Yesterday Nature magazine published an article covering two Australian studies that showed the ability of Wolbachia pipientis bacteria to stop reproduction of dengue virus in mosquitoes, which could mean controlling the spread of dengue fever.
The strain of Wolbachia, called wMel, interrupts pathogen transmission within the insect without causing severe physical effects to the insect itself, making it a more environmentally safe candidate for dengue fever control efforts.
Dengue fever infects approximately 50 million people each year. With nearly half of the world’s population at risk of dengue infection, the lack of specific treatment or vaccine increase the severity of risk.
The dengue virus, part of the same family as West Nile virus and yellow fever, is mosquito born. Transmitted by the Aedes Aegypti mosquito, dengue is endemic in 100 different countries throughout the Americas, Asia and Africa, but it is concentrated in Asia-Pacific.
A mosquito becomes infected with dengue by feeding on the blood of an infected person and then transmits the virus to other people through subsequent blood feedings. A mosquito remains infected for the duration of its life and females can transmit the virus to her offspring.
Symptoms of dengue fever begin 1-4 days after infection and may last 3-10 days. Signs include high fever, pain behind the eyes, severe joint pain, rash and mild bleeding from the nose or hums. Symptoms of dengue hemorrhagic fever (DHF), a more severe (potentially fatal, if left untreated) form of the disease, include the above as well as difficulty breathing, persistent vomiting and internal bleeding.
As there is no treatment or vaccine yet, the Center for Disease Control and Prevention (CDC) recommends the use of painkillers, hydration, rest and consultation with a physician.
Current prevention methods are focused on eradicating breeding grounds for mosquitoes. Ideal egg-laying places include anything that captures rainwater, such as old tires, pet bowls, and containers for domestic water use. WHO also encourages use of insecticides in conjunction with monitoring to test mosquitoes’ vulnerability to the insecticide.
The virus has been spreading its geographic reach, partly due to increased urbanization and partly due to climate change. With increasing dengue threat comes an accelerated effort to combat and control the virus. In addition to studies on preventing the transmission of the virus, progress on vaccine development has been made.
Late last year, Sanofi Aventis’ dengue vaccine began phase III of clinical trials; the last step in clinical development before a vaccine candidate is submitted for review by regulatory authorities for market production. Phase III studies are being carried out in Mexico, Colombia, Honduras, Puerto Rico, Peru, Philippines, Vietnam, Singapore, Australia and Thailand.
Dengue is caused by one of four closely related viruses (DENV1, DENV2, DENV3, DENV4). The vaccine undergoing trials is a tetravalent vaccine, which means that it offers protection against these four viruses.