J Mulema - The Scourge of Biological Invasions in Africa

Sub-Saharan Africa (SSA) is at crossroads especially from attack by invasive alien species (IAS) majorly facilitated by international trade, transport and travel. A multitude of IAS have significantly impacted
economies, livelihoods, and biodiversity in SSA. Examples include Bactrocera dorsalis and B. invadens (fruit flies), Eichhornia crassipes (Water hyacinth), Globodera rostochiensis and G. pallida (Potato cyst nematode), Maize Lethal Necrosis, Phthorimaea absoluta (tomato leaf miner), Pomacea canaliculate (apple snail), Prosopis juliflora (Mesquite), and Spodoptera frugiperda (fall armyworm). The preponderance of IAS in SSA is attributed to porosity of borders, weak border biosecurity, and lack of adequate information about likely invasions. While it may be unrealistic to address issues related to border porosity and biosecurity, availing adequate and timely information on the highest risk species enables planning and implementation of sustainable management options that
can avert some likely invasions. Such options include prevention through early detection, containment and eventual eradication where possible. Prevention is achieved through constricting pathways by reducing and
limiting the means of entry, intercepting movements at border points, and assessing risk of planned imports. Information about likely invasions can be obtained through strategic foresight, scenario planning, or horizon
scanning. Horizon scanning has been widely used and is defined as the systematic search for potential biological invasions and an assessment of their potential socio-economic impacts and potential impacts on biodiversity, considering possible opportunities for mitigating the impacts. Previously, horizon scanning was conducted through extensive review of published and grey literature however, CABI has developed a Horizon Scanning Tool which uses information available in the CABI Compendium to identify pests that have not been recorded in the “area at risk” (country or region of interest) but in areas that the country or region may trade with. The selected pests are subjected to a risk assessment process to prioritise the most important that may require further action. Such actions include establishing a pest risk register to continuously monitor change in risk,
updating lists of regulated pests, conducting detection and delimiting surveys to establish pest status and extent of spread respectively, conducting pest risk analysis to advise on import requirements, and research to provide key information necessary for decision making. Specific surveillance involves collection of pest samples and subjecting them to various diagnostic tests to confirm pest identity. Some of these include Polymerase Chain Reaction with approved diagnostic primers, biochemical tests, pathogenicity tests, DNA barcoding and metagenomic sequencing especially for viruses. The Horizon Scanning Tool has been used to select pests for risk assessment and eventual prioritisation for action in Burundi, Ghana, Kenya, South Africa, Uganda, and Zambia.
Following prioritisation, a process for pest risk management and communication can be instituted.