Equine herpesviruses. 6. Sequential infection of horses with types 2, 3 and 1.

The research investigates the immunological and virological reactions of three foals to sequential infection with different Equine Herpesviruses (EHV) – specifically EHV2, EHV3, and EHV1. The results observed provide a hint that a recent prior infection with EHV2 and/or EHV3 might provide some level of protection against EHV1.

Understanding the Methodology

• In this study, scientists established the immunological and virological baseline of three foals regarding Equine Herpesviruses (EHV).
• Later, these foals were sequentially infected with three different strains of the virus: EHV2, EHV3 and EHV1. The term ‘sequentially’ in this context means one after the other in the order specified.

Observations from the Infection with EHV2

• After the experimental infection with EHV2, no signs of disease were observed in any of the studied foals. The lack of observable clinical symptoms may give an insight into how EHV2 affects healthy foals.

Impact of EHV3 Infection

• Upon EHV3 infection within the genital tract, the foals developed lesions on the mucous membrane and perineal skin. These symptoms were recognized as typical outcomes of equine coital exanthema, a sexually transmitted disease in horses caused by this strain of EHV.
• Furthermore, when EHV3 was introduced into their systems via the nasal pathway, the researchers identified extensive ulceration and the formation of pustules on the nasal mucosa by day 5. This was then followed by the release of a considerable amount of thick, pus-filled nasal discharge by the seventh day. On the eighth day, pustular skin lesions were visible around the exterior of the nostrils.

Reactions to EHV1 Infection

• The signs of disease after EHV1 infection in two of the three foals were milder than anticipated. This raised the possibility that prior infection with EHV2 and/or EHV3 might have a protective effect against EHV1.
• This observation also suggests that the immune response triggered by the previously encountered strains of EHV could potentially lower the severity of symptoms caused by EHV1, presenting an interesting avenue for further research.