EXPRESS: Feline granulocytic anaplasmosis in Europe: anamnesis, clinicopathological abnormalities, bacterial DNA load, treatment, and outcome

Feline granulocytic anaplasmosis (FGA) is caused by Anaplasma ( A. ) phagocytophilum . Fever and thrombocytopenia are the most common clinicopathological abnormalities. Objectives The aim was to investigate regionality, seasonality, clinicopathological parameters, treatment, and outcomes in cats with FGA. Methods The database of a commercial laboratory was retrospectively screened for A. phagocytophilum -polymerase chain (PCR)-results on EDTA-blood submitted by European veterinarians from 01/2022 to 12/2025. Hematological data and bacterial DNA loads quantified by digital droplet-PCR were analyzed. Questionnaires were sent to the veterinarians asking for underlying diseases, anamnesis, clinicopathological abnormalities, treatment, and outcome in cats with FGA. Results 43/702 cats (6.1%) tested positive by A. phagocytophilum -PCR in Europe. Questionnaires were available for 29/43 cats (67.4%), all of which had outdoor access. Lethargy (23/29; 79.3%), anorexia (22/29, 75.9%), and fever (>39.5°C, 18/29, 62.0%) were the most reported findings. Thrombocytopenia was detected in 14/18 cats (77.8%) without concurrent diseases, anemia and leukopenia in 2/20 cats each (10.0%), eosinopenia in 10/17 (58.8%), and lymphopenia in 8/17 cats (47.1%). The bacterial DNA load was available for 27/43 cats (25 x 10 2 -87 x 10 6 , median 124 x 10 5 /ml EDTA-blood), revealing no significant correlation with hematological parameters. 20/21 cats (95.2%) were treated with doxycycline and one (4.8%) with enrofloxacin. Uncomplicated course of disease was reported in 19/21 cats (90.5%). In one cat treated with doxycycline for 10 days, another positive PCR was recorded one month later. Clinical signs recurred immediately in another cat treated with doxycycline for five days only. Conclusions and relevance FGA should be considered in cats with outdoor access, lethargy, inappetence, and most often mild thrombocytopenia and/or anemia, regardless of fever. Infected cats usually responded well to doxycycline with individual relapses if treated for 10 days or shorter. Treatment for 14 days to clear the infection, and PCR monitoring after finishing treatment are recommended.