Assessing the WHO 50% prevalence threshold in school-aged children as indication for treatment of urogenital schistosomiasis in adults in central Nigeria.

Preventive chemotherapy with praziquantel is recommended in adults by the World Health Organization when prevalence of schistosomiasis in school-aged children (SAC) is ≥ 50%. This study ascertained the value of this threshold in predicting prevalence and intensity of Schistosoma hematobium (SH) infection in adults in central Nigeria. We evaluated urogenital schistosomiasis prevalence in 1,164 adults: 659 adults in 12 communities where mean hematuria among SAC in 2008 was 26.6% and 505 adults in 7 communities where the mean hematuria among SAC in 2008 was 70.4%. No statistically significant differences were found between the two groups of adults in prevalence of hematuria, prevalence of SH eggs, or intensity of infections. We conclude that, in this setting, the SAC threshold is not useful for treatment decisions in adults. Given the increased risk of subtle morbidity or urogenital schistosomiasis as a risk factor for human immunodeficiency virus (HIV), more liberal treatment of adults with praziquantel is warranted.

Epidemiological and entomological evaluations after six years or more of mass drug administration for lymphatic filariasis elimination in Nigeria.

The current strategy for interrupting transmission of lymphatic filariasis (LF) is annual mass drug administration (MDA), at good coverage, for 6 or more years. We describe our programmatic experience delivering the MDA combination of ivermectin and albendazole in Plateau and Nasarawa states in central Nigeria, where LF is caused by anopheline transmitted Wuchereria bancrofti. Baseline LF mapping using rapid blood antigen detection tests showed mean local government area (LGA) prevalence of 23% (range 4-62%). MDA was launched in 2000 and by 2003 had been scaled up to full geographic coverage in all 30 LGAs in the two states; over 26 million cumulative directly observed treatments were provided by community drug distributors over the intervention period. Reported treatment coverage for each round was ≥85% of the treatment eligible population of 3.7 million, although a population-based coverage survey in 2003 showed lower coverage (72.2%; 95% CI 65.5-79.0%). To determine impact on transmission, we monitored three LF infection parameters (microfilaremia, antigenemia, and mosquito infection) in 10 sentinel villages (SVs) serially. The last monitoring was done in 2009, when SVs had been treated for 7-10 years. Microfilaremia in 2009 decreased by 83% from baseline (from 4.9% to 0.8%); antigenemia by 67% (from 21.6% to 7.2%); mosquito infection rate (all larval stages) by 86% (from 3.1% to 0.4%); and mosquito infectivity rate (L3 stages) by 76% (from 1.3% to 0.3%). All changes were statistically significant. Results suggest that LF transmission has been interrupted in 5 of the 10 SVs, based on 2009 finding of microfilaremia ≥1% and/or L3 stages in mosquitoes. Four of the five SVs where transmission persists had baseline antigenemia prevalence of >25%. Longer or additional interventions (e.g., more frequent MDA treatments, insecticidal bed nets) should be considered for 'hot spots' where transmission is ongoing.

A pilot program of mass surgery weeks for treatment of hydrocele due to lymphatic filariasis in central Nigeria.

In a pilot program of mass surgery weeks (MSW) to provide hydrocelectomy services to men with filarial scrotal hydrocele, local general practitioners performed 425 surgical repairs in 301 men in five MSW in three rural Nigerian community hospitals between 2002 and 2005. The most common (94%) procedure used was the eversion technique, which was most familiar to the practitioners. Postoperative complications included hematoma (3.7%) and infection (3%), and there was one death from infection in an elderly man with previously unrecognized diabetes. In 115 patients (38%) followed for 1 to 3 years, the hydrocele recurrence rate was 7%. The eversion technique gives an acceptable outcome, and MSW are safe and effective if strict attention is paid to preoperative screening of candidates and asepsis.

Rapid assessment for lymphatic filariasis in central Nigeria: a comparison of the immunochromatographic card test and hydrocele rates in an area of high endemicity.

The rapid immunochromatographic card test (ICT) for Wuchereria bancrofti circulating filarial antigen is being used to map areas endemic for lymphatic filariasis. However, the ICT is expensive; thus, surveys based on this test must be relatively limited. Our study was conducted to determine if village-based hydrocele surveys could be used to supplement the ICT surveys in the mapping activities. We compared in 144 Nigerian villages the two assessment methods, ICT and examination for clinical hydrocele, in random samples of 30 adults selected using a procedure that obtained 15 younger males (reported age = 16-39 years old) and 15 older males (> or = 40 years), based on the assumption that hydrocele rates may be more prevalent in older age groups. The men were asked if they had scrotal swelling, then examined and tested by the ICT. We found a weakly positive correlation between village prevalence determined by the ICT and hydrocele (r = 0.041, P < 0.001). Only villages with hydrocele rates of 20% or greater were also consistently classified as having endemic filariasis by the ICT. There was no correlation between an individual's ICT positivity and clinical presence of hydrocele, and questioning about scrotal swelling was not predictive for presence of hydrocele. More research is needed to determine if community level hydrocele prevalence surveys can offer an economical and broadly applicable supplement to the ICT for determining the endemicity of filariasis.

Lymphatic filariasis elimination and schistosomiasis control in combination with onchocerciasis control in Nigeria.

This paper describes a pilot initiative to incorporate lymphatic filariasis (LF) elimination and urinary schistosomiasis (SH) control into a mature onchocerciasis control program based on community-directed ivermectin treatment in central Nigeria. In the same districts having onchocerciasis we found LF (as determined by blood antigen testing in adult males) in 90% of 149 villages with a mean prevalence of 22.4% (range 0-67%). Similarly, SH, as determined by dipstick reagent testing for blood in urine from school children, was found in 91% of 176 villages with a mean orevalence in school age children of 24.4% (range 0-87%). Health education and treatment interventions for SH resulted in 52,480 cumulative praziquantel treatments, and 159,555 combined onchocerciasis and LF treatments (with ivermectin and albendazole) as of the end of 2000. Treatments for onchocerciasis and LF were separated by at least 1 week from treatments for SH. There was no negative impact on the coverage of the onchocerciasis program by the addition of LF and SH activities.