Ascaridia galli eggs obtained from fresh excreta, worm uteri or worms cultured in artificial media differ in embryonation capacity and infectivity

Abstract

<p><i>Ascaridia galli</i> infection models use eggs isolated from chicken excreta, worm uteri and worms cultured in artificial media. The aim of this study was to compare the infectivity of <i>A. galli</i> eggs isolated from these sources under two infection regimens. A 3 × 2 factorial arrangement was employed to test the infectivity of <i>A. galli</i> eggs from the three sources and two modes of infection (single or trickle infection). One hundred and fifty-six IsaBrown one day-old cockerels randomly assigned to the six treatment groups (n = 26) were orally infected with embryonated <i>A. galli</i> eggs obtained from the three <i>A. galli</i> egg sources (worm uteri, excreta or eggs shed in vitro) administered either as single dose of 300 eggs at one day-old or trickle infected with 3 doses of 100 eggs over the first week of life. Twenty-two negative control birds remained uninfected. Eggs obtained from cultured worms or excreta exhibited a higher embryonation capacity (P = 0.003) than eggs obtained from worm uteri. There were higher worm establishment (infectivity) rates from embryonated eggs originating from cultured worms and worm uteri compared with eggs obtained from fresh excreta (P < 0.0001). Trickle infection resulted in a significantly higher total worm burden (P = 0.002), establishment rate (P = 0.002) and excreta egg counts (EEC, P = 0.025) than single infection. Worm length was greater in birds infected with embryonated eggs from excreta than from uteri or cultured worms (P < 0.0001). However, mode of infection did not affect worm length (P = 0.719) and weight (P = 0.945). A strong significant positive linear correlation was observed between EECs and female worm counts at 12 weeks of post infection sampling (r = 0.75" P < 0.0001). Body weight of birds was negatively correlated with both worm burden (r = − 0.21" P < 0.01) and EEC (r = − 0.20" P < 0.05) at 12 weeks post infection. In conclusion, our results show that eggs shed by cultured worms or isolated from worm uteri had greater infective capacity than eggs harvested from excreta and that trickle rather than bolus infection resulted in higher worm establishment. These factors should be taken into account when considering artificial infection protocols for <i>A. galli</i>.</p>