Cash
| Martha Love had a lot to be
thankful for Thanksgiving 2009. Her
1-year-old Miniature Australian Shepherd, "Cash," walked out of the WSU
Veterinary Teaching Hospital on November 17 after being hospitalized for 26
days. Eight of those days Cash was in a coma on a mechanical breathing
ventilator.
Martha first noticed Cash wasn't feeling well after they visited several
horse stables. On the evening of October 21 Cash began staggering and
quickly lapsed into a coma. He was first rushed to Pets ER for supportive
care and the next morning presented to Dr. Colin Bonnett, a WSU alumnus in
Montana, who placed a breathing tube because Cash was having difficulty
breathing. Dr. Bonnett continued supportive care, but immediately referred
him to the WSU Veterinary Teaching Hospital. Cash was flown by chartered
plane to WSU. Kimber Feher, a veterinary technician, volunteered her time to
accompany Cash and breathed for him using a manual breathing ventilator
until he arrived safely in Pullman.
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Cash in
the
Intensive
care
unit at
WSU
|
Because of his symptoms, the veterinary team suspected that Cash had
eaten ivermectin, a commonly used drug likely given to the horses at one of
the stables. Ivermectin, which is used to remove worms or prevent heartworm
disease, is safe at prescribed doses for many animals, including dogs. Large
doses of ivermectin can be toxic or even deadly. But some dog breeds have a
genetic mutation that makes them more susceptible to ivermectin toxicity,
even at prescribed doses.
Dr. Katrina Mealey at Washington State University discovered the MDR-1
gene mutation that causes increased sensitivity to certain drugs, including
ivermectin. The MDR-1 gene helps create a protein called P-glycoprotein that
pumps drugs and toxins out of the brain. Without this protein, high levels
of certain drugs can accumulate in the brain impairing function, leading to
coma and an inability to breathe that can result in death. Dogs with the
MDR-1 gene mutation do not produce P-glycoprotein or do not produce enough
of the protein to effectively pump particular drugs, which leads to
toxicity. Ivermectin toxicity causes the nervous system to shut down.
Tests confirmed that Cash had high levels of ivermectin in his system and
had the MDR-1 mutation, which made him more susceptible to poisoning. The
MDR-1 mutation is more common in some breeds of dogs including the Collie,
Australian shepherd, Miniature Australian shepherd, Shetland sheepdog, Old
English sheepdog, and Long-haired whippet. Approximately 50 percent of
Australian Shepherds and 70 percent of Collies have this mutation.
Cash
received around the clock intensive care
from fourth year WSU veterinary students,
ICU veterinary technicians, and Dr. Heather
Wright, a neurology resident. While
recovering Cash remained on a ventilator to
breathe, he was given nursing care to
prevent bedsores and infection, and was fed
intravenously. His team of doctors included
Dr. Annie Chen-Allen, a board certified
neurologist; Dr. Katrina Mealey, a board
certified internist and pharmacologist; and
Dr. Patricia Talcott, a board certified
toxicologist. Cash gradually
emerged from his coma, began eating on his
own, playing with his toys, and walking
without assistance. Now fully recovered,
Cash is home with his family and he is not
expected to have any lasting effects from
the ivermectin.
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Cash with from L to R: Kristen Davignon, Sarah Giebel, Dr. Heather
Wright, Aimee Ratzlaff, and Jennifer Hylin |
For more information about the MDR 1 mutation including how to test your dog
for this mutation, please visit
http://www.vetmed.wsu.edu/depts-VCPL/
See Cash's story on Spokane TV station
KHQ-TV by clicking the arrow below.
