Animal Science and Technology


Jones, Darlene, E

Advisor Department

Animal and Veterinary Science




heartworm; shelter; dirofilaria; parasite


Heartworm in Canines

Kelsey McKenna

Faculty Sponsor: Darlene Jones, DVM, Animal Science

Each year thousands of dogs in the United States become infected with heartworm, which is caused by Dirofilaria immitis. D. immitis is a parasite that is transmitted to dogs via a bite by an infected mosquito. Nine of the seventy competent mosquito species reside in Rhode Island. The true incidence of D. immitis is unknown. Current incidence maps are derived from data generated at veterinary clinics and do not include shelter dogs. The objective of this study is twofold: to determine the prevalence of D. immitis in shelter populations across the state of Rhode Island and to compare the frequency of heartworm infection in shelter dogs to privately owned dogs.

Records were reviewed from three different shelters for the years 2006 through 2010. At each shelter the primary way of testing for heartworm disease was by a 4Dx SNAP test. Only one of the three shelters tested all dogs, and two of the three shelters tested some of the dogs. If a dog was tested more than once only the initial test was included in the analysis. For the years 2006 through 2010 the heartworm prevalence rate was 2.06%, 1.05%, 0.04%, 1.0% and 2.05% respectively. When compared to the prevalence of D. immitis in veterinary populations using Pearson’s Chi-Square test (df=1), there was no statistical significance between the prevalence of heartworm disease in shelter populations and dogs under the care of a veterinarian. It is important to note however, that not all dogs were tested for heartworm disease in all of the Rhode Island shelters.

There is a dichotomy between the testing and treatment of owned dogs and shelter populations. The most commonly cited reason for not testing shelter dogs for heartworm disease is lack of funding. Dogs under the care of a veterinarian are usually tested annually for heartworm infection. In open admission shelters, the most common course of action for a heartworm positive dog is to adopt out the dog with the disease or euthanize the dog. If the dog is treated, the protocol closely resembles that of veterinary patients with a few modifications due to lack of funding: melarsomine split-dosing three-dose protocol in addition to an ivermectin treatment. Most veterinary patients also receive doxycycline, a nonsteroidal anti-inflammatory drug, and an opiate analgesic in addition to this treatment. In Rhode Island, the prevalence of heartworm disease in shelter populations follows the trends found in privately owned dogs in veterinary clinics. The data shows that the shelter population may be a sentinel population for Rhode Island dogs. If there is an increase in heartworm in shelter dogs, there may be more potential danger for household pets and proper precautions should be taken.