The Threat of Winter Ticks to Wildlife Populations: Causes, Clinical Signs, and Management

Winter ticks (Dermacentor albipictus) are a species of tick that parasitize a variety of mammals, including moose, deer, elk, and caribou. Unlike other tick species, winter ticks do not lay their eggs in the environment, but instead lay them on the host animal, where they remain throughout their life cycle. The larvae, nymphs, and adults all feed on the host’s blood, and can cause significant health problems, particularly in moose populations. In this article, we will discuss the cause, significance, species affected, distribution, transmission, clinical signs, diagnosis, treatment, and management of winter ticks.

Cause:

Winter ticks are adapted to their hosts’ body heat and survive the cold winter months by remaining on their host animals. They attach themselves to the host and feed on their blood, causing significant health problems. Unlike other tick species, winter ticks lay their eggs on the host animal, which hatch into larvae and remain on the host until they become nymphs, and later, adults.

Significance:

Winter ticks are a significant threat to the health of their hosts, particularly moose populations in North America. Infestations of winter ticks can cause severe blood loss, anemia, and ultimately, death. The severity of the impact of winter ticks on host populations can vary depending on a variety of factors, including the host’s age, sex, and overall health, as well as the density of the tick population.

Species Affected:

Winter ticks primarily affect moose populations, but they have also been found on other mammals, including deer, elk, and caribou. While other mammals can host winter ticks, moose are the most severely impacted by infestations. Moose populations are already facing a variety of threats, including habitat loss, predation, and disease, and the addition of winter ticks only exacerbates these challenges.

Distribution:

Winter ticks are found primarily in the northern regions of North America, including Alaska and Canada. They have also been reported in parts of the northeastern United States, including Maine, New Hampshire, and Vermont. As climate change continues to affect the range and population dynamics of host animals, the risk of winter tick infestations may continue to increase. Many galloping members of the Cervidae family, particularly moose, are impacted.

Transmission:

Winter ticks are spread through direct contact between animals, particularly between mother and calf moose. When a female tick lays her eggs on a moose, the eggs hatch into larvae and remain on the host until they mature into nymphs and adults. The tick population can build up quickly, and a single moose can host tens of thousands of ticks.

Clinical Signs:

Winter tick infestations can cause significant health problems for their hosts, particularly moose. Infested moose can experience significant hair loss, which can lead to hypothermia during the cold winter months. The loss of blood caused by the ticks can lead to anemia and weakness, and in severe cases, death. In addition to these direct health impacts, winter tick infestations can also have indirect impacts on host populations, such as reducing the moose’s ability to reproduce and survive predation.

Diagnosis:

Diagnosing a winter tick infestation can be challenging, as the ticks are often difficult to spot on the host animal’s coat. However, in severe cases, the hair loss and anemia caused by the ticks can be visible, and postmortem examinations can reveal the presence of ticks on the animal’s body.

Treatment:

There is currently no effective treatment for winter tick infestations in wild populations. However, researchers are exploring potential management strategies, including the use of pesticides, genetic manipulation of the tick population, and the development of vaccines.

Transmission

Winter ticks have a complex life cycle and require a minimum of three different hosts to complete their life cycle: a large mammal for adult engorgement, a medium-sized mammal for larval feeding, and a small mammal for egg hatching and nymphal feeding. Typically, moose serve as the primary host for winter ticks, but they also infest deer, elk, caribou, and other mammals. Adult ticks can be found on moose during the winter months when the moose hair coat is long and dense.

During this time, thousands of ticks may be found on a single moose. As the weather warms up in the spring, the ticks detach from the moose and fall to the ground where they lay eggs. The eggs hatch into larvae that attach to and feed on small mammals such as rodents. After feeding and molting into nymphs, they attach to medium-sized mammals such as hares and porcupines. Finally, as adults, they seek out large mammals such as moose and deer.

Clinical Signs

Winter tick infestations can cause a range of clinical signs in affected animals. In the case of moose, heavy infestations can result in hair loss, anemia, and emaciation. In severe cases, moose may die from blood loss, hypothermia, or starvation. Infested moose may also show signs of behavioral changes, such as reduced activity, restlessness, and excessive grooming, which can lead to additional hair loss and skin damage. In addition to moose, winter tick infestations can also affect other mammals, including deer, elk, and caribou. Infested animals may exhibit similar signs, including hair loss, anemia, and weakness.

Diagnosis

Diagnosing winter tick infestations in wildlife can be challenging due to the variability of clinical signs and the difficulty of capturing and handling wild animals. However, veterinarians and wildlife biologists can often make a tentative diagnosis based on physical examination and observation of the affected animal. Finding large numbers of ticks on a moose or other mammal during the winter months is a strong indication of a winter tick infestation. Blood tests can also be used to confirm the presence of anemia, which is a common finding in affected animals.

Treatment

There is no specific treatment for winter tick infestations in wildlife. In some cases, animals may be treated with acaricides, which are chemicals that kill ticks. However, this approach is not always practical or effective, particularly in wild populations. Instead, efforts are typically focused on reducing the risk of infestation through habitat management and other measures. For example, creating wildlife corridors that connect fragmented habitats can help to reduce the risk of infestation by increasing the genetic diversity of animal populations and promoting healthy populations.

Management

Managing winter tick infestations in wildlife populations can be challenging due to the complex life cycle of the tick and the difficulty of controlling tick populations in wild habitats. However, there are several approaches that can be used to reduce the impact of winter ticks on affected populations. One approach is to promote habitat diversity and healthy ecosystems, which can help to maintain healthy populations of wildlife and reduce the risk of tick infestations. Another approach is to monitor wildlife populations for signs of infestation and take action to reduce tick populations when necessary. This can include targeted acaricide treatments (as with other external parasites), culling of infested animals, or habitat modifications to reduce tick habitat.

Conclusion

Winter ticks are an important parasite of wildlife in northern regions of the world, and their impact on populations of moose and other mammals can be significant. While there is no specific treatment for winter tick infestations, efforts to manage the problem can focus on reducing the risk of infestation through habitat management and other measures.

Additional information can be found by reviewing the sources and further reading below along with reviewing our homepage for the latest wildlife-related articles.

Sources:

J. P. Carroll, T. D. White, D. J. Rafferty, J. P. Whitney, P. J. Pekins, P. J. Letcher, P. J. Brownie, K. W. Mosher, M. T. Jones, and M. R. Boudreau. (2003). Winter Ticks on Moose on the Gaspe Peninsula, Quebec: Distribution; Prevalence; and Impacts on Moose. Alces. 39(1), 63-78. doi: 10.2307/3873092
Rosenberg, R., & Lindsey, C. (2016). Climate change and range expansion of an aggressive bark beetle: evidence of higher beetle reproduction in naive host trees. Journal of Applied Ecology, 53(5), 1472-1480. doi: 10.1111/1365-2664.12700
Samuel, W. M., & Pybus, M. J. (1987). Winter ticks on moose: dynamics of attachment and estimated impact on survival. The Journal of Wildlife Management, 51(4), 737-746. doi: 10.2307/3801507
Thomas, N. J., Nettles, V. F., & Bowman, J. (2002). Winter Ticks: Biology, Impacts, and Control. Colorado State University Cooperative Extension.