Histophilus somni infection: an outbreak in cattle in Central Italy

Objective of the study - Histophilus somni is responsible for a wide variety of systemic diseases in addition to thrombotic meningoencephalitis (TME), including respiratory disease syndromes, myocarditis, reproductive disease syndromes, polyarthritis, mastitis, eye disease and septicaemia. The aim of this study is to describe a H. somni outbreak in cattle in Central Italy. Methods - In this outbreak, between January and April 2016, nine one-year-old male calves suffered from progressive eye disease, resulting in blindness, ataxia, weight loss and mild respiratory disease, and died within 20 days of the onset of symptoms. Nasal and eye swabs were collected from two other calves for bacteriological and virological analysis. After slaughter, the brain and testicles were also collected for the macroscopic and histopathological examinations. Results - All the samples collected were negative for BoHV-1, BVDV, PI-3 and Mycoplasma spp., while H. somni was isolated from the testicles, brain and eye swabs. Mannheimia haemolytica was also isolated from nasal swabs. Histological examination confirmed the presence of lesions typical of TME. All the remaining calves were vaccinated with HIPRABOVIS® SOMNI/Lkt starting from the 2nd month of age. After a follow-up of 12 months, no other case of infection was diagnosed. Conclusions - This outbreak confirms the presence of H. somni in Central Italy and its responsibility for the onset of TME and Bovine Respiratory Complex which are often lethal, especially in calves under one year of age. Effective prevention through vaccination can reduce the appearance of clinical signs, lung damage and consequently the use of antibiotics.