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The World’s Ongoing Struggle With Vector-Borne Disease

Posted on May 09, 2014 by Ailee Slater ()  | Tags: vector-borne disease, WHO, World Health Day, World Health Organization, malaria, dengue fever, insects and disease, mosquitoes and disease

Earlier last month, the World Health Organization (WHO) recognized World Health Day 2014. Each year, WHO chooses a different health care issues to address, and the focus this year was vector-borne diseases: ailments such as malaria and dengue fever that occur after coming into contact with an animal. 

Teeny tiny insects like mosquitoes and ticks are a very big deal when it comes to health: every year more than 1 billion people around the world acquire a vector-borne disease following an insect bite, and more than 1 million fatalities result. 

This year, WHO is emphasizing the fact that along with being extremely dangerous, vector-borne diseases are preventable as well. In the newly published WHO report entitled “A Global Brief on Vector-Borne Disease,” researchers point out that stopping vector diseases before they start is essential to improving global health care. Not only are many vector-borne viruses becoming resistant to current treatments, but some diseases (including dengue fever and chronic virus chikungunya) have no effective treatment or even vaccination in the first place – prevention through pest control is the only option. 

Disease-carrying insects can often be controlled using very simple measures – governments can encourage their citizens to sleep under mosquito nets, for example, and provide nets for families who can’t afford them. WHO recommends that bed nets be replaced every two to three years, and with help from international aid agencies, more and more nets are being provided to developing nations struggling to control vector-borne disease. 

Insecticides safe for indoor use are also important in controlling mosquitoes and other disease-carrying bugs inside the home. Many insecticides last for up to 12 months, and with support from public programs, families can limit their exposure to potentially fatal viruses by using a WHO-endorsed insecticide. However, quantity is key: indoor insecticides cannot effectively lower rates of vector-borne disease unless at least 80 percent of houses in the local community have been sprayed – a statistic that highlights the importance of government support in keeping residents healthy and vector-disease free. 

Of course, insecticides can also be of use outdoors. Aerial spraying helps control mosquitoes, sand flies, and black flies – but some environmentalists protest the widespread use of insecticides outdoors, saying that damage to people, animals and the local environment is far worse than the dangers of insects. 

Those who oppose insecticides argue that natural rather than chemical methods should be employed to control insect populations. One such technique is to encourage the use of water storage containers with tight lids, so that mosquitoes aren’t able to use those areas as breeding grounds. Provision of such water containers to rural communities, as well as education about how to prevent mosquitoes from laying their eggs nearby, could greatly reduce cases of malaria, dengue fever and other mosquito-related illnesses. 

Besides mosquitoes, the WHO Global Brief on Vector-Borne Diseases also calls for better methods of controlling pests such as freshwater snails (responsible for the intestinal disease schistosomiasis), ticks (which spread the bacteria that cause Lyme disease), and black flies (a small gnat responsible for transmitting Onchocerciasis, a skin and eye condition also known as river blindness). However, mosquitoes remain a major focus of global efforts to reduce vector-borne disease: they are responsible for the deaths of over 1 million people every year, carrying diseases such as malaria, dengue and yellow fever, Japanese encephalitis and chikungunya. 

Along with better public policy to eradicate disease-carrying bugs (or at least mitigate their effects), educational campaigns also have the potential to reduce vector-borne illnesses. WHO recommends that people living in at-risk areas take precautions to avoid insect bites, including using DEET repellents, wearing light-colored, long-sleeved clothing, and when possible staying inside after the sun goes down and insects are at their most active. 

WHO reports that the most widespread vector-borne disease in the world is schistosomiasis, a condition passed to humans through contact with freshwater snails – but if individuals can limit their exposure to infested water, the chances of contracting schistosomiasis decrease greatly. Schistosomiasis can also be controlled with preventative medication – children who take regular doses of the anti-parasite drug praziquantel are far less likely to develop schistosomiasis as adults. 

Other insect-borne diseases can also be prevented or treated through the use of pharmaceuticals. Japanese encephalitis, a viral illness causing brain inflammation and a fatality rate of more than 50 percent, can be avoided through vaccination. One initial vaccination and two follow-up booster shots are enough to protect a person for life from Japanese encephalitis. Unfortunately, the vaccine and follow-up shots are expensive, making them a good option for travelers but not effective enough at controlling the disease in developing countries without efficient or well-funded public health services. 

With its focus on vector-borne disease during World Health Day 2014, WHO has also called for countries to put more resources into entomological training – that is, developing programs in which residents can become skilled at the science of insects. More entomologists in countries struggling with vector-borne disease could lead to better disease surveillance, more effective insect control, and new solutions to limiting insects’ effect on human health. Researchers with WHO further point out that entomology training programs could be good for developing nations’ economies: vector-borne diseases take a huge toll on public health funds and the effectiveness of local work forces, and reducing those illnesses would be a boon for workplaces and the general economic market. What’s more, entomological training programs would increase employment opportunities, for both skilled teachers as well as new workers in the field. 

The World Health Organization ends its Global Brief with an important warning: that we must address the problem of insect-borne diseases now, before illnesses such as malaria can grow stronger and spread further. Already, problems such as drug-resistant viral strains and environmental changes due to urbanization have led to increasing cases of disease, and death, in many parts of the world. It’s not too late to fight vector-borne illnesses, but we certainly shouldn’t wait around to get started.  


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