Wednesday, February 15, 2012

Nasal Shedding of Equine Herpesvirus-1 from Horses in an Outbreak of Equine Herpes Myeloencephalopathy in Western Canada

Please note this is not information about a new outbreak, but publications from studies done during the outbreak of 2011. In this study, asymptomatic, afebrile horses shed the virus in their nasal passage for 9 days. It is important to understand EHV-1 to adequately protect your horses and your farms. This is a small piece of new information. Please vaccinate for EHV with a single antigen vaccine (that means not using a combo vaccine for your herpes protection). - Ben Buchanan

Nasal Shedding of Equine Herpesvirus-1 from Horses in an Outbreak of Equine Herpes Myeloencephalopathy in Western Canada:

Background

There is little information on the duration of nasal shedding of EHV-1 from horses with naturally occurring equine herpesvirus myeloencephalopathy (EHM).

Objectives

To evaluate the duration of nasal shedding of EHV-1 in horses affected by EHM.

Animals

One hundred and four horses naturally exposed to EHV-1, 20 of which had clinical signs of EHM.

Methods

All horses on affected premises were monitored. Those horses developing EHM were sampled in a longitudinal outbreak investigation. Nasal swabs were collected daily from 16 of 20 horses affected by EHM. A qPCR was performed on 98 of 246 nasal swab samples to determine nasal shedding duration. Historical and clinical information was analyzed to evaluate potential risk factors for developing EHM and duration of shedding during this outbreak.

Results

The last day shedding was detected in any horse was Disease Day 9. EHV-1 was detected in two-thirds of horses tested on Disease Days 0–3. The amount of EHV-1 DNA found in nasal swabs varied markedly and was not associated with disease severity or age. The odds of developing EHM were greater for febrile horses (OR = 20.3; 95% CI 3.4–390.3; P = .01) as well as for horses attending the riding clinic (OR = 4.1; 95% CI 0.84–21.65; P = .08).

Conclusions and Clinical Importance

Biosecurity measures should be implemented for a minimum of 14 days beyond the onset of clinical signs of EHM. Animal managers cannot rely on the severity of clinical signs to predict the duration of EHV-1 shedding.

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