated that normal saline, PBS and the locally manufactured VTM can be used for COVID-19 sample collection and testing, thus expanding the range of SARS-CoV-2 viral collection media.

molecular biology↗