Assessment of the inhibitory effects of disinfectants on the embryonation of Ascaridia columbae eggs.

This study was set out with the aim of assessing the effects of the most commonly available commercial disinfectants on embryogenesis of A. columbae eggs. In addition to the distilled water treatment as a control group, four disinfectants were tested that included formalin, povidone iodide, TH4, and Virkon-S, in three independent experiments. In the first experiment, an overnight incubation with the working concentration of disinfectants resulted in significant inhibition of 80%, 85%, and 98% of embryonic development at day 9 post-treatment with formalin, povidone iodide, and TH4, respectively. This inhibition was continued through days 12 and 15 with the three tested disinfectants. Virkon-S did not affect embryogenesis with larval development comparable to that of the control group. In the second more dissected experiment, contact times of 10, 20, 30, and 60 minutes were set out for each disinfectant with embryogenesis inhibition results echoed that of the first experiment, with all disinfectants but Virkon-S inhibited larval development in significant proportions of eggs. Again, Virkon-S was very neutral in its effect on embryogenesis. When pigeon fecal matters were mixed with eggs and were subjected to disinfectants, discrepancies to results of the first two experiments were observed with only formalin inhibited embryogenesis in considerable proportion of eggs. Thus, and with the exception of Virkon-S, disinfectants tested at levels similar to those applicable in poultry in-houses and farms exhibited potent ovicidal activities on free eggs. To our knowledge, this is the first study involving the application of the commonly used in-poultry houses disinfectants to inactivate or delay the embryogenesis of bird Ascarids. The future perspective will potentially involve the in-field applications of the efficient disinfectants to eliminate or reduce the dissemination of infections with bird Ascarids in the chicken, turkey, pigeons, and other poultry houses.

Embryonation ability of Ascaridia galli eggs isolated from worm uteri or host faeces.

Experimental infection models for Ascaridia galli rely on the use of eggs isolated either directly from worm uteri or from host faeces. We investigated whether A. galli eggs isolated from the two sources differ in their embryonation ability. A. galli eggs originating from 12 worm infrapopulations were isolated both from faeces of the living host (faecal eggs) and directly from worm uteri after host necropsy (uterine eggs). The isolated eggs from each infrapopulation and source were incubated in Petri dishes (n=24) containing a potassium-dichromate (0.1%) medium for 28 days (d) at room temperature. Starting from the day of egg isolation (d0), in ovo larval development was evaluated every second day by examining morphological characteristics of 200 eggs/petri dish. A total of 72,000 eggs were classified into undeveloped, early development, vermiform or fully embryonated stages. Isolation procedures caused similar damage to uterine and faecal eggs (2.2% and 0.5%, respectively; P=0.180). The first sign of in ovo embryonic development in faecal eggs (7%) was observed during the 24-h period when faeces were collected. On d28, a higher percentage of uterine eggs remained undeveloped when compared with faecal eggs (58.6% vs 11.0%; P<0.001). Although a higher (P<0.001) percentage of faecal eggs entered both the early developmental and vermiform stages, which took place primarily within the first two weeks of incubation, there was no time-shift between the development of faecal and uterine eggs. Starting from day 10, higher (P<0.05) percentages of faecal eggs completed embryonation compared with uterine equivalents. Eggs from both sources reached a plateau of embryonation by the end of 2nd week of incubation, with faecal eggs having a greater than two-fold higher embryonation ability. Cumulative mortality was higher in uterine eggs (14.3%) than in faecal eggs (0.2%). We conclude that faecal eggs have a higher embryonation ability than uterine eggs possibly due to maturation differences.