Research in infectious disease in wild birds

Abstract

Trichomoniasis, caused by a protozoan parasite, has been known for many years in pigeons and doves and also in birds of prey, but in 2005 it emerged in finches, first causing necrotic ingluvitis, infection of the crop.1 Since then epidemic mortality has occurred every year in the late summer and early autumn in birds visiting garden feeding stations, and particularly in Greenfinches (Chloris chloris). In the first year this disease led to a reduction in greenfinch populations of 35% and in chaffinches of 20% in areas with highest reports of the condition. Before the outbreak these finch species were seen in around 80% of gardens yet in the years following first reports of the disease sightings have halved.2 Now in the UK the International Union for the Conservation of Nature (IUCN) Red list classifies the breeding greenfinch population as endangered. Spread to Europe seemed to occur in 2008 with the same A1 clonal strain of Trichomonas involved. It appears that year-round feeding of garden birds at stations such as bird tables and congregation of birds at such localities has led to the spread of this condition.3