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

Abstract

AbstractIn 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 naïve animals into an endemic tick area. Co‐infection also potentially increased severity of disease. The difficulties in controlling this outbreak are discussed.