Over the past several years, the earth has experienced extreme weather patterns from heat to cold, hurricanes to flooding, and tsunamis to snowfalls. While many of us are learning to adapt to the immediate emergencies, such as rescuing people and companion pets from flooded houses, we need to consider the health effects caused by these climate changes. So, how is the health of our companion pets affected by climate change?
During the summer of 2016, a boy and more than 2,300 reindeer passed away from anthrax infection in a remote area of Siberia. This was the first occurrence of anthrax in the region in over 75 years.
Now, anthrax is naturally occurring in any type of soil and can be fatal to all warm-blooded animals – including our companion pets.
Scientists believe that the Siberian incident was due to thawing permafrost, which then released this ‘bioweapon’ into the soil and water.
Many researchers wondered, “What other infectious diseases could be released into the atmosphere that humans and animals lack immunity to?” They dubbed these as ‘zombie diseases’.
We have all witnessed disturbing images of starving polar bears that have to swim further between ice sheets to find food. However, emaciation due to climate change is not the only problem polar bears or the other Arctic populations are suffering.
Many studies have indicated disruption of normal immune function with subsequent deleterious changes in polar bears, ringed seals, sled dogs and foxes due to the presence of environmental contaminants (persistent organic pollutants). Additionally, these pollutants have broader damaging effects on the body, which are implicated in disrupting endocrine systems, decreasing bone density, and affecting the reproductive systems.
Scientists suspect that warming trends are causing the long-range transport of chemicals and other non-native species to the once considered isolated Arctic, thus increasing the amount of contaminant exposure.
Greenland Sled Dogs
Researchers are warning that the Greenland Sled Dog is at risk of extinction for numerous reasons, but primarily from climate change. Since the sea ice is melting, hunters and fishers are hindered from obtaining food from traditional sources.
Other reasons include outbreaks of canine distemper and parvovirus, along with the introduction of snowmobiles that have replaced sled dogs.
You might think these changes are meant to be, but researchers argue that the Greenland sled dogs are an ecologically important species.
Heartworm (Dirofilarial immitis infection) is a parasite that lives in the heart and is spread by its filarial-infected mosquitoes. Mosquitoes were once fairly limited to the Southeastern part of the United States. Now, heartworm is found in all fifty states – including Hawaii and Alaska. Plus, the risk of heartworm in companion pets is steadily increasing.
The Companion Animal Parasite Council (CAPC) does not explicitly say that the culprit is climate change. However, if you read in between the lines of the 2018 forecast, it is inherently obvious:
“For the fourth year in a row, CAPC forecasts heartworm infection prevalence to be above normal across virtually the entire United States. Unfortunately, 2017’s above normal forecast panned out. This increase was partially attributed to the hot and wet weather that occurred in 2016, (mosquitoes like these conditions), and in 2017 weather was again hot and wet. Moreover, infected dogs act as “reservoirs of infection”, increasing the number of infected mosquitoes and ultimately spreading the parasite to other dogs. CAPC is concerned with this annual increase in numbers of cases. Nationally, prevalence rates have risen each of the last five years and are now up 20% from 2013 levels.”
In the United Kingdom, scientists are saying that more cases of heartworm are being diagnosed further north in England and Scotland because of wetter and warmer summers.
On the European Continent, heartworm is spreading as well. However, they are also experiencing the spread of another related parasitic worm by mosquitoes, Dirofilaria repens. This worm is not as harmful to dogs and cats as the related species causing heartworm disease, because it usually causes a non-pathogenic subcutaneous infection in dogs. However, D. repens has spread from Southern Europe to Northern Europe. The authors of “Recent advances on Dirofilaria repens in dogs and humans in Europe” believe climate change contributed to the expansion of mosquito vectors, but the primary reason for concern is the rate of undiagnosed infected dogs.
Lyme Disease (caused by Borrelia burgdorferi infection) is possibly the most famous of all tick-borne diseases. Lyme Disease is named after the town of Lyme, Connecticut, where it was first discovered.
Since then, we have witnessed Lyme Disease spread westward across the United States and into Canada. In 2018, 14.92% of dogs tested positive for the disease in Connecticut, 7.53% of dogs tested positive in Minnesota, and 1.32% in Washington state.
Lyme Disease is not the only tick-borne disease of concern, however, as anaplasmosis (Anaplasma phagocytophila, A. platys) and ehrlichiosis (Ehrlichia canis, E. ewingii) are also spreading across the country.
Scientists again say that climate change is the primary cause. Based on numerous investigations, ticks are expanding their geographic ranges because of rapidly increasing global temperatures.
However, scientists also identify other variables – such as host availability, habitat suitability, relative humidity tolerance, the extent and duration of freezing temperatures, and human impact – all of which may limit the likely rate and extent of range expansion for different tick vector species. These factors deserve as much attention in understanding what influences tick range expansion as climate change.
In Minnesota, however, there has been a slight dip in reported cases of Lyme disease (from a high of 8.63% in 2016 to 7.53% in 2018). Why did this decrease of Lyme Disease occur? Factoring in that the number of dogs tested per year varies, the contributing factors could include:
- An increased percentage of dogs being vaccinated against Lyme Disease, even though the vaccine is not considered to be very effective, and can cause adverse effects. (Note: W. Jean Dodds and Hemopet do not recommend this vaccine.)
- White-tailed deer are dying from chronic wasting disease and not spreading the ticks as far and wide.
- People are walking their dogs in areas without a high abundances of ticks.
- The weather was different in 2018 compared to the previous years.
- Cases may be under-reported.
On a brighter note, any reduction in prevalence of these diseases might be due to the fact that some of them – like Powassan virus and anaplasmosis – potentially may not fair well in weather that is too warm. As always, such benefits also have the trade-offs of climate change!
Fleas are not as affected by climate change as are ticks. However, their season is extending due to the warmer temperatures. In some areas of the country, fleas are living year-round. Indeed, they are becoming smaller, more aggressive and increasing in numbers. Flea control using generally safe products and other measures including environmental cleanliness is important.
“As Earth Warms, the Diseases That May Lie within Permafrost Become a Bigger Worry.” Scientific American, vol. 315, no. 5, Nov. 2016, pp. 11–12., doi:10.1038/scientificamerican1116-11, https://www.scientificamerican.com/article/as-earth-warms-the-diseases-that-may-lie-within-permafrost-become-a-bigger-worry/.
Capelli, Gioia et al. “Recent advances on Dirofilaria repens in dogs and humans in Europe.” Parasites & vectors vol. 11,1 663. 19 Dec. 2018, doi:10.1186/s13071-018-3205-x, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6299983/.
Companion Animal Parasite Council, 2019, http://www.capcvet.org/.
Sonenshine, Daniel E. “Range Expansion of Tick Disease Vectors in North America: Implications for Spread of Tick-Borne Disease.” International journal of environmental research and public health vol. 15,3 478. 9 Mar. 2018, doi:10.3390/ijerph15030478, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5877023/.
Sonne, Christian et al. “A veterinary perspective on One Health in the Arctic.” Acta veterinaria Scandinavica vol. 59,1 84. 16 Dec. 2017, doi:10.1186/s13028-017-0353-5, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5732494/.
Sonne, Christian et al. “Greenland Sled Dogs at Risk of Extinction.” Science, vol. 360, no. 6393, 8 June 2018, p. 1080., doi:10.1126/science.aat9578, http://science.sciencemag.org/content/360/6393/1080.1.
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