The rising challenge of vector-borne diseases
It’s an old story, except that it only seems to get worse with every passing year. And so it is this year too. The monsoon season has resulted in a spike in vector-borne diseases across the country even as there has been an equally worrying increase in off-season incidents.
In New Delhi, which was the epicentre of a chikungunya outbreak last year and a dengue outbreak the year before, at least 50 new cases of malaria have been reported in the past week alone, taking the total number of cases since January to 225, according to the city’s municipal corporations. Across the country, in Kerala, there have been more than 10,300 new dengue infections and the disease has claimed 21 lives this year. Tamil Nadu has reported 4,400 cases, followed by Karnataka with more than 2,100 cases. Swine flu is also on the rise: More than 600 people have already died and another 12,460 people have been infected this year. In comparison, there were only 1,786 infections and 265 swine flu deaths all of last year. Similarly, chikungunya, which reappeared in this country a little more than a decade ago, has shown no signs of abating. In just three years between 2014 and 2016, there has been a 300-400% increase in the incidence of chikungunya, according to data analysed by the Centre for Science and Environment (CSE).
Against this backdrop, the government last week released a national strategic plan for the elimination of malaria, and pledged to eradicate the vector-borne disease by 2027. This is a change from previous years, when the focus was on containing the disease, but achieving this lofty goal will depend on effective implementation and sustained commitment to the project. The government will also need to tackle the root causes of the problem, such as genetic changes in pathogens, insecticide and drug resistance, the challenges of poor urban planning.
Another area of concern is funding. Last year, the Central government released only 68% of budgeted funds under the national vector-borne disease control programme, and an even smaller percentage of that was actually utilized, according to the CSE’s State Of India’s Environment 2017. The lack of adequate healthcare workers who can carry out a prevention programme on a war footing is also a challenge. This includes not just field workers but also entomologists who can research all aspects of vector populations and recommend how these can be kept below the “critical mass”.
Finally, the prospects for vaccines against vector-borne diseases seem to be poor. In India, the International Centre for Genetic Engineering and Biotechnology has been working on a malaria vaccine for at least a decade but it is not ready for clinical trials yet. A dengue vaccine that is being used in about a dozen other countries is not yet allowed in India.
Fighting vector-borne diseases isn’t easy, least of all in a place like India that is a breeding ground for at least six major vector-borne diseases—malaria, dengue, chikungunya, filariasis, Japanese encephalitis and visceral leishmaniasis. As pathogens travel across continents and new strains continue to emerge, the fight against vector-borne diseases has, once again, become a global public health challenge.
From the 17th through the early 20th century, vector-borne diseases such as malaria, dengue, yellow fever, plague and typhus routinely wreak havoc on entire populations. And, according to Duane J. Gubler, an expert on tropical infectious diseases who headed the vector-borne infectious diseases division at the Center for Disease Control and Prevention in the US for 15 years, it was only after these diseases were brought under control, and in some cases eliminated, that public health could meaningfully improve,
However, as is evident today, those successes were short-lived. Since the 1970s, many of these diseases have resurfaced, with even greater intensity in recent decades. And while there are many different factors, local and global, that have contributed to the resurgence of each pathogen, Gubler lists two common factors that have impeded response strategies: 1) the diversion of financial support and subsequent loss of public health infrastructure, and 2) the reliance on quick-fix solutions such as insecticides and drugs.
In India, for example, the early success of the anti-malaria programme led to a certain amount of complacency. As P.K. Rajagopalan, a former director of the Vector Control Research Centre in Puducherry, writes, our health policy planners did not “foresee vector adaptation to chemical pressure”. A.P. Ray, the father of India’s relatively successful anti-malaria programme, “depended too much on the efficacy of DDT (dichloro-diphenyl-trichloroethane)” and assumed that “there would be no further need for entomologists in mosquito control work”—hence, researchers were moved to other tasks such as family planning, funds were diverted, and only a small field staff was engaged in DDT spraying. This, Rajagopalan argues, was a huge mistake: When malaria and other vector-borne diseases resurfaced, India was found unprepared. These are some important lessons from the past that India must keep in mind if it wants to mount a successful and sustained offensive against vector-borne diseases.
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