Influenzavirusinfektionen beim Kleintier

In the past few years in Europe, an increased incidence of infections with the highly pathogenic avian influenza virus has occurred in poultry. A direct transmission of avian influenza viruses to mammals has only been described for a few species, e.g. pig, mink, ferret and seal. With respect to the transmission of these viruses to man, it has been assumed that the pig plays a special role as this species can be infected by both avian and human influenza viruses, In the meantime, the infection has occurred in Asia, Europe and Africa and for the first time, lethal infections with the highly pathogenic avian influenza subtype H5N1 have been observed in cats and one dog. In addition, infections in humans have been repeatedly seen, a fact which indicates the special biological characteristics of this virus. In the present paper, the basic characteristics of influenza viruses are explained and an overview of influenza virus infections in dogs and cats is given, Our investigations revealed that the clinical signs seen in cats infected with H5N1 are dependent on the infective dose. In addition, cats which have been immunised with an inactivated H5 antigen exhibit a significantly reduced virus excretion rate and were protected against clinical symptoms. Dogs appear to be less susceptible to H5N1 in contrast to other influenza virus subtypes, which have been associated with severe clinical symptoms in this species. Our contact studies showed also that the H5N1 infection is not transmitted from infected cats to uninfected dogs. Finally, the present paper summarises the criteria which can be used to justify the suspicion of an H5N1 influenza virus infection in cats and which samples in such cases should be investigated