GENETIC MUTATION AND DRUG TOXICITY

The remarkable recovery of a dog nursed back to health from the brink of death recently highlights the value of a simple genetic test that can help owners determine if their pets are vulnerable to what in most cases is a safe, commonly-used drug. Bristol, a 4-year-old Australian Shepherd, was brought to the Hospital for Small Animals , barely responsive and experiencing persistent seizures. The owner suspected Bristol was suffering from severe ivermectin toxicity, a condition in which ivermectin, the active ingredient in some heart-worm prevention medicines, crosses the blood-brain barrier and causes neurological damage. Bristol required immediate and aggressive care, including the assistance of a mechanical ventilator. She also underwent a brain MRI to rule out other causes of her condition. Although Bristol began to breathe on her own within 10 days, she remained unconscious for three weeks. Eventually, she began walking with the assistance of a cart and leg splints, and later began walking under her own power with support from hospital staff. After a month of treatment, Bristol regained her normal personality traits and the ability to walk, eat and drink on her own. One or two cases of ivermectin toxicity occur each year and they are most frequently the result of accidents, such as when dogs are exposed to higher-dose ivermectin products intended for horses. Although products containing ivermectin are typically safe and effective, many white-footed herding breed dogs like Bristol have a genetic mutation that makes them sensitive to it and several other drugs, including some common chemotherapy drugs.The gene mutation test would enable owners know for sure if they could safely use some of these other drugs, many herding dogs undergo a simple genetic test to determine if they have a mutation in the multidrug resistance (MDR1) gene. Dogs could be indirectly exposed as in the above case that the dog had access to feces of a sheep that was recently dewormed using ivermectin. This also highlights the need for owners to be vigilant when their dogs are in certain settings, such as on farms or in barns, where other animals might have been treated with high concentrations of ivermectin. Source Tufts University.