Helminth infections in laying hens kept in organic free range systems in Germany

Abstract

This study describes the spectrum and intensity of helminth infections in laying hens kept in organic production systems in Germany. A total of 740 laying hens from 18 organic free range farms were collected between 2007 and 2010. The hens were sacrificed and the gastrointestinal tracts were examined for the presence and intensity of helminth infections with standard parasitological methods. Three nematode (Ascaridia galli, Heterakis gallinarum, Capillaria spp) and four cestode (Raillietina cesticillus, Hymenolepis cantaniana, Hymenolepis carioca, Choanotaenia infundibulum) species were found. Almost all hens (99.6%, N=737) harboured at least one helminth species. Average worm burden per hen was 218.4 (SD=218.3) worms. The most prevalent species were the nematodes Heterakis gallinarum (98%) followed by Ascaridia gali (88%) and Capillaria spp. (75.3%). The overall prevalence of the cestodes was 24.9%. Total worm burden was significantly higher during the summer season when compared with animals slaughtered during winter season (254 vs. 191, P<0.0001). The most dominant helminth species was Heterakis gallinarum averaging 190 (SE=9.8) worms per hen in the summer and 129 (SE=8.7) in the winter season (P<0.0001). Average Ascaridia galli burden was 25 (SE=2.0) in summer and 26 (SE=1.7) in winter (P=0.1160). Risk of infection with any of the nematodes was 50% higher in summer compared to winter (Ψ=1.49, P<0.0319). Probability of infection with any of the tapeworm species was 3.5 times higher in summer than in winter (P<0.0001).It can be concluded that the vast majority of hens are subclinically infected with at least one helminth species. The prevalence as well as intensity of the helminth infections, particularly with tapeworms, considerably increases in summer. The results indicate that it is essential to adopt alternative control strategies in order to lower infection risk in organic production systems which are gaining popularity.