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Declining moose populations linked to brain-eating parasitic worms

Moose, the majestic giants of North America, are facing a silent threat – a parasitic worm that could be playing a significant role in their decline. New research from Washington State University (WSU) has shed light on the underestimated impact of Eleaophora schneideri, also known as the arterial worm, on these iconic animals.

Parasitic worm’s hidden moose invasion

The researchers found that Eleaophora schneideri, a parasitic roundworm, infests the brains of moose in southeastern Idaho. The microscopic early life stage of the worm, called microfilariae, scatter throughout the brain, causing subtle but widespread damage.

“The microfilaria are just scattered throughout their brains, and even though the damage from each is miniscule, they’re basically shot-gunning the whole brain,” explained Kyle Taylor, a pathologist at WSU’s Washington Animal Disease Diagnostics Laboratory (WADDL).

“We hypothesize the cumulative effects of large numbers of microfilariae in the brain may be associated with increased morbidity or chance of mortality, with mortality more likely in cases with larger numbers of worms.”

Moose brains infected by parasitic worms

The research examined 61 recently deceased moose in Idaho. The researchers found no evidence of infection in northern Idaho moose or juveniles. However, a staggering 50% of adult moose in southeastern Idaho were infected.

Of those infected, three had damage to the tips of their ears. This condition is directly attributed to E. schneideri infection. Additionally, four infected moose exhibited atypical behavior before their deaths.

This is the first time researchers have identified this level of parasitic infection in moose. This finding raises alarming questions about the overall health and survival of these populations. The high infection rate suggests a significant threat to moose in the affected regions.

Researchers now face urgent challenges in understanding and mitigating this new risk to moose conservation.

A silent killer

The arterial worm spreads through tabanid flies like horse and deer flies. Mature worms can grow up to 4.5 inches long. They live in the carotid arteries of the head and neck. There, they mate and release microfilariae into the bloodstream.

Infection can cause elaeophorosis, which disrupts the moose’s circulatory system. This can lead to blindness, atypical behavior, and damage to the ears and muzzle. In severe cases, it can even cause death. Other species like deer and elk can also be infected. However, they typically show minimal to no signs of infection.

Geographic spread of parasitic worms

The experts also found that E. schneideri is widespread in southeastern Idaho. This aligns with the parasite’s prevalence in neighboring regions of Montana and Wyoming. The distribution of E. schneideri coincides with populations of mule deer, which are natural hosts of the parasite.

The implications of this research are far-reaching. Moose populations have been declining for years across North America. Contributing factors include habitat loss, climate change, and predation. The discovery of this widespread parasitic worm infection adds another layer of complexity to the moose population. This finding underscores the need for further research and monitoring.

Understanding the full impact of E. schneideri is crucial for effective moose conservation efforts. Scientists must now investigate how this parasite interacts with other factors affecting moose populations. This comprehensive approach will help develop strategies to protect and preserve these iconic animals.

Future research directions

The next steps for researchers include developing tests to determine if live moose are infected with the parasitic worms. This would allow for targeted interventions and management strategies to protect these vulnerable populations.

“We really need to have an understanding of all the issues related to moose population decline, and this parasite appears to be a factor,” noted Taylor.

The story of the moose and the arterial parasitic worm starkly reminds us of the interconnectedness of ecosystems and nature’s delicate balance. Parasites, often overlooked and underestimated, can profoundly impact wildlife populations.

Additionally, we must acknowledge their role as we face conservation challenges in a changing world. Understanding parasites is crucial to protecting our planet’s biodiversity. By studying these hidden threats, we can better protect and preserve diverse wildlife.

The study is published in the Journal of Wildlife Diseases.


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