Parasites have moose in their crosshairs

New Hampshire sits right on the line — just southern enough to support a deer population, and just northern enough to also spot the occasional moose. But as recent milder winters have caused the local deer population to perk up, the local moose has seen only a stable and, in some parts of the state, declining population. Deer population in the southern half of the state ranges from 10 to 13 deer per square mile. For moose, it’s as low as less than 0.25 moose per square mile in the southwest portion on the state, and 0.1 moose per square mile in southeast New Hampshire. Up north, there are fewer deer, but there are as many as two moose for every square mile.

The two situations are not unrelated, according to Kristine Rines, the leader of the Moose Project at N.H. Fish and Game. As the deer population thrives, so do some of the parasites that they carry. For humans, the big concern is ticks and Lyme disease. For moose, it’s a more deadly prospect: Brainworm.

Brainworms, formally known as parelaphostrongylus tenuis, are a parasite that are carried by the white-tailed deer population without any real visible effects. The larval form are deposited with the deer’s scat, and picked up by local snail and slug populations that feed off it. Then, when moose accidentally consume snails and slugs during their foraging, the parasite finds a host that is not so capable of living with the effects, said Rines in a phone interview Thursday.

The parasite passes through the gut into the bloodstream, navigates to the spinal cord and is carried into the brain. The minute the parasite hits the spinal cord, moose begin to show the effects, which are significant and eventually deadly, said Rines. The moose can go blind, deaf, have difficulty walking or experience paralysis.

“It’s not a fun way to go,” said Rines.

But the truth of the matter is that brainworm is mostly a problem in the southern portion of the state, where the deer population is the highest. And that’s a section of the population that analysts have never particularly expected to thrive, said Rines. Moose have always been more prevalent the higher north you go. About 12 years ago, when Fish and Game started noticing an issue with the northern population of moose, a major reason for concern began to develop. It’s still a parasite causing the issue, said Rines, but a more commonly-known one this time — the winter tick.

Just over a decade ago, habitats were good, food plentiful and the moose population should have been on the rise. Instead, it was stagnating. The cause was the increase in the winter tick population.

Again, the delay and early-leaving winters were the major factors in the thriving parasite. Ticks that find homes on moose and other wildlife are not landing on the cold snow and falling victim to days of freezing weather during the early and late winter months. The warmer weather over the past several years is giving them a chance to lay and hatch eggs, causing an increase in their population. Moose aren’t succumbing to the diseases that winter ticks carry, but to the sheer volume of them on their bodies. One moose alone can carry up to 100,000 to 120,000 ticks. The drain of blood can cause anemia, secondary infections and can lead to hypothermia and pneumonia.

“The animals die in fairly large numbers,” said Rines. And there’s no real solution to the problem, she added.

Treating a wild animal population with tick controls is simply not feasible, and would have to be done every year. Both ticks and brainworms are large contributors to the fact that the moose population in New Hampshire is down to about half of what it was at its all-time high.

Both these parasite issues are exacerbated by shorter winters which have allowed the deer — and thus brainworm — and tick populations to accumulate higher than usual numbers, said Rines. “The absolute thing that needs to be done is that we need winter to come back,” she said. “People need to be a little more interested in what’s going on with our natural world.”

Ashley Saari can be reached at 924-7172 ex. 244, or She’s on twitter @AshleySaari.

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