Mosquito-borne illnesses

mosquito pic

While the world focuses on Ebola, and rightfully so for many reasons, we must not forget about the other infectious diseases that are claiming lives everyday but may not be getting as much media coverage here in the US. The focus of this post is about some of the mosquito-borne illnesses that plague people around the world on a daily basis, in honor of World Mosquito Day that was Aug 20th.

Many efforts are under way to attempt to limit the mosquito populations that transmit these diseases, but we know that just spraying insecticide all over towns and the people living there may creative negative consequences that outweigh the positives.  Here is a link to a TED blog containing some great TED talks about innovative mosquito control efforts.

The newest mosquito-borne virus to catch some US media attention is Chikungunya. Chikungunya made it’s way into the Carribean in late 2013 and has now been found in many of the states of the US. Although only in Florida has it been locally-transmitted (meaning transmission from person-to-person via mosquitos in Florida) in at least 4 cases, the rest of the cases in the other states are a result of someone being infected abroad and coming back into the US where they are diagnosed. Efforts are underway to create a vaccine for Chikungunya and the vaccine has been shown to provide antibodies in the volunteer’s blood but more studies are needed on a larger sample size.

A common mosquito-borne virus in the US in West Nile Virus. The life cycle of WNV includes birds where some get sick and die but some birds are a reservoir for the virus but don’t show any signs of illness.

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Life cycle of West Nile virus

Because WNV can survive in birds it is hard to eradicate the disease by just controlling mosquito populations. Birds as a reservoir in combination with the increasing global temperatures and lower precipitation will result in WNV moving further north into previously unaffected areas, according to UCLA’s Center for Tropical Research.

Dengue virus is the cause of approximately 50 to 200 million dengue infections (aka breakbone fever) resulting in about 20,000 deaths annually. The WHO again classified dengue as “the most important mosquito-borne viral disease in the world” in 2012, due to it’s increasing spread into previously unaffected areas and the costly burden it places on people and countries. Tires may be the best example of how dengue is brought to new countries as water collected in the tires on shipping barges provide an optimal breeding ground for mosquitoes. There is a big concern that dengue could become endemic in the US and Europe as wherever the mosquito species that carry dengue can live, so can dengue. Work is being done to figure out both how to control the mosquito populations and also what potential there is for a vaccine.

Last but not least is the mosquito-borne virus is Malaria. Most of the more than 200 million annual cases of malaria occur in Africa and it is a leading cause of death of children.

Malaria life cycle in humans

Malaria life cycle in humans

Because people infected with the malaria parasite causes fevers, like Ebola, many of the people seeking hospital assistance for potential Ebola infections are more than likely infected with malaria. However, many cases of malaria will go untreated because health clinics have closed due to Ebola concerns and health workers are wary to draw blood to diagnose malaria in the midst of an Ebola epidemic. Because malaria is such a burden to people and countries creative efforts are underway to create vaccines for malaria.  However, the malaria life cycle is very complicated so it can be hard to control the parasite through traditional vaccine methods. We think of vaccines meant to protect people from disease, like polio and smallpox, but the transmisson-blocking-vaccine (TBV) would prevent mosquitoes from picking up the malaria parasite from an infected person, thereby preventing the mosquito from transporting the parasite to the next person it bites. It’s a novel way of looking at how to control the transmission of malaria but novel approaches are what is needed in the decades long fight against malaria.

What are other novel mosquito-borne illness control methods you have heard of?

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