Monitoring and detection of acute viral respiratory tract disease in horses.
OBJECTIVE
To develop a system to monitor and detect acute infections of the upper respiratory tract (i.e., nares, nasopharynx, and pharynx) in horses and to assess the association among specific viral infections, risk factors, and clinical signs of disease.


METHODS
Prospective study.


METHODS
151 horses with clinical signs of acute infectious upper respiratory tract disease (IURD) from 56 premises in Colorado.


METHODS
Health management data, blood samples, and nasal or nasopharyngeal swab samples were obtained for 151 horses with clinical signs of acute IURD. Of these horses, 112 had an additional blood sample obtained during convalescence and were considered to have complete sample sets. Samples were tested for evidence of respiratory tract infection by use of ELISA, virus isolation, and serologic testing of paired serum samples.


RESULTS
Viral infections were identified in 65 horses with complete sample sets; influenza virus infection was identified in 43 horses, equine herpesvirus (EHV) infection in 18, and mixed influenza virus and EHV infections in 4. On 14 premises, samples were obtained from more than 1 affected horse. Viral infections were identified in horses on 11 of 14 premises. Equine herpesviruses were isolated from 10 horses. A relationship was not found between vaccination history and identification of EHV or influenza virus infections. An infection with EHV was less likely to be identified in horses with initial (acute) antibody titers > 1:16 to EHV.


CONCLUSIONS
Influenza virus (specifically, A/equine/2) was the most common virus associated with acute IURD. Use of multiple diagnostic tests and obtaining samples from more than 1 horse in an outbreak may improve detection of viral infections.
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins 80523, USA.
E L
EL
Mumford
J L
JL
Traub-Dargatz
M D
MD
Salman
J K
JK
Collins
D M
DM
Getzy
J
J
Carman
D000208:Acute Disease; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000032:analysis; D003120:Colorado / Q000453:epidemiology; D004196:Disease Outbreaks / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D006566:Herpesviridae Infections / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*; D004861:Herpesvirus 1, Equid / Q000276:immunology / Q000302:isolation & purification; D006734:Horse Diseases / Q000175:diagnosis* / Q000453:epidemiology; D006736:Horses; D009980:Influenza A virus / Q000276:immunology / Q000302:isolation & purification; D009976:Orthomyxoviridae Infections / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*; D014611:Vaccination / Q000662:veterinary; D018140:Varicellovirus / Q000276:immunology / Q000302:isolation & purification
D000914:Antibodies, Viral; D000956:Antigens, Viral