Equine herpesviruses. Experimental infection of a foetus with type 2.

This research article focuses on the effects of equine herpesvirus type 2 (EHV 2) on a horse fetus from conception to birth and then after birth. The primary conclusion is that the intrauterine infection did not lead to abortion, stillbirth, or any visible disease, although the presence of EHV 2 was confirmed and led to a mild clinical disease after birth.

Experiment Set-Up and Inoculation Process

• Researchers purposely infected a pregnant mare with equine herpesvirus type 2 (EHV 2) to observe its impact on the fetus.
• Two methods were used to confirm the infection was established in the uterus: allantocentesis and amniocentesis, where fluid samples were collected from the uterus 107 days after inoculation.

Observations and Findings at Birth

• The studies revealed that the infection did not lead to any severe outcomes such as abortion, stillbirth, or any visible disease.
• The virus was cultured from separate samples of allantoic and amniotic fluid taken 156 days after inoculation during a chosen Caesarean section.
• Additionally, antibodies capable of neutralizing the EHV 2 virus were found in the foal’s presuckle serum at birth, indicating that the immune system of the newborn was already working against the virus.

Post-Birth Observations and Further Findings

• After the foal’s birth, a very mild clinical disease manifested between the fourth and eleventh days. The disease was hardly noticeable, characterized by a trivial mucus-like oculo-nasal discharge.
• The presence of EHV 2 was confirmed through 22 nasal swabs taken between birth and day 65, providing further proof that the virus was ongoing.
• On the 65th day, the foal was also infected with the equine adenovirus. However, the research doesn’t clarify whether this was due to the initial EHV 2 infection or occurred independently.
• From day 66 to day 71, six nasal swabs were taken, but none of them tested positive for EHV2, implying that the foal had successfully cleared the initial infection or that the virus was undetectable at the time of these tests.