Canine Leproid Granuloma Syndrome in Dogs

Canine leproid granuloma syndrome, the most common mycobacterial disease in Australia, manifests as nodules that may be as small as 2 millimeters to as large as 5 centimeters, most often on the ears but possibly on the head and thoracic limbs of your dog. Fortunately, lesions typically regress on their own within one to three months, though treatment with an antimicrobial medication may be required.

Also known as canine leprosy, canine leproid granuloma syndrome is a mycobacterial disease that causes lesions or nodules mainly on the ears of your dog.

A dog with canine leproid granuloma syndrome will display single or multiple lesions that in most cases are on the head, the dorsal ear fold or thoracic limbs (though they can be anywhere on the dog). These nodules are:

• Hard to the touch but painless
• Can be a variety of sizes from 2 mm up to 5 cm in diameter
• Larger nodules may display superficial hair loss
• Very large nodules may ulcerate
• Small nodules present as hard lumps under the skin.

While leproid granulomas can be found on or under the skin, they will not be present in the regional lymph nodes, nerves or internal organs of your dog.

Types 

Most cases of canine leproid granuloma syndrome resolve on their own. There are some cases where a dog will require treatment with an antimicrobial medication to eliminate the disease. A secondary infection with Staphylococcus intermedius may develop in rare cases, which will require treatment in order to be resolved.

Canine leproid granuloma syndrome is caused by a species of mycobacteria that is likely transmitted through biting insects. Short-coated breeds are most likely to be impacted.

Diagnosing canine leproid granuloma syndrome is typically straightforward, especially in breeds of dogs considered at-risk (short-coated breeds, particularly Boxer, Boxer-cross, Staffordshire terriers and Doberman Pinschers) as the nodules often appear in multiples around the head and ears. Your veterinarian will conduct a physical examination of your dog and may choose to confirm the diagnosis by getting a specimen to examine under a microscope using special staining. Depending upon the lesions and if they are causing your dog irritation, your veterinarian may check to see if your dog has a secondary infection with Staphylococcus intermedius.

In many cases, the disease is self-limiting and the lesions will suddenly regress over time (usually within one to three months). It is hypothesized that this is due to a cell-mediated immune response. Lesions may be surgically removed, which will also provide material to confirm the diagnosis. In rare cases, the infection will worsen and lead to chronic and disfiguring lesions. These difficult to treat lesions will often respond to a therapy with combinations of antimicrobial agents that have had success combatting nontuberculous mycobacteria. These include rifampicin, clarithromycin, clofazimine, and doxycycline. A combination of rifampicin and clarithromycin is recommended.

Should your dog have acquired a secondary infection with Staphylococcus intermedius (also known as staphylococcus pseudintermedius), your veterinarian may recommend a first-line antimicrobial like cephalexin, cefadroxil, amoxicillin-clavulanate, trimethoprim-sulfas, lincosamides, and cefovecin. Your veterinarian may request culture and sensitivity testing to better guide treatment in the following circumstances:

• The infection is not responding to treatment
• The infections are deep
• The infections are recurrent or relapsing
• Your dog has had previous courses of antibiotics
• The wounds are not healing
• You or your dog has possibly been exposed to methicillin-resistant staphylococci in a healthcare environment.

If the culture and sensitivity testing shows no sensitivity to first-line antimicrobials, the veterinarian may recommend second-line antimicrobials (and if no sensitivity is shown to second-line antimicrobials, third-line antimicrobials may be recommended). Your veterinarian may recommend a mixture of clofazimine and petroleum jelly to be used as a topical treatment in addition to drug therapy.

Treatment should be continued until the lesions have resolved. Deep infections should be treated for 7-21 days after the lesion has healed, and superficial infections treated for 7 days beyond the skin healing.

Most cases of canine leproid granuloma syndrome will resolve themselves within one to three months. In rare cases, treatment with antimicrobial medication will be required. In cases with a secondary infection with Staphylococcus intermedius, treatment in superficial infections will likely be necessary for 3-4 weeks. In more severe, deep infections, treatment may be required for 8-12 weeks. Your veterinarian may recommend follow-up visits depending on whether treatment is required or if there is a secondary infection.