The Order Dasyuromorphia are the carnivorous marsupials. They are characterised by having three pairs of approximately equal sized lower incisors and an absence of fusion between the second and third digits of the hind foot (Strahan 1995). The Order is divided into three Families: Thylacinidae, which contains the extinct thylacine (Thylacinus cynocephalus); Myrmecobiidae, which contains the numbat (Myrmecobius fasciatus); and Dasyuridae, which contains the remaining 66 species. This group includes the Tasmanian devil (Sarcophilus harrisii), quolls, antechinus, dunnarts, kowari (Dasyuroides byrnei) and phascogales (Krajewski & Westerman 2003). Its members are found throughout Australia and New Guinea occupying all environments ranging from high alpine regions (agile antechinus [Antechinus agilis], spot-tailed quoll [Dasyurus maculatus]) to coastal forests (quolls, Tasmanian devils, antechinus, phascogales) and deserts (mulgara [Dasycercus cristicauda], little red kaluta [Dasykaluta rosamondae], kowari).
Dasyurids range in size from the narrow-nosed planigale (Planigale tenuirostris) (4–9 g) to the Tasmanian devil (up to 10 kg). They were initially thought to be predominantly nocturnal, however, continued investigation has demonstrated that many species also forage during the day. Many species of dasyurids are arboreal while others are both arboreal and terrestrial and some are completely terrestrial.
The eastern quoll (D. viverrinus) and Tasmanian devil, once widespread throughout the Australian mainland, are now found only in Tasmania. Due to a combination of habitat destruction and introduced predators, such as the dingo and the fox, most dasyurid populations have declined since European settlement.
Dasyurids are not long-lived. Tasmanian devil life expectancy is up to 6 yr in the wild and 8 yr in captivity. Quolls can be expected to live up to 6 yr in captivity and 3 yr in the wild. The smaller dasyurids generally live for no more than 5 yr in captivity, usually up to 2 in the wild and occasionally up to 3. Males of some groups, such as the antechinus, all die in the wild after their first year (Table 10.1).
2 ANATOMY AND PHYSIOLOGY
Similar to the situation with eutherian carnivores, apart from size there is little variation in the body shape and anatomy of dasyurids. The most extreme variation in body shape of dasyurids is found in the kultarr (Antechinomys laniger). This species has elongated hind limbs and a long tufted tail.
Dasyurids are polyprotodont marsupials as they have three pairs of lower incisors, unlike the diprotodonts which have only a single pair. Dasyurids also have four pairs of pointed upper incisors, well-developed upper and lower canines, two or three pairs of upper and lower blade-like premolars and four pairs of upper and lower molars with sharp shearing cusps (Fig. 10.1). Antechinus are often mistaken for mice but are easily differentiated on the basis of dentition (Fig. 10.2).
Table 10.1 Reproductive characteristics for a range of dasyurids
2.2 Gastrointestinal system
Dasyurids are all carnivorous or insectivorous, although antechinus, phascogales and quolls also consume plant material and nectar, particularly in winter when invertebrates are scarce. Diets are highly digestible, high in protein, water, vitamins and minerals and low in carbohydrates. Therefore, glucose and energy requirements are met primarily from amino acid metabolism. The small intestine contains high levels of trehalase, an enzyme required to digest trehalose, a disaccharide found only in insects. Dasyurids have a short gastrointestinal tract consisting of a simple stomach, small intestine, large intestine and no caecum. Brunner’s glands, which secrete an alkaline fluid that protects the proximal duodenal mucosa from the ulcerating effects of acid-pepsin secretions from the stomach, appear as a thick collar in the duodenum immediately distal to the pylorus. The glands form large lobes that drain into the duodenal lumen. Digesta transit times are brief with 100% excretion occurring 3–4 hr after ingestion in planigales and up to 13 hr in eastern quolls (Hume 1999).
2.3 Musculoskeletal system
The fore feet have five clawed toes, the first toe on the hind foot is either short or absent, and the second and third toes of the hind feet are not fused (didactyly) unlike the diprotodonts where they are fused (syndactyly). The presence of the first digit on the hind foot is usually indicative of an arboreal habit (Fig. 10.2). Two epipubic bones (rudimentary in the thylacine) extend from the anterior aspect of the pubis and support the pouch. As is the case in all marsupials other than bandicoots, dasyurids have no ossified patella. The tail of most species is shorter than the body length. Fat is stored in the tail of some species (Pseudantechinus spp.).
The number of teats ranges from four to 12. Many species lack a pouch. In phascogales eight teats are situated on a circular patch of skin on the abdomen. In other species low lateral folds develop at the sides of the mammary area of lactating females. These folds do not constitute a pouch in the strict sense and provide very little protection for the young which, as they develop, dangle from the mother’s belly between her fore and hind legs. A permanent pouch is present in most ningauis (Ningaui spp.), the kultarr, spot-tailed quoll and Tasmanian devil. Dasyurids have aural, circumanal, interdigital, sternal, paracloacal and labial glands, which are used for scent marking.
2.5 Nervous and sensory systems
Dasyurids, like all marsupials and monotremes, have no corpus callosum. Arachnoid villi have been found in the lumbo-sacral spinal cord of the brown antechinus (A. stuartii), mulgara, kowari, fat-tailed dunnart (Sminthopsis crassicaudata) and white-footed dunnart (S. leucopus) (Attwood & Woolley 1974).
Dasyurids have a vascular retina. The arteries do not branch but form end arteries giving off discrete capillary loops. Marsupials have double cones, which are not found in eutherians. Dunnarts exhibit trichromacy, i.e. there are three separate cone visual pigments sensitive to long (LWS 535 nm), medium (MWS 509 nm) and ultraviolet (UVS 350 nm) wavelengths. Primates are the only other mammalian group to exhibit trichromacy. Trichromacy allows discrimination across a greater section of the visual spectrum to facilitate both diurnal and nocturnal activity. The LWS and MWS pigments are found in single and double cones predominantly in the central retina, while the UVS pigments are only found in single cones predominantly in the dorso-temporal retina. LWS cones are maximally sensitive to the green-yellow range of the spectrum, allowing discrimination of cryptically camouflaged prey such as insects and reptiles. Dunnarts have no tapetum and an intermediate rod: cone ratio of 40:1, which is compatible with an arrhythmic lifestyle. Each cone contains an oil droplet which filters incoming light, thereby enhancing contrast and reducing glare (Arrese et al. 1999; Arrese et al. 2002).
2.6 Metabolism and thermoregulation
Basal metabolic rate (BMR) for dasyurids can be calculated using the following equation:
BMR = 2.39 X body mass (BM)-0.262
Basal metabolic rates are highest in the small insectivores such as planigales, antechinus and phascogales, which are similar to eutherian rates. Rates for other dasyurids, however, are less than half those for eutherian carnivores of similar size. Field metabolic rate (FMR), or the energy cost of free existence, is calculated by the following equation:
Figure 10.1 Dentition of a Tasmanian devil (I4/3, C 1/1, P2/2, M4/4).
Figure 10.2 Brown antechinus (Antechinus stuartii) (a) are frequently mistaken as mice (b) but are easily differentiated on the basis of dentition and anatomy of the feet.
This ranges from six times BMR for 10 g dasyurids to twice BMR for 10 kg dasyurids (Geiser 2003).
Thermoregulatory ability is slow to develop. Kowaris cannot thermoregulate until about 100 d after birth. Body temperatures of adult dasyurids range from 32°C in planigales up to 38°C in the northern quoll (D. hallucatus) with most falling in the 34–36°C range. To combat cold, dasyurids produce heat by shivering. Brown adipose tissue, which is used by eutherians to generate heat, has not been found in marsupials. Dasyurids do not sweat and cope with excessive heat by licking and panting to increase evaporative cooling.
As many dasyurids are small they have a high surface area to volume ratio, which results in high heat loss. Therefore, most if not all species undergo periods of torpor to lower energy expenditure. They do not hibernate but enter shallow periods of daily torpor where the body temperature drops to varying degrees depending on species, ranging from 11°C in the kultarr to 28°C in the dusky antechinus (A. swainsonii). Metabolic rates drop to 10–60% of BMR during torpor bouts, which can last up to 19 hr but usually extend 2–8 hr (Geiser 2003).
The larger dasyurids are better able to conserve body heat due to their smaller surface area to body weight ratio. An eastern quoll weighing 1 kg has a daily energy requirement in summer of approximately 793 kJ. This increases to 1169 kJ/day in winter. Metabolisable energy content is approximately 3.5 kJ/kg for insects and 5 kJ/kg for wallaby flesh. In summer the quoll needs to consume 159 g of mammal flesh (two rat sized mammals) or 227 g of insects (340 insects). In winter this increases to 262 g of mammal flesh or 334 g of insects. In contrast, an 8 kg Tasmanian devil requires 518 g of prey in summer and 578 g of prey in winter, i.e. only twice as much as the quoll despite being eight times as large. The situation is even more extreme for the brown antechinus, which weighs approximately 26 g and has an FMR of 4218 kJ/kg in winter. It must consume 21 g of insects, almost its own body weight each day to survive (Tyndale-Biscoe 2005).
3.1 Reproductive anatomy
Most dasyurid species exhibit sexual dimorphism with males being larger than females. Exceptions are the paucident planigale (Planigale gilesi) and the dunnarts, where there is no significant size difference, and the long-tailed planigale (Planigale ingrami) where the female is larger.
Female marsupials have two uteri and two lateral vaginae. Between the vaginae is a mass of fibrous tissue called the urogenital strand. A birth canal forms within this strand during parturition. This canal becomes permanent after the first parturition in most macropods but in dasyurids the cleft closes rapidly after birth so that no indication of the canal remains.
All dasyurids have a carrot-shaped prostate and bulbourethral glands, two pairs in Tasmanian devils and fat-tailed dunnarts, and three pairs in eastern quolls and brown antechinus.
3.2 Oestrous cycle, mating and gestation
Dasyurids are polyovular and most are monoestrus. Quolls, kultarrs, kowaris, dunnarts, ningauis and planigales are polyoestrus. They have an oestrous cycle which ranges from 24 d in the fat-tailed dunnart up to 60 d in the kowari. Oestrus usually lasts 2–3 d but can persist for up to 14 d in the brown antechinus. Gestation length ranges from 13 to 31 d. Post partum oestrus and ovulation are suppressed during lactation. Ovulation is spontaneous (McAllan 2003). Smaller species have more young in a litter than the larger dasyurid species. It has also been observed that some species give birth to more young than can be accommodated on the teats. However, due to the tiny size of these supernumerary neonates the extent of this phenomenon is poorly understood (Strahan1995).
Females will mate with more than one male, multiple paternity having been demonstrated in the agile antechinus and brush-tailed phascogale (Phascogale tapoatafa). Mating lasts from 1 hr in Tasmanian devils to 12 hr in agile antechinus. Sperm storage, which does not take place in other marsupial groups, occurs in the isthmus of the oviduct. Mating can occur up to 2 wk before ovulation in antechinus and up to 3 d in dunnarts. After mating, the sperm become immobile and reside in the oviduct until ovulation. At ovulation the sperm migrate to the site of fertilisation. At the same time the sperm head moves from its position parallel to the tail to one perpendicular to it, to maximise contact with the egg. The egg is about twice the size of a eutherian egg but the zona pellucida is much thinner. Biased sex ratios have been recorded in semelparous dasyurids, i.e. those that produce offspring in one season only, such as antechinus with first-year mothers producing more females than males. The converse occurs in iteroparous species, i.e. those that produce offspring over multiple seasons, with males more prevalent in the first year (Breed et al. 2003; Taggart et al. 2003).
In antechinus there is a 1–3 wk mating period after which all the males die before the females give birth. The mating period is governed by photoperiod and is longer in duration and later in the year the further north the populations are found. Brown antechinus mate when the rate of change of day length is 90–100 sec/d, while agile antechinus mate when the rate of change is 120–130 sec/d (Tyndale-Biscoe 2005).
Despite increasing testosterone levels, spermatogenesis ceases in mid June in the southern hemisphere, possibly due to photoperiod effects. Mortality occurs because of elevated plasma cortisol levels, which rise from 2.9 ± 0.51 μg/100 mL before mating up to 5.2 ± 0.6 μg/100 mL just prior to death, and a testosterone-dependent decrease in plasma corticosteroid binding globulin from 7.51 ± 0.53 μg/100 mL before mating to 1.96 ± 0.38 μg/100 mL during mating. While in the short term this glucocorticoid increase is beneficial as it enhances the mobilisation of energy reserves for a once-only reproductive effort, in the long term it leads to a range of ultimately fatal syndromes including hippocampal neuronal apoptosis, anaemia, anorexia, reduced splenic follicle size, heavy Babesia spp. parasitaemia, Listeria monocytogenes-induced hepatic necrosis, glomerulonephritis, renal tubular necrosis and gastrointestinal haemorrhage due to gastric and duodenal ulcers. If males are removed or castrated before the mating process begins they can survive for up to 5 yr (Barker et al. 1978; Bradley 2003).
Synchronous mating and complete post mating male mortality also occurs in phascogales and red kalutas, with some mortality reported in mulgaras, northern quolls, dibblers and ningauis. Mortality tends to occur in high-density populations, but not in low-density ones due to decreased competition between males for mates.
A review of dasyurid husbandry can be found in Jackson (2003) and in the Exhibited Animals Protection Act 1995. Recommended dimensions for dasyurid enclosures can be found in Holz (2003) and in the code of practice for the welfare of wildlife during rehabilitation (AG0976 2001).
4.1 Housing and husbandry
Devils and quolls will climb, so a smooth metal skirt at least 1.2 m high around the enclosure is necessary to stop them escaping. Small dasyurids can be maintained in a glass-fronted enclosure made of solid wood at least 10-mm thick, as phascogales in particular are great chewers. Wood or metal nest boxes filled with shredded paper, sea grass or wood shavings should be provided. Arboreal dasyurids such as antechinus and phascogales require roofed enclosures with a maximum gap in the wire of 5–10 mm, depending on the species. Optimum temperature range is 15–30°C, so supplemental heating may be necessary. Enclosures should be spot cleaned daily and small enclosures should receive a full substrate change at least weekly.
Hospital requirements are similar to small eutherian carnivores. Small dasyurids can be maintained in enclosures similar to those described above or in stainless steel wire hospital cages. The wire mesh must be small enough to prevent escape of small species. A nest box should always be provided for security. Quolls and devils need to be held in sturdier accommodation with metal walls. Supplemental heat may need to be provided.
Dasyurids are just as prone to developing stereotypical behaviours as eutherian carnivores. Quolls and devils in particular are prone to stereotypic pacing. Free-ranging dasyurids spend a significant amount of time searching for food. If feeding routines are not varied, animals pace in anticipation of being fed just prior to their usual feeding time, spend a short time eating the meal then spend the remainder of their time sleeping or pacing. It is therefore important that the animal’s housing and husbandry routines provide not only for their physical needs but also their behavioural needs. Enclosures should be interesting and varied with natural materials such as leaf litter, mulch, bark, branches and hollow logs. Enrichment activities should be provided and aimed at encouraging natural behaviours and stimulating senses. These may include the use of different feeding methods, varying and randomising feeding times and providing non-food related enrichment. These may include the use of bungee feeders, random scatter feeds of insects, fruits and nuts, hiding feed in the substrate and exhibit furniture, hanging papier mache balls filled with food and frozen blocks of blood. Prey species and other scents are very stimulating to dasyurids and these can be provided in the form of macropod faeces scattered in the exhibit, use of browse or nesting material from glider or possum enclosures or aromatherapy oils. Observational data has shown that macropod faeces provide the greatest stimulation for Tasmanian devils (Schaap 2002). The risk of disease (e.g. mycobacteriosis) transmission when using macropod faeces must always be carefully considered.
4.2 Individual marking and identification techniques
Dasyurids over 10 g can be permanently identified by inserting a passive integrated transporter or microchip SC between the scapulae. Tissue glue is used to seal the entry wound to prevent the microchip from tracking out along the injection site. Ear notching has been used in smaller individuals, and ear tattoos are another option.
Small dasyurids can be transported short distances in pillowcases or other cloth bags. Alternatively, they can be placed in a nest box with the entrance plugged up. Larger species can be moved in plastic crates designed for holding cats and small dogs. For longer-distance transport they must be placed in a wooden box with nesting material, a water bottle to prevent spillage and a small dish of food (Fig. 10.3).
All dasyurids are carnivorous or insectivorous although antechinus, phascogales and quolls will eat some plant material and nectar. Small dasyurids are generalists and opportunists consuming predominantly arthropods such as beetles, spiders and ants, the size of the prey increasing with the size of the predator. Large dasyurids consume mostly vertebrates, prey size again varying with predator size. Tasmanian devils eat wallabies, wombats and a significant amount of carrion including introduced species such as rabbits and sheep. Spot-tailed quolls consume mostly rabbits and possums, while eastern quolls ingest small mammals, birds, lizards, insects and fruit such as blackberries. Western quolls (D. geoffroii) eat small mammals, lizards, frogs, insects and freshwater crustaceans (Hume 1999). Northern quolls consume large quantities of fruit, their favourite being the wild grape (Ampelocissus asetosa) and they enjoy nectar from eucalypt and grevillea flowers (Oakwood 2004).
Figure 10.3 Transport box for a Tasmanian devil.
In captivity small dasyurids such as planigales, dunnarts, antechinus, phascogales and kowaris have been successfully maintained on a mixed diet containing dog chow, hard-boiled eggs, cheese, day-old chicks and mice. This can be supplemented with assorted invertebrates such as mealworms, earthworms, fly pupae, crickets and moths, depending on what is available. A commercial insectivore mix can also be used, and pollen grains and blossoms can be fed when available. Tasmanian devils and quolls are fed dog chow and whole animals such as guinea pigs, rabbits, rats, mice, pilchards and day-old chicks (Table 10.2). Quoll diets can also be supplemented with mixed invertebrates and they may enjoy a small amount of soft fruit such as bananas, grapes and melon.
Anorexic dasyurids may be tempted to eat using favourite food items or live food. If the problem is one of aggression, multiple feeding stations or the separation of warring individuals may be required. Alternatively, individual dasyurids that do not eat after being placed in a new environment may benefit from the inclusion of a companion.
4 day-old chicks (35 g), 1 egg (60–70 g)
½ guinea pig (150–200 g)
1 rabbit, wallaby, sheep piece (1600 g)
4 day-old chicks (35 g), 1 egg (60–70 g)
1 rat (250 g)
1 rat (250 g) or ½ adult chicken
½ day-old chick or mouse
20 g moist dog chow
1 g fly pupae
0.2 g pollen grains once/week
6 g egg and cheese 3–4 times/week
2 crickets 3–4 times/week
2 moths 3–4 times/week
6 g moist dog chow
10 g egg or cheese
1/8 day-old chick or mouse
1 g fly pupae
2 crickets 3–4 times/week
2 earthworms 1–2 times/week
2 moths 3–4 times/week
3 pollen grains once/week
Blossoms as available
Daily energy requirements for late lactation are double those for non-breeding females. For the eastern quoll to double its food intake it must consume half its body weight daily, while the antechinus needs to ingest more than its own body weight. If this cannot occur the female either draws on her own reserves and loses weight or selectively reduces her litter size by culling some of the young. To prevent this, lactating females should be fed 3–4 times maintenance.
Tasmanian devils and quolls tend to become obese and should be fed 5–10% of their body weight daily. Devils will benefit from a starve day once a week.
Metabolic bone disease has occurred in small dasyurids fed on a strict mutton diet. Affected animals had soft translucent bones. The problem was rectified by the addition of 1 tablespoon of calcium carbonate to 1 kg of meat. A laboratory colony of fat-tailed dunnarts died of iodine deficiency. Affected animals had enlarged thyroids containing follicles lined by a cuboidal to columnar epithelium that were devoid of colloid; iodine supplementation of 60 mg/d prevented mortalities (Obendorf 1993). If a dasyurid’s diet is varied and balanced there should be no need to supplement with vitamins or minerals. Dental disease is uncommon in dasyurids and may be associated with the practices of feeding whole prey items and insects. Obesity is also common; energy intake should be monitored and controlled if required and activity encouraged through behavioural enrichment.
6 CAPTURE AND RESTRAINT
6.1 Capture and physical restraint
Physical restraint is only used for minor procedures or to induce general anaesthesia as it will result in considerable struggling and attempts to bite. This will produce a minor degree of pain and inconvenience when caused by an antechinus or dunnart, and the larger members of the group can inflict severe injuries.
When restraining or transporting a dasyurid it is advantageous to place it in a bag. This can range from a small calico bag or pillowcase for smaller animals up to a large hessian sack for Tasmanian devils. Devils must be closely monitored as they can chew their way out of bags. Animals in bags tend to relax as outside stimuli and visual threats are removed. The chance of injury is decreased as they cannot lash out against solid objects.
Small dasyurids can be caught in their nest box or with an Elliott trap. They are gripped by the scruff of the neck and placed in a bag. Alternatively, they can be held firmly around the body. It is important not to clasp them too firmly, as suffocation is possible.
Figure 10.4 Capture of (a) a Tasmanian devil and (b) a spot-tailed quoll. Photo: Larry Vogelnest.
Larger dasyurids, such as quolls and devils, can be caught in a net or restrained by the tail and lowered into a bag. Devils and quolls can easily be held for short periods by the tail (Fig 10.4). To avoid injuring the tail it should be grasped toward its base. Some quolls are agile enough to turn and bite the handler. Dasyurids should not be carried long distances held only by the tail. Smaller dasyurids, such as antechinus, dunnarts and phascogales, should not be restrained by the tail, as severe degloving injuries and tail fractures can occur.
6.2 Chemical restraint
Most dasyurids are not prone to regurgitation under anaesthesia, but pre-anaesthetic fasting for 6–8 hr is recommended (Vogelnest 1999).
Sedation for transport is generally not required but very nervous animals may benefit from the administration of 1–2 mg/kg diazepam IM. Effects should be obvious after approximately 20 min.
Inhalation anaesthesia is the method of choice for dasyurids. If the animal can be manually restrained the safest way to induce general anaesthesia is via a non-rebreathing circuit (e.g. Ayre’s T-piece) and a mask. For animals in bags anaesthesia can be induced through the bag or by extracting the head and placing it in the mask. It is important to grasp quolls and devils very firmly behind the head, as they will attempt to pull back out of the mask and potentially bite the operator.
5% isoflurane delivered in oxygen at a flow rate of 200 mL/kg/min with a minimum of 1 L/min is used for induction. Maintenance of anaesthesia generally requires 2% isoflurane, but this varies between species and individuals. Tasmanian devils and quolls have a wide gape and are easily intubated for more prolonged procedures. If isoflurane is unavailable halothane is an acceptable substitute, but is not as safe and requires close monitoring.
Injectable agents can also be used if gaseous anaesthesia is not available. To induce general anaesthesia tiletamine/zolazepam can be administered at 7–10 mg/kg IM (Vogelnest 1999). The advantage of this combination is its low volume and rapid effect. However, relaxation is variable with hypersalivation and constant limb and jaw movement sometimes occurring in Tasmanian devils. Recoveries can also be prolonged, in excess of 6 hr in one devil (Holz 1992). Xylazine 4 mg/kg combined with ketamine 20 mg/kg IM provides light anaesthesia with better muscle relaxation (Vogelnest 1999). Although likely to be useful, there are no reports of ketamine or tiletamine/zolazepam and medetomidine combinations or alfaxalone being used in dasyurids.
7 CLINICAL PATHOLOGY
7.1 Haematology and biochemistry
7.1.1 Sample collection
Anaesthesia is usually required for successful venipuncture in dasyurids. The ventral coccygeal, femoral, medial metatarsal, lateral saphenous, cephalic and jugular veins are suitable for blood collection. Access to the ventral coccygeal vein is by inserting the needle perpendicular to the tail, in the ventral midline, and advancing it until the vertebrae are reached. Withdraw the needle slightly and blood should enter the needle hub. This vein is useful for smaller dasyurids. No more than 10% of total blood volume (approximately 1% of body weight) should be collected at any one time. Access to the femoral vein or artery is by directing the needle at the pulse felt in the inguinal region (Fig. 10.5). Arterial blood is often obtained and digital pressure is required to prevent haematoma formation. The medial metatarsal vein is a small vein running along the medial aspect of the hind leg. The cephalic vein is present on the dorsal surface of either fore leg. The lateral saphenous vien is on the lateral aspect of the tibia just proximal to the tarsal joint. The latter 2 veins are useful in Tasmanian devils and quolls. The jugular vein is suitable for blood sampling in all dasyurids (Fig. 10.6). It is best accessed with the animal lying in dorsal recumbency with the neck extended. It can be found along the length of the neck in larger species with access relatively easy just at the thoracic inlet. At this point the needle can be directed almost perpendicular to the skin (L Vogelnest pers. comm.). Blood collection from the periorbital sinus is not acceptable.
Figure 10.5 Femoral venipuncture in an eastern quoll. Photo: Taronga Zoo.
7.1.2 Reference ranges and interpretation
Dasyurids are born at an early stage of development and PY still have foetal haematological characteristics, e.g. fat-tailed dunnarts have 100% nucleated erythrocytes at 1 d of age decreasing to 15% by 4 d of age. Howell-Jolly bodies can be found in normal blood from eastern quolls, western quolls, fat-tailed dunnarts and stripe-faced dunnarts (S. macroura). Heinz bodies have been found in eastern quolls. Annular leucocytes occur in Tasmanian devils, eastern quolls and dunnarts. Western quolls tend to produce a lymphocytosis, rather than a neutrophilia, in response to inflammation (Clark & Boardman 2005). Brown antechinus erythrocytes produce high levels of lactate from glucose. Dasyurid haemoglobin has a low oxygen affinity and a high oxygen-carrying capacity (24 mL of oxygen in 100 mL of kowari blood compared with 20 mL of oxygen in 100 mL of blood for many placental mammals) (Hallam et al. 1995). Dasyurids also have a high haematocrit, large tidal volume and high ventilation perfusion ratio. This is consistent with smaller animals having a higher metabolic rate and greater oxygen demands. Dasyurid spleens contain areas of extramedullary haematopoiesis with megakaryocytes visible histologically. A range of protozoa can be found in dasyurid blood (see 9.3.4). For a complete review of dasyurid haematology see Clark (2004).
Figure 10.6 Jugular venipuncture in (a) a Tasmanian devil and (b) an eastern quoll. Photos: Taronga Zoo.
Tasmanian devils have high plasma levels of acid phosphatase. The reason is unknown. Highest levels occur in the reticulo-endothelial system and reproductive organs. The ratio of cortisol: corticosterone in the plasma is 10:1 in quolls and Tasmanian devils. Dasyurids have high normal blood urea levels compared with domestic mammals. The reason is unknown. Table 10.3 provides haematology and biochemistry values for various dasyurid species.
Dasyurids have relative lactose intolerance due to low levels of intestinal lactase and should be reared on low-lactose milk. In Tasmanian devils and eastern quolls solids, lipids, protein and calcium peak in late lactation, carbohydrates peak in mid lactation and iron peaks in early lactation. Di-Vetelact (Sharpe Laboratories), Biolac and Wombaroo are all satisfactory milk substitutes for dasyurids. Upon presentation the orphaned PY should be assessed for injuries, hydration status and hypothermia. It should only be hand-raised if it presents in good condition, does not have any injuries resulting in future permanent handicaps and can be released at maturity. After assessment it should be warmed up and, if there is a delay before delivery to the intended carer, given an electrolyte solution at 100–150 mL/kg/24 hr. Orphaned PY should be held in artificial pouches made from soft material such as wool with a cotton lining. Hand-rearing furless PY has a poor success rate as they are normally attached to the mother’s teat, have an extremely immature immune system, are heavily dependent on passive maternal immunity and are very susceptible to infection. Strict attention to hygiene and sterilisation of feeding utensils is important. Their skin must be treated regularly with an emollient such as sorbolene or lanolin to prevent it drying out and cracking. Feeding should be every 2 hr and the PY maintained at 34–36°C until well furred, when the temperature can be reduced to 30°C. Once fine fur has appeared feeding frequency can decrease to every 3–4 hr. Daily milk consumption varies from 10% to 20% of body weight. PY require stimulation after each feed to urinate and defecate. Rub the cloaca gently with a damp piece of cottonwool. Phascogales, antechinus and other small dasyurids are difficult to feed as they have small mouths. A very fine teat is required, or they may suckle from a fine paintbrush. Older animals may lap from the end of a syringe or eye ointment dispenser. Once the teeth have emerged and the young starts leaving the pouch, solid food such as chicken pieces and live mealworms and crickets should be offered. Live food is usually very popular. Feeding frequency can decrease to every 4–6 hr. Milk quantity should be gradually reduced and solid food increased until milk is totally eliminated from the diet. Animals for release must have minimal human contact to avoid imprinting, and access to natural prey items. Release should occur shortly before dusk and additional food may need to be provided until hunting skills are developed (Jackson 2003).
9.1 Dermatological diseases
9.1.1 Parasitic diseases
Demodex spp. have been reported from the brown antechinus, agile antechinus, spot-tailed quoll, southern dibbler (Pseudantechinus apicalis), red kaluta, northern quoll and hairy-footed dunnart (S. hirtipes) causing skin nodules, which represent a granulomatous dermatitis and folliculitis histologically (Fig. 10.7). In affected antechinus one to three solid nodules were found on the hind legs, head, tail base, cloaca or near the pouch. Nodules were filled with mites and had a honeycomb appearance on cut surface. Giant cells were present. Spontaneous regression occurred in two cases. Surgical removal in one case resulted in recurrence a month later. In quolls nodules were found on the feet and abdominal wall. Mites parasitised hair follicles causing hypertrophy and eventual destruction of the follicle, leading to a predominantly mononuclear cell infiltrate and ulceration. Unlike the antechinus, surgical excision was curative. In the dibblers nodules appeared on the face. Seven animals were treated 2–4 times with 0.1 mg/mL ivermectin diluted in propylene glycol and dabbed onto the lesions at 7 d intervals, resulting in resolution in five individuals (Nutting & Woolley 1965; Holz 1998; Eden et al. 2004; Desch & Holz 2006).
Table 10.3 Haematology and biochemistry reference ranges for selected dasyurids
Figure 10.7Demodex from an antechinus.
Sarcoptiform mites belonging to the genus Diabolicoptes and Satanicoptes have been found on large dasyurids, associated with alopecia, hyperkeratosis and erythema.
There are six species of ticks, from the genera Ixodes and Haemaphysalis, recorded on dasyurids. They include the paralysis tick, Ixodes holocyclus, which also transmits the filarioid Cercopithifilaria johnstoni. This nematode occurs in the subcutaneous tissues of Tasmanian devils. No clinical signs have been associated with any of the ticks.
There have been 32 species of fleas reported from dasyurids. Uropsylla tasmanica occurs on Tasmanian devils and quolls. The adults are found mainly on the scrotum, lower limbs, face and ears. They attach their eggs to the basal portion of hairs. After hatching, the larvae burrow into the skin and feed on the subcutaneous tissues of the host until pupation, causing irritation leading to the formation of pustules, self-trauma and hair loss (Fig. 10.8). Treatment is with topical parasiticides such as pyrethrin spray 1 mg diluted in 10 mL water, fipronil 5–10 mg/kg or selamectin 6 mg/kg. Changing nest material and washing nest boxes frequently helps decrease ectoparasite numbers (Obendorf 1993). One study found imidacloprid to be safe and effective at a dose of 10.4 mg/kg in eastern quolls and 26.3 mg/kg in fat-tailed dunnarts (Baker & Beveridge 2001). In situations where reintroduction of fleas into an environment is limited, lufenuron has been used successfully to control fleas (L Vogelnest pers. comm.).
Figure 10.8Uropsylla tasmanica infection in a spot-tailed quoll.
Dasyurid lice are all biting lice belonging to the genus Boopia.
Ophidascaris robertsi is a python ascarid whose large (up to 15 cm) larval stages have been found in the viscera and subcutaneous tissues of the brown antechinus, brush-tailed phascogale, quolls and dusky antechinus (Fig. 10.9). Plerocercoids of Spirometra erinacei (spargana) have been found subcutaneously in numerous dasyurid species.
9.1.2 Cutaneous mycobacteriosis
Cutaneous mycobacteriosis has been reported in spot-tailed quolls and Tasmanian devils. The causative agents are saprophytic mycobacteria such as Mycobacterium chitae, M. fortuitum, M. smegmatis and M. ulcerans. Lesions consist of single to multiple thickened areas of skin that range from focal plaques to abscesses with fistulous tracts. Histologically affected areas consist of a pyogranulomatous dermatitis containing acid-fast bacilli, neutrophils, mononuclear cells, giant cells, necrosis and mineralisation. Most commonly affected sites are the dorsal neck, thorax and axilla occurring secondary to bite wounds associated with breeding. Treatment is invariably unsuccessful but can be attempted using a combination of surgical debridement and prolonged treatment with antimicrobial drugs such as amikacin 3 mg/kg bid, enrofloxacin 2.5 mg/kg bid and rifabutin 20 mg/kg sid (Raymond et al. 2000). Euthanasia is generally recommended if cutaneous mycobacteriosis is diagnosed.
Figure 10.9Ophidascaris robertsi larvae in the thoracic cavity of a spot-tailed quoll. Photo ARWH.
9.1.3 Tasmanian devil facial tumour disease (DFTD)
DFTD was first recognised in Tasmania in 1997. None of the biologists trapping Tasmanian devils between 1964 and 1996 reported any lesions resembling DFTD (Hawkins et al. 2006). Tumours present as large solid soft tissue masses that ulcerate, first appearing on the head and/or neck regions (Fig. 10.10). The cut surface is firm, pale and slightly translucent with visible fibrous septa, often with a necrotic core. Histologically they form sub-epithelial expansile masses of round cells (8.08 ± 1.43 μm in diameter) with abundant eosinophilic cytoplasm and a high nuclear to cytoplasmic ratio (1:1.2) encased within a pseudocapsule. Mitotic figures range from zero to 12 and average four per high-power field. Inflammation is minimal, with only 7% of cases having lymphocytic infiltrates. Based on immunohistochemical stains the tumour appears to be an undifferentiated sarcoma of neuroendocrine origin that is locally aggressive and metastasises in 57% of cases to draining lymph nodes. In 41% of cases metastases are found further afield – 47% in the lung, 12% in the spleen, 6% on the heart, ovary and serosal surface of the rib and 5% in the kidney, mammary, pituitary and adrenal glands. Lymphocytes with a moderate to high mitotic index are commonly seen infiltrating other organs such as the liver. Transmission electron microscopic examination of tumour cells has not identified a viral cause (Loh et al. 2006a; Loh et al. 2006b).
Figure 10.10 Tasmanian devil facial tumour disease.
Tumours are rarely seen in animals less than 2 yr of age (17% of cases seen occurred in 2 yr olds, 52% in 3 yr olds, 26% in 4 yr olds and 5% in devils older than 4) with males and females equally represented. Once clinical, the course of DFTD is rapid with the tumour enlarging over the course of weeks. Death usually occurs within a few months. Mortality is 100%, mostly due to starvation as the tumour destroys facial bones and dental arcades. Mature adults are scarce in regions that have been affected for a long time, with most animals being <2 yr old. Devil numbers peaked at 150 000 in the mid 1990s but mean devil sightings fell by 41% from 1992–95 to 2002–05 as a result of DFTD (Hawkins et al. 2006).
After having first been observed in the north-east of Tasmania at Mount William National Park, the distribution of DFTD has progressively increased and affected devils are now found over much of the eastern half of Tasmania. There are two apparently unaffected areas, on the north-west and east coasts, surrounded by diseased populations (Hawkins et al. 2006).
Tasmanian devils have low genetic diversity with a karyotype of 14XX or 14XY. They differ from other dasyurids by having a pericentric inversion of chromosome 5. However, 4 of 100 devils examined had both inverted and non-inverted forms of chromosome 5. Because of the characteristic chromosomal rearrangement found in the cells of every tumour (all tumours examined lack both sex chromosomes, both chromosomes 2 and one chromosome 6) direct exposure to tumour cells is regarded as necessary for the development of DFTD but that alone is not sufficient for disease to occur. Damage to the skin or mucus membranes around the head and neck, as occurs with fighting, scratching and biting, is also required before DFTD can develop. It is noteworthy that lesions are rarely observed on other parts of the body that are also subject to trauma. One diseased animal had a pericentric inversion of chromosome 5 throughout its normal tissues, but not in the cells of the facial tumour. Because of the differences in chromosome 5 between the tumour and the animal, the tumour could not have developed from the animal’s own tissues but acted as an allograft (Pearse & Swift 2006). This provides solid evidence for the transmissibility of DFTD. It is possible, but not certain, that animals whose chromosome 5s are both of the non-inverted form might be resistant to development of the tumour.
Incubation period is unknown but one animal developed DFTD after 10 mo in captivity without apparent exposure to tumour cells during that time. To date, spot-tailed quolls and eastern quolls have not been diagnosed with the disease.
Currently there is no treatment. Management options are limited to attempting to separate diseased animals from disease-free susceptible animals. As the incubation period may be long and there is no preclinical diagnostic test, confidently identifying disease-free animals is difficult (AusVet 2005).
9.1.4 Miscellaneous conditions
Pedunculated papillomas of unknown aetiology have been described from the foot and head of quolls and Tasmanian devils. Lesions resembling epitrichial sweat gland cystomatosis have been described in a spot-tailed quoll (L Vogelnest pers. comm.; ARWH 2007 case number 5178). Many skin neoplasms have been reported in dasyurids (Table 10.4).
Dasyurids moult during or after the breeding season and animals may present with patchy fur loss. This is normal, and affected animals will regrow their fur over the following months. Aged dasyurids can also develop progressive fur loss, which will not regrow. Adult Tasmanian devils frequently have patchy alopecia, reddened skin, small skin wounds (particularly in wild animals and those kept in pairs), minor crusting skin lesions and occasionally pustules. They are frequently pruritic. Ectoparasites, trauma from bite wounds and pyoderma may be implicated in some cases, however, a cause is frequently inapparent (L Vogelnest pers. comm.). Multifocal to coalescing, exudative and crusting skin lesions, particularly affecting the hind quarters, are frequently reported in wild spot-tailed quolls (K Firestone pers. comm.). The cause of this condition is yet to be determined but is most likely the result of a combination of parasitic, environmental and social factors.
9.2 Gastrointestinal diseases
9.2.1 Gastrointestinal parasites
There are 23 species of trichostrongyles infecting dasyurids, mostly occurring in the small intestine with one, Peramelistrongylus skedastos, found in the stomach. Of the spiruroids, which utilise invertebrate intermediate hosts, Spirura aurangabadensis occurs in the oesophagus of antechinus, planigales and dunnarts, while Cyathospirura seurati, Cyathospirura dasyridis and Cyclicospirura heydoni occur in tumour-like nodules in the stomach of quolls (Munday 1988). Antechiniella suffodiax and Synhimantus australiensis are found in antechinus stomachs. They use arthropod intermediate hosts. A. suffodiax burrows into the stomach wall, producing fibrous nodules. Physaloptera sarcophili occurs in the stomach of Tasmanian devils and quolls and uses a coleopteran intermediate host. The filarioid nematode Sprattia capilliforme is found in the mesenteric and portal veins of the liver in northern quolls. Breinlia dasyuri occurs in the spot-tailed quoll. Capillaria rickardi is found in tunnels in the epithelium of the stomach and duodenum of antechinus. It can cause ulceration and haemorrhage. A Capillaria spp. has also been recognised histologically in the tongue of northern quolls. There was no associated inflammatory reaction. Trichinella pseudospiralis is found in spot-tailed quolls and Tasmanian devils. Larvae occur in the muscle and adults in the intestines. Anatrichosoma spp. occur in the paracloacal glands of antechinus. Baylisascaris tasmaniensis is a large ascarid (males 24–68 mm and females 26–128 mm) found in the stomach and small intestine of Tasmanian devils and quolls. It causes visceral granulomas in wombats and pademelons, the intermediate hosts. Ophidascaris robertsi is a large (up to 150 mm) python ascarid that forms liver cysts in dasyurids. Larvae may also be found in the abdominal cavity of dasyurids (Beveridge & Spratt 2003) (Fig 10.9).
Tasmanian devil X 9
Eastern quoll X 3
Tiger quoll X 3
Kowari X 6
Common planigale X 2
Fat-tailed dunnart X 3
Brown antechinus X 1
Brush-tailed phascogale X 1
Red-tailed phascogale X 1
Tasmanian devil X 2
Eastern quoll X 1
Kowari X 1
Brown antechinus X 1
Brush-tailed phascogale X 2
Tasmanian devil X 2
Northern quoll X 2
Fat-tailed dunnart X 1
Fat-tailed false antechinus X 5
Dibbler X 1
Sandstone false antechinus X 1
Tasmanian devil X 1
Tiger quoll X 1
Northern quoll X 1
Kowari X 2
Fat-tailed dunnart X 3
Tasmanian devil X 2
Eastern quoll X 1
Tiger quoll X 1
Northern quoll X 1
Tasmanian devil X 1
Eastern quoll X 6
Tiger quoll X 3
Kowari X 2
Common planigale X 1