A comparison of the prevalence and burdens of helminth infections in growers and adult free-range chickens.

Matched samples of 100 chickens of each of growers and adult rural free-range chickens in Morogoro, Tanzania, were purchased from the beginning to the end of the long rainy season. At necropsy, the trachea, the gastrointestinal tract and the oviduct were examined for helminth infections. The helminth species isolated comprised 18 nematodes and 8 cestodes but no trematodes. Tetrameres fissispina is a new record in Tanzania. All the chickens harboured at least three different helminth species. Growers contained 4-14 and adults 3-12 helminth species. The number of species isolated per chicken increased as the rainy season advanced. The prevalence of the following species were significantly higher in growers than in adults (p < 0.05); Ascaridia galli (69% of growers, 29% of adults); Syngamus trachea (14%, 3%); Tetrameres americana (94%, 82%); Trichostrongylus tenuis (43%, 7%); Choanotaenia infundibulum (15%, 6%); Davainea proglottina (9%, 2%); and Raillietina tetragona (36%, 21%). Allodapa suctoria (3%, 20%) and Capillaria annulata (1%, 10%) had a significantly lower prevalence in growers than in adults (p < 0.05). There were significantly higher worm burdens (p < 0.05) in growers than in adults for A. galli, Capillaria caudinflata, R. tetragona, S. trachea, T. americana, T. fissispina and T. tenuis. Conversely, A. suctoria and C. annulata showed significantly higher worm burdens in adults (p < 0.05). The sex of the chickens influenced the burdens of Heterakis brevispiculum (p < 0.05). There was an interaction effect such that growing males and adult females had statistically higher (p < 0.05) burdens of T. tenuis and A. suctoria, respectively.