AFIP Wednesday Slide Conference - No. 11
November 24, 1999
- Conference Moderator:
COL Michael J. Topper
Division of Pathology
Walter Reed Army Institute of Research
Washington, DC 20307
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- Case I - 99-8265 (AFIP 2694722)
- Signalment: 2-yr-old, female, domestic shorthaired
cat, Felis domesticus.
- History: The cat developed dyspnea within 48 hours
of being placed in a boarding facility. The owner claimed that
the animal exhibited no clinical abnormalities prior to this
sudden onset of respiratory distress. Radiographs revealed a
diffuse interstitial pattern of pulmonary infiltration. The animal
died before further clinical work-up could be pursued.
- Gross Pathology: Necropsy was performed by the referring
veterinarian. The lungs were described as diffusely red, meaty
and heavy. No other abnormalities were noted in the carcass,
and the lung was the only organ sampled for microscopic exam.
- Contributor's Diagnosis and Comments: Severe, subacute
to chronic, diffuse, proliferative interstitial pneumonia with
Etiology: Toxoplasma gondii.
- Sections have been cut from each of the 3 lung samples submitted,
so there is some variability between slides. There is remarkable
proliferation of type II pneumocytes, resulting in an adenomatous
appearance to the tissue. Many protozoal organisms are visible.
These tachyzoites are most prominent in macrophages and multinucleate
giant cells but can also be found within respiratory epithelial
cells. The alveolar septa and pleura are thickened, and a lymphoplasmacytic
infiltrate is evident in this interstitial compartment. Many
bronchoalveolar spaces are filled with necrotic cellular debris,
which includes tachyzoite-laden cells.
- The cat is the definitive host for Toxoplasma gondii,
which utilizes an enteroepithelial life cycle to produce oocysts
within this host. However, extraintestinal organisms can be found
within the cat (and a wide variety of other hosts, including
humans) in the form of intracellular tachyzoites and bradyzoites.
Cats may be infected transplacentally or orally (through ingestion
of food or water contaminated with sporulated oocysts, or by
eating tachyzoites and bradyzoites within the tissues of infected
intermediate hosts). Immunohistochemical staining of the lung
for Toxoplasma antigen was positive (test performed at Cornell
Veterinary Diagnostic Lab).
- Infection of cats is common, but the clinical outcome is
likely influenced by various factors such as the strain and number
of infectious organisms ingested, as well as the immune status
of the host. Fatal disease in adult cats is uncommon. Dyspnea,
as seen in this case, is one of the most common clinical signs
of postnatal toxoplasmosis. Toxoplasma-induced lesions are frequently
detected in the lung, liver, pancreas and lymph nodes and generally
have a necrotizing and granulomatous character. The FIV and FeLV
status of this cat is unknown and the possibility of concurrent
infection with viral respiratory pathogens such as calicivirus
and feline viral rhinotracheitis virus cannot be ruled-out.
- AFIP Diagnosis: Lung: Pneumonia, interstitial, proliferative,
diffuse, severe, with pleuritis and numerous intracellular protozoa,
domestic short hair, feline, etiology consistent with Toxoplasma
- Conference Note: Conference participants agreed that
the findings are consistent with Toxoplasma gondii. Other
organisms that were considered in the differential diagnosis
include: Neospora caninum, Sarcocystis sp., Trypanosoma sp.,
Leishmania sp., and Histoplasma capsulatum. In general, the most
difficult possibility to eliminate is Neospora caninum. Immunohistochemistry
and electron microscopy can differentiate the two organisms.
Ultrastructurally, Neospora has electron dense rhoptries, while
Toxoplasma has honeycomb-like or labyrinthine rhoptries. Also,
natural infection of cats with Neospora caninum has not been
- Toxoplasma gondii is an obligate intracellular parasite that
can infect all warm-blooded animals, but cats are the definitive
host (only cats excrete oocysts). The three infectious stages
are tachyzoites (rapidly proliferating, infect almost any cell),
bradyzoites (slowly proliferating encysted zoites) and sporozoites
(four per sporocyst, two sporocysts per sporulated oocyst). Both
Toxoplasma and Neospora oocysts require up to 3 days to sporulate
after they are shed, but Frenkelia, Sarcocystis and Cryptosporidium
are shed as sporulated oocysts.
- Contributor: College of Veterinary Medicine, Oregon
State University, Magruder Hall, Corvallis, OR 97331
- 1. Barker IK, Van Dreumel AA, Palmer N: The Alimentary System.
In: Pathology of Domestic Animals, 4th ed., vol. 2, eds. KVF
Jubb, PC Kennedy, Palmer N, pp. 308-310. Academic Press, San
Diego, CA, 1993
- 2. Dubey JP: Advances in the life cycle of Toxoplasma gondii.
Internat J for Parasit 28:1019-1024, 1998
- 3. Dubey JP, Lappin MR: Toxoplasmosis and Neosporosis. In:
Infectious Diseases of the Dog and Cat, ed. CE Greene, 2nd ed.,
pp. 493-509. WB Saunders, Philadelphia, 1998
- 4. Dubey JP, Lindsay DS, Speer CA: Structures of Toxoplasma
gondii tachyzoites, bradyzoites, and sporozoites and biology
and development of tissue cysts. Clin Microbiol Rev. 11(2):267-299,
- Case II - B99-9032 (AFIP 2693027)
- Signalment: Sprague Dawley rat (Rattus norvegicus),
young adult male.
- History: Rats had surgery for placement of bile duct
cannulae 7-10 days prior to sacrifice. These rats were supposed
to be used for a metabolism study involving bile excretion. Rats
were purchased from a commercial supplier after a surgical procedure
to allow sampling of bile outside the body. The bile duct had
been cannulated with small bore polyethylene tubing. The tubing
was anchored in place via a suture, then exteriorized through
the abdominal cavity and skin. The tubing then formed a loose
loop outside the body, passed back through the skin into the
abdominal cavity, and was anchored to empty into the duodenum.
There was a small connector in the tubing loop present outside
the skin that could be removed to sample bile. This connector
had a small opening in the center which was patent to allow bile
to flow freely. This surgical preparation was supposed to allow
bile to flow freely through the tubing and eventually return
to the duodenum. The exterior connector could be removed to take
a sample, then put back in place.
- Note: On each slide, a non-cannulated control rat
liver is included nearest the label for comparison with the cannulated
- Gross Pathology: Livers from cannulated rats were
enlarged and mottled. Livers from non-cannulated controls were
- Laboratory Results: The following clinical chemistry
findings were noted (presented as means for groups of n=5):
29 - 65
75 - 118
8 - 28
0 - 3
T Bili (mg/dl)
0.1 - 0.2
T Bile Acids (umol/L)
13.7 - 391.2
- Contributor's Diagnosis and Comments:
Moderate to severe necrotizing and proliferative cholangiohepatitis
- Etiology: Biliary obstruction from surgical cannulation
of the bile duct
- Multiple rats were used to prepare the submission, so the
degree of change present varies somewhat across the slides. In
general, there is inflammation centered on portal regions characterized
by infiltration of mononuclear cells and neutrophils. Inflammation
extends variably into adjacent hepatic parenchyma. Biliary ducts
and ductules are dilated and proliferative, with associated edema
and dilation of portal lymphatics. Many biliary epithelial cells
are hypertrophic and have prominent nuclei. In addition to the
biliary change, there is considerable hepatic necrosis in some
areas, with associated infiltration by neutrophils and other
inflammatory cells. The clinical pathology data is supportive
of the histopathology, and provides evidence for both hepatocellular
damage as well as cholestatic disease.
- Although the surgical cannulation procedure in these rats
was supposed to provide free flow of bile out the tubing and
back into the duodenum, we speculate that there was too much
resistance in the length of tubing present and a functional obstruction
resulted. Back-pressure from increased resistance likely produced
primary post-hepatic cholestasis and the biliary proliferation.
Associated with these events would have been secondary infection,
resulting in the inflammation and necrosis.
- AFIP Diagnosis:
- 1. Liver: Cholangiohepatitis, subacute, diffuse, moderate
with biliary hyperplasia, Sprague Dawley rat, rodent.
2. Liver: Hepatitis, necrotizing, suppurative, random, multifocal,
moderate, with bacilli.
3. Liver: Necrosis, coagulative, multifocal.
- Conference Note: The histologic lesions in this case
most likely resulted from two processes. The bile duct hyperplasia
is attributed to biliary obstruction secondary to cannulation.
The hepatitis and necrosis are most likely associated with a
secondary ascending bacterial infection and possibly septicemia.
Gram stains demonstrated large numbers of Gram negative bacilli
within the areas of necrosis.
- Clinical pathologic testing for hepatocellular damage is
conducted by measuring the soluble cytosolic enzymes that are
released into the blood with sublethal cell injury and necrosis.
Alanine aminotransferase and sorbitol dehydrogenase are considered
to be specific for detecting liver damage in the mouse. In this
case both were elevated. Aspartate aminotransferase was also
elevated; however, it is not considered to be liver specific.
The elevated total bilirubin is attributed to cholestasis.
Contributor: The Procter & Gamble Company, Miami Valley
Laboratories, PO Box 398707, Cincinnati, Ohio, 45239-8707.
- 1. Duncan JR, Prasse KW, Mahaffey EA: Veterinary Laboratory
Medicine, Clinical Pathology, 3rd ed., pp. 130-151. Iowa State
University Press, Ames, Iowa, 1994
- 2. Harada T, Enomoto A, Boorman GA, Moronpot RR: Liver and
Gallbladder. In: Pathology of the Mouse, eds. Maronpot RR, Boorman
GA, Gaul BW, pp. 125-126. Cashe River Press, Vienna, IL, 1999
- Case III - S94/99 (AFIP 2681357)
- Signalment: Guinea pig (Cavia aperea porcellus), 6-month-old,
- History: There was high mortality in a breeding colony
of a pet shop. No clinical signs were observed the day before
this animal's death.
- Gross Pathology: Post-mortem examination disclosed
focal alopecia, hyperkeratosis, panniculitis and acute congestion
of lung, liver and spleen.
Contributor's Diagnosis and Comments: Kidney: focal interstitial
nephritis, focal tubular degeneration, intratubular spherical
bodies; guinea pig (Cavia aperea porcellus), Cavioidea, Rodentia,
Mammalia; Cause: infection with Klossiella cobayae.
- Light microscopically, the animal showed a severe focal mononuclear
interstitial nephritis, accompanied by lymphohistiocytic perivascular
infiltrations and a focal increase of interstitial fibroblasts.
Besides, focal tubular degeneration and intratubular spherical
bodies of varying size were observed. According to their morphology,
the latter were identified as Klossiella cobayae development
stages. Additionally, focal interstitial pneumonia was diagnosed.
- In general, Klossiella infection, which has up to now been
demonstrated in equids, mice, bats, opossums, various rodents,
boa constrictors, and guinea pigs, remains asymptomatic. Clinical
and macroscopic alterations, represented by minute gray spots
in the renal cortex, are only observed in animals exposed to
massive stress (e.g., emaciation, transport, primary infections).
Klossiella are protozoans belonging to the subclass coccidia.
They have a direct life cycle. Ingestion of sporocyst leads to
the release of sporozoites, which circulate and parasitize the
endothelial cells of small vessels in kidney, lung, spleen, and
other organs. Primary schizonts develop predominantly in glomerular
endothelial cells. Merozoites invade epithelial cells of the
proximal convoluted tubules where secondary schizogony takes
place. Released merozoites undergo sexual stages in the loops
of Henle. Fertilized gametes develop into sporonts, which bud
to form sporoblasts. Each sporoblast undergoes successive division
to form sporocysts containing sporozoites, which are shed with
- AFIP Diagnoses:
- 1. Kidney, tubules: Intraepithelial and intraluminal protozoa,
with multifocal mild tubular epithelial degeneration, guinea
pig (Cavia aperea porcellus), rodent.
2. Kidney: Nephritis, interstitial, lymphoplasmacytic, multifocal,
minimal to mild.
- Conference Note: The histologic findings of multiple
stages of protozoan parasites within endothelium and tubules
in conjunction with the distinctive sporonts rimmed by budding
sporoblasts caused conference participants to agree with the
diagnosis of Klossiella cobayae. Toxoplasmosis and encephalitozoonosis
were discussed, but neither has life stages similar to the sporonts
Contributor: Institut für Veterinar-Pathologie, Universität
Leipzig, An den Tierkliniken 33, Leipzig, Germany 04103
- 1. Gardiner CH, Fayer R, Dubey JP: An Atlas of Protozoan
Parasites in Animal Tissues, 2nd ed., pp. 61-62. Armed Forces
Institute of Pathology, Washington, DC 1998
- 2. Maxie MG: The kidney. In: Pathology of Domestic Animals,
eds. Jubb KVF, Kennedy PC, Palmer N, vol. 2, 4th ed., p. 518.
Academic Press, San Diego, CA, 1993
- 3. Shadduck JA, Pakes SP: Protozoal and Metazoal Diseases.
In: Pathology of Laboratory Animals, eds. Benirschke K, Garner
FU, Jones TC, vol. II, p. 1609. Springer-Verlag, New York, 1978.
- Case IV - 95/351 (AFIP 2698315)
Signalment: 8-year-old, male, Rottweiler dog.
- History: In 1994, the dog had episodic weakness and
mild, generalized seizures. The first seizure coincided with
minor surgery two months before hospitalization. Immediately
after surgery a generalized seizure lasting for about three minutes
occurred. Diazepam was administered intravenously to alleviate
the symptoms. Analysis of a blood sample revealed marked hypoglycemia
(1.4 mmol/liter). Nine days later the dog was re-examined. No
new seizures had been observed, but the dog was generally depressed
and several episodes of weakness and muscle tremor had been noticed.
These clinical signs were preceded by periods of excitement.
- Blood analysis revealed hypoglycemia (1.7 mmol/liter) and
hyperinsulinemia (193 mU/liter). The condition was stabilized
and controlled for 46 days by means of prednisolone and a strict
diet. Two days after the owner ran out of prednisolone tablets,
several seizures occurred. Prednisolone treatment was reinstated
and the dose was increased. No new seizures had occurred five
days later. The dog was then anaesthetized and a coeliotomy was
- No gross abnormalities were identified in the pancreas, but
palpation revealed two tiny nodules (diameter 2-3 mm) in the
right lobe of the pancreas. The liver and spleen appeared normal.
A firm and irregular abdominal mass, thought to be a mesenteric
lymph node, was observed. This mass was excised and submitted
for histological examination. Since an obvious pancreatic tumor
could not be located, intravenous infusion of methylene blue
was performed. After 20 to 25 minutes, tiny nodules previously
not visible in the right lobe of pancreas became visible and
stained reddish-blue. No other color changes in the pancreas
or other organs were observed. A partial right lobe pancreatomy
was performed and the tissue was sent for histological examination.
Microscopic examination of pancreas and mesenteric lymph node
revealed neoplastic tissue in both samples. In the pancreas,
a few lobules of tumor cells surrounded by dense fibrous tissue
were found. Tumor tissue, located in the mesenteric lymph node,
almost completely replaced the lymphoid tissue. Immunocytochemistry
showed that some tumor cells stained positively for insulin,
and a diagnosis of insulin-secreting carcinoma was made (sections
from these biopsies are included, marked 40014/94, nyd 6 and
nyd 1). The dog recovered quickly. Fourteen months later, in
1995, the dog suddenly died and an autopsy was performed.
- Gross Pathology: The dog was in good body condition.
It was dehydrated and had moderate diarrhea. Lungs were heavy,
wet and dark red. The left lobe of the pancreas appeared normal.
Two mesenteric lymph nodes close to the pancreas were enlarged
and contained tumor tissue. The cut surface consisted entirely
of grayish-white, lobular tumor tissue. Focal ½ to 1 cm
diameter nodules with lobulated cut surface were found in the
- Laboratory Results: Immunocytochemistry using an avidin-biotin
complex method with an anti-insulin antibody as primary antibody
revealed positive staining of a large proportion of tumor cells
(see section marked krøsln 1 Insulin ABC).
Contributor's Diagnosis and Comments: Metastatic, insulin-secreting
carcinoma, localized to mesenteric lymph nodes (and liver). Other
diagnoses were aspiration pneumonia (sections not included) and
The biopsies examined in 1994 revealed tumor tissue arranged
in irregular cords or in closely packed nests. The neoplastic
cells were of two main types: ovoid to polyhedral cells with
eosinophilic and finely granular cytoplasm, and cuboidal or columnar
cells with a lightly basophilic cytoplasm and frequent small
cytoplasmic vacuoles. Immunoreactivity for insulin was found
in the polyhedral cells, which resembled normal pancreatic islet
cells. Further examination of the insulin negative cell population
was not performed. These cells may represent less differentiated
B-cells or presence of another cell population. A heterogeneous
cell population may be present in canine islet cell tumors, and
tumor cells that are immunoreactive for other hormones such as
glucagon, somatostatin, pancreatic polypeptide and gastrin have
been reported in insulin-secreting tumors.
The submitted sections (material from 1995) of metastatic processes
showed tumor tissue composed of a more homogenous population
of oval to polyhedral cells, of which many showed immunoreactivity
- AFIP Diagnosis: Lymph node: Neuroendocrine carcinoma,
metastatic, Rottweiler, canine
- Conference Note: In adult animals, profound hypoglycemia
is most commonly associated with hyperinsulinemia resulting from
insulin secreting tumors of the pancreas. An insulin to glucose
ration of >30 (insulin mUnits/dl ¸ serum glucose mg/dl)
in the presence of <60mg/dl of glucose is indicative of hyperinsulinemia.
Other causes of hypoglycemia include:starvation, malabsorption,
exertion, systemic disease, liver disease and hypoadrenocorticism.
The body utilizes glucose from three sources: ingestion, gluconeogenesis,
and glycogenolysis. Glucose in the blood is either used by cells
or converted into glycogen.
- The histologic pattern of irregularly arranged cords forming
a gyriform pattern is consistent with a neuroendocrine tumor.
The differential diagnosis considered by conference participants
included pancreatic islet cell tumor and other neuroendocrine
carcinomas. Immunohistochemistry performed at the AFIP revealed
multifocal positivity of the neoplastic cells for insulin, supporting
an islet cell tumor. Ultrastructurally, characteristic angular
to rhomboid "brick granules" are anticipated in pancreatic
islet cell neoplasms.
- Contributor: Norwegian School of Veterinary Science,
PO Box 8146 Dep., N-0033 Oslo, Norway
- 1. Duncan JR, Prasse KW, Mahaffey EA: Veterinary Laboratory
Medicine, Clinical Pathology, 3rd ed., pp. 122-129, 196-197.
Iowa State University Press, Ames, Iowa, 1994
- 2. Fingeroth JM, Smeak DD: Intravenous methylene blue infusion
for intraoperative identification of pancreatic islet-cell tumors
in dogs. Part II: Clinical trials and results in four dogs. J
of the Amer Anim Hosp Assoc 24:175-182, 1988
- 3. Hawkins KL, Summers BA, Kuhajda FP, Smith CA: Immunocytochemistry
of normal pancreatic islets and spontaneous islet cell tumors
in dogs. Vet Pathol 24:170-179, 1987
- 4. O'Brien TD, Hayden DW, O'Leary TP, Caywood DD, Johnson
KH. Canine pancreatic endocrine tumors: Immunohistochemical analysis
of hormone content and amyloid. Vet Pathol 24:308-314, 1987
- 5. Thoresen SI, Aleksandersen M, Lønaas L, Bredal
WP, Grøndalen J, Berthelsen K: Pancreatic insulin-secreting
carcinoma in a dog: Fructosamine for determining persistent hypoglycemia.
J Small Animal Pract 36:282-286, 1995.
- J Scot Estep, DVM
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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