Sarcoptes scabei var. wombati infection in the common wombat (Vombatus ursinus)

Sarcoptic mange has been identified as the most significant infectious disease affecting the common wombat (Vombatus ursinus). Biochemistry and haematology values for wild common wombats have not been published previously. A 35% of the wombat population were exhibiting clinical signs of the disease. Significant changes in blood haematology and biochemistry parameters were observed in affected animals. A seasonal variation in numbers of animals affected was demonstrated. Females appeared to be more commonly affected than males although the reason for this is not forthcoming.     

A microscopic investigation of enamel in wombat (Vombatus ursinus)

Summary A study of the enamel of continuously growing Vombatus ursinus molars was carried out using the techniques of light microscopy, hardness testing, scanning electron microscopy and transmission electron microscopy. From the erupted end to within 8 mm of the growing end, mature enamel was observed and it was found that between comparable areas there were no significant ultrastructural differences in enamel; however, small (12nm diameter), loosely packed needle-like crystals characteristic of developing enamel were observed near the growing end. Mature enamel was found to consist of three optically-translucent regions interleaved with two opaque regions. Opaque enamel was softer than translucent enamel. The opacity and relative softness characteristic of two of the enamel regions was not related to prism pattern or orientation; it was, however, related to the presence of voids (28 nm diameter) in these regions.     

Secretion of electrolytes,protein and urea by the mandibular gland of the common wombat (Vombatus ursinus)

Saliva was collected from the mandibular glands of anaesthetized common wombats (Vombatus ursinus) to ascertain maximal flow rates, salivary compostion and possible adaptations, particularly PO₄ ^3- secretion, to assist digestion. After temporary catheterization of the main duct through its oral opening, salivary secretion was evoked at flow rates ranging from 0.02±0.002 (±SEM) ml·min^-1 (0.7±0.07 l·min^-1·kg body weight^-1) to 0.4±0.05 ml·min^-1(14±1.9 l·min^-1·kg body weight^-1) by ipsilateral intracarotid infusion of acetylcholine. The [Na⁺] (15±5.1 to 58±8.6 mmol·l^-1) and [HCO₃ ^-] (35±1.9 to 60±1.9 mmol·l^-1) were positively correlated with salivary flow rate. The [K⁺] (58±5.2 to 30±2.4 mmol·l^-1), [Ca²⁺] (10.4±1.67 to 4.1±0.44 mmol·l^-1), [Mg²⁺] (0.94±0.137 to 0.17±0.032 mmol·l^-1), [Cl^-] (71±9.2 to 45±6.0 mmol·l^-1), [urea] (9.3±0.79 to 5.1±0.54 mmol·l^-1), H⁺ activity (29±1.6 to 17±1.6 nEq·l^-1) and amylase activity (251±57.4 to 92±23.3 kat·l^-1) were negatively correlated with flow. Both concentration and osmolality fell with increasing flow at the lower end of the flow range but osmolality always increased again by maximal flow whereas the relation between protein and flow was not consistent at the higher levels of flow and stimulation. Salivary [PO₄ ³⁺] was not correlated with flow and at 3–14% of the plasma concentration was extremely low. Thus, in contrast to its nearest relative, the koala (Phascolarctos cinereus), the wombat secretes little PO₄ ³⁺ presumably because it does not need high levels of PO₄ ³⁺ in its saliva to facilitate microbial digestion of plant fibre.Abbreviations bw body weight - ww wet weight     

Faecal progesterone metabolites and behavioural observations for the non-invasive assessment of oestrous cycles in the common wombat (Vombatus ursinus) and the southern hairy-nosed wombat (Lasiorhinus latifrons)

Wombats belong to Australia's unique marsupial species. Two of the three remaining species, the common wombat (Vombatus ursinus) and the southern hairy-nosed wombat (Lasiorhinus latifrons) are abundant. The third species, the northern hairy-nosed wombat (Lasiorhinus krefftii) has only about 115 individuals left in the wild. This study aimed to gain further insight into the basic reproductive biology of wombat species and evaluate the value of faecal progesterone metabolites and behavioural patterns as a means for non-invasive monitoring of the oestrous cycle in common and the southern hairy-nosed wombats. In an initial study, three different faecal steroid assays showed that 20alpha-OH-pregnanes were the main progesterone metabolites. These metabolites were examined in captive female common wombats (n = 5) and southern hairy-nosed wombats (n = 2). In one female common wombat 11.7 days with a follicular phase of 25.6 +/- 6.3 days and a luteal phase of 28.2 +/- 12.7 days. The data for faecal pregnanes obtained in the southern and in one male common wombat oestrous related behavioural data were obtained. Individual cycling females exhibited a significant relationship between plasma progesterone and faecal pregnanes. In the common wombat, the values for faecal pregnanes showed an oestrous cycle length of 55.1 +/- hairy-nosed wombat during the breeding season gave an oestrous cycle length of 41.1 +/- 12.8 days with a follicular phase of 27.9 +/- 12.3 days and a short luteal phase of 13.3 +/- 1.1 days. The behavioural data show that the faecal sniffing behaviour of the male, tended to increase around the time that oestrous was found. In conclusion, monitoring of 20alpha-OH-pregnanes in wombat faeces could be a useful methodology to monitor reproductive cycles in the wombat, and can possibly be applied to monitor the endangered northern hairy-nosed wombat.     

Coccidiosis in common wombats (Vombatus ursinus).

Eimeria arundeli is a widespread coccidian parasite of the common wombat (Vombatus ursinus), and has been considered to be nonpathogenic. We describe disease in two captive juvenile wombats ascribed to infection with E. arundeli. One animal had diarrhea, the second had mucoid soft feces and lost weight over several weeks prior to death. Masses of coccidial gametocytes in hypertrophic cells in the lamina propria distended villi, causing grossly visible raised pale thickened regions over extensive areas of the mucosa of the small intestine in both animals. Neutrophils infiltrated affected mucosa, and there was an inflammatory exudate into the intestinal lumen in case one. In case two, neutrophils infiltrated the lamina propria of villi focally, crypts were distended by necrotic debris, and epithelium on villi was extremely attenuated. No bacterial pathogens were isolated from lung and intestine in case one; case two was not cultured. Oocysts consistent with E. arundeli were present in large numbers in floatations of diarrheic feces in both cases.     

Isolation and chemical synthesis of a major, novel biliary bile acid in the common wombat (Vombatus ursinus): 15alpha-hydroxylithocholic acid

The major bile acids present in the gallbladder bile of the common Australian wombat (Vombatus ursinus) were isolated by preparative HPLC and identified by NMR as the taurine N-acylamidates of chenodeoxycholic acid (CDCA) and 15alpha-hydroxylithocholic acid (3alpha,15alpha-dihydroxy-5beta-cholan-24-oic acid). Taurine-conjugated CDCA constituted 78% of biliary bile acids, and (taurine-conjugated) 15alpha-hydroxylithocholic acid constituted 11%. Proof of structure of the latter compound was obtained by its synthesis from CDCA via a Delta14 intermediate. The synthesis of its C-15 epimer, 15beta-hydroxylithocholic acid (3alpha,15beta-dihydroxy-5beta-cholan-24-oic acid), is also reported. The taurine conjugate of 15alpha-hydroxylithocholic acid was synthesized and shown to have chromatographic and spectroscopic properties identical to those of the compound isolated from bile. It is likely that 15alpha-hydroxylithocholic acid is synthesized in the wombat hepatocyte by 15alpha-hydroxylation of lithocholic acid that was formed by bacterial 7alpha-dehydroxylation of CDCA in the distal intestine. Thus, the wombat appears to use 15alpha-hydroxylation as a novel detoxification mechanism for lithocholic acid.     

An investigation into the similarities and differences governing the cryopreservation success of koala (Phascolarctos cinereus: goldfuss) and common wombat (Vombatus ursinus: shaw) spermatozoa

The aim of this study was to determine the relative cryopreservation success of koala and wombat spermatozoa and to investigate reasons for their respective post-thaw survival by examining the sperm's response to a range of osmotic media and determining the presence and distribution of F-actin. An hypothesis was proposed that F-actin may be imparting a degree of structural inflexibility to the koala sperm plasma membrane; hence, exposure of spermatozoa to cytochalasin D (5 microM), a F-actin depolymerisation agent, should result in increased plasticisation of the membrane and greater tolerance of cell volume changes that typically occur during cryopreservation. In experiment 1, koala (n = 4) and wombat (n = 4) spermatozoa packaged in 0.25 mL straws were cryopreserved using two freezing rates (fast-3 cm above liquid N2 interface; slow-6 degrees C/min in a freezing chamber) and two glycerol concentrations (8 and 14% v/v) in a tris-citrate glucose buffer with 15% (v/v) egg yolk. Wombat spermatozoa showed better (P < 0.01) post-thaw survival (% motile, % intact plasma membranes, % decondensed sperm heads) than koala spermatozoa. When exposed to media of varying osmolality, koala spermatozoa were less tolerant (% intact plasma membrane) of hyper-osmotic conditions (920 and 1410 mOsmol/kg) than wombat spermatozoa. F-actin was localised using a monoclonal antibody but only found in the wombat sperm head. When koala and wombat spermatozoa were exposed to media of varying osmolality, cytochalasin D had no beneficial effect on sperm survival (% intact plasma membranes). This study has demonstrated that wombat spermatozoa are highly tolerant of cryopreservation when compared to koala sperm but that spermatozoa from both species show greatest post-thaw survival when frozen slowly in 14% glycerol. Koala sperm are also particularly susceptible to hyper-osmotic environments but lack of detectable F-actin in the koala spermatozoan suggests that poor cryopreservation success in this species is unlikely to be associated with F-actin induced plasma membrane inflexibility.     

A seroprevalence survey of Toxoplasma gondii in common wombats (Vombatus ursinus)

Serum was collected from 23 wild common wombats (Vombatus ursinus) on a pastoral property in the Southern Tablelands of New South Wales, Australia (231N 616E) between 3rd August 2001 and 25th March 2002. The serum was tested using three serological methods for antibodies to Toxoplasma gondii. Six animals (26.1%) were shown to have antibodies to T. gondii. The latex agglutination test proved to be less sensitive than the direct agglutination test or the modified agglutination test. This is the first serological survey of T. gondii in wombats. This is the first recorded use of the latex agglutination test on wombat serum. This study demonstrated the highest percentage of seropositive animals in any serological survey for T. gondii in marsupials.     

Electron microscopic investigation relating the occlusal morphology to the underlying enamel structure of molar teeth of the wombat (Vombatus ursinus)

This investigation relates the occlusal morphology of the continuously growing molars of common wombats (Vombatus ursinus) to the underlying enamel ultrastructure that was investigated using the techniques of light microscopy, scanning electron microscopy, and transmission electron microscopy. The main feature of the occlusal enamel was a prominent ridge, which followed the contour of the dentine-enamel junction (DEJ). It was found that the occlusal morphology depended upon the orientation of the dentinal and enamel tissues, variations in prism orientation, Hunter-Schreger bands (HSB), and presence or absence of cleavage. Cleavage of enamel promoted by sheets of parallel prisms occurred along the face between the DEJ and the ridge, whereas on the face between the ridge and the cementum-enamel junction (CEJ) cleavage was inhibited by HSB. The slope of the latter face was mainly due to a decrease in wear resistance going from the ridge, where prisms were intercepted transversely, toward the CEJ, where they were intercepted obliquely. Occasionally small surface undulations were observed on the face between the ridge and the CEJ. These undulations were found to correspond to gradually decussating enamel regions. The pronounced cleavage of enamel parallel to the face between the DEJ and the ridge played an important role in conferring on the continuously growing molars a distinct property to develop and maintain a self-sharpening ridge throughout the life of the tooth.     

Clinical response of captive common wombats (Vombatus ursinus) infected with Sarcoptes scabiei var. wombati

Seven common wombats (Vombatus ursinus) were exposed and two of these were re-exposed to Sarcoptes scabiei var. wombati (Acari: Sarcoptidae). For wombats exposed for the first time, five exposed to 5,000 mites on their shoulder developed moderate to severe parakeratotic mange after 11 wk compared with two given 1,000 mites that developed mild clinical signs of mange after 11 wk. For re-exposed wombats, one of two given 5,000 mites developed mild parakeratotic mange and the other developed severe parakeratotic mange. Initial signs of mange were erythema followed by parakeratosis, alopecia, excoriation and fissuring of parakeratotic crust and skin. Erythema usually became apparent within 14 days after exposure (DAE) or within 24 hrs of re-exposure. Parakeratosis was visible 14-21 DAE and alopecia first occurred 35-77 DAE. Clinical signs increased in severity over time and lesions spread slowly from the site of exposure. Mangy wombats scratched excessively, lost weight, and exhibited a significant neutrophilia compared with control wombats. Treatment of mange with three injections of ivermectin, 300 micrograms/kg, 10 days apart led to complete resolution of clinical signs. However mites were not entirely eliminated until wombats received a second regime of treatment.     

Circadian variation in resource quality: leaf water content and its relevance to eastern grey kangaroo Macropus giganteus and common wombat Vombatus ursinus

Green leaves of six grass species in temperate Australia showed considerable circadian variation (especially in summer) in water content, which peaked late in the night and fell from sunrise to an afternoon minimum. In summer, water content of a set of ‘wetter’ species (Axonopus affinis, Pennisetum clandestinum and Paspalum dilatatum) was consistently higher and varied less profoundly through the 24 h than that of a ‘drier’ set (Imperata cylindrica, Poa labillardieri and Themeda triandra). Hour‐to‐hour and day‐to‐day variation in leaf water content of P. dilatatum in summer partly but imperfectly reflected ambient temperature. Recognizing the risks for herbivores of visiting water sources, we considered leaf water content as a source of free water for leaf‐grazing herbivores, eastern grey kangaroos Macropus giganteus and common wombats Vombatus ursinus. Using known field metabolic rates, energy requirements and digestive efficiencies, we calculated these two species' free‐water intakes when satisfying their energy needs with these grasses but distributing their grazing in different schedules. Both species would obtain more free water by their observed foraging schedules than by random or daytime‐only schedules. We calculated that the measured grasses could satisfy the water requirements of wombats but not always those of kangaroos, who would need to drink when forage water content was less than about 70%. Water content of grass leaf could rise above and fall below this value within a day, creating some scope for kangaroos to manage their need to visit water by adjusting foraging schedules or choice of grass species. In future studies, circadian variation in leaf water content should be considered as a factor (together with their thermal physiology) driving herbivores' activity scheduling, and affecting their dietary selection.     

Cellular response in the dermis of common wombats (Vombatus ursinus) infected with Sarcoptes scabiei var. wombati

The cellular response in the dermis of common wombats (Vombatus ursinus) with sarcoptic mange exhibited some typical aspects of an immune response to Sarcoptes scabiei. There was an induction phase for wombats experimentally infected with S. scabiei represented by absence of a dermal inflammatory infiltrate for at least 12 days after infection. T lymphocytes, plasma cells, mast cells, and neutrophils then entered the dermis, consistent with a type IV (delayed) hypersensitivity response. In free-living wombats with severe parakeratotic sarcoptic mange eosinophils were also present in the dermis suggesting that a type I (immediate) hypersensitivity response may develop after a type IV hypersensitivity response. Absence of plasma cells and B lymphocytes in free-living wombats with severe parakeratotic sarcoptic mange compared with their presence in wombats experimentally infected with S. scabiei suggested that some immune tolerance may develop with severe infections. A large proportion of cells in the dermal response were not identified but were possibly cells of connective tissue. The thickness of the epidermis increased within 4 days in response to S. scabiei infection. Some antibodies raised against human leucocyte antigens CD3, CD5, HLA-DP, DQ, DR, and CD79b cross-reacted with leucocyte antigens of common wombats and were used to identify cell types in inflammatory infiltrates using immunohistochemistry.     

Sperm membrane fatty acid composition in the Eastern grey kangaroo (Macropus giganteus), koala (Phascolarctos cinereus), and common wombat (Vombatus ursinus) and its relationship to cold shock injury and cryopreservation success

Marsupial spermatozoa tolerate cold shock well, but differ in cryopreservation tolerance. In an attempt to explain these phenomena, the fatty acid composition of the sperm membrane from caput and cauda epididymides of the Eastern grey kangaroo, koala, and common wombat was measured and membrane sterol levels were measured in cauda epididymidal spermatozoa. While species-related differences in the levels of linolenic acid (18:3, n-6) and arachidonic acid (20:4, n-6) were observed in caput epididymal spermatozoa, these differences failed to significantly alter the ratio of unsaturated/saturated membrane fatty acids. However in cauda epididymidal spermatozoa, the ratio of unsaturated/saturated membrane fatty acids in koala and kangaroo spermatozoa was approximately 7.6 and 5.2, respectively; substantially higher than any other mammalian species so far described. Koala spermatozoal membranes had a higher ratio of unsaturated/saturated membrane fatty acids than that of wombat spermatozoa (t = 3.81; df = 4; p < or = 0.02); however, there was no significant difference between wombat and kangaroo spermatozoa. The highest proportions of DHA (22:6, n-3), the predominant membrane fatty acid in cauda epididymidal spermatozoa, were found in wombat and koala spermatozoa. While species-related differences in membrane sterol levels (cholesterol and desmosterol) were observed in cauda epididymidal spermatozoa, marsupial membrane sterol levels are very low. Marsupial spermatozoal membrane analyses do not support the hypothesis that a high ratio of saturated/unsaturated membrane fatty acids and low membrane sterol levels predisposes spermatozoa to cold shock damage. Instead, cryogenic tolerance appears related to DHA levels.     

In vitro maturation and intracytoplasmic sperm injection of oocytes collected from hormonally stimulated common wombats, Vombatus ursinus

Porcine FSH/LH stimulation successfully induced development of multiple large (>or=4mm) antral follicles in 10 of 11 common wombats. A mean of 5.5 metaphase II (MII) oocytes were aspirated from wombats that were stimulated during the follicular phase of the oestrous cycle (n=3) or after pouch young removal (n=3). Three subadults (n=3) and two anoestrus adults did not produce MII oocytes despite pFSH/pLH administration. In vitro maturation of immature oocytes at the time of aspiration doubled the number of MII oocytes that could be collected from pFSH/pLH stimulated wombats. Immature oocytes with cumulus attached, matured more readily to the MII stage than immature oocytes without cumulus. Following intracytoplasmic sperm injection (ICSI), approximately 5% of the oocytes that were MII at the time of collection cleaved. Approximately 5% of those that were matured by in vitro maturation (IVM) formed two polar bodies following ICSI, although they not cleave. Parthenogenesis cannot be excluded. This demonstrates that assisted reproductive technologies may be applicable to the common wombat.     

Sarcoptes scabiei: The Mange Mite with Mighty Effects on the Common Wombat (Vombatus ursinus)

Parasitism has both direct and indirect effects on hosts. Indirect effects (such as behavioural changes) may be common, although are often poorly described. This study examined sarcoptic mange (caused by the mite Sarcoptes scabiei) in the common wombat (Vombatus ursinus), a species that shows severe symptoms of infection and often causes mortality. Wombats showed alterations to above ground behaviours associated with mange. Infected wombats were shown to be active outside of the burrow for longer than healthy individuals. Additionally, they spent more time scratching and drinking, and less time walking as a proportion of time spent above ground when compared with healthy individuals. They did not spend a higher proportion of time feeding, but did have a slower feeding rate and were in poorer body condition. Thermal images showed that wombats with mange lost considerably more heat to the environment due to a diminished insulation layer. Infection status did not have an effect on burrow emergence time, although this was strongly dependent on maximum daily temperature. This study, through the most detailed behavioural observations of wombats to date, contributes to a broader understanding of how mange affects wombat health and abundance, and also to our understanding of the evolution of host responses to this parasite. Despite being globally dispersed and impacting over 100 species with diverse intrinsic host traits, the effects of mange on hosts are relatively poorly understood, and it is possible that similar effects of this disease are conserved in other host species. The indirect effects that we observed may extend to other pathogen types.     

Sarcoptes mange (Sarcoptes scabiei) increases diurnal activity of bare-nosed wombats (Vombatus ursinus) in an agricultural riparian environment

Sarcoptes mange is an important disease that affects the health, mobility and longevity of bare-nosed wombats (Vombatus ursinus) in Australia. We measured the activity patterns of wombats infected with varying levels of mange in an agricultural riparian environment using motion-sensing cameras. Over a 10 month period we observed a greater increase in nocturnal activity of mange-free wombats than those with mange on six or more body sections. The percentage of mange-infected wombats was greater during the day, but in the 6 h after midnight, wombats were detected with fewer mange-infected segments. Air temperature at the time of wombat detections was generally higher for individuals with mange than those without mange. Our results show that diurnal activity of wombats is likely to increase with higher levels of infection by sarcoptes mange. Increased diurnal activity is likely to present serious problems for the persistence of sustainable populations of wild wombats.     

Morphology of the Jaw-Closing Musculature in the Common Wombat (Vombatus ursinus) Using Digital Dissection and Magnetic Resonance Imaging

Wombats are unique among marsupials in having one pair of upper incisors, and hypsodont molars for processing tough, abrasive vegetation. Of the three extant species, the most abundant, the common wombat (Vombatus ursinus), has had the least attention in terms of masticatory muscle morphology, and has never been thoroughly described. Using MRI and digital dissection to compliment traditional gross dissections, the major jaw adductor muscles, the masseter, temporalis and pterygoids, were described. The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials. This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet. The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force. MRI scans allow more detail of the muscle morphology to be observed and the technique of digital dissections greatly enhances the knowledge obtained from gross dissections.