3 July 2019
This is part of a series of posts from our own Shane Hanlon’s disease ecology class that he’s currently teaching at the University of Pittsburgh Pymatuning Laboratory of Ecology. Students were asked to write popular science posts about (mostly) wildlife diseases. Check out all the posts here.
By Maggie Prokovich
As if climate change did not seem to be negatively impacting everything as we know it already, it also has recently been shown to trigger the spread of diseases throughout the United States. Diseases like Rocky Mountain spotted fever, Heartworm disease, and Lyme disease, which are all known to infect and kill dogs, are becoming even more threatening than they have been in in the past. Specifically, these diseases are being spread into new territories in which they have not been recognized previously, causing worry not only in pet owners, but in scientists and veterinary epidemiologists as well. This spread is thought to be mediated by drastic changes in the climate. Although these diseases can also strike humans, dogs are more of a concern at this point in time because of the significant amount of time that they spend outdoors, which is mostly in the warmer months.
Rocky Mountain Fever, a disease carried by ticks, affects both humans and dogs. The mechanism in which this bacteria acts is by transmission through a tick bite that leads to bacterial invasion of the blood stream. Eventually, the bacteria causes pooling of blood out of the blood vessels and into highly sensitive areas like the brain. A new tick strain has recently been discovered moving up through North America from South America. This tick species is unlike those commonly seen in the U.S because temperature actually impacts these ticks’ behavior. As temperature increases, this species of tick tends to become more active and bite more, therefore, spreading more disease. Most importantly, though, this tick species can carry Rocky Mountain Fever and contribute to its rising prevalence.
- Life stages of the blacklegged tick. Credit: CDC
Heartworm is also a growing concern for dog owners and scientists right now. Heartworms are parasites that are transmitted through mosquito bites. When this disease is transmitted, the heartworm is actually in its larval state, and it does not mature to adulthood until it is inside of its host. As the parasitic worm grows inside of its host, which in this case is a dog, it can invade the cardiovascular system and eventually lead to blood clots and death. Although, the heartworm larvae is only able to be transmitted from mosquito to dog when it is at a specific developmental stage. The higher the temperature in the environment, the faster the maturation of these heartworms, and the more likely they are to be in the specific developmental stage required for transmission. Because of this, the warming of the climate is causing this disease to be transmitted even more than it has been in the past. Preventative treatments can be administered to dogs, and it is highly recommended that these are utilized year-round now due to the warming of the climate.
Thirdly, Lyme disease is moving north to regions that have typically experienced cooler temperatures in the past. But, with rising temperatures, it seems that diseases thought to exist only in warm regions can infect just about anywhere. Lyme disease is carried by a tick, but contrarily to Rocky Mountain Fever, it is primarily carried by the blacklegged tick, seen in the photo attached. Although common in the U.S., these ticks are now moving north into upper regions of the U.S. and into Canada due to rising temperatures. Lyme disease causes symptoms in dogs such as fever, loss of appetite, joint swelling, reduced energy, and more. In research that tested dogs for Lyme Disease in certain counties in New York and Massachusetts, it was found that between 20% and 30% of dogs had the disease. Similar to global warming, these percentages are continuously on the rise.
At this point, there is no longer time to debate whether or not the climate is changing. In 2019, temperature in the U.S. has gone up 1.5 degrees in comparison to temperatures a century ago. Regardless of the reason for this temperature change, it is accelerating the spread and increasing the prevalence of diseases that can affect both humans and dogs. If there already weren’t enough reasons to care about climate change, our dogs’ health has now been threatened. If climate continues to change as drastically as predicted, these issues will only get worse.