Prevention Of Leishmaniasis Transmission Through Prevention Of Bites By Sand Flies

Main Category: Tropical Diseases
Also Included In: Infectious Diseases / Bacteria / Viruses
Article Date: 30 Mar 2007 - 13:00 PDT

email to a friend   printer friendly   opinions  

The forthcoming summer in the Middle East, South America, India and parts of Africa brings the swarms of sand flies that spread leishmaniasis, considered among one of deadly neglected tropical diseases of our time.

Phlebotomine sand flies are tiny (>3 mm in length), densely haired flies found throughout the world's tropical and subtropical regions. The female sand fly lays its eggs inside cracks in house walls, in rubbish, ruined buildings and in sandy or savannah areas where heat, humidity and organic matter promote their growth. Because a female sand fly can lay millions of eggs and because insect resistance to pesticides is increasing, eradication of sand flies to date has met with little success. There are 30 species of sand flies that are known to transmit leishmaniasis, a parasitic disease by a protozoan (Leishmania sp.) through the bite of the female sand fly. When the female sucks the blood from an infected individual, it takes in the protozoa which develop during a period of 4 to 25 days inside the sand fly. The infectious female sand fly will then take a blood meal from another person and the painful sting will inoculate the new victim with the Leishmania protozoa, thus completing the cycle.

Leishmaniasis occurs in several forms. In cutaneous leishmaniasis, the disease is expressed in the form of skin ulcers on the exposed parts of the body, such as the face and arms. These lesions leave the infected individual with as many as 200 ulcers causing permanent scarring, disability and social stigma. In mucocutaneous leishmaniasis, the disease leads to the destruction of mucous membranes of the mouth, nose and throat causing disfigurement and disability in the victim. The fatal form of this disease is visceral leishmaniasis or kala azar and is characterized by anemia, swelling of the spleen and liver, bouts of fever and weight loss. Death occurs in 100% of the cases within two years if no medical intervention is available. The World Health Organization (WHO) estimates that 350 million people in 88 countries are at risk. Each year, up to 12 million people are infected and about 2 million of these develop various forms of this disease. Just like malaria, the magnitude of human suffering caused by this disease is staggering. But compared to malaria, leishmaniasis remains a poorly studied insect borne disease.

Over 90% of leishmaniasis cases are found in Brazil, Sudan, Syria, Arabian Peninsula, Iran, Afghanistan and Iraq. In the city of Kabul in Afghanistan alone 67,500 people contracted this debilitating disease in 2004. After 20 years of war, Afghanistan's infrastructure and insect control programs were destroyed. The ruins of the country also became excellent breeding grounds for sand flies. Refugees returning from Pakistan, where sand flies are not endemic, have lost their immunity from sand fly bites while living in Pakistan. They become especially vulnerable to leishmaniasis because they have yet to build up sufficient immunity upon their return. The situation in Iraq is equally dismal as the 2003 war and the ongoing insurgency has disrupted the already worsening public health situation. Although the bite of the phlebotomine sand fly (Phlebotomus sergenti) is not fatal, the hundreds of bites a person receives at night not only produce painful lesions, but disfigurement. Women in particular, with their exposed faces, suffer the most since the scarring made the affected women to be become stigmatized and often forbidden to breast feed their children as a result.

While eradication is an important goal, the prolific nature of the insect population, its resistance to conventional repellents and pesticides and the environmental conditions in Afghanistan and Iraq pose challenge to current control measures, such as use of fine bed nets. However, people have difficulty breathing when inside the very fine mesh bed nets because of the hot weather. Without effective intervention, experts believe that the epidemic will spiral out of control. Since complete elimination of sand fly populations is highly unlikely, the prevention of transmission of leishmaniasis will depend on combination of ways to avoid contact with sand flies. This will include use of effective repellents, avoiding areas where there are sand flies, use of bed nets / protective clothing and area-wide protection. The most practical and least restrictive approach will be the use of repellents. However, conventional repellents, including DEET, had proven to be marginally effective in preventing sand flies from biting. The effectiveness is further affected by other environmental conditions--heat and wind action--that greatly diminish the repellent's efficacy.

Working on sand fly infested areas, Poseidon scientists compared the effectiveness of MR-08 (menthol propyleneglycol carbonate) and DEET. In human volunteers, the application of 20% DEET in a lotion provided less than 10 minutes of protection from bites. When MR-08 was used in the same lotion, the protection time, i.e. the duration of time between application and the time of first confirmed bite, was extended by greater than 200 minutes. "These new finding offers a practical method of preventing leishmaniasis transmission and reduce the discomfort and disfigurement associated with sand fly infestation. Use of MR-08 as a preventive step would help reduce the 12 million new cases of this disease," says Jonathan Matias, executive director of Poseidon Sciences. MR-08 is a GRAS (generally recognized as safe) chemical that is modified from naturally occurring menthol and used in the food and cosmetic industry today as a cooling agent. The sand fly repellent potential of MR-08 is orders of magnitude greater than the protection provided by DEET. More information about the biological actions of MR-08 is available at www.poseidonsciences.com/insect_control.html.

Poseidon Sciences Group is an R&D company engaged in developing alternative, eco-friendly technologies to replace the toxic systems now being used by industries in diverse areas of medicine, biocides and insect control. R&D Initiatives Program is designed to enable collaborations between Poseidon and industry/academia/governments to enable such technologies to be made available for worldwide use in the shortest possible opportunity.

Poseidon Sciences Group
122 East 42nd Street, Suite 1700
New York, NY 10168 USA
www.poseidonsciences.com

• Additional
• References
• Citations