Prevalence of Gastrointestinal Helminths in Thai Indigenous Chickens Raised Under Backyard Conditions in Northern Thailand

This study aimed to evaluate the prevalence and worm burden of gastrointestinal parasites in Thai indigenous chickens (Gallus gallus domesticus) kept under extensive backyard conditions in Northern Thailand. A total of 211 male (N = 98) and female (N = 113) chickens from 11 smallholder farms were selected randomly between December 2016 and May 2017. At slaughter, fecal samples were collected to estimate fecal egg counts (presented as eggs per gram of feces) and oocyst counts (oocyst per gram of feces). The gastrointestinal tract of each animal was examined for the presence of parasites. The percentage of FEC- and FOC-positive samples was 33.7 and 55.4%, respectively. On average, 111 ± 328 ascarid eggs and 2,983 ± 11,641 coccidian oocysts were found. From the post mortem examination, 3 nematode species and cestodes were recovered. A total of 156 (73.9%) of the sampled chickens were infected with at least 1 helminth species. Average worm burden per chicken was 46.7 (SD = 50.9, median = 30). The most prevalent species were the nematodes Heterakis gallinarum (70.6%) followed by Ascaridia galli (60.2%) and Capillaria spp. (44.1%). The overall prevalence of cestodes was 27.7%. Apart from A. galli with higher prevalence in males than in females (P ≤ 0.05), gender did neither affect prevalence nor worm burden (P > 0.05). Growth performance was not negatively affected by helminth infections. In conclusion, the vast majority of Thai native chickens are subclinically infected with at least 1 helminth species under the studied backyard conditions.