Needless to say, mosquitoes cause more human suffering than any other organism. Since time immemorial, millions of people have been suffering and even 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 mostly parasitic and viral infections that are on the rise in many tropical and sub-tropical regions of the world such as Asia, Africa, South America, et al. 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.
For long, we have been facing a constant onslaught of ‘Anopheles’ and ‘Culux’ genera of mosquitoes that are responsible for spreading Malaria and Filariasis, respectively. These ancient and most devastating diseases have been afflicting millions of people worldwide, each year. While Malaria – a dangerous and often difficult to manage disease is caused by tiny parasite called ‘Plasmodium’, Filariasis (commonly known as Filaria or Elephantiasis) – a disfiguring and disabling disease, usually acquired in childhood – is caused by thread-like nematode parasite called microfilariae. However, of late, the intensity of these diseases has been on a considerable decline due to sustained international efforts pushed by the World Health Organisation (WHO) in controlling breeding of Anopheles and Culex mosquitoes, since the 1970s.
But, in the last couple of decades or so, the world is increasingly witnessing a havoc created by ‘Aedes Aegypti’ species of mosquito that is responsible for transmission of a group of diseases, which include Yellow Fever, Dengue, Chikungunya and Zika. This species of mosquito usually bite during the day – peak time is usually early and late afternoon or evening hours. The spiraling crisis surrounding these diseases across the globe is attributed to decades of international policy failure to control breeding of Aedes Aegypti mosquito, besides inadequate sanitation facilities and compromised health care systems available to the masses. Those failures have allowed mosquito-borne infections to spread rapidly and create a significant threat to global health, according to the WHO.
Yellow Fever is an acute infectious tropical and sub-tropical disease, caused by a virus that infects humans, all species of monkeys and certain other small mammals. The transmission of this disease from person to person is mostly carried by the Aedes Aegypti mosquito. After the bite of the infected mosquito, there is an incubation period of several days while the virus multiplies within the body. The onset of symptoms is then abrupt, with headache, backache, rapidly rising fever, nausea and vomiting. Because the virus destroys liver cells, jaundice (yellowing of skin and eyes by disposition of bile pigment) is a common symptom in persons with yellow fever and is in fact responsible for the name of the disease. Death may occur six or seven days after onset of symptoms. The disease can be prevented through inoculation of live-virus vaccine, which produces active immunity without clinical illness.
Dengue, also called breakbone fever or dandy fever, is an acute infectious mosquito-borne hemorrhagic fever that temporarily is completely incapacitating but is rarely fatal. Besides fever, the disease is characterised by an extreme pain in and stiffness of the joints (hence the name ‘breakbone fever’). Dengue is caused by a virus and may occur in any region where the carrier mosquito (mostly Aedes Aegypti) breeds. The mosquito becomes infected only if it bites an infected individual (man and perhaps certain species of monkey) during the first three days of the victim’s illness, and then requires 8 to 11 days to incubate the virus before it is able to transmit the disease to another individual.
Chikungunya is an infection caused by RNA virus that belongs to the alphavirus, first described during an outbreak in South Tanzania in 1952. Besides humans, the virus may circulate within a number of animals, including birds and rodents. The disease does not often result in death, but the symptoms can be severe and disabling. and sometimes up to 10 days.
Zika is an acute infectious disease, which is spread through mosquito bite and leads to brain damage and death in fetuses. Birth defect microcephaly – babies born with abnormal small heads and brains – is caused after their mothers are infected with the virus. The virus, which also causes the rare but serious neurological disorder Guillain-Barre Syndrome, in which the immune system attacks the nervous system, is mainly spread by the Aedes Aegypti mosquito but has also been shown to transmit through sexual contact. Recently, a team of international researchers has found that Zika virus can live in the eye and there is a possibility that people could acquire the infection through contact with tears.
Recently, the WHO said that Zika is presently endemic in 70 countries, mostly in Latin America, the Caribbeans and Eastern Asia, where countless people are infected by the virus. In Brazil, the hardest-hit country, more than 1.5 million people have been infected with Zika, and nearly 1500 cases of microcephaly have been registered since the outbreak began last year. The Zika outbreak remains an international health emergency and while the virus continues to hit new countries, experts still are not sure how big the risk is that pregnant women who catch the virus will give birth to brain-damaged babies.
Fundamental in preventing all mosquito-borne diseases is said to be regular insecticidal spraying and fumigation around human habitation and destruction of breeding places of mosquito vectors, particularly in the wet tropical regions of the globe. According to experts, in temperate climate regions mosquito breeding ceases with the first freeze and most of the mosquito-borne infections are terminated until the next warm season; but in the moist tropics, the diseases are perpetual, and control must be both effective and prolonged to keep mosquito breeding below transmission level of the diseases.
(The writer is a freelance journalist)
