[e-drug] Filariasis control: ethics, economics, and good science

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E-drug: Filariasis control: ethics, economics, and good science
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[Copied as fair use. KM]

Lancet 2001; 358: 246 (issue 9277, 21 July 2001)

Filariasis control: ethics, economics, and good science

Sir--Administration of a single annual dose of diethylcarbamazine
citrate to the population is already being done by many
less-developed countries for control of lymphatic filariasis. The
adoption of this control strategy is based on the observed reduction
in microfilariae prevalence or density after single annual
administration of diethylcarbamazine citrate for 2-5 
years.1

Scrutiny of these data reveals an important omission: a control
group of untreated microfilariae carriers has not been monitored to
find out whether the observed effect on decrease in density in the
treated group was not due to loss of circulating microfilariae during
the natural course of infection. Limited reports suggest that
microfilariae rate decreases quite substantially in carriers without
chemotherapy--26% in 1 year in Egypt,2 38% in 5 years in
Pondicherry,3 and 63% in 13 years in Orissa.4 The observed
decrease in microfilariae rate must be unequivocally a consequence
of administration of one annual dose of diethylcarbamazine citrate
in a given geographical area and be significantly more than the loss
of circulating microfilariae due to natural attrition over 4-5 years.

More interestingly, widespread and indiscriminate use of broad
spectrum antibiotics such as tetracycline and doxycycline in some
less-developed nations could also contribute to the observed
decrease in microfilariae density. These drugs compromise the
survival of filarial worms in mammalian hosts by eliminating
endosymbionts such as Wolbachia residing inside the worms, since
filarial parasites seem to be dependent on them for development as
well as embryogenesis. The need to include a control group is
further emphasised by this mechanism.

Although inclusion of an untreated group of microfilariae carriers is
clearly unethical, use of several million dollars on a control strategy
not based on good science could be perceived as equally unethical.
In view of the enormous cost involved in implementing nationwide
control programmes, the ethics, economics, and good science
involved in filariasis control programmes currently being pursued
should be debated. Analysis of even a small group of symptom-free
microfilariae carriers would assist in assessment of the cost-benefit
ratio of the current control programme.

Persistence of filarial infection after more than three decades of
biannual distribution of diethylcarbamazine citrate in a remote island
in French Polynesia5 clearly indicates that midcourse correction of
the filariasis control strategy would be inevitable.

Balachandran Ravindran
Division of Immunology, Regional Medical Research Center
Indian Council of Medical Research, Bhubaneswar 751 023, India
e-mail: balaravi@sancharnet.in

1. Mataika JU, Kimura E, Koroivueta J, Shimada M. Eficacy of five
   annual single doses of diethylcarbamazine for treatment of
   lymphatic filariasis in Fiji. Bull World Health Organ 1998; 76:
   575-79.
2. Weil GJ, Reda MRR, Setouhy MEL, Kandil AM, Ahmed ES, Faris
   R. A longitudinal study of bancroftian filariasis in the Nile delta
   of Egypt: baseline data and one-year follow-up. Am J Trop Med
   Hyg 1999; 61: 53-58.
3. Vanamail P, Subramanian S, Das PK, Pani SP, Rajagopalan PK.
   Estimation of fecundic life span of Wuchereria bancrofti from
   longitudinal study of human infection in an endemic area of
   Pondicherry (South India). Ind J Med Res 1990; 91: 293-97.
4. Satapathy AK, Sahoo PK, Babu Geddam JJ, Mohanty MC,
   Ravindran B. Human Bancroftian filariasis: loss of patent
   microfilaraemia is not associated with production of antibodies
   to microfilarial sheath. Parasitol Immunol 2001; 23: 163-67.
5. Esterre P, Plichart C, Sechan Y, Nguyen NL. The impact of 34
   years of massive DEC chemotherapy on Wuchereria bancrofti
   infection and transmission: the Maupiti cohort. Trop Med Int
   Health 2001; 6: 190-95.


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