The Carter Center's assistance to river blindness control programs: establishing treatment objectives and goals for monitoring ivermectin delivery systems on two continents

Periodic mass treatment with ivermectin in endemic communities prevents eye and dermal disease due to onchocerciasis. As part of an international global partnership to control onchocerciasis, The Carter Center's Global 2000 River Blindness Program (GRBP) assists the ministries of health in ten countries to distribute ivermectin (Mectizan, donated by Merck & Co.). The GRBP priorities are to maximize ivermectin treatment coverage and related health education and training efforts, and to monitor progress through regular reporting of ivermectin treatments measured against annual treatment objectives and ultimate treatment goals (e.g., full coverage, which is defined as reaching all persons residing in at risk villages who are eligible for treatment). Since the GRBP began in 1996, more than 21.2 million ivermectin treatment encounters have been reported by assisted programs. In 1999, more than 6.6 million eligible persons at risk for onchocerciasis received treatment, which represented 96% of the 1999 annual treatment objective of 6.9 million, and 78% of the ultimate treatment goal in assisted areas.

Liver sonography in an area endemic for schistosomiasis haematobium

Through the use of portable ultrasonography, eight cases (2%) of periportal fibrosis were identified in a random sample of 400 subjects selected from a village with a high prevalence and morbidity due to schistosomiasis haematobium in the White Nile Province of Sudan. In contrast, 36 cases (15%) of fibrosis were seen in an area with a similar prevalence and morbidity due to schistosomiasis mansoni in the Gezira Managil region of Sudan. Although there was only one case of Schistosoma mansoni as determined by repeated stool examination of the entire sample population in the first village, the majority of those with fibrosis and age-matched controls showed serologic evidence of active S. mansoni infection. This led to the conclusion that the cases of periportal fibrosis seen in the White Nile Province are most probably due to S. mansoni rather than to S. haematobium.

Association of the therapeutic activity of praziquantel with the reversal of Symmers' fibrosis induced by Schistosoma mansoni

The impact of antischistosomal chemotherapy on the most important complication of intestinal schistosomiasis, Symmers' periportal fibrosis, has not been determined. Since abdominal ultrasonography has proven to be an effective tool in assessing the extent of Symmers' fibrosis in patients, we monitored the effect of chemotherapy, which involved the annual administration of praziquantel, on 48 Sudanese villagers having varying degrees of Symmers' fibrosis. Results indicate no significant differences in the fibrotic status of the 48 patients between 1986 and 1987, but test statistics (both the Wilcoxon signed rank test and Friedman's block/treatment test), indicated a significant decrease between the fibrotic status of the patients in 1986 and their fibrotic status in 1988 and 1989. Thus, after three years of therapy, 12 of the 48 patients no longer had detectable Symmers' fibrosis, while another 16 patients experienced a reduction in the amount of fibrosis in their livers. When coupled with our previous study, which demonstrated that annual treatment of children with praziquantel prevents the appearance of Symmers' fibrosis, it now appears that praziquantel may reverse this schistosomal-induced pathology.

Effect of antischistosomal chemotherapy on prevalence of Symmers' periportal fibrosis in Sudanese villages

Almost all mortality caused by Schistosoma mansoni is secondary to Symmers' periportal fibrosis of the liver which can now be diagnosed by ultrasonography. This study assessed the usefulness of ultrasonography in measuring the effect of chemotherapy on the prevalence of Symmers' periportal fibrosis in Sudanese villagers. The prevalence of Symmers' fibrosis in 318 randomly selected patients from two villages not receiving systemic antischistosomal chemotherapy was compared with that in 168 patients from a village where antischistosomal chemotherapy had been systematically applied since 1979. The prevalence of Symmers' fibrosis was two to three times lower among treated villagers, with an eight-fold difference for villagers aged 10-20 years.

Oxamniquine pharmacokinetics in hepatosplenic schistosomiasis in the Sudan

Oxamniquine pharmacokinetics were determined in five normal Sudanese subjects and nine Sudanese patients with advanced hepatosplenic schistosomiasis, given 1 g as a single oral dose. There were no significant differences in oxamniquine mean area under the plasma concentration time curve (AUC), plasma half life (T1/2), or time to reach peak concentration (Tmax). However, patients had a 19% lower mean AUC, a 36% higher T1/2, and a 23% increase in Tmax. The peak concentration (Cmax) was 36% lower in patients (P = 0.04). There was no correlation between disease severity and oxamniquine pharmacokinetic values. A significant correlation between oxamniquine AUC and T1/2 suggests that its elimination may be non-linear. The higher dosage requirements for oxamniquine in the Sudan are unlikely to be due to lower plasma concentrations amongst the Sudanese.

Metronidazole metabolism following oral benzoylmetronidazole suspension in children with giardiasis

A suspension of benzoylmetronidazole (6.4% w/v) was given orally at a dose of 15-25 ml, equivalent to 0.6-1 g metronidazole, once a day for three days to 11 children with giardiasis. Blood samples were collected after the first and third doses for analysis of plasma metronidazole and its main oxidative metabolite by high performance liquid chromatography. Peak metronidazole concentrations were 22.60 +/- 8.52 mg/l (mean +/- S.D.) after the first dose, and 30.22 +/- 10.06 mg/l after the third dose, occurring at 3.6 +/- 1.4 and 4.4 +/- 2.9 hours post-dose, respectively. Peak concentrations of the metabolite were 4.26 +/- 1.94 mg/l after the first dose and 7.96 +/- 3.63 mg/l after the third dose, occurring 7.2 +/- 1.6 and 9.1 +/- 3.3 h post-dose, respectively. Calculation of plasma metronidazole half-life and clearance values was not possible. This study shows that oral administration of metronidazole as its benzoyl ester slows the rate of metronidazole absorption, followed by sustained plasma concentrations and a prolonged elimination phase. Giardiasis does not appear to prevent metronidazole absorption. Concurrent giardiasis is unlikely to influence metronidazole therapy for systemic anaerobic infections.