How can veterinarians best convey the benefits of metaphylaxis to their stocker clients?

Bovine Respiratory Disease (BRD) is an all-too familiar challenge to stocker operators, despite numerous advances in animal health over the past 40 years, says Dr. Ken Blue, DVM, and Elanco Animal Health technical consultant. “As veterinarians, we know that because a higher percentage of stocker cattle come from multiple sources, these cattle run a greater risk of developing BRD.”

Q: When are cattle most susceptible to respiratory disease?

A: For cattle, periods of stress are when their physiological state changes, such as weaning or severe changes in weather. Generally, the greatest stress to a beef animal is at the time of movement from farm of origin to some type of feeding facility, such as a stocker operation, backgrounding facility or a feedlot. For dairy calves, in most cases, the time of greatest stress is as we transition them from individual housing to group housing. A stressed animal releases a number of agents, particularly corticosteroids, that reduce the ability of the immune system to fight infection.

Q: How does an animal naturally react to fight infection?

A: When a bacterial infection occurs in the lungs, alveolar macrophages are some of the first responders. They eliminate bacteria by a process called phagocytosis. Another primary defense cell that responds to infection is the neutrophil. Neutrophils are like the cavalry in that once they recognize the presence of infection, they migrate in large numbers to the site of infection, in this case the lungs. Like macrophages, neutrophils also kill bacteria by engulfing and digesting them.

Q: How does Micotil^® (tilmicosin injection) work with the immune system?

Micotil is a macrolide antibiotic approved for the treatment and control of BRD which has characteristics that allow it to concentrate in the immune cells, specifically alveolar macrophages and neutrophils. We know these cells are migrating to fight infection in the lungs. As they are delivered to the site of infection, they bring high concentrations of tilmicosin (Micotil) directly to that site as well.*

Q: How quickly does Micotil respond and what is its duration when treating respiratory disease?

A: Micotil is fast-acting*¹ and long-lasting.*^2,3,4 Data shows that Micotil concentrates in diseased  lungs within one hour¹ following a subcutaneous injection of 1.5 mL/100 pounds body weight. Even in consolidated or severely diseased lungs, Micotil concentrates within two hours.*¹ Micotil does not depend on circulation for delivery to the lungs; it concentrates in the first cells that migrate to the infection site, enabling its fast-acting response. 

Also, in our original research we found that Micotil persists in the lungs in significant concentrations for at least three to four days² following a subcutaneous injection. As we conducted additional research, we found that Micotil persisted in high levels in key defense cells through 10 days*^3,4 post-injection, confirming its long-lasting* characteristic.

Q: How does Micotil’s long-lasting* characteristic impact re-treat practices?

A: Years ago, if we were not seeing what we felt was an adequate response in two to three days, we would typically re-treat. Today, we know more about the long duration effect of Micotil and the response time of the animal. If the calf doesn’t look totally well in two to three days, it may still be convalescing and on its way to recovery. In trials, we have seen additional recoveries by extending the post-treatment evaluation,⁵ or post-metaphylaxis evaluation periods,⁶ to five or even seven days.

*The clinical significance of this data has not been demonstrated.

Q: What are a few of the factors that affect respiratory health specifically for dairy calves?

A: With dairy calves, in most cases, the primary stress period for respiratory disease is during transition or at the time of movement from individual housing to group housing. This typically occurs between seven and eight weeks of age and usually follows weaning. When calves are initially placed in a group environment, locating feed and water can be an issue. Another stress is commingling. Bringing beef or dairy animals from an environment with relatively few animals to a larger group of new pen mates can in itself be stressful.

We often overstock dairy calves at time of first grouping. Initial groupings should have no more than 12 calves. Larger groups increase calf interaction and make it more difficult to locate feed and water. Small groups tend to not be as heavily stressed and are less challenged by disease.

Important Safety Information

See label for complete use information, including boxed human warnings and non-target species safety information. Micotil is to be used by, or on the order of, a licensed veterinarian. For cattle or sheep, inject subcutaneously. Intravenous use in cattle or sheep will be fatal. Do not use in female dairy cattle 20 months of age or older. Use in lactating dairy cattle or sheep may cause milk residues. The following adverse reactions have been reported: in cattle: injection site swelling and inflammation, lameness, collapse, anaphylaxis/anaphylactoid reactions, decreased food and water consumption, and death; in sheep: dyspnea and death. Always use proper drug handling procedures to avoid accidental self-injection. Do not use in automatically powered syringes. Consult your veterinarian on the safe handling and use of all injectable products prior to administration. Micotil has a pre-slaughter withdrawal time of 42 days.

¹Thompson, TD, SB Laudert, S Chamberland & K Lawrence. 1994. Micotil: pharmacokinetics of tilmicosin, a semi-synthetic macrolide antibiotic, in acutely pneumonic cattle and primary bovine alveolar macrophages. 6th European Assoc Vet Pharmacology and Therapeutics Congress, Aug., pp 31-32. 

²Thompson, TD & K Lawrence. 1994. Micotil: pharmacokinetics of tilmicosin, a semi-synthetic macrolide antibiotic, in cattle. 6^th European Assoc Vet Pharmacology and Therapeutics Congress, Aug., pp 55-56.

³Fossler, SC, JW Moran & TD Thomson. 1998. Pharmacologic mechanism for tilmicosin in the control of cattle pneumonia. Proceedings of the 79th Annual Meeting of Conf of Research Workers in Animal Diseases, p 82.

⁴Fossler, SC, JW Moran, MA Martinez & TD Thomson. 2000. Distribution of Tilmicosin into Bovine Peripheral Neutrophils Following Micotil Treatment. Proceedings of the 81^st Annual Meeting of the Conference of Research Workers in Animal Diseases. p 101.

⁵Carter, BL, DG McClary, GD Mechor, RA Christmas, MJ Corbin & CA Guthrie. 2006. Comparison of 3-, 5- and 7-day post-treatment evaluation periods for measuring therapeutic response to tilmicosin treatment of bovine respiratory disease. Bov Pract 40:97-101.

 ⁶ McClary DG, MJ Corbin, BL Carter, J Homm, G Vogel, W Platter & CA Guthrie. 2008. A Comparison of 3-, 5-, 7- and 10-day Post-metaphylaxis Evaluation Periods on Health and Performance Following On-arrival Treatment with Tilmicosin in Feeder Cattle – A Summary of Two Studies. Bov Pract 42:117-127.

Micotil^® is a trademark for Elanco’s brand of tilmicosin injection.
© 2011 Elanco Animal Health.
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