Diagnosis of mixed infections with myxovirus influenzae A equi 2 and herpes virus equi 1 among Danish stud horses.

Examination of nasopharyngeal secretion and organ material from clinical cases of respiratory diseases in horses, using inoculation of embryonated hen eggs and rabbit and horse kidney cell cultures, resulted in the isolation of influenza virus and herpes virus. In 2 cases, both viruses were present in the same specimen. On the basis of the physio-chemical, cytological and serological criteria, the viruses were found to be identical with influenza virus type A equi 2 and herpes virus equi type 1. The methods for serological diagnosis and characterization of the influenza and herpes viruses are discussed. Detailed serological examinations of blood specimens from the clinical cases confirmed the aetiological significance of the isolates and the presence of mixed infections. Further characterization of a strain of influenza virus was carried out by inoculation experiments on horses. These included reproduction of clinical influenza, reisolation of the strain in casu and a study of the antibody formation.