Controlling breeding is the way out
Chikungunya was first reported in 1952 when it caused an epidemic on the Makonde plateau in Tanzania. The disease was called chikungunya, which, in Makonde meant that which bends up, to describe the stooped posture caused by the arthritic symptoms of the disease. Since then, the disease has been reported from the Seychelles, Mauritius, Madagascar, the Comoros Islands, Malaysia, Cambodia, Vietnam, Myanmar, Sri Lanka, India, Pakistan, Indonesia and the Philippines. In Asia, the virus was first isolated in Bangkok in 1958. In India, chikungunya was detected for the first time in Kolkata in 1963. There were extensive outbreaks during 1964-1965 in south and central India. Maharashtra reported cases in 1973. The virus virtually disappeared for 33 years before resurfacing, again in Maharashtra, in 2005.
Though chikungunya has been around for over half a century, worldwide, little research has gone into it.who and the Indian Medical Association typify the attitude towards the disease both say it is not dangerous on the basis of sketchy evidence. Since the virus was first described, PubMed, a database of medical journals, shows just 547 entries on chikungunya. Compared to this, 744 reports have been put out on avian influenza during the last year.
India mirrors this state of ignorance and neglect. An nvbdcp report, for instance, said there was an epidemic resurgence of the disease in 2001-2003, but no one took note of it. The ongoing outbreak has finally shaken the establishment, but is not enough to pull out the stops to track and study it. The government is relying largely on information from the Runion Islands, which is also going through an epidemic that has claimed over 200 lives.
Only one sample is collected per 100 cases. Only two laboratories, those of niv and nicd, are carrying out the tests for the disease; between them they don't have the capacity to process the number of samples they receive. A total of 11,836 samples have been sent, but the labs have not been able to furnish results after months. In these circumstances, decent epidemiological studies are not possible. Even so, there are some clues about the resurgence of the disease and its rapid spread.
The Aedes aegypti mosquito, the main carrier, can only fly very short distances. This makes houses ideal breeding sites, giving it access to humans. Being a day-biter, it has a disturbed feeding pattern. The result is that the mosquito bites lots of people and, therefore, spreads viruses more widely. The mosquito feeds every second day and can transmit through its life cycle.
A number of studies generated by niv have thrown some light on chikungunya. nvbdcp unfortunately has not made much use of the findings. A 2004 study showed that high temperatures alter the susceptibility of adult Aedes aegypti mosquitoes to the chikungunya virus. So an increase in temperature above the normal average in an area leads to an increase in the proportion of mosquitoes that can carry the virus. In 2003, the institute reported that a parasite, Ascogregarina culicis, in the mosquito could have an important role in the maintenance of virus during inter-epidemic periods. The same year, they found that the Anopheles stephensi, found mostly in urban areas, could also transmit the virus. (In Runion, another species of mosquito, the Aedes albopictus, has also been found to be a carrier. Aedes albopictus is active outdoors, while Aedes aegypti typically feeds and rests indoors.In 2002, niv also published the results of a serological survey in the human population of the Andaman and Nicobar Islands, which showed the presence of the virus. The same year, it developed a rapid and simple test that could detect the virus in the carrier, which was a significant step forward for surveillance purposes. It can be completed in two days as compared to the 10 days taken by conventional techniques. The institute also found that during an outbreak of a dengue-like illness in eastern India, Aedes aegypti mosquitoes tested positive for the chikungunya virus. Evidence of dual dengue-chikungunya infection was also detected then.
It has also become clear that chikungunya spreads very easily, as the eggs can remain dormant for over a year. The lifespan of the mosquito is around 30 days and the virus takes around seven days to multiply in the mosquito. Since the mosquito passes on the virus through its eggs, prevention of breeding is the only way of controlling the disease.
One reason why the disease is spreading so quickly could be that people do not have immunity to the virus because it has not been around for a long time, says V Ravi, head, department of neurovirology, National Institute of Mental Health and Neuro Sciences, Bangalore. A serosurvey conducted at Kolkata around a decade ago showed that only 4.37 per cent of samples tested were positive for chikungunya antibodies, with the highest rates observed in the age group of 51-55 years and no chikungunya antibodies detected among the young and young adults. Given that the first group would have experienced earlier chikungunya outbreaks, the study lends credence to the view that infected people get lifelong immunity. But the latest outbreak seems to undermine this theory, given that many people are reported to have multiple relapses.
Studies on the mosquito, which spreads other diseases, have also shown that it started breeding in rural areas only after government water, supply reached these places. The logic of this development was that when governments started supplying water people were forced to store it for long periods. This gave the Aedes aegypti its ideal breeding habitat -- clean, stagnant water. In affected states, the government is asking people to empty all water containers and clean them regularly. But this is an impractical solution, given the reality of water scarcity and erratic supply.
Research has shown that water storage tanks contribute 90 per cent of breeding sites for the Aedes aegypti. Chemicals can be put in storage reservoirs to kill the larvae. But this is not a good method because it would require officials to treat every tank in affected areas -- a stupendous task. Moreover, people do not like chemicals in water. Making mosquito-proof tanks is the only way out, but there is no advocacy in this direction, say vector control specialists. Another problem is that mosquito control is now under the purview of panchayats but steps have not be taken to train people to identify the correct chemicals to buy and carry out the programme in a scientific manner.
But the issues of research and testing must be seen from the right perspective. Former nicd director K K Datta points out that monitoring and surveillance should take precedence and research bodies like niv should be actively involved in this endeavour to control the spread of the disease. niv could, however, argue with justice that it had carried out a study in Andhra Pradesh in December 2005 and warned the government that an epidemic could occur, but it was ignored.
State governments have launched somewhat belated campaigns to raise awareness about chikungunya. But the question is how aware is the official machinery about the disease. The answer is not terribly
Surveillance is also necessary to identify mutations that could make the virus more deadly. niv officials say the virus that has caused the epidemic this time seems to be different from the one that had caused earlier outbreaks. Studies are being planned to confirm this. Analysis of the outbreak in Runion has suggested that the increased severity of the disease may be due to a change in the virus's genetic sequence, which potentially allows it to multiply more easily in mosquito cells. In July 2006, a team in the island analysed the virus's rna and determined the genetic changes that have occurred in various strains of the virus and identified the genetic sequences that led to the increased virulence of recent strains.
The lack of surveillance is mirrored in the myopic responses of the government in the matter of treatment protocols. The government says there is no specific treatment for the disease and has prescribed paracetamol and painkillers. The Runion epidemic revealed, however, that chloroquin could be effective against the virus and there could be other more suitable drugs. Some districts in Karnataka use a certain amount of chloroquin. In the mid-1980s, the us Army Medical Research Institute of Infectious Diseases developed a vaccine. Though it was effective in trials, it is yet to be commercially made.
The point, however, is not whether drug A or B will be more effective. The question of medication is connected to surveillance and research. If the health establishment does not know what variant of the virus is causing the disease, it cannot possibly know what drug to administer, other than by accident. Relying on the Runion experience is not the best solution, since the island strain could be different.
But questions of treatment and research are overshadowed by the issue of prevention. The government just has not put into place the systems that will ensure that conditions are created in which mosquitoes are not allowed to breed. Vector management will take care of not just chikungunya, but a host of other diseases.
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