AFIP Wednesday Slide Conference - No. 20

March 12 1997

Conference Moderator: LTC William H. Baker
Diplomate, ACVP
Walter Reed Army Institute of Research
Division of Pathology
Washington, D.C. 20307-5100
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Case I - A95-401 (AFIP 2549261)

Signalment: 1-year-old, male, rhesus monkey (Macaca mulatta).
History: This monkey was inoculated intravenously with a pathogenic, cloned variant of SIVmac239 four months prior to sacrifice. There was a recent history of dehydration, anorexia, cutaneous erythema, and weight loss.
Gross Pathology: There was weight loss (1.7 Kg, normal=2.0-2.4 Kg) and abdominal adipose tissue was sparse. The right middle lung lobe was atelectatic, pale pink to purple, and somewhat firm on palpation. The mesenteric and ileocecal lymph nodes were enlarged (approximately 2-3 times normal), white, and soft on palpation.
Laboratory Results: Microbiology: A few coagulase-negative staphylococci, small numbers of alpha streptococci, and few Pseudomonas mirabilis were cultured from lung. No significant organisms were cultured from the colon or heart blood.
Contributor's Diagnosis and Comments:
1. Trachea: tracheitis, lymphoplasmacytic, chronic-active, diffuse, moderate with squamous metaplasia and apical protozoa.
2. Lung: bronchiolitis, lymphoplasmacytic, chronic-active, diffuse, with squamous metaplasia and apical protozoa.
3. Lung: pneumonia, bronchointerstitial, subacute, multifocal, moderate.
Trachea: Cryptosporidium sp.
Lung: Cryptosporidium sp. and cytomegalovirus (CMV).
In the section of trachea there are multiple 2 micron diameter basophilic spherical protozoa adhered to the mucosal surface. There is attenuation of the epithelium, loss of goblet cells and cilia. Glands in the lamina propria have squamous metaplasia with protozoa of similar morphology adhered to the epithelium of some cells, and inflammatory cellular debris in lumina. In the lamina propria there are diffuse to aggregated lymphoplasmacytic cellular infiltrates, admixed with few eosinophils, between and around the glands. Capillaries are congested.
Affecting approximately 40% of lung parenchyma are multifocal areas of inflammation which are primarily associated with the pulmonary vessels, smaller airways, and the interstitium. In bronchi, the epithelial cells have numerous 2 micron diameter basophilic spherical protozoa adhered to the apical surface with few intra- epithelial leukocytes present. This is accompanied by loss of goblet cells and cilia. The submucosal glands have squamous metaplasia with protozoa adhered to the epithelium. The proprial stroma has diffuse infiltrates of lymphocytes and plasma cells which extend between and around the submucosal glands. Alveoli immediately surrounding bronchi are collapsed. Multifocally and circumferentially arranged around bronchioles and blood vessels are varying admixtures of lymphocytes, plasma cells, macrophages, eosinophils and neutrophils; there is mild perivascular edema. The lumina of some bronchioles and alveoli have accumulations of neutrophils, macrophages, and debris partially occluding lumina; this is accompanied by type II pneumocyte hyperplasia and rare cytomegalic cells with intranuclear inclusions. The inflamed interstitium is expanded due to infiltrates of mixed mononuclear cells and granulocytes.

The genus Cryptosporidium (phylum, Apicomplexa; family, Cryptosporiidae) includes ubiquitous protozoan parasites that infect fish, reptiles, birds, and mammals, and that grow and reproduce within epithelial cells (i.e., intracellular, extra cytoplasmic). Cryptosporidiosis is not a common finding in SIV-infected macaques, but when present is usually found in the small intestine resulting in a chronic diarrhea syndrome producing malnutrition. The pathogen is sometimes found in the gall bladder, biliary ducts, and pancreatic ducts resulting in proliferative lesions in each. Respiratory cryptosporidiosis is apparently rare in macaques, particularly when it is the only system infected. Immunohistochemistry (IHC) performed on sections of lung identified the organism attached chiefly to the tracheal and bronchial epithelium, but a few organisms were identified both within macrophages and free in the lumina of bronchioles and alveoli. Multiple sections of intestine, pancreas, gall bladder, and liver were negative.
When respiratory disease is found in macaques with AIDS, it is common to find more than one etiologic agent. Other respiratory pathogens found in these animals include SIV (giant cell pneumonia), Pneumocystis carinii, CMV, Mycobacterium avium, and to a lesser extent Toxoplasma gondii and various bacteria and fungi. The tracheitis and bronchitis in this animal were compatible with cryptosporidiosis, and C. parvum is the most likely etiology. However, significant numbers of organisms were not detected by IHC in the bronchioles or alveoli suggesting a possible separate etiology for pneumonia. In some sections, CMV inclusions may be observed, and moderate numbers of CMV positive cells were detected by in situ hybridization; low numbers of SIV positive cells were detected. The bacteria recovered from the lung were considered to be contaminants.
Perivascular inflammatory lymphohistiocytic infiltrates and pulmonary lymphoid hyperplasia can be manifestations of SIV-induced pulmonary lesions. Pulmonary CMV may present as an interstitial pneumonia. The pneumonic lesions in this animal may represent mild CMV infection, CMV/SIV co-infection, or a manifestation of all three etiologies.
The means by which primary respiratory cryptosporidiosis developed is not known. The organism may have become dislodged from the upper airway. Other significant microscopic findings in this animal included cytomegaloviral orchitis, cytomegaloviral meningitis, mild enteritis, and a non-specific degenerative myelopathy.
AFIP Diagnosis: 1. Trachea; bronchi: Tracheobronchitis, lymphoplasmacytic and eosinophilic, diffuse, moderate, with luminal epithelial hyperplasia, loss of cilia and goblet cells, multifocal squamous metaplasia, tracheobronchial adenitis, and numerous protozoa, rhesus monkey (Macaca mulatta), primate - etiology consistent with Cryptosporidium sp.
2. Lung: Pneumonia, bronchointerstitial, subacute, diffuse, moderate, with type II pneumocyte hyperplasia and rare cytomegalic/karyomegalic cells with eosinophilic intranuclear inclusion bodies.
Conference Note: The conference participants agreed with the contributor's diagnoses. Rare intranuclear inclusion-bearing cytomegalic cells were found within epithelial cells and vascular smooth muscle cells in some sections. This case illustrates the importance in looking for multiple etiologic agents in animals suspected of having immunosuppressive disease.
Contributor: New England Regional Primate Research Center, P.O. Box 9102, Southborough, MA 01772-9102.
1. Baskin GB, Murphey-Corb M, Martin LN, et al: Lentivirus-induced pulmonary lesions in rhesus monkeys (Macaca mulatta) infected with simian immunodeficiency virus. Vet Pathol 28:506-513, 1991.
2. Blanchard JL, Baskin GB, Murphey-Corb M, et al: Disseminated Cryptosporidiosis in simian immunodeficiency virus/delta-infected rhesus monkeys. Vet Pathol 24:454-456, 1987.
3. Current WL, Reese NC, Ernst JV, et al: Human Cryptosporidiosis in immunocompetent and immunodeficient persons. N Engl J Med. 308:1252-1257, 1983.
4. Fayer R and Ungar LP: Cryptosporidium spp. and Cryptosporidiosis. Microbiol Rev. 50:458-483, 1986.
5. Hoerr FJ, Ranck FM, Hasting TF: Respiratory cryptosporidiosis in turkeys. JAVMA 173:1591-1593, 1978.
6. Kestler H, Kodmana T, Ringler D, et al: Induction of AIDS in rhesus monkeys by molecularly cloned simian immunodeficiency virus. Science. 248:1109-1112, 1990.
7. Kovatch RM and White JD: Cryptosporidiosis in two juvenile rhesus monkeys. Vet Pathol. 9:426-440, 1972.
8. Naidu, YM, Kestler HW, Li Y, et al: Characterization of infectious molecular clones of simian immunodeficiency virus (SIVmac) and human immunodeficiency virus type 2: Persistent infection of rhesus monkeys with molecularly cloned SIVmac. J Virol. 62:4691-4696, 1988.
9. Simon MA, Chalifoux LV and Ringler DJ: Pathologic features of SIV-induced disease and the association of macrophage infection with disease evolution. AIDS Res Hum Retroviruses 8:327-337, 1992.
10. Sun, T: Current topics in protozoal disease (Review): Am J Clin Pathol. 102:16-29, 1994.
International Veterinary Pathology Slide Bank:
Laser disc frame #Cryptosporidium: 21239, 23314, 23316, 12573. Cytomegalovirus: 13124.

Case II - NADC 96-1 (AFIP 2548580)

Signalment: 6-week-old female pig.
History: This pig was part of a group of pigs that were inoculated intra-nasally with Bordetella bronchiseptica, strain 4609. This pig developed pneumonia 5 days post- inoculation (PI) and was necropsied.
Gross Pathology: Marked acute multifocal suppurative bronchopneumonia.
Laboratory Results: B. bronchiseptica was isolated from lung tissue. Numerous bacteria and bacterial antigen by immunocytochemistry were present in the cilia of epithelial cells lining the nasal conchae, trachea, and bronchi. Bacteria and antigen were also present in small portions of cilia within the alveoli of some pigs. These detached portions of cilia presumably came from bronchi or trachea and entered alveoli during inspiration. Bacterial antigen was also present in the cytoplasm of macrophages and neutrophils within alveolar lumens.
Sections of lung contain marked multifocal infiltrates of neutrophils, cell debris, seroproteinaceous fluid and red blood cells. Such exudates were present within dilated bronchi, bronchioles, and the adjacent alveolar lumens. The epithelium lining of some bronchi and bronchioles is multifocally denuded.
Contributor's Diagnosis and Comments: Marked acute to subacute bronchopneumonia with hemorrhages and rod-shaped bacteria associated with cilia. Etiology: Bordetella bronchiseptica
B. bronchiseptica colonizes ciliated cells of the respiratory tract. This results in a suppurative rhinitis and possibly pneumonia that eventually changes into a lymphoplasmacytic rhinitis and chronic pneumonia. In chronic lung lesions, there can be prominent peribronchial and peribronchiolar fibrosis. B. bronchiseptica is associated with conchal atrophy (atrophic rhinitis) and can induce moderate to severe conchal atrophy experimentally. Several studies have shown that if pigs are cleared of the B. bronchiseptica infection, the conchae can return to near normal size. Therefore, conchal atrophy caused by B. bronchiseptica has been termed reversible or nonprogressive. Toxigenic strains of Pasteurella multocida can also induce conchal atrophy; however, the conchae do not typically regrow after clearance of these organisms. Therefore, P. multocida induced conchal atrophy is termed irreversible or progressive. Combined infections of B. bronchiseptica and P. multocida produce severe forms of conchal atrophy that are irreversible. Both toxigenic and non-toxigenic strains of P. multocida can cause pneumonia and pleuritis.
B. bronchiseptica produces a variety of virulence factors and toxins. These include attachment factors such as fimbriae, filamentous hemagglutinin, and pertactin. Toxins include: dermonecrotic toxin, adenylate cyclase, and tracheal cytotoxin. B. bronchiseptica does not produce pertussis toxin. Of the above toxins, very little is known about their influence on respiratory disease and conchal atrophy. Many assume that the dermonecrotic toxin induces conchal atrophy; however, this has not been clearly demonstrated. Thus, little can be said about the virulence of B. bronchiseptica isolates from pigs until more is known about the virulence factors and toxins. P. multocidacolonizes tonsil to a greater degree than turbinate, trachea, and lung. The toxin of P. multocida can be produced by either A or D strains. Experimentally, the toxin increases the number of osteoclasts in long bones of rats, induces osteoclast formation in vitro, decreases the proliferation rate of chondrocytes in the growth plate of long bones, and causes hepatic and testicular necrosis.
AFIP Diagnosis: Lung: Pneumonia, necrohemorrhagic, fibrinous, diffuse, severe, with vasculitis, fibrin thrombi and cilia-associated bacilli, breed unspecified, porcine.
Conference Note: The conference participants agreed with the contributor's diagnosis and well written comments. Atrophic rhinitis continues to be an important cause of economic loss to the swine industry.
Contributor: USDA/ARS/National Animal Disease Center, P.O. Box 70, 2300 Dayton Road, Ames, IA, 50010-0070.
1. Ackermann MR, Rimler RB and Thurston JR: Experimental model of atrophic rhinitis in gnotobiotic pigs. Infection and Immunity, 59:3626-3629, 1991.
2. Goged NT: Pasteurella multocida toxin: The characterization of the toxin and its significance in the diagnosis and prevention. AMPIS (Acta Pathology, Microbiology, and Immunology Scandinavian). February: 1-55, 1992.
3. Gagné S and Martineau-Diozé B: Nasal epithelial changes induced in piglets by acetic acid and by Bordetella bronchiseptica. J Comp Pathol 109:71-81, 1993.
4. Magyar T, Chanter N, Lax AJ, Rutter JM, Hall GA: The pathogenesis of turbinate atrophy in pigs caused by Bordetella bronchiseptica. Vet Microbiol 48:693- 701, 1988.
5. Register KB, Ackermann MR, and Dyer D: Nonradioactive colony lift- hybridization assay for detection of Bordetella bronchiseptica infection in swine. J Clin Microbiol 33:2675-2678, 1995.
International Veterinary Pathology Slide Bank:
Laser disc frame #7514, 12716, 13993, 12939, 2242.

Case III - Dog-2 Sanofi (AFIP 2557308)

Signalment: 11-month-old male Beagle.
History: Dog was found dead on study day 32. No significant abnormalities were observed up to study day 31. On study day 32, ptyalism, dyspnea and weakness were observed prior to death.
Gross Pathology: Oral mucosa was pale. Subcutaneous tissue in the neck was disrupted by a hematoma and fascia was edematous and pale green. In the thoracic cavity, hemothorax was accompanied by pale green areas in parietal pleura and adhesions between the lung and parietal pleura.
Laboratory Results: None.
Contributor's Diagnosis and Comments: Pleuritis, granulomatous, chronic, marked.
Etiologic agent unknown; no bacteria observed with Gram stain and no fungal elements with PAS stains.
Additional significant lesions observed included the following: granulomatous pleuritis of the diaphragm with Gram+ cocci; subacute periarterial inflammation of the carotid artery with Gram+ cocci; and marked granulomatous serositis of the esophagus with Gram+ cocci.
This lesion is considered traumatic in origin, probably caused by esophageal injury before initiation of the study, as the dogs were not gavaged. Initial inflammation in the cervical region then extended into the thorax. The cause of the hematoma and hemothorax were not identified.
AFIP Diagnosis: Lung: Pleuritis, chronic-active, proliferative, diffuse, severe, with diffuse atelectasis and fibrino-cellular thrombi, Beagle, canine.
Conference Note: Conference participants discussed the difference between chronic active pleuritis and mesothelioma. The regular, even distribution of this lesion and the presence of inflammation argue against a diagnosis of mesothelioma. Reactive mesothelium is often pleomorphic and must be differentiated from neoplastic mesothelium.
Pleuritis can be caused by numous different bacteria and is often secondary to pneumonia. Other pathways by which infectious agents may reach the pleura include hematogenous or lymphatic spread, direct extension from the esophagus or abdominal viscus, and traumatic penetration through the thoracic wall.
In the dog, the most common causes of pleuritis are Actinomyces, Nocardia, and Bacteroides spp. Mixed bacterial infections are common and a variety of organisms may be present, including Corynebacterium spp., Pasteurella spp., E. coli, Fusobacterium necrophorum, Pseudomonas spp., and streptococci.
Contributor: Sanofi Research Division, 9 Great Valley Parkway, Collegeville, PA, 19426.
Jubb KVF, Kennedy PC, Palmer N (eds): Pathology of Domestic Animals, 4th ed., Vol. 2, Academic Press, pp. 697-698; 443-444, 1993.
International Veterinary Pathology Slide Bank:
Laser disc frame #Pleuritis: 2460, 2461, 8770, 9223, 9529, 23916. Mesothelioma: 0648, 2867, 5665, 20938.

Case IV - 95-4682N (AFIP 2550440)

Signalment: 5-year-old, female, mixed breed dog.
History: Sudden onset of weakness and depression. Physical exam revealed pale mucous membranes and tachycardia. The dog had been diagnosed with Addison's disease two weeks previously and was on prednisone therapy. Soon after admission, the dog went into cardiac arrest and died.
Gross Pathology: Necropsy revealed massive hepatic necrosis and hemorrhage, generalized icterus and petechiae in lung, mouth, esophagus, stomach, intestine and urinary bladder. Hemorrhage was present in the stomach and intestine. The adrenal glands were small.
Laboratory Results: Packed cell volume on day of presentation was 14.
Contributor's Diagnosis and Comments: Hepatic necrosis, centrilobular to coalescing, severe, with intranuclear inclusion bodies, consistent with adenovirus infection.
Infectious canine hepatitis is a rare disease and typically occurs in young dogs where it causes mild to severe clinical disease. It is unusual for the disease to occur in the older dog and cause sudden death. This dog died of hemorrhage probably caused by disseminated intravascular coagulation (DIC). The dog had renewed it's annual DHL vaccine 4 months previous.
AFIP Diagnosis: Liver: Hepatitis, necrotizing, acute, multifocal to coalescing, severe, with hemorrhage and rare basophilic intranuclear inclusion bodies, mixed-breed, canine, etiology consistent with canine adenovirus type 1.
Conference Note: Infectious canine hepatitis is caused by canine adenovirus type 1 (CAV1). CAV1 is unusual among the adenoviruses, in that it is capable of causing severe generalized disease affecting including liver, lung, eye, brain, and kidney. CAV1 is distinct from canine adenovirus type 2, which usually causes a mild respiratory infection in the dog. Coyotes, wolves and raccoons are also susceptible to CAV1. CAV1 has special tropism for endothelium, mesothelium, and hepatic parenchyma. Virions are assembled in the nucleus and are released during cell lysis. Oral or conjunctival exposure is presumed to be the natural route of infection. Viral replication occurs initially in the tonsils; the resulting tonsillitis can be severe with extensive edema of the throat and larynx. Fever accompanies the tonsillitis and precedes the viremic phase, which is of short duration and accompanied by severe leukopenia. The order of infection of Kupffer cells, sinusoidal endothelium and hepatocytes is unclear, but all are affected. As stromal collapse does not occur, there is rapid hepatic regeneration with no significant residual lesions in survivors. Hemorrhage of serosa, gingiva, lungs and the brain are due to viral infection of capillary and venule endothelium. Disseminated intravascular coagulation is a frequent complication that begins in the early viremic phase. Thrombocytopenia results from severe vascular endothelial damage with adhesion of platelets in sinusoids. Although the production of clotting factors may be somewhat reduced, the effect of accelerated consumption is greater. Ocular lesions may develop between 7 and 21 days of infection. There is inflammatory edema of the iris, ciliary body, and corneal propria with viral antigen in all but the cornea; cellular infiltrates of the iris and filtration angle are principally plasma cells. This lesion represents a local type III hypersensitivity reaction to virus-antibody complex deposition in the small blood vessels of the ciliary body and iris, and the resulting interference with normal fluid exchange. During ICH recovery, the virus is eliminated from most organs, but tends to persist in the kidney, with virus being shed in urine for up to 9 months post-infection.
Contributor: Department of Biomedical Sciences & Pathobiology, College of Veterinary Medicine, VA Tech, Blacksburg, VA 24061-0442.
1. Kelly RW: The liver and Biliary System. In: Pathology of Domestic Animals, eds. Jubb KVF, Kennedy PC and Palmer N. 4th ed, vol 2, pp. 364-366, 1993.
2. Fenner, et al.: Veterinary Virology, Academic Press, pp. 330-335, 1993.
International Veterinary Pathology Slide Bank:
Laser disc frame #15725.
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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