Trevor Milner

Unfulfilled potential: using diethylcarbamazine-fortified salt to eliminate lymphatic filariasis

Fortifying salt with diethylcarbamazine (DEC) is a safe, low-cost and effective strategy to eliminate transmission of lymphatic filariasis. DEC-fortified salt has been used successfully in pilot projects in several countries and has been used operationally by China to eliminate lymphatic filariasis. The successful use of iodized salt to eliminate iodine-deficiency disorders is encouraging; similarly, fortified salt could be used as a vehicle to eliminate lymphatic filariasis. Despite the potential programmatic advantages of fortifying salt with DEC instead of undertaking mass administration of tablets, DEC-fortified salt remains an underutilized intervention. We discuss the reasons for this and suggest settings in which the use of DEC-fortified salt should be considered.

Una posibilidad desaprovechada: el uso de sal enriquecida con dietilcarbamazina para eliminar la filariasis linfática

Introduction Unbeknownst to many, a global effort is being undertaken to eliminate the parasitic disease colloquially known as elephantiasis. This little-known public health effort against lymphatic filariasis has achieved considerable momentum and successes, but is competing for scarce global funding. Approximately 80 million people in more than 75 countries harbour the transmission stages of Wuchereria bancrofti and Brugia malayi, the diseases causative agents. An additional 40 million people are affected by disfiguring damage to their limbs and genitalia, making the disease a leading cause of disability worldwide. (1,2) Interrupting transmission of the disease requires careful identification of endemic areas and the use of drugs designed to reduce microfilaraemia and break the transmission cycle. The mapping of areas endemic for W. bancrofti has been made easier with the use of a rapid antigen detection test. (3,4) The standard drug intervention has been simplified from a 12-day regimen, often directed at people with clinical disease, to mass drug administration for at-risk populations of a single annual dose of a two-drug regimen. (5) With the advent of these new diagnostic and therapeutic approaches as well as strategies to control morbidity, widespread interest has developed in eliminating these infections. As a result, the World Health Assembly called for the elimination of lymphatic filariasis to become a global public health goal. (5) Most endemic countries have now initiated or completed mapping, and more than 30 have established programmes that use albendazole and either ivermectin or diethylcarbamazine (DEC) for mass drug administration programmes. (6) The single greatest barrier to expanding elimination programmes to all at-risk people is financing. Although mass drug administration programmes have been successful in reducing microfilaraemia and providing important collateral de-worming benefits, elimination programmes are competing for scarce public health dollars. (7-9) Additional barriers to implementing filariasis elimination programmes based on mass drug administration include the difficulty of developing an infrastructure capable of distributing drugs to the entire at-risk population, the need to achieve and maintain high coverage levels for 5 years or more, and diminishing compliance over subsequent cycles of mass drug administration because of adverse reactions associated with the parasites death following treatment. (10,11) As discussed in greater detail below, salt fortified with DEC offers an alternative to mass drug administration and has the potential to overcome these obstacles; it could, in principle, eliminate filariasis faster and more cost-effectively than tablet-based programmes. (12-16) Despite its theoretical advantages, DEC-fortified salt has not been embraced by the lymphatic filariasis community as a public health intervention. Ironically, two major public health successes have also not received the public attention they deserve and they have direct relevance to the use of DEC-fortified salt. First, China, the country with the largest number of cases and largest population at risk, has eliminated transmission of the disease owing to, at least partly, the use of DEC-fortified salt. (17,18) Second, the salt industry has been mobilized on a country-by-country basis to increase the household use of iodized salt from low levels worldwide to more than 70% globally within the past 15 years; this has resulted in the likely elimination of cretinism, the most severe form of iodine deficiency, as well as a dramatic reduction in less severe iodine-deficiency disorders, and it has likely improved the IQ of millions of people. (19-21) These two successes highlight the importance of considering the contribution that salt containing DEC and iodine could make to the global effort to prevent lymphatic filariasis. DEC salt: the other intervention In 1967, at a time when lymphatic filariasis was being addressed primarily as a clinical problem by case identification and its standard treatment was a 12-day regimen, initial studies were done on using DEC-fortified salt to reduce microfilaraemia. …