Look out for Histophilus somni septicaemia / myocarditis

Over the last ten years, SRUC Veterinary Services has seen a steady increase in the number of Histophilus somni septicaemia cases. This is distinct from the respiratory form, which causes a fibrinous and purulent bronchopneumonia.  The septicaemic form typically affects 6 to 12-month-old, weaned, beef calves in the autumn/winter period.  Animals are either found dead or can show a range of non-specific clinical signs including recumbency, respiratory signs, pyrexia, neurological signs, blindness and lameness.

On post-mortem examination some lesions can be quite subtle.  Necrotic or purulent lesions are frequently present in the papillary muscles of the left ventricle of the heart, therefore it is important to carefully examine these areas (see photos in attached presentation). Laryngitis is also found in a smaller proportion of cases. Note that respiratory signs in these cases of septicaemia may actually be due to pulmonary oedema secondary to septicaemia or left sided heart failure rather than pneumonia.

Due to its fastidious nature, and often prior antibiotic use, Histophilus somni is often not successfully cultured in these cases, therefore having material available for PCR and histopathology is very useful to confirm the diagnosis.

This presentation has further details on the Scottish cases of Histophilus somni septicaemia, which includes information on sampling. Also this article was produced by SRUC Veterinary Services for the Vet Record in 2019 on Histophilus somni septicaemia.  If you wish to discuss suspect cases further, please get in touch.   

Posted by Veterinary Services on 08/01/2021