The epidemic you don’t know about

This story was selected by TOI Guest Editor Bill Gates.

NEW DELHI: It is now pretty certain. India will miss the target date of stamping out

elephantiasis

or lymphatic filariasis, one of two diseases that it was hoping to eliminate by 2020.

The national health policy had aimed at eliminating filariasis by 2015. The deadline was extended to 2017 and now has been shifted to 2020.

Filariasis, called hathipaon locally, can cause limbs, usually the leg, knee downwards, to swell enormously, or hydrocele (swelling of the scrotum), causing disfigurement and disability.

Transmitted through mosquito bite, filariasis is estimated to be endemic in over 250 districts in 20 states, putting 650 million people at risk.

Mass drug administration (MDA) in endemic districts ensuring coverage of over 65% population is the global strategy to eliminate the disease. It is caused by various coiled and thread-like parasitic worms.

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In India, 99.4% of the cases are caused by the species Wuchereria bancrofti with the other species Brugia malayi responsible for just 0.6%. The worms produce about 50,000 microfilariae (minute larvae) that enter a person’s blood stream — and get passed on when a mosquito bites an infected person.

Persons with microfilariae in their blood can appear healthy but are infectious. Those with chronic filarial swellings cannot further spread the infection. The larvae develop into adult worms that can live upto 5-8 years and more in humans. They damage the lymphatic system though no symptoms may show for years.

Since 2004, the health ministry has been carrying out mass drug administration as part of the Hathipaon Mukt Bharat (

Filaria Free India

) programme for preventive medication. This involves giving at least 65% of the population in endemic districts two drugs: tablets of diethylcarbamazine citrate (

DEC

) and albendazole once a year for five years. Children below two years, pregnant women and seriously-ill people are not eligible for these drugs.

After five years of MDA and 65% coverage, a transmission assessment survey is conducted to see if the district qualifies for stoppage of mass drug administration. India stopped the MDA in 96 of the 256 districts last year. But many of the 96 districts failed a treatment assessment survey by external evaluators.

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Another challenge is that the surveillance that identified the 256 endemic districts is now outdated. A fresh survey could push up the number of endemic districts to over 300. This would require an overhaul of programme strategy and consequently, the chances of meeting the 2020 target are slim. “It’s a challenge to get people to take as many as four tablets simultaneously, especially when they have no symptoms. Health workers must ensure the person consumes the tablets right then. This doesn’t always happen,” explained a senior official in the national filariasis elimination programme.

Since DEC is given by body weight, the rough calculation is about one DEC tablet for those between 2-5 years, two tablets for those aged 6-14 years and 3 tablets for adults or those above 15 years. This is in addition to the albendazole tablet.

The new three-drug combination, IDA, which involves adding tablets of Ivermectin to the DEC and albendazole tablets, has been shown to reduce microfilariae by 99% with the first dose itself. The two-drug regimen (DE and albendazole) reduces the disease by 60-80% and hence requires five rounds. The new drug regimen is expected to help clear the infection faster as IDA would require just two rounds.

But Ivermectin dosage is bodyweight dependent, which could mean adding 2-4 tablets to the existing drug regimen depending on the person’s body weight. That could be an additional challenge to the programme, the success of which hinges on community compliance (ensuring people take the medicine) and coverage (ensuring medicines reach at least 65% of the population).

Though WHO gives India albendazole free, it has to buy 70% of the required DE, 30% is free. Government will now have to find the funds to buy Ivermectin and meet the cost of expanding the programme. Budget approvals for the same are still in the pipeline.

Is this costing us medals in sports?
Are children being held back from excelling in sports because of the damage to their lymphatic system caused by the filarial worm? A study of 102 students in a filaria-endemic district in Odisha seems to suggest that is so and has also shown that treatment can reverse the damage.

For the study, children aged 5-18 in Odisha’s Khordha district were screened for filariasis caused by Wuchereria bancrofti — the species behind 99.4% of filaria infections in India. Though infection usually occurs early in childhood in endemic areas, the clinical signs appear later.

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The study looked for prevalence of damage to the lymphatic system in children who did not show any outward or clinical signs and tried to determine how well they responded to treatment. It tested the efficacy of DEC and albendazole once or twice a year in clearing the infection and reversing lymphatic damage.

It found that though changes to lymphatic vessels occurred early in the infection, treatment could reverse these in most cases.

“Of the children included in the study, 80% showed no symptoms but over 40% showed damaged lymphatic system. This indicates that it’s highly likely that these children won’t have the strength and stamina required to excel in sports,” explained a filariasis expert, adding that the study had strengthened evidence of the benefits of treatment even for children who showed no symptoms. He said treatment could boost chances of producing better sports people for the country.

The study was funded by the Bill and Melinda Gates Foundation and published in PLOS journal in October this year.

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