The role of culture media on embryonation and subsequent infectivity of Capillaria obsignata eggs

This study investigated whether infectivity of Capillaria obsignata eggs depends on media culture used for embryonation. Intact female worms were kept in one of following four media: 0.5 % formalin, 2 % formalin, 0.1 % potassium dichromate and 0.1 N sulfuric acid. Embryonation rates of the eggs were quantified either daily in intact females for 16 days, or weekly in disrupted females. Infectivity of the embryonated eggs was tested through an experimental infection of chickens with a single dose of 250 eggs/ bird. The vast majority of the eggs (>82 %) in the first two thirds of the uteri was able to complete embryonation, irrespective of the culture media used for incubation. However, only 32.6 % of total eggs could be harvested after disruption of the intact females. Embryonation rates of the eggs from disrupted worms were different among four culture media, with 0.1 N sulfuric acid resulting in the highest embryonation rate (44.2 %). All the experimentally infected birds harboured mature worms, with varying establishment rates depending on the culture media (P < 0.001). Incubation of the eggs in potassium dichromate 0.1 % resulted in a lower (P < 0.001) establishment rate (10.2 %) when compared with formalin (70.5 and 47.9 % for concentrations at 0.5 and 2 %, respectively) or with 0.1 N sulfuric acid (57.5 %). It can be concluded that most of the eggs in first two thirds of the uteri in the intact females have the potential to complete embryonation without being influenced by the culture media. However, disruption of the intact females results in lower number of harvestable embryonated eggs, with a considerable variation due to culture media used. With the exception of 0.1 % potassium dichromate, any of the three media, particularly 0.1 N sulfuric acid, can be suggested for embryonation of C. obsignata eggs.