Do you know the deadliest animal on earth? The biggest killer of human being!!!
No, it’s not a shark, it’s not a lion, not even a snake. It’s a tiny arthropod – Mosquito which accounts for approx 725,000 deaths per year across the globe by transmitting diseases like malaria, dengue and chikungunya. I got an opportunity to learn a great deal about this deadly animal while working with my NGO Malaria Consortium for last two months. I thought it would be nice to write a blog on this tiny deadly insect and to share different tools and techniques that can be used to prevent and control mosquito borne diseases.
Mosquito borne diseases are more common in tropics as this part of the earth provides suitable climatic factors such as temperature, humidity, and rainfall for mosquitoes to survive and multiply.
Mosquito vectored diseases include protozoan diseases, i.e., malaria, filarial diseases such as dog heartworm, and viruses such as dengue, encephalitis and yellow fever.
Malaria and Dengue are two of the commonest mosquito borne diseases which are endemic in certain parts of the world. It would be interesting to know few differences between Malaria and Dengue
1. Although both these diseases are prevalent in tropics, the dengue fever is more prevalent in the urban areas than malaria.
2. Malaria is caused by parasitic protozoa (Plasmodium) whereas Dengue is caused by virus.
3. Both organisms are spread through mosquito bites although the species are different in each disease. Thus, the dengue virus spread through Aedes mosquito while the malaria is spread through Anopheles.
4. The biting habits of these mosquitoes also vary and the Aedes (Dengue Mosquito) bites during the day time especially in the morning and late afternoon whereas Anopheles bites all night, but mostly between 11pm and 5am.
5. In treating malaria, the mainstay of treatment is the use of anti malarial drugs whereas in dengue, there is no such specific drug and the mainstay of treatment is supportive measures with fluid resuscitation and at times blood transfusion as well.
All in all, both malaria and dengue would be considered as life threatening illnesses in its own right requiring close monitoring. Early intervention in both instances is critical to avoid complications.
Now that you briefly understood about the disease, so now let us look at the ways to control the spread of Malaria/Dengue
1. Mosquito Nets – Using mosquito nets is one of the most effective ways to avoid a mosquito bite. These days ITN (Insecticidal Treated Nets) and LLIN (Long Lasting Insecticidal Nets) are also available and highly recommended in malaria prone areas. The mosquitoes that land on the net are prevented from biting the person sleeping under the net, and mosquitoes often avoid landing on the net altogether. But for Dengue prevention, Mosquito nets are not that effective as Aedes mosquito would bite in day time when nets aren’t in use.
2. Biological control: Larvivorous fish or Mosquito fish reduces larval mosquito populations. Some countries have established programmes for distributing these small fish to residents. Small Guppy fishes are placed in water containers to devour mosquito larvae
3. Source reduction: Source reduction is particularly useful for vector species, such as Anopheles stephensi, that often breed in man-made containers like water tanks and at construction sites.
4. Drug treatment of malaria patients: People with malaria have parasite in their blood. If they are treated with appropriate drugs, the parasite disappears from their blood helping to reduce the transmission of malaria.
5. Use of insect repellents: Recommended for frequent travelers or for those who are likely to travel in malarious areas.
6. Use of mosquito mats, coils and vaporizers: This is similar to the use of repellents. Some people may be allergic to the smoke that these devices emit, and for some, these devices are too expensive.
7. Screening: Put screens on windows and doors. Screening is a useful tool which helps in reducing the number of mosquitoes entering and leaving the building
8. Residual treatment of interior walls: In many instances, malaria mosquitoes rest on the walls before or after biting people. Residual treatment of the walls inside a house repels or kills the mosquitoes.
9. Vector Biology and Control – Some of the most interesting recent vector biology and control research uses Geographic Information Systems (GIS) and Global Positioning System (GPS) data to analyze distribution and abundance of malaria vectors. This data can be used at both local and national levels to target malaria vector control efforts appropriately and utilize resources effectively.
10. What About a Vaccine – As of now there are no vaccines available for Malaria and Dengue. Because malaria is caused by a protozoan, there are some difficulties in developing an effective malaria vaccine. But good news is that GSK pharmaceuticals has recently filed for its Malaria Vaccine RTS,S with regulators. Sanofi Pasteur has also in a press release said that its Dengue Vaccine candidate successfully completed final landmark Phase III Clinical Efficacy Study. Very soon we may have an effective vaccine for Malaria and Dengue.
11. EMR (Electronic mosquito repellant) : EMR’s have not been found very effective in preventing mosquito bite. This also includes various apps available on smart phones. So don’t rely on these.
12. Clothing: When outdoors near woodlands and areas with tall grass, wear long sleeves and socks if possible. Keep fabrics looser, too, because some mosquitoes can bite through tighter-fitting clothing
13. Wear Bright colors: Dark clothing attracts mosquitoes, so wear bright-colored clothing when spending time outdoors.
14. Genetically Modified (GM) Mosquitoes: Now biotech firm Oxitec of Oxford, UK, has genetically engineered males of the species Aedes aegypti so that their offspring die before reaching maturity. Oxitec’s mosquito-suppression solution consists of releasing the modified male mosquitoes into the wild—male mosquitoes don’t bite; it’s the females who do. The Oxitec males mate with female mosquitoes and create offspring that also have the lethal gene. Without the supplement, those offspring die.
Some of the strategies mentioned above are appropriate for individuals, while others are very useful on an area-wide or country-wide basis.
Hope you enjoyed reading this article.
Disclaimer: I am not an Expert on Mosquito Borne disease. I have just tried to put things together which I have learnt in last two months.