47, 000 Ticks on a Moose, and That’s Just Average

47,000 Ticks on a Moose, and That’s Just Average. Blame Climate Change.

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The biggest number of winter ticks that Peter J. Pekins ever found on a moose was about 100,000. But that moose calf was already dead, most likely the victim of anemia, which develops when that many ticks drain a moose’s blood. So it was probably a lowball estimate, because some of the ticks had already detached.

“It’s about as grody a picture as you can imagine on a dead animal,” said Dr. Pekins, a professor of natural resources and the environment at the University of New Hampshire. (A warning: The pictures below are, indeed, grody.)

Between 2014 and 2016, Dr. Pekins counted ticks on moose calves at two locations in New Hampshire and Maine. He wanted to see how the moose were faring, given that climate change has been delaying snow’s arrival in New England’s winters.

The longer-lasting warmth gives the ticks a leg up as they glom onto the moose, their preferred hosts, in the fall. They then feed through winter and hop off in the spring to lay eggs.

The moose-tracking exploits of Dr. Pekins and his colleagues were published last month in the Canadian Journal of Zoology. They argued that three consecutive years of tick outbreaks “arguably reflects a host-parasite relationship strongly influenced by climate change at the southern fringe of moose habitat.”

While large numbers of ticks, literal bloodsucking parasites, aren’t great for adult moose, they’re especially bad for moose calves, which can die from the onslaught.

With the help of a team that shoots nets from helicopters to catch and tag the calves with radio collars (a process that takes about 15 minutes for the moose and eschews the use of drugs), Dr. Pekins was able to track 179 moose calves. The average number of ticks he found on them was 47,371.

“Anything over 35,000 is trouble for a calf moose,” he said. Over the study period, 125 calves died, 70 percent of those being tracked.

In some ways, the moose are a victim of their own success.

“Maine and New Hampshire had less than 50 moose in the 1970s,” Dr. Pekins said. But their numbers have multiplied many times over since then, thanks to improvements in the available habitat and a lack of predators like wolves.

As a result, Maine now has anywhere from 60,000 to 70,000 moose; New Hampshire had as many as 8,000 or 9,000 in the early 2000s, though the numbers now hover around 5,000. And it’s the abundance of moose that enables the ticks to survive.

“You need a lot of moose on the landscape to have a lot of parasites,” Dr. Pekins said. “That’s the host-parasite relationship.”

That relationship was more or less in balance until the changing climate tilted the scales in the ticks’ favor. Over the long term, Dr. Pekins doesn’t expect the moose to die off completely, but there will be fewer of them.

The ticks don’t want the moose to die off completely, either. “The parasite doesn’t want to kill off its host — that’s bad evolution,” Dr. Pekins said. “Because the parasite loses the game.”

For more news on climate and the environment, follow @NYTClimate on Twitter.


Difference Between Deer Ticks and Wood Ticks

Deer ticks and wood ticks are broadly descriptive common names that are often used to refer to four species of ticks. Deer ticks usually refer to the blacklegged tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus), while wood tick refers to the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni). The common name deer tick is somewhat antiquated, but is still a frequently used name that is now correctly referred to as blacklegged tick.


Both species of wood ticks are members of the family Ixodidae, the hard ticks. They are dark brown in color with silver-gray or whitish coloring on their back. Both have a dorsal plate on their back called the scutum, and their mouthparts are visible when viewed from above the tick. The males are slightly smaller than the females in the adult stage. Both species have six legs in the larval stage; eight legs in the nymphal and adult stages; and undergo a life cycle that consists of four stages: eggs, larvae, nymphs and adults.

Neither of these ticks is considered a vector of Lyme disease, but they do transmit other diseases and both species are known to cause tick paralysis, a condition triggered by a toxin that is released from the tick’s salivary glands when taking a blood meal.

The American dog tick is the primary tick vector of Rocky Mountain spotted fever in the eastern United States and can also transmit tularemia. Overwintering American dog tick larvae are of special interest because they can acquire the disease organism that causes Rocky Mountain spotted fever by hatching from an infected egg and are infected with the disease without feeding on an infected host. This phenomenon is known as transovarial transmission. The Rocky Mountain wood tick can transmit Colorado tick fever, tularemia and Rocky Mountain spotted fever to humans.

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Deer ticks are also in the family Ixodidae. Blacklegged ticks (Ixodes scapularis) and the Western blacklegged ticks (Ixodes pacificus) are also known as deer ticks and are often mistaken for brown dog ticks. Named for their propensity to feed on white-tailed deer and other Western deer species, these ticks may also feed on other small and large mammals as hosts, including humans. Livestock and domestic animals can also be hosts. Ixodes scapularis is primarily found in the eastern half of the United States and Ixodes pacificus is primarily found in the western states of California, Oregon, Washington and eastward into Nevada, Utah and Idaho.

Deer ticks can sometimes be confused with other tick species, but generally are smaller than most ticks. Unfed adult female blacklegged ticks are approximately 3 — 5 millimeters (mm) long, are colored red and brown with a darker scutum shield on their back. Female ticks that are engorged with a blood meal appear darker and are about 10 mm long. The uniformly brown adult male tick is smaller than its female counterpart. Nymphs are between 1-2 mm long (about pin-head sized) with eight legs and larvae are less than 1 mm long (about poppy seed sized) and have only six legs. Deer tick adults are about half as large as the wood ticks.

Deer ticks are the most common vectors of Lyme disease. Their preferred habitat is shaded grassy and brushy areas frequented by both small and large mammals, dogs, cats and other warm-blooded hosts. As these hosts brush against the grass, deer ticks cling to the coat of the animal and begin to feed. Because the ticks usually bite a different host for their subsequent blood meals, infected ticks are capable of spreading Lyme disease quickly throughout a population. The small size of the deer tick is also a factor in the prevalence of Lyme disease. Their bites are not painful, and most victims do not notice them until they have become engorged from prolonged feeding and may have transmitted the Lyme disease organism.

Unlike Ixodes scapularis, Ixodes pacificus nymphs do not climb onto low vegetation and wait for a passing host. Instead, they live within litter on the forest floor, climb onto logs and the lower portions of tree trunks up to a height of about 3 — 4 feet to await a passing host.


These 10 Diseases are Plaguing Whitetail Herds Nationwide

November 5, 2019

Have you shot a whitetail only to find it had one of these common diseases or parasites?

Across the country from Wisconsin to Wyoming, whitetail herds face a number of natural diseases that impact their populations. The population itself, if unmanaged, can allow certain parasites, injuries, and viruses to run rampant with devastating effects.

Know which ones can render your harvested whitetail inedible and which are safe to eat.

Here are the top ten deer disease threats, in no particular order, that plague whitetail deer nationwide.

Hemorrhagic Disease (HD)

Hemorrhagic disease (HD): There are two types of HD viruses that impact whitetail deer. Also sometimes known as epizootic hemorrhagic disease. Until Chronic Wasting Disease was discovered, HD was the most well known virus infecting deer herds nationwide. Early stages of HD result in fever which drive deer to water to cool their bodies and where they are often found dead. Other symptoms include swelling around the head, tongue and respiratory distress. Infected deer are affected differently and some may not display symptoms for months to years after contracting the virus while others die shortly after exposure. As the virus is not one that can be transmitted to humans, the meat from a harvested deer with HD is still edible.

Blue Tongue (BTV)

Blue Tongue (BTV): This virus is contracted by biting midges (Culicoides) when they are at their peak season between August and October. Symptoms include fever; swollen neck, tongue or eyelids; excessive salivation; sloughed or deformed hooves; reduced activity; and significant weight loss. The swelling causes the deer’s tongue to take on a blue color, thus the name. A clear indicator that a deer has had either HD or BVT and lived to graze another day is by the sloughed re-growth of their hooves. This virus cannot be transmitted to humans through consumption of the meat. However, many deer that have HD or BVT also have secondary infections resulting from injuries or swelling. If you shoot a deer infected with BTV during hunting season, any infected meat should not be consumed.

Deer Warts

Deer Warts: Cutaneous fibromas are wart-like growths are viral based and contracted through an open wound or insect bite. The deer’s immune system reacts in what can sometimes result in large, grotesque growths that apparently have no adverse impact on the deer. Bucks are often the most likely to develop the growths from battle wounds. Should the warts grow around the deer’s eyes, mouth or nose, they may begin to interfere with the animal’s ability to see and feed. Large tumors often have bacterial infections and any infected area is unfit for human consumption. But as the growths are localized to the skin and do not penetrate into the muscle, the deer meat is still likely fine for human consumption.

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Parasitic Worms

Parasitic Worms: Lung worm is passed from deer to deer via their feces and being infested by young deer feeding on low vegetation this parasite is common amongst whitetail. As with most parasites, in low volumes they do not impact the animal’s health. However, in large volumes the Large Lung Worm will cause severe respiratory distress and lead to pneumonia and other infections by clogging airways. Large Stomach Worms, once inside the infected animal’s system, take up residence in the stomach and cause can cause emaciation. Though a common parasite to deer, these worms can go undetected in a healthy animal in low numbers. However, should the animal’s immune system already be compromised due to other parasites or viruses the volume of worms can sky rocket and lead to death.

Brain Abscesses

Brain abscesses: Bucks are 90% more likely to develop a brain abscess as a result of fighting and antler shed. During antler shed bacteria can enter the body near the pedicle and an abscess begins to form near the skull. As would be expected a deer with a brain abscess exhibits blindness, significant weight loss, circling movements, and drunken-like movements. A deer that is found to have a brain abscess is not suitable to eat.

Chronic Wasting Disease

Chronic wasting disease (CWD): Classified in an infectious disease group as transmissible spongiform encephalopathies (TSEs) that cause brain degeneration in cervids like whitetail deer and mule deer. Similar to mad cow disease, this disease is sometimes called the «zombie deer disease» by some media outlets. It may take months if not years for this prion disease to manifest and it has devastating effects on the animal. This is an always fatal disease. Symptoms include fever, excessive salivation, loss of coordinated movement, and extreme weight loss. CWD spreads from animal-to-animal contact or animal-to-soil contact. Which is how it has spread easily with captive deer herds. Being the social animals that deer are, the disease is prone to spread quickly in wild deer herds too. There is no documented evidence that the CWD can be transmitted to humans. But public health officials at places like the Centers for Disease Control and Prevention still urge caution eating infected venison. CWD has been found all over the United States and Canada. Cases of CWD have also popped up outside of North America in places like Norway. Unfortunately the disease can be spread after the animal is dead because the prion can hide out in the lymph nodes, brain and spinal cord, leading to regulations on bringing those parts into many states.

Arterial Worms

Arterial worms: These white round worms live in the arteries of the whitetail deer. Horsefly bites are how a deer contracts the parasite. A deer’s health can be impacted by the worm taking residence in bone structures causing bone deformities and resulting infections. The jaw tends to be the area most commonly affected. Swelling in this area can lead to food being trapped below the tongue which can lead to tooth loss and secondary infections. Deer infected with arterial worms are still safe to eat.


Mange: While demodectic mange is not as common or as sever as Blue Tongue, mange does affect whitetail deer populations in some states and Canadian provinces. Being a skin disease transmitted by the mange mite it does not impact beyond the skin. All of the expected issues of mange (regardless of species) apply to deer as well: hair loss, puss-filled lesions, and thickening of the skin. Because this wildlife disease does not reside anywhere but on the skin, the meat of a deer with mange is still safe for human consumption.

Nasal Bots

Nasal Bots: This common parasite infests rabbit, squirrel and deer by taking up residence in the animal’s nasal passages. The flies lay their eggs in the animal’s nose, which develop until they are literally sneezed out by the deer where they develop further into adult flies. Most hunters never know their deer has nasal bots until they are found by the taxidermist. Though profoundly yucky to humans these flies don’t cause the deer much discomfort and do not impact the meat.

War Wounds

1War Wounds: Either infected from a misplaced shot or lodged arrow, humans inflict wounds to deer that often result in bacterial infections. Bucks do their share of damage to each other as well and inflict battle wounds that can also result in severe trauma and result in infections. Some animals simply heal around the bullet, arrow, or bone fragment and go on living just fine. Others develop abscesses internally that when found during a harvest, must be carefully handled. While the meat surrounding an infected area should be cut away, the remainder is still edible. However, if not removed carefully and the infected area/fluids leak, none of the meat exposed is safe for human consumption.

Other Diseases & Parasites

Other viruses and parasites plague America’s whitetail deer herds. Liver flukes, bovine tuberculosis, corn toxicity and more result from both natural and man made environments. The spread of certain diseases can take on epidemic forms and wipe out entire herds. The effects can last for generations and transmit across state lines. Herds in high density populations are prone to the greatest exposure and death as a result of their social nature. What have you found while hunting? What is prevalent in your area?

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A New Tick-Borne Parasite That Invades Red Blood Cells: Beware Babesiosis

Imagine microscopic parasites that invade your red blood cells. This is the danger posed by Babesiosis, a little-known tick-borne illness that the CDC has identified as an emerging threat here in the U.S. Babesiosis itself is not new; however, it is a new threat in many areas that until recently had never seen a case of the disease.

Similar to malaria, Babesiosis is caused by microscopic protozoa called Babesia which can reproduce inside red blood cells. Most cases of Babesia infection are caused by Babesia microti, but another type, Babesia divergens, has also been identified and may cause even more serious disease. Two types of ticks, deer ticks and blacklegged ticks, can carry Babesia parasites.

But here’s the big problem: it’s the nymph stage of the tick that’s most frequently responsible for transmitting this parasite. And the nymph stage of a deer tick is very, very small — about the size of a poppyseed, according to the CDC.

You’re most likely to get Babesiosis from the miniscule nymph-stage tick on the left. (Photo: CDC)

Long a well-known disease in animals, particularly cattle, Babesiosis was only spotted in humans as recently as the late 1950s and 1960s. Here in the U.S., Babesia was confined to very specific areas such as Nantucket Island, but in the past few years it’s been identified in a wider and wider spread across the country.

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Where Is Babesiosis Most Common?

The majority of cases of babesiosis reported recently have been in the Northeast and upper Midwest states. New Jersey, New York, other parts of New England, Wisconsin, and Minnesota have been the hardest hit, but recently cases have been reported across the West and in Kentucky and Missouri. Wisconsin issued a health alert for Babesiosis in March. In California, yet another type, Babesia duncani, has recently been identified as responsible for some of the reported cases.

Babesiosis-carrying ticks have a particular fondness for coastal areas, wetlands and marshes, and lake shores. In addition to Nantucket, experts have issued warnings for many other popular vacation spots such as Martha’s Vineyard, Fire Island, Shelter Island, Block Island near Providence, and the east side of Long Island. At the young nymph stage during which a tick is most likely to transmit babesiosis, it’s likely hunkered down in brush, grass, or wooded undergrowth.

When to Worry: Now; Tick Season Is Just Starting

May is Lyme Disease Awareness Month for good reason; ticks are everywhere right now. When it comes to risk of babesiosis infection, peak months are the warmest, typically from June through early October. And of course we’re out walking our dogs, hiking, cycling and camping more during these months, giving ticks plenty of chances to hitch a ride.

Who’s At Risk?

Anyone can get babesiosis, and of course the more you’re outdoors in at-risk areas, the more exposure you have. However, a strong immune system can fight off the parasites, and many people will experience only mild symptoms or none at all. In fact, you may never even know you were exposed.

Those most at risk are the elderly, and those with compromised immune systems such as people with HIV or cancer patients on immuno-suppressive drugs. You’re also at much higher risk if you have liver or kidney disease or have had your spleen removed.

According to Columbia University’s comprehensive report, Babesiosis can be fatal in up to 20 percent of people with such immune-compromising problems.

How Do You Know You’ve Been Exposed to Babesiosis?

Unfortunately, often you don’t. This is because the tick bite that transmits this parasite is so small; imagine the minuscule bite mark left by a nymph-stage tick that is itself the size of a pinhead. So instead, it’s symptoms that are most likely to alert you. And you want to notice them as early as possible, as babesiosis can be very dangerous once it progresses.

Babesiosis symptoms usually set in from a week to a month after a tick bite. The most common symptoms mimic the flu: fever, chills, aches, sweating, headache, and nausea. However, because Babesia infect the red blood cells, you may also experience weakness, fatigue, and other symptoms of anemia.

Doctors may be able to tell you’ve been exposed to Babesia by looking for a pattern of results from blood tests. Many people develop hemolytic anemia from Babesia, which should be a major red flag for the disease. For concrete identification, they have to look at blood smears under a microscope.

Since the same ticks that transmit Lyme disease carry Babesia parasites, the two conditions often go hand in hand, making diagnosis even more difficult. The bottom line is that if you develop flu-like symptoms and have been outdoors in an area where you might have encountered ticks (particularly if it’s in one of the geographic areas with a high incidence of Babesis-carrying ticks), go to the doctor and make sure to present the whole picture.

One last warning: So far, there is no way to test the blood supply for the presence of Babesia. That means blood transfusion is a possible mode of transmission. If you experience symptoms and have recently received donated blood, this is something to be aware of.


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