Abstract.A study of acute respiratory disease in horses in Ontario was undertaken to determine the identity of current causative infectious agents. A nasopharyngeal swab was designed and utilized to maximize isolation of viruses, mycoplasma, and pathogenic bacteria. Serum samples were collected for parallel determination of antibody titers to equine influenza virus type A subtype 1 (H7N7) and subtype 2 (H3N8), equine rhinovirus types 1 and 2, equine herpesvirus type 1, Mycoplasma equirhinius, and Mycoplasma felis. Equine rhinovirus type 2 was recovered from 28/92 horses tested, and equine influenza virus type A, subtype 2, was recovered from 5. The mycoplasma and bacteria isolated were consistent with those commonly associated with nonspecific respiratory diseases in horses, except that Streptococcus pneumoniae capsular type 3 was isolated from 10 horses.Contagious respiratory infections in horses are major causes of both acute and chronic respiratory diseases resulting in impaired pulmonary function and reduced performance. 12,13,39 The chronic sequelae are important to the horse industry and include bronchopneumonia, chronic obstructive pulmonary disease, and exerciseinduced hemorrhage. 26,39 Earlier studies conducted in Ontario on thoroughbred 8 and standardbred horses used isolation and serodiagnosis to demonstrate that equine influenza virus type A subtypes 1 (AE1; H7N7) and 2 (AE2; H3N8), equine rhinovirus types 1 (ERhV-1) and 2 (ERhV-2), and equine rhinopneumonitis virus, now termed equine herpesvirus type 4 (EHV-4), were the major causes of respiratory disease. Other infectious agents that can induce respiratory disease in the horse are equine abortion virus 1 (distinguished as equine herpesvirus type 1 [EHV-1] 33 ), equine cytomegalovirus (equine herpesvirus type 2 10 ), equine arteritis virus (EAV), 34 equine adenovirus, 14,26 equine rhinovirus-3, 26 mycoplasmas, 16,40 and bacteria. 18,22 Vaccines are currently available in Ontario only for AE1, AE2, EHV-1, EHV-4, and EAV. These viral agents are believed to be the most common causes of clinical respiratory disease in North America. 26 Received for publication March 18, 1996. cious vaccination for AE1, 39 AE2, 39 EHV-1 , 24 and EHV-4 24 using modern vaccines. This continuing disease problem may be due to partial vaccine-induced immunity, genetic diversity of 26 or the antigenic drift of influenza viruses. 13,26,39 This study was conducted to identify the infectious agents more recently implicated in respiratory disease in horses in Ontario . 37 We used patient data, clinical examination, isolation, and paired serology for specific infectious agents. Nasal swabs from 92 horses with acute clinical respiratory disease from 29 different premises were cultured for viruses, mycoplasma, and pathogenic bacteria. Paired sera were collected and tested for antibodies to AE1, AE2, ERhV-1, ERhV-2, and EHV-1. For an additional 89 horses from 13 stables where respiratory disease occurred annually, these same serologic tests and antibody tests for EAV were perf...

The first case of phocine distemper in a seal from Canadian waters and the first case of clinical phocine distemper in a harp seal, Phoca groenlandica, is reported. A two-month-old female harp seal stranded on Prince Edward Island in May 1991. Significant clinical findings were lethargy and severe conjunctivitis. Pulmonary congestion was the main necropsy finding, and histological lesions included diffuse demyelinating nonsuppurative encephalitis and mild multifocal interstitial pneumonia. Acidophilic intracytoplasmic and intranuclear inclusions were present in cerebral neurons and astrocytes. Immunoperoxidase staining confirmed phocine distemper virus (PDV) antigen in the cytoplasm and nuclei of neurons, bronchiolar gland epithelium and transitional epithelium of the bladder. Infectivity titers of canine distemper virus (CDV) (Onderstpoort strain) and a morbillivirus isolated from a grey seal were significantly reduced by serum from the harp seal.

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In late spring of 1986, 10 of 23 Dall's sheep (Ovis dalli dalli) at the Metropolitan Toronto Zoo were moved to a new exhibit, where all developed severe respiratory signs refractory to anthelmintic and antibiotic therapy. In July, two animals died with chronic active bronch-pneumonia, and a third was euthanized because of pneumonia several months later. Bacteria were not isolated from the lungs of the first, steptococci and Pasteurella hemolytica were isolated from the other two, respectively; Mycoplasma ovipneumoniae was isolated from both. Pulmonary lesions in all three sheep were consistent with Mycoplasma sp. infection. Nasal swabs of the remaining animals yielded no consistent bacterial isolates; however, four of eight sheep were positive for M. ovipneumoniae. Viral cultures yielded an as yet unidentified herpesvirus. Sheep in the original and new herds had no serologic titers to parainfluenza-3, equine viral rhinopneumonitis, or infectious bovine rhinotracheitis, and had variable titers against bovine respiratory syncytial virus. No titers against M. ovipneumoniae were present in 13 sheep still in the original exhibit, but titers varied from 1:32 to 1:256 in eight pneumonic sheep. Sera taken from three sheep before or early in the outbreak were all negative for antibody to M. ovipneumoniae. Two of the affected Dall's sheep had been in contact with domestic sheep in the winter of 1985-1986, and M. ovipneumoniae was subsequently cultured from the domestic flock. Exposure to a new pathogen, and environmental and social stress in a new exhibit may have resulted in this severe disease in Dall's sheep.

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