D. R. Bell

The chemotherapy of onchocerciasis. XII. The prediction of microfilarial loads in patients with onchocerciasis after treatment with diethylcarbamazine in northern Ghana.

This paper presents some statistical problems of analysing changes in patterns of microfilarial loads in onchocerciasis patients after chemotherapeutic treatment. Analyses are made of a pooled set of data from ten separate studies of diethylcarbamazine (DEC) conducted at the Onchocerciasis Chemotherapeutic Research Centre, Tamale, between 1978 and 1983. Regression models of microfilarial load at different intervals post-treatment are fitted with initial microfilarial load, total dose of DEC, duration of treatment and age of the patient as the independent variables. Appropriate transformations of the variables are chosen by examination of plots of residuals for violations of the assumptions underlying the regression models. A dose response curve for DEC is produced.

The chemotherapy of onchocerciasis. V. A standard method for the determination of microfilarial density in skin snips.

The microfilarial density in 400 skin snips from 100 patients was determined using the standard technique of the Onchocerciasis Chemotherapeutic Research Centre (OCRC method), the method used by the Onchocerciasis Control Programme (OCP method), and also after collagenase digestion. The OCRC method was fairly consistent and detected 84% of the total microfilariae. The OCP method gave a density which was consistently 20% less than the OCRC method, indicating that the increase in weight in skin snips following incubation in saline was fairly predictable. It is concluded that collagenase digestion is not worthwhile as a routine technique in chemotherapeutic trials, for which the OCRC method is recommended.

Schistosoma mansoni: activity responses in vitro to praziquantel.

SummaryThe effects of praziquantel, a novel antischistosomal compound, on the activity of adultSchistosoma mansoni (Liverpool strain) in vitro were investigated.Worm activity was modified at all concentrations of praziquantel. High concentrations (above 0.5 μg/ml) produced rapid paralysis, whilst low concentrations of praziquantel stimulated worm activity. It is concluded that such activity modification could lead to worm displacement in vivo.

Metrifonate in urinary schistosomiasis. A field trial in northern Nigeria.

A field trial of metrifonate in the form of Bilarcil tablets (Bayer) was carried out in 39 northern Nigerian schoolchildren heavily infected with Schistosoma haematobium. Three oral doses of 7.5 mg/kg were given at four-week intervals. The drug proved effective (mean reduction in egg counts eight weeks after completion of treatment 94.5%) and was excellently tolerated. Its use on a larger scale is suggested.

Activity of Schistosoma mansoni over a ten-hour period in vitro, and its modification by oxamniquine.

The activity of pairs of adult Schistosoma mansoni maintained in a continuous flow culture system was monitored for ten hours using the ultrasound method of Brown, Norman, Bell and Chavasse (1978). The results of 75 experiments were collated by computer to demonstrate the average effect of oxamniquine on worm activity in vitro at concentrations from 0.2 microgram/ml to saturation. The averaging technique indicates that oxamniquine concentrations down to 0.2 microgram/ml modify worm activity in vitro.

Schistosoma mansoni: ultrasonically detectable motor activity responses to 5-hydroxytryptamine in vitro.

The ultrasonic method compared favourably with other methods for monitoring schistosome motor activity in vitro, being able to detect and differentiate between the activity responses of Schistosoma mansoni to 5-hydroxytryptamine at concentrations down to 1 X (10(-6) M. This was taken to indicate suitable sensitivity for the application of the ultrasonic method to other drug studies.