A few months back, I attended a World Vaccine Congress which talked about creating vaccines to combat Malaria, Dengue and other diseases. The best thing I remembered throughout the congress was that every single researcher was spending millions upon millions of dollars to find ways in which to deliver the vaccine into the body, how to fight the body's immune system and to overcome rejection or immunity against the vaccine itself, because a vaccine is considered a foreign body and when it is introduced into the body, the body's defences will attack it and destroy it.
The main topic was how to combat Dengue and Malaria. It then went on to expand on this idea and work towards combatting all mosquito-borne diseases, which included Yellow-fever, Japanese encephalitis, West Nile and Chikungunya. Now, the thing that I couldn't understand was why these scientists/researchers were trying to strike at the disease instead of at the carriers, ie the mosquitoes. I may sound mean, but will it be such a bad idea to eradicate all species of mosquitoes on the planet? Or if not all, just the female mosquitoes?
The idea was so simplistic, it was just baffling to me why millions and millions of dollars were spent to prevent it when we could simply destroy it, saving millions of lives.
Here's a short overview on the main and most important 5 mosquito-borne diseases:
Dengue Fever
Do not confuse Dengue with Malaria. Unlike Malaria, which is caused by a parasite, Dengue is a disease caused by a 4 closely related virus serotypes of the genus Flavivirus, family Flaviviridae. Dengue is transmitted by the Aedes mosquitoes, specially the Aedes aegypti mosquito, that feeds during the day.
With Dengue fever, a vicious cycle occurs when a mosquito bites an infected person, then becomes infected, and bites others. Dengue fever is typically characterised by symptoms like severe headaches, fever, nausea and vomitting and pains in the joints or bones. Some may mistake Dengue fever for a bad case of the flu.
The treatment similarly is lots of rest and increase fluid intake to prevent dehydration. In some cases, your doctor may prescribe drugs to bring your fever down. Usually patients recover within 2 weeks. However, if a person who has had Dengue is reinfected again with another serotype of Dengue, hemorrhagic fever can set in and it might become incurable, leading to death.
Malaria
Malaria is a well known mosquito-borne illness caused mainly by the Plasmodium parasites, consisting of the following species, Plasmodium vivax, Plasmodium falciparum, Plasmodium ovalae, Plasmodium malariae. These parasites are transmitted by female Anopheles mosquitoes. The parasites multiply inside red blood cells
Symptoms include fever, chills, muscle aches, fatigue, nausea and vomiting. Patients with malaria may also mistake their symptoms for flu symptoms. Unfortunately if not treated, malaria can lead to other illnesses including anemia and jaundice.
Once bitten it may take several weeks before a patient begins exhibiting symptoms, thus this is one mosquito born illness that is difficult to diagnose. Malaria is most often associated with travelling to foreign countries with large populations of Aedes mosquitoes. Fortunately, there are many treatment choices for patients with malaria. There are also preventive treatments a patient can take. These include:
- Chloroquine - Travellers should consider taking this pill starting two weeks prior to travel and for four weeks after travel if going to malaria infested areas.
- Doxycycline - This treatment starts two days before departure and may be continued for up to 4 weeks upon return home.
Unfortunately malaria is a very severe and insidious disease. Even after recovering some patients may find that their symptoms return several months or years after treatment.
Interestingly Malaria was discovered by Sir Ronald Ross, who was working in Secunderabad in the early 19th century, and is one of the oldest recorded disease in the world in the 18th century. Italians associated it with "Bad Air" (Mal aria).
Malaria remains the world's most devastating human infection, with 300-500 million clinical cases and 3 million deaths every year.
Paul Muller received a Nobel prize for the discovery of Malaria in 1939.
West Nile Virus
West Nile is a viral disease of the family Flaviviridae. It mainly infects birds, but is known to infect humans, horses, dogs, cats, and many other mammals. The main route of human infection is through the bite of an infected mosquitoes.
A 2004 paper in Science found that Culex pipiens mosquitoes existed in two populations in Europe, one which bites birds and one which bites humans. In North America 40% of Culex pipiens were found to be hybrids of the two types which bite both birds and humans, providing a vector for West Nile virus. This is thought to provide an explanation of why the West Nile disease has spread more quickly in North America than Europe.
West Nile Virus has recently invaded the shores of the United States. The symptoms are also flu-like and may include muscle and joint aches and pains, headaches, rashes and fevers. At this time there is no cure for West Nile disease, though patients usually recover in one to several weeks. Some people are not affected as badly as others.
West Nile is particularly risky for those with compromised immune symptoms. Severe reactions to the disease may include paralysis and encephalitis.
Japanese Encephalitis
Japanese encephalitis virus is a virus from the family Flaviviridae. Domestic pigs and wild birds are reservoirs of the virus; transmission to humans may cause severe symptoms. It is associated with inflammation of the brain and hence termed encephalitis. This severe and potentially life-threatening disease and is the leading cause of viral encephalitis in Asia with 30-50,000 cases reported annually.
The virus is prevalent in many countries in Asia with epidemics breaking out every few years. The disease is very widespread in China, Sri Lanka, Philippines, Nepal, Indonesia & other countries in Southeast Asia.
One of the most important vectors of this disease is the mosquito Culex tritaeniorhynchus. This disease is most prevalent in Southeast Asia and the Far East.
The illness occurs in two forms - a primary form and a secondary form. The primary form of the disease is more serious, while the secondary form is more common. But because of the milder nature of secondary encephalitis, more cases of primary encephalitis are seen.
Chikungunya
Chikungunya virus is an insect-borne virus of the family Alphavirus, that is transmitted to humans by virus-carrying Aedes mosquitoes. It is usually a usually self-limiting condition due to a virus.
Chikungunya is a relatively rare viral fever that is caused by the bite of a common mosquito. Outbreaks have taken place in many tropical countries. Recently it has resurfaced in many parts of South India and Southeast Asia.
It causes high fever with joint pain and rashes on the body. Most of the symptoms of Chikungunya mimic Dengue fever and can sometimes be mistaken for Dengue if further blood tests are not performed to exclude Dengue first, before diagnosing it. At the same time, the pain associated with Chikungunya infection of the joints persists for weeks or months.
Protecting Yourself From Mosquito-Borne Diseases
While most of this information sounds pretty terrible (that's because it is) the good news is you can largely protect yourself from mosquito bites. While you may not be able to prevent every bite, you can reduce the risk for contracting a mosquito born illness.
Common preventive measures include:
- Using chemical repellants or insecticides to keep mosquitoes in your yard at bay.
- Use of a mosquito repellant containing DEET. There are family formulas that contain less DEET that are safe to use on young children.
- Wearing long pants and sleeves when out in mosquito infested areas. Mosquitoes are also more common at dusk, thus it is a good idea to wear long sleeved items and spray your clothes when out in this environment.
- Use of citronella candles and other natural insect repellants.
- Keep grass trimmed short to deter mosquitoes.
- Avoid allowing any water to stand for more than a day in your yard or around your house, as mosquitoes tend to breed in standing water.
You'll probably find a combination of these strategies works best to keep mosquitoes from harming you and your family.
After listing down the diseases caused by mosquitoes, the kind of problems they cause and the millions and billions of money spent to research either a treatment or a prevention, wouldn't it be easier and cheaper, to just eradicate mosquitoes off the face of this Earth?
What do you think?
