Publications
Effect of Reservoir Host and Climactic Conditions on Emerging Heartworm Disease
Emerging Heartworm Disease: Part 2
This publication will explain how the
effect of change in reservoir host, reservoir
movement, and climactic events
propagated the expansion of heartworm
disease into non-endemic areas. The
main premise is that changes in climactic
conditions may have created environments
in which the vector has increased
survivability. Climatic and host changes
have combined to expand the geographical
area of heartworm disease.
Reservoirs
Many people believe wildlife reservoirs
are responsible for the spread of heartworm
disease in the United States
(Bowman and Atkins 2009). Raccoons,
deer, bears, wolverines, and coyotes are
wildlife reservoirs affected by heartworm
disease.
In the Pacific west, the coyote has been used as a wildlife sentinel to monitor the spread of the disease. This is because coyotes do not have confounding factors (such as use of different preventives, veterinary criteria for testing, and travel) experienced by domestic dogs, yet they tend to parallel the pattern of prevalence of heartworm disease in domestic animals in an area (Sacks and Caswell-Chen 2003). A study in 2003 documented the spread of heartworm disease in coyotes from the Sierra Nevada foothills to central California (Sacks and Caswell-Chen 2003).
Domestic animals also can spread heartworms to new areas. After Hurricane Katrina, 1,958 dogs and 1,289 cats were relocated to different areas of the United States and Canada. Of the dogs relocated, 956 (48.8 percent) tested positive for heartworms. Seven of the 176 cats tested positive (Levy, et al. 2007). These 963 animals were relocated to other parts of North America. Many of the areas receiving these animals were considered non-endemic areas (Levy, et al. 2007).
Climactic Conditions
Climatic conditions must be favorable for heartworm
disease to spread into an area. Global warming and
municipal expansion are two events that could be
responsible for the spread of the disease.
As the effects of global warming create habitats conducive to the survival of mosquito populations, the geographic range of heartworms will continue to increase (Simon, et al. 2008). Climate modeling in Europe found a correlation between the increased incidence of heartworm cases and the changing of climate patterns (Genchi, et al. 2009). Weather patterns in the Gulf Coast region in 2001 and 2002 contributed to the change and increase of vectors of heartworm disease (Hampshire 2005).
Real estate development into less-populated and non-endemic areas moves families and their pets into new areas (Environmental Protection Agency 2009). Commercial and residential real estate development may create urban areas that are warmer than rural areas. According to the Environmental Protection Agency, this can increase nighttime temperatures in cities with populations of 1 million or more. Many mosquito vectors are nighttime feeders. This warming of nighttime temperatures allows them to stretch their geographical range to cooler climates for longer periods of time. (T. Nelson, Heartworm: An emerging disease climactic conditions, reservoir, competent vectors all contributing to disease spread 2010).
Conclusion
Canine heartworm disease continues to cause significant
morbidity and mortality to U.S. animals. Despite
excellent preventive products, sensitive diagnostic
testing, and effective adulticide therapies, the case
numbers continue to escalate. Documentation shows
heartworms are occurring more often and are spreading
to different areas.
Please talk to your veterinarian for heartworm information and recommendations for your particular situation.
The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.
Copyright 2011 by Mississippi State University. All rights reserved. This publication may be copied and distributed without alteration for nonprofit educational purposes provided that credit is given to the Mississippi State University Extension Service.
By Dr. Jody Ray, Assistant Chief of Community Veterinary Services, College of Veterinary Medicine Animal Health Center.
Discrimination based upon race, color, religion, sex, national origin, age, disability, or veteran’s status is a violation of federal and state law and MSU policy and will not be tolerated. Discrimination based upon sexual orientation or group affiliation is a violation of MSU policy and will not be tolerated.
Publication 2644
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture.
Published in furtherance of Acts of Congress, May 8 and June 30, 1914. GARY B. JACKSON, Director
(E-01-11)