Prolonged persistence of residualWuchereria bancroftiinfection after cessation of diethylcarbamazine-fortified salt programme

Abstract

SummaryA diethylcarbamazine (DEC)-fortified salt intervention programme was implemented between 1982 and 1986 in Karaikal district, Union territory of Pondicherry, south India, to control Culex transmitted bancroftian filariasis. The intervention reduced the microfilaria (Mf) rate from 4.49% to 0.08%. showed an overall Mf rate of 0.46% in the high-risk urban areas and 0.18% in the rural areas; none of the sampled children was positive for Ag. All detected Mf carriers were >20 years old. The age of the youngest Mf carrier was 30 years in urban and 21 years in rural areas, which suggests that transmission was interrupted and there was no incidence of new Mf case after cessation of DEC salt programme. Eleven of 15 urban and 15 of 17 villages were totally free from microfilaraemia. Nevertheless, three of 15 surveyed urban localities and two of 17 villages showed >1% Mf rate. Thus, it seems that (i) postintervention very low levels of microfilaraemia can continue as long as 20 years; (ii) 0.60-0.70% Mf rate is a safe level and at this level recrudescence of infection may not occur; (iii) there can be isolated localities with >1% Mf rate and their detection for further intervention measures could be challenging in larger control ⁄ elimination programmes and (iv) the residual infection mostly gets concentrated in the adult population, in underdeveloped urban areas and in historically highly endemic or large endemic rural areas. These groups and areas should be targeted with rigorous intervention measures such as mass drug administration to eliminate the residual infection.

Secondary Mapping of Lymphatic Filariasis in Haiti-Definition of Transmission Foci in Low-Prevalence Settings

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A Research Agenda for Helminth Diseases of Humans: The Problem of Helminthiases

“…Mathematical models predict, and experience confirms, that population coverage is a key determinant of the success of such programmes and that there remains a need to evaluate the compliance of the population participating in such programmes over the years. The use of the term “therapeutic coverage” implies that the persons who receive the drugs are actually taking them (i.e., they are compliant), but in several countries, most notably India, a gap between coverage and compliance has been observed in the case of LF [81], [82]. The contribution of non-compliant persons to transmission is unknown, but systematic non-compliance may represent a potential threat for helminth control or elimination.…”

Diurnally subperiodic filariasis in India—prospects of elimination: precept to action?

“…The results of these trials in India and elsewhere showed that microfilaria density dropped by more than 90% and that microfilariae disappeared from the blood in 31% to 98% of the infected population (Raghavan et al 1968;Sen et al 1974;Krishna Rao et al 1976;Katiyar et al 1977;Narasimham et al 1979;Krishna Rao et al 1980;Narasimham et al 1989). Ramaiah et al (2009) concluded from a study on the impact of DECfortified salt that residual infection was found to persist after cessation of intervention. However, 0.60-0.70% microfilaremia (mf) prevalence is a safe level with no recrudescence of infection, and rigorous interventions measures are required to eliminate the residual infection.…”