Bitew, M. | bioRxiv Science

bioRxiv2025

Distribution and association of biophysical factors with onion (Allium cepa L.) downy mildew (Peronospora destructor) disease epidemics in northwestern Ethiopia.

Onion (Allium cepa L.) is a significant food bulb crop that can be used for medicine, diverse recipes, and income. However, downy mildew disease limits productivity and production of onion in onion growing-regions. Thus, this survey was conducted to assess the distribution and intensity of onion downy mildew and determine the associations of disease parameters with biophysical factors. During the 2024/2025 onion cropping season, 130 onion fields were surveyed in order to measure biophysical and disease data. The associations of disease parameters and biophysical factors were analyzed using the binary logistic regression model by employing the SAS GENEMODE procedure. The surveys findings verified that downy mildew was 100% prevalent. The highest disease intensity was assessed from Fogera (50.68% and 23.48%) and Libokemkem (45.16% and 21.62%) districts, respectively. High disease incidence (>40%) and severity (>20%) were strongly associated with maturity crop growth stages, field size (>0.25 ha), blub previous crop, late October transplanting, less than four times fungicide application and less than three times land preparation. Lower disease incidence ([≤] 40%) and severity ([≤] 20%) had a strong association with early December transplanting, more than three times land preparation, fungicide spray (>4 times), field size ([≤] 0.25 ha), fields previously planted with cereals, could be considered as relative management options to minimize the diseases effects in onion growing areas of northwest Ethiopia and other similar onion cultivating areas. In addition, In order to develop effective management strategies, future research may examine pathogen variability.

pathology↗

bioRxiv2025

Identifying genomic surveillance gaps in Africa for the global public health response to West Nile Virus

BackgroundWest Nile Virus (WNV) is a zoonotic flavivirus of significant One Health relevance and is classified as a priority pathogen with a high-risk of causing public health emergencies of global concern. WNV is endemic to Africa; however, the availability of genomic sequences from the continent remains limited. MethodsWe review the extent of polymerase chain reaction testing and genomic sequencing of WNV conducted across Africa. Using phylogeographic methods, we map the spatiotemporal spread of the virus across the continent and globally. FindingsOur study shows that WNV has been detected in 39 African countries (including Comoros, Seychelles, and Mauritius), the Canary Islands, and Reunion Island. Publications including molecular data originate from 24 countries; however, genomic sequences are publicly available for only 16 countries. We identify regions with detected viral circulation but lacking molecular surveillance. Further, we list such regions that overlap with Key Biodiversity Areas (sites harbouring significant bird diversity) as they may host high viral circulation, and high human population density that may be susceptible to spillover. InterpretationWe recognise significant knowledge gaps on the true disease burden, molecular epidemiology, and distribution of WNV in Africa. Addressing these gaps requires an integrated One Health surveillance approach which is challenging to establish. We propose three key surveillance needs as potential starting points to improve our understanding of the virus in Africa to strengthen the global public health response to this disease. FundingRockefeller Foundation, the National Institute of Health USA, Institute of Human Virology Nigeria, Global Health EDCTP3 Joint Undertaking, the Health Emergency Preparedness and Response Umbrella Program, managed by the World Bank Group, the Medical Research Foundation, and the Wellcome Trust.

molecular biology↗