AFIP Wednesday Slide Conference - No. 16

5 February 1997

Conference Moderator: Dr. John D. Strandberg
Diplomate, ACVP
Johns Hopkins University
Division of Comparative Medicine
720 Rutland Ave.
Baltimore, MD 21205

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Case I - 95-1453-3 and 95-1453-2 (AFIP 2558111), 2 histoslides.

Signalment: Puffin (Fratercula corniculata), young age, body weight approximately 50 gm.

History: Sixteen horned puffin chicks of various pre-fledgling ages were caught in Alaska and transported to a zoological park in August of 1995. Six of the sixteen chicks died within a five day period beginning two days after their arrival. The chicks had been fed a diet of thawed frozen ocean silver sides, and were not supplemented with vitamins. Clinical signs were non-specific from chicks that were found dead or euthanized in extremis.

Gross Pathology: No significant lesions.

Laboratory Results: No data was available for hematology or clinical biochemistry. Toxicology screens for carbamate and organophosphate insecticides were negative on proventricular ingesta from two birds. Bacterial culture of lung, liver, and intestinal contents from two birds grew (Staphylococcus sp. and Enterococcus sp., both of which were considered contaminants, and large numbers of Escherichia coliwere cultured from the small intestines only.

Contributor's Diagnosis and Comments:
1. Multifocal, acute, moderate myocardial necrosis-vitamin E responsive disease.
2. Liver-centrilobular necrosis, multifocal to bridging, moderate.

Multifocal myocardial necrosis without mineralization was present in five of the six birds that died. Differentials included coccidiostats, Cassia intoxication, gossypol, and vitamin E responsive disease. The diet of marine fish without vitamin supplementation in the absence of exposure to other known toxins made vitamin E deficiency the most likely etiology. The centrilobular hepatic necrosis was attributed to the myocardial lesion and secondary centrilobular hypoxia. Microsporidia were in the GI tract of these puffins and infection with microsporidium has been associated with hepatic necrosis in love birds. In love birds, the organisms were present in the areas of hepatic necrosis, but no organisms were present in puffin liver sections stained with H&E, Gram stain, or Warthin-Starry. All chicks were given oral itraconazole at a dose of 1 mg/100 gm of bodyweight daily, beginning three days prior to transport. Itraconizole is associated with hepatic failure and is contraindicated in human patients that have hepatic problems. Although this is a possible etiology for the liver lesion, we could find no reference that described the liver lesions associated with this drug.

AFIP Diagnosis: 1. Heart, myocardium: Degeneration, acute, multifocal to coalescing, severe, horned puffin (Fratercula corniculata), avian.
2. Liver: Necrosis, coagulative, centrilobular, bridging, diffuse, with hepatocellular vacuolar change (lipid type).

Conference Note: The conference participants agreed with the contributor's diagnosis. Little is written concerning Vitamin E deficiency in non-domestic avian species. In domestic poultry, hypovitaminosis E produces encephalomalacia, exudative diathesis, and muscular dystrophy in chicks; enlarged hocks and dystrophy of the gizzard musculature in turkeys; and muscular dystrophy in ducks. Encephalomalacia has also been reported in turkey poults. Experimental intoxication with cobalt, an essential trace element and component of vitamin B12, is reported to cause skeletal muscle degeneration and hepatic necrosis.

Vitamin E is one of several essential nutrients that act as natural antioxidants and prevent oxidative damage to cell membranes. Deficiency may result in necrosis. Although vitamin E deficiency manifests itself in a wide variety of diseases in numerous species, the hallmark is necrosis due to oxidative damage.

Vitamin E is composed of a group of closely related tocopherols and tocotrienols, of which alpha tocopherol is the most active and widely available. It is abundant in many foods, including vegetables, nuts, grains, dairy products, fresh fish, and red meats. It is the only lipid soluble antioxidant; absorption requires normal biliary and pancreatic functions. Diets high in polyunsaturated fats cause a corresponding increase in requirement for vitamin E, and may precipitate a state of hypovitaminosis E. Following absorption in the intestine, tocopherols are transported in the blood as chylomicrons, which rapidly equilibrate with plasma lipoproteins, particularly low density lipoproteins. Vitamin E is stored throughout the body, primarily in fat, liver, and muscle. Vitamin E scavenges free radicals formed in redox reactions (both intra and extracellularly) and is important in termination of free radical-generated lipid peroxidation chain reactions, particularly in cellular and subcellular membranes rich in polyunsaturated lipids.

Contributor: North Carolina State University, College of Veterinary Medicine, 4700 Hillsborough St., Raleigh NC, 27606, USA.

1. Powell S, et al: Microsporidiosis in a lovebird. J Vet Diagn Invest 1:69-71, 1989.
2. Campbell G, Montali RJ: Myodegeneration in captive brown pelican attributed to vitamin E deficiency. J Zoo Wildl Med 11:35-40, 1980
3. American Hospital Formulary Service, Editor, McEvoy G., p. 93, 1996.
4. Dierenfeld ES: Vitamin E deficiency in zoo reptiles, birds, and ungulates. J Zoo Wildl Med 20:3-11, 1989.
5. Jubb KVF, Kennedy PC, Palmer N (eds): Pathology of Domestic Animals, 4th ed., Vol. 1., Academic Press, pp. 228-235, 1993.

6. Cotran RS, Kumar V, Robbins SL (eds): Robbins Pathologic Basis of Disease. 5th ed., W.B. Saunders Co., pp. 418-419, 1994.
7. Geraci JR, St. Aubin DJ: Nutritional disorders of captive fish-eating animals. In: Montali RJ, Migaki G (eds): Comparative Pathology of Zoo Animals. Smithsonian Institution, Washington, DC, pp. 41-49, 1980.
8. Nichols DK, Montali RJ: Vitamin E deficiency in captive and wild piscivorous birds. Proc. First Int. Conf. Zool. Avian Med., Turtle Bay, Hawaii, pp. 419-421, 1987.
9. Diaz GJ, et al: Lesions in Broiler Chickens following experimental intoxication with cobalt. Avian Dis 38:308-316, 1994.

International Veterinary Pathology Slide Bank:
Laser disc frame #3549-50, 4564-5.

Case II - 9235338 (AFIP 2547627)

Signalment: An approximately 16-month-old, female, Long Evans rat.

History: This control rat died approximately 14 months after initiation of a 2-year study.

Gross Pathology: Skin/subcutis had a large (63 x 30 x 16 mm), ellipsoid, firm, multilobular mass within the left side of the ventral aspect of the abdomen. The liver was markedly enlarged and contained numerous, tan, pale, firm foci, as well as raised nodules (6-13 mm diameter), in multiple lobes. The spleen had marked diffuse enlargement.

Laboratory Results: None.

Contributor's Diagnosis and Comments:
1. Skin and subcutis: Histiocytic sarcoma.
2. Kidney: Hyaline droplets, intracytoplasmic, proximal tubules, moderate, multifocal.

Skin and subcutis: Dermal and subcutaneous architecture is effaced by an expansile infiltrating oval mass (15 x 20 mm) composed of a population of non-uniform discrete cells which generally contain a single, centrally placed, non-lobed euchromatic nucleus surrounded by granular eosinophilic cytoplasm. The 10 to 20 m diameter neoplastic cells, which isolate adnexal structures, dermal collagen bundles, blood vessels, and skeletal muscle, form solid sheets which are necrotic in small focal areas. Other small focal areas contain spindle cells arranged into slight whirling patterns. Low to moderate numbers of multinucleated giant cells (Langhan's type) are scattered among the population of histiocyte-like cells.

Kidney: Between 1/3 and 2/3 of proximal tubules are lined by epithelial cells that are laden with intracytoplasmic, brightly eosinophilic, partially refractile hyaline droplets. The 1 m diameter droplets have fused to form large (up to 15 m diameter) globules within numerous cells. Some sections of kidney have extracapsular foci of histiocytic sarcoma.

In addition to the neoplastic cell mass within the subcutis, similar neoplastic cell infiltrates were observed within liver, spleen, and mesenteric lymph node. The neoplasm was possibly multicentric because a primary site of origin was not discernible. Because the neoplasm had histiocytic and sarcomatous features, including the presence of multinucleated giant cells, the following differential diagnoses were considered: malignant fibrous histiocytoma, malignant pleomorphic fibrous histiocytoma, and histiocytic sarcoma. The diagnosis of histiocytic sarcoma was favored because spindle cell features, which would be diagnostic for the other differential diagnoses, were focal and minimal. Additionally, the predominant histiocytic morphology was consistent with that of histiocytic sarcoma, including the presence of intracytoplasmic eosinophilic granular material within neoplastic cells and renal tubular epithelial cells. Although common locations for histiocytic sarcoma have been identified as the uterus of Sprague- Dawley rats and the skin/subcutis of Wistar rats, common locations for the neoplasm have seemingly not been reported for Long-Evans rats.

The presence of intracytoplasmic hyaline droplets within proximal tubular epithelial cells of the kidney has been reported to occur in 96% of histiocytic sarcoma cases in rats (Sprague-Dawley, Osborne-Mendel, Fischer 344) and in 55% of such cases in mice (B6C3F1). The droplets are reportedly positive by immunohistochemistry for lysozyme but negative for 1-antitrypsin, 2 -globulin, rat or mouse immunoglobulin, and albumin. A mechanism has been proposed whereby malignant histiocytes secret lysozyme which is ultimately filtered in the kidney and reabsorbed into proximal tubule cells, where it accumulates. The process is reportedly independent of the hyaline droplet nephropathy involving 2 -globulin in the male rat.

AFIP Diagnosis:
1. Haired skin and subcutis: Sarcoma, histiocytic, Long Evans rat, rodent.
2. Kidney, capsule: Sarcoma, histiocytic.
3. Kidney, proximal tubules: Intracytoplasmic hyaline droplets, diffuse, numerous.

Conference Note: The conference participants agreed with the contributor's diagnoses. Many participants believed there was a mild diffuse increase in mesangial matrix within renal glomeruli. An immunohistochemical procedure for lysozyme failed to stain the hyaline droplets in this case.

Contributor: Pfizer Central Research, Drug Safety Evaluation, Eastern Point Road, Groton, CT 06340.

1. Carlton WW: Neoplasms of Rodents. In, Pathology of Laboratory Animals Proceedings, 41st annual meeting. 1994.

2. Greaves P, and Faccini JM: Rat Histopathology. A Glossary for Use in Toxicity and Carcinogenicity Studies. Elsevier, Amsterdam, pp. 5-45, 1984.
3. Greaves P, Martin JM, and Masson MT: Spontaneous rat malignant tumors of fibrohistiocytic origin: an ultrastructural study. Vet Pathol 19:497-505, 1982.
4. Hard GC, and Snowden RT: Hyaline droplet accumulation in rodent kidney proximal tubules: an association with histiocytic sarcoma. Toxicol Pathol 19:88-96, 1991.

International Veterinary Pathology Slide Bank: None.


Case III - 96-5025 (AFIP 2549635), 1 photo

Signalment: Seven-week-old Rhodesian Ridgeback dogs, both male and female.

History: Breeder noticed dilution of coat color in 2 of 3 pups at birth (one female & one male affected). At two weeks of age pups with dilute coats had increased ataxia when compared to the normal littermate. Ataxia progressed to the point where pups spent the majority of time in lateral recumbency and had little control of their heads and necks. Spastic limb movements at rest and horizontal nystagmus were also noted. Affected pups were aware of surroundings and responsive to stimuli but ate only if assisted. Cranial nerves and spinal reflexes were recorded as normal.

Gross Pathology: Both affected pups had fawn haircoats and blue to silver-gray irises. Brain and cerebellar sizes were equivalent to the unaffected littermate.

Laboratory Results: None.

Contributor's Diagnosis and Comments: Severe, regionally extensive Purkinje cell necrosis, with atrophy of the molecular and granular cells layers.

Inherited cerebellar degeneration, often termed abiotrophy, has been reported in numerous dog breeds including the Beagle, Samoyed, Irish Setter, Kerry Blue Terrier, Australian Kelpie, Rough-coated Collie and Rhodesian Ridgeback. Histopathological changes in Rhodesian Ridgeback dogs most resemble those seen in Irish Setters, but the association with coat color dilation is unique to the Rhodesian Ridgeback. The litter whose tissues were submitted had a similar pedigree to the litter profiled by Cheiffo, et al and had similar cerebellar lesions, with increased severity in the lateral lobes and vermis, less so in the flocculonodular lobes and the uvula.

AFIP Diagnosis: Brain, cerebellum: Atrophy of germinal, molecular, granular, and Purkinje cell layers, segmental, with Purkinje cell degeneration, necrosis, and loss, Rhodesian Ridgeback, canine.

Conference Note: The conference participants agreed that the lesions are consistent with a diagnosis of cerebellar abiotrophy. Cerebellar cortical abiotrophy is perhaps the most common nervous system abiotrophy in domestic animals. Purkinje cells appear to be quite susceptible to this type of degeneration. The viability of the granule cell neuron is dependant on a synaptic relationship with the Purkinje dendrite, and loss of Purkinje neurons often results in a secondary depletion of the granule cell neurons. It is interesting to note the segmental distribution of lesions, with the vermis being particularly affected. Cerebellar atrophy (abiotrophy) has been described in numerous species, including horses, sheep, cattle, swine, and numerous breeds of dogs. In addition to the breeds listed above, cerebellar abiotrophy has been described in the Bernese Mountain Dog, Finnish Terrier, and Airedale. As noted by the contributor, canine cerebellar abiotrophy with coat color dilution has only been described in the Rhodesian Ridgeback. Hereditary syndromes including neurological disease and color coat dilution have been reported in several species, including the chicken, mink, cat, and mouse. In experimental studies with mice, genetic deletion at a single locus, termed D locus, results in defects of several alleles, producing color coat dilution and neurologic disease.

Histologically, the distribution of melanin within hairs of affected dogs resembles that of other mammals with the color dilution phenotype. Melanin does not appear to be reduced in amount but is clumped into large, unevenly distributed macromelanosomes, that apparently have less effect on light absorption.

Contributor: University of Pennsylvania, Laboratory of Pathology, School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104.

1. Chieffo C, Stalis IH, Van Winkle TJ, Haskins ME, Patterson DF: Cerebellar Purkinje's Cell Degeneration and Coat Color Dilution in a Family of Rhodesian Ridgeback Dogs. J Vet Int Med, 8(2):112-116, 1994.
2. de Lahunta A: Abiotrophy in domestic animals: A review. Canadian J Vet Res, 54:65-76, 1990.
3. Yasuba M, Ikimoto K, Iida M, et al. Cerebellar cortical degeneration in beagle dogs. Vet Pathol, 25:315-317, 1988.
4. Summers BA, Cummings JF, de Lahunta A: Neuronal Abiotrophy, InVeterinary Neuropathology. Mosby-Year Book Inc., St. Louis, pp. 300-305, 1995.
5. Jubb KVF, Kennedy PC, Palmer N: Pathology of Domestic Animals, 4th ed., Vol. 1, Academic Press, pp. 283-284, 1993.
International Veterinary Pathology Slide Bank: None.


Case IV - X18389 95 (AFIP 2550406), 2 photos

Signalment: 5-month-old, female, Blue Iris mink (Mustela vison).

History: Over a one week period a mink rancher had lost 15 juvenile mink from a population of 600 animals. This case was one of the four mink submitted for necropsy. All mink died shortly after being noticed lethargic. Morbidity and mortality quickly declined following the administration of an antibiotic in the feed.

Gross Pathology: Necropsy findings were similar in all the mink. All four mink had irregularly shaped pale areas involving a large portion of one or more liver lobes. These areas were usually emphysematous, had hyperemic margins and the overlying capsular surface was covered by fibrin. The fibrin was often abundant and adherent to surrounding structures (abdominal wall, diaphragm, omentum, surrounding intestines, etc). The lungs of some of the mink had a few to several dark red foci with pale centers, up to 1 cm in diameter, scattered throughout.

Laboratory Results:
1) Aerobic bacteriology - no microbial growth in lung, spleen or liver.
2) Anaerobic bacteriology - Fusobacterium necrophorum and Clostridium spp.
Contributor's Diagnosis and Comments:
1. Hepatitis, necrotizing and emphysematous, focally extensive, acute, severe, with intralesional filamentous bacteria, etiology - Fusobacterium necrophorum.
2. Peritonitis, fibrinous, acute with intralesional filamentous bacteria.

Necrobacillosis occurs in a wide range of animals (including humans) and refers to tissue damage caused by infection with Fusobacterium necophorum. The lesions are typically pyonecrotic and can affect many body sites; however hepatic abscesses in cattle, foot rot in cattle and sheep, and calf diphtheria are some of the more common manifestations. In most infections involving Fusobacterium species, one or more additional anaerobic or aerobic bacteria can be recovered.

The lesions in this outbreak of necrobacillosis in mink were similar to those reported in the early 1960's. The hepatic lesions consist of focally extensive areas of coagulative necrosis containing myriads of gram-negative filamentous bacteria. There is prominent hyperemia and hemorrhage in the hepatic parenchyma immediately surrounding the lesions with occasional vascular thrombosis. Relatively few leukocytes are evident at the interface of the necrotic and viable tissue. Some of the mink had multifocal lung lesions which were similar to those in the liver, ie. areas of coagulative necrosis with myriads of intralesional gram-negative filamentous organisms. The emphysema in many of the lesions in this outbreak may be the result of the co-infection with Clostridium spp (ie Clostridium spp cultured anaerobically from some cases and small numbers of gram-positive rods are present in the emphysematous vacuoles in the necrotic areas of liver).

AFIP Diagnosis: Liver: Hepatitis, necrotizing, acute, focally extensive, severe, with hemorrhage, emphysema, fibrinous capsulitis, and numerous filamentous bacteria, Blue Iris mink (Mustela vison), mustelid.

Conference Note: The conference participants agreed with the contributor's diagnosis. Since no Fusobacterium spp. have been reported to be gas producers, a second bacterium such as Clostridium perfringens is the most likely cause of the emphysema.

Fusobacterium necrophorum is a gram-negative, non-sporulating, filamentous, obligate anaerobe that is part of the normal gut flora of many species. It has little ability to invade normal epithelium and is thus an opportunistic pathogen, invading sites affected by trauma, chemical damage or infection by other agents. In infected tissues, the organism is usually seen as long, filamentous rods, but shorter, and even coccoid, forms may be observed. The rod forms are 1 micron in diameter and may be in excess of 100 microns in length. The organism is a member of the family Bacteroidiaceae. The ability of F. necrophorum to produce disease can be greatly increased experimentally by co-infection with a variety of agents.

F. necrophorum produces a variety of exotoxins and endotoxins, whose exact roles in the pathogenesis of necrobacillosis are not completely understood. The exotoxins include leukocidin, hemolysin, a hemagglutinin and a cytoplasmic toxin, all of which probably enhance the necrotizing ability of the organism.

Contributor: Department of Pathology and Microbiology, Atlantic Veterinary College, 550 University Ave, Charlottetown, P.E.I., CANADA C1A-4P3.

1. Gorham J: Mink diseases: Spherophorus necrophorus infection. Natl-Fur- News 34: 21 & 28, 1963.
2. Jang SS, and Hirsch DC: Characterization, distribution, and microbiological association of Fusobacterium spp. in clinical specimens of animal origin. J Clin Microbiol 32:384-7, 1994.
3. Monlux WS, and Rhoades KR: Spherophorus necrophorus infection in mink. Iowa State Vet 23:144-145, 1960-61.

International Veterinary Pathology Slide Bank:
Laser disc frame #04081, 20437.

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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