Letters: Follow-up questions to IMHA article
I enjoyed reading "IMHA: Diagnosing and treating a complex disease" in the December 2008 issue of Veterinary Medicine. However, I did have some questions: What role do vaccinations play in the disease process, and should I discontinue vaccinating a patient after IMHA has been diagnosed?
Also, is there any benefit to continuing a low dose of prednisone in a patient after it has recovered? I had a patient transferred to me recently that has been receiving prednisone for about five years. It recovered nicely at that time but was still receiving a low dose to try to prevent IMHA from recurring. I hadn't heard of this being done before this case.
Once again, I really enjoyed this well-written article.John Boley, DVM
Animal Hospital of Colorado Springs
Colorado Springs, Colo.
Dr. Shaw responds: Thank you for your thoughtful comments, Dr. Boley. One study in dogs with IMHA found that one-fourth had been vaccinated with a polyvalent vaccine within one month of onset of the disease.1,2 But a large retrospective study of medical records in Europe uncovered no relationship between vaccination and IMHA.3 These inconsistent findings suggest that while vaccination cannot be directly linked to IMHA, it may—along with certain drugs, infections, and other factors—set off or enhance an already activated immune system in a predisposed patient.
In cases in which I suspect IMHA may have been triggered by a vaccination, I discourage revaccination and recommend measuring antibody titers yearly instead. Distemper, parvovirus, and rabies antibody titers are simple to run and are performed at many commercial laboratories. Laboratories state that titers do not ensure protection against infection, and it is certainly true that adequate serum antibody titers do not represent total protection in all types of infectious diseases. The value of titers depends on the type of laboratory method used, the type of infection, and, most important, the results of experimental challenge studies.2 Over the past six years, I have used this method and have obtained adequate antibody titers in about a half dozen dogs with previously diagnosed IMHA. To my knowledge, none of these patients ever experienced clinical signs of the diseases for which they had adequate titers.
The goal of treating a first-time IMHA patient is generally to taper drugs slowly and eventually to stop medications altogether since the side effects of medications can be severe, and chronic immunosuppression can predispose a patient to long-term problems. However, in some cases, this appears difficult. In patients whose packed cell volume declines in the face of a slow drug taper, in patients who have a recurrence of autoagglutination, or in patients whose IMHA recurs quickly after all medications are discontinued, the clinician should consider lifelong, low-dose corticosteroids. Some dogs can be maintained on anti-inflammatory drugs with every-other-day dosing.4 Usually, I do not use lifelong corticosteroids to try to prevent recurrence in first-time patients. Still, in your case, I would not change a protocol that has proven to be successful in that patient.
Nicole Shaw, DVM, DACVIM
1. Duval D, Giger U. Vaccine-associated immune-mediated hemolytic anemia in the dog. J Vet Intern Med 1996;10:290.
2. Greene CE, Schultz R. Immunoprophylaxis. In: Greene CE, ed. Infectious diseases of the dog and cat. 3rd ed. St. Louis, Mo: Saunders Elsevier, 2006;1069-1119.
3. Giger U. Regenerative anemias caused by blood loss or hemolysis. In: Ettinger SJ, Feldman EC, eds. Textbook of veterinary internal medicine. 6th ed. St. Louis, Mo:Elsevier Co, 2005;1886-1907.
4. Miller E. Immune-mediated hemolytic anemia. In: Bonagura JD, Twedt DC, eds. Kirk's current veterinary therapy XIV. St. Louis, Mo:Saunders Elsevier, 2009;266-276.