Changes in parasite transmission stage excretion after pheasant release

Area of Science:

• Veterinary Parasitology
• Wildlife Health
• Gamebird Management

Background:

• Farm-bred gamebirds are often released to supplement wild populations.
• Captive-reared animals can harbor and excrete parasites, potentially impacting naive wild populations.
• Understanding parasite dynamics in released birds is crucial for conservation and disease management.

Purpose of the Study:

• To investigate the shedding of parasite transmission stages in farm-bred ring-necked pheasants before and after release into the wild.
• To assess the impact of anthelmintic treatment on parasite excretion.
• To evaluate the relationship between parasite shedding, host condition, and survival.

Main Methods:

• Faecal samples from 77 ring-necked pheasants were analyzed for coccidian oocysts and nematode eggs.
• Parasite shedding was quantified before and after release.
• Birds were treated with fenbendazole prior to release.
• Relationships between parasite excretion, body condition, and survival were examined.

Main Results:

• Anthelmintic treatment reduced parasite shedding, but excretion significantly increased post-release for all investigated parasites (Eimeria sp., Heterakis sp., Capillaria sp.).
• New infections (Ascaridia sp.) were detected after release, indicating wild acquisition.
• Higher Heterakis excretion was linked to poorer pheasant body condition; Capillaria sp. eggs were more abundant in females.
• No significant correlation was found between parasite excretion and pheasant survival.

Conclusions:

• Release of captive pheasants leads to increased shedding of parasite transmission stages, posing a risk to indigenous wildlife.
• This shedding pattern may contribute to restocking failures.
• Enhanced prophylactic strategies are recommended to minimize pathogen transmission from released gamebirds.