No Way To Fight Dengue, Chikungunya


When thousands of patients are writhing in pain in the bed, the last thing they would like to see is two governments engaged in a blame game over whose callousness caused the epidemic. Delhi Health Minister Satyendar Jain is brazening it out, saying does not kill — in the face of evidence to the contrary in quite a few hospitals. His party, the AAP, is blaming the three municipal corporations for failing to fog all neighbourhoods in time. The BJP mayors are hitting back with radio advertisements, and one has absolutely no idea where Union Health Minister JP Nadda stands on the issue. Some doctors have issued a statement of the percentage of mortality from these diseases, which can, on the one hand, prevent panic but, on the other, make these medical practitioners come across as insensitive to the plight of the people.

But fogging is what they all believe must be done! Never mind that no municipality fogs your house; if, unfortunately, you left a window or door ajar, the insecticide would push all the mosquitoes from the nearby drains to safe havens underneath the pieces of furniture in your house. What brains our ruling class has got!

Actually, fogging kills only adult mosquitoes. The larvae stay unaffected by the insecticide-laden fog. They grow up into adults in a matter of a few days and then may turn the next vectors of dengue and chikungunya. Even adult mosquitoes not exposed directly to the fog survive the spray.

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Technically speaking, pyrethrum/pyrethrin is a naturally occurring botanical insecticide, but authorities across the world mostly use pyrethroids or permethrins, not wholly safe for humans, especially those with chemical sensitivity. The US Environment Protection Agency will bear us out on that.

Come to think of it, the AAP and BJP are arguably the most cyber-savvy parties in the country, and they cannot do a simple Google search to find out how countries across the world — including our less-resourced southern neighbour Sri Lanka — have systemically and successfully fought the mosquito menace. The logic is commonsensical. You cannot fight a disease by letting every generation of its vector be born and then chasing them in their hideouts. You need a plan to eliminate the population of unnecessary, disease-causing creatures. If mindless environmentalists protest, they must be told that not every living being is required for the sustenance of nature.

Biological insect control

The idea of elimination brings us first to the mosquito sterilisation programme. Funny as it may sound, nobody is proposing a human-like tubectomy [vasectomy is, anyway, not applicable because female, pregnant mosquitoes alone sting; the males feed on plant sap. The lady mosquito does not feed on blood either; the blood it sucks in nourishes the eggs in its ovary]. There are two ways of sterilising the mosquito population. One is called the Sterile Insect Technique (SIT) where sterile males released from laboratories compete with naturally fertile males for mating; success for the sterile males would mean the mating with females would produce no offspring. The other is a transgenic process where either the offspring produced is sterile or the females are rendered infertile, ensuring that there is no subsequent generation of mosquitoes.

The SIT, where the reproductive cells of targeted insects are subjected to irradiation, has not demonstrated success in dense insect populations, and its success has been observed not in the case of mosquitoes but in controlling fruit flies, tsetse flies, melon flies and screw-worm flies. For one, the irradiated males were rendered too weak in comparison with the wild, productive males to attract the females for mating and execute the act. The transgenic approach, on the other hand, has worked on mosquitoes. There are quite a few ways of doing it.

One of the transgenic methods involves making female mosquitoes unfit for reproduction. A DNA-cutting enzyme Cas9 is extracted from bacteria and guided to particular genes via designed RNA molecules. Cas9 and another gene editor TALEN (transcription activator-like effector nucleases) disrupt three highly active genes in the female mosquito’s ovary. If even two of these genes are affected, the female can no longer reproduce. This has been successfully experimented on Anopheles mosquitoes to control malaria in quite a few countries.

Then, the Bay of Bengal offers a source of cure. If transgenic Anopheles stephensi produces hetrolytic C-type lectin CEL-III from a sea cucumber called Cucumaria echinata found in that bay, it stops the development of the malaria parasite. The jargon used in this paragraph refers to a protein that is calcium-dependent. It acts on the mid-gut region of the mosquito, inhibiting the insect from carrying the parasite, which is a Plasmodium (P falciparum, P vivax, P ovale, P malariae or P knowlesi).

But Delhi is concerned with dengue and as of now. On previous occasions and now as well, several other cities and towns have been affected. So, what have other countries that faced these epidemics done to check the diseases? Since dengue can be more fatal, we deal with it first.

This article will not deal with issues that the civic and health authorities are already apprised of: social education programmes, cleaning stagnant water sources to deprive the vector mosquito of its natural habitat and treatment in hospitals. It focuses on the research and experimentation by labs.



Dengue is caused by one of the five serotypes of a single positive-stranded RNA virus of the family Flaviviridae and genus Flavivirus that the Aedis aegypti mosquito carries. Brazil, Mexico and Philippines have approved the use of a vaccine to prevent dengue. Since four of the five serotypes are affecting these countries, the challenge for them is to develop a vaccine that pre-empts all the four. The risk factor is that prevention from one serotype may lead to severe viral replication if attacked by any of the other three, causing either dengue hemorrhagic fever or dengue shock syndrome. The rates of success recorded by Sanofi-Pasteur in the Phase III trials of their lab in Lyon, France, are 50.3%, 42.3%, 74.0% and 77.7% respectively for the first, second, third and fourth serotypes. As of now, there is no news of India keeping in touch with the pharmaceutical company for regular updates.

It was heartening to find two Indian researchers Aruna Sampath and R Padmanabhan working on entry inhibitors to stop the virus from entering cells. There are also efforts in Australia to infect the vector mosquitoes with the Wolbachia genus, which will make them partially resistant to the dengue virus. But neither government nor media in India has so far assured the country or its capital city that better treatment of patients will be available in the future.

The scene at the hospitals and private clinics is worse. Even a rudimentary examination of the patient to ensure that the symptoms are of dengue and not of chikungunya, malaria, leptospirosis, viral haemorrhagic fever, typhoid fever, meningococcal disease, measles or influenza is not being done unless the person is so serious that he/she must be admitted to a hospital. Of course, carrying out these tests on a large scale is a prohibitive proposition, but there’s got to be a medical approach further to merely checking the pulse, blood pressure, seeking a blood report from a pathological lab and asking the patient to leave with some Paracetamol (acetaminophen) tablets and advice of generous fluid intake. These blood reports are inconclusive, merely giving indications of one of the diseases mentioned above. Typically, a doctor in Delhi is telling the patient that his symptoms are “dengue-like” or “-like”. The “like” in the phrase that psychs the patient shows how puzzled they are with the virus’s mutation.

Mercifully, the rate of fatality in dengue is low — at a maximum of 5% worldwide — but this could be an alarmingly high number in absolute terms in a thickly populated and largely ailing Delhi (more than 12,000 cases of dengue and have been reported this year from across the country, out of which more than 3,000 are from the capital city). Those who have died might well have had a previous occasion of affliction, with the relapse caused by a different serotype of the virus. But this consequence of contracting dengue for a second time is not being communicated to the people either.

Mercifully again, only some towns and cities have reported the outbreak or epidemic of dengue that is caused by stings of infected Aedes aegypti. In other countries of and Africa, a species of mosquito called Aedes albopictus is spreading the disease in villages. We know how scarcely resourced our villages are to be able to tackle it. From Southeast Asia, when this mosquito, also known as the Asian tiger mosquito, travelled to Australia and New Zealand, it could not establish a habitat due to entomological surveillance programmes of the harbours and airports of these countries. We have no such contingency plan even after the arrival of and Ebola from Africa; all that we had heard of back then was quarantining of suspects.

The virus of this disease, belonging to genus alphavirus and family Togaviridae, is transmitted to humans by the same mosquito species Aedes aegypti and Aedes albopictus. The rate of fatality is less than that in dengue — less than 0.1% — but fatality is not impossible, contrary to what Delhi’s health minister has asserted.

Death, though the gravest of worries, cannot be the people’s only concern. Some patients, for example, fear being inflicted with chronic arthralgia (long-term arthritis) or any rheumatological disease. Their C-reactive protein has shot up beyond the normal level of less than 5 mg/l, and the reports say it is an indicator of “rheumatoid arthritis, rheumatic fever, tissue injury or necrosis”.

How could the inhabitants of this region have avoided this outbreak? By fogging or by the use of mosquito repellents? So far in the last two months since the disease began making news, the residents of east Delhi, for example, have heard the fogging machine only twice in the vicinity. While an Internet search shows that repellents containing DEET, icaridin, p-menthane-3, 8-diol (a substance derived from the lemon eucalyptus tree) or IR3535 work, you can be absolutely sure that none of the brands from All Out to Good Knight to Mortein — liquids, coils or papers — works beyond chasing away the first generation of mosquitoes. The subsequent generations develop immunity to these repellents, swarming all over the people in gay abandon. An Australian consumer organisation actually conducted a test of repellent to find that the strongest of repellents are effective only for the first 2 hours, peaking in the first 30 to 60 minutes and then diminishing in effect.

Importantly, mosquito repellents have little or no effect on the mosquitoes carrying dengue and -carrying viruses that are active in the daytime. They work, for a limited time, only on nocturnal mosquitoes.

As in dengue, the vector can be infected with a wMel strain of Wolbachia so that it is rendered ineffective to carry the virus CHIKV, but no such initiative is being taken in India.

It is discomfiting that while the Sri Lankan authorities could target both the vector and the parasite in the case of malaria, eradicating the disease from the country to the WHO’s satisfaction, a richer India is still fogging around cluelessly. Can we take lessons from Brazil that is fighting the mosquito menace on a war footing? Emulating a richer Australia would be a far cry. If our governments are dumb, can’t our researchers try, like the French did, to develop a vaccine of chikungunya that would induce neutralising antibodies?

Needed, CDC-like communication

Finally, all the biochemical and microbiological names used in this article remind me also of a glaring vacuum in health education in India. Who is supposed to educate the people in bare minimum technicalities needed to save themselves? Who will tell, for example, whether All Out, Good Knight or Mortein contains DEET or IR3535, the most effective of repellents?

India does not have an authoritative CDC-like website that the United States has. The website of the Union Health Ministry is as lousy as that of any other sarkari website — while ironically ministers have been seeking pride in the launch of one portal after another for the last of years. If at all a directive is issued in the face of an outbreak or an epidemic, it is totally ad hoc. Disease mitigated, webpage gone! The next year when the disease revisits us, the authorities scramble to put in place fresh social advertisements in newspapers. There is no reliable, one-stop FAQ page in a government-authorised website for all diseases, or even for the most frequent ones.

Doctors may do what they can do based on what science has so far discovered as treatment and cure. The gravest lapse here is lack of information with India’s governments and absence of communication of whatever little information they have to the people at large. This is no way to govern a country.

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Surajit Dasgupta
Co-founder and Editor-in-Chief of Sirf News Surajit Dasgupta has been a science correspondent in The Statesman, senior editor in The Pioneer, special correspondent in Money Life, the first national affairs editor of Swarajya, executive editor of Hindusthan Samachar and desk head of MyNation