Can the intake of antiparasitic secondary metabolites explain the low prevalence of hemoparasites among wild Psittaciformes?

BACKGROUND: Parasites can exert selection pressure on their hosts through effects on survival, on reproductive success, on sexually selected ornament, with important ecological and evolutionary consequences, such as changes in population viability. Consequently, hemoparasites have become the focus of recent avian studies. Infection varies significantly among taxa. Various factors might explain the differences in infection among taxa, including habitat, climate, host density, the presence of vectors, life history and immune defence. Feeding behaviour can also be relevant both through increased exposure to vectors and consumption of secondary metabolites with preventative or therapeutic effects that can reduce parasite load. However, the latter has been little investigated. Psittaciformes (parrots and cockatoos) are a good model to investigate these topics, as they are known to use biological control against ectoparasites and to feed on toxic food. We investigated the presence of avian malaria parasites (Plasmodium), intracellular haemosporidians (Haemoproteus, Leucocytozoon), unicellular flagellate protozoans (Trypanosoma) and microfilariae in 19 Psittaciformes species from a range of habitats in the Indo-Malayan, Australasian and Neotropical regions. We gathered additional data on hemoparasites in wild Psittaciformes from the literature. We considered factors that may control the presence of hemoparasites in the Psittaciformes, compiling information on diet, habitat, and climate. Furthermore, we investigated the role of diet in providing antiparasitic secondary metabolites that could be used as self-medication to reduce parasite load. RESULTS: We found hemoparasites in only two of 19 species sampled. Among them, all species that consume at least one food item known for its secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, were free from hemoparasites. In contrast, the infected parrots do not consume food items with antimalarial or even general antiparasitic properties. We found that the two infected species in this study consumed omnivorous diets. When we combined our data with data from studies previously investigating blood parasites in wild parrots, the positive relationship between omnivorous diets and hemoparasite infestation was confirmed. Individuals from open habitats were less infected than those from forests. CONCLUSIONS: The consumption of food items known for their secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, as well as the higher proportion of infected species among omnivorous parrots, could explain the low prevalence of hemoparasites reported in many vertebrates.

Feather mites (Acari: Astigmata) of captive Psittaciformes in Brazil / Ácaros de pena (Acari: Astigmata) de Psittaciformes de cativeiro do Brasil

Feather samples were obtained from the following Psittaciformes birds: Amazona amazonica, Amazona aestiva, Aratinga jandaya, Brotogeris spp., Ara ararauna and Ara chloropterus (total of 37 individuals). These birds were housed at the Wild Animal Screening Center of Maranhão, São Luís, Brazil. Four feathers were taken from the following regions: head, back, wings, belly/breast, thighs, and tail/covert. Mites were found on 17 birds (45.94%). Astigmatid mites belonging to the genera Fainalges (Xolalgidae), Chiasmalges (Psoroptoididae) and Tanyaralichus (Pterolichidae) were identified. The highest dominance coefficient was for the mite Fainalges sp. (DC= 96.29). Chiasmalges sp. was obtained only from Ara chloropterus, and Tanyaralichus was found in A. aestiva. The genus Fainalges was obtained from all the species of Psittaciformes studied, except for A. ararauna. In evaluating mite density according to body region, statistical differences were found between the back and wing regions (P= 0.041), back and thighs (P= 0.02), wings and tail (P= 0.002), belly and tail (P= 0.031) and thighs and tail (P= 0.001). The morphological variations observed in Fainalges spp. suggested the existence of three species that probably have not been described yet. This was the first record of the genus Tanyaralichus in Brazil.(AU)

As amostras de penas foram obtidas das seguintes aves da ordem Psittaciformes: Amazona amazonica, Amazona aestiva, Aratinga jandaya, Brotogeris spp., Ara ararauna e Ara chloropterus, totalizando 37 aves, alojadas no Centro de Triagem de Animais Silvestres do Maranhão, São Luís, Brasil. Colheram-se quatro penas de cada uma das regiões: cabeça, dorso, asas, ventre/peito, coxas e cauda/crisso. Verificou-se a presença de ácaros em 17 aves (45,94%). Foram identificados ácaros Astigmata, pertencentes aos gêneros Fainalges (Xolalgidae), Chiasmalges (Psoroptoididae) e Tanyaralichus (Pterolichidae), sendo o maior coeficiente de dominância correspondente ao ácaro Fainalges sp. (CD= 96,29). Chiasmalges sp. foi obtido apenas de Ara chloropterus, e Tanyaralichus foi encontrado em A. amazônica. O gênero Fainalges foi obtido de todas as espécies de Psittaciformes estudadas, exceto em A. ararauna. Na avaliação da densidade de ácaros por região do corpo, verificou-se diferença estatística entre regiões dorsal e asas (P= 0,041), dorsal e coxas (P= 0,02), asas e caudal (P=0,002), ventral e caudal (P= 0,031) e coxas e caudal (P= 0,001). Variações morfológicas observadas em Fainalges spp., sugerem a existência de três espécies provavelmente ainda não descritas. Este é o primeiro registro do gênero Tanyaralichus no Brasil.(AU)

Antibody selection for immunocytochemical characterization of the male reproductive system in Psittaciformes.

The success of breeding programs is limited by the sparse knowledge about endocrine regulation and biochemical reactions in the psittacine male tract. The immunocytochemical analysis of parrots' testicular tissues provides an insight into their reproductive system but is often hampered by the lack of reliable antibodies. In the present study, we tested a large panel of antibodies raised against steroid receptors, steroidogenic enzymes, relaxin peptides including their receptors, and proliferation markers on paraffin sections of testicular tissue from eight psittacine genera representing three continents. All investigated species displayed the tested markers in somatic and germ cells of testis and epididymis, even though cell distribution was partly heterogenous and in species-specific patterns. The 17ß-hydroxysteroid-dehydrogenase-2, 3ß-hydroxysteroid-dehydrogenase, and smooth muscle actin allowed the cross-species differentiation between active and nonactive gonads. The remaining steroidogenic enzymes, steroid receptors, relaxin peptides, and Ki67 proved to be suitable to define reproductive activity depending on the parrot species. Adapting immunocytochemical methods to different psittacines was successful, though various cellular expression patterns do not allow the transfer of results among different parrot species. However, the availability of a reliable repertory of sexual markers is important to examine reproductive biology of psittacine birds.

Predicted metabolizable energy density and amino acid profile of the crop contents of free-living scarlet macaw chicks (Ara macao).

Hand rearing of neonates is a common practice for the propagation of psittacines. However, nutritional requirements for their growth and development are not well understood, and malnutrition is common. We analysed the amino acid (AA) profile of the crop contents of 19 free-living scarlet macaw (Ara macao) chicks, 19-59 days old. Predicted metabolizable energy (PME) density was 16.9 MJ/kg DM and true protein (total AA protein) 8.3 g/MJ PME. Crude protein (CP) was 10.0 g/MJ PME, lower than the requirements of 0- to 12-week-old leghorn chicks but not different than the requirements of growing budgerigars (Melopsittacus undulatus) and lovebirds (Agapornis spp.). The mean concentrations of leucine, isoleucine, threonine, lysine (Lys) and methionine on a PME basis were below the minimum requirements of 0- to 12-week-old leghorn-type chicks. The calculated PME density of the samples did not vary with age. However, there was a significant negative correlation between the average age of the chicks and the Lys concentration. We conclude that the lower CP and AA densities compared with poultry could result from a combination of (i) differences in the essential AA composition of the body tissues, (ii) adaptations that allow the birds to grow on low-protein food sources and (iii) suboptimal nutrition of these free-ranging chicks.

[Endocrinologic studies of male psittacine birds for the evaluation of their reproductive status]. / Endokrinologische Untersuchung männlicher Papageienvögel zur Beurteilung ihres Reproduktionsstatus.

OBJECTIVE: Evaluating methods of hormone measurement in different specimens of male parrots in order to assess their reproductive status and stress axis. MATERIAL AND METHODS: Cockatiels and rose-ringed parakeets were chosen as psittaciforme representatives and their endocrine profiles were examined. In various pre-experiments, suitable techniques for the determination of testosterone in plasma, saliva and faeces of male parrots were established. Before analysing the samples by enzyme immunoassay, blood and faeces were extracted using diethyl ether, while saliva could be tested without extraction. Based on the excretion of mainly conjugated testosterone metabolites, parrots' faecal samples were also hydrolysed with ß-glucuronidase/arylsulfatase before extraction. In addition, the levels of the stress hormone corticosterone were determined by radioimmunoassay in order to assess possible relationships between stress and the secretion of testosterone. RESULTS: The examined psittacine species displayed different seasonal secretion patterns for both testosterone and corticosterone. Cockatiels had maximum plasma testosterone levels in February, in contrast, rose-ringed parakeets showed highest concentrations in November. As a consequence of cumulative excretion, both species showed much higher faecal than plasma testosterone concentrations. In rose-ringed parakeets, the levels of corticosterone in plasma were exceptionally high compared to the cockatiels. CONCLUSION: According to this study, we have been able to establish suitable methods for testosterone analysis in blood and faeces of cockatiels and rose-ringed parakeets, supporting the assessment of their reproductive status. At present saliva does not appear to be an ideal medium for reliable hormone level measurement, thus further investigations are required concerning this subject. CLINICAL RELEVANCE: By means of process analysis, it will be possible to detect increasing testosterone levels and/or pathological alterations, which could be considered in breeding programmes.

Pathology of aging psittacines.

Aging processes leading to specific organ problems are not obvious in aging psittacines. In general, birds live long and age slowly despite their high metabolic rates and very high total lifetime energy expenditures. Most pathologic processes seen in older parrots are generally not specific for aging because they are seen in young birds as well. Pathologic processes that have a tendency to occur more in older psittacines are atherosclerosis and repeated injury processes, such as chronic pulmonary interstitial fibrosis, pneumoconiosis, liver fibrosis, and lens cataracts. Also, some neoplasms are more often seen at an older age.

Mechanism and rate of glucose absorption differ between an Australian honeyeater (Meliphagidae) and a lorikeet (Loriidae).

Efficient mechanisms of glucose absorption are necessary for volant animals as a means of reducing mass during flight: they speed up gut transit time and require smaller volume and mass of gut tissue. One mechanism that may be important is absorption via paracellular (non-mediated) pathways. This may be particularly true for nectarivorous species which encounter large quantities of sugar in their natural diet. We investigated the extent of mediated and non-mediated glucose absorption in red wattlebirds Anthochaera carunculata (Meliphagidae) and rainbow lorikeets Trichoglossus haematodus (Loriidae) to test the hypothesis that paracellular uptake accounts for a significant proportion of total glucose uptake in these species. We found that routes of glucose absorption are highly dynamic in both species. In lorikeets, absorption of L-glucose (non-mediated uptake) is slower than that of D-glucose (mediated and non-mediated uptake), with as little as 10% of total glucose absorbed by the paracellular pathway initially (contrasting previous indirect estimates of approximately 80%). Over time, however, more glucose may be absorbed via the paracellular route. Glucose absorption by both mediated and non-mediated mechanisms in wattlebirds occurred at a faster rate than in lorikeets, and wattlebirds also rely substantially on paracellular uptake. In wattlebirds, we recorded higher bioavailability of L-glucose (96+/-3%) compared with D-glucose (57+/-2%), suggesting problems with the in vivo use of radiolabeled d-glucose. Further trials with 3-O-methyl-D-glucose revealed high bioavailability in wattlebirds (90+/-5%). This non-metabolisable glucose analogue remains the probe of choice for measuring uptake rates in vivo, especially in birds in which absorption and metabolism occur extremely rapidly.

Pharmacokinetics of voriconazole after oral administration of single and multiple doses in African grey parrots (Psittacus erithacus timneh).

OBJECTIVE: To determine the pharmacokinetics and safety of orally administered voriconazole in African grey parrots. ANIMALS: 20 clinically normal Timneh African grey parrots (Psittacus erithacus timneh). PROCEDURES: In single-dose trials, 12 parrots were each administered 6, 12, and 18 mg of voriconazole/kg orally and plasma concentrations of voriconazole were determined via high-pressure liquid chromatography. In a multiple-dose trial, voriconazole (18 mg/kg) was administered orally to 6 birds every 12 hours for 9 days; a control group (2 birds) received tap water. Treatment effects were assessed via observation, clinicopathologic analyses (3 assessments), and measurement of trough plasma voriconazole concentrations (2 assessments). RESULTS: Voriconazole's elimination half-life was short (1.1 to 1.6 hours). Higher doses resulted in disproportional increases in the maximum plasma voriconazole concentration and area under the curve. Trough plasma voriconazole concentrations achieved in the multiple-dose trial were lower than those achieved after administration of single doses. Polyuria (the only adverse treatment effect) developed in treated and control birds but was more severe in the treatment group. CONCLUSIONS AND CLINICAL RELEVANCE: In African grey parrots, voriconazole has dose-dependent pharmacokinetics and may induce its own metabolism. Oral administration of 12 to 18 mg of voriconazole/kg twice daily is a rational starting dose for treatment of African grey parrots infected with Aspergillus or other fungal organisms that have a minimal inhibitory concentration for voriconazole < or = 0.4 microg/mL. Higher doses may be needed to maintain plasma voriconazole concentrations during long-term treatment. Safety and efficacy of various voriconazole treatment regimens in this species require investigation.

Assessment of a point-of-care biochemical analyzer and comparison with a commercial laboratory for the measurement of total protein and albumin concentrations in psittacines.

OBJECTIVE: To determine agreement for total protein (TP) and albumin concentrations measured by a point-of-care biochemical analyzer in heparinized whole blood and plasma samples obtained from psittacines and compare results with those from a commercial laboratory. SAMPLE POPULATION: Hematologic samples from 92 healthy birds. PROCEDURES: Duplicate samples of heparinized whole blood and plasma were obtained. A point-of-care biochemical analyzer was used to determine TP and albumin concentrations. To assess precision, intraclass correlation coefficient (r(i)) and Bland-Altman measures of agreement were used. These results were compared by use of Bland-Altman plots with those obtained from a commercial laboratory that used a biuret method for TP concentration and electrophoresis for albumin concentration. RESULTS: For the analyzer, there was excellent agreement (r(i) = 0.91) between heparinized whole blood and plasma samples for TP and albumin concentrations. Relative error was 0.9% for TP and 0.7% for albumin. Analyzer results correlated well with commercial laboratory results, with a downward bias of 0.6 for TP and 0.3 for albumin. CONCLUSIONS AND CLINICAL RELEVANCE: The analyzer had excellent precision for analysis of heparinized whole blood or plasma samples for TP or albumin concentrations; analyzer values had good agreement with those from a commercial laboratory. The analyzer could be a valid method to measure plasma TP concentrations and provide point-of-care testing in apparently healthy parrots. Biochemical analyzer results for plasma albumin concentration were not validated by results from a commercial laboratory, so conclusions cannot be drawn regarding use of the analyzer in measurement of albumin concentrations in psittacines.

Pharmacokinetics of marbofloxacin in blue and gold macaws (Ara ararauna).

OBJECTIVE: To determine the pharmacokinetics of marbofloxacin after single IV and orally administered doses in blue and gold macaws. ANIMALS: 10 healthy blue and gold macaws. PROCEDURES: In a crossover study, marbofloxacin (2.5 mg/kg) was administered orally (via crop gavage) to 5 birds and IV to 5 birds. Blood samples were obtained at 0, 0.5, 1, 3, 6, 12, 24, 48, 72, and 96 hours after marbofloxacin administration. After a 4-week washout period, the study was repeated, with the first 5 birds receiving the dose IV and the second 5 birds receiving the dose orally. Serum marbofloxacin concentrations were quantitated by use of a validated liquid chromatography-mass spectrometry assay. RESULTS: After oral administration, mean +/- SD area under the curve was 7.94 +/- 2.08 microg.h/mL, maximum plasma concentration was 1.08 +/- 0.316 microg/mL, and bioavailability was 90.0 +/- 31%. After IV administration of marbofloxacin, the apparent volume of distribution was 1.3 +/- 0.32 L/kg, plasma clearance was 0.29 +/- 0.078 L/h/kg, area under the curve was 9.41 +/- 2.84 microg.h/mL, and the harmonic mean terminal half-life was 4.3 hours. CONCLUSIONS AND CLINICAL RELEVANCE: Single IV and orally administered doses of marbofloxacin were well tolerated by blue and gold macaws. The orally administered dose was well absorbed. Administration of marbofloxacin at a dosage of 2.5 mg/kg, PO, every 24 hours may be appropriate to control bacterial infections susceptible to marbofloxacin in this species.

Distribution of unique red feather pigments in parrots.

In many birds, red, orange and yellow feathers are coloured by carotenoid pigments, but parrots are an exception. For over a century, biochemists have known that parrots use an unusual set of pigments to produce their rainbow of plumage colours, but their biochemical identity has remained elusive until recently. Here, we use high-performance liquid chromatography to survey the pigments present in the red feathers of 44 species of parrots representing each of the three psittaciform families. We found that all species used the same suite of five polyenal lipochromes (or psittacofulvins) to colour their plumage red, indicating that this unique system of pigmentation is remarkably conserved evolutionarily in parrots. Species with redder feathers had higher concentrations of psittacofulvins in their plumage, but neither feather colouration nor historical relatedness predicted the ratios in which the different pigments appeared. These polyenes were absent from blood at the time when birds were replacing their colourful feathers, suggesting that parrots do not acquire red plumage pigments from the diet, but instead manufacture them endogenously at growing feathers.

Carboplatin pharmacokinetics following a single-dose infusion in sulphur-crested cockatoos (Cacatua galerita).

OBJECTIVE: To determine the pharmacokinetics of carboplatin in sulphur-crested cockatoos, so that its use in clinical studies in birds can be considered. DESIGN: A pharmacokinetic study of carboplatin, following a single intravenous (IV) or intraosseus (IO) infusion over 3 min, was performed in six healthy sulphur-crested cockatoos (Cacatua galerita). PROCEDURE: Birds were anaesthetised and a jugular vein cannulated for blood collection. Carboplatin (5 mg/kg) was infused over 3 min by the IV route in four birds via the contralateral jugular vein, and by the IO route in two birds via the ulna. Serial blood samples were collected for 96 h after initiation of the infusion. Tissue samples from 11 organs were obtained at necropsy, 96 h after carboplatin administration. Total Pt and filterable Pt in plasma and tissue Pt concentrations were assayed by inductively coupled plasma-mass spectrometry. A noncompartmental pharmacokinetic analysis was performed on the plasma data. RESULTS: The mean +/- SD for the Cmax of filterable Pt was 27.3 +/- 4.06 mg/L and in all six birds occurred at the end of the 3 min infusion, thenceforth declining exponentially over the next 6 h to an average concentration of 0.128 +/- 0.065 mg/L. The terminal half-life (T1/2) was 1.0 +/- 0.17 h, the systemic clearance (CI) was 5.50 +/- 1.06 mL/min/kg and the volume of distribution (Vss) was 0.378 +/- 0.073 L/kg. The extrapolated area under the curve (AUC0-x) was 0.903 +/- 0.127 mg/mL x min; the area extrapolated past the last (6 h) data point to infinite time averaged only 1.25% of the total AUC0-x. The kidneys had the greatest accumulation of Pt (7.04 +/- 3.006 microg/g), followed by the liver (3.08 +/- 1.785 microg/g DM). CONCLUSIONS AND CLINICAL RELEVANCE: Carboplatin infusion in sulphur-crested cockatoos produced mild, transient alimentary tract signs and the Pt plasma concentration was similar whether carboplatin was given intravenously or intraosseously. Filterable plasma Pt concentrations for carboplatin persisted longer than for cisplatin, due mostly to the difference in systemic clearance between these drugs in sulphur-crested cockatoos. The distribution of tissue Pt after carboplatin administration was similar to that reported for cisplatin in sulphur-crested cockatoos. Despite anatomical, physiological and biochemical differences among animal species, the pharmacokinetic disposition of filterable Pt in the sulphur-crested cockatoo shares some features with the kinetics reported previously in other animals and human beings.

Adult cockatiels (Nymphicus hollandicus) metabolically adapt to high protein diets.

To determine the ability of cockatiels (Nymphicus hollandicus), a granivorous avian species, to adapt metabolically to high dietary protein levels, adult males (n = 26) were fed isocaloric diets containing 11, 20, 35 or 70% crude protein (CP) for 11 mo. Throughout the trial, body weight and breast muscle weight were maintained by 11, 20 or 70% CP. The 35% CP diet resulted in significantly greater body weight (P < 0.05) and whole-body lipid content (P < 0.05) compared with the 11% CP diet. The 20% CP diet resulted in greater breast muscle mass compared with 70% CP (P < 0.05). Activity of the amino acid catabolic enzymes alanine aminotransferase, aspartate aminotransferase and arginase as well as the gluconeogenic enzyme phosphoenolpyruvate carboxykinase were significantly increased with 70% CP (P < 0.05). Serum essential amino acids, urea and uric acid were also increased with 70% CP (P < 0.05), but the magnitude of their increase was similar to that found in omnivorous chickens fed a similar diet. There was no evidence of visceral gout, articular gout or renal pathology; however liver lesion severity, and specifically liver lipogranuloma severity, was significantly increased above 11% CP (P < 0.05). We conclude that cockatiels are able to up-regulate enzymes for amino acid catabolism as well as mechanisms for nitrogen excretion in response to high dietary protein levels, and that high dietary protein levels are not associated with kidney dysfunction in this avian species.

Platinum pharmacokinetics in sulphur-crested cockatoos (Cacatua galerita) following single-dose cisplatin infusion.

OBJECTIVE: To determine the pharmacokinetics of platinum (Pt) in cockatoos. DESIGN: A pharmacokinetic study of Pt, following a single i.v. infusion of cisplatin, was done in six healthy sulphur-crested cockatoos (Cacatua galerita). PROCEDURE: Birds were hydrated for 1 h before and 2 h after a 1-h cisplatin infusion (1 mg/kg, i.v.). Serial blood samples were collected for 96 h after initiation of the infusion and urine was collected for 2 h during the hydration period after cisplatin administration. Tissue samples from 10 organs were obtained at necropsy, 96 h after cisplatin infusion. Total Pt and filterable Pt in plasma, urinary Pt and tissue Pt concentrations were assayed by inductively coupled plasma-mass spectrometry. A noncompartmental pharmacokinetic analysis was performed on the plasma and urine data. RESULTS: For total Pt and filterable Pt, the respective mean systemic clearances were 0.373 and 0.699 L/kg hourly, the steady state volumes of distribution were 4.19 and 0.356 L/kg, and the mean residence times were 111 and 0.512 h. Total plasma Pt displayed a bi-exponential decay profile with average half-lives of 0.398 and 79.0 h, while filterable Pt had a monoexponential decay with mean half-life of 0.413 h. The renal clearance during the 2-h postinfusion period was 0.167 L/kg hourly. The kidneys had the highest Pt accumulation (4.54 micrograms/g DM). CONCLUSIONS AND CLINICAL RELEVANCE: Cisplatin infusion in cockatoos was well tolerated and Pt plasma concentrations were similar to those measured during treatment of solid tumours in human patients. Despite anatomical, physiological and biochemical differences among animal species, the pharmacokinetic disposition of Pt in the cockatoo shares some features with the kinetics reported previously in rodents, dogs and human beings.

Doxycycline plasma concentrations in macaws fed a medicate corn diet.

A trial was conducted to determine the doxycycline plasma concentrations attained by feeding a medicated corn diet to large psittacine birds. Doxycycline is the preferred drug for the treatment of chlamydiosis in psittacine birds. Healthy macaws were fed a 0.1% doxycycline-medicated corn diet for 45 days, and plasma doxycycline concentrations were determined by microbiological assay on treatment days 3, 15, 30, and 45. Plasma doxycycline concentrations exceeded 1 microgram/ml in 87% of the samples assayed. As blood concentrations of 1 microgram/ml are considered therapeutic, a doxycycline-medicated corn diet may be efficacious in the treatment of chlamydiosis in large psittacine birds.

Pharmacokinetics of amikacin in African gray parrots.

Amikacin sulfate was administered to African gray parrots at 3 dosages (5, 10, and 20 mg/kg) via 2 routes (IV and IM). The elimination half-time was approximately 1 hour (range, 0.9 to 1.34 hour). The apparent bioavailability of IM administered drug was 61 to 106% and was not dose-related.

[Antibiotic therapy in psittacines]. / Antibiotikatherapie bei Psittaziden.

The use of different antibiotics in psittacines is described. Among other aspects especially the anatomy of the bird and its consequence for the application of medicaments is taken into account. The use of antibiotics in psittacines often turns out to be difficult because of missing data about their pharmacokinetics, dosage, period of application and their compatibility. In order to deal with the increasing number of pet-birds in the veterinary practice, further examinations have to be conducted.

Antibiotic aerosolization: tissue and plasma oxytetracycline concentrations in parakeets.

Oxytetracycline hydrochloride (OTC) was delivered to adult parakeets by aerosolization using a DeVilbiss model 65 ultrasonic nebulizer. Trachea, lung, and plasma concentrations were ascertained at 1, 2, 4, 6, and 8 hours postaerosolization (PA). An average of 284 ml of a solution containing 2 mg OTC/ml was aerosolized over a 1-hour period into a 0.0596 M3 chamber containing 10 parakeets. The trachea and lung concentrations were more than 10 micrograms/g at 1 and 2 hours PA, had decreased to approximately 3 micrograms/g by 4 hours PA, and were below 2 micrograms/g by 8 hours. The plasma concentration never exceeded 2.6 micrograms/ml and was at 1.6 micrograms/ml by 8 hours. This study demonstrates that it is possible to achieve therapeutic concentrations of OTC by aerosolization in lung and trachea, but treatment may need to be repeated every 4-6 hours. Since the plasma concentration never reached high levels, aerosolization under the conditions of this study is not an effective way to treat systemic infections outside the respiratory tract.