Tetrameres americana Cram (1927) populations in chickens infected with different dose levels

Three groups of 20-45 Lohman brown chickens aged 3 weeks were orally infected with doses of 25, 100 and 400 Tetrameres americana, respectively. Fifteen chickens were kept as uninfected controls. Every third week in a period of 12 weeks, 5-15 chickens were slaughtered and the proventriculi were examined for the presence of adult stages of T. americana. From day 21 post-infection, pooled feacal samples were examined for parasite eggs, whereas the weight gain of the chickens was monitored weekly. The parasite established the infection in similar rates in all the three groups, 9.5-15.2%, except on day 84 post-infection, when the establishment rate of the high-dose group was significantly lower (P < 0.005). The average worm burden increased with increasing dosages, though displaying the worm burden of the high-dose group as being roughly halved on day 84 post-infection, thus suggesting an expulsion of worms. Females were more abundant than males. The mean lengths of male and female specimens showed no significant differences between the groups. The egg output was also increased with increasing dosages with the earliest prepatent period of 38 days post-infection found in the high-dose group. Infected chickens exhibited no difference in weight gain in comparison with the controls. This study demonstrated that single infections with varying doses influenced the establishment rate and the worm burden but not the parasites egg excretion, worm size nor the weight gain and mortality of the final host.