# Demonstration teaching case: An abortion storm in a beef cow-calf herd

Created by AI under faculty supervision for demonstration only. Not a scientific reference; verify important information before teaching or clinical use. Fictional herd and people. Clinical statements are linked to the sources listed at the end ([n]); items marked VERIFY were not independently confirmed.

## Learning objectives (for veterinary students)
1. Recognize when an abortion rate in a beef herd warrants a diagnostic investigation.
2. Select appropriate samples from the fetus, placenta, aborting dams, and herdmates.
3. Interpret leptospiral serology in maintenance-host versus incidental-host infections.
4. Build a herd-level plan that combines treatment, vaccination, and environmental control.
5. Communicate zoonotic risk and protective measures to the producer and farm workers.

## Signalment and setting
- Commercial cow-calf operation in the southeastern United States; about 85 Angus-cross cows on mixed pasture; fall-calving season.
- Late summer, after several weeks of heavy rain. Cattle drink from a pond and a slow creek with muddy margins.
- The owner (Jim Miller, 58, third-generation rancher) has seen feral hogs along the creek at night "more than ever this year."
- Vaccination: replacement heifers receive a respiratory vaccine; the cows' last reproductive vaccine (owner unsure which) was "two or three years ago." No leptospirosis booster since. VERIFY plausibility.
- No new cattle purchased this year; natural service with the same three herd bulls for three seasons (about 25-30 cows per bull; typical guidance is about 25 cows per mature bull [6]).
- Vaccination timing for this case: no vaccine is given until after the second (paired) blood sample, so the serology is not confounded by new vaccination [7].

## Presenting complaint (what the owner reports)
- Six cows aborted in the past five weeks, all in late gestation; two more calved early with weak calves, one of which died.
- 80 cows were confirmed pregnant before these losses, so 6 abortions = 7.5% (the two premature births are counted separately). In beef herds an abortion investigation is generally recommended when the abortion rate exceeds approximately 3-5% [1].
- Two heifers were "off feed for a day or two" with no other obvious signs.
- One weak calf had dark red urine and rapid breathing before it died. Severe disease with high fever, weakness, red urine, and rapid breathing from anemia is described in calves infected with incidental serovars, especially Pomona [2].
- The owner's adult son helped pull a weak calf and handled two aborted fetuses bare-handed; he had a flu-like illness with headache and muscle aches last week (human health: refer to a physician; do not diagnose).

## Findings on the farm visit (fictional, consistent with sources)
- Aborting cows: bright and eating; no fever at the visit. Retained fetal membranes in one cow. Retained membranes may follow leptospiral abortion [2].
- The most recent fetus (refrigerated by the owner, about 24 hours old) is autolyzed with mild icterus. Placenta: diffuse placentitis with avascular, light tan cotyledons and edematous, yellowish intercotyledonary areas [1]. Fetuses infected with Pomona may show icterus; lesions are not specific [1].
- No ringworm-like skin lesions on the fetus. This does not rule out mycotic abortion, because only about 25% of mycotic-aborted fetuses have them; placental histopathology and fungal testing are needed [1].
- Pond margins trampled and muddy; hog wallows along the creek.

## Differential diagnoses (late-gestation abortion in beef cattle) [1]
- Leptospirosis (incidental serovar such as Pomona, or Hardjo)
- Bovine viral diarrhea virus (BVDV)
- Infectious bovine rhinotracheitis (BoHV-1): abortion typically 4-7 months, often after respiratory disease
- Neosporosis: most common at 4-6 months of gestation
- Mycotic abortion: necrotizing placentitis; about 25% of fetuses have ringworm-like skin lesions
- Listeriosis, chlamydiosis. (Epizootic bovine abortion and ponderosa pine toxicity are western US problems and unlikely in this southeastern herd without that exposure [1].)
- Brucellosis: late-term abortion; largely eliminated from US domestic cattle, with occasional cases linked to wildlife in the Greater Yellowstone area; it remains a reportable disease [1][8].
- Trichomoniasis and Campylobacter venerealis are less likely: Trichomonas causes abortion mainly in the first half of gestation [1].

## Diagnostic plan (what a strong student orders) [1][2]
- Fetus and placenta to a diagnostic laboratory for necropsy and histopathology, submitting both chilled fresh tissues and formalin-fixed tissues [9]. Fluorescent antibody staining or PCR for Leptospira; fetal spleen for BVDV; fetal brain, heart, and kidney for Neospora; fetal tissues for BoHV-1; abomasal contents for bacterial culture.
- Paired serum samples (at least 1 week apart) from aborting cows and some herdmates: Leptospira microscopic agglutination test (MAT), BVDV and BoHV-1 titers.
- Urine from aborting cows within 2 weeks after abortion for Leptospira PCR [1][2].

## Results (fictional)
| Test | Result |
|---|---|
| Fetal kidney PCR, pathogenic Leptospira | Positive |
| Fetal tissues, fluorescent antibody | Positive |
| Fetal spleen BVDV PCR | Negative |
| Fetal brain and heart, Neospora IHC | Negative |
| Fetal tissues, BoHV-1 PCR | Negative |
| Abomasal contents culture | No significant growth |
| Dam MAT, Pomona: first sample | 1:1600 |
| Dam MAT, Pomona: 2 weeks later | 1:6400 (fourfold rise) |
| Dam MAT, Hardjo | 1:100 (both samples) |
| Herdmates MAT, Pomona (5 cows) | 1:400 to 1:3200 |
| Urine PCR, pathogenic Leptospira | Positive in 2 of 5 aborting cows |

Interpretation: a rising titer is diagnostic for incidental infections such as Pomona [2]; an initial titer above 1:800 is suspicious [1]. Hardjo titers can stay low because cattle are its maintenance host, and about one-third of cows aborting from Hardjo have titers below 1:100 at abortion [1][2]. Vaccination confounds serology because tests cannot distinguish vaccine from infection antibodies [2]. Final diagnosis: abortion storm due to leptospirosis, confirmed by detection in fetal tissues. Serovar Pomona is presumptive: PCR and fluorescent antibody tests do not identify the serovar, and MAT titers can cross-react [7]. Water contaminated by feral swine or wildlife urine is the leading exposure hypothesis [2], not a proven source; confirmation would need organism characterization and epidemiologic evidence.

## Management plan [1][2]
- Work with the herd veterinarian under a valid veterinarian-client-patient relationship. Treatment options reported to reduce clinical signs and stop urinary shedding include oxytetracycline, tilmicosin, ceftiofur, and amoxicillin; some dosages are extralabel [1]. Long-acting oxytetracycline is commonly used to clear kidney infection [2]. In the US, extralabel drug use in food animals must follow FDA rules (AMDUCA), and cephalosporins such as ceftiofur may only be used at an approved dose, frequency, duration, and route for that class of cattle; extended withdrawal times cannot make a prohibited use legal [10]. (No doses shown in this case on purpose.)
- Vaccinate the whole herd with a multivalent leptospirosis vaccine (often labeled L5: Canicola, Grippotyphosa, Hardjo, Icterohaemorrhagiae, Pomona) [2]; cross-protection among serovars is very little or absent [1]. Heifers: two doses 4-6 weeks apart before breeding, then annual boosters [1]. Infected cattle should be treated before vaccination is expected to be effective [2].
- Environment: fence off the pond margins and swampy areas, provide clean water, keep urine out of feed, and work on feral swine and rodent control [2].
- People: wear rubber boots, waterproof clothing, gloves, and eye protection when handling fetuses, placentas, or urine; cover cuts; wash hands [3]. The son already has symptoms, so he should get prompt medical evaluation and tell his clinician about the cattle exposure; diagnosis and treatment are for his physician [11].
- Check with the state veterinarian about reporting requirements for abortion storms and leptospirosis in livestock; they vary by state. VERIFY for the state used in teaching.

## Virtual client facts (what Jim Miller knows and reveals only when asked)
| Topic | What the client says |
|---|---|
| Opening | "We've lost calves, Doc. Six cows slipped them in the last five weeks, most of them late along." |
| Timing in pregnancy | "Most were pretty close to calving. A couple were maybe two months out." |
| Calves born alive | "Two came early. Weak. One had dark red pee and was breathing hard before it died." |
| Sick cows | "A couple of heifers went off feed for a day or two. Nothing I'd call sick." |
| Cows after aborting | "They seem fine. One held her afterbirth." |
| Vaccines | "Heifers get a shot for shipping fever. The cows got a reproductive shot two, three years back. I don't remember the name." |
| Water | "Pond and the creek. With all the rain the edges are just mud." |
| Wildlife | "Hogs. Feral hogs all along the creek this year. Coons and possums too." |
| New animals | "No new cattle. Same three bulls three years running." |
| Feed | "Grass and a little hay. Hay looked fine." |
| Breeding | "Natural service. Three bulls in with the cows." |
| People | "My boy pulled a calf and moved two of the dead ones. He was down with a fever and achy last week." |
| Records | "I've got the dates written in my book." |
| Asks for diagnosis | "That's what I'm paying you to tell me. I just can't afford to lose more calves." |

## References
1. Ciccarelli M. Abortion in Cattle. MSD Veterinary Manual. Full review Sept 2026. https://www.msdvetmanual.com/reproductive-system/abortion-in-large-animals/abortion-in-cattle
2. Arnold M. Reproductive Failure in Cattle: Frequently Asked Questions about Leptospirosis. Ohio BEEF Cattle Letter, OSU Extension, Dec 2022. https://u.osu.edu/beef/2022/12/14/reproductive-failure-in-cattle-frequently-asked-questions-about-leptospirosis/
3. Centers for Disease Control and Prevention. About Leptospirosis; Leptospirosis Fact Sheet for Clinicians. https://www.cdc.gov/leptospirosis/about/index.html
4. Ellis WA. Animal leptospirosis. Curr Top Microbiol Immunol. 2015;387:99-137. PMID 25388134. https://pubmed.ncbi.nlm.nih.gov/25388134/
5. Sykes JE, et al. A global one health perspective on leptospirosis in humans and animals. J Am Vet Med Assoc. 2022;260(13). https://avmajournals.avma.org/view/journals/javma/260/13/javma.22.06.0258.xml

6. University of Nebraska-Lincoln Extension. Bull management guidance (G2332). https://extensionpubs.unl.edu/publication/g2332/2021/pdf/view/g2332-2021.pdf
7. World Organisation for Animal Health. Terrestrial Manual, Chapter 3.1.12 Leptospirosis. https://www.woah.org/fileadmin/Home/eng/Health_standards/tahm/3.01.12_LEPTO.pdf
8. USDA APHIS. Bovine brucellosis. https://www.aphis.usda.gov/livestock-poultry-disease/cattle/bovine-brucellosis
9. Cornell Animal Health Diagnostic Center. Bovine diagnostic plans and panels. https://www.vet.cornell.edu/animal-health-diagnostic-center/diagnostic-services/diagnostic-plans-and-panels/bovine-diagnostic-plans-and-panels
10. US FDA. Cephalosporin order of prohibition: questions and answers. https://www.fda.gov/animal-veterinary/antimicrobial-resistance/cephalosporin-order-prohibition-questions-and-answers
11. CDC. Clinical overview of leptospirosis. https://www.cdc.gov/leptospirosis/hcp/clinical-overview/index.html

Review log: veterinary review by Codex (gpt-6.1-sol, acting as a skeptical large-animal reviewer) on 2026-10-22; all 10 issues accepted and applied by Claude. Sources 6-11 were suggested by that review; Pedro to spot-check.

## Images (public domain, CDC PHIL via Wikimedia Commons)
- `images/leptospira-sem-cdc-phil138.jpg`: scanning electron micrograph of Leptospira. Credit: CDC/Rob Weyant, PHIL #138.
- `images/leptospira-interrogans-cdc-phil1220.png`: Leptospira interrogans. Credit: CDC/NCID/HIP/Janice Carr, PHIL #1220.