Duck body condition affects the number of parasites in the gastrointestinal tract, as evaluated with the Akaike information criterion.

The aim of the study was to determine the relationship between the body condition, and the number of parasites in the gastrointestinal tract of the tufted duck (Aythya fuligula), using the Akaike information criterion. Absolute and relative measurements of 197 ducks were taken. Liver mass was positively associated with the number of parasites in the duodenum (β = 0.5). Heart mass affected positively the number of parasites in the rectum (β = 2.3), the number of nematodes in the jejunum (β = 7.45), the total number of trematodes (β = 1.7), their number in the ceca (β = 7.3) and rectum (β = 4.2), and the number of cestodes in the ceca (β = 8.2). Beak length influenced the number of nematodes in the rectum (β = 1.7). Left tarsometatarsus length (β = 1.4) and relative head height (β = -2.0) affected the number of trematodes in the ceca. Tail length influenced negatively the number of cestodes in the ileum (β = -0.2). Similarly, a ratio of body mass to body length was negatively associated with the total number of parasites (β = -0.1), their number in the ceca (β = -0.2) and rectum (β = -0.3), the total number of trematodes (β = -0.3), and their number in the ceca (β = -0.5) and rectum (β = -0.4). A ratio of keel-skin length to keel length affected differently the total number of parasites in the ceca (β = 9.1), the number of nematodes in the jejunum (β = -17.9) and the number of trematodes in the duodenum (β = -5.8). A ratio of fat mass to body length affected the number of cestodes in the jejunum (β = 1.8). The present study indicates some morphological and anatomical parameters that may be useful for determining the correlation between the body condition and the level of parasitic infection.