Experts at the Royal (Dick) School of Veterinary Studies have treated the first cases of cats with abnormally low heart rates brought on by Lyme disease – a bacterial infection transmitted by tick bites.
They found that the heart condition can sometimes be resolved by treating the underlying Lyme disease, and caution that vets consulted for heart conditions should consider whether this infection may be an underlying cause.
In separate cases, two cats with low heart rates and abnormal heart rhythm were referred for treatment to the Hospital for Small Animals.
Both animals had a blocked nerve impulse in the heart, known as third degree atrioventricular block, which is the most common finding in people where Lyme disease affects the heart. In addition, one cat had a tick bite mark typical of Lyme disease infection in people.
Extensive testing indicated infection with the bacteria that causes Lyme disease.
Treatment was successful in one cat, resolving the heart disease completely. Unfortunately, the heart disease was more severe in the second cat, and treatment was unsuccessful.
The team that undertook the study urge owners to maintain preventative anti-tick treatment in animals that go outside, and for vets treating cats with heart abnormalities to consider checking for Lyme disease.
A warming climate is likely to increase the prevalence of ticks and associated diseases in cats and dogs, the researchers warn.
Lyme disease in cats can be challenging to test for, as the bacteria rarely stays in the blood for long, and antibodies generated to fight it may last for as little as a week, so more sensitive tests are needed.
Details of the cases were published in the Journal of Feline Medicine and Surgery Open Reports.
Lyme disease is exceedingly rare in cats and has never before been reported to affect their hearts, let alone been treated successfully. It is important that these cases are catalogued in the scientific literature for the benefit of future cats presenting similarly with low heart rate and abnormal rhythm.
Camilla Tørnqvist-Johnsen, Hospital for Small Animals