Related Experiment Videos
Investigations on female Onchocerca volvulus for the evaluation of drug trials
Abstract:
Females of O. volvulus show several typical morphological alterations during their ontogenesis. In order not to attribute such natural findings to the efficacy of drugs in drug trials female worms isolated from untreated patients in Liberia and Togo were examined by light microscopy. Local incrustations could be found regularly on the surface of the female parasite. Different inclusions are described which could often be found. They partially lead to degeneration and calcification. For the evaluation of ovocidal or embryocidal efficacy of drugs the developmental stages of 290 untreated female worms were quantitatively assessed, normal and pathologically altered forms were distinguished. Embryos were obviously not produced continuously but in intervalls of unknown length and frequency. Two third of the females contained embryos and microfilariae, one third showed eggs only or had empty uteri. The number of the developmental stages per female varied considerably. On the average more than 200,000 stages per female were found.
Insights
Morphological changes in female Onchocerca volvulus (O. volvulus) worms are natural, not drug-induced. This study examined untreated worms to establish baseline data for drug trials evaluating ovocidal efficacy.
Area of Science:
- Parasitology
- Helminthology
- Tropical Medicine
Background:
- Female Onchocerca volvulus (O. volvulus) exhibit natural morphological changes during development.
- Accurate assessment of antiparasitic drug efficacy requires distinguishing natural changes from drug-induced effects.
Purpose of the Study:
- To characterize the normal morphological alterations and developmental stages of untreated female O. volvulus.
- To establish baseline data for evaluating ovocidal and embryocidal drug efficacy in onchocerciasis treatment.
Main Methods:
- Light microscopy examination of female O. volvulus worms isolated from untreated patients in Liberia and Togo.
- Quantitative assessment of developmental stages (eggs, embryos, microfilariae) in 290 female worms.
- Distinguishing between normal and pathologically altered forms.
Main Results:
- Regular occurrence of local incrustations and various inclusions on the parasite surface, some leading to degeneration and calcification.
- Embryo production is intermittent, not continuous.
- Two-thirds of females contained embryos and microfilariae; one-third had only eggs or empty uteri.
- Average of over 200,000 developmental stages per female worm were observed.
Conclusions:
- Established baseline morphological and developmental characteristics of untreated female O. volvulus.
- Provides essential data to avoid misattributing natural parasite alterations to drug effects in clinical trials.
- Crucial for accurate evaluation of new onchocerciasis therapies.