A Deadly Brainworm Is Infecting Moose Across The US. But We Can Finally Track It.

A moose in Minnesota unexpectedly wanders onto a busy road. Disoriented and dizzy, she fails to recognize the imminent danger posed by a rapidly approaching semitruck.

While the direct cause of her demise is the collision with 13 tons of steel, the underlying factors are infinitely more complex. Hidden inside her brain is a parasitic worm, a grim harbinger of doom for both the moose and the truck driver.

This worm, known as the brain worm, scientifically termed Parelaphostrongylus tenuis, poses a serious threat to various herbivorous species, including moose and elk. Its ability to invade and disrupt the brain has severe health implications, often leading to death.

Related:

As researchers in parasitology, we have investigated the impact of these worms on moose populations in Minnesota. By tracking the infection and spread of this parasite within wild populations, we aim to aid wildlife managers in sustaining these populations while minimizing transmission to livestock and other wildlife.

Notably, while white-tailed deer can harbor these parasites without experiencing any adverse effects, the brain worm can inflict serious harm on populations of species such as moose and elk that lack resistance to the parasite. However, tracking this disease in the wild is a significant challenge.

The Disease Cycle

White-tailed deer, serving as definitive hosts for the parasite, shed the worms into the environment through their feces. Snails and slugs subsequently consume this larval form, allowing the parasites to develop within them and later infect other deer species, moose, elk, and even cattle.

For researchers like us in the field of parasitology, the primary challenge is detecting the disease prior to irreversible damage to its host. The exclusive shedding of the parasite by white-tailed deer means we cannot detect the presence of the worm by analyzing the fecal matter of moose or other susceptible species.

Once an animal begins to show symptoms, it’s often too late for recovery. Diagnosis typically only occurs post-mortem, by retrieving and analyzing the carcass to identify the parasite lodged within the central nervous system.

Moreover, the identification of a slender, threadlike worm against the vast network of a moose or elk’s nervous system proves to be painstakingly difficult. Often, wildlife biologists rely on microscopic evidence indicating parasitic migration within the central nervous system and through genetic material remnants left behind by the worm.

Diagnostic Confusion

The challenge intensifies as other types of worms, such as Elaeophora schneideri, can exhibit similar symptoms and also affect Minnesota moose.

This arterial worm resides primarily in the necks of black-tailed and mule deer, and like P. tenuis, it can cause significant harm in non-adapted host species.

Consequently, biologists diagnosing moose based solely on visible clinical signs could mistakenly attribute symptoms to the wrong parasitic infection. Accurate assessments are essential, as differing transmission methods between these parasites necessitate distinct management strategies for control and prevention.

Even with microscopic examination of body samples, misidentification risks persist. The most reliable method for achieving accurate diagnoses involves genetic analysis of the parasite’s DNA, which can clearly differentiate between P. tenuis and E. schneideri.

Serological Testing

Genetic analysis is a vital tool for monitoring disease prevalence in wildlife populations, but it cannot assist in diagnosing living animals. Our research team, alongside specialists from the University of Tennessee College of Veterinary Medicine’s molecular diagnostic lab, has developed an innovative test to diagnose infected animals while still alive.

When an animal is infected with brain worm, its immune system generates antibodies – proteins that combat the parasite. Our serology test detects these antibodies in blood samples.

Wildlife health specialists collect blood from suspected infected animals, which is then sent to our laboratory. There, we screen the sample for specific antibodies targeting P. tenuis to ensure no misdiagnosis occurs.

This novel testing method, now operational for analyzing samples sent from various locations nationwide, allows us to monitor populations of moose and elk for this parasite, detecting its presence while the animals are still alive and without the costs of genetic testing.

Ripple Effects from Testing

In our earlier scenario, when the Minnesota moose meets her tragic end from a truck collision, wildlife officials promptly retrieve her carcass and take a blood sample for diagnostic testing. This sample is sent to the University of Tennessee, where it adds to a vast archive of specimens collected from moose, elk, and even caribou across North America.

Each entry contributes to advancing our understanding and effectiveness of the serological test.

The test also screens populations in previously unmonitored areas for P. tenuis. If results show positive, biologists are alerted to a potential spread into new territories, allowing proactive measures to be taken.

Upon early detection in a novel population, wildlife managers have the opportunity to take preventative actions against the spread. Strategies may include reducing the number of snails and slugs through controlled burns or adjusting hunting regulations to manage white-tailed deer populations.

Looking ahead, we aspire for researchers beyond our team to leverage the methodologies from this serological test to forge similar diagnostic tools targeting other infectious agents linked to RNA or DNA.