Single-dose pharmacokinetics of oxytetracycline and penicillin G in tammar wallabies (Macropus eugenii)

McLelland, D.J., Barker, I.K., Crawshaw, G., Hinds, L.A., Spilsbury, L., Johnson, R. Single‐dose pharmacokinetics of oxytetracycline and penicillin G in tammar wallabies (Macropus eugenii). J. vet. Pharmacol. Therap. 34 , 160–167. The pharmacokinetics of oxytetracycline and penicillin G was investigated in tammar wallabies (Macropus eugenii). Groups of eight healthy tammar wallabies were administered i.v. oxytetracycline hydrochloride (40 mg/kg), i.m. long‐acting‐oxytetracycline (20 mg/kg), i.v. sodium penicillin G (30 mg/kg), or i.m. procaine/benzathine penicillin G (30 mg/kg). Plasma concentrations of oxytetracycline were determined using high‐performance liquid chromatography. Pharmacokinetic parameters were comparable to those reported for eutherians of equivalent size and suggest that the practice of adjusting allometrically scaled doses to account for the lower metabolic rate of marsupials may not be valid. Long‐acting oxytetracycline and penicillin G both demonstrated depot effects. However, the plasma concentrations achieved question the therapeutic efficacy of the long‐acting preparations.     

Epizootics of sudden death in tammar wallabies (Macropus eugenii) associated with an orbivirus infection

Epizootics of sudden death in tammar wallabies (Macropus eugenii) occurred at six research facilities and zoological gardens in New South Wales, Australia, in late 1998 and at one Queensland research facility in March 1999. There were 120 confirmed tammar wallaby deaths during this period; however, population censuses indicated that up to 230 tammar wallabies may have died. The majority of animals died without premonitory signs. A small proportion of wallabies exhibited increased respiratory rate, sat with a lowered head shortly before death or were discovered in lateral recumbency, moribund and with muscle fasciculations. Gross postmortem findings consistently included massive pulmonary congestion, mottled hepatic parenchyma and subcutaneous oedema throughout the hindlimbs and inguinal region. Approximately 30% of the animals examined also had extensive haemorrhage within the fascial planes and skeletal muscle of the hindlimb adductors, inguinal region, ventral thorax, dorsal cervical region and perirenal retroperitoneal area. The tissues of affected animals became autolytic within a short period after death. Bacteriological examination of tissues from 14 animals did not provide any significant findings. Toxicological examination of the gastric and colonic contents of four animals did not reveal evidence of brodifacoume or other rodenticides. Viruses from the Eubenangee serogroup of the Orbivirus genus were isolated from the cerebral cortex of nine, and the myocardium of two, tammar wallabies and the liver and intestine of another tammar wallaby. A similar orbivirus was also isolated from the cerebrospinal fluid of another tammar wallaby that died suddenly. The disease agent appears to be a previously unrecognised orbivirus in the Eubenangee serogroup. This is the first report of epizootics of sudden deaths in tammar wallabies apparently associated with an orbivirus infection.     

Toxoplasmosis in Tammar wallabies (Macropus eugenii) in the Budapest Zoo and Botanical Garden (2006-2010)

Smaller macropodid species (commonly referred to as wallabies) are extremely susceptible to toxoplasmosis: in most cases, infection with Toxoplasma gondii leads to death within a short time. Between June 2006 and July 2010, T. gondii was detected by immunohistochemical examination in six Tammar wallabies (Macropus eugenii) that died in the Budapest Zoo and Botanical Garden; in another four specimens histopathology revealed T. gondii-like organisms (which could not be differentiated from Neospora caninum solely by morphology), and in another 11 animals toxoplasmosis as the possible cause of death could not be excluded. The current zoo population of 12 Tammar wallabies was tested for T. gondii IgG antibodies by the modified agglutination test (MAT), with negative results. We suppose that most of the deaths were due to acute toxoplasmosis resulting from a recent infection.     

Methane production by red-necked wallabies (Macropus rufogriseus)

The claimed low production of CH(4) by kangaroos and marsupials in general has been questioned because of a lack of data. The extent of their CH(4) production is of interest both from the point of view of discussing meat production of marsupials and as a basis for developing methods to reduce CH(4) production from ruminants. In the present experiment, the CH(4) production of 8 red-necked wallabies (Macropus rufogriseus) was measured of which 4 were fed 2 different diets in an open-circuit respiration chamber. These results were compared with a newly developed, inexpensive, and simple method that does not influence the behavior of the animal, and where the ratio between CH(4) and CO(2) is measured and used together with the calculated CO(2) to quantify the CH(4) production. The experiment demonstrated that the wallabies produce CH(4). However, the amount of CH(4) produced by these wallabies was between 1.6 and 2.5 L/d equivalent to 1.6 and 2.5% of GE or 2.2% and 3.5% of DE intake and 0.22 L/BW, kg(0.75). This is between 25 and 33% of what can be expected from ruminants fed the same diet. Based on the uneven release of CH(4) with time, it is most likely that the CH(4) is excreted through flatulence and not through breathing as is seen in ruminants. The experiments also showed that a reasonably accurate determination of the CH(4) production of a group of animals can be obtained by simply measuring the CH(4)/CO(2) ratio over a limited time span. This may represent the situation in a natural setting better than measurements in a respiration chamber. It was found that the CH(4)/CO(2) ratio in itself represents a reasonable prediction of the proportion of feed GE that is lost as CH(4), and that this method offers new opportunities for CH(4) measurements on a large number of animals.     

Toxoplasmosis in captive Bennett's wallabies (Macropus rufogriseus) in Argentina

Wallabies and other Australian marsupials are among the most susceptible species to Toxoplasma gondii. Fatal generalized toxoplasmosis was diagnosed in two captive 3 year-old female Bennett's wallabies (Macropus rufogriseus) from Argentina (w 1 and w 2) with a history of sudden death. Both animals had internal joeys which died 2 days after their mothers. Serologically, both females and one adult male without clinical signs from the same enclosure (w 3) had antibody titers for T. gondii>or=800 by the modified agglutination test (MAT); another adult male (w 4) was negative (MAT titer<25). Microscopically, tachyzoites were observed associated to non-suppurative meningoencephalitis, hepatitis, myositis, myocarditis and severe enteritis in hematoxylin and eosin stained sections from both w 1 and w 2. Immunohistochemically, parasites in heart, brain and liver sections of both female wallabies reacted with T. gondii antiserum. T. gondii was isolated from brain tissues of w 1 and w 2 by bioassay in mice and by culture in bovine monocytes and both isolates were cryopreserved. Genomic DNA was isolated from tachyzoites grown in cultures derived from both animals. The primer pair B22/B23 specific for T. gondii produced 115bp amplicons on poliacrylamide electrophoretic gels. Stray cats were suspected as the possible source of infection. Not all infected macropods were ill, showing that the infection may be asymptomatic and is not always fatal. A vertical infection could not be proved in the joey from w 2. As far as we know, this is the first confirmed report of toxoplasmosis in Bennet's wallabies in Argentina.     

Pharmacokinetics of intravenous clindamycin phosphate in captive Bennett's wallabies (Macropus rufogriseus)

This study was designed to investigate the pharmacokinetics of clindamycin, a lincosamide antibiotic, in Bennett's wallabies. The pharmacokinetic properties of a single intravenous (IV) dose of clindamycin were determined in six wallabies. A single 20‐min IV infusion of 20 mg/kg of clindamycin was administered, followed by blood collection prior to, and up to 12 hr after clindamycin administration. Plasma clindamycin concentrations were determined by high‐pressure liquid chromatography (HPLC) with ultraviolet (UV) detection. Pharmacokinetic variables were calculated using a two‐compartment model with first order elimination which best fit the data. The mean volume of distribution at steady‐state, distribution half‐life, and elimination half‐life were 898.25 ml/kg, 0.16 hr, 1.79 hr, respectively. No adverse effects were noted after IV administration.     

Evaluation of medetomidine-alfaxalone and medetomidine-ketamine in semi-free ranging Bennett's wallabies (Macropus rufogriseus)

Twenty-six adult semi-free-ranging Bennett's wallabies were anesthetized. Animals in group MA received medetomidine 0.1 mg/kg and alfaxalone 4 mg/kg i.m. in a 5-ml dart, whereas those in group MK received medetomidine 0.1 mg/kg and ketamine 5 mg/kg i.m. in a 3-ml dart. Dosages were based on estimated body weights. The wallabies were allowed to recover spontaneously or, if still nonresponsive at the end of the procedure, were given atipamezole 0.5 mg/kg (half the dose via i.m. and the other half via i.v.). Heart rate and respiratory rate were monitored at 5-min intervals, temperature at 10-min intervals, and two arterial blood samples were taken for blood gas analysis. Statistical analysis was performed by using analysis of variance (P < 0.05). The use of 5-ml darts in group MA compared with 3-ml darts in group MK could potentially increase the risk of iatrogenic trauma and should be considered. Induction and maintenance of anesthesia were satisfactory in both groups. There were no significant differences between the groups in mean time to first effect, recumbency, and approach, or to time to sternal recumbency and standing after reversal with atipamezole. Although bradycardia was present in both groups, no statistical differences were calculated for respiratory rate and heart rate, whereas the mean cloacal temperature was significantly lower in group MA (P = 0.01). Mixed acid-base disturbances occurred in both groups. All but one animal in group MK needed atipamezole at the end of the procedure. No adverse effects were observed after recovery.     

Comparison of three anaesthetic protocols in Bennett’s wallabies (Macropus rufogriseus)

ObjectiveInvestigate physiological and sedative/anaesthetic effects of xylazine, medetomidine or dexmedetomidine combined with ketamine in free-ranging Bennett's wallabies.Study designProspective clinical trial.AnimalsTwenty-six adult free-ranging Bennett's wallabies.MethodsAnimals were darted intramuscularly with one of three treatments: xylazine and ketamine, 2.0 and 15.0 mg kg^?1, respectively (XK): medetomidine and ketamine 0.1 and 5.0 mg kg^?1 (MK) and dexmedetomidine and ketamine 0.05 and 5.0 mg kg^?1 (DMK). Body weights were estimated. If the animal was still laterally recumbent after 45 minutes of anaesthesia, then an alpha-2 adrenoceptor antagonist, atipamezole, was administered (XK: 0.4 mg kg^?1, MK: 5 mg kg^?1, DMK: 2.5 mg kg^?1). Heart rate (HR) and respiratory rate (f_R) were recorded at 5-minute intervals and temperature at 10-minute intervals. Venous blood was taken 30 minutes after initial injection. Statistical analysis utilized anova. p < 0.05 was considered significant.ResultsAnimals became recumbent rapidly in all groups. XK animals had muscle twitches, responded to external stimuli, and three animals required additional dosing; this was not observed in the MK and DMK groups. HR (mean ± SD beats minute^?1) in XK (81 ± 4) was significantly higher than MK (74 ± 2) and DMK (67 ± 4). There were no differences in f_R, temperature, blood-gas and biochemical values between groups. More animals in MK (9/10) and DMK (5/6) needed antagonism of anaesthesia compared with XK (1/10). There were no adverse effects after anaesthesia.Conclusion and clinical relevanceCardio-respiratory effects were similar in all groups. There were fewer muscle twitches and reactions to external stimuli in MK and DMK. Duration of anaesthesia was shorter in XK; most animals in MK and DMK needed atipamezole to assist recovery. All three treatments provided satisfactory sedation/anaesthesia and are suitable for use in Bennett's wallabies.     

Gastric amebiasis due to Entamoeba histolytica in a Dama wallaby (Macropus eugenii)

A 1.5-year-old captive female Dama wallaby (Macropus eugenii) died after a 3-month period of progressive weight loss, anorexia, bloat, and diarrhea. Histopathologic examination revealed numerous Entamoeba histolytica trophozoites within the gastric mucosa and, less frequently, gastric submucosa and submucosal vessels. Immunofluorescent antibody testing confirmed the identity of the trophozoites as E. histolytica. The trophozoites were associated with mild glandular epithelial necrosis, mucosal erosions, and lymphoplasmacytic inflammation. E. histolytica most commonly causes necrotizing and ulcerative colitis in humans and captive nonhuman primates, and it causes necrotizing and ulcerative gastritis in nonhuman primates with sacculated stomachs adapted for leaf fermentation. Rare cases of gastric amebiasis also have been been reported in captive macropods, which also have complex sacculated stomachs. To our knowledge, this is the first report confirming E. histolytica as the cause of gastric amebiasis in a wallaby. The zoonotic potential of this infection in macropods is uncertain.     

Familial ichthyosiform keratoderma in newly out-of-pouch Bennett's wallabies (Macropus rufogriseus) and report of two cases

Primary inherited disorders of cornification in veterinary medicine are uncommon and rarely reported. Herein described is a unique syndrome associated with keratoderma that occurred in two Bennett's wallaby siblings (Macropus rufogriseus), and was characterized by profound thickening of the pad skin of all feet, generalized scaling of haired skin, and death within 7 weeks of out-of-pouch experience. The male also had depressed serum zinc levels. In addition, the male had, on electron microscopic exam of his skin, the presence of abnormal lipid deposits within the stratum corneum and stratum granulosum. The combination of clinical features and electron microscopic findings strongly suggests a syndrome analogous to harlequin ichthyosis or lamellar ichthyosis in humans.     

First description of onychomycosis caused by Chrysosporium keratinophilum in captive Bennett's wallabies (Macropus rufogriseus rufogriseus)

Seven Bennett's wallabies (Macropus rufogriseus rufogriseus) presented within a period of several months with onychodystrophy, onychomadesis, and severe digital tumefaction. Histopathologic findings included a pseudocarcinomatous hyperplasia of the claw matrix surrounding a cavity filled with keratin and septate hyphae stained with periodic acid Schiff reagent. The fungal species Chrysosporium keratinophilum was identified on cultures. The wallabies were orally treated with ketoconazole (15 mg/kg s.i.d.) for 20 wk. Material and enclosures were cleaned and sprayed with 0.2% enilconazole solution once a month over a period of 4 mo. No improvement of advanced cases was observed, but no new case appeared for the next 6 mo. The positive mycological culture and the invasion of tissues on histopathologic examination suggested that the fungal species C. keratinophilum was implicated in this claw disease. This is the first report of onychomycosis caused by C. keratinophilum in animals.     

Sub-cellular localisation of alkaline phosphatase activity in the cytoplasm of tammar wallaby (Macropus eugenii) neutrophils and eosinophils

Alkaline phosphatase (ALP) has been used in studies of neutrophil morphology and function as a marker for identifying different granule populations. In human neutrophils, ALP is found within secretory vesicles, a rapidly mobilisable vesicle population important for upregulating membrane receptors during early activation. Intra-cellular ALP activity in the heterophils of rabbits and guinea pigs, in contrast, is found only in secondary granules. The neutrophils and eosinophils of tammar wallabies (Macropus eugenii) have previously been reported to contain large amounts of ALP activity when stained using routine cytochemical techniques. To define the subcellular location of ALP in this species, cell suspensions were examined using cerium chloride cytochemistry and transmission electron microscopy (TEM). ALP was found in 2 distinct cytoplasmic compartments. One compartment displayed morphology consistent with a subpopulation of secondary granules while a second tubulo-vesicular population appeared similar to the secretory vesicles of human neutrophils. Thin tubular vesicles containing ALP were also identified within the cytoplasm of tammar wallaby eosinophils. Large numbers of ALP-containing vesicles have not been recognised previously in eosinophils and this may represent a novel cytoplasmic compartment. In both cell types, ALP-containing structures showed alteration in morphology following stimulation with N-formyl-Met-Leu-Phe (fMLP) and PMA.     

Analysis of the expression of immunoglobulins throughout lactation suggests two periods of immune transfer in the tammar wallaby (Macropus eugenii)

Marsupial young are born in an under-developed state without mature immune responses. Prior to the maturation of an immune system, marsupial young are heavily reliant upon immune factors secreted in the milk to defend them against potential microbial pathogens in the environment. In this study, we identified and characterized the immunoglobulin heavy chain constant regions, light chains, polymeric Ig receptor (pIgR), J chain, neonatal Fc receptor (alpha chain) (FcRn) and the chemokine CCL28 from the model marsupial species, the tammar wallaby (Macropus eugenii). Low levels of conservation were seen in motifs in C and Cγ associated with receptor binding and or transcytosis, and this may have potential implications for functionality. We evaluated the expression of immunoglobulin genes in the tammar mammary gland throughout lactation and found that two periods of increased expression of immunoglobulin genes occur. These two periods coincide with the birth of the young, and with its first emergence from the pouch. This increased expression may represent a strategy for maternal immunological protection of the pouch young.