AFIP Wednesday Slide Conference - No. 27

7 May 1997
Conference Moderator: COL Nancy Jaax
Diplomate, ACVP
U. S. Army Medical Research Institute of Infectious Disease
Bldg. 1425
Fort Detrick, MD 21702-5011
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Case I - X5893-3 (AFIP 2579514)

Signalment: Adult, male, common pintail duck (Anas acuta acuta).
History: This duck was housed in a large outdoor enclosure with several other male pintails. The bird was noted to have a drooping left wing and apparent inability to use this wing. Physical examination revealed severe swelling of the carpal joint of this wing associated with the presence of yellow caseous material. The wing was amputated at the distal radius and ulna and submitted for histopathologic examination.
Gross Pathology: There was diffuse swelling (up to 3 times normal) of the soft tissues surrounding the carpal and carpometacarpal joints. Caseous yellow nodules measuring up to 1 cm diameter were scattered throughout the joints and periarticular soft tissues.
Laboratory Results: See contributor's comments.
Contributor's Diagnoses and Comments: Joint (carpus), arthritis, granulomatous and heterophilic, septic, severe.
Bone, carpal, osteomyelitis, granulomatous and heterophilic, septic, moderate.
Bone marrow, hyperplasia, myeloid, moderate.
Etiology: Staphylococcus aureus
Septic arthritis is a relatively common problem in captive collections of waterfowl. The joints of the feet are most commonly affected and Staphylococcus aureus is the etiologic agent usually isolated from these lesions. In our experience at the National Zoo, birds with chronic infections often die from acute staphylococcal septicemia. Hepatic, splenic and/or renal amyloidosis are also common sequelae secondary to chronic inflammation.
This bird died 2 weeks following the wing amputation. Death was attributed to a combination of hepatic failure from severe amyloidosis and terminal bacterial septicemia. At necropsy, pure cultures of Staphylococcus aureus were isolated from the wing stump, liver, and heart blood.
AFIP Diagnosis: Wing, carpus: Arthritis, osteomyelitis and tenosynovitis, necrotizing, granulomatous and heterophilic, multifocal to coalescing, severe, with granulation tissue, periosteal hyperostosis, and colonies of cocci, pintail duck (Anas acuta acuta), avian.
Conference Note: The incidence of staphylococcosis among captive Anseriforms is relatively high. In free living waterfowl, staphylococcosis tends to be sporadic and is not responsible for large numbers of mortalities. The major pathological findings include: endocarditis, arthritis, tenosynovitis, osteomyelitis, peritonitis, hepatitis, splenitis, nephritis, pneumonia, encephalomyelitis, and enteritis. The most common route of infection in Anseriforms appears to be through skin wounds, with initial infection of subcutaneous or muscular tissues, followed by dissemination through the blood stream to other organs and tissues. A higher frequency of infection is observed in males especially during the breeding season and winter; this is probably related to their naturally aggressive breeding behavior and frequent fighting.
Amyloidosis is a common finding in Anseriforms and is often secondary to chronic infections, such as tuberculosis, aspergillosis or other persistent bacterial infection.
Contributor: National Zoological Park, Smithsonian Institution, Washington, DC 20008.
1. Dias JLC and Montali RJ: Staphylococcosis in captive exotic waterfowl. Avian Pathol 23:659-669, 1994.
2. Gerlach H: "Bacteria:, In: Ritchie BW, Harrison GJ, and Harrison LR (eds.), Avian Medicine: Principles and Application, Wingers Publishing, Inc., Lake Worth, FL, pp. 965-968, 1994.
3. Halliwell WH and Graham DL: "Bacterial diseases of birds of prey", In: Fowler ME (ed): Zoo & Wild Animal Medicine, Second Edition, WB Saunders Co., Philadelphia, pp. 415-416, 1986.
International Veterinary Pathology Slide Bank: None.

Case II - 96-1515 (AFIP 2551544)

Signalment: 4-month-old, female, nude mouse (Nu/JNu).
History: This mouse was housed with APOe (deficiency of apolipoprotein E) mice suspected to have pneumocystosis. A research technician placed the nude mouse in the colony to act as a sentinel mouse.
Gross Pathology: The perineum was stained with dried feces and fluid. Well developed pus was present in the left uterine horn. The gastrointestinal tract was distended with gas.
Laboratory Results: Enterobacter spp. cultured from reproductive tract. An acute multifocal neutrophilic hepatitis and moderate Pneumocystis pneumonia were present.
Contributor's Diagnosis and Comments: Acute to subacute suppurative and necrotizing placentitis and metritis with fetal death (coagulation necrosis) and intralesional bacteria.
A literature search failed to reveal information on spontaneously occurring suppurative and necrotizing placentitis in mice induced by Enterobacter spp. It has been shown that gram-negative bacteria such as Klebsiella oxytoca, K. pneumonia, Escherichia coli, and Enterobacter sp. can cause suppurative utero-ovarian infections in nongravid mice (Rao, 1987). Pasteurella pneumotropica, frequently found in the upper respiratory tracts of normal mice, has been demonstrated to cause a necrotizing suppurative metritis and fetal resorption, similar to the lesions in the case presented here (Ward, 1978; Casillo, 1972). Mice inoculated experimentally with Brucella abortusor E. coli endotoxin can develop a necrotizing placentitis (Tobias, 1993;McKay, 1963). The pathogenesis of the placentitis shown here is uncertain, but could result from an ascending vaginal infection from intestinal flora or could be the result of a septicemia (this mouse also had a mild, acute, neutrophilic hepatitis). It has been speculated that the local immune suppression of pregnancy may allow bacteria to proliferate preferentially in the placenta (Tobias, 1993). The immunodeficiency in this nude mouse was likely a predisposing factor to infection.
AFIP Diagnosis: 1. Uterus, gravid: Metritis and placentitis, necrotizing, acute, diffuse, severe, with vasculitis and numerous intracellular and extracellular bacilli, nude mouse (Nu/JNu), rodent.
2. Fetus: Autolysis, diffuse, moderate.
3. Fetus, lung: Numerous squamous epithelial cells and meconium.
4. Fetus, nasal mucosa, dermis, dental pulp, tongue: Necrosis and acute inflammation, multifocal, mild.
Conference Note: The conference participants agreed with the contributor's diagnosis and comments. The death of the fetus was attributed to loss of blood supply due to placental vasculitis and necrosis. The presence of squamous epithelial cells and meconium within fetal lungs indicates fetal stress. Enterobacter sp. are occasionally reported to cause placentitis in horses and sporadic cases of mastitis and urinary tract infections in dogs.
In addition to those listed by the contributor, the following bacteria have been isolated from the reproductive tracts of female mice that aborted: Streptococcus sp., Proteus mirabilis, and Proteus vulgaris.
Contributor: The Ohio State University, Department of Veterinary Biosciences, 1925 Coffey Rd., Columbus, OH 43210.
1. Casillo S, Blackmore DK: Uterine infections caused by bacteria and mycoplasma in mice and rats, J Comp Pathol 82:477-482, 1972.
2. McKay DG, Wong TC: The effect of bacterial endotoxin on the placenta of the rat. Am J Pathol 42(3):357-377, 1963.
3. Rao GN, Hickman RL, Seilkop SK, Boorman GA: Utero-ovarian infection in aged B6C3F1 mice. Lab Anim Sci 37(2):152-158, 1987.
4. Tobias L, Cordes DO, Schurig GG: Placental pathology of the pregnant mouse inoculated with Brucella abortus Strain 2308. Vet Pathol 30:119-129, 1993.
5. Ward GE, Moffatt R, Olfert E: Abortion in mice associated with Pasteurella pneumotropica. J Clin Microbiol 8(2):177-180, 1978.
6. Hong CB, et al: Etiology and pathology of equine placentitis. J Vet Diag Invest 5(1):56-63, 1993.
International Veterinary Pathology Slide Bank: None.

Case III - H96-1183 G 96-1210 (AFIP 2551540)

Signalment: Black-gloved wallaby (Macropus irma).
History: The animal was an adult wild wallaby found blind on a farm. It was euthanized and necropsied.
Gross Pathology: Apart from superficial predator damage, the animal was otherwise normal and well muscled. Blood was submitted for serology; brain and eye were submitted for virus isolation.
Laboratory Results: See below.
Contributor's Diagnosis and Comments: Choroiditis, non-suppurative, moderate, diffuse. Wallal virus infection.
The presenting history and clinical signs of this case were suggestive of "choroid blindness", a disease recently shown to be due to infection with orbiviruses belonging to the Wallal and Warrego serogroups. The histological findings of a diffuse non- suppurative choroiditis and a moderate, diffuse, non-suppurative encephalitis, also present in this case, were strongly supportive of this diagnosis. Testing at the Australian Animal Health Laboratories (AAHL) demonstrated an antibody response in blood; Wallal virus was isolated from samples of eye and brain from this case.
Recent and continuing outbreaks of blindness in various species of kangaroo across vast areas of central and western Australia have been attributed to Wallal virus infection. The species commonly affected include western grey kangaroos (Macropus fuliginosus), eastern grey kangaroos (Macropus giganteus), red kangaroos (Macropus rufus) and euros (Macropus robustus). Typically, affected animals are found blind and stumble into bushes and other objects but otherwise are generally able to hear, move, feed, and maintain body condition.
Misadventure, injury and drowning are common causes of death. As in the present case, blindness is due to severe necrotizing retinitis, choroiditis, atrophy of optic nerves, and mild non-suppurative encephalitis.
Field and laboratory investigations carried out by the various States' Departments of Conservation and of Agriculture isolated orbiviruses of the Wallal serogroup from tissues taken from various affected kangaroos, particularly from eye, brain and blood. AAHL has identified orbivirus belonging to the Wallal virus serogroup in whole blood and sera. Polymerase chain reaction (PCR) has been used to confirm the presence of Wallal serogroup virus in the eyes and brains of affected cases. PCR has demonstrated the same virus in Culicoides dycei and C. austropalpalis. Indirect immunofluorescence testing has been used to demonstrate reactions to Wallal serogroup in the affected retinas of a number of cases. Grey kangaroos inoculated with Wallal virus developed clinical and pathological evidence of the disease after incubation periods of about 4 to 5 weeks. The lesions in the retinas of their eyes were confirmed at AAHL as specific to an orbivirus of the Wallal serogroup by PCR and immunofluorescence.
AFIP Diagnosis: Eye: Choroiditis, lymphocytic, diffuse, severe, with moderate anterior uveitis, retinitis, retinal detachment and intra-ocular fibrinocellular exudate, black-gloved wallaby (Macropus irma), marsupial.
Conference Note: The conference participants agreed with the contributor's diagnosis. Differential diagnosis for this lesion includes viral infection and autoimmune reaction. The distribution of these lesions is interesting. Many orbiviruses cause more generalized, often vascular, lesions. Other orbiviruses of veterinary importance include: bluetongue virus, epizootic hemorrhagic disease of deer virus, African horse sickness virus, Palyam virus, Ibaraki virus, and equine encephalosis virus.
Contributor: Murdoch University, School of Veterinary Studies, Murdoch, W.A., 6150, Australia.
International Veterinary Pathology Slide Bank: None.
1. Blacksell SD, Lunt RA, White JR: A rapid indirect ELISA for the serogrouping of Australian orbiviruses. Journal of Virological Methods 49:67-78, 1994.
2. Durham PJK, Finnie JW, Lawrence DA, Alexander P: Blindness in South Australian kangaroos. Australian Veterinary Journal 73:111-112, 1996.
3. Hooper P: Blind ‘roo epidemic. Microbiol Australia 17:22, 1996.
4. Fenner FJ, et al. (eds): Veterinary Virology, Second edition, Academic Press, pp. 537-552, 1993.

Case IV - 96L-107 (AFIP 2552479)

Signalment: A 7-month-old female marmoset.
History: First seen 7-1-96. Initially exhibited partial closure of left eye, with a pinpoint pupil and excessive lacrimation. Treated with Baytril. 9-1-96: Left eye still inflamed with development of a small yellow pustule by left eye. Betsolan added to treatment. 12-1-96: Still jumping about and scratching left eye area. Betsolan drops stopped; Neobiotic ointment dispensed and Betsolan injection given. 13-1-96: Condition worse - several skin lesions on left side of face and head. Trauma from scratching or pathological process?
Gross Pathology: Moist matted fur around the facial and neck region and dried exudate around the left eyelids. No other significant findings.
Laboratory Results: Sections of cerebrum reacted positively for herpes simplex virus types I and II when stained with an HRP-linked antibody against human herpes virus (Dakopatts B114).
Contributor's Diagnosis and Comments: Necrotizing meningoencephalitis caused by herpesvirus infection.

AFIP Diagnosis: Brain: Meningoencephalitis, necrotizing, subacute, multifocal, moderate to severe, with astrocytosis, multifocal hemorrhage, ventriculitis, vasculitis, and neuronal and astrocytic eosinophilic intranuclear inclusion bodies, marmoset, primate.
Conference Note: The lesions are consistent with herpes simplex virus infection. Marmosets are susceptible to both herpes simplex and herpes T infection. Both viruses cause systemic infection with similar gross and microscopic lesions. Encephalitis has not been described in Herpesvirus T infection but this would not be a reliable criterion on which to base the differentiation of the two diseases.

Herpes simplex infection is generally acquired from humans, the natural reservoir. Human to monkey or monkey to monkey transmission can occur via contact with active lesions. Lesions may be localized or generalized. The most characteristic gross lesions are discrete ulcers, necrotic plaques, and erosions or ulcers of the oral mucous membranes and at the mucocutaneous junction of the lips. Conjunctivitis is frequently present. Internally, foci of necrosis can be seen in most organs (i.e., liver, adrenal, spleen, lung, lymph nodes, and occasionally, kidneys). The brain of affected animals is usually grossly normal. Important histologic lesions include oral, lingual, labial, or genital vesicles and ulcers, conjunctivitis, keratitis, necrotizing meningoencephalitis, and focal necrosis in visceral organs. Intranuclear inclusion bodies and multinucleate syncytial cells are characteristic findings. The most striking feature herpes simplex encephalitis is necrosis of neurons, particularly of the temporal cerebral cortex and the thalamus. Intranuclear inclusions may be found in neurons and astrocytes.
Marmosets, owl monkeys, tree shrews, lemurs, and tamarins are susceptible to generalized herpes simplex infection. Chimpanzees and gibbons can be infected, but lesions usually remain confined to the skin, oral cavity, external genitalia, and conjunctiva. Fatal encephalitis is rarely reported in gibbons.
Herpesvirus simplex was also recently diagnosed in an African pygmy hedgehog. See 1996/97 Wednesday Slide Conference 9, Case 1 for more details.
Contributor: University of Liverpool, P.O. Box 147, Liverpool L69-2BX, UK.

1. Hunt RD: Herpesvirus simplex Infection. In: Monographs on the pathology of laboratory animals: Nonhuman primates I, Jones TC, et al (eds), Springer-Verlag, pp. 82-86, 1993.
2. Baskin GB: Pathology of Nonhuman primates. 42nd Annual Pathology of Laboratory Animals Course, Bethesda MD, 1995.
International Veterinary Pathology Slide Bank: None.
Lance Batey
Captain, VC, USA
Registry of Veterinary Pathology*
Department of Veterinary Pathology
Armed Forces Institute of Pathology
(202)782-2615; DSN: 662-2615
* The American Veterinary Medical Association and the American College of Veterinary Pathologists are co-sponsors of the Registry of Veterinary Pathology. The C.L. Davis Foundation also provides substantial support for the Registry.
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