7: Bovine Abortions Flashcards
What are diseases that cause late term abortions?
BHV-1, Mycoses, Brucellosis, Lepto, Opportunistics, Neospora, Epizootic Bovine Abortion
What are diseases that can cause abortions at any time?
Ureaplasma, mycoplasma
BVD, bluetongue, Listeria
Three mechanisms of hematogenous abortion:
Infect fetus directly through umbilical veins
Infect fetus indirectly through contamination of amnionic fluid from primary placental infection
Hypoxia via placentitis (no fetal infection)
Two main routes of abortifacient infection:
Hematogenous dam-> placenta
Ascending infections from vagina through cervix
When do losses due to campylobacter occur?
Majority 30-70d
Occasionally at 4-8 mo
Campylobacter mechanism:
Heat-stable endotoxin-> placentitis-> fetal hypoxia
Mollicute infection abortion presentation:
EED/Abortion/Stillbirth/Weak calves/Neonatal pneumonia
Retained fetal membranes common
White-brown exudate and thickened, fibrotic, necrotic, amnion & chorioallantois
Mollicute infection tx:
Macrolide abx
Mollicute transmission:
Venereal or respiratory
Likes mucosal/serosal surfaces
When do opportunistic infections cause abortion:
2nd half of gestation
variable presentation
Dx of exclusion
Where is epizootic bovine abortion more common?
California, Oregon, Nevada
“Foothill Abortion”
What is the mechanism of Epizootic bovine abortion?
Tick borne
Replication in histiocytes-> fetal stress-> parturition induction
SLOW infection
When are cattle susceptible to EBA and when does it cause abortions?
Susceptible mid-gestation (60-140d)
Abortions in 3rd trimester
Mechanism of brucellosis abortions:
Penetrates resp. mucosa-> localizes in lymph nodes-> bacteremia-> uterus-> trophoblast necrosis and chorioallantoic ulcertation (placentitis)-> fetal bacteremia
Gross pathology associated with brucellosis abortions:
Moroccan leather placenta (dry, thickened, cracked) may be covered in yellowish exudate
What does brucellosis cause in cows?
Spontaneous late term abortions, premature calving, infertility
Compare Lepto serovars hardjo and pomona on terms of timing and abortion rates:
Pomona: higher abortion rate (50%); 3rd trimester abortions; 1-6 wk post infection
Hardjo: <10% abortion rates; 2-3rd trimester abortions; 4-12 wk post infection
Mechanism of leptospirosis abortions:
Infection-> 4-10d incubation-> bacteremia-> localizes/persists in repro & kidneys-> persistent shedding in urine & repro fluids-> May deliver weak infected calves or autolyzed/icteric fetus
Presentation of Lepto abortions:
Weak infected calves
Autolyzed & icteric
Diffuse cotyledonary necrosis
RFM common
Mechanism of listeria abortions:
Spoiled silage consumption-> hematogenous spread to placenta (5-12 days)-> fetal septicemia
Timing of listeria abortions:
Early third trimester- retained for a few days
Or near full term; less autolysis
Presentation(s) of listeria abortions:
Early 3rd trimester- severe autolysis
Near term- dam metritis, septicemia, dystocia, RFM; less autolysis, multifocal cotyledonary necrosis, intercotyledonary placentitis, fibrinous polyserositis & white necrosis of liver/spleen
Mechanism of BVDV abortion:
Oronasal inoculation-> replicates in tonsils & resp tract-> disseminated to other epithelial/lymphoid tissues-> transplacental infection
Infection of BVDV at <40d:
Decreased conception rate/EED
Oophoritis, salpingitis, hormone alteration
Infection of BVDV at 40-125 days:
Pregnancy loss or PI animal (non-cytopathic)
Infection of BVDV at 100-150 days:
Congenital malformations
Cerebellar hypoplasia, hydranencephaly, hydrocephalus, porencephaly, microcephaly, ocular changes
Infection of BVDV >125 days:
Abortions rare
Clinically normal calf with high antibodies
Bluetongue vector:
Biting midge
Cullicoides variipennis
Bluetongue mechanism:
inoculation-> LN replication-> hematogenous spread-> cell damage/thrombosis
Bluetongue infection at <70d:
fetal death/absorption
Bluetongue infection at 70-130d:
Stillbirth, weak calves, hydrancephaly, abortion
Bluetongue infection at >150 days:
premature birth +/- encephalitis
Sources of IBR:
Nasal exudates, cough droplets, preputial secretions, semen, fetal tissues/fluids
IBR abortion mechanism:
Infection of non-immune pregnant females-> viremia-> rapid fetal infection-> abortion
Timing of IBR abortions:
most common between 4 and 8 months
Presentation of IBR abortions:
Variable autolysis
White-tan foci on liver/lungs
Edematous placenta
Horizontal transmission of neospora:
cattle ingest oocysts
Exogenous transplacental transmission of neospora:
naive animal ingests oocysts while pregnant; passes to fetus
Endogenous transplacental transmission of neospora
latent infection reactivates during pregnancy and is passed to the fetus
When do neospora abortions occur?
2nd trimester 5-6 mo
Mechanism of neospora abortions:
disorder of fetoplacental unit following maternal parasitemia
Parasite invades & damages placental villi
Most common cause of mycotic abortions:
Aspergillus fumigatus
timing of abortions from mycoses:
sporadic, late term
Mechanism of mycotic abortions:
Resp/GI introductions-> bloodstream-> placental necrotizing vasculitis with thrombosis-> placental insufficiency-> abortion
Placenta frequently retained
What infectious abortifacients do we not have a vaccine in the US for?
Bluetongue
Neospora
Mycotics
Listeriosis
What is in a commercial 5-way vaccine
BVD (x2), BHV-1, BRSV, PI3
What is in a commercial 10-way vaccine?
BVD, BHV-1, BRSV, PI3, Campy, Lepto
