Increased mortality in wild tits in North Rhine-Westphalia (Germany) in 2020 with a special focus on Suttonella ornithocola and other infectious pathogens

From April to June 2020, during a period of increased mortality of tits (Cyanistes caeruleus, Parus major, Periparus ater) in Germany, 84 tits were pathomorphologically and microbiologically investigated in governmental veterinary investigation offices in North Rhine-Westphalia using a broad diagnostic panel. Although Suttonella ornithocola was the most frequently detected bacterium (36/84), other pathogens, in particular Chlamydia psittaci (12/65), were also identified, sometimes as concurrent infection (3/36). In conclusion, S. ornithocola-infection seems to play an important role within the epidemic tit mortality in North Rhine-Westphalia, Germany in 2020. However, these cases may be combined with sporadic and/or endemic causes of mortality (e.g., other pathogens, trauma, or predation) for these species.