Livestock skin odours assist scientists tame Rift Valley Fever

Scientists from the Centre of Insect Physiology and Ecology (Icipe), have identified skin odours found in livestock which the mosquitoes use to spread the deadly Rift Valley Fever, a discovery that will now assist them to timely predict the likelihood of an outbreak of the disease that  in the last outbreak cost the economy Sh2.1billion.

The skin odours, known as aldehydes are common in many animals, including sheep, goats, cows and donkeys. The odours, researchers say, would now help them trap the disease causing mosquitoes in a narrowed and specific way. Up until now the disease vectors were being detected by Centres for Disease Control (CDC) light traps that were baited with carbon dioxide. Their shortcomings however was that they targeted a wide array of mosquito species even the harmless ones, while also trapping non target insect species like moths and bettles. The CDC traps according to ICIPE could also not be relied upon especially when the mosquito population was low.

The researchers found that combining a blend of aldehydes with CDC carbon dioxide traps without the light bulb can increase the number of mosquitoes captured three times. The new trapping system is expected provide adequate numbers of mosquitoes for virus detection, and can improve prediction of potential outbreaks of the infection. “The findings by the icipe researchers contribute significantly towards resolving two key challenges in the control of RVF. The first challenge is the critical need for more effective tools for monitoring mosquito vectors distribution, through developing more efficient trapping systems. The second is the need to enhance the ability of national programmes to predict the likelihood of an outbreak of the disease, which would enable them to respond in a timely manner,” read part of the study published in the PLOS Neglected Tropical Diseases journal.

The discovery now brings relief to governments, policy makers and livestock owners who have traditionally been caught flatfooted especially after long rains when the disease strikes. In 2006 a Rift Valley fever outbreak struck in Kenya predominantly in North Eastern and Coast Province which had received heavy rain in months, causing floods and creating breeding grounds for mosquitoes, which spread the virus of the fever from infected livestock to humans. In two months the disease had claimed 75 lives and left 183 were infected.

The highest losses were, for livestock producers, loss of milk production caused by abortion, worth  up to Sh758 000 per camel producer, livestock traders losing upto Sh180,000 per trader in sales due to animal deaths, and butchers accruing losses of upto Sh1million in the first two months as a result of non deliveries of meat. International interventions including laboratories by CDC in the country helped develop a vaccine against the disease.  But industry players have been on high alert ever since. In January this year UN issued an alert on the likelihood of an outbreak of Rift Valley Fever in Kenya and neighbouring countries which it said if it struck would have devastating effect on economies and livelihoods.