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The abdominal air sac actually forms a backwards C positioned dorsal and ventral to the caudal thoracic air sac (see Anatomy Overlay) discount 100 mg furosemide amex prehypertension at 20. In some species furosemide 40 mg with mastercard hypertension jnc, the right and left abdominal air sacs may be more symmetrical than shown buy furosemide overnight delivery blood pressure medication uk names. Entry sites are shown as either left-sided approaches (open circle) or right-sided approaches (solid circle) cheap 40mg furosemide fast delivery arrhythmia yahoo answers. Endoscopic laparotomy can be performed from either the right or left side of a bird, and 14 different approaches have been described. Site 4, located between the seventh and eighth ribs, is frequently used for endoscopic evalu- ation of the gonads; however, an entrance point through the left flank (site 6, Figures 13. The leg is pulled cranially and the entry site is at the junction of the caudal edge of the 1) eighth rib and the 2) flexor cruris medialis muscle. By matching the angle and depth of the endoscope, the endoscopist can develop an insight into the relative position of organs as viewed from entry site 6. Each color endoscopic picture has a corresponding angle and position marker to help the endoscopist envision the anatomic relationship of the endoscopic view. Thus, if the scope is oriented to B-4, the gonad, adrenal gland and kidney would be in view. Structures that will be used for orientation in the various endoscopic pictures include: a) lung b) ostium of the cranial thoracic air sac c) adrenal gland d) gonad e) kidney f) ureter, oviduct, vas deferens area g) abdominal air sac h) caudal thoracic air sac i) liver j) proventriculus k) heart and l) cranial thoracic air sac. In the clinician through the evaluation of this view, a clear, unobstructed view of the thoracoabdominal structures that can be ostium (o) of the caudal thoracic air sac viewed from various entrance points to the indicates that the tip of the endoscope is abdominal cavity. Also visible are the left adrenal entrance site is at the junction of the eighth gland (a), ilium (i), cranial pole of the left rib and the flexor cruris medialis muscle. Also visible are the left adrenal gland (a), right and left common iliac veins (arrows) Color 13. The air sac should be view of the kidney (k) and immature melan- transparent with minimal vascularity. The istic ovary (o) of a six-month-old Blue and proventriculus (p) is ventral to the en- Gold Macaw. The medial wall of the caudal tho- sels are seen through the abdominal air sac racic air sac (a) becomes contiguous with in the peritoneal membrane overlying the the lateral wall of the abdominal air sac. The mented, mature testicle (lt) in an Amazon cranial oviductal artery (arrow) is easily parrot. The vessels seen crossing the pole of the left kidney (k), epididymis (e), ovary are those that are present in the right testicle (rt), caudal vena cava (arrow) peritoneal membrane and are visible and right kidney (rk). Also visible are the left adrenal Also visible are the kidney (k), caudal pole gland (a), cranial pole of the left kidney (k), of the testicle (t) and a loop of intestines (i). The kidney (k) and aorta (a) are ovary (o), cranial pole of the left kidney (k), also visible. The vessels coursing across the ovi- duct, kidney and ovary are present in the erens (d) of a mature Amazon parrot. The ureter (u), kidney difficult to identify, but the dorsal ligament (k), and vessels in the abdominal air sac are of the oviduct (arrow) coursing across the also visible. The cranial pole of the abdominal (as opposed to the normal left left kidney (k), lung (lu), left common iliac abdominal) approach has been used to vein (open arrow) and aorta (a) are also demonstrate the regression of the right visible. Note the developing follicles (f) and the characteristic yellowish caudal vena cava (arrow), the cranial mes- enteric artery (open arrow) and the dorsal (“cooked egg”) appearance of the involuted ovary, indicating previous ovulation sites mesentery (dm). This endoscope is excellent for patients weighing less than 100 grams or in small anatomic sites (eg, sinus, trachea, ovi- duct). The major disadvantages of these very small endoscopes are their fragility, relatively small field of view and transmission of less light, which limit use- fulness in larger body cavities. For these reasons endoscopes with a 30° offset are recommended for general diagnostic The 2. Minimum Diagnostic Working Set for Examination and Biopsy Elements listed in “A” as well as: endoscope in the range of 170 to 190 mm is recom- Diagnostic sheath for 2. Shorter working lengths may give a more 5 Fr instrument channel 5 Fr double spoon flexible biospy forceps (oval jaws) comfortable feel in use but often lack the reach de- 5 Fr flexible grasping forceps sired for use in the trachea, esophagus or larger body cavities. Elements listed in“A” and “B” as well as: Diagnostic sheath incoporating a single 7 Fr instrument Angle of View: The final consideration when select- channel (for larger birds) 7 Fr double spoon flexible biopsy forceps (oval jaws) ing an endoscope for avian diagnostics is the angle of 5 Fr double spoon flexible biopsy forceps (round jaws) view of the distal lens element. A 0° lens offset affords 3 Fr flexible grasping forceps straight ahead viewing with a natural orientation. A 150 W Xenon high intensity light source Endovideo camera 30° offset angles the field of view obliquely in the direction of the offset (Figure 13. In the l980’s a tubular en- The major disadvantage of a small-sized, flexible doscope that attached to a handle-mount battery endoscope is that one cannot control the tip direction pack was introduced to the veterinary market as a unless the instrument is located in a confined area less-expensive alternative to rod-lens endoscopes. In an open area While this device had the advantages of lower cost, a (such as the air sac), the scope cannot be manipu- focusing ocular and a length similar to a rod-lens lated or used to penetrate beyond the air sac walls endoscope, it had the disadvantages of poorer resolu- without a probe. A specialty avian practice may have tion, reduced light transmission and a limited field of a small diameter flexible endoscope available to per- view. Large flexible scopes with up to five times greater than less expensive instru- an operating channel for placement of grasping and ments; however, the high optical quality, light trans- biopsy instrumentation can be used in ratites. Instrument Care Before purchasing any endoscopic system the veteri- narian is well advised to become familiar with the Flexible and rigid endoscopes are expensive, preci- optical qualities of all systems under consideration. Rigid tissues with accuracy and to recognize pathology or telescopes, especially those of small diameter, are it is of no value. High quality optical systems are fragile and must be carefully handled during trans- required to enable the clinician to achieve reliable, port and cleaning to avoid damage to the rod-lens reproducible results. Torsional stresses upon the long axis of the rigid endoscopes should have a working life of five to endoscope must be avoided. It is particularly important that justify the purchase of the appropriate equipment the operator be sensitive to the amount of force being should refer endoscopy services to more experienced applied to the telescope during a procedure. Over the past decade, rod-lens en- endoscopes should always be picked up by the ocular doscopes have become the standard for use in avian (eyepiece) rather than the distal tip. In many cases, simply washing the telescope in distilled water is all that is needed. A Conventional flexible endoscopes are based entirely quality lens paper is used to clean the lens surfaces. Unlike modern rigid endoscopes, which employ fore it is placed in a padded storage container that solid rod-lenses, flexible endoscopes use many coher- ent, flexible, glass fiber bundles to transmit the im- age. A l0 Moderate to marked obesity leading to the intra-abdominal mm flexible colonoscope was found to be effective in deposition of fat is the most frequent cause of difficulty in endoscopic visualization. Fine-diameter, flexible endoscopes techniques and careful movements of the endoscope will may have limited usefulness in smaller birds (eg, less reduce the risk of iatrogenic trauma. Ethylene oxide gas is an extremely effective ster- ilant, but exposed materials must be aerated for a minimum of eight to twelve hours before use. Ethyl- ene oxide is a human health hazard and must be used under carefully controlled conditions. The most practical and safe alternative for the avian practitioner for office or field sterilization of sensitive endoscopic equipment is soaking in a two percent solution of glutaraldehyde (of a type approved by the manufacturer of your equipment).
In a study of newly diagnosed type 1 diabetics furosemide 40 mg online heart attack 720p kickass, seven patients were given 3 g niacinamide per day and nine were given a placebo cheap furosemide 40mg overnight delivery pulse pressure endocarditis. After six months purchase 40mg furosemide with visa arteria vesicalis superior, ﬁve patients in the niacinamide group and two in the placebo group were still not taking insulin and had normal blood glucose and hemoglobin A1C discount 100mg furosemide mastercard blood pressure monitors at walmart. At 12 months, three patients in the niacinamide group but none in the placebo group were in clinical remission. As of 2004, there had been 12 studies of niacinamide treatment in patients with recent-onset type 1, or type 1 of less than ﬁve years’ duration, and who still had some functional beta cells. Of 10 double- blind, placebo-controlled studies, 5 showed a positive effect compared with a placebo in terms of prolonging the period in which insulin was not yet required, lower insulin requirements when the hormone was required, improved metabolic control, and increased beta cell function as determined by secretion of a substance known as C-peptide. In the 5 studies that showed a positive result, patients had a higher baseline fasting C-peptide level, and patients were generally older than in the negative studies. The ﬁrst of these studies, the Deutsche Nicotinamide Intervention Study, did not show much of an effect with 1. It is possible that such a formulation did not allow for sufﬁcient peak levels of niacinamide to block autoimmune mechanisms. Nonetheless, the fact that some patients have had a complete reversal of their disease makes its use certainly worth the effort, especially since there is currently no other reasonable alternative. The dosage recommendation is based on body weight: 25 to 50 mg niacinamide per kg of body weight, up to a maximum dosage of 3 g per day, in divided doses. However, because large doses of niacinamide could possibly harm the liver, a blood test for liver enzymes should be performed every three months to rule out liver damage. The line of research on its potential role in recent-onset type 1 diabetes began with examining the bark from the Malabar kino tree (Pterocarpus marsupium). This botanical medicine has a long history of use in India as a treatment for diabetes. Initially, epicatechin extracted from the bark was shown to prevent beta cell damage in rats. Further research indicated that both epicatechin and a crude alcohol extract of P. Another reason is that green tea polyphenols exhibit signiﬁcant antiviral activity against rotaviruses and enteroviruses, two types of virus suspected of being involved in the development of type 1. Recommended dosage for green tea extract in children younger than age 6 is 50 to 150 mg; for children 6 to 12 years old, it is 100 to 200 mg; for children over 12 and adults, it is 150 to 300 mg. The green tea extract should have a polyphenol content of at least 80% and be decaffeinated. Type 2 Diabetes Causes The major risk factor for type 2 diabetes is obesity or, more precisely, excess body fat. Approximately 80 to 90% of individuals with type 2 are obese (body mass index greater than 30). When fat cells (adipocytes), particularly those around the abdomen, become full of fat, they secrete a number of biological molecules (e. Also important is that as the number and size of adipocytes (fat cells) increase, this leads to a reduction in the secretion of compounds that promote insulin action, including adiponectin, a protein produced by fat cells. Not only is adiponectin associated with improved insulin sensitivity, but it also has anti-inﬂammatory activity, lowers triglycerides, and blocks the development of atherosclerosis (hardening of the arteries). The net effect of all of these actions is that fat cells severely stress blood glucose control mechanisms, as well as lead to the development of the major complication of diabetes, atherosclerosis. Because of all these newly discovered hormones secreted by adipocytes, many experts now consider adipose tissue to be part of the endocrine system, joining glands such as the pituitary, the adrenals, and the thyroid. As metabolic stress increases and insulin resistance becomes more signiﬁcant, eventually the pancreas cannot compensate and elevations in blood glucose levels develop. As the disease progresses from insulin resistance to full-blown diabetes, the pancreas starts to “burn out” and produces less insulin. Fortunately, the pancreas can recover and continue to secrete insulin for the rest of a person’s lifetime if ideal body weight is achieved and steps to improve insulin sensitivity are taken. Data from family studies also provide additional support: children who have one parent with type 2 have an increased risk of diabetes in their lifetime, and if both parents have the disease, the risk in offspring is nearly 40%. The Case of the Pima Indians The Pima Indians of Arizona have the highest rate of type 2 and obesity anywhere in the world. Research has demonstrated a strong genetic predisposition, but even with this strong tendency it is extremely clear that the high rate of type 2 in this group is almost totally due to diet and lifestyle. The Pima Indians living traditionally in Mexico still cultivate corn, beans, and potatoes as their main staples, plus a limited amount of seasonal vegetables and fruits such as zucchini, tomatoes, garlic, green peppers, peaches, and apples. The Pimas of Mexico also make heavy use of wild and medicinal plants in their diet. They work hard, have no electricity or running water in their homes, and walk long distances to bring in drinking water or to wash their clothes. They use no modern household devices; consequently, food preparation and household chores require extra effort by the women. In contrast, the Pima Indians of Arizona are largely sedentary and follow the dietary practices of typical Americans. Although roughly 16% of Native Americans in general in the United States have type 2, 50% of Arizona Pimas have type 2, and 95% of those diabetics are overweight or obese. By contrast, type 2 is a rarity among Mexican Pimas and only about 10% could be classiﬁed as obese. The average difference in body weight between the Arizona and Mexican Pima men and women is more than 60 lb. When patients are placed on a more traditional diet along with physical exercise, blood glucose levels improve dramatically and weight loss occurs. The focus right now by various medical organizations such as the National Institutes of Health is to educate children on the importance of exercise and dietary choices to reduce diabetes risk. Other Genetic and Racial Factors Racial and ethnic groups besides Pima Indians that have a higher tendency for type 2 include other Native Americans, African-Americans, Hispanic-Americans, Asian-Americans, Australian Aborigines, and Paciﬁc Islanders. In all of these higher-risk groups, again, it is important to point out that when they follow traditional dietary and lifestyle practices, the rate of diabetes is extremely low. It appears that these groups are simply sensitive to the Western diet and lifestyle. Of individuals with type 2, 69% did not exercise at all or did not engage in regular exercise; 62% ate fewer than ﬁve servings of fruits and vegetables per day; 65% obtained more than 30% of their daily calories from fat, with more than 10% of total calories from saturated fat; and 82% were either overweight or obese. By comparison, the 300 million typical Americans living alongside them have, over the past 250 years, willingly adopted advances of modern technology, making life less physically demanding. Although the typical Amish person’s diet is not very different from the average American’s and the rates of obesity are very similar as well, the rate of diabetes is about 50% lower. Although the percentage of Amish with impaired glucose tolerance (prediabetes) is about the same as the rate among other white populations in America, apparently not as many Amish go on to develop diabetes. This trend suggests that physical activity has a protective effect against type 2, independent of obesity. Lifestyle changes alone are associated with a 58% reduced risk of developing diabetes in people at high risk (those with impaired glucose tolerance), according to results from the Diabetes Prevention Program, a large intervention trial of more than 1,000 subjects. The two major goals of the program were achieving and maintaining a minimum of 7% weight loss and a minimum of 150 minutes per week of physical activity similar in intensity to brisk walking. In an effort to qualify carbohydrate sources as acceptable or not, two tools have been developed: the glycemic index and glycemic load.
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There is Schwann cell proliferation sis in fledgling mocking birds fed a commercial cat and swelling generic furosemide 40mg overnight delivery pulse pressure measurement, perivascular leukocytic infiltration and food has been reported cheap furosemide 40 mg without a prescription blood pressure medication for preeclampsia. All affected birds cord and degeneration at the neuromuscular end- responded to parenteral administration of selenium plate may also be observed effective 100mg furosemide heart attack 85 blockage. Other ministration of oral or parenteral riboflavin and diet species of birds being raised at this facility were not correction; however generic furosemide 40 mg fast delivery heart attack songs, many of the changes are irre- affected. Vitamin E deficiency also occurs in piscivorous birds Hypovitaminosis B6 (Pyridoxine) fed an unsupplemented diet of frozen fish (especially Neurologic signs associated hypovitaminosis B are6 smelt). In birds of the family Ardeidae (herons and characteristic, with the bird exhibiting a jerky, nerv- bitterns), the deficiency manifests initially as fat ous walk progressing to running and flapping the necrosis accompanied by steatitis. Muscular dystrophy may resolve with sup- Deficiency in a Nanday Conure was reported to cause subacute, multifocal white matter necrosis. Head the anterior muscles of the neck resulting in pseudo- trauma may occur at night when a panicked bird flies hypertonus of the muscles of the dorsal aspect of the into an enclosure wall or if birds fly into windows or neck (see Color 48). Injured birds may remain on the bottom of ciency causes a polyneuritis with myelin degenera- the enclosure and exhibit depression, head tilt, cir- tion of peripheral nerves. Blood may be present edema of the skin are also characteristic of thiamine in the mouth, ears or anterior or posterior chamber deficiency. Anisocoria and delayed pupillary light hours of oral or parenteral administration of vitamin response may be present and convulsions may occur B1. Administration of thiamine is a useful adjunct to therapy in many nonspecific neurologic Fractures of the skull or scleral ossicles may be de- disorders. In some cases, a bruise might be visualized on the head that is the result of meningeal hemorrhage seen through the cranium. A fibrocartilaginous, wedge-shaped hemorrhage to occur within the brain parenchyma. With intervertebral disc rupture, this meniscus is driven into the spinal canal along with Treatment is supportive and involves maintaining the fibrocartilaginous disc material (see Color 14). Dexamethasone appears to be the most im- In a Black Swan, cervical intervertebral degenera- portant therapeutic agent. The prognosis is guarded- tive joint disease and spondylosis caused spinal cord to-poor if the bird is convulsing. In mammals with spondylosis, ventral and lateral Compressive Lesions osteophyte formation result in osseous bridging be- Pigmented calvarium is characterized by a yellow tween adjacent vertebrae, while dorsal and dorsolat- discoloration (hemosiderin) in the skull, especially eral osteophyte formation, as occurred in this swan, the pneumatic spaces of the temporal bones. Inflammation of the birds, the joints between vertebral bodies are synovial frontal bone was reported as a cause of opisthotonos and in this swan, noninflammatory, degenerative and depression with violent convulsions. The stasis occurs secondary to thyroid enlargement and degeneration, rupture and atrophy of the synovial- results in increased intracranial pressure. Hydro- lined, fibrous intervertebral meniscus may have been cephalus and intracranial masses cause compressive involved in the pathogenesis of this disease. With hydrocepha- lus, the cortex over the lateral ventricles has a “blis- Dexamethasone and forced rest are the only recom- ter-like” appearance at necropsy. Naloxone and thyrotropin releas- ing hormone are beneficial in mammalian patients Spinal Abnormalities with spinal cord trauma, but their effects in avian Spinal fractures may be the result of injury or meta- patients are unknown. Tumors may affect the spinal cord by Peripheral Nervous System direct invasion or compression. The level of nerve injury (eg, neurapraxia, neurotmesis, The junction of the fixed synsacrum with the more axonotmesis or complete transection) determines the flexible portion of the thoracolumbar spine is a loca- prognosis. In many instances, nerve dysfunction is tion susceptible to mechanical stress and vertebral transient; however, as in the case of brachial plexus subluxation. King Penguin, spondylolisthesis was believed to be Clinically, there is evidence of denervation of the the result of trauma because no articular defects affected wing including lack of pain perception, pa- were observed. It may be difficult to determine the level of nerve injury in birds presented with clinical signs associated with a unilateral pe- ripheral neuropathy involving one extremity. Typi- cally, birds with neurapraxia improve clinically within two to four weeks, while those with axonot- mesis and neurotmesis (as with avulsion injury) would not. If these are not available, it is prudent to treat with supportive care for approximately one month, with weekly evalu- ation for signs of improved neurologic function. Abdominal Masses Compressive peripheral nerve trauma generally oc- curs secondary to an expanding mass that applies pressure to the nerve (see Figure 25. Because the pelvic nerves pass through the renal parenchyma, tumors or infection of the kidneys can damage the nerves (see Color 21). Ovarian tumors, if very large or invasive, have also been reported to damage these nerves. Renal adenocarcinomas occur more commonly in males than females and the incidence is higher in psittacine than passerine birds (see Color 25). The paresis may become bilateral, but systemic signs usually develop before the contralateral limb is affected. A severe wing droop was present and pearance of embryonal nephromas are similar to re- radiographs indicated a fractured coracoid. The wing was placed in a figure-of-eight bandage and the fracture healed without com- nal adenocarcinoma. When the bandage was removed, the bird still had a cysts and necrotic foci and are less frequently associ- severe wing droop, no deep pain and muscle atrophy involving most ated with paralysis. If these tumors cause in the avian iris, miosis is not a consistent feature of paralysis, the patient is likely to show an abdominal Horner’s syndrome. These tumors cause a peripheral Pituitary adenoma or pituitary chromophobe ade- neuropathy with a loss of withdrawal reflex not ob- noma occurs in young (four years old), predominantly served with a spinal cord lesion. These tumors arise from chromophobe cells Egg binding or internal trauma associated with and may or may not be functional, secreting tumors. These tumors are reported to cause a classic clinical Circulatory Disturbances syndrome described as somnolence with occasional Both peripheral and central neuropathies have been convulsions, uncoordinated wing-flapping and clonic as so c iat e d wi th dimin is he d c irculat ion. Incoordination, tremors ated with this condition, and affected birds are sim- and inability to perch have also been reported. In some cases, dipsia and polyuria, cere color change, feather abnor- however, neurologic signs may be observed. Exophthalmos, visual deficits, lack of pupillary scribed as a cause of ischemia and cerebral hyperten- light response and mydriasis may be present sion. Hepatic Encephalopathy Signs ranging from blindness and ataxia to opistho- Birds with severe liver disease may demonstrate tonos and seizures have been associated with cere- signs of hepatic encephalopathy. Hepatic lipidosis, br ov ascular accide nts an d is che mic in- 22,46,51,130 mycotoxicosis, hemochromatosis and vaccine-in- farction. Clinical signs vary with the clinical signs associated with hepatic encephalopa- location of the neoplasm. Vacuola- may be beneficial in diagnosing some cases; however, tion of the cells of the adrenal glands is a consistent a parallel test should be performed on an asympto- feature and may be an indication of stress.
Tylosin: The pharmacokinetics of intramuscularly Trimethoprim and sulfonamide combinations have administered tylosin has been studied in quail order furosemide online pills arteria lusoria, pi- few toxic effects buy generic furosemide pills blood pressure 300 150, but many birds (especially macaws) geons generic furosemide 40mg on line blood pressure cuff size, cranes and emus discount furosemide online american express arteria meningea media. Effective pulmonary concentrations were The injectable product may cause irritation and ne- achieved with nebulization of 1 gram tylosin in 50 ml crosis at the site of injection. Trimeth- Erythromycin: Erythromycin is active against cam- oprim/sulfadiazine (veterinary formulation) is avail- pylobacter and mycoplasma. Trimethoprim/sul- vestigated in pigeons,44 but it is rarely used in com- famethoxazole (human formulation) is available in panion and aviary birds. A water-soluble powder has been used to treat Trimethoprim/sulfadiazine is an excellent broad- mild respiratory infections in psittacine birds at a spectrum bacteriostatic drug. It is often the drug of rate of 500 mg/gallon of water but is of questionable choice when using the oral route to deliver antibiotics efficacy. A popular over-the-counter productb is avail- (eg, treating gram-negative infections in nestling able for medicating drinking water, but it is doubtful birds). Macrolides and Lincosamides Clindamycin: Clindamycin is the most active of the Pharmacology macrolides mentioned. It is used to treat anaerobic The macrolides and lincosamides interfere with bac- infections and osteomyelitis caused by susceptible terial protein synthesis, are bacteriostatic and share 6 gram-positive pathogens. Their spectrum of action in- osteomyelitis in a macaw with a combination of en- cludes gram-positive bacteria, pasteurella, borde- rofloxacin and clindamycin for seven months without tella, some mycoplasma and obligate anaerobic bac- detectable toxic effects. Injectable formulations are available but are seldom used in birds due to irritation and necrosis at New Macrolides: Research on treating Chlamydia the site of injection. Oral absorption is good in mam- trachomatis infection in humans has focused on the mals, but there are few pharmacokinetic studies in use of new macrolide (azalide) antibiotics (ie, azithro- birds. Studies usually limited to gastrointestinal irritation and in humans have demonstrated that a single dose of vomiting. For this reason, clients are instructed to handle this drug carefully and wear gloves when treating birds. Use in Companion Avian Medicine Oral Formulation (palmitate ester): This formula- tion is readily accepted by most birds but achieves erratic blood concentrations. Injectable Formulations (succinate, propylene gly- col-based): These formulations yield more predictable serum concentrations than the oral preparations. There is titis recur when therapy is stopped (photo courtesy of Louise wide pharmacokinetic variation among species. Comments Lincomycin: Lincomycin is usually combined with Use of chloramphenicol has been largely replaced by spectinomycin and has been used in finches to treat other antibiotics that are more effective and can be respiratory and alimentary tract infections caused by administered less frequently. Chloramphenicol is gram-positive bacteria and mycoplasma in other spe- still useful for treating infections caused by suscepti- cies. Chloramphenicol is bacteriostatic and is prob- Chloramphenicol ably not the drug of choice for initial treatment of Pharmacology severe, life-threatening infections. Chloramphenicol interferes with bacterial protein synthesis and is bacteriostatic. It will inhibit chlamydial growth and alleviate clinical signs in infected birds, but will not routinely clear a bird of infection. Oral Antifungal Therapy and parenteral formulations are available; however, oral absorption is highly erratic. Chloramphenicol is highly lipid-soluble and is widely distributed to most The most common fungal infections encountered in tissues, including the central nervous system. Tissue psittacine birds, raptors and waterfowl are candidi- concentrations often exceed serum levels. The route asis (usually confined to the alimentary tract) and of excretion varies with different species, but in most aspergillosis (respiratory and cutaneous). The major draw- Pharmacology back to the use of azoles is the lack of pharmacoki- Amphotericin B is a polyene antimicrobial drug that netic and toxicologic information to guide dosage disrupts the fungal cell membrane by substituting for ergosterol. However, empirical doses have been estab- lished, and use of these drugs is becoming estab- and fungi of medical importance. Comparison studies in humans tion, route of administration and potential toxicity have shown that amphotericin B is still one of the are important considerations when selecting an anti- most efficacious antifungal drugs, especially for fungal agent. Clinical data demonstrating im- proved efficacy when amphotericin B is combined Nystatin with flucytosine or an azole antifungal are conflict- Pharmacology ing, but combination therapy is a common practice for treating serious fungal infections in humans. Am- Nystatin is a polyene antimicrobial that disrupts the photericin B is not well absorbed after oral admini- fungal cell membrane by substituting for ergos- 48 stration and is too irritating for intramuscular or terol. It is effective against most strains of candida subcutaneous injection; thus, it must be delivered and some other yeasts, although clinical evidence intravenously or used topically. It is widely distrib- suggests resistant yeast strains may occur in some 46 uted to tissue and extracellular spaces where it is psittacine nurseries. Treatment failures may Use in Companion Avian Medicine occur if the nystatin is delivered via a tube or syringe Amphotericin B is one of the drugs of choice for to the back of the oral pharynx, bypassing more initially treating serious, systemic fungal infections. It has been used in com- bination with flucytosine in raptors and swans with Nystatin is a highly useful drug for yeast infections fair results. It has low may offer similar activity or may potentiate the ef- toxicity and is safe for use in nestling birds. With oral infections, nys- Amphotericin B can be nebulized or injected into an tatin or a more potent topical drug (eg, amphotericin affected air sac for respiratory infections. If be injected through the glottis or administered trans- resistance or a non-alimentary tract infection is en- tracheally to treat tracheal and syringeal aspergil- countered, a systemically active antifungal should be losis. Nystatin dosage recommendations have been empiri- The pharmacokinetics of amphotericin B in turkeys cally derived but are supported by effective, long- and selected raptors indicate that these birds elimi- term clinical use. Phar- formulas for prophylactic treatment in nurseries ex- macokinetic data in psittacine birds is lacking. If the yeast is term use in raptors was not associated with nephro- highly susceptible to nystatin, food-based admini- toxicity, so the drug may be safer in avian than stration will be effective. A major breakthrough in antifungal therapy oc- curred in 1979 with the release of the azole drug ketoconazole, the first orally active, systemic anti- Flucytosine fungal with a broad spectrum. Further research re- sulted in release of fluconazole in 1990 and itracona- Pharmacology zole in 1992. All three of these drugs are labeled for Flucytosine is converted by the liver to 5-fluorouracil, human use only. It is always used in combination with topical use only and are more toxic than more re- amphotericin B in humans, and this combination is cently available drugs. Resistance develops quickly when the The use of the azole antifungals in veterinary medi- drug is used alone. This drug is excreted almost plished by inhibition of a P450 enzyme system, and the entirely unmetabolized in the urine, and dosage relative potency of the azoles is determined by their modifications are necessary in patients with reduced affinity for this P450 enzyme moiety. Dose-related, reversible bone marrow have a P450 enzyme system, and the selective toxicity depression is the major toxic change seen in humans, of the azoles depends on their relative specificity for presumably due to the conversion of flucytosine into binding fungal P450 enzymes.