Parasitic worms in commercial free-range poultry flocks in England and Wales

INFECTIONS with parasitic worms were frequently seen when most poultry flocks in the UK were kept on free-range systems. A postmortem survey carried out in the late 1950s showed that the most common parasitic worms in chickens were the caecal worm (Heterakis gallinarum), found in 77 per cent of adult fowl; different species of hairworms (classified then as Capillaria species), found in 58 per cent of adult fowl; and the large roundworm (Ascaridia galli), found in 40 per cent of adult fowl (Norton 1964). Tapeworms were uncommon, found in only 2 per cent of adult free-range fowl. This short communication summarises the results of a small survey carried out to determine the current prevalence of nematodes in free-range chickens. Veterinary surgeons with a particular interest in poultry were asked to nominate clients who had free-range chickens and who might be willing to participate in the survey. Of 117 free-range flocks nominated and approached, 27 sites in England and Wales had birds of a suitable age. Most of the flocks contained 1500 to 12,000 birds, although one flock contained 200 birds and another, 40,000 birds. Twenty of the 27 flocks had been wormed before the onset of lay, and 14 of the flocks were wormed during lay. Sixty portions of faeces were collected by the flock owner or site manager on each of these 27 sites on four occasions: when the birds were approximately 20 weeks of age (first sampling), approximately 33 weeks of age (second sampling), approximately 46 weeks of age (third sampling), and approximately 59 weeks of age (fourth sampling). The first samples were collected in September 1998, and the last samples in January 2000. The faecal samples were tested for worm eggs using a modification of the McMaster technique (Thienpont and others 1986). Worm eggs were identified using the key described by Thienpont and others (1986). The eggs of H gallinarum and A galli are very similar in appearance, although the side-walls of the latter tend to be more barrel shaped (Thienpont and others 1986). To avoid the possibility of inaccurate differentiation between these two species in the absence of corroborative postmortem examinations, these eggs were grouped together as Ascaridia/Heterakis. Worm eggs were detected in the faeces of 26 of the 27 flocks monitored (96 per cent of flocks). In 21 flocks only Ascaridial Heterakis eggs were detected, in four flocks Ascaridia/Heterakis plus hairworm (subfamily Capillariinae) eggs were found, and in one flock only hairworm eggs were detected. If the results from flocks which had been wormed within the previous three months, either before or during lay, are excluded, 43 per cent of flocks were positive at the first sampling (approximately 20 weeks of age), 62 per cent were positive at the second sampling (approximately 33 weeks of age), 79 per cent at the third sampling (approximately 46 weeks of age), and 81 per cent at the fourth sampling (approximately 59 weeks of age). Thirteen flocks were not wormed at all during lay, and the results from these flocks demonstrated a similar pattern. Five of these flocks (38 per cent) were positive for worm eggs at the first sampling, six (46 per cent) were posi~~~~~~~~~~S ~~~~~~~~~~~~~~~~~------