Trichuris suis and Oesophagostomum dentatum show different sensitivity and accumulation of fenbendazole, albendazole and levamisole in vitro.
BACKGROUND
The single-dose benzimidazoles used against Trichuris trichiura infections in humans are not satisfactory. Likewise, the benzimidazole, fenbendazole, has varied efficacy against Trichuris suis whereas Oesophagostomum dentatum is highly sensitive to the drug. The reasons for low treatment efficacy of Trichuris spp. infections are not known.


METHODS
We studied the effect of fenbendazole, albendazole and levamisole on the motility of T. suis and O. dentatum and measured concentrations of the parent drug compounds and metabolites of the benzimidazoles within worms in vitro. The motility and concentrations of drug compounds within worms were compared between species and the maximum specific binding capacity (Bmax) of T. suis and O. dentatum towards the benzimidazoles was estimated. Comparisons of drug uptake in living and killed worms were made for both species.


RESULTS
The motility of T. suis was generally less decreased than the motility of O. dentatum when incubated in benzimidazoles, but was more decreased when incubated in levamisole. The Bmax were significantly lower for T. suis (106.6, and 612.7 pmol/mg dry worm tissue) than O. dentatum (395.2, 958.1 pmol/mg dry worm tissue) when incubated for 72 hours in fenbendazole and albendazole respectively. The total drug concentrations (pmol/mg dry worm tissue) were significantly lower within T. suis than O. dentatum whether killed or alive when incubated in all tested drugs (except in living worms exposed to fenbendazole). Relatively high proportions of the anthelmintic inactive metabolite fenbendazole sulphone was measured within T. suis (6-17.2%) as compared to O. dentatum (0.8-0.9%).


CONCLUSIONS
The general lower sensitivity of T. suis towards BZs in vitro seems to be related to a lower drug uptake. Furthermore, the relatively high occurrence of fenbendazole sulphone suggests a higher detoxifying capacity of T. suis as compared to O. dentatum.
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Tina V A
TV
Hansen
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Peter
P
Nejsum
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Christian
C
Friis
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Annette
A
Olsen
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Stig Milan
SM
Thamsborg
D015766:Albendazole / Q000378:metabolism*; D000818:Animals; D000871:Anthelmintics / Q000378:metabolism*; D005273:Fenbendazole / Q000378:metabolism*; D007978:Levamisole / Q000378:metabolism*; D008124:Locomotion / Q000187:drug effects; D009815:Oesophagostomum / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D016019:Survival Analysis; D014258:Trichuris / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
D000871:Anthelmintics; D007978:Levamisole; D005273:Fenbendazole; D015766:Albendazole