In a letter published in this newspaper on Thursday captioned ‘It makes more sense trying to sort out the mosquito problems to eradicate filaria’, Dr Mark Devonish took the WHO to task over the method used in its campaign to eliminate filariasis from the country. The agency is currently running a series of advertisements in the local press explaining the rationale of its programme, and informing citizens about the drugs they are being asked to take.
Eradicating elephantiasis in particular, which is the form in which the public will recognise filariasis, will be welcomed by everyone, so a letter from a health professional suggesting that the WHO is doing the wrong thing to achieve that end could have a counter effect, dissuading citizens from complying with the request to take the drugs being administered. The problem is that laypersons are not in a position to judge whether there is merit in Dr Devonish’s assertions or not.
Dr Devonish first describes how a mosquito spreads filariasis by biting someone who is infected, and then transfers the worms in their lymphatic system to someone else by biting them. Anyone who is infected can be treated with filaricides to kill the worms. That, he writes, sorts the problem. However, he goes on to say that in Guyana, everyone is being given filaricides whether they are infected or not. He claims that this approach lacks medical evidence despite it being championed by the WHO. “No trials have been done on its effectiveness in eradicating filariasis,” he asseverates.
He goes on to explain how someone given filaricide tablets today may be protected for a day or two before the tablet is broken down and excreted. “What if a mosquito is to bite that person after the tablet is excreted?” he asks, and then provides his answer: “The fact is that they will get filariasis because the tablet is long gone out of their system. Common sense would dictate for this to be effective then all 800,000 population of Guyana have to get the filariasis tablet regime at the same time hence there may be a lag in potentially infected people.”
The doctor cites the WHO as arguing that a campaign over a six-year period can address this. However, he goes on to remark that the campaign has been going on worldwide since 2000 with little success in eradicating filariasis globally. He expressed doubt that such a strategy could be successful in developing countries “with struggling healthcare systems.”
Perhaps it could be remarked that the agency did experiment with putting filaricides in salt a few years ago, which was manufactured in Jamaica for Jamaicans and Guyanese. The experiment was not a success, possibly because here, at least, it was regarded with suspicion, and not enough people bought it.
Dr Devonish’s reservations notwithstanding, it should be noted that the WHO website itself does acknowledge that the filaricide tablets given locally have a “limited effect on adult parasites … [although they]… effectively reduce the density of microfilariae in the bloodstream and prevent the spread of parasites to mosquitoes.” (Microfilariae are immature larvae which grow into adults in a person’s lymphatic system and are what are transmitted by mosquitoes.)
In addition, the agency on its website says that at the start of its worldwide campaign, “81 countries were considered endemic for lymphatic filariasis. Further epidemiological data reviewed since, indicate that preventive chemotherapy was not required in 10 countries... The population requiring MDA [Mass Drug Administration] has declined by 36% (499 million) where infection prevalence has been reduced below elimination thresholds.” It then lists 14 countries as having achieved the elimination of lymphatic filariasis, while seven more are under surveillance to “demonstrate that elimination has been achieved.” It goes on to say that preventive MDA is still required in 52 countries.
Prima facie this would appear to cover some of Dr Devonish’s larger concerns, although whether in the kind of detail he would prefer is another matter. But he did raise another issue, and that was the side effects of the drugs used. To give one example, he writes that DEC can affect the heart and kidneys, and should not be used on heart patients or by pregnant and breastfeeding women. He asks whether the administrating personnel are really checking for these problems before the medicines are given.
Exactly what the extent of the danger of the drugs on certain categories of persons is, has not been made known to the public by the global health agency, although it may well be that the administering personnel have been given instructions about who should not receive doses. It is something that perhaps requires some clarification from the WHO.
As for Dr Devonish, his view – as the caption to his letter demonstrates – is that we should forget about taking on the disease, and deal with the mosquitoes. Well, we have been down this road before. It involves something more complex than just the WHO and the Ministry of Health doling out filaricides to the population. It will encompass central and local government agencies, require organisational and in some places, engineering skills, consistent monitoring and considerable sources of funding.
The last time that eradication was successfully achieved was after Dr Giglioli worked on the eradication of malaria from first, the coastland, and subsequently, the interior. The insecticide he used was DDT, which was sprayed on the canals and other water courses, as well as in houses in the interior. However, DDT acquired an unsavoury reputation and was banned worldwide, although recently there has been some suggestion it has stood wrongly accused. In addition, in Georgetown and its environs, at least, if not elsewhere, the Ministry of Health entered homes to check for stagnant water, while a more vigorous City Council than any we know nowadays managed the drains and trenches. In the rural areas, there were sophisticated drainage management arrangements that included the sugar industry. Exactly how all of that would be reproduced in this day and age is a mystery, although dealing with the drainage for all kinds of reasons is a desirable end in itself, as everyone knows.
Everyone would like to see the end of filariasis, and if the WHO’s method to eliminate it from our environment, indeed, from the global environment, is viable, then they should have our unqualified support. It is specialists in the scientific and medical fields who are best placed to know whether there is any substance at all to Dr Devonish’s statements; it is difficult for the public to decide when they lack the information to support their views. Clearly the WHO needs to answer the letter – albeit outside the context of their advertising campaign – responding to its contentions so citizens have a clear view of why it is necessary for them to cooperate.