Introduction

Although there are many therapeutic agents available for treating companion birds, most drugs are based on empirical data, observations, and experience. There are relatively few pharmacodynamic studies in companion birds in relation to the medications we use or potentially use in practice.

Drug Administration

Most of the drugs given to companion birds are given parenterally or orally in the form of suspensions. There has been little research on the efficacy of various drug suspensions in these patients. It is essential for practitioners to have a good working relationship with a licensed compounding pharmacist. These pharmacists will ensure that the drug is placed in the appropriate media to remain viable in suspension and can warn of potential risks associated with this media.

Antibiotics

Bacterial diseases are among the most common medical problems reported in companion birds. Because there is a concern by the medical profession of antibiotic resistance associated with the overuse and abuse of antibiotics, it is important to recognize the factors that determine the use of antibiotic agents. Some of the decision making factors include effectiveness of the agent against the specific bacterial organism being treated, ease of administration, stress of the patient related to administration, ability of the agent to reach therapeutic levels at the intended site of treatment, cost, and availability of the drug.

When selecting an antibiotic the clinician should know if it is bacteriocidal or bacteriostatic, how it is administered, how well an oral medication is absorbed through the gastrointestinal tract and disseminated through the body, species variation relating to dose, and major side effects of the drug. Although there are other considerations, but if one does not apply this thought process into the selection of antibiotics and other therapeutic agents the success of treating avian patients will be greatly reduced. It is generally recommended to use bacteriocidal agents when possible, but certain diseases respond better to agents that may be bacteriostatic (e.g., drug of choice for Chlamydiophila psittaci is doxycycline). A detailed list of antibiotics, dosages, and special considerations are listed in the Exotic Animal Formulary (2005).¹

It is important to obtain a definitive diagnosis whenever possible to avoid the problems associated with the empirical dosages and to improve efficacy in these species. Antibiotics should be selected based on culture and sensitivity results when possible. The use of more pathogen-specific antimicrobials will decrease the potential for resistant bacteria and often narrows the potential side effects. Following are some of the antibiotics commonly used in companion bird medicine¹:

 Antimicrobial agents commonly used to treat bacteremia/septicemia cases include synergistic aminoglycoside and cephalosporin therapy, enrofloxacin with extended-spectrum penicillins, and for anaerobic infections chloramphenicol, clindamycin, and metronidazole.

 Cephalosporins, doxycycline, trimethoprim-sulfa, and fluoroquinolones are often used to treat anaerobic soft tissue infections while clindamycins or metronidazoles are used to treat anaerobic soft tissue infections.

 Respiratory tract infections are one of the most common disease presentations involving avian species. The drugs of choice for respiratory infections are extended-spectrum penicillins, cephalosporins, tetracyclines (especially doxycycline), trimethoprim-sulfa, chloramphenicol, fluoroquinolones, macrolides, and, for anaerobic infections, clindamycin or metronidazole. Antibiotics can be administered through nebulization techniques and nasal flushes.

 Trimethoprim-sulfa, fluoroquinolones, cephalosporins, amoxicillin, tetracyclines, and metronidazole for anaerobic infections are commonly used for conditions that affect the gastrointestinal tract.

 Dermatological presentations are treated with similar antimicrobial agents that one would use for other small companion animals: amoxicillin-clavulanate, cephalosporins, erythromycin, enrofloxacin, and trimethoprim-sulfa.

 Bone and/or joint infections are difficult to treat and as with any microbial infection a culture and sensitivity will greatly aid in selecting the right antibiotic agent to use. Choices of antimicrobial agents to use for bone and/or joint infections include cephalosporins, extended-spectrum penicillins, fluoroquinolones, aminoglycosides, clindamycin, and, for anaerobic infections, extended-spectrum penicillins with clindamycin and third generation cephalosporins with clindamycin. Polymethyl methacrylate (PMMA) beads containing aminoglycosides, fluoroquinolones, or clindamycin may be a useful adjunct to conventional antibiotic therapy.

 Extended-spectrum penicillins (piperacillin), cephalosporins (ceftazidime, ceftiofur), trimethoprim-sulfa, and fluoroquinolones, are all commonly used for urinary tract infections.

 For central nervous system infections it is important to choose an agent that crosses the blood-brain barrier. The drugs of choice are chloramphenicol and fluoroquinolones.

 Reproductive tract disorders are best treated with chloramphenicol, trimethoprim-sulfa, enrofloxacin, amoxicillin-clavulanate, and clindamycin (against anaerobes).

Antifungal Agents

Fungal diseases (aspergillosis, candidiasis, and avian gastric yeast [Macrorhabdus ornithogaster]) are relatively common in captive birds. Of these diseases, aspergillosis is the most challenging to diagnose and treat. Although several species of Aspergillus may be involved in avian disease, the most commonly encountered is A. fumigatus, followed by A. flavus and A. niger. Particularly susceptible species include African grey, Amazon, and pionus parrots.

Agents most commonly used in treating mycotic diseases in birds include:

 Amphotericin B: for aspergillosis, may be used intravenously or topically via nebulization, intratracheal, and direct application to lesions within the air sac; administered PO for avian gastric yeast; renal toxicity does not seem to be a significant problem in birds.

 Nystatin: fungistatic; used to treat yeast infections, primarily candidiasis; functions as a topical treatment when administered PO (drug requires contact with the yeast to be effective).

 Itraconazole: most common triazole antifungal used in birds; fungistatic; alters the cellular membranes of susceptible fungi, thereby increasing and allowing leakage of cellular contents and impaired uptake of purine and pyrimidine precursors.

 Voriconazole: a triazole antifungal; oral; in people with aspergillosis, treatment success with voriconazole is often better than amphotericin or itraconazole; some side effects in people have been reported.

 Other triazoles: fluconazole (PO), ketoconazole (PO), clotrimazole (nebulization), and miconazole and enilconazole (topical).

 Terbinafine: fungicidal; an allylamine antifungal that inhibits squalene epioxidase, thus inhibiting fungal steroid and cell wall synthesis; well-tolerated; administered orally or nebulized.

Respiratory tract infections in birds caused by Aspergillus are especially difficult to treat. The most commonly used drugs used to treat this disease are a combination of itraconazole with nebulization of amphotericin B. Topical application of amphotericin B or clotrimazole aids in the initial treatment success. Long periods of oral antifungal drug therapy are usually required to treat aspergillosis. Although itraconazole can be effective, treatment failures in some species (i.e., African grey parrots) are common. In those cases, terbinafine or voriconazole may be used.

Analgesics

Because avian pain is likely analogous to pain experienced by most mammals, painful procedures or events should always be accompanied by appropriate analgesia. As in mammals, it is assumed that pre-emptive administration of analgesics reduces the magnitude of the pain experienced by a bird as a result of tissue damage. During gas anesthesia, the CNS is depressed sufficiently to prevent perception of pain, but this depression does not provide analgesia. In fact, inhaled anesthetics can produce extreme sensitivity to pain at very low concentrations. The sometimes violent recoveries in birds from anesthetic may be due, in part, to hyperalgesia produced by low concentrations of inhaled anesthetics. Opioids and nonsteroidal anti-inflammatory drugs (NSAIDS) are probably the most frequently used drugs for treating pain in birds.

Opioids: Opioid actions are mediated by specific membrane receptors (mu, delta, and kappa) that are distributed throughout the CNS and peripheral nervous system. In contrast to the population of opioid receptors in the mammalian nervous system, kappa receptors predominate in the pigeon fore brain. Buprenorphine is a partial agonist that binds readily to mu receptors and has some kappa antagonist properties. Although reported to be clinically effective in birds, buprenorphine at 0.1 mg/kg in African grey parrots did not show an analgesic effect (higher doses may be effective in some species).

Butorphanol is a mixed agonist-antagonist with primarily kappa agonist action. Butorphanol (1-3 mg/kg IM) is the correct recommendation for opioid analgesia in parrots.

Non-steroidal Anti-inflammatory Drugs: NSAIDs control pain by inhibiting cyclooxygenase (COX) enzymes which prevents production of prostaglandins (important local mediators of inflammation that lower the threshold of thermal, mechanical, and chemical nociceptors). However, NSAIDs are also capable of producing gastrointestinal ulceration and bleeding because of inhibition of prostaglandin synthesis. NSAIDs should not be used if there is an indication of renal impairment, hepatic dysfunction, severe hypovolemia, or if gastric ulceration is present.

NSAIDs can be use to relieve musculoskeletal and visceral pain, acute pain (trauma or surgical), and chronic pain such as osteoarthritis. Although the most common NSAIDs used in avian medicine are ketoprofen, carprofen, and meloxicam, the latter two are preferred because of their widespread use and low incidence of reported toxicities.

Corticosteroids

Steroid use can cause severe alterations in the normal physiology of birds. For example, studies in pigeons have shown the deleterious affects of steroids on the liver of birds and the possible negative affect on breeding birds. Corticosteroids in psittacine birds can also cause other adverse effects, including immunosuppression, delayed wound healing, hepatic disease, and gastrointestinal ulceration. Since the use of steroids in many situations is now controversial, it may be appropriate to avoid these drugs unless no other medication will be effective.

References

1.  Carpenter JW (ed.). Exotic Animal Formulary. 3rd ed. St. Louis, Elsevier Publishers, 2005. pp 133-344; 547-554.

2.  Flammer K. Common bacterial infections and antibiotic use in companion birds. Suppl Compend Contin Educ Pract Vet. 20(3A): 34-48, 1998.

3.  Lumeij JT. Psittacine antimicrobial therapy. Antimicrobial Therapy in Caged Birds and Exotic Pets: International Symposium, Orlando, 1995. pp. 38-47

4.  Machin KL. Avian analgesia. Semin Avian Exotic Pet Med. 14(4): 236-242, 2005.

5.  Rosenthal KL. Therapeutic contraindications in exotic pets. Semin Avian Exotic Pet Med. 13(1): 44-48, 2004.