Cattle Chat Podcast Summary

Episode: Guest Dr. Cassandra Olds: What is Theileria, How is Theileria Transmitted, Heifer Development
Date: December 12, 2025
Host/Panel: Brad White (A), Bob Larson (E), Scott (C), Jason (B), Dustin (F)
Guest: Dr. Cassandra Olds (D), Entomologist
Podcast: BCI Cattle Chat, Kansas State University Beef Cattle Institute

Episode Overview

This episode brings back Dr. Cassandra Olds to clarify listener questions about Theileria, a tick-borne parasite impacting cattle in the U.S. The team dives into Theileria’s emergence, transmission, challenges of management, and the state of immunity. The second half shifts focus to practical pre-breeding management of replacement heifers—highlighting why early pregnancy is critical and offering step-by-step strategies for herd success.

Main Discussion Points & Insights

1. Theileria in the U.S.: Emergence and Spread

• Timeline & Origin

  • Theileria was officially reported in the U.S. in 2017, but retrospective analysis found it present beforehand.
    • Dr. Olds: “The first official, official reports were 2017. But then when we went back and looked at old samples, it had been here for a while. ...Once an animal is infected, it's infected for life.” (05:01)

• Geographic Spread

  • Started on the East Coast, now moving west. Endemic status developing in states like Virginia.
    • Dr. Olds: “East coast has had it the longest... we'll get to the point where this is just...most places have it and it's fairly endemic.” (06:45)
  • Difficult to predict outbreaks due to variable responses even from the same cattle supplier year-to-year.

2. Transmission, Immunity, and Management

• Modes of Transmission

  • Primarily via ticks, stable flies, lice; persistently-infected carriers are common.
    • Dr. Olds: “Minimize your ectoparasites as much as possible, provide supportive care and reduce stress, good nutrition.” (08:55)

• Infection and Immunity

  • Early low-dose infection in calves generally promotes effective immunity; overwhelming infection (often linked to stress) triggers disease.
    • Dr. Olds: “If cattle can get infected when they're young, low dose...the immune response behaves appropriately.” (07:47)
    • “Any stress event can really cause this recurrence of disease.” (05:01)

• No Approved U.S. Treatments

  • “There is an approved drug out there, there's issues with it...Right now all it is is minimize your ectoparasites... and reduce stress, good nutrition.” (08:55)
  • Bupavacone used internationally, but not yet available in the U.S. Its main impact is “knocking back” the parasite enough for clinical recovery—not curing the infection (10:47, 11:29).

• Supportive/Anecdotal Therapies

  • Long-acting tetracycline sometimes reportedly helps, possibly by controlling secondary infections—but not Theileria itself.
    • “It may play a role. It's not going to save the animal, it's not going to do anything necessarily to the tularia, but it may just help it deal with everything else...” (09:44)

3. Challenges: Prevention, Transmission Control, and Herd Management

• Needle Sharing and Iatrogenic Spread

  • Practical impact of needle hygiene may depend on current herd infection rates (“knowing your herd’s status is key”).
    • Dr. Olds: “I think it comes down to knowing your herd infection rate. If everybody's infected, we're not making a whole lot of progress.” (15:01)

• Community Approach

  • Importance of involving veterinarians, sharing information, and collective problem-solving.
    • Dr. Olds: “We need to start thinking as a community, like how do we help bring everybody on this journey?” (12:42)

4. Heifer Development and Pre-Breeding Exams

• Why Pre-Breeding Exams Matter

  • The goal: Heifers get bred as early as possible, ensuring productivity for a lifetime.
    • Dr. Larson: “I just focus on getting heifers bred early... I want her to calve either before the calving season for the mature cows starts or very early in the calving season. ...If she calves the first part of that calving season, that sets her up for life…” (16:33, 22:54)

• Key Tools in Assessment

  • Weight: Directly linked to puberty; heavier heifers generally cycle sooner.
  • Reproductive Tract/Track Scores: Palpation to assess sexual maturity.
  • Pelvic Area Measurement: Useful mostly for catching rare outliers at high dystocia risk.
    • Dr. Larson: “Of the ways I assess heifers, probably pelvic area is the least important... But just every once in a while, you'll find that heifer that... her pelvic area is small. ...to find an oddball, it has a role there.” (20:47)

• Timing & Management

  • Assess 45-60 days pre-breeding to adjust nutrition or development plans as needed.
    • “Kind of a nice thing about doing a pre breeding exam that includes weight and a track score here, you know, 45 days ahead of the breeding season... I can make some adjustments and get them more [ready].” (19:32)

• Making Cull/Keep Decisions Efficiently

  • Market pressures (high heifer value) raise the stakes; only keep/breed those likely to thrive.
    • Dr. Larson: “If the ones I keep, I darn sure want them to get pregnant early.” (16:33)

Memorable Quotes & Timestamps

• On Theileria’s Elusive Nature:

  • Dr. Olds: “We’re a hair’s breadth away from chaos at any given point in time with these [immune responses].” (07:47)

• On Long-Term Herd Management:

  • Dr. Olds: “We will get to the point where all herds are infected and that for the most part it calms down. We just have to get over that initial hump.” (13:15)

• On Treatment Limitations:

  • Dr. Olds: “This horse is bolted. It’s not coming back to the stable.” (10:47)

• On Early Heifer Breeding:

  • Dr. Larson: “I want her to calve either before the calving season... or very early in the calving season... That sets her up for life.” (16:33, 22:54)

• On Economic Impacts:

  • Dr. Olds: “My heart breaks when it produces. Like, I lost 20 animals. I can’t lose two animals, let alone 20 animals.” (11:16)

Key Segment Timestamps

• [05:01] – Theileria’s Arrival, Persistence, and Stress-Linked Recurrence
• [06:45] – Regional Spread and Endemicity
• [07:47] – Immunity, Disease Expression under Stress
• [09:44] – Antibiotics, Supportive Therapy, No U.S.-approved Treatment
• [10:47] – International Treatment, Realities of Management
• [12:42] – Need for Vet-Producer Communication, Community Strategy
• [15:01] – Needle Changes, Herd Decisions
• [16:33] – Heifer Pre-Breeding Exam: Rationale and Steps
• [19:32] – Practical Timing, Group-Nutrition Adjustments
• [20:47] – Role and Limitations of Pelvic Measurements
• [22:54] – Holistic Assessment: Weight, Tract Scores, Pelvics

Tone and Takeaways

The conversation is pragmatic and supportive, balancing current scientific uncertainty with actionable advice. Speakers are candid (“this horse is bolted...”) and empathetic toward producer concerns. There’s a strong orientation toward teamwork—among veterinarians, researchers, and producers—to solve both disease and management issues.

Practical Takeaways

• Minimize animal stress and optimize nutrition—these are the core tools for managing both Theileria and heifer development issues right now.
• For Theileria, prevention is difficult; focus on herd awareness and best practices with veterinary guidance.
• Pre-breeding exams for heifers are vital: They help you maximize herd productivity and make hard culling decisions with confidence.

If you have additional questions or want to consult with Dr. Olds on Theileria or herd protocols, contact information will be included in the episode notes.