Investigating veterinary management choices for canine heartworm disease (Dirofilaria immitis) in northern Mississippi

摘要

Canine heartworm disease affects nearly 45% of dogs in endemic regions of the United States (Atkins, 2005). There are concerns that the chronic use of macrocyclic lactone (ML) preventives to kill adult heartworms (“soft-” or “slow-kill”) may have contributed to the development of ML resistance. My study of this problem had three objectives: (a) to determine the frequency of “slow-kill” treatment in heartworm-positive patients and compare them to practitioner estimates; (b) to survey practitioner opinions on the factors influencing heartworm disease management; and (c) to analyze the heartworm prevention history of heartworm-positive patients in order to understand the causes of heartworm infection in this region. The study group consisted of dogs determined to be heartworm-positive when presented to a mixed-animal practice in northern Mississippi. Client records were scrutinized for heartworm preventive purchase history. Veterinarians in the four-doctor practice completed a questionnaire concerning their beliefs and practices in regard to heartworm treatment. 75% of heartworm-positive patients received “slow-kill” treatment, more than 20% greater than that estimated by the practitioners. 12.5% of patients received adulticidal treatment, equivalent to those that received no treatment. Injectable moxidectin was the most common ML preventive used in “slow-kill” treatment. Client financial concerns were cited as the primary reason for choosing “slow-kill” treatment. The results of this study show that practitioner estimates of “slow-kill” prevalence within their clinics may be suspect in their accuracy. Despite the recommendations of the American Heartworm Society, clients and veterinarians prefer the “slow-kill” method of heartworm treatment. However, trends in patient heartworm preventive history show that poor client compliance remains the predominant reason for heartworm infection. Thus, consistent use of existing, effective heartworm preventives should be the primary goal in reducing prevalence of heartworm infection, regardless of the recognized threat of resistance. Further study is needed on the risks and efficacy of “slow-kill” treatment and the effects of different ML preventives for the treatment of heartworm infection.