Marsupials Flashcards
What are the seven orders of marsupials and what groups are in them?
Where are marsupials located geographically?
- Taxonomy
- Australasia and Americas
- Majority in Australia, New Guinea, nearby islands
- One species in NA - Opossum
- Subclass Marsupialia
- Sever orders
- Didelphimorphia – opossums, 92 spp
- Microbiotheria (Monito del Monte)
- Dasyuromorphia (dasyurids – 71 spp).
- Peramelemorphia (bandicoots and bilby, 21 spp)
- Notoryctemorphia (marsupial moles, 2 spp)
- Diprodontia (koala, wombats, possums, gliders, macropods – 140 spp).
- Sever orders
- Australasia and Americas
Describe the musculoskeletal anatomy of marsupials.
What species have an ossified patella?
What are the epipubic bones?
Syndactyly occurs in which species?
What is unique about the atlanto-occipital articulation of macropods? What is a potential downside of that?
What is unique about the macropod symphysis?
- Musculoskeletal system
- Only bandicoots and bilby have ossified patellas
- Epipubic bones extend from cranial pubis
- Paired clavicles in all spp except bandicoots and bilby
- Second and third digits on hindfoot are syndactylus except for opossums, dasyurids, and the numbat.
- Macropods
- Atlanto-occipital articulation is highly flexible, allows muzzle to remain horizontal whether neck is horizontal or vertical.
- Weakness at the articulation may result in fractures at that site.
- Mandibular symphysis of kangaroos and wallabies unfused and flexible.
- Banded hare-wallable, bettongs, and potoroos it is fused.
Describe marsupial dentition?
What is unique about their deciduous teeth?
What are the two main groups? How do these groups reflect their natural history?
What species exhibit molar progression? What other taxa do this?
What is unique about koala dentition?
What is the dental formula of marsupials?
- Dentition
- Deciduous teeth apart from the third PM degenerate before eruption.
- Two broad groups
- Polyprotodonts (many incisors) – dasyurids, numbat, opossums, marsupial moles, bandicoots, bilby.
- Majority carnivorous or omnivorous.
- Diprodonts (two lower incisors) – Macropods, koala, wombats, possums, gliders.
- Majority are herbivorous.
- Wombats are the only diprodont marsupials with one pair of upper incisors and the only marsupials with hypsodont teeth (rootless, ever growing).
- Some spp of macropods (genus Macropus) exhibit molar progression.
- Molars erupt caudally and migrate forward throughout life.
- Cheek teeth shed from font as they wear out, replaced by next tooth.
- Unique to macropods, elephants, and manatees.
- Koala – occlusal surfaces of molars wear continuously and degree of tooth wear important for plane of nutrition.
- Polyprotodonts (many incisors) – dasyurids, numbat, opossums, marsupial moles, bandicoots, bilby.
- The basic dental formula for marsupials is I 5/4; C 1/1; P 3/3; M 4/4 but this now exists only in the Didelphidae, with the incisors of extant Australian marsupials not exceeding I 5/3.
Describe the gastrointestinal anatomy and physiology of marsupials.
What is merycism?
What is the fermentation strategy of macropods? What about koalas, wombats, possums, and gliders?
What is unique about the koala cecum?
Do any marsupials exhibit coprophagy?
What type of GI do dasyurids, bandicoots and bilbies have?
How does the GI system connect with the urinary or reproductive systems?
- Gastrointestinal system
- Macropods – foregut fermenters
- Merycism – Occasional regurgitation into mouth, involves rather violent heaving motion with vigorous movements of the forelimbs and thorax.
- Bolus not generally rechewed as in ruminants and is quickly reswallowed.
- Merycism – Occasional regurgitation into mouth, involves rather violent heaving motion with vigorous movements of the forelimbs and thorax.
- Koalas, wombats, most possums and gliders – monogastric, hindgut fermenters.
- Koalas – largest cecum relative to body size among all known mammals.
- Wombat SI is short, colon large and sacculated, cecum vestigial.
- Possums and gliders – expanded cecum is main site for fermentation in ost spp.
- Striped possum and honey possum – simple SI, lack plant material in diets.
- Coprophagy in some spp of ringtail possums.
- Dasyurids, bandicoots, bilby have simple GIT.
- Females – Urogenital sinus (urethra opens into), together with the rectum opens into a common vestibule (cloaca).
- Males – Penis lies within the common vestibule.
- Urogenital openings ventral to the rectum.
- Macropods – foregut fermenters
Describe the anatomy and physiology of marsupial skin.
What species lack a pouch?
Do males have teats? How does teat number vary across species?
Where is their skin thinnest and thickest?
What is unique about glider skin?
- Skin
- Many spp of dasyurids, opossums, numbat lack a pouch.
- Som spp temporary pouch from folds of skin during lactation.
- Males lack teats.
- Female teat number varies.
- 2 koala.
- 2 wombat.
- 4 macropods, numbat
- 4-12 in dasyurids
- 2-6 in possums and gliders
- 6-8 in bandicoots, bilby
- 4-13 in opossums.
- Cutaneous glands have various functions.
- Thin skin, especially inner surfaces of forelimb, where vascularity of SQ is significantly increased.
- Wombat skin thicker compared t others, inelastic.
- Sacral plate on the rump that is rigid.
- Gliders distinguished from possums by presence of a gliding membrane extending from hindlimb to forelimb.
Describe the sensory anatomy of marsupials.
What is their field of vision like?
What pupil shapes exist in marsupials?
Describe the fundic anatomy of macropods, koalas, and dasyurids.
- Sensory systems
- Wide field of peripheral vision with binocular vision for precise close vision.
- Good day and night vision.
- Still have difficulty navifating barriers that are not solid when alarmed and fleeing.
- Iris is thick and brown, pupil circular and ilated easily with tropicamide.
- Fundus heavily pigmented dark brown ventrally.
- Some animals have choroidal vessels visible through the pigment.
- Optic disk at the junction between these two zones, well vascularized.
- Retinal vessels not prominent.
- All macropods have persistent hyaloid vessels (tuft arising from center of optic disk and extending toward the posterior lens capsule). Usually not easily visualized but may be seen moving within vitreous.
- Kangaroos – myelination of then erve fiber layer may be seen extending from around the optic disc.
- Lateral and medial.
- Koala – small, spherical, frontally palced eyes.
- Relatively large corea.
- Tapetum across retina above optic disc.
- Mean IOP 24.2+/- 6 mmHg.
- Iris brown.
- Pupil vertically oriented slit.
- Lacrimal puncta slitlike openings inside the lid edges near medial canthus.
- Dasyurids have a vascular retina.
- Arteries do not branch but form discrete capillary loops.
Describe the immune system of marsupials.
How does the immune system of pouch young develop?
How is passive immunity provided? How long does it last?
What lymp structures are palpable in healthy marsupials?
- Immune system
- No lymphoid tissue is present at birth, neonate is not immunocompetent.
- Mos tspp reach immune system maturation at time of first release from the teat about half way through pouch life.
- Passive transfer of material Ab throughout lacrtation.
- Ab are absorbd unchanged across GI epithelium of pouch young.
- Passive immunity is short lived most maternal Ab lost about 4 wks after separation from the mother, with young only protected buy an underdeveloped active immune system.
- Secretions from pouch epithelium and MP in marsupial milk may contribute to immunologic protection of pouch young.
- Thymi are firm, bulging structures on ventral neck.
- Regress by sexual maturity.
- Superficial LN not palpable in healthy macropods.
- Superficial inguinal, axillary, rostral mandibular, mandibular, and facial LN are palpable in koalas.
- Popliteal and subiliac LN are absent.
Describe the reproductive anatomy of marsupials.
What type of placentation do they have (generally speaking)?
Describe the anatomy of the female urogenital tract.
Describe the route the fetus takes during parturition.
How does the median vagina change after the first parturition in most species?
Describe male marsupial reproductive anatomy.
What accessary sex glands are present?
What marsupials produce seminal plugs?
- Reproductive system
- Diffuse, epitheliochorial choriovitelline placenta.
- Bandicoots – diffuse placenta with both choriovitelline and chorioallantoic contributions.
- Female reproductive anatomy
- Each of the paired lateral uteri opens into a vaginal cul de sac through a cervix.
- Paired lateral vaginae both open separately into the urogenital sinus at level of urethral opening, separated along the length by soft tissue median septum.
- During parturition, fetus tunnels through this septal tissue for form a median vagina.
- In most marsupials, median vagina closes rapidly after fetus passes and then reforms with each subsequent parturition.
- In most macropods, opossums, and honey possuym, the med vagina becomes epithelialized after first parturition and remains patent as permanent median vag.
- Male repro anatomy
- Scrotum is pendulous, pedunculated (other than wombats), and pre penile.
- Strong cremast muscle retracts scrotal contents against the body.
- Accessory sex glands include a large disseminate prostate and one or more pairs of bulbourethral glands.
- No seiminal vesicles or ampullae.
- Some spp the prostate is easily palpated in the abdomen of breeding males.
- Macropodidae are the only marsupials to produce semen.
- Coagulates to form a seminal plug in the female after ejaculation.
- May be seen protruding from the female common vestibule.
Describe the urinary anatomy of marsupials.
What is the path of the ureters from kidney to bladder?
Why is urinary bladder surgery difficult?
Why is urinary catheterization of males difficult?
- Urinary system
- Unique to marsupials – Path of ureters from kidney to bladder.
- Ureters pass between median and lateral vaginae on each side.
- Surgical procedures on females difficult.
- Macropods, koala and wombats, bladder is intrapelvic when not distended.
- Ureters pass between median and lateral vaginae on each side.
- Urethra of male has paired valvelike cusps proximal to the external orifice.
- Similar cusps distal to the urinary bladder sphincter. Mkes cath difficult.
- Koalas – two regions of the male urethra may potentially impede the cath.
- First is a narrowing of the lumen and some mucosal irregularity in the vicinity of the openings of the bulbourethral glands.
- Second is the prostatic sinus, groove on either side of the urethral crest distal to the neck of the bladder.
- Unique to marsupials – Path of ureters from kidney to bladder.
Describe the metabolism and thermoregulatory strategies of marsupials.
What type of adipose tissue do they have?
What are the two types of torpor in marsupials? Which species experience which type?
At what point can pouch young thermoregulate?
How does marsupial metabolism compare to other mammals? What species have higher metabolic rates compared to other marsupials?
How do marsupials regulate their body temperature?
- Metabolism and thermoregulation
- No brown adipose.
- Two types of torpor in some spp.
- Shallow daily torpor – temp drops to 11C-28C lasts 2-20 hours – opossums, dasyurids, small possums, numbat and marsupial moles.
- Deep prolonged torpor (hibernation) – body temp drops to 1-6 deg Cm lasts 1-3 wks in pygmy possums, feathertail glider, monito del monte.
- Cannot thermoregulate until about half way through pouch life.
- Metabolism is lower than other mammals.
- Macropods at 25% and koala and hair nosed wombats at 44%.
- Basal metabolic rates highest in the small insectivorous dasyurids, but rates for other dasyurids less than half of other carnivores.
- All wombats have extremely low req of energy, protein, and water.
- Thyroid hormones in plasma in wombats lowest recorded for any mammal.
- Koalas and hairy nosed wombats rarely drink fluids.
- Thermoregulation by evaporative mechanisms – panting, seating, licking.
- Unique kangaroos – sweating stops as soon as exercise stops despite body temp.
- A method of evaporative heat loss by spreading saliva on forearms is common in macropods that have undergone exertion or anxiety.
- Panting is major means of evap cooling in the koala.
- Wombats more tolerant of cold than heat, cannot sweat.
- Use postural thermoreg or salivation on forelegs and hest to air cooling.
- Dasyurids do not sweat, cope with heat by licking and panting to increase evap cooling.
What are the four types of marsupial placentation?
Give examples of groups of marsupials with each type.
- 4 types of marsupial placentas
- Complete absence of allantois as a placental organ; allantois used only for excretion. All nutrients passed through a well vascularized yolk sac (Maceopodidae, phalngeridae, didelphidae)
- As above but the allantois approaches the chorion, although it does not fuse with it and retreats again during development (eastern quoll and dunnarts, other Dasyurids unknown)
- The allantois fuses with the chorion to form a chorioallantoic placenta but the yolk sac remains well-developed and is the main organ for exchange. (Phascolarctidae, Vombatidae);
- The allantoic placenta is the main organ of exchange but a well-developed choriovitelline placenta remains. The chorioallantoic placenta forms a discoid placenta that is firmly attached to the uterine wall and there is a long and thick umbilical cord (Peramelidae).
Describe the postnatal development of marsupials.
How does milk composition change over time?
Describe the lung development of neonatal macropods.
What is the primary function of the liver in neonatal macropods?
How is infection prevented in the nonsterile environment of the pouch?
● Normal Postnatal Development
o Neonatal macropods lack functioning adaptive immune system and weigh < 1 gram.
o After birth they crawl from cloaca to the pouch, continue to develop within a nonsterile environment.
o Suckling is continuous initially, becomes progressively intermittent after first third of pouch life.
o Milk composition changes dramatically with lipids, protein, and energy content increasing over time and carbohydrates decreasing at the point of pouch emergence.
o Newborn macropods – cutaneous respiration and simple lungs capable of gas exchange.
▪ Lungs composed of short branching airways that terminate in large saccules.
▪ Development of lungs is generally slow, saccules become subdivided by septal crests and decrease in size.
▪ At birth, liver is actively hematopoietic, produces the erythrocytic, granulocytic, leukocytic cell lineages.
▪ Throughout pouch life the hematopoiesis declines in the liver and BM takes over.
▪ Hemoglobin of pouch lung adapted to lower O2 and higher CO2 concentrations than ambient levels.
▪ Renal function is limited and compensated for by continuous oral intake of milk.
▪ Gastric grehlin secretion is important for regulating appetite shortly after bith.
▪ Pouch contains a broad range of gram positive and negative bacterias.
▪ Immune compounds in milk, prenatal transfer of immunoglobulins, antimicrobial compounds sereted in the pouch, chemical and mechanical cleaning of the pouch and pouch young.
▪ Paired thymus play important role in maturation of T cells and CMI.
▪ Pouch young able to synthesize antimicrobial peptides soon after birth.
Describe the proper nutrition of marsupials.
What are some common nutritional issues?
● Nutrition
o Most marsupials low metabolic rate and lower maintenance req for energy, protein, water, and other nutrients.
o Captivity often fed in excess and diets of low fiber that result in obesity and GI/dental dz.
o Energy intake should be monitored and controlled, activity encouraged.
o Small macropods should be supplemented with vit E.
▪ Prone to weakness and wasting of HL leading to paralysis and death.
● Myopathy.
● Stress, overcrowding may increase vit E requirements.
● This syndrome not only linked to diet, probs multifactorial.
Describe the hand rearing of marsupials.
Describe the differences in marsupial milk that make it challenging to find a suitable replacer.
How does the volume drank differ between mother reared and hand reared pouch young?
What effect does lactose have on pouch young?
Describe the weaning process for proper GI function.
o Hand rearing
▪ Requires detailed understanding of neonatal development and physiology, unique pouch environment, maternal care, passive immunity, development of immune system, amd milk composition.
▪ Major challenges simulating the pouch environment and functions.
● Also finding appropriate milk substitute.
● Minimizing exposure to pathogen.
● Milk of marsupials must support pouch young from embryonic state at birth until independence.
o Composition changes profoundly during course of lactation.
o Calcium, P, Na, and K also changes with lactation time.
o Milk very low in lactose, oligosaccharides predominant carbs for most of lactation.
o Transport of sugars into the intestinal mucosal cells relatively slow process.
o Mother-reared PY drink small volumes frequently.
o Hand reared PY fed larger volumes less freq.
o When hand reared PY fed milk containing lactose, the capacity of mechanism for transport of sugars into cell exceeded, unabsorbed lactose accumulates within intestinal lumen, increases osmolality of gut contents and results in watery diarrhea, dehydration, malabsorption, malnutrition, stunted growth.
o Oligosaccharides significantly larger than lactose and exert a lower osmotic effect.
▪ Numerous milk formulas have been used.
● Critical factors – Low lactose content, mirror changing composition of natural milk from early to late lactation.
● Weaning process – herbivores require inoculation of gut with appropriate bacteria. Hand reared koalas that have not consumed pap must be fed natural pap or substitute.
● Macropod and wombat young should be given access to fresh feces from healthy adults or mixed with water or formula, fed as slurry.
Describe marsupial reproduction - what are the various phases?
What are the five marsupial reproductive strategies and what species exhibit them?
● Reproduction
o In general – Brief gestation, birth of altricial young, extended and sophisticated lactational phase, significant portion fo which is spent in the pouch.
o Unlike other mammals, in all marsupials – conception does not interrupt the estrous cycle, but lactation does.
▪ 5 basic marsupial reproductive strategies:
▪ 1 – Possums, mountain pygmy possum, gliders, dasyurids, opossums are polyovular and polyestrous, with a gestation period shorter than the estrous cycle.
● Postpartum estrus and ovulation are suppressed during lactation.
▪ 2 – Bandicoots and bilbies are polyestrous and polyovular, with an ultra-short gestation period.
▪ 3 – Macropods are monovular and polyestrous, with a gestation period of similar lngth to the estrous cycle.
● Postpartum estrus and ovulation occur.
● During lactation, if fert has occurred, embryo remains as a blastocyst in embryonic diapause, except in western gray kangaroo, Lumholtz tree kangaroo, and musky rat kangaroo.
o Maintained by the sucking stimulus of the PY,
o Eastern gray kangaroo, parma, and whiptail wallaby – postpartum estrus does not occur, but females may come into estrus and mate when PY is older.
▪ 4 – Honey possum and pygmy possums (except the pygmy possum) – polyestrous and polyovular, with prolonged gestation and embryonic diapause.
▪ 5 – Koala and wombat are polyestrous and monovular, gestation period shorter than estrous cycle.
● In koala, ovulation is induced by copulation.
How can the reproductive success of marsupials be enhanced?
How does cross fostering work?
What are some difficulties with it?
How does milk composition change with the addition of a donor young?
o Enhancing reproduction.
▪ Semen collection, cryopreservation, induced superovulation, artificial insemination, ooyte and ambryo harvesting, and in vitro fert have been carried out in various spp.
▪ Best success probably koalas.
▪ Cross fostering has been successful in macropods.
● Potential to dramatically increase the reproductive rate.
● Rearing of young by a surrogate mother of a different taxon.
● Alternative for euthanasia of very small unfurred orphans of threatened spp.
● Factors implicated in successful cross-fostering attempts:
o Relative size of donor and surrogate females
o Size of pouch young at weaning.
o Differences in length of pouch life between spp.
o Size differences between the donor young and those of the surrogate spp at transfer.
● Females regulate milk composition and production irrespective of pouch young age.
o Transfer of donor young to species with more immature or advanced mammary glands will result in slowing or acceleration of growth and development and duration of pouch life.
o If the joey can be raised to age at which hand-rearing can start, considered successful.
Describe the lesions associated with oxalate nephrosis. Is this a toxic or metabolic disease?
What is the toxic principle of Phalaris grasses? What clinical signs occur in kanagaroos? What are the associated clinical signs?
What are the lesions associated with fluorosis in kangaroos?
What are the lesions associated with aluminum toxicity in koalas?
Metabolic
● Oxalate nephrosis
o Reported in koala, potoroo, wallaby, and scaly tailed possum
Tubular loss and dilatation, cortical fibrosis, glomerular atrophy, crystal associated inflammation
o Cause is poorly understood, can be an incidental finding or can cause significant nephrosis and renal failure
o Unlikely to be dietary, more likely genetic and due to inbreeding
Toxic
● Phalaris spp has caused neurotoxicity in kangaroos that have grazed on it
o Toxic compound is bufotenine
o Alkaloid that is structurally similar to serotonin
o Causes ataxia, wide vased stance, hypermetria and muscle tremors
o Gross lesions – green discoloration of the grey matter
● Fluorosis
o Reported in a group of gray kangaroos near a fluoride-emitting aluminum smelter
o Caused large exostoses over the diaphysis of longbones
o Also DJD and synovial hyperplasia
● Aluminum toxicity
o Implicated in renal failure in free ranging koalas
o Pathogenesis not confirmed but suspect dietary
Describe the degenerative changes that commonly occur in marsupials.
What type of cardiomyopathies commonly occur in North American opossums? How early can they occur?
What macropod species is commonly affected by idiopathic hypertenstion? What are the lesions?
What are the most common lesions from trauma in macropods?
Age related/degenerative
● Dilated and hypertrophic cardiomyopathies are seen in north American opposums, related to obesity - as early as 2 years of age (potentially obesity related)
● Idiopathic hypertension in gray kangaroos - arteriolar hypertrophy in multiple organs, multifocal retinal detachment
● Trauma
o Atlanto occipital joint of macropods is unusually mobile and predisposes them to cervical dislocation
o Facial and hepatic trauma also common from fighting
o Capture myopathy common in macropods
Describe the noninfectious inflammatory diseases of marsupials.
What marsupial species is particularly susceptible to these types of diseases?
What are the lesions associated with nonsuppurative meningoencephalitis in that species?
What about swollen paw syndrome and exudative dermatitis? Are other species affected? What risk factors exist for this disease?
Idiopathi progressive rrenal disease occurs in what marsupial species? How are the kidney lesions different from CKD?
Inflammatory non-infectious
● Nonsuppurative meningoencephalitis
o Common in brushtail possums in Australia
o A viral etiology (nidovirus) produces wobbly possum disease of brushtails in NZ but this has not been found in the Australian ones
o Multifocal areas of hemorrhage and a malacia, nonsuppurative inflammatory cell cuffing, fibrinoid vascular necrosis of the meninges and parenchyma
o Retinal atrophy also commonly occurs
● Swollen paw syndrome
o Seen in ringtail possums and less commonly in brushtail possums
o Etiology unknown but suspected to involve avascular necrosis
o Edema of the feet, especially forefeet, progressing to gangrene
o Ulceration and exudative dermatitis and necrosis of the ears, nose and tail tip can also occur
● Exudative dermatitis
o Brush tailed possums
o Widespread alopecia, exudation, crusting, and ulceration of skin
o Most common on rump but also face, limbs, other locations
o Anecdotally more common in males and in warm/humid weather
o Possible relationship to stress, fight wounds, or maceration of skin
o Facial necrosis may represent a different syndrome and is often more acute and severe
● Rump wear
o Brush tailed possums
o Breakage of fur over rump, minimal damage to skin
o Etiology unknown
● Idiopathic progressive renal disease
o Common in mountain pygmy possums
o Older animals, like CKD, renal tubular degeneration and lymphoplasmacytic infiltration
o Often have multisystemic metastatic mineralization
What are the clinical signs associated wtih macropod herpesviruses?
What are the various strains?
What are the inclusion bodies associated with these diseases?
● Macropod herpesvirus 1 (MaHV-1)
o Alphaherpesvirus
o Sudden death and rhinitis, conjunctivitis, pneumonia, cloacal ulceration, and variable splenic, pulmonic, and hepatic necrosis with intranuclear inclusion bodies in captive parma wallabies
● MaHV-3
o Gammaherpesvirus
o Respiratory disease in a group of free ranging eastern gray kangaroos
● MaHV-4
o Alphaherpesvirus
o Respiratory and neuro disease in a free living eastern gray kangaroo
● Cytomegalic inclusions without associated inflammation or apparent impact have been described in the prostate of antechinus and phascogale and renal tubular epithelium of bettongs, platypus, and pygmy possums
o Thought to be herpesviral in morphology but no viral particles observed yet
Pox lesions are common in what marsupials?
What species has neoplastic transformation from papilloma viruses? Which ones? What cancers develop?
● Poxviral lesions
o Most commonly reported in macropods
o Typical exophytic, hyperkeratotic cutaneous lesions with eosinophilic inclusion bodies
● Bandicoot papillomatosis and carcinomatosis virus 1 (BPCV 1) and BPCV2
o Associated with papillomatous and carcinomatous lesions in wester barred and southern brown bandicoot
o This disease is an impediment to species recovery efforts
o The viruses are genetically intermediate between papillomaviridae and polyomaviridae
o Induce a spectrum of cutaneous and mucocutaneous lesions
o Lesions classified as epithelial hyperplasia, carcinoma in situ, or SCC
o Carcinomatous lesions can metastasize
Marsupials are subclinical reservoirs or amplifications hosts of what arboviruses?
What is the cause of wobbly possum disease? What fatal lesions does it produce? Where are most lesions foudn on necropsy? What type of inflammation is found in these lesions?
RNA viruses
● Arboviruses
o Many endemic to Australia that cause dz in humans but marsupials are subclinical reservoirs or amplification hosts
o Examples of these viruses are Ross River Virus, Barmah Forest Virus, Murray Valley Encephalitis Virus and the Kunjan strain of WNV
Wobbly Possum disease
o Fatal disease of brushtail possums in NZ
o Caused by a novel nidovirus
o Nonsuppurative encephalitis and myocarditis
o Most lesions in liver, spleen, heart, brain, meninges, and kidneys
o Lymphocytic and plasma cell infiltrates in these organs
What viruses cause chorioretinitis in kangaroos?
What species of kangaroos are commonly affected?
How is this disease transmitted?
What are the clinical signs of this disease?
What lesions may be appreciated on fundic examination?
How is this disease diagnosed?
Eyes should be fixed in what preservative for histopathology?
How is this disease treated and controlled?
Fowler 7 Ch 51 - Viral Chorioretinitis of Kangaroos
- 1990 – Many blind kangaroos observed along the Darling River in webersn New South Wales between April and July 1994
- March thru June 1995- the disease reappeared and extended into NW Victoria and SE South Australia
- Dec 1995 thru April 1996- kangaroos in southern Western Australia also affected
- Outbreak of blindness in NW Victoria in 1975 retrospectively confirmed as viral chorioretinitis by PCR
Natural Hosts:
· Most common in western grey kangaroos (Macropus fulginosis)
· Also detected in eastern grey kangaroos (M. giganteus), red kangaroos (M. rufa), and euros (M. robustus)
· Captive red-necked wallabies (M. rufogriseus) and swamp wallabies (Wallabia bicolour) in affected areas had positive serologic results to two obriviruses, but no clinical signs.
· Sheep from affected areas also seropositive, but no clinical signs
Cause:
· Two orbiviruses implicated: Wallal and Warrengo viruses
Epidemiology
· Transmitted by biting midges (Culicoides austropalpalis, C. dycei, and C. marksi)
· Other insects, especially mosquitoes, no not appear to be involved
· C. austropalpalis is known to prefer feeding on bird, avian involvement in maintenance and transmission of virus in nature is unclear.
· 1995-50% to 85% of kangaroos tested in affected area seropositive to both viruses
o Associated prevalence of blindness ranged from less than 5% to 50%
· Animals are viremic for less than 2 weeks, within several weeks of first infection, and weeks to months before clinical signs appear.
· No evidence of direct transmission from kangaroo to kangaroo
Clinical Signs and Diagnosis:
· Blind, altered gait, shorter and higher hops, hopping in circles, star gazing
· Any deaths appear to be secondary to blindness (malnutrition, injury, etc)
· Few external signs of eye disease
o Some have small focal retinal lesions with little or no clinical manifestations
o Many apparently normal kangaroos have lesions detected on pathology
o Changes in eye reflectivity when spotlighted at night can indicate early change
o Some individuals have accompanying anterior uveitis
§ Pupils may remain dilated and animal doesn’t squint in bright sunlight
· Increased rectal temp not a reliable indicator of viremia
- Ophthalmoscopic Examination:
- Normal fundus
- Has fine, short retinal vessels emanating from the optic disc
- Background color is a bland reddish brown (choroidal vasculature)
- **No Tapetum**
- Some have normal variation of pale area surrounding the optic disc
-
Acute lesions of active retinal and/or choroidal inflammation
- Progressive focal to extensive pale areas of the retina
- Some acutely affected animals may have anterior uneitis
- Chronic retinal lesions are hyperreflective, pigmented, and nonprogressive
- Normal fundus
- Laboratory Results:
- Histopathology:
-
Eyes should be collected into Bouin’s fixative within15 minutes of death
- One eye fixed whole, the other opened for virus isolation samples
- 10% formalin may give reasonable results
- Brain and optic nerve should also be collected in formalin
-
Eyes should be collected into Bouin’s fixative within15 minutes of death
-
Immunohistochemistry:
- Strong positives for only Wallal virus seen in degenerate retinas of acute experimental cases.
- Reaction was confined to the retina and absent from inflamed choroid, degenerate optic nerve, and all other tissues
- Electron Microscopy:
- 1-mm cutes of retina and underlying choroid should be collected with 15 minutes of death, fixed for 4 hours in 2.5% glutaraldehyde in phosphate buffered saline pH 7.5 (PBS).
- Icosahedral virus particles 65nm in diameter are associated with disrupted and degenerative photoreceptor cells and macrophages of affected retinas.
- Virus inclusion bodies and cytoplasmic virus-specific 30-nm diameter tubules may be seen in infected cultured cells.
- **Findings are characteristic of the genus Orbivirus** can be confirmed with immunogold labeling.
- Virus Isolation:
- Wallal and Warrego viruses isolated from acute, but not chronic, cases in BHK-21 cells, in primary retinal cell cultures, and in joey kidney and lung cells.
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PCR:
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PCR developed for variant and reference Wallal and Warrego viruses
- Can be used on fresh and fixed tissue
- Variant Wallal virus detected in eyes and brain collected at necropsy of affected kangaroos with eye lesions
- Warrego virus also detected in some wild animals
- Test can also be applied to insect samples (detected in 3 species of midges)
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PCR developed for variant and reference Wallal and Warrego viruses
- Serology:
- Seroconversion is widespread during outbreaks
- Hematology and Serum Biochemistry:
- No detectable changes on routine biochemistry attributable to this infection
- Further Diagnostic Considerations:
- Histopathologic lesions are pathognomonic in animals euthanized due to blindness during outbreaks in endemic areas of Australia.
- For isolated cases with similar pathology, PCR or immunoperoxidase testing should be used as confirmatory tests.
- Histopathology:
- Pathology and Pathogenesis:
- Principle lesions: retinitis and/or retinal degeneration and uveitis
- Retinal lesions vary in extent from small segmental lesions to involving the whole retina
- Acute cases: active retinal degeneration, necrotic retinal cells, neutrophils, gitter cells, protin rich exudates (Fig 51-1, pp. 392)
- Chronic cases: (> 1 month duration) segmental to extensive atrophic retinal remnants and few inflammatory cells (Fig 51-3, pp. 393)
- Uveitis: Infiltration with mononuclear cells, including prominent plasma cells, most severe in the choroid overlying the affected retina.
- Wallerian degeneration – secondary change resulting from loss of gangion cells from the retina, seen in optic nerves in acute cases, extends to optic tracts in chronic cases.
- Mild multifocal nonsuppurative encephalitis in some cases
- Eye lesions may be immunologically mediated- eye normally contains no lymphocytes and no antigen-processing macrophages.
- Is assumed that the initial infection of the eye is coincident with, or soon after the detectable viremia.
- Lymphocytes activated in the spleen in response to leakage of foreign antigen from the eye
- Takes at least one week to reach the eye to respond to antigenic stimuli leading to uveitis.
- Fundic changes not seen for at least another 2 weeks, suggests an immunologic pathogenesis for retinal damage.
- Macropod eye anatomy: the retina is more dependent on choroidal blood supply than in eutherian mammals, might be predisposed to retinal damage secondary to choroidal inflammation.
- Dual infection with both Wallal virus and Warrego virus may be necessary for serious eye lesions to occur.
- Sequential or dual infections and the enhancement of infection/severity of clinical disease by antibody investigated for dengue fever and Murray Valley encephalitis.
- Further studies needed to clarify the pathogenesis of viral chorioretinitis in macropods.
- Principle lesions: retinitis and/or retinal degeneration and uveitis
Treatment, Prevention, and Control:
· Local or systemic corticosteroid treatment may be helpful to reduce retinal damage in acute cases, assuming an immunologic pathogenesis, but is unproven.
· Currently no treatment is practical and retinal damage is permanent
· Not directly contagious, so unlikely to occur outside endemic areas of Australia
· Period of viremia is brief, and no carrier state is known, so risk of transport of infected macropods, except from affected areas during an outbreak, is minimal.
· A national arbovirus monitoring program in Australia plots the extent of arboviral spread on an annual basis to help guide decisions on risks of moving animals.
· A one-month quarantine of animals imported in insect-proof enclosures from endemic areas would remove any risk of introduction.
Orbiviral blindness caused by Wallal and/or Arrego viruses - Terio ZP
o Predominantly in kangaroos, also in wallaroos
o Outbreaks up to 30% of animals in a group effected
Sudden blindness, chorioretinitis and often encephalitis
Describe the sudden death syndrome of Tammar wallabies.
What is the scientific name of the Tammar wallaby?
What are the clinical signs associated with this syndrome?
What is the etiologic agent?
What are the histologic lesions associated with this disease?
● Tammar wallaby (Macropus eugenii) sudden death syndrome
o Only reported in zoos and research colonies
o Associated with an orbivirus of the Eubenagee serogroup
o Lethargy, head drop, ataxia, muscle tremors, death
o Gross findings: marked diffuse pulmonary and hepatic congestion and SQ edema with petechiae in the extremities
o Lymphocytolysis in lymphoid germinal centers is a consistent finding
o Multifocal hemorrhage also common
What are the clinical signs associated with Koala Retrovirus?
Where is it most prevalent?
What secondary diseases can occur?
● Koala retrovirus A (KoRV A)
o Gamma retrovirus
o Widespread in australia, 100% prevalence in queensland and new south wales where it is endogenous (inherited in the germ line)
o Variable prevalence elsewhere
o Possible etiologic agent of lymphoma and other lymphoid disorders but also likely multifactorial
o 3 subtypes (A, B, C)
o KoRVA is the only endogenous one, others are exogenous
o Some evidence to suggest an association between KoRVB infection and lymphoma or death of pouch young
What are the most common bacteria associated with lumpy jaw in macropods?
What are some predisposing factors leading to disease?
What are the typical lesions?
How is this disease managed?
● Necrobacillosis (lumpy jaw)
o Common in macropods
o Fusobacterium necrophorum most common but nocardia and others can also be involved
o Predisposing factors include overcrowding, stress, abrasive or soft forage, facial trauma, and GI parasites
o Edematous or bony swelling in the maxillary or mandibular area, usual with abscessation
o Hematogenous spread can cause visceral lesions
What mycobacteria species commonly affect macropods?
What marsupial species is an important wildlife reservoir in New Zealand?
What mycobacteria commonly causes ulcerative disease in koalas? What other species does this affect?
What are the typical lesions associated with mycobacteriosis in marsupials?
What management options are there?
● Mycobacteria
o Marsupials are highly susceptible
o Affected by various species including M. bovis, M ulcerans, M tuberculosis, M paratuberculosis, M avium, and others
o In New Zealand brushtail possums are a big reservoir for M bovis
o Reasons for susceptibility are unclear but likely related to their inflammatory response
o Lesions typically granulomatous or pyogranulomatous with giant cells often seen
o M ulcerans is the causative agent of Bairnsdale, Buruli, or Daintree ulcer in humans and can cause ulcerative dermatitis in koalas and brushtail possums which are proposed reservoirs for this pathogen
What marsupial species is commonly affected by Chlamydia?
What Chlamydia species cause the most issues?
How is it transmitted?
What clinical signs typically occur?
What lesions commonly occur?
How is this disease diagnosed?
How is it managed?
● Chlamydiosis
o Most common infectious disease of koalas
o C pecorum most common but can also get C pneumoniae
o C pecorum present in almost all free ranging koala populations, variable prevalence
o Transmitted sexually and likely during birth via monocytes in milk or ingestion of maternal cecal feces (pap-feeding)
o Majority of tissue damage caused by host’s response rather than by cell lysis from chlamydial replication
o Pyometra, metritis, cystitis, pyelonephritis are common
o Ovarian bursa may fill with fluid to form multiloculated cysts
o In males prostatitis and rarely orchitis have been described
o Hydroureter and hydronephrosis are common sequelae of fibrotic cystitis and ascending pyelonephritis
o Ocular lesions—from mild conjunctival hyperemia and edema to epithelial and lymphoid hyperplasia, thickened cauliflower-like nictitans
o Keratitis and blindness common
o Occasionally pneumonia can be seen
o Histology – villous epithelia hypertrophy and hyperplasia and squamous metaplasia
o Diagnosis by PCR or IHC
What marsupial species are commonly affected by Bordetella?
How is it transmitted?
What clinical signs are associated with Bordetella?
What lesions does it cause?
What treatment and preventatives are recommended?
● Bordetella bronchiseptica
o Can cause fatal outbreaks of respiratory disease in captive koalas
o Considered an opportunistic pathogen
o Causes suppurative bronchopneumonia
o Pasteurella multocida can also cause opportunistic bronchopneumonia or septicemia from cat bite wounds
What fungal infection commonly affects Koalas?
Is this fungus commonly found in healthy animals?
How is this organism transmitted?
What are the three different syndromes that can present with this disease?
What lesions are associated with this disease?
How is it treated?
Fungi
● Cryptococcosis (cryptococcus gattii)
o Koalas affected
o Saprophytic yeast, associated with a wide range of eucalyptus species
o Nasal mucosa of koalas commonly colonized without lesions
o Disease is rare but can cause respiratory disease (lower more common than upper)
o Dissemination to CNS common as well as invasion into local tissues
o Can cause neutrophilic to granulomatous inflammation
Toxoplasma gondii is a significant problem for marsupials.
How is it transmitted?
What species is particularly susceptible?
What are the typical clinical signs?
● Toxoplasma gondii
o Reported in many marsupials and monotremes
o Vertical transmission may occur or through oocyst ingestion via plants or soil contaminated with cat feces
o T gondii bradyzoites are common in muscle of sheep in Australia; if raw meet is fed to small dasyurids they can develop neuro signs and die due to encephalitis
o Significant cause of mortality in bandicoots, this species may be particularly susceptible
o Signs are species dependent but can include neuro signs, resp signs, diarrhea
o Tachyzoites are the most immunogenic life stage
Discuss macropod progressive periodontal disease.
What risk factors are associated with the development of MPPD?
What bacteria are commonly isolated in these cases?
How do lesions progress from early to advanced cases?
How is this disease diagnosed and manged?
Fowler 10 Chapter 101 Macropod Progressive Periodontal Disease (Lumpy Jaw)
Abstract/Intro
- Macropod progressive periodontal disease (MPPD, lumpy jaw) is a multifactorial progressive inflammatory and necrotizing polymicrobial disease associated with predominantly anaerobic opportunistic bacterial infection of the soft tissues and bony structures supporting the teeth, including gingivitis, periodontitis, and mandibular/maxillary osteomyelitis.
- Specific bacteria, principally Fusobacterium necrophorum, have been proposed as etiological agents.
- However, current evidence suggests MPPD is a more complex polymicrobial disease, and its epidemiology remains incompletely understood.
- Disruption of normal molar progression is a predisposing factor
- Dietary risk factors are poorly understood, but a an appropriate high-fiber diet that
- reflects species-specific forage ecology is likely protective.
- The prevalence of MPPD increases with age and is higher in animals that have previously had episodes of the disease.
- Dental trauma, especially to the incisors, likely predisposes
- Stressors that have been associated with MPPD include cold and wet weather, inadequate shelter, high stocking density, conspecific aggression, inappropriate contact with zoo visitors, confinement, vehicle noise, and moves between enclosures or institutions.
MPDD in wild and captive populations
- MPDD has been documented in the wild but prevalence is unknown
- In the wild, drought conditions and high population density considered predisposing factors.
- Prevalence in captivity is unknown, but MPPD is commonly cited as the most significant disease of captive macropods.
Microbiology
- Fusobacterium necrophorum (Fn) and bacteroides most commonly isolated
- Fn–although frequently identified and its endotoxins very likely key drivers of disease, there is evidence that Fn is neither necessary nor sufficient to cause MPPD
- A polymicrobial disease theory is supported, mostly comprised of anaerobes
Pathogenesis and Epidemiology
- Lesions are generally centered on periodontal tissues.
- Gingivitis and periodontitis are commonly considered to the constitute early stages
- Many cases progress to necrotizing osteomyelitis of the maxilla/mandible, with bony proliferation.
- Necrotizing anaerobic infection can also spread to other organs
- Some characteristics of molar progression in macropods, such as the persistence of “postfunctional” teeth beyond the period of direct occlusion, differ from other taxa
- The premolar and rostral molars are the most common sites of disease, suggesting that post-functional teeth may be a risk factor.
- Abrasive plant material has been proposed to be associated with gingival trauma and disease, but no definitive association has been found, and high fiber/more naturalistic diets are likely protective
- Low fiber diet associated with plaque accumulation
- Diet-induced gingival fragility could potentially make it more likely that rough plant material causes gingival trauma.
- A range of stressors associated with MPPD (see abstract for list)
- One study reported that odds of MPPD increased with the number of interzoo transfers
- Macropods older than 10 years are at least seven times more likely to develop disease.
- Fecal contamination of enclosures/environments is a proposed factor, Fn is a normal part of herbivore flora
- One study–Fn isolate from a red kangaroo with MPPD was added to the feed of tammar wallabies for 8 months, and none of the wallabies developed MPPD
Diagnosis, treatment, and prevention
- Summarized in table below, but antibiotics alone not likely to be successful, need to remove affected teeth as well
- Prevention is based on optimizing captive husbandry and identifying and addressing potential risk factors.
- Several vaccines trialed unsuccessfully
A recent study described hyperlipidemia and xanthomatotis in Yellow Footed Rock Wallabies.
What is the scientific name of this species?
What are xanthomas?
How did these wallabies present?
What findings were present on biochemistries?
What findings were present on necropsy?
How did body condition factor in to the development of xanthomas?
JZWM 2022 53(2) 470-479
HYPERLIPIDEMIA AND XANTHOMATOSIS IN YELLOW-FOOTED ROCK WALLABIES (PETROGALE XANTHOPUS) UNDER MANAGED CARE
Abstract
Xanthomas are localized lipid deposits in organs with associated granulomatous inflammation. Xanthomatosis is a rare condition in both human and veterinary medicine and is often linked to inherited or acquired dyslipidemias. Three female yellow-footed rock wallabies (Petrogale xanthopus) at a single institution were diagnosed via biopsy with cutaneous xanthomas secondary to hypertriglyceridemia and hypercholesterolemia, and an additional two female yellow-footed rock wallabies were diagnosed with xanthomas at a second institution. All cases presented with cutaneous masses at the haired skin and paw pad junctions of the extremities, and/or mucocutaneous junctions of the face or urogenital tract. The clinically affected individuals were overconditioned or obese, had lipemic serum, and had elevations in blood cholesterol and triglyceride levels. When full lipid panels were performed, inverse high- and low-density lipoprotein fractions were observed. Six other individuals at the first institution had identical husbandry but were of more appropriate body condition, were normolipidemic, and had no xanthomas. One of the affected animals was also concurrently diagnosed with hepatic lipidosis via liver biopsy. Pedigree review and evaluation for underlying endocrine diseases such as hypothyroidism were performed. Because all affected animals were found to be related, a genetic predisposition is possible but requires further investigation. Consideration for the predisposition of some individuals for obesity, hyperlipidemia, and subsequent xanthoma formation should be factored in the husbandry and medical management of this species.
Key Points
- Yellow footed rock wallabies are an Australian marsupial of the family Macropodidae; inhabit cliff faces and rocky outcrops in S. Australia, New South Wales and Queensland
- Lipemia - grossly visible plasma - hypertriglyceridemia
- Lipoproteins:
– Chylomicrons - formed by enterocytes to endogenous dietary lipids
– VLDL
– LDL
– HDL
- LDL and HDL mainly contain cholesterol
- Xanthomas - lozalized lipid deposits in organs with associated granulomatous inflammation
- Clinical presentation:
– Obesity
– Pink, raised dermal masses on paws, naris, muzzle, cloaca
- Biochem findings
– Elevated GGT, Tbili, AST
– Lipemic serum
– hypertryglyceridemia, hypercholesterolemia (persistent)
– Inverse high density lipoprotein to low density lipoprotein ratio (persistent)
- Pathology
– Cutaneous xanthomatosis, hepatic lipidosis, tracheal xanthoma in one case
- Outcome
– One animal with due to self mutilation of ulcerated xanthoma mass
– One animal lost wt, cholesterol normalized, no xanthomas on necropsy 1 month later
– One animal had c/s and persistent lipemia and elevated TG, chol
– One animal had lost some wt
– All young adult females, obese, grossly lipemic serum, elevated TG and cholesterol, inverse ratio of HDL to LDL
– Affected wallabies had higher mean wt, chol, TG, LDL; and lower HDL
– 3/5 cases developed elevated liver enzymes, once case hepatic lipidosis via liver bx
- Treatment - address the dyslipidemia
– 1 case had spontaneous resolution despite persistent hyperlipidemia
Take home message
- Hyperlipidemia and xanthomatosis in 5 yellow-footed rock wallabies; etiology undetermined
- Lipid and thyroid panels routine in this species
