Viruses of the genital tract + pregnant uterus Flashcards
Tranmission
horizontal + vertical
reproductive failure - causes
Viral replication in foetal tissues leading to
malformation or death
Damage to placental blood vessels leading to
interrupted blood supply to the foetus
Stress and pyrexia due to viral infection
combination of the above
equine herpes virus
EHV-1: abortions, respiratory disease, paralysis
EHV-3: causes genital pustules but not abortion
EHV-4: respiratory disease, very rarely isolated abortions
EHV-1
Abortion typically in last third of pregnancy
Lung oedema
Multifocal necrosis in liver, lungs and spleen
Abortion accompanies or occurs shortly after foetal
death
EHV-1 - diagnosis
Post mortem examination of fetus + placenta
Polymerase chain reaction (PCR) or virus isolation
Microscopic examination of tissue sections
EHV-1 immunostaining
EHV - prevention
Isolation of pregnant mares during last trimester
(disinfection of boots etc.)
Vaccination of all horses on the premises
Combination vaccines EHV-1 and EHV-4
EHV - control
In case of abortion isolate affected mare
Collect foetus and placenta for testing (antigen test) Paired serum samples from mare to test for rising
antibody titre (but interpretation difficult if mare
vaccinated against infection and also recrudescence due to stress of abortion can occur)
equine arteritis virus (EAV)
Arterivirus (Family Arteriviridae) Causes equine viral arteritis (EVA) Notifiable disease Last case in UK in 2012 Entry via respiratory tract or semen Infects macrophages and endothelial cells and causes arteritis
EAV abortion diagnosis
Clinical signs in mare: variable - fever, depression, conjunctivitis (‘pink eye’), abortion
Post mortem exam of aborted foetus and placenta – may detect virus
Virus-neutralising antibody levels in mare high at abortion or rising between paired post abortion titres
stallions persistently infected + shed in semen without clinical signs
investigate in travel Hx
EAV - problems in diagnosis
May be subclinical
Stallions can shed virus in semen intermittently or
persistently without showing clinical signs
Virus persists in accessory glands
Is not considered to persist in the mare
EAV - diagnosis + control
Diagnosis on aborted foetus or on semen samples
using virus isolation or PCR
Movement restrictions
Vaccination of stallions (confirm that he is antibody
negative before vaccination)
bovine viral diarrhoea (BVDV)
Pestivirus (Family Flaviviridae)
Shed in respiratory secretions and faeces
Transmission also via semen during AI
Virus replication in respiratory and enteric tract
Haematogenous spread to foetus via placenta
(equivalent in sheep is Border disease virus – hairy
shaker lambs)
BVDV - timing of infection
First trimester of pregnancy (0-110 days) prior to
immunocompetence - Embryonic/ foetal death – resorption/ abortion/mummification, Persistent infection (PI calf)
Second trimester (111-190 days) - Abortions/mummification, PIs usually only until ~ day 140, Congenital deformities (esp day 125-175)
Third trimester after day 191 - occasional abortions/ stillbirths/ weak calves, Predominately “normal” calf
BVDV - abortion diagnosis
Post mortem examination on aborted foetus with
PCR of lymphoid tissue (thymus/ spleen)
Histopathology with immunohistochemistry (esp.
brain tissue)
Foetal serology on free foetal fluids for indication of
exposure
Maternal serology (but can be difficult to interpret)
BVDV - prevention + control
BVDV is endemic in the UK
Vaccination of dams before pregnancy
Identify and remove persistently infected animals
(antigen test followed by second antigen test or antibody test)
Various European countries have eradication programs