Prevalence of Trichomonas gallinae in northern goshawks from the Berlin area of northeastern Germany.

In recent years, the northern goshawk (Accipiter gentilis) has colonized suburban and urban areas in Berlin, Germany, and elsewhere in Europe. Because of the high proportion of feral pigeons (Columba livia f. domestica) in their diet, urban goshawks are suspected to have a high infection rate with Trichomonas gallinae. Therefore, from 1998 to 2001, we examined 269 nestlings from 90 nests for infection with T. gallinae by culture of swabs taken from the oropharynx and checked their oropharynx for the presence of caseous lesions indicative of trichomonosis. In 80% of the nest sites (n=90), at least one nestling was infected. The nestling infection rate with T. gallinae was 69.7% (n=33) in 1998, 73.0% (n=89) in 1999, 55.8% (n=77) in 2000, and 62.9% (n=70) in 2001. In total, 65.1% of the northern goshawk nestlings were culture positive for T. gallinae. Prevalence increased with the age of nestlings (chi2=12.4, n=269, df=5, P=0.03) and tended to increase with brood size (chi2=9.345, n=269, df=4, P=0.053). Caseous lesions were present in 12 nestlings (4.5%), but only 10 of these were culture positive for T. gallinae. Two nestlings (0.7%) had large caseous lesions (diameter>1 cm) characteristic of late-stage trichomonosis and died shortly after examination. It is suggested that the combination of a high prevalence of T. gallinae with a low rate of pathologicic changes is the result of an evolutionary-adapted parasite-host relationship.