title: Transplacental infection and apparently immunotolerance induced by a wild-type bluetongue virus serotype 8 natural infection.
abstract: Until recently, bluetongue (BT) virus (BTV) serotypes reportedly causing transplacental infections were all ascribed to the use of modified live virus strains. During the 2007 BT epidemic in Belgium, a significant increase in the incidence of abortions was reported. A study including 1348 foetuses, newborns and young animals with or without suspicion of BTV infection, was conducted to investigate the occurrence of natural transplacental infection caused by wild-type BTV-8 and to check the immunocompetence of newborns. BTV RNA was present in 41% and 18.5% of aborted foetuses from dams with or without suspected BTV involvement during pregnancy, respectively. The results of dam/calf pairs sampled before colostrum uptake provide evidence of almost 10% transplacental BTV infection in newborns. Apparently immunotolerant calves were found at a level of 2.4%. The current study concludes that the combined serological and real-time PCR (RT-qPCR) result of pregnant dams gives no indication of the infection status of the offspring except in the case of a double negative result. In a group of 109 calves with clinical suspicion of BT, born during the vector-free period, 11% were found to be RT-qPCR positive. The true prevalence was estimated to be 2.3%, indicating the extent of transplacental infection in a group of 733 calves of one to 4 months of age without BT suspicion. Moreover, virus isolation was successful for two newborn calves, emphasizing the need for restricting trade to BT-free regions of pregnant dams possibly infected during gestation, even if they are BTV RT-qPCR negative.
authors.affiliation: Veterinary and Agrochemical Research Centre, Department of Virology, Brussels, Belgium. kris.de.clercq@var.fgov.be
authors.forename: K
authors.initials: K
authors.lastname: De Clercq
authors.forename: I
authors.initials: I
authors.lastname: De Leeuw
authors.forename: B
authors.initials: B
authors.lastname: Verheyden
authors.forename: E
authors.initials: E
authors.lastname: Vandemeulebroucke
authors.forename: T
authors.initials: T
authors.lastname: Vanbinst
authors.forename: C
authors.initials: C
authors.lastname: Herr
authors.forename: E
authors.initials: E
authors.lastname: Méroc
authors.forename: G
authors.initials: G
authors.lastname: Bertels
authors.forename: N
authors.initials: N
authors.lastname: Steurbaut
authors.forename: C
authors.initials: C
authors.lastname: Miry
authors.forename: K
authors.initials: K
authors.lastname: De Bleecker
authors.forename: G
authors.initials: G
authors.lastname: Maquet
authors.forename: J
authors.initials: J
authors.lastname: Bughin
authors.forename: M
authors.initials: M
authors.lastname: Saulmont
authors.forename: M
authors.initials: M
authors.lastname: Lebrun
authors.forename: B
authors.initials: B
authors.lastname: Sustronck
authors.forename: R
authors.initials: R
authors.lastname: De Deken
authors.forename: J
authors.initials: J
authors.lastname: Hooyberghs
authors.forename: P
authors.initials: P
authors.lastname: Houdart
authors.forename: M
authors.initials: M
authors.lastname: Raemaekers
authors.forename: K
authors.initials: K
authors.lastname: Mintiens
authors.forename: P
authors.initials: P
authors.lastname: Kerkhofs
authors.forename: N
authors.initials: N
authors.lastname: Goris
authors.forename: F
authors.initials: F
authors.lastname: Vandenbussche
mesh_terms: D000034:Abortion, Veterinary / Q000821:virology*; D000818:Animals; D000831:Animals, Newborn; D001530:Belgium / Q000453:epidemiology; D001819:Bluetongue / Q000453:epidemiology / Q000635:transmission*; D001820:Bluetongue virus / Q000302:isolation & purification* / Q000472:pathogenicity; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000635:transmission*; D005260:Female; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D012367:RNA, Viral / Q000032:analysis; D012703:Serotyping / Q000662:veterinary
chemical_list: D012367:RNA, Viral