Experimental transmission of avian-like swine H1N1 influenza virus between immunologically naïve and vaccinated pigs.

BACKGROUND: Infection of pigs with swine influenza has been studied experimentally and in the field; however, little information is available on the natural transmission of this virus in pigs. Two studies in an experimental transmission model are presented here, one in immunologically naïve and one in a combination of vaccinated and naïve pigs. OBJECTIVES: To investigate the transmission of a recent 'avian-like' swine H1N1 influenza virus in naive piglets, to assess the antibody response to a commercially available vaccine and to determine the efficiency of transmission in pigs after vaccination. METHODS: Transmission chains were initiated by intranasal challenge of two immunologically naïve pigs. Animals were monitored daily for clinical signs and virus shedding. Pairs of pigs were sequentially co-housed, and once virus was detected in recipients, prior donors were removed. In the vaccination study, piglets were vaccinated and circulating antibody levels were monitored by haemagglutination inhibition assay. To study transmission in vaccinates, a pair of infected immunologically naïve animals was co-housed with vaccinated recipient pigs and further pairs of vaccinates were added sequentially as above. The chain was completed by the addition of naive pigs. RESULTS AND CONCLUSIONS: Transmission of the H1N1 virus was achieved through a chain of six pairs of naïve piglets and through four pairs of vaccinated animals. Transmission occurred with minimal clinical signs and, in vaccinates, at antibody levels higher than previously reported to protect against infection.

Pathological and electrophysiological features of a canine cone-rod dystrophy in the miniature longhaired dachshund.

PURPOSE: To characterize the electrophysiological and histopathological features of a retinal degenerative disease in a colony of miniature longhaired dachshunds known to have a form of progressive retinal atrophy (PRA). METHODS: Serial electroretinograms were recorded from affected homozygous (n = 36) and heterozygous (n = 15) dogs. Morphologic investigations including immunohistochemistry and lectin histochemistry were performed on selected homozygous animals (n = 15). RESULTS: Clinical findings included loss of tapetal hyperreflectivity. The mode of inheritance was autosomal recessive. An early dramatic reduction of cone-specific ERG amplitude with a more modest reduction in rod b-wave amplitude was demonstrated. Progressively, rod specific responses diminished until there were no recordable responses to the ERG stimuli at 40 weeks of age. Morphologic changes confirmed early cone inner and outer segment loss. Other abnormalities included opsin mislocalization and outer nuclear layer thinning due to the subsequent loss of rod photoreceptors. CONCLUSIONS: A novel canine cone-rod dystrophy has been identified.