Artificial infection of chickens with Capillaria obsignata eggs embryonated in different media

The present study investigated whether incubation media have an impact on infectivity of Capillaria obsignata eggs in chickens infected with gradually increasing doses. C. obsignata eggs collected from female worms were incubated either in formalin (0.5% or 2%) or in potassium dichromate 0.1% or in sulfuric acid 0.1N for three weeks (wk). One-day-old male chicks (N=92) were reared in a parasite-free environment, and infected with 0, 500, 1000 or 2000 eggs at an age of 3 wk. Post-mortem parasitological examinations were performed on day 28 p.i. Although all the infected birds harboured adult worms, their growth performance was not affected. Furthermore there was no significant interaction effect between incubation media and infection dose on worm establishment rates (P=0.080), while main effects of these two factors were significant (P<0.05). The average number of adult worms found in birds infected with the eggs incubated in potassium dichromate were significantly lower (P<0.001) than in formalin 0.5%, formalin 2% and sulfuric acid 0.1N. A higher (P<0.05) percentage of larvae could establish themselves in the intestines when the birds were infected with 500 eggs (40.5%) instead of 2000 eggs (26.2%), indicating density dependent effects. It is concluded that formalin (particularly 0.5%), and sulfuric acid can successfully be used as incubation media for C. obsignata eggs, whereas potassium dichromate impairs subsequent infectivity of the eggs. Although effects of media on the infectivity of the eggs were confirmed to be fairly repeatable, no harmful effect of infection was quantified on the host animal performance with the infection doses up to 2000 eggs.