Investigation of the global transportation ofCulicoidesbiting midges, vectors of livestock and equid arboviruses, from flower-packing plants in Kenya
Abstract
Background
In recent decades there has been a huge increase in the export of cut flowers from countries in Africa and elsewhere to European flower markets, with the vast majority first entering the Netherlands for local use or for export. Coincidentally, two significant livestock disease outbreaks caused by viruses associated with Africa or other tropical regions, were first detected in the Netherlands (bluetongue virus, BTV, 2006) and in western Germany about 200 km from the Netherlands border (Schmallenberg virus, SBV, 2011). This study aimed to determine whetherCulicoidesbiting midges, the vectors of BTV and SBV, are present within flower-packaging plants in East Africa, and therefore whetherCulicoidescould be unknowingly exported during the shipping of cut flowers.
Methods
Field sampling was undertaken at a flower-packaging facility in Kenya, East Africa. The facility undertook all stages of cut flower production from maintaining rootstock through to packaging and shipping to an airport for international export. Trapping was undertaken at each stage of production (rootstock, propagation, inside growing greenhouses, in the packing-house, inside cold-storage rooms, during transportation) using CDC Light Emitting Diode (LED) light traps. Hand-held aspirators were used to obtain individual insects directly from flowers and around composting sites, while emergence traps studied insect emergence from compost, leaf-litter and flowers discarded at quality control checkpoints.
Results
A maximum nightly catch of 269Culicoideswere identified on a half-acre smallholding, containing 15 ruminants and 40 birds, located 20 m from the nearest greenhouse. Greatest numbers ofCulicoideswere trapped at a pond (n =23) and leaf-litter compost site (n =19) within the curtilage of the flower-packaging plant. Of the seven greenhouses sampled, three hadCulicoidestrapped overnight (mean = 4, range: 1-9), and noCulicoideswere trapped in the propagation units. NoCulicoideswere trapped in the pack house, cold-store, or during transportation of the flowers to the airport for shipment. NoCulicoidesemerged from emergence traps or were trapped when aspirating directly from flowers.
Conclusions
This is the first study to investigate whetherCulicoidesare present within flower packaging plants in Africa. The results highlight that although present in small numbers both outside and within greenhouses, the presence ofCulicoidesdeclined with each stage of production. Therefore, the risk of exportingCulicoideswith packaged cut flowers is non-zero but likely very small.
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