Outbreak of infectious bovine rhinotracheitis with high clinical score in Ragusa (Sicily, Italy)

Infectious bovine rhinotracheitis (IBR) is a widespread disease in Italy, resulting from bovine herpesvirus 1. Some Italian Regions started compulsory/voluntary eradication programmes. Sicily has not adopted any programme yet, although the disease is present at a herd prevalence of around 60% (1). Today, the disease is multisymptomatic but most infections run a mild or subclinical course (2); the classical symptoms of IBR (upper respiratory tract symptoms and abortion) are observed in few individuals in an infected herd. A new outbreak of IBR with high clinical score is reported in a cattle herd (243 animals) in the area of Ragusa (Sicily, Italy). The herd was characterized by high reproductive indexes, and was free of brucellosis, enzootic bovine leucosis, tuberculosis and bovine virus diarrhoea. With regard to IBR, the animals were seronegative and unvaccinated. Biosafety measures were strictly applied. Starting from the half of August 2015, 138 cows, 8 heifers, 4 calves, 1 bull (62% of the herd) showed progressive respiratory signs (nasal discharge, conjunctivitis, cough and dyspnoea) and general signs (fever, drop of milk yield and food intake, reduced rumination). Abortion at 4-8 months of pregnancy was observed in 22% of pregnant cows, premature calving in 4% and stillbirth in 9%. The outbreak was dealt with using isolation and symptomatic therapy, but 4% of the animals died. At the end, 19% unproductive cows were slaughtered. A serological screening was performed 7 days after the onset of clinical signs which showed an IBR virus glycoprotein gB ELISA positive reaction, while IBR virus glycoprotein gE was negative. After 20 days a seroconversion of protein gE was finally observed, confirming a major infection of wild strain IBR virus. A vaccination schedule was applied using a live marker and conventional vaccine respectively in young and adult animals. IBR outbreak with high clinical score (abortion, mortality) is a severe risk when IBR-free and unvaccinated herd are close to infected herds. The widespread use of the indirect assay of gE glycoprotein to screen herds has to take in consideration the delayed antibody answer and the less immunogenicity of the protein (3). A double sampling spaced of at least 21-35 days and a 4-week quarantine period are proposed for evaluation of IBR status of animals, especially before and after movement or participation to animal shows. 1.Purpari et al. Valutazione della prevalenza di IBR e BVD nella Regione Sicilia: un modello sperimentale. Atti SIB 2005, 37: 111-5. 2.Pritchard et al. Subclinical breakdown with infectious bovine rhinotracheitis virus infection in dairy herd of high health status. Vet Rec 2003, 153: 113-7. 3.OIE Manual for Terrestrial Animals. Chapter 2.4.13. Infectious bovine rhinotracheitis/ infectious pustular vulvovaginitis, 2010.