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Animal Diseases

Animal Diseases and Climate Change


Climate change causes many alterations to the environment that can have far-ranging effects. The warming climate, more frequent flooding, increased rainfall in some areas, drought in others, and shifting seasonal events, such as later first snowfall, can all affect diseases in animals. The greatest reason is that the changing climate allows disease carriers or vectors, such as ticks, fleas, and mosquitoes, to have increased periods of activity thus longer transmission seasons due to warmer temperatures. These insect vectors may even establish in areas they have not before, affecting animals they may not have previously.



These insects are very sensitive to temperature and thus move with the shifting heat patterns. They also need water, so increased flooding due to more intense storms, longer summers, and mild winters can provide favorable breeding conditions for insects and lead to greater numbers of ticks and mosquitoes. Increased rainfall also leads to increased vegetation, which includes food sources. Rodent populations increase with greater food sources and are hosts to some of these vectors. Soil moisture, temperature, and drought also affect tick populations. Climate change effects are not always negative for all species, however. For example, opossums didn’t used to live in New Hampshire but have moved northward with the warming temperatures.


How Animal Diseases Affect Wildlife


White Nose Syndrome (WNS) is a fungus that affects bats and first appeared in New York State in 2006. Bats are more susceptible to the disease if their health is weakened. If conditions are too dry, less water is available for them, or if conditions are too hot, bats are very susceptible to heat and may be more vulnerable to disease.


Climate change may influence the incidence of rabies too, such as in raccoons and coyotes. Drought, for example, will drive animals to areas where there is water, often closer to people, as will a lack of food.


West Nile virus and Eastern Equine Encephalitis are diseases carried by mosquitoes that affect many species of birds, such as crows, hawks, grouse, and owls.


What NH Fish and Game Is Doing in Response to Animal Diseases


The Wildlife Division is working with the NH Department of Agriculture, the Northeast Deer Technical Committee, and federal agencies to prevent CWD from entering New Hampshire through a CWD-infected animal, living or dead. Fish and Game samples more than 400 hunter-harvested deer annually as well as in a testing program the NH Department of Agriculture has for captive deer and elk as an early warning program for CWD detection.


The Nongame Program has been working to protect bat populations, such as installing protective gates on hibernacula (bat caves), and conducting surveys of bat numbers in the state.


Fish and Game biologists collaborated with the University of New Hampshire on a long-term moose study (2000-2005 and 2014-2018) to determine overall moose her health, productivity, and impacts of winter ticks on survival. The moose population began to decline in the 1990s and the increase in the winter tick numbers was determined to be the main cause.


Animal Diseases and People


The increased risk of disease in animals has several important implications for residents and visitors to New Hampshire. Hunting and fishing could be further affected, such as moose permits, if climate change worsens. Biological diversity is important for human health, for many reasons, including that wild animals help keep ecosystems healthy, such as freshwater mussels that filter water. Biodiversity can also help reverse climate change, like plants that take in carbon dioxide, and our food supply depends on a degree of biodiversity, such as needing pollinators to fertilize our crops. There is also the possibility that increased disease in wildlife can lead to increased disease in humans, such as cases of rabies and West Nile virus.


Taking Action  

  • Follow the Fish and Game guidelines on preventing CWD
  • Remove standing water from your yard to prevent mosquito breeding.
  • Change water in birdbaths every day or two to help birds and prevent mosquito breeding.
  • Educate yourself and share your understanding with friends and family about how climate change affects wildlife and habitats. 
  • Start planning now for good ecological health and get involved in your local community by addressing potential climate change issues in your town or region. 
  • Support and volunteer for environmental and conservation organizations that address climate change impacts to wildlife and habitats.
  • Become a citizen scientist and help collect data on plants, wildlife, water, and weather.