Needless to say, mosquitoes cause more human suffering than any other organism. Since time immemorial, millions of people have been dying due to the menacing activity of the moving bombshell that transmits some of the world’s worst life threatening and devastating diseases. Mosquitoes transmit many parasitic and viral diseases like Malaria, Dengue, Chikungunya, Filariasis, etc., that are on the rise in many tropical and sub-tropical countries.
Come summer and then rains, the terror unleashed by mosquitoes gets into full gear. Most disease carrying mosquitoes breed in stagnant fresh water. Majority of them breed in stagnant fresh water. The majority of them breed in various fresh water bodies like ponds and lakes, underground and overhead water tanks, under-construction buildings, unused wells and in abandoned tyres, empty cans, coconut shells, etc. It is, therefore, very important that preventive steps like inspection of fresh water bodies and other stagnant water containers, and anti-larval measures needed to be undertaken regularly during the rainy season inorder to check the onslaught of mosquito-borne diseases, particularly the dreaded Malaria – a dangerous and often difficult to manage disease caused by tiny parasite called ‘Plasmodium’.
According to available data, Malaria, an ancient and most devastating disease afflicting humanity, infects about 700 million people and killing more than a million each year, mainly in the wet tropical regions of the world such as Asia, Africa, Central and South America, where Malaria is rampant and people are brutally exposed to the compromised health conditions. Unfortunately, despite decades of international efforts, we are still not in a position to completely control such a minute creature having immense potential to create havoc worldwide.
It was in August 1867, that Dr. Ronald Ross (Nobel Prize winner for Physiology or Medicine in the year 1902), a renowned British army surgeon, began dissecting mosquitoes that fed on malarious patients. On 20 August, while dissecting a mosquito, he found many cells on the stomach wall of the mosquito and concluded that these were the Malaria parasite stages in the mosquito. This research was quite significant because until then, no one had any idea of how parasites in the blood of malarious patients were transmitted via mosquitoes. Hence, 20 August is commemorated as World Mosquito day.
Health experts say Malaria, which is preventable and curable, can be highly fatal if not treated properly. The term ‘malaria’ has its roots in the words ‘mal’ and ‘aria’ that mean ‘bad air’ in Italian. The malady can be cured by four different species of Plasmodium, the most deadly being Plasmodium Falciparum. The other three species are : P. Vivax, P. Malariae and P. Ovale that generally do not cause life-threatening disease. A fifth species, Plasmodium Knowlesi, causes malaria in monkeys but can also infect humans. The life cycle of malarial parasite involves two hosts – female mosquitoes of the ‘Anopheles’ genus are the primary host, while human beings are the secondary hosts. The disease raises its ugly head in human beings when an infected Anopheles mosquito bites a person and injects the infective stage of malarial parasites called ‘sporozoites’ into the blood stream. The parasites then embark upon their vicious journey to destroy the liver and blood cells of the host. This normally takes about one to three weeks from the day of the mosquito bite. The symptoms of illness start to appear in the victim only after the incubation period, which is quite variable and depends on the species of the infecting parasite as well as the health status of the victim prior to infection.
The cyclical occurrence of sudden chills followed by fever and sweating is repeated every two days in P. Vivax and P. Ovale infections, while it occurs every three days for P. Malariae. P. Falciparum can have recurrent fever every 36 to 48 hours or an almost continuous fever. A bout of Malaria may also typically cause yellowing of the skin and whites of the eyes due to destruction of Red Blood Corpuscles (RBCs) and liver cells. Besides causing severe anemia, Malaria causes cognitive impairment due to brain damage, especially in children. The worst hit are victims of P. Falciparum infection or cerebral malaria as they might develop bleeding problems, liver or kidney failure, seizures and even coma. This lethal assault by the malarial parasite kills the victim in most cases. Chronic malaria normally occurs in P. Vivax and P. Ovale infections, where the disease can relapse months or years after exposure, due to the presence of latent parasites in the liver. Malaria is commonly associated with poverty, but it is also a cause of poverty and a major hindrance to economic development.
In India, malaria is the number one killer among infectious diseases. The malady has staged a dramatic comeback after its near eradication in the early and mid-1960s. That is because prophylactic measures are still not economically viable, vaccines haven’t been developed as yet and currently available drugs that attempt to disrupt the metabolism of the parasite are beginning to slowly fail due to the bug’s continuously evolving resistance. It is obvious a completely different strategy is needed now. If no new measures to fight against mosquitoes are initiated, the number of malaria cases are predicted to double in the next 20 years.
As part of World Health Organization’s (WHO’s) global efforts to fight malaria, the Global Malaria Programme (GMP) envisages myriad activities that include malaria surveillance, monitoring and evaluation besides technical assistance and policy advice for integrating with national malaria programmes of different countries. Technical assistance at country level is also on diagnosis and treatment strategies, mosquito control including other preventive measures, besides supporting research for the development of new drugs and insecticides.
Among the new approaches being tried, under the supervision of the WHO, is to develop a transgenic mosquito (introduce into the mosquito a gene that interferes with the development of the malaria parasite). According to researchers, there are three basic requirements to achieve genetic modification of mosquitoes: (a) method to introduce foreign genes into the germ line (transformation), (b) the availability of a suitable promoter to drive the expression of foreign genes in the appropriate tissue and at the appropriate time; and ( c) the identification of appropriate gene products (effector genes) capable of interfering with the development of malaria parasite.
Researchers, however, say that several loose ends have to be tied up before we can expect to release transgenic insects to block human diseases. Integrated past management with conventional strategy as well as public awareness is highly indispensable to control the mosquito menace as of now, researchers emphasized.
(The writer is a freelance journalist)
