High morbidity associated with an outbreak of tick-borne disease in a dairy herd, Cornwall

摘要

In April 2020, animals in a herd of 180 dairy cows began displaying pyrexia, milk drop and condition loss. Some animals aborted while others developed anaemia and red-coloured urine. Copious ticks were noted on affected animals. Blood smear examination performed on sick animals detected piroplasms within erythrocytes, and a pan-piroplasm PCR and sequencing confirmed the presence of Babesia divergens. Further PCR testing detected Anaplasma phagocytophilum in some of the animals. In a number of animals, co-infection with both pathogens was demonstrated. A range of control measures were implemented with varying levels of success, and clinical cases continued until winter housing of cows in November. A total of 61 animals were affected. The main contributory factor in this case was likely buying in of large numbers of naive animals into an endemic tick area. Co-infection also potentially increased severity of disease. The difficulties in controlling this outbreak are discussed.