Visceral leishmaniasis (VL) & cutaneous leishmaniasis (CL) are parasitic diseases transmitted to humans by the bite of sand flies. In VL, the parasite migrates to the internal organs such as liver, spleen and bone marrow. Signs and symptoms include fever, weight loss, mucosal ulcers, fatigue, anaemia and substantial swelling of the liver and spleen. VL if left untreated will almost always result in the death of the host. Meanwhile, CL is the most common form of leishmaniasis. It is a skin infection caused by a single-celled parasite that is also transmitted by sand fly bites and can cause facial disfigurement.
Both diseases tend to affect children under 5 years old in Southern Mediterranean countries. However, in Northern Mediterranean countries, VL is more prevalent and is often associated with HIV infections.
Precise figures are not available but reports suggest that between 36,000 and 65,000 cases of VL and CL combined occur in endemic Mediterranean countries each year. The European Union and World Health Organisation (WHO) recognise the significance of the health problem and have called for research to develop innovative tools to control the number of sand flies due to the lack of available vaccines. This approach is known as vector control.
"Vector Control for Visceral and Cutaneous Leishmaniasis" (VCVCL) is a three-year, €180,000 Marie Curie Fellowship programme which began in October 2008. The programme addresses the EU and WHO concerns by examining the potential for an alternative vector control strategy that targets the insects responsible for transmitting VL and CL. It is hoped that success may lead to new opportunities for sand fly control and thus reduced disease transmission.
Sex pheromones are secreted chemical factors that trigger an attraction response in members of the same sand fly species and lead to mating. Through laboratory and field-based behavioural and chemical studies, VCVCL focused on determining if sex pheromones are present in the sand flies that spread CL and VL and then determine if they have practical applications.
Interestingly, the same approach is being followed by the Keele University Research Group to develop sex pheromone based strategies for controlling the South American vector of VL. As the work on VCVCL was undertaken at Keele University, the benefits were obvious. On the one hand, the VCVCL team has significant skills in maintaining colonies, handling and understanding sand fly‘s behaviour. And on the other hand, the Keele group is well-versed in isolating, identifying and synthesizing insect sex pheromones and translating the results of bench research into practical outcomes. Working together effectively was thus of utmost importance.
“This research may lead to a new and environmentally benign method of controlling sand flies that transmit VL and CL in European and other countries,” says project coordinators Prof. Gordon Hamilton and the Dr. Elyes Zhioua. “We are hopeful that it will eventually lead to a significant reduction in disease transmission across the Mediterranean.”
And if the results are anything to go by, there is indeed potential that a new tool to reduce transmission may be available in the not too distant future. For the first time, there is “evidence” of sex pheromones in old world leishmania vectors.