The Importance of the Acanthocephalan Polymorphus minutus as a Parasite of Domestic Ducks in the United Kingdom

The intestinal parasite Polymorphus minutus sometimes causes severe losses of domestic ducks, but more often birds on free range are unaffected although exposed to infection. The causes of this are examined and an attempt is made to explain it. The worm has no innate seasonal occurrence, but can survive for many months in the intermediate host, by which it can also be spread for long distances along streams. The veterinary implications of these findings are considered.