Deer host a variety of parasites, found both internally and externally. This is a common and natural occurrence in wildlife populations. Understanding these parasites is part of comprehending deer biology and overall ecosystem health.
Common Deer Parasites
Deer are susceptible to a wide range of parasites, broadly categorized into internal and external types. Internal parasites include various worms and protozoans, such as roundworms, tapeworms, flukes, and coccidia.
Gastrointestinal roundworms, such as the barberpole worm (Haemonchus contortus), are frequently encountered and can affect the digestive system. Liver flukes, like Fascioloides magna, are also found in deer and reside in the liver. Another notable internal parasite is the brainworm (Parelaphostrongylus tenuis), a type of roundworm that lives in the spaces surrounding the brain and spinal cord of white-tailed deer.
External parasites often attach to the deer’s skin and feed on their blood or tissues. Ticks are among the most recognized external parasites of deer, with black-legged ticks (Ixodes scapularis), commonly known as deer ticks, being prevalent in many regions. Deer keds (Lipoptena cervi), which are blood-feeding parasitic flies, also infest deer. Other external parasites include bot flies, which can lay larvae in the nasal passages, and mange mites, which cause skin irritation.
Impact on Deer Health
While deer can host numerous parasites, the impact on their health varies significantly depending on the parasite type, the intensity of the infestation, and the deer’s overall condition. Many parasite infections in deer are subclinical, meaning they cause no apparent symptoms. Heavy parasite loads can lead to various health issues, especially in young, old, or nutritionally stressed deer.
Internal parasites can directly affect a deer’s ability to absorb nutrients, leading to weight loss and a general decline in body condition. Large stomach worms can cause anemia and malnutrition. Lungworms can impair respiratory function, leading to coughing and reduced weight gain, and in severe cases, may result in death. White-tailed deer typically tolerate brainworm with few or no clinical signs. However, very high parasite loads can occasionally cause temporary lameness or other neurological issues, particularly in fawns.
External parasites can also compromise deer health. Heavy tick infestations can cause irritated skin, poor body condition, and even contribute to fawn mortality due to significant blood loss. Mange mites can lead to hair loss and skin thickening, and in severe cases, can be fatal to individual deer. The combined effect of multiple parasite types can further stress a deer’s immune system, increasing susceptibility to other diseases.
Potential for Transmission to Other Species
Many parasites carried by deer are species-specific and pose no threat to humans, pets, or livestock. However, some deer parasites can be transmitted to other species, including humans, through various routes.
The primary concern for human health involves vector-borne diseases transmitted by ticks found on deer. Black-legged ticks, or deer ticks, are well-known vectors for the bacteria that cause Lyme disease. While deer host these ticks, they do not carry the Lyme disease bacteria; humans contract Lyme disease from an infected tick bite, not directly from deer.
Another parasite with cross-species transmission potential is the brainworm. Although white-tailed deer tolerate this parasite well, it can cause severe neurological disease and often death in other cervids like moose, elk, and caribou, as well as in livestock such as llamas, alpacas, sheep, and goats.
Transmission occurs when these animals accidentally ingest snails or slugs that have consumed brainworm larvae from deer feces. Humans cannot be infected with brainworm.
Toxoplasmosis, a protozoan parasite, can also be present in deer meat. While often asymptomatic in deer, improper handling or undercooking of venison can lead to human infection.
To minimize risk, avoid handling fresh carcasses with open wounds, freeze meat before cooking, and cook venison thoroughly to at least 160°F (71°C). General hygiene practices, such as washing hands after handling deer or being in deer habitats, and checking for and promptly removing ticks, are effective preventive measures against parasite transmission.