A new case report, conducted by the Internal Medicine team at Lumbry Park Veterinary Specialists and supported by the University of Edinburgh, has document breakthrough treatment possibilities for dogs infected with Mycobacterium avium.
Mycobacterium avium infections in dogs are rare in the UK, although slightly more common in cats. There have been only 49 published cases of M. avium worldwide. However, cases are increasingly being diagnosed in companion animals in the UK.
Once diagnosed with MAC mycobacteriosis, the prognosis for affected dogs is usually poor; most die or are euthanised. Mycobacterial granulomas are often found in several organs, including the spleen, liver, lung, bone marrow, and assorted lymph nodes.
Choosing to treat dogs suffering with M. avium infection is a complex decision due to the requirement for significant treatment commitment, the risk of relapse, zoonotic considerations (particularly with immunocompromised clients), and appropriate antimicrobial stewardship.
The new case report reviewed the long-term outcome, diagnostic imaging follow-up and treatment of two dogs diagnosed with M. avium infections diagnosed at Lumbry Park. It also compared the findings from their initial diagnoses to those of their relapses.
The findings highlighted that a viable treatment option is available that can lead to clinical remission, in the form of a multi-drug combination antibiotic therapy – including fluoroquinolones, rifampicin, doxycycline, clarithromycin, and a protocol containing ethambutol.
However, they also documented relapses following discontinuation of treatment – indicating the eradication of the organism is unlikely, though relapses resolved when restarting the multidrug combination therapy.
The case report also revealed the potential for patients treated for M. avium infections to achieve long-term survival. Both Lumbry Park cases were clinically well up to 4 years after diagnosis with no evidence of clinical disease but required ongoing therapy.
Victoria Coates, internal medicine resident at Lumbry Park who led the study, said: “To our knowledge, this report is the first to describe the long-term outcome and diagnostic imaging follow-up in two dogs diagnosed with Mycobacterium avium treated with multidrug combination therapy. Previously published cases included non-favourable outcomes with progression of disease and euthanasia, and lack longer-term diagnostic or treatment information.
“Our findings document a huge step forward in the successful treatment and management of M. avium infections in dogs. And we hope that they could lead to improved chances of survival for patients suffering with this previously fatal disease.
“However, our findings also illustrate the challenges of treatment of canine M. avium – including the need for multi-antibiotic potentially life-long therapy and high risk of relapse – all of which should be considered when approaching management of a case.”
The Long Term Follow Up Of Two Dogs Diagnosed With Mycobacterium Avium, Victoria Coates, Samantha Taylor, Clarisse D’Août, Conor O’Halloran, Cesar Sanchez Jimenez, has been published in the BSAVA’s Journal of Small Animal Practice. Long-term follow up of two dogs diagnosed with Mycobacterium avium | BSAVA Library.
