NEW CAUSE OF GLAUCOMA IN HORSES
the development of EMPF. The host immune response, however, is definitively involved in this process.”
The current “gold standard” for diagnosing EMPF is a lung biopsy to look for signs of fibrosis, combined with a positive polymerase chain reaction (PCR) test for EHV-5 within the tissue samples. Lung biopsies, however, can be difficult to obtain from a horse showing severe respiratory signs and may lead to serious complications.
Looking for an easier alternative, the Davis researchers sought to determine how effective the testing of blood, nasal secretions and lung fluid could be in identifying EHV-5-associated EMPF.
The researchers first used clinical findings, radiographic imaging and analysis of lung tissues and fluid to divide 70 horses into four groups: those with no respiratory illnesses, those with inflammatory airway disease, those with non-EMPF interstitial lung diseases and those with EMPF. PCR was then used to test each horse’s blood, nasal secretions and lung fluid for EHV-5.
The data showed that the presence of EHV-5 in lung fluid was strongly associated with EMPF. “Although possible, it is very rare to find a horse that tests positive for EHV-5 in lung fluid that does not have EMPF,” says Pusterla.
EHV-5-positive blood and nasal secretion tests were also associated with EMPF, but with lower sensitivity (meaning the tests could miss some cases) and specificity (meaning the tests could produce false positives). Considered together, however, positive blood and nasal secretion tests were more reliable in detecting horses with EMPF than each was on its own.
These findings, says Pusterla, show that less invasive measures can be used instead of lung biopsies in making a diagnosis of EMPF. “In a case suspected on the basis of clinical and radiographic abnormalities, blood and nasal secretions positive for EHV-5 can support that diagnosis,” he says. Confirmation of the diagnosis can be made via PCR testing of lung fluid or a lung biopsy.
Reference: “Assessment of quantitative polymerase chain reaction for equine herpesvirus-5 in blood, nasal secretions and bronchoalveolar lavage fluid for the laboratory diagnosis of equine multinodular pulmonary fibrosis,” Equine Veterinary Journal, published online January 2016
A new cause for glaucoma in horses is documented in a recently published research paper.
The paper describes the cases of five horses referred to veterinary clinics in various parts of the country---Minnesota, New York, Ohio and Washington State---because of severe fluid buildup in the cornea (corneal edema), high pressure within the eyeball (glaucoma) and corneal