HYMENOLEPIS-DIMINUTA - LACK OF PATHOGENICITY IN HEALTHY RAT HOST

Whether H. diminuta (Cestoda: Cyclophyllidea) might affect adversely the growth of its host under normal conditions was studied. Rats were divided into 4 experimental groups: (1) rats infected with the tapeworm and fed ad lib, (2) uninfected rats fed ad lib, (3) and infected rats fed isocalorically with (4) uninfected rats. Growth rates of infected rats did not differ from infected animals. Infected, meal fed rats limited to 15 g synthetic diet/day grew as rapidly as their uninfected counterparts, and infected rats fed ad lib did not consume more food than the comparable infected group. There were no significant differences in consumption or in excrement produced between groups (1) and (2) and groups (3) and (4). Weights attained by the worms were not affected by mode of host feeding (ad lib or meal fed), whether expressed as wet or dry weight. Since H. diminuta appears not to affect nutrient utilization or consumption in a healthy, unstressed host, at least on a gross level, it probably should be considered an endocommensal.