Coccidiomycosis in a dog

A 2-year-old, spayed, female greyhound named Cabby was presented for a postadoption examination on March 9, 2002. She originated in Arizona and had been adopted via the Greyhound Rescue Society.

On presentation, Cabby was bright, alert, and responsive. The right submandibular lymph node was enlarged (diameter 2 cm), the right external ear was inflamed, and the nail bed of the left front 2nd digit was infected. She was placed on cephalexin (Novo-Lexin, Novopharm, Toronto, Ontario), 250 mg, PO, q12h for 2 wk and then reexamined; the lymph node had reduced in size (diameter 1.25 cm) and the nail bed infection and ear were healed.

On July 13, 2002, Cabby was presented limping on the left hind leg and with a fever of 39.5°C. The clinical examination was unremarkable and she was administered meloxicam (Metacam, Boehringer Ingelheim (Canada), Burlington, Ontario), 0.1 mg/kg bodyweight (BW), PO, q24h. On July 23, 2002, the limp in the left hind limb had not improved, the limb was still painful on extension and sensitive in the area of the groin, and, in addition, Cabby had developed a draining fistula at the site of the left anal gland. An anal gland abscess was suspected and amoxicillin; 500 mg, PO, q12h for 1 wk, was prescribed; after 3 d, the discomfort and the discharge had decreased.

On August 6, 2002, Cabby was checked again. Her left hind limb lameness was worse and she was again febrile (40.5°C), with persistent drainage from the peri-anal fistula.

The fistula was probed to a depth of 3.5 cm. A swab from the fistula was submitted to a veterinary diagnostic laboratory (Calgary Central Laboratory for Veterinarians). Radiographs were taken of the pelvis and abdomen. Blood was also collected and submitted for a complete blood cell (CBC) count, biochemical analysis, and serological testing for fungi.

The pyogranulomatous discharge from the fistula contained spherules of Coccidiodes immitis. Results from the CBC count showed a monocytosis (1.730 × 109 cells/L; reference range, 0.000 to 0.980 × 109/L) and a basophilia (0.111 × 109 cells/L; reference range, 0 to 0.100 × 109/L). Results of the blood biochemical analysis revealed a severe hyperproteinemia (86 g/L; reference range, 54 to 71 g/L) due to an exaggerated hyperglobinemia (62 g/L; reference range, 20 to 40 g/L). The systemic fungal panel was positive for antibodies to Coccidiodes (+1:16). As low grade infections with Ehrlichia canis are common in dogs of the southern USA, an antibody titer for E. canis was determined and found to be negative. The pelvic radiographs showed granulomatous osteomyelitis.

After Cabby’s condition had been discussed with the owner, Cabby was administered ketoconozole, 5 mg/kg BW, PO, q12h. She was also placed on a diet of canned puppy food (Medi-Cal Development, Veterinary Medical Diets, Guelph, Ontario) to augment her diet, as ketoconozole can act as an appetite suppressant. Cabby responded well to treatment; her temperature was lower (39.2°C), and she was bright and eating well. The treatment will be continued for a minimum of 1 y, after which her condition and treatment will be reassessed.

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The desert southwest (Arizona, New Mexico, Southern California) is the hotbed for coccidiomycosis (Coccidiodes immitis) in the United States. “Cocci” or “Valley Fever” (VF) is caused by a fungus that lives in the desert soil and forms spores when released into the air. The digging of building foundations and pools helps to release the spores more quickly. Periods of rain, which cause fungal growth, are usually followed by more cases of VF. The spores are inhaled by humans, dogs, and horses (cats seem to be resistant), very frequently causing the disease. Any dog that breathes air in an endemic region can become infected. There is no vaccine.

Greyhounds seem particularly susceptible to VF, perhaps due to their normally low white blood cell count. Natural immunity plays a part in determining which dogs contract VF (a new arrival to the area is more susceptible than a dog that grew up there).

Valley Fever is a disease that can be obscure and may progress before the owner sees sufficient reason to visit a veterinarian. Some dogs display no specific signs, especially early on, appearing to be not as well, eating inconsistently, or losing weight. Despite the name, half of dogs with VF have normal temperatures at presentation. They may, however, run fluctuating fevers at home and have times of appearing not as well, interspersed with times of lethargy, and inevitably go on to develop more specific signs, if their condition is undiagnosed and untreated. The most common signs are poor appetite, weight loss, lameness, bone pain, spinal pain, and coughing. In the early (primary) form, the fungus infects the lungs, then moves on to infect the bones (secondary form). Lungs and bones are affected in most cases; other systems that can be affected are the central nervous system (CNS), eyes, and, less commonly, the heart or skin.

The coughing stage is seldom seen in greyhounds; most cases present with bone involvement or nonspecific illness and weight loss. Other dogs tend to present with equal proportions of the lung versus the bone form.

Of particular concern with greyhounds is that, on radiographs, VF bone lesions resemble osteosarcoma. Lesions can be either osteoproliferative or osteolytic, so it is important to obtain an antibody titer to C. immitis. In fact, a titer should be obtained for any greyhound from Arizona that is sick for any reason.

Ketoconazole is the first line of treatment. It is used at a dose of 5 mg/kg BW, q12h, with food. Minimum treatment time is 1 y, unless there is only lung involvement, in which case it is 6 mo. Treatment is continued until titers are negative and radiographs are clear (if bone has been involved).

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In the first 2 to 3 wk of treatment, the dog is usually anorexic, due both to the disease and to the ketoconazole. Ketoconazole is an appetite suppressant because it depresses steroids in the body, which is why it can be used as a treatment for Cushing’s disease. Dogs may have to be force fed through the first few weeks to ensure that a full dose of medication is administered, thereby keeping them from losing any more weight until they begin to improve. Relapses are rare in a dog that is on full dose medication; they are more common when medications are being discontinued.

If a dog vomits even when ketoconazole is given with food, try itraconazole at a dose of 2.5 mg/kg BW, q12h. The best medication for dogs that are quite sick with VF is fluconazole at a dose of 2.5 mg/kg BW, q12h. Sometimes, it is helpful to use fluconazole for the first 1 to 2 mo and then to revert back to ketoconazole for long-term treatment. Most dogs tolerate fluconazole much better than ketoconazole or itraconazole, and it is the drug of choice for CNS involvement. Regardless of which medication you use, it is critical to maintain calorie input.

Some veterinarians recommend adding methylsulfonylmethane (MSM) when treating VF, others add lufenvron (Program, Novartis Animal Health, Mississauga, Ontario), 409.8 mg, PO, q24h, but this makes treatment relatively expensive. Others give vitamin C (500 mg) with the medication, as antifungals work better in an acidic stomach.

With really sick dogs, amphotericin B is an option. It has to be given over a period of 12 h, first with 1 L of 0.9% saline to flush, followed by 1 L of 5% dextrose. Before each treatment, a urinalysis should be done and the blood urea nitrogen determined. The full course of treatment is twice weekly for 2 mo. Some dogs will need to be maintained on oral medication after the amphotericin B treatment has been completed. Veterinarians who have used it develop a sense of risk versus benefit. It certainly is a stronger and faster working drug for seriously ill patients.

Valley Fever can relapse, even if the titers are negative. Some veterinarians consider that the VF is only in remission, not cured, until the dog has gone without a relapse for several years. Greyhounds seem to suffer more with VF than do other dogs. Weaning dogs off the medication seems preferable to stopping the medication entirely and having the dogs have a relapse, which can sometimes be fatal.

Approximately 1/3 of dogs with VF will die, 1/3 are cured, and 1/3 are alright as long as medication is continued.