Red rim elk die-off

Red Rim Wildlife Habitat Management Area

1. Old Daley Ranch owned by WGFD

2. Approx. 50 section (1 section = 1 square mile)

3. 10 miles southwest of Rawlins, WY

4. Important pronghorn winter range

5. Not typically used by elk, but 800 elk on the area in winter 2004

6. 5th year of drought

Feb 8, 2004

1. Coyote hunters find 2 down elk alive, report to WGFD

   1. Elk had been partially depredated by coyotes

2. Elk euthanized and taken to WSVL

3. At necropsy:

   1. Subcutaneous hemorrhages (bruises)

   2. Degenerative myopathy

So What?

1. Differential diagnoses?

   1. Capture myopathy? (Snowmobile chased elk around)

2. Is it important?

Feb 14, 2004

1. 7 additional down elk found

2. WSVL and WGFD vets go to field:

   1. Elk down, unable to rise, but alert and responsive

   2. Normal TPR

   3. Seemed to progress to depression and death

   4. Necropsies - like that at lab

3. Blood & urine samples collected

   1. Myoglobin was NEGATIVE 

4. Found 50 elk entangled in barbed wire fences (couldn’t jump)

5. Red urine seen in snow

   1. Not due to myoglobin 

   2. Urine is normal

What might cause red urine?

1. Could any of these causes relate to clinical signs?

2. Any new ideas?

Feb 20, 2004

1. 63 elk confirmed down or dead

2. WGFD, WSVL pathologist & toxicologist & student return to field

3. Clinical and pathologic picture remained the same

4. Toxicologist and game warden notice lichen 

5. Only consistent lesion:

   1. Pale and not dark red in muscle

   2. Degenerative myopathy

6. Ruled out majority of possibilities

Feb 29 & Mar 1, 2004

1. Over 280 confirmed cases

2. 4 live elk brought to WSVL for treatment

   1. Assurance for biologists/wardens

   2. Diagnostics

   3. Political pressure

3. Treatment attempted:

   1. Vitamins, minerals, fluids, penicillin,dexamethasone

   2. No response to any treatments (all died)

4. ABADRL ruled out Tick Paralysis 

   1. Found immense amount of ticks in elk (but this was in winter!)

   2. The reason why there was so many tick because elk could not brood

WSVL toxicologist: lichen hypothesis

1. Literature from 30s in cattle and sheep

2. Dr. Cook had strong reservations

   1. Not documented since, clinical picture, mouse trials

3. Then came results of rumen analysis:

   1. Lichen was major part of diet (which matched the lichen the toxicologist found)

   2. Tumbleweed shield lichen

WGFD fed lichen to elk from NER

1. Red urine noted in expt. elk at 4days

2. At 7 days 1st elk down

3. At 10 days elk down

4. 3rd elk stayed perfectly healthy but would not eat lichen (even mixed with alfalfa hay) and lost a lot of weight

At the same time:

1. Elk migrated out of red rim area

2. Down elk and losses stopped

Elk population

1. Had to reduce hunting license

2. Population bounced back in 2 years

What is lichen?

1. Commensal between algae and fungus

2. Many different species

3. Some are important parts of certain wildlife diets

4. Elk documented to eat some other spp. of lichen

Tumbleweed shield lichen

1. Xanthoparmelia chlorochroa

2. Very common ground lichen in WY

3. Early literature: Parmelia molluscula

   1. Toxic lichen year round (toxic dose: 1% of body for 5 days)

What is the toxic compound?

1. Usnic Acid? Hypothesis in 50s

2. Usnic Acid associated with liver damage in humans, not with muscle or nerve damage

3. The lichen contains high levels of Usnic Acid

4. But there may be another compound responsible for the paresis

Occurrences since 2004

1. Tough to predict

2. Elk occasionally winter in red rim

   1. Outbreak in 2008

3. Does the lichen contain variable amounts of toxin in different seasons or years?

Rebecca Dailey PhD

1. Sheep are affected by the lichen

   1. Clinical picture similar to elk

2. Toxicity of the lichen varis

   1. Season and location

3. Red urine occurs in all sheep fed lichen

   1. Regardless of severity of paresis

4. Usnic Acid can be toxic to sheep

   1. Produces a myodegenerative disorder similar to lichen toxicity

5. Very high does required

   1. More than they can eat

6. No hepatotoxicity even at very high doses

7. Probably a combination of usnic and salazinic acids

Livestock implications

1. Original documentation in sheep & cattle

2. No documented cases since the 30s until elk die-off

3. Seven documented outbreaks since

   1. Most had red urine

4. Lichen is very common

5. Qiute possibly more occasional casses

Red urine

1. Unrelate to myopathy

2. No kidney lesions

3. Nurinalysis normal

4. Red urine result of pigment excretion from the lichen

5. Remains a diagnostic indicator for potential lichen toxicosis

Where do we go from here?

1. Identify wildlife species susceptibility

2. Identify additional toxic compounds

3. Identify “toxicity test” of lichen

4. Develop true diagnostic assay

5. Current management is working, so little interest in funding above

Human implications

1. Scientists: interesting, intriguing, exciting!

2. Wildlife managers: saddening, disheartening, stressful

Summary

1. 326 confirmed cases

2. Estimate of 400-500 cases

3. Limited to elk

4. Feb to early March 2004

5. Diagnosis: Tumbleweed shield lichen toxicity

6. 84% of loss was adult female elk

Take home message/discussion

1. When large numbers of animals are dying in a short time frame: think toxins!

   1. Why?

      1. EVERYBODY CAN GET EXPOSED AT THE SAME TIME

2. Why is it unlikely to be infectious?

   1. Time it takes for replication

      1. Some exceptions: Anthrax (environment based)

3. What are the wildlife population-level impacts of toxins?

   1. Significant instant population impact, but bounces back quite quickly (very little long term population impact)

      1. Unless toxin persists

4. Does it matter if it is a natural or man-made toxin?

   1. No. Its all toxin