Experimental infection of pregnant ewes with bovine viral diarrhea virus type-2 (BVDV-2): effects on the pregnancy and fetus.
The reproduction effects of bovine viral diarrhea virus type-2 (BVDV-2) infection were investigated in ewes inoculated with a non-cytopathic BVDV-2 isolate at three stages of gestation. Virus inoculation was followed by a transient viremia, accompanied by a transient and mild hyperthermia and nasal discharge in a few animals. Some ewes were sacrificed at different time-points after virus inoculation to study the kinetics of fetal infection. Infectivity and viral antigens were detected in placentomes from day 7 to 36 post-inoculation (pi) and in fetal fluids and tissues between days 10 and 28 pi. Cardiac petechial hemorrhages and hemoperitoneum accompanied by a severe fibrinous ulcerative placentitis were observed in fetuses examined at days 21, 28 and 36 pi. Inoculation of ewes at days 55-60 of gestation resulted in a prolonged virus replication in placentomes and fetal tissues; ewes that were allowed to proceed with pregnancy had 77% of abortions or fetal and perinatal deaths. Seven stillbirths, unviable and viable lambs born to these ewes were virus-positive at birth. Infectious virus was repeatedly isolated from leukocytes of two lambs up to 2 and 6 months of age, indicating they were persistently infected. Ewes inoculated at days 65-70 of gestation had 66.6% of fetal and perinatal losses. Three viable lambs born to these ewes were healthy, BVDV antibody-positive and virus-negative. A transient viral replication in placentomes and in a few fetal tissues, followed by the rise of fetal neutralizing antibodies and virus clearance was the result of inoculating ewes at days 120-125 of gestation. Lambs born to these ewes were healthy, antibody-positive and virus-negative. These results demonstrate that the biology of BVDV-2 infection in pregnant sheep is essentially similar to that of BVDV-1 in pregnant cattle and sheep. These features make this species an attractive animal model for studying the pathogenesis of congenital BVDV-2 infection.
Departamento de Medicina Veterinária Preventiva (DMVP) e Departamento de Microbiologia e Parasitologia (DMP), Universidade Federal de Santa Maria (UFSM), 97105-900, RS, Santa Maria, Brazil.
C F
CF
Scherer
E F
EF
Flores
R
R
Weiblen
L
L
Caron
L F
LF
Irigoyen
J P
JP
Neves
M N
MN
Maciel
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000032:analysis; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000097:blood / Q000473:pathology* / Q000821:virology; D001938:Brazil; D002417:Cattle; D002540:Cerebral Cortex / Q000196:embryology / Q000473:pathology / Q000821:virology; D030242:Diarrhea Virus 2, Bovine Viral / Q000254:growth & development* / Q000276:immunology; D005260:Female; D005312:Fetal Blood / Q000821:virology; D005313:Fetal Death / Q000821:virology; D007150:Immunohistochemistry; D008297:Male; D010920:Placenta / Q000473:pathology / Q000821:virology; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000097:blood / Q000662:veterinary* / Q000821:virology; D011256:Pregnancy Outcome / Q000662:veterinary; D011897:Random Allocation; D012756:Sheep; D012757:Sheep Diseases / Q000473:pathology / Q000821:virology*
D000914:Antibodies, Viral; D000956:Antigens, Viral