USE OF TRANSABDOMINAL ULTRASOUND-GUIDED AMNIOCENTESIS FOR DETECTION OF EQUID HERPESVIRUS 1-INDUCED FETAL INFECTION IN-UTERO

Objective-To evaluate transabdominal ultrasound-guided amniocentesis f or detection of equid herpesvirus 1 (EHV-l)-induced fetal infection in utero. Animals-4 Welsh Mountain mares. Procedure-Pregnant mares were inoculated intranasally with EHV-1 during the ninth month of gestation . Amniocentesis was initiated on postinoculation day (PID) 12, and was performed at 2- to 3-day intervals in standing mares under deep sedat ion. Amniotic fluid samples were tested by virus isolation (VI), polym erase chain reaction (PCR), and immunoperoxidase cytologic examination (IC) for detection of EHV-1. Results-Exposure to EHV-1 in the ninth m onth of gestation resulted in nasal shedding of infective virus, estab lishment of cell-associated viremia, and seroconversion. Equid herpesv irus 1 was detected by VI, PCR, and IC in amniotic fluid collected on PID 14 from 1 mare and on PID 16 and 17 from a second mare. Specimens of amniotic fluid from a third mare were VI negative until PID 18, whe n collections ceased, although this mare subsequently aborted an EHV-l -infected fetus on PID 28. The fourth mare aborted an EHV-1 infected f etus on PID 14. The 2 mares with VI-positive amniotic fluid were each carrying an EHV-1 infected fetus in utero, confirmed by examination of the uterus, placenta, and fetus, using specific immunohistochemistry and in situ hybridization. Endothelial cells in the endometrium and al lantochorion were often virus-infected, with accompanying vascular les ions. The fetus had been infected via the chorionic vasculature in the first and fourth mares, and by inhalation of infected amniotic fluid in the second mare. Conclusion-Amniocentesis permits specific detectio n of EHV-l-induced fetal infection in utero. Clinical Relevance-Amnioc entesis may have a clinical role in the specific identification and is olation of mares carrying virus-infected fetuses during EHV-1-induced abortion epizootics.