Lecture 9- Bovine Infectious Infertility and Abortion

Learning objectives for infectious infertility

Discuss pathophysiology, characteristics, clinical signs, diagnosis, and treatment of T. foetus, Brucella abortus, Listeria, H. somnus, Mycoplasma/Ureaplasma, IBR, BVDV, Bluetongue, Aspergillus fumigatus

Tritrichomonas foetus morphology

Flagellate protozoa; 3 anterior + 1 posterior flagellum; pyriform shape (lecture: “3 anterior and 1 posterior flagellum”)

T. foetus habitat

Preputial crypts (older bulls); vagina/uterus of cows

T. foetus pathogenesis

Coitus → vaginal infection → uterus; does not prevent conception; causes fetal loss; usually EED; bulls are reservoirs

T. foetus herd-level signs

Reverse stair-step infertility; conception then return to heat at 60–90 days; prolonged interestrus; early abortions; abortions rarely past 150 days; postcoital pyometra

T. foetus diagnosis in bulls

Preputial scraping or pipette aspiration → Diamond’s media or InPouch → culture; bulls infected for life → cull

T. foetus diagnosis in cows

Repeat breeders; fetal fluids (amnion/abomasum); uterine contents; cervico-vaginal mucus

T. foetus treatment/control

Test & cull; sexual rest ≥3 cycles; breed to uninfected bulls; quarantine; use AI; use only culture-negative or <4-year-old bulls; maintain tight breeding season; TrichGuard vaccine shortens recovery but does not prevent disease

Brucella abortus characteristics

Gram– coccobacillus; intracellular; zoonotic; causes undulant fever in humans; abortions in last half of gestation

Brucella abortus transmission

Mucous membranes → lymph nodes → bacteremia → uterus → trophoblast infection → fetal bacteremia → chorioallantoic necrosis → abortion; abortion products major transmission route

Brucella abortus bull involvement

Bulls may have epididymitis/orchitis; not commonly transmitted by coitus; can be transmitted via frozen semen

Brucella abortus clinical signs

Abortion after 5th month; RFM; metritis; weak calves that die soon after birth

Brucella abortus diagnosis

Placentitis; intercotyledonary areas dry/thickened/cracked (“Moroccan leather”); isolate organism from fetal lung/abomasum, uterus, placenta

Brucella abortus control

Reportable; no treatment; routine serology; vaccinate heifers (Bangs, RB51); purchase only from certified Brucellosis-free herds

Listeria monocytogenes characteristics

Gram+ coccobacillus; causes encephalitis, abortion, neonatal disease; found in rotting hay/improper silage; predilection for fetoplacental tissues; abortions in last trimester

Listeria pathogenesis

Ingestion → replication in monocytes/macrophages → placenta → placentitis + fetal septicemia → abortion; fetus retained for days → autolysis

Listeria clinical signs

Sick cows before/during/after abortion; fever; weight loss; RFM

Listeria diagnosis

Isolation of organism from fetal tissues or placenta

Listeria lesions

Autolyzed fetus; necrotic foci in liver (similar to BHV‑1); pinpoint yellow necrotic foci on cotyledon tips; intercotyledonary placentitis

Listeria prevention

Proper silage storage; clean wet hay rings; avoid feeding rotten material to pregnant animals

Haemophilus somnus reproductive role

Causes weak calves/stillbirths more than abortion; controversial infertility role; pure culture needed; common vaginal inhabitant; not major cause

Mycoplasma/Ureaplasma reproductive role

Granular vulvovaginitis; salpingitis → infertility; early/late abortions; uncommon/sporadic; present in normal tract; diagnosis must be cautious

Chlamydia/Salmonella

Uncommon causes of bovine abortion

IBR (BHV‑1) characteristics

Enveloped herpesvirus; latency; venereal and systemic forms; airborne transmission possible; most common viral abortion cause in North America

IBR venereal form transmission

Coitus; instruments; semen

IBR venereal form signs

Pustules, nodules, ulcers, erosions on vulva/penis

IBR systemic form pathogenesis

Naïve cow → mucous membrane exposure → viral replication → fetal infection → abortion; abortion storms (25–60% abort); abortions at 4–8 months; MLV vaccine can cause abortion

IBR diagnosis

Autolyzed fetus; necrotic foci in liver/other organs; IHC; intranuclear inclusion bodies; viral isolation confirms

IBR control

Venereal lesions resolve in 1–2 weeks; biosecurity; vaccination; AI with negative semen

BVDV characteristics

ssRNA enveloped virus; genotypes BVDV1 & BVDV2; biotypes cytopathic vs noncytopathic (PI calves always noncytopathic)

BVDV vertical transmission

Creates PI calves; fetal outcomes depend on gestational timing: EED, resorption, abortion, congenital defects, PI formation (infection before day 120–150)

BVDV congenital defects

Microencephaly; cerebellar hypoplasia; hydranencephaly; hydrocephalus; alopecia (lecture images)

BVDV horizontal transmission

PI animals shed high viral loads; prevalence 0.2–4%; acutely infected animals shed 2 days–2 weeks

Sources of PI calves

PI cows → PI calves; fetal infection before day 120–150

PI clinical features

Ill-thrift; intermittent diarrhea; chronic respiratory disease; most show no signs

PI diagnostic confirmation

Virus neutralization negative on two tests 14 days apart; virus isolation positive ≥14 days

BVDV economic impacts

Decreased conception; abortions; stillborn; weak calves; ovarian pathology; decreased weight gain; decreased immunity; decreased milk production

BVDV diagnosis

Virus isolation (gold standard); IHC on ear notch; PCR (pooled samples; low specificity → false positives); ELISA similar to VI

BVDV control

Biosecurity; closed herd; avoid stockyards; quarantine/test new entries; vaccinate; implement PI detection/elimination strategy

Bluetongue virus characteristics

Orbivirus; transmitted by Culicoides; minor abortion cause; teratogenesis more common (cerebral malformations, weak calves, stillborns); difficult diagnosis; only MLV vaccines (may propagate disease if vectors present)

Aspergillus fumigatus characteristics

Causes ~70% of fungal abortions; winter/spring confinement increases exposure; ingestion → hematogenous spread → placentitis → abortion

Aspergillus lesions

Placenta: necrotic cotyledons, thickened intercotyledonary space; fetus: mycotic skin plaques (~25%), resemble ringworm

Aspergillus diagnosis

Fungal hyphae on microscopy or histopath