If an EHV-1 nasal swab tests positive and a blood sample tests negative, how should this be interpreted?

If an EHV-1 nasal swab tests positive and a blood sample tests negative, how should this be interpreted?

• A. Horse is latently infected
• B. Horse has recovered and may comingle with other horses
• C. Horse is shedding the virus
• D. Horse is viremic

Answer: (C)

The main idea is that a positive nasal swab means the horse is shedding the virus through respiratory secretions, making it contagious to others. A negative blood sample indicates there is no detectable virus in the bloodstream at that moment, so there isn’t viremia. Latent infection wouldn’t typically show up as nasal shedding, and recovery with the horse still mingling would not involve active shedding. Viremia would be indicated by virus in the blood, which isn’t present here. So, the interpretation is that the horse is actively shedding the virus, posing a transmission risk, but is not viremic at the time of testing.

The main idea is that a positive nasal swab means the horse is shedding the virus through respiratory secretions, making it contagious to others. A negative blood sample indicates there is no detectable virus in the bloodstream at that moment, so there isn’t viremia. Latent infection wouldn’t typically show up as nasal shedding, and recovery with the horse still mingling would not involve active shedding. Viremia would be indicated by virus in the blood, which isn’t present here. So, the interpretation is that the horse is actively shedding the virus, posing a transmission risk, but is not viremic at the time of testing.