PATHOLOGY OF BATS Cheryl Sangster, DVM, MVSc, Diplomate ACVP Taronga Conservation Society Australia Taronga Zoo, Bradleys Head Road Mosman NSW 2088 Bats are a highly diverse mammalian order, coming second only to rodents for number of species. The order is traditionally divided into two suborders, the Megachiroptera which includes the highly visual, non-echolocating fruit bats and the Microchiroptera which includes the smaller, echo-locating species. Previously, theories had been put forth suggesting that Chiroptera was not a monophyletic order, but rather that the megachiropterans were more closely related to primates. However, molecular technology has now put this theory to rest, solidly placing megabats and microbats within the same order. The suborder Megachiroptera includes one family, Pteropodidae, which within Australia is represented by five genera, Pteropus and Dobsonia (flying foxes), Nyctimene (tube-nosed fruit bats) and Syconycteris and Macroglossus (blossom bats). The most highly recognised species are the mainland flying foxes, the grey-headed (Pteropus poliocephalus), the black (Pteropus alecto), the spectacled (Pteropus conspicillatus) and the little red (Pteropus scapulatus). Numerous species of Microchiroptera are present in Australia, falling into the families Emballonuridae, Megadermatidae, Rhinolophidae (horseshoe bats), Hipposideridae (also commonly referred to as horseshoe bats), Vespertilionidae and Mollosidae. Fauna of Australia, Australian Government DEWHA website, http://www.environment.gov.au/biodiversity/abrs/publications/fauna-of-australia/fauna-1b.html. Accessed June 2008. Hall L, Richards G. 2000. Flying Foxes, Fruit and Blossom bats of Australia. Sydney: UNSW Press. Pp 135. Teeling EC, Springer MS, Madsen O, Bates P, O’Brien SJ, Murphy WJ. 2005. A molecular phylogeny for bats illuminated biogeography and the fossil record. Science 307: 580-584. THE NEUROLOGICAL BAT A common history accompanying bats presented to Australian pathology services will include a combination of neurological signs. These can include musculoskeletal signs such as weakness, paresis and paralysis, which may be ascending, gastrointestinal signs such anorexia and possibly diarrhoea, and abnormal behaviour including aggression, obtundence, failure to attempt escape and abnormal vocalisation. Differential diagnoses for these animals include, but may not be limited to the following: Australian bat lyssavirus (ABLV) Angiostrongylus cantonensis Lead poisoning Trauma Tick paralysis (Ixodes holocyclus) Toxoplasma gondii Other neurological disease (e.g. bacterial meningitis) Since the identification of Australian bat lyssavirus in the early 1990’s, it has become particularly important to approach these cases with caution and diligence. In cases of human exposure (bites and scratches) ruling out ABLV is paramount. Co-occurrence of ABLV with other neurological related aetiologies has been reported (e.g. lead poisoning), highlighting the importance of considering this pathogen in the face of histological and ancillary test results suggestive of other neurological diseases. See the following text for complete descriptions of these diseases. BAT PATHOLOGY BY AETIOLOGIC CATEGORY VIRAL DISEASES Disease name Australian bat lyssavirus Agent Australian bat lyssavirus, family Rhabdoviridae, genus Lyssavirus Significance Fatal disease affecting all 4 common species of flying foxes, at least one microchiropteran bat, the yellow-bellied sheath-tailed bat (Saccolaimus flaviventris) and humans. No domestic animals have been found to be affected to date. This disease is nationally notifiable within Australia Clinical Signs Muscle weakness, paresis or paralysis Aggression, obtundence or a failure to attempt escape Abnormal vocalisation Inability to fly Gross Pathology None Microscopic Pathology May be none on H&E Nonsuppurative meningoencephalomyelitis in brain and cervical spinal cord, with neuronal necrosis, gliosis and perivascular cuffing Nonsuppurative ganglioneuritis of the Gasserian and spinal ganglia Nonsuppurative sialoadenitis (rare) Eosinophilic intranuclear inclusions bodies in neurons (Negri bodies, rarely present) Intracytoplasmic vacuolation of neurons Differential Diagnoses Angiostrongylus cantonensis Lead poisoning Trauma Tick paralysis (Ixodes holocyclus) Toxoplasma gondii Other neurological disease (e.g. bacterial meningitis) Diagnostic Pathway Suspect ABLV based on history of abnormal behaviour and/or neurological deficits. Absence of microscopic changes does not rule out ABLV. Submit minimum of half brain frozen or chilled to 4°C to reference lab as per instruction of state authority. Confirmation based on fluorescent antibody test, PCR and/or virus isolation on fresh/frozen brain or immunohistochemistry on fixed brain. Other nervous tissues, saliva, salivary gland or cerebrospinal fluid can be used for ancillary testing, but results are less reliable. Positive identification of an alternative aetiology for neurological signs does not rule out ABLV (e.g. lead poisoning and ABLV have been confirmed in the same animal). References Australian bat lyssavirus, Hendra virus and Menangle virus information for veterinary practitioners. 2001. http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-pubsother-bat_lyssa.htm Hooper PT, Fraser GC, Foster RA, Storie GJ. 1999. Histopathology and immunohistochemistry of bats infected by Australian bat Lyssavirus. Aust Vet J 77: 595-599. McColl KA, Chamberlain T, Lunt RA, Newberry KM, Middleton D, Westbury HA. 2002. Pathogenesis studies with Australian bat lyssavirus in grey-headed flying foxes (Pteropus poliocephalus). Aust Vet J 80: 636-641. Disease name Hendra virus Agent Hendra virus, genus Henipavirus, family Paramyxoviridae Significance Pteropid bats (fruit bats) are believed to be wildlife reservoirs for Hendra virus, which is the cause of fatal respiratory disease in horses and fatal encephalitis in humans. Clinical Signs None, Hendra virus is a subclinical disease in bats Gross Pathology None Microscopic Pathology Perivascular lymphocytic inflammation and/or fibrinoid vascular degeneration with lymphocytic and histiocytic infiltration in blood vessels. Mesenteric and alimentary arteries are most often affected followed by splenic central arteries in periarterial lymphoid sheaths, renal arteries, meningeal arteries, placental vessels and foetal tissues. Viral antigen in endothelial and smooth muscle cells of affected vessels can be demonstrated by immunohistochemistry. Differential Diagnoses Nipah virus Diagnostic Pathway Identification of suggestive vascular lesions by histopathology followed by confirmation with immunohistochemistry. Immunostaining is more effective than virus isolation, as active virus is often neutralised by high antibody titres, while inactive viral material will remain in lesions. References Williamson MM, Hooper PT, Selleck PW, Gleeson LJ, Daniels PW, Westbury HA, Murray PK. 1998. Transmission studies of Hendra virus (equine morbillivirus) in fruit bats, horses and cats. Aust Vet J 76: 813-818. Williamson MM, Hooper PT, Selleck PW, Westbury HA, Slocombe RF. 1999. Experimental Hendra virus infection in pregnant guinea-pigs and fruit bats (Pteropus poliocephalus). J Comp Path 122: 201-207. Disease name Nipah virus Agent Nipah virus, genus Henipavirus, family Paramyxoviridae Significance Based on serology, pteropid bats (fruit bats) are a hypothesised wildlife reservoir for Nipah virus, the causative agent of a febrile respiratory and neurological disease in pigs and viral encephalitis in humans. Clinical Signs None Gross Pathology None Microscopic Pathology Following experimental infection, various histological lesions were identified, the most suspicious being small intestinal submucosal vasculitis, similar to Hendra virus lesions, and ganglioneuritis, similar to lesions in Nipah infected cats. However, immunohistochemical staining and virus isolation for Nipah virus was negative in these lesions. Differential Diagnoses Hendra virus Diagnostic Pathway Immunohistochemical staining and virus isolation may be able to be attempted. References Middleton DJ, Morrissy CJ, van der Heide BM, Russell GM, Braun MA, Westbury HA, Halpin K, Daniels PW. 2007. Experimental Nipah virus infection in pteropid bats (Pteropus poliocephalus) J Comp Path 136: 266-272. BACTERIAL DISEASES Disease name Abscesses, pneumonia, meningitis Agent Various, including Pasteurella sp., Streptococcus sp., Staphylococcus sp. and Enterobacteria Significance Bacterial infections are relatively common in bats listed within the Australian Registry of Wildlife Health, with most occurrences relating to aspiration pneumonia and secondary to bite wounds Clinical Signs Related to the organ system affected Neurological signs can occur with meningitis Tachypnoea and dyspnoea with pneumonia Gross Pathology Purulent exudation can be recognised with abscesses. Pulmonary infections result in consolidation and abscess formation. Gross lesions can be unilateral. Microscopic Pathology Neutrophil dominated inflammation is most common in Registry cases Differential Diagnoses Differentials for abscesses include neoplasia and granulomatous disease (e.g. fungal disease). Diagnostic Pathway Suspicion based on gross inspection can be confirmed with histological examination and microbial culture. References Helmick KE, Heard DJ, Richey L, Finnegan M, Ellis GA, Nguyen A, Tucker L, Weyant RS. 2004. A Pasteurella-like bacterium associated with pneumonia in captive megachiropterans. J Zoo Wild Med 35: 88-93. MYCOTIC DISEASES Disease name White-nose syndrome Agent Geomyces destructans Significance An emerging disease first documented in New York state in February 2006, which appears to be responsible for the death of thousands of microchiropteran bats in the eastern US states and Canadian provinces with continued concentric spread. Clinical Signs Emaciation and poor body condition Accumulation of white, fungal material around nose and elsewhere on body Deterioration of skin of wing webs and elsewhere Gross Pathology Very little body fat Marked dehydration Microscopic Pathology Fungal invasion of viable skin with no inflammatory reaction in hibernating bats, but marked inflammation in non-hibernating animals Cup-like epidermal erosions and ulcers on wing web and pinnae with fungal invasion of hair follicles and sebaceous glands Fungal hyphae branched and septate with variation from parallel 2µm walls to undulating walls ranging from 3-5µm wide Fungal conidia have distinctive curved shape Differential Diagnoses Presence of white fungus on muzzle of hibernating bats appears to be quite distinctive Saprophytic post mortem invaders need to be ruled out on submitted carcasses Diagnostic Pathway Evidence of gross changes, although distinctive, is often lost on route to lab Culture is difficult with a resultant low sensitivity Fulfilment of histological criteria is sufficient for a diagnosis PCR on small volumes of tissue is highly specific and sensitive and can be used on live animals References Blehert DS, Hicks AC, Behr M, Meteyer CU, Berlowski-Zier BM, Buckles EL, Coleman JTH, Darling SR, Gargas A, Niver R, Okoniewski JC, Rudd RJ, Stone WB. 2009. Bat white-nose syndrome: an emerging fungal pathogen? Science 323: 227. Cryan PM, Meteyer CU, Boyles JG, Blehert DS. 2010. Wing pathology of white-nose syndrome in bats suggests life-threatening disruption of physiology. BMC Biology 8: 135 Lorch JM, Gargas A, Meteyer CU, Berlowski-Zier BM, Green DE, Shearn-Bochsler V, Thomas NJ, Blehert DS. 2010. Rapid polymerase chain reaction diagnosis of white-nose syndrome in bats. J Vet Diagn Invest 22: 224-230. Meteyer CU, Buckles EL, Blehert DS, Hicks AC, Green DE, Shearn-Bochsler V, Thomas NJ, Gargas A, Behr M. 2009. Histopathologic criteria to confirm white-nose syndrome in bats. J Vet Diagn Invest 21: 411-414. Disease name Histoplasmosis Agent Histoplasma capsulatum Significance Bat guano is a common source of Histoplasma capsulatum, the causative agent of histoplasmosis in humans and other vertebrate animals worldwide, including Australia. Although prevalence of infection in microchiropteran bats can be moderate to high, little to no morbidity or mortality in bats typically occurs. No record of infection in megachiropterans could be found. Clinical Signs Rare Gross Pathology None Microscopic Pathology Numerous intracellular yeast-like cells in intra-alveolar and septal pulmonary macrophages Yeasts appear as small blue dots (1-2µm) surrounded by a thin, clear halo on H&E Yeasts can be highlighted in tissue using Periodic Acid Schiff (PAS) or methenamine silver (Grocott’s or Gomori’s) stains. Differential Diagnoses Pulmonary infection with Blastomyces dermatitidis has been reported in a bat, but should be easily differentiated based on its larger yeast size exhibiting broad based budding and the presence of a granulomatous inflammatory reaction. Diagnostic Pathway Identification of yeasts in tissue using histopathology is highly suggestive Fungal culture of lung, liver, spleen and gut is definitive but should be approached with caution due to human infection risk PCR and immunohistochemistry involve less risk (not currently available in Aust.) References Jackson S. 2003. Australian Mammals Biology and Captive Management. Collingwood: CSIRO Publishing. Pp 524. Maxie MG. 2007. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals, Volume 3, Fifth Edition. Philadelphia: Elsevier Saunders. Pp 737. Raymond JT, White MR, Kilbane TP, Janovitz EB. 1997. Pulmonary blastomycosis in an Indian fruit bat (Pteropus giganteus). J Vet Diagn Invest 9: 85-87. Taylor ML, Chavez-Tapia CB, Rodriguez-Arellanes G, Pena-Sandoval GR, Toriello C, Perex A, Reyes-Montes MR. 1999. Environmental conditions favoring bat infection with Histoplasma capsulatum in Mexican shelters. Am J Trop Med Hyg 61: 914-919. Disease name Wing web infections; slimy wing Agent Candida spp., often co-infected with Pseudomonas sp. bacteria Significance Wing web infections typically occur when bats have insufficient access to sunlight, fresh air and space to flap wings, usually in situations of poor husbandry or tightly applied bandages. Clinical Signs Areas of erythema progress to greyish, pseudomembranous slime. Fur may epilate easily, in matted clumps. Often accompanied by foul odour. Gross Pathology As per clinical signs Microscopic Pathology Budding yeasts can be seen on impression smears Dermatitis with intralesional fungal hyphae, pseudohyphae (chains of yeasts) and individual yeasts would be expected Differential Diagnoses Necrosis secondary to trauma, particularly if gangrenous Diagnostic Pathway Identification of yeasts in tissue using histopathology or on impression smears Fungal culture of wing web scraping References Olsson AR, Woods R. 2008. Bats. In: Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing. Jackson S. 2003. Australian Mammals Biology and Captive Management. Collingwood: CSIRO Publishing. Pp 524. PROTOZOAL DISEASES Disease name Toxoplasmosis Agent Toxoplasma gondii Significance Two reported cases in Australian flying foxes have both occurred in bats experiencing some degree of captivity, which may have increased exposure to oocysts. No reports exist from free-ranging animals but increasing encroachment of human urbanisation on bat habitat may increase opportunities for infection. The presence of neurological signs makes this an important addition to the list of differential diagnoses for ABLV. Clinical Signs Respiratory signs Lethargy Anorexia Twitching and paresis (neurological signs) Gross Pathology Mottled appearance to lungs Small white foci on various organs Microscopic Pathology Widespread, multifocal necrosis with pyogranulomatous inflammation Foci of necrosis and gliosis within nervous tissues Intralesional tachyzoites and bradyzoites within macrophages and tissue cells Differential Diagnoses For neurological changes: Australian bat lyssavirus Angiostrongylus cantonensis Lead poisoning Trauma Tick paralysis (Ixodes holocyclus) Other neurological disease (e.g. bacterial meningitis) For intracellular protozoa Neospora caninum Diagnostic Pathway Histopathologic appearance of tissue cysts is highly suggestive Immunohistochemistry References Sangster CR, Gordon AN, Hayes D. In Press. Systemic toxoplasmosis in captive flying-foxes. Aust Vet J. Disease name Hepatocystosis Agent Hepatocystis spp. Significance Vector borne infection found in many Old world mega and microchiropterans, including Australian species. Infections tend to be self limiting and of little clinical significance. Clinical Signs None Gross Pathology 2-4mm translucent merocysts can been seen on the surface of the liver in affected primates. Visualisation of cysts in bats is rare (Karrie Rose, personal communication). Microscopic Pathology Large (4-6mm) merocysts form in hepatic parenchymal cells. With maturity, a colloid filled vacuole forms in the middle and merozoites develop around the periphery. Inflammatory cells can be present around merocyst borders. Cysts are also present in lung interstitium Ring shaped trophozoites and round to oblong, nucleated gamonts occur in circulating erythrocytes. Differential Diagnoses Plasmodium spp. has very similar ring-shaped trophozoites in erythrocytes, but this organism does not form mature merocysts in the liver and produces characteristic protozoal pigment. Diagnostic Pathway Histopathologic appearance of merocysts is highly diagnostic Molecular techniques are required for speciation of the pathogen References Duval L, Robert V, Csorba G, Hassanin A, Randrianarivelojosia M, Walston J, Nhim T, Goodman SM, Ariey F. 2007. Multiple host-switching of Haemosporidia parasites in bats. Malaria Journal 6: 157-164. Gardiner CH, Fayer R, Dubey JP. 1998. An Atlas of Protozoan Parasites in Animal Tissues, Second Edition. Washington: Armed Forces Institute of Pathology. Pp 84. Landau I, Adam JP. ca. 1972. Two types of schizonts of Hepatocystis sp., a parasite of insectivorous bats in the Congo-Brazzaville. Laboratory meeting notes of the Laboratoire de Zoologie (Vers) associe au CNRS, Museum National d’Histoire Naturelle, Paris. Pp 2. Olival KJ, Stiner EO, Perkins SL. 2007. Detection of Hepatocystis sp. in Southeast Asian flying foxes (Pteropodidae) using microscopic and molecular techniques. J Parasitol 93: 15381540. Olsson AR, Woods R. 2008. Bats. In Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing T-W-Fiennes RN. 1972. Pathology of Simian Primates Part II: Infectious and Parasitic Diseases. Basel: S. Karger. Pp 770. Disease name Renal coccidiosis Agent Nephroisospora eptesici nov. gen., n. sp. Significance Reported in big brown bats with prevalence ranging from 3.5-19%. Infections appear to be incidental. Most notable is that although Nephroisospora eptesici nov. gen., n. sp. is closely related to Besnoitia, Hammondia, Toxoplasma and Neospora, it accomplishes sporogony within the host, not apparently requiring oxygen as do these other species. No reports in megachiropteran bats. (Note: Various enteric coccidia identified as Eimeria have been described in bats, again with little known significance. No further discussion of these will be made.) Clinical Signs None that are known Gross Pathology 0.5 to 1mm diameter white, raised or flat foci are seen in the cortex of the kidney. Microscopic Pathology Renal tubules are dilated to form cysts and are lined with hypertrophied epithelium containing asexual and sexual coccidian stages. Tubular lumens contain oocysts, which are sporulated with 2 sporocysts each containing 4 sporozoites. Differential Diagnoses Klossiella sp. previously reported in kidneys of Myotis sodalis; No dilation of tubules or intratubular sporogony was described in this case. Renal coccidiosis with tubular dilation was separately reported in Pipistrellus pipistrellus, Myotis mystacinus, M. nattereri and Nyctalus noctula. In this report, no intratubular sporogony was seen, indicating it was possibly a different species. Diagnostic Pathway Histopathologic examination of renal tissue Molecular characterisation may be possible on fresh or frozen tissue References Gruber AD, Schulze CA, Brugmann M, Pohlenz J. 1996. Renal; coccidiosis with cystic tubular dilatation in four bats. Vet Path 33: 442-445. Kusewitt DF, Wagner JE, Harris PD. 1977. Klossiella sp. in the kidneys of two bats (Myotis sodalist). Vet Parasitol 3: 365-369. Wunschmann A, Wellehen JFX, Armien A, Bemrick WJ, Barnes D, Averbeck GA, Roback R, Schwabenlander M, D’Almeida E, Joki R, Childress AL, Cortinas R, Gardiner CH, Greiner EC. 2010. Renal infection by a new coccidian genus in big brown bats. J Parasitol. 96: 178-183. Disease name Babesiosis Agent Babesia vesperuginis Significance Tick transmitted disease identified in various microchiropteran species in the British Isles, continental Europe and the Americas. No reports in fruit bats could be found nor reports in Australasian microchiropteran species. Clinical Signs No descriptions in bats, but clinical signs in domestic animals include: Fever Regenerative anaemia with reduced blood haemoglobin and increased reticulocytes Jaundice Haemoglobinuria CNS signs when parasitised erythrocytes sludge in brain capillaries Gross Pathology Splenomegaly Microscopic Pathology Intraerythrocytic trophozoites (round to oval rings, 1.0 to 1.8µm); amoeboid forms (2.0 to 4.0µm rings with central or marginated nucleus) and merozoites (pear shaped with distinct nucleus, 1.4 to 2.0µm) Brain capillaries congested with parasitised erythrocytes Differential Diagnoses Other haematosporidia (Hepatocystis sp., Plasmodium sp.) have similar appearing trophozoites, but should be easily differentiated based on the morphology of intravascular merozoites of Babesia sp. Consider other causes of intravascular haemolytic anaemia (e.g. immune mediated disease or a toxin such as copper) Diagnostic Pathway Suspicion based on clinical and post mortem signs Blood or organ smears from freshly dead animals can reveal parasitised erythrocytes PCR on fresh or frozen macerated heart tissue for speciation and diagnosis in further autolysed or archived animals References Concannon R, Wynn-Owen K, Simpson VR, Birtles RJ. 2005. Molecular characterization of haemoparasites infecting bats (Microchiroptera) in Cornwall, UK. Parasitology 131: 489-496. Gardiner CH, Fayer R, Dubey JP. 1998. An Atlas of Protozoan Parasites in Animal Tissues, Second Edition. Washington: Armed Forces Institute of Pathology. Pp 84. Gardner RA, Molyneux DH, Stebbings RE. 1987. Studies on the prevalence of haematozoa of British bats. Mammal Rev 17: 75-80. Marinkelle CJ. 1996. Babesia sp. in Colombian bats (Microchiroptera). J Wild Dis 32: 534-535. Kocan AA, Waldrup KA. 2001. Blood-inhabiting Protozoans. In Parasitic Diseases of Wild Mammals Eds. Samuel WM, Pybus MJ, Kocan AA. Ames: Iowa State University Press. Pp 559. METAZOAN PARASITIC DISEASES Disease name Neuro-angiostrongylosis Agent Angiostrongylus cantonensis (Rat lungworm) Significance Is a common cause of paresis in Black and Grey-headed flying foxes, and has been reported in Little Red flying foxes and various other Australian native and introduced fauna. Clinical presentation and history cannot be differentiated from Australian bat lyssavirus. Clinical Signs Hind limb or tetraparesis Depression Anorexia Gross Pathology Occasional petechial haemorrhages on surface of cerebral cortex Meningeal congestion or cloudiness Often no gross changes Microscopic Pathology Eosinophilic and granulomatous meningoencephalitis with macrophages, eosinophils, lymphocytes and lesser plasma cells and multinucleated giant cells, most severe in brainstem and cerebellum Perivascular cuffs of macrophages, lymphocytes and eosinophils Tracts of tissue disruption, gliosis and/or haemorrhage Nematode sections in subarachnoid space of cerebral sulci and/or cerebellar folds and less often in parenchyma or ventricles Metastrongyle larval characteristics include: coelomyarian musculature, accessory hypodermal chords, lateral chords, and a large intestine In animals with only stage 3 larvae, presence of little inflammation or parenchymous change with few very small nematodes detectable Differential Diagnoses Australian bat lyssavirus Lead poisoning Trauma Tick paralysis (Ixodes holocyclus) Toxoplasma gondii Other neurological disease (e.g. bacterial meningitis) Diagnostic Pathway Suspect neuro-angiostrongylosis based on history of hind limb paresis and depression. Exert caution, however, as these signs are also consistent with ABLV. If human exposure has occurred, proceed as for a lyssavirus suspect. Parasitological identification of worms found grossly or extracted through maceration of half the brain allows for definitive diagnosis. Histological identification of larvae consistent with Angiostrongylus spp. in the brain is highly suggestive, as the native species of Angiostrongylus, A. mackerrasae, has not been associated with neurological disease. Tracts of tissue disruption associated with eosinophils, gliosis and/or haemorrhage are also suggestive. References Barrett JL, Carlisle MS, Procliv P. 2002. Neuro-angiostrongylosis in wild Black and Greyheaded flying foxes. Aust Vet J 80: 554-558. Reddacliff LA, Bellamy TA, Hartley WJ. 1999. Angiostrongylus cantonensis infection in greyheaded fruit bats (Pteropus poliocephalus). Aust Vet J 77: 466-468. Disease name Pulmonary angiostrongylosis Agent Angiostrongylus mackerassae (presumed) Significance Recent case of pulmonary disease in a flying fox as a result of Angiostrongylus has been described (manuscript pending). Significance of this disease to flying fox populations is unknown. Clinical Signs Unknown Gross Pathology Unknown Microscopic Pathology Adult worms with characteristic metastrongylid features (smooth cuticle, coelomyarian musculature, large intestine lined by multinucleate cells, accessory hypodermal chords, lateral chords) in blood vessels Larval worms in air spaces Differential Diagnoses Other causes of pneumonia (bacterial, secondary to trauma) Diagnostic Pathway Parasitological identification of worms found grossly or extracted through maceration of fresh or fixed lung allows for definitive diagnosis Histological identification of larvae and adults consistent with Angiostrongylus spp. in the lung References Mackie J, Lacasse C, Spratt D. Pulmonary angiostrongylosis in a black flying fox. Manuscript in progress. Disease name Toxocariasis Agent Toxocara pteropodis Significance Occur in all species of flying fox with up to 50% prevalence, but very low morbidity and mortality. Pups are infected via transmammary exposure to larvae. Typically 3-5 worms mature in GI tract of pups and eggs are shed in faeces. Adults consume eggs and hatched larvae migrate to the liver via the portal circulation, where they remain dormant until mobilised in females at the time of parturition and migrate to the mammary gland. Disease occurs rarely as the result of aberrant migration, heavy parasitic burden and intestinal accidents. Clinical Signs Small size for age and bloated stomach with heavy burdens Various other clinical signs are dependent on site of aberrant migration or presence of intestinal accident Gross Pathology Adult worms present in the intestinal tract of pups Adult worms present in aberrant sites in pups Volvulus of intestine Microscopic Pathology Vascular and degenerative changes related to aberrant migration Intestinal accidents result in congestion, oedema and necrosis of infarcted tissue Differential Diagnoses Other intestinal parasites recorded in bats include trichostrongyles, dendrolecithid trematodes and one species of cestode. Diagnostic Pathway Examination of faeces from pups for presence of ascarid eggs Identification of adult worms based on presence of three large lips and body size References Heard DJ, Garner M, Greiner E. 1995. Toxocariasis and intestinal volvulus in an island flying fox (Pteropus hypomelanus). J Zoo Wildl Med 26: 550-552. Prociv P. 1990. Aberrant migration by Toxocara pteropodis in flying-foxes – two case reports. J Wild Dis 26: 532-534. Spratt D, Beveridge I, Skerratt L, Speare R. 2008. Guide to the identification of common parasites of Australian mammals. In Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing. Disease name Tick paralysis Agent Ixodes holocyclus Significance Variably causes loss of large numbers of Spectacled flying foxes in the Atherton Tablelands rainforests. Clinical Signs Ascending flaccid paralysis Dyspnoea Cyanotic mucous membranes Gross Pathology Trauma associated with fly strike or predation, secondary to paralysis Microscopic Pathology No specific changes Differential Diagnoses For neurological signs Australian bat lyssavirus Angiostrongylus cantonensis Lead poisoning Trauma Toxoplasma gondii Other neurological disease (e.g. bacterial meningitis) For tick like ectoparasites Argus macrodermae (the bat tick of Ghost bats) Nycteribiid flies Diagnostic Pathway Identification of attached tick on bat as Ixodes holocyclus: Legs form a V-shape line from the snout down the body First and last pairs of legs are brown, second and third are pale Body is pear to oval shaped, light grey with dark bands on the side Scute (face) is oval but wider at base and brown in colour Snout is very long Due to similarity of presenting signs, diagnostic testing to rule out ABLV and histopathology to rule out Angiostrongylus cantonensis are required to make a definitive diagnosis. References Campbell FE, Atwell RB, Smart L. 2003. Effects of the paralysis tick, Ixodes holocyclus, on the electrocardiogram of the Spectacled Flying Fox, Pteropus conspicillatus. Aust Vet J 81: 328-331. Garnett S, Whybird O, Spencer H. 1999. The conservation status of the Spectacled Flying Fox, Pteropus conspicillatus in Australia. Aust Zool 31: 38-54. Paralysis Ticks Agnote DAI-267 Second Edition, NSW Agriculture website, http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0013/160321/paralysis-ticks.pdf. Accessed June 2008 Spratt D, Beveridge I, Skerratt L, Speare R. 2008. Guide to the identification of common parasites of Australian mammals. In: Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing. Disease name Other ectoparasites Agent Nycteribiid flies (spider-like flat flies) Streblid flies (flat flies) Mites Fleas Significance The impact of these parasites on their chiropteran hosts is not fully understood, but is expected to be minimal, except in the face of heavy burdens. Nycteribiid and streblid flies are thought to possibly transmit erythrocytic parasites. Clinical Signs Flat flies can be found running through the coat of bats. Gross Pathology Presence of ectoparasites on skin surface Microscopic Pathology None Differential Diagnoses Ixodes holocyclus is the only ectoparasite known to have significant detrimental effects on Australian bats. Diagnostic Pathway Identification of parasite based on morphology References Fauna of Australia, Australian Government DEWHA website, http://www.environment.gov.au/biodiversity/abrs/publications/fauna-of-australia/fauna-1b.html. Accessed June 2008. Jackson S. 2003. Australian Mammals Biology and Captive Management. Collingwood: CSIRO Publishing. Pp 524. Spratt D, Beveridge I, Skerratt L, Speare R. 2008. Guide to the identification of common parasites of Australian mammals. In: Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing. TOXICOSIS Disease name Lead poisoning, plumbism Agent Lead, typically from automobile and industrial emissions Significance Historically was a disease of urban fruit bats, speculatively due to high levels of atmospheric lead resulting from automobile and industrial emissions. Recent examination of a series of 100 neurological bats did not identify a single case of lead poisoning. Clinical Signs Inability to fly, weakness, ataxia, muscle tremors Emaciation, no appetite Excess salivation, diarrhoea Gross Pathology No specific changes, but possible secondary traumatic injuries Microscopic Pathology Degeneration of renal proximal tubular epithelium with dissociation of cells into lumen Renal tubular epithelial attenuation +/- tubular dilation and intraluminal accumulation of cellular debris and hyaline casts Intranuclear, eosinophilic, inclusion bodies in kidneys with >40 µg/g lead dry weight Inclusion bodies are occasionally acid fast with Ziehl Neelsen stain Differential Diagnoses For neurological changes: Australian bat lyssavirus Angiostrongylus cantonensis Trauma Tick paralysis (Ixodes holocyclus) Toxoplasma gondii Other neurological disease (e.g. bacterial meningitis) For renal tubular necrosis Other heavy metal toxicoses Possibly plant and mycotoxins Diagnostic Pathway Lead tissue levels > 10ppm wet weight (or µg/g dry tissue) in liver and > 25 ppm in kidney indicates toxicity in domestic animals and this measure has been adopted for bats. Chronic exposure can be measured using bones, teeth and fur. Fresh, frozen or fixed tissue is appropriate for testing heavy metals. References Barrett J, Rodwell B, Lunt R, Rupprecht C, Field H, Smith G, Young P. 2005. Australian bat Lyssavirus: Observations of natural and experimental infection in bats. Wildlife Disease Association International Conference Proceedings, Pp.149-150. Hariano B, Ng J, Sutton RH. 1993. Lead concentrations in tissues of fruit bats (Pteropus sp.) in urban and non-urban locations. Wildl Res 20: 315-320. Skerratt LF, Speare R, Berger L, Winsor H. 1995. Lyssaviral infection and lead poisoning in black flying foxes from Queensland. J Wild Dis 34: 355-361. Sutton RH. 1983. Lead poisoning in grey-headed fruit bats (Pteropus poliocephalus). J Wild Dis 19: 294-296. Disease name Rodenticide poisoning Agent Anti-coagulant rodenticides Significance Bats are exposed when buildings are fumigated where bats are roosting and following spraying of crops. Bats do not typically eat rodenticide baits. Clinical Signs Lameness Swollen joints Ventral haematoma Dyspnoea and respiratory depression Nasal and rectal bleeding Vomiting of blood Gross Pathology Subcutaneous and internal haemorrhage Microscopic Pathology Haemorrhage in multiple tissues Differential Diagnoses Trauma Diagnostic Pathway Identification of grossly apparent haemorrhage in the absence of evidence of physical trauma should raise suspicion. Investigation to determine if rodenticide has been applied in the area of the affected animal Prolonged clotting times in blood obtained from live animal References Olsson AR, Woods R. 2008. Bats. In: Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing. PHYSICAL INJURY Disease name Skeletal injuries Agent Collisions with vehicles, fences, powerlines and trees; shooting injuries; predator attacks Significance Humeral fractures are very common, followed by radial, metacarpal and phalangeal fractures. Vertebral compression fractures and luxations can result when animals fly front on into stationary objects. Clinical Signs Inability to fly Palpable or visible displacement Posterior paralysis with vertebral injury Neurological signs with head trauma Gross Pathology Long bone fractures are often severely comminuted Loss of digits is often accompanied by loss of significant portions of the adjacent wing web Vertebral injuries often occur at the junction of the most caudal thoracic and first lumbar vertebrae. Similar to birds, bats have a rigid thoracic vertebral column, facilitating injury at the first point of flexibility, the thoracolumbar junction. Microscopic Pathology Spinal cord haemorrhage and degeneration secondary to vertebral injury Differential Diagnoses Neurological signs secondary to head trauma and posterior paralysis resulting from vertebral injury are differentials for Australian bat lyssavirus, Angiostrongylus cantonensis, lead poisoning, Ixodes holocyclus and other neurological diseases. Diagnostic Pathway Gross examination will reveal most skeletal injuries, though vertebral injuries can be subtle and difficult to assess. Fixation and decalcification of the vertebral column en bloc can facilitate examination by allowing subsequent longitudinal sectioning of the tissue. Be aware that cranial and other skeletal trauma can occur secondary to primary neurological disease. If human exposure has occurred, ruling out Australian bat lyssavirus is warranted. References Olsson AR, Woods R. 2008. Bats. In: Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing. Rose K. Common diseases of urban wildlife: mammals. ARWH website, http://www.arwh.org/ARWH/CommonDisease/CDisease_Display.aspx. Accessed June 2008. Disease name Electrocution Agent Power lines, deterrent electric grids around fruit-growing areas Significance Significant numbers of pteropid bats are injured or killed in this manner. Infants often survive when the dams are electrocuted due to the insulating effects of fur. Clinical Signs Sudden death Singed fur Burns to pinnae, wing membranes, uropatagium, toes and/or thumbs Muscle fasciculations, seizures and cardiac arrhythmias in surviving animals Gross Pathology Singed fur may be the only change present Burns to the integument, as described above, with associated necrosis, depending on duration of survival following electrocution event Congestion of visceral organs and lymph nodes and multifocal petechiae can be present Pulmonary oedema Burns in the mouth of neonates Microscopic Pathology Severe burns to skin result in coagulation necrosis of all components (epidermis, dermis and adnexa) with acute inflammation, vasculitis and thrombosis, given the animal survives for a period of time. With time, this acute inflammation will be replaced by histiocytes setting up a reparative granulation process. Pulmonary oedema may be detectable. Differential Diagnoses Burns from bush fires, lightning strikes, etc. Diagnostic Pathway History of bat being found on power lines and electric fences or on the ground below and presence of external burns is highly suggestive. References Fairbrother A, Locke LN, Hoff GL. 1996. Noninfectious Diseases of Wildlife, Second Edition. Ames: Iowa State University Press. Pp 219. Maxie MG. 2007. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals, Volume 1, Fifth Edition. Philadelphia: Elsevier Saunders. Pp 899. Merck MD. 2007. Veterinary Forensics, Animal Cruelty Investigations. Ames: Blackwell Publishing. Pp 327. Olsson AR, Woods R. 2008. Bats. In: Medicine of Australian Mammals Eds. Vogelnest L, Woods R. Melbourne: CSIRO Publishing. Radostits OM, Blood DC, Gay CC. 1994. Veterinary Medicine, Eighth Edition. London: Bailliere Tindall. Pp 1763. Disease name Fencing entrapments Agent Barb wire fence Significance Large numbers of bats are injured and killed every year. Fencing injuries are recognised as threatening processes in the recovery plans for the Spectacled flying fox (Pteropus conspicillatus) and the Grey-headed flying fox (Pteropus poliocephalus). Clinical Signs Most affected bats will be found on the fencing with lacerations, twists and other physical injuries. Gross Pathology Mouth: Puncture wounds, teeth fractures Wing membranes: Lacerations, punctures, twists resulting in ischemic necrosis and loss of the tissue in days following the entanglement Bones: Fractures and exposure with tearing of wing membrane Microscopic Pathology Histopathological changes related to physical trauma and resulting ischemic necrosis Differential Diagnoses Other causes of physical trauma, including predator attacks, hit by cars, etc. Diagnostic Pathway Diagnosis is based on history and appropriate gross lesions. References Wildlife Friendly Fencing Project website, http://www.wildlifefriendlyfencing.com/ Accessed June 2008. NEOPLASTIC DISEASES Disease name Round cell: e.g. Lymphosarcoma Epithelial: e.g. Basosquamous carcinoma Mesenchymal: e.g. Subcutaneous leiomyosarcoma Agent Spontaneous Papillomavirus Microchip-associated Significance Neoplasia is not commonly seen in wild or captive bats. Clinical Signs As per the presentation of the lesion Gross Pathology Nodules, thickening, organ enlargement, etc. Microscopic Pathology As per the cell of origin and malignancy of the tumour Differential Diagnoses Abscesses Granulomas Diagnostic Pathway Histopathology Immunohistochemistry and PCR to identify cell of origin and pathologic aetiology References Andreasen CB, Dulmstra JR. 1996. Multicentric malignant lymphoma in a pallid bat. J Wild Dis 32: 545-547. McKnight CA, Wise AG, Maes RK, Howe C, Rector A, Van Ranst M, Kiupel M. 2006. Papillomavirus-associated basosquamous carcinoma in an Egyptian bat (Rousettus aegyptiacus). J Zoo Wildl Med 37: 193-196. Siegal-Willot J, Heard D, Sliess N, Nayden D, Roberts J. Microchip-associated leiomyosarcoma in an Egyptian fruit bat (Rousettus aegyptiacus). J Zoo Wildl Med 38: 352356. MISCELLANEOUS DISEASES WITH RARE REPORTS IN BATS WORLDWIDE Cryptosporidium sp. Dubey JP, Hamir AN, Sonn RJ, Topper MJ. 1998. Cryptosporidiosis in a bat (Eptesicus fuscus). J Parasitol 84: 622-623. Blastomyces dermatitidis Raymond JT, White MR, Kilbane TP, Janovitz EB. 1997. Pulmonary blastomycosis in an Indian fruit bat (Pteropus giganteus). J Vet Diagn Invest 9: 85-87. Iron storage disease Farina LL, Heard DJ, LeBlanc DM, Hall JO, Stevens G, Wellehan JFX, Detrisac CJ. 2005. Iron storage disease in captive Egyptian fruit bats (Roussettus aegyptiacus): relationship of blood iron parameters to hepatic iron concentrations and hepatic histopathology. J Zoo Wildl Med 36: 212-221. Copper toxicosis Hoenerhoff M, Williams K. 2004. Copper-associated hepatopathy in a Mexican fruit bat (Artibeus jamaicensis) and establishment of a reference range for hepatic copper in bats. J Vet Diagn Invest 16: 590-593. Algal poisoning Pybus MJ, Hobson DP. 1986. Mass mortality of bats due to probable blue-green algal toxicity. J Wildl Dis 22: 449-450. DISEASES FOR WHICH BATS ARE KNOWN OR SUSPECTED TO BE CARRIERS IN AUSTRALIA Leptospira spp. Smythe LD, Field HE, Barnett LJ, Smith CS, Dohnt MF, Symonds ML, Moore MR, Rolfe PF. 2002. Leptospiral antibodies in flying foxes in Australia. J Wild Dis. 38: 182-186. Menangle virus Halpin K, Young PL, Field H, Mackenzie JS. 1999. Newly discovered viruses of flying foxes. Vet Micro. 68: 83-87.