by Veterinary Practice News Editors | April 17, 2009 4:06 pm
"We're seeing much fewer respiratory problems in pet birds today than we did 10 or 15 years ago, and that's primarily due to improved husbandry," said Brian Speer, DVM, Dipl. ABVP, who has a practice in Oakley, Calif.
Some of the deadliest respiratory diseases in times past, such as pox, are rarely seen today, Dr. Speer said.
But, bacterial and fungal pneumonias, aspergillosis and severe respiratory distress are still common.
This, Speer speculated, is in big part caused by an increase in "germ phobia" in our society. "A lot of pet owners are scrubbing their bird's cage daily with very powerful disinfectants," he said. "This can weaken a bird's defense mechanisms and make it susceptible to innocuation with an opportunistic infection."
The incidence and types of respiratory disease seen vary depending on geography and whether the birds are kept in aviaries or as pets. "Bird owners in the Midwest or South, where there's higher humidity, are going to have a greater incidence of respiratory disease than bird owners living on the West Coast, where it's drier," said Larry Nemetz, DVM, a birds-only veterinarian in Santa Ana, Calif.
Large indoor flocks are at a greater risk for bacterial and fungal infections than single-kept pet birds because the ventilation in indoor aviaries is usually poor and the spread of a disease can be rapid since the number of susceptible birds is higher, Dr. Nemetz said.
On the other hand, pet birds are more susceptible to inhaling airborne toxins because these birds are more often exposed to such things as household cleansers, incense and air fresheners, kerosene heaters, second-hand cigarette smoke and overheated cookware.
Birds housed in outdoor aviaries or flights usually have plenty of air circulation so airborne toxins are far less an issue for them.
Treatment for birds that have inhaled airborne toxins is difficult at best. "In most cases of respiratory toxins, the bird dies before getting to my office," said Sam Vaughan, DVM, Dipl. ABVP, in Louisville, Ky. "It's hard to save a bird that has inhaled airborne toxins. You need to diagnose them quickly and really act fast."
A new tool being used to treat birds with severe respiratory distress is the bronchodilator. In Nemetz's experience, the use of terbutaline has effected great improvement within 20 minutes in several cases.
"The bronchodilators work to relax smooth muscle around the bronchi and help get those bronchi to open and let more air get past to the deeper tissue for oxygen exchange," he said.
For more severe cases and for those birds that do not respond to intramuscular administration, terbutaline can be nebulized and administered to the intubated, anesthetized patient, Nemetz said.
"The anesthesia actually lowers the anxiety in many patients and can actually increase the survival rate of these birds."
Common bacterial respiratory infections seen in pet birds today include Klebsiella, Proteus, chlamydophila, and Pasteurella.
"Bacterial infections can be very severe and serious," said Gregory Burkett, DVM, Dipl. ABVP, in Durham, N.C.
"Supportive care and appropriate antibiotics are treatments of choice for serious infections," Dr. Burkett said. "Antibiotics should be chosen based on culture and sensitivity. Supportive care includes heat, oxygen, rest, fluids and gavage feeding."
An increasing number of veterinarians are now using nebulization to deliver antibiotics and other medications directly into a bird's respiratory tract. "Drugs can be nebulized as well as saline to get deeper into the respiratory system," Burkett said.
"Antibiotics, along with other drugs such as steroids and antifungals, are frequently used with great success." Burkett said it is important to use a nebulizer that produces a three to five micron particles to improve penetration.
The fungal infection, aspergillosis, has been a huge problem for veterinarians for many years.
"It is one of the toughest avian diseases to diagnose and successfully treat," Vaughan said. "Since fungal organisms grow very slowly, usually by the time a bird has clinical symptoms, in most cases the disease is in an advanced stage, so you're working from a disadvantaged position."
An aspergillosis infection can go for months to years without detection, and suddenly a bird will present with dyspnea, tachypnea and open-mouthed breathing.
"In these cases usually a fungal plug will be found in the trachea at the bifurcation," Dr. Burkett said. "If found antemortem, treatment is difficult; attempting to remove the plug endoscopically can cause the plug to dislodge and enter the lungs, causing spread of the fungal organism."
In order to successfully treat aspergillosis, early diagnosis is essential, said avian researcher Robert Dahlhausen, DVM, M.S., owner of Veterinary Molecular Diagnostics in Milford, Ohio.
This past year he and his colleagues developed two PCR tests for aspergillosis: a general DNA probe that picks up any species in the aspergillus genus, and a second test that is specific for Aspergillus fumigatus—the species that accounts for the majority of Aspergillus infections in companion birds today.
So far, "It appears these new tests are a big improvement over the tests that were available in the past, in that they are much more reliable at confirming positive infections," Dr. Dahlhausen said. "With the assays that we've had available to date, you could have birds infected and still get negative test results for them off the assays, and it was a challenge to confirm the diagnosis."
Researchers have also been developing some new combination therapy protocols that have proved very successful in treating Aspergillus infections, Dahlhausen said. Traditionally, the drug of choice has been itraconazole, but many veterinarians are now using a combination of antifungals.
In addition to itraconazole, the drug arsenal may include amphoteracin, terbinifine (Lamisil), diflucane and glucanozole, according to Dahlhausen.
Often these drugs are administered by nebulization. Treatment may last anywhere from a few weeks to several months. "Exactly which drugs we use depends on the bird," Dahlhausen said. "African greys in particular tend to be very sensitive to itraconazole and can suffer from liver toxicity if they get too strong a dose."
Lately, he said, he has been relying more on Lamisil for treatment. "In some very deep-seeded Aspergillus infections, Lamisil is often effective when other, more standard therapies aren't," Dahlhausen said.
"Lamisil has a very good absorption when given orally and is very good at penetrating these granulomas. Also, it's a fungicidal medication, so it actually kills the fungal organism, whereas some of these other drugs might not."
In his practice, Dahlhausen uses itraconazole initially for five to six days along with Lamisil and then continues with just the Lamisil for the rest of the treatment period.
"Lamisil is a very safe drug, so it's great for long-term therapy," Dahlhausen said.
While aspergillosis is a very serious disease, "The success rate for treating aspergillosis is improving greatly," Dahlhausen said.
"In the past, aspergillosis was a death sentence, and the majority of birds wouldn't make it. But when I look back over the last several years in our practice, we were able to successfully treat the majority of birds that we saw with aspergillosis.
"The keys are early diagnosis and an effective long-term treatment in combination therapy."
Rebecca Sweat is a frequent contributor to Veterinary Practice News.
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