Bovine Abortion: Deciding What to Submit
A 400-cow dairy herd experiences 6 late-gestation abortions over 3 weeks, all between 7 and 8.5 months gestation. Cows are otherwise clinically normal; milk production is stable. The herd is vaccinated against BVDV and IBR, and the owner reports no new animals in 6 months. Two aborted fetuses were found fresh; one placenta was retained and appears thickened with pale cotyledons. The referring veterinarian has limited budget and asks which samples give the most diagnostic yield. Neospora, Brucella, and BVDV are on the differential list.
1. Given the cluster and the limited budget, what is your prioritized sample set and why?
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Prioritized sample set (highest yield per dollar):
- Fresh placenta (cotyledon and intercotyledonary tissue) - the thickened pale cotyledons are a strong clue. Submit chilled for culture (Brucella, Campylobacter, Salmonella, Listeria) and fixed in formalin for histology. Placenta is often the most rewarding tissue in bovine abortion.
- Fetal stomach content and lung - chilled for bacterial culture and PCR (BVDV, Neospora caninum).
- Fetal brain and heart - fixed in formalin; brain for Neospora cysts and nonsuppurative encephalitis, heart for myocarditis (Neospora, BVDV).
- Fetal liver and spleen - fixed plus fresh for culture.
- Dam serum - paired or single sample for Brucella (if not vaccinated) and Neospora serology; BVDV PCR on dam blood if indicated.
Rationale: a cluster of late-gestation abortions with a visibly abnormal placenta points toward an infectious cause with placental tropism (Brucella, Neospora, BVDV, or fungal). Culturing placenta and fetal stomach plus PCR on fresh tissue covers the top differentials. Formalin-fixed brain and heart are cheap and add Neospora/BVDV diagnostic power.
What to skip under budget pressure: whole-fetus submission is expensive; targeted tissues suffice.
2. The placenta shows necrotizing placentitis with intralesional coccoid organisms, and fetal lung culture grows a Gram-negative coccobacillus. How do you interpret this and what is the herd-level implication?
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Interpretation: necrotizing placentitis with intralesional organisms plus a Gram-negative coccobacillus from fetal lung is highly suggestive of Brucella abortus (or another Gram-negative abortifacient such as Campylobacter fetus or Salmonella). Brucella is the priority given zoonotic and regulatory significance.
Immediate actions:
- Notify the regulatory authority - Brucella abortus is reportable in most jurisdictions; do not delay.
- Confirm with culture/PCR at a reference laboratory; serology on the dam and herd.
- Handle tissues with biosafety precautions - zoonotic risk to veterinarians and staff.
Herd-level implications:
- A confirmed Brucella diagnosis triggers a herd investigation, movement restrictions, and a test-and-remove or vaccination strategy depending on jurisdiction.
- If Brucella is excluded, the Gram-negative coccobacillus could be Campylobacter or Salmonella, which have different control strategies (hygiene, water, feed).
Pathologist's role: report the morphologic diagnosis and organism description clearly, flag the zoonotic/regulatory concern in the report, and recommend confirmatory testing rather than over-interpreting a single culture.