The case of TB in a Yellow-napped Amazon was a straight forward case that was easy to diagnose. The bird had a very clear radiographic lesions and a biopsy quickly identified they granulomas in the air sac as being acid fast positive. The diagnose was made within 48 hours. The next case shows how difficult it can be to diagnose TB.
An 8yr-old (Double) Yellow Head was presented for feather picking, decreased appetite and talking less. Four weeks before I saw the bird it suddenly started to pull out its feathers in "fits". The owners described episodes of frantic feather picking (day and night) as if the bird had an overwhelming itchy or burning sensation. They took the bird to an avian veterinarian who did a CBC (Complete Blood Count) and said the with blood cell count was elevated. The bird was put on an oral antibiotic and an antihistamine dissolved in the water. No response was seen after two weeks.
On physical exam, I found a healthy bird except for the loss of the cover and a few down feathers on the chest and sides. Skin and feather follicles were normal with no evidence of skin multilation. At this point some of the possibilities could be
It seemed unlikely to be infectious since no true skin lesions could be seen. A gram stain of the feather follicles showed gram positive rods, but this can be normal. (A culture of the feather follicles did not grow any bacteria). A CBC was done which showed a normal white blood count.
It also seems unlikely to be metabolic in nature. The bird was on an adequate diet and blood chemistries showed normal liver and kidney function.
It appeared not to be psychological as the species is not one to commonly feather picking and the frantic nature of the feather picking is not characteristic of this type of behavioral problem.
Now you may have noticed that I have stated that all the above reasons were "unlikely". Even though it seems this way none of ;the possibilities can truly be ruled out. My true thoughts at this time were that there was one subtle metabolic problem or a tumor stimulating the feather picking behavior.
The feather picking was just a secondary clinical sign for a primary (more serious) problem. The owners did not want to proceed with anymore diagnostic test, so the bird was put on a different oral antibiotic to see if any response would occur.
No response was seen in two weeks so the bird was anesthetized and X-rays taken. A fecal sample was also obtained for an acid fast stain. The bird had difficulty breathing under anesthesia as if it had a pulmonary problem, but no breathing abnormalities were noted at rest before or after anesthesia.
The X-rays were sent to an avian radiologist who saw evidence of a low grade pneumonia (the reason for the breathing problem under anesthesia) a slightly enlarged spleen, thickened intestinal loops, and a newly healed fracture of the right radius(one of the wing bones). By the time I had a chance to discuss these finding with the radiologist, I got back a positive acid fast smear result. The radiologist felt that all of ;the radiographic changes could definitely be secondary to tuberculosis. The organism can infect the intestines, spleen, lungs and cause lesions of the bone leading to pathological fractures. These fractures can go unnoticed if they occur in small bones such as the radius. The owners were surprised to hear he had a fracture in the recent past as they'd not notice any signs associated with it.
Since tuberculosis seemed to be the reason for the feather picking, treatment was discussed with the owner. The public health risks, length of treatment and the cost, were all reviewed. The owners elected to try treatment, so the bird was started on some of the newer drugs used to treat TB in humans (Seromycin, Lamprene and Myambutol). The family members were all tested for TB and found to be negative. A fecal acid fast culture was done on the bird to see if we could identify the type of TB organism present. The culture did not grow any organisms after 8 weeks. A skin biopsy is pending to see if there are any acid fast organisms in the feather follicles.
As of this writing the bird has responded somewhat to the medication. It is eating better, talking normally and the "fits" of feather picking are diminishing. It may take months of treatment to see complete resolution of the clinical signs
The test that proved to be most valuable was the one that I had run almost as an afterthought.TB caused a bone to be broken, fits of feather pocking, decreased appetite and less talking in a Yellow-head.Mycobacterium avium is a causative agent that invades the bird excreted from lesions and spread from feces and urine, and can survive in cages and the aviary for about 5 months.
*From the Birds Eye View, Smoky Mountain Cage Bird Society, July/August 92 Joyce Cope, ed. Chris is a vet at the Haywood Animal Hospital, and writes for the newsletter.
