A recent study has shown a high relapse rate: 12 of 27 dogs treated long-term, with eight of the 27 relapsing more than once.1 Four of the 27 dogs relapsed within one or two weeks of missing doses of decoquinate. None of the dogs that were treated
long-term in this study developed proteinuria, muscle wasting, severe cachexia, or evidence of renal disease.1 Decoquinate inhibits the organism's asexual reproduction cycles and subsequent release of zoites, which stops the pyogranulomatous
inflammation and sequelae. Mean survival times that were previously estimated at 10 to 12 months2,3 were greater than 39 months for 22 of the 27 dogs; in 11 of these 22 dogs, the decoquinate was discontinued after a mean
treatment time of 13.7 ± 6 months. The remaining 11 continued to receive decoquinate with a mean treatment time of 20 ± 8
In that study, 84% of dogs treated with trimethoprim-sulfadiazine, pyrimethamine, and clindamycin followed by decoquinate
had a mean survival time of greater than two years. Further long-term studies are needed to determine mean survival times,
as 22 of 27 dogs were still alive when the study was published.1
Michael G. Strain, DVM
Tommi A. Pugh, DVM
Claiborne Hill Veterinary Hospital
19607 Highway 36
Covington, LA 70433
1. Macintire DK, Vincent-Johnson NA, Kane CW, et al. Treatment of dogs infected with Hepatozoon americanum: 53 cases (1989-1998). J Am Vet Med Assoc 2001;218:77-82.
2. Keller RL, Lurye J. What is your diagnosis? J Am Vet Med Assoc 2004;225:1531-1532.
3. Macintire DK, Vincent-Johnson N. Canine hepatozoonosis. In: Bonagura JD, ed. Kirk's current veterinary therapy XIII small animal practice. Philadelphia, Pa: WB Saunders Co, 2000;310-313.
4. Cummings CA, Panciera RJ, Kocan KM, et al. Characterization of stages of Hepatozoon americanum and of parasitized canine host cells. Vet Pathol 2005;42:788-796.
5. Panciera RJ, Mathew JS, Ewing SA, et al. Skeletal lesions of canine hepatozoonosis caused by Hepatozoon americanum. Vet Pathol 2000;37:225-230.