Determination of ceiling doses of Heligmosomoides bakeri infections in outbred albino mice: the maximum tolerated dose

Abstract

The maximum dose of Heligmosomoides bakeri that can be tolerated by outbred albino mice was determined. Due to the extensive works of the author of this study with Heligmosomoides bakeri infections in the outbred albino mice, researchers have often contacted him for guides in choosing safe working dose levels of the parasite. This study was conducted in order to be able to advise accurately such requests and making available such results by publication for easy and wide access. This was done in two separate experiments in which maximum infection levels of 1000 L3 and 4000 L3 respectively were used. In Experiment I all infected mice survived. However, in Experiment II, some mortalities occurred in mice infected with 2500 – 4000 L3 H. bakeri. Though only proportionate to a certain point, there was generally an increase dose increase faecal egg counts (FEC) and worm burden (WB) response pattern. Also observed was an increase dose increase in PCV and bodyweight decline. This is an indication that these parameters are dependent on the infection dose levels. This fact was supported by the high morbidity and high mortality rate that occured at higher doses. The results therefore suggest that adult mice up to 8 week-old can survive infection with 2000 L3 H. bakeri and below. The infection dose of 2000 L3 is therefore the ceiling dose of H. bakeri in such adult or older mice. Dose levels as high as 2500 L3 and above were lethal to the mice. In designing experiments with the H. bakeri-mouse model for the study of GI nematode parasites only doses of 2000 L3 and below should be considered. Infection doses of H. bakeri greatrer than 2000 L3 may lead to earlier death of the mice when enough data might not have been taken.