AFIP Wednesday Slide Conference - No. 21

26 March 1997
Conference Moderator: LTC Catherine L. Wilhelmsen
Diplomate, ACVP
U.S. Army Medical Research Institute of Infectious Disease
Bldg. 1425
Fort Detrick, MD 21702-5011
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Case I - 950952 (AFIP 2554551)

Signalment: Adult male cynomolgus monkey (Macaca fascicularis).
History: This monkey was a placebo control in a double-blinded efficacy protocol to evaluate a new Q-fever vaccine. The monkey was aerosol exposed to Coxiella burnetii live organisms and died unexpectedly 10 days post aerosol challenge.
Gross Pathology: Marked diffuse pulmonary consolidation, mild splenic enlargement and diffuse reddening of femoral bone marrow.
Laboratory Results: Sequential chest radiographs on days zero and five post aerosol exposure were essentially normal, but radiographic examination performed on the day of death demonstrated severe generalized increase in alveolar opacity, with air bronchograms, consistent with severe generalized pneumonia.
Contributor's Diagnosis and Comments: Lungs, left and right apical and diaphragmatic lobes: Pleuropneumonia, interstitial, fibrinopurulent and histiocytic, subacute, diffuse, marked, with obliterating fibrinous alveolitis and with bronchiolar and type II pneumocyte hyperplasia.
The immediate cause of death was likely a combination of hypoxia and cardiovascular collapse due to fatal Q-fever pneumonia, possibly with myocarditis as a contributing factor. Immunohistochemical staining of the lung microsections demonstrated intracellular Coxiella burnetii antigen within macrophages and within a few granulocytes. Some extracellular C. burnetii antigen was also observed. Other lesions observed, perhaps induced by C. burnetii infection, were mild, multifocal subacute, lymphohistiocytic epicarditis and myocarditis, paracortical lymphocytic hyperplasia of mediastinal lymph nodes, myodegeneration of skeletal muscle and hyperplasia of hematopoietic precursor cells in the bone marrow. Incidental lesions in this wild caught monkey were mineralized schistosome eggs in the liver and intestine, colonic nematode granulomas consistent with oesophagostamiasis, mesenteric vasculitis, and lymphoplasmacytic gastritis. The spleen was within normal limits histologically.
Human Q fever is a zoonotic disease transmitted to man from infected animals, usually sheep, cattle and cats. Infection among animals can be tickborne, but spread to humans is usually airborne, via inhalation of infectious aerosols. Pulmonary Q fever is rarely fatal in humans. Fatal human cases are characterized by an interstitial pneumonia resembling viral pneumonia or ornithosis. A nonhuman primate Q fever model was established in cynomolgus monkeys at Fort Detrick in the late 1970's to test experimental Q fever vaccines.
AFIP Diagnosis: Lung: Bronchopneumonia, fibrinosuppurative and histiocytic, subacute, diffuse, severe, with type II pneumocyte hyperplasia, and fibrinosuppurative pleuritis, cynomolgus monkey (Macaca fascicularis), primate.
Conference Note: Additional findings in some sections include bronchus- associated eosinophilic infiltrates and pigment likely secondary to Pneumonyssus sp. lung mites.

Q fever is a zoonosis. Worldwide, the most common animal reservoirs for Coxiella burnetti are cattle, sheep, and goats. When infected, these ungulates shed the desiccation-resistant organism in urine, feces, milk, and especially birth products. Domestic animals are probably infected by ticks in most cases. C. burnetti naturally infects over 40 species of ticks found on five continents. There is a wildlife cycle of infection, including birds, wild rabbits, desert rats, mice, and bandicoots. Humans are generally infected incidentally by inhalation of aerosols containing the organisms.
Coxiella burnetti is a member of the Rickettsiaceae family. It is a highly pleomorphic coccobacillus measuring 0.3 X 1.0 µm and having a cell wall similar in composition to those found in gram-negative bacteria. C. burnetti survives within the phagolysosome of the host. C. burnetti contains plasmids that appear to differ among isolates associated with different clinical syndromes. The discovery of a spore stage explains the extraordinary ability of C. burnetti to withstand harsh environmental conditions. The ability to destroy the spore stage is the current standard by which adequate milk pasteurization is measured.
Contributor: Pathology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011.
1. Baca OG, Paretsky D: Q fever and Coxiella burnetii: a model for host-parasite interactions. Microbiol Rev 47:127-149, 1983.
2. Gonder JC, Kishimoto A, Kastello MD, Pedersen CE, Larson EW: Cynomolgus monkey model for experimental Q fever infections. J Inf Dis 139:191-196, 1979.
3. Marrie TJ: Q-fever pneumonia: Med Grand Rounds 3:354-365, 1985.
4. Marrie TJ, Stein A, Janigan D, Raoult D: Route of infection determines the clinical manifestations of acute Q fever. J Inf Dis 173:484-487, 1996.
5. Reimer LG: Q fever. Clin. Microbiol Rev 6:193-198, 1993.
6. Urso FP: The pathologic findings in rickettsial pneumonia. Am J. Clin Pathol 64:335-342, 1975.
International Veterinary Pathology Slide Bank: None.

Case II - 15374-96 (AFIP 2548135)

Signalment: One approximately 8-week-old, 16 kilogram, crossbreed pig was submitted for postmortem examination. Lung and heart were submitted from another pig by the practitioner.
History: Sudden death, or recumbency with paddling.
Gross Pathology: The carcass appeared gaunt and slightly dehydrated. Multiple small pustules ranging in size from 1 to 8 millimeters were present on the skin. Multiple gray foci were present on serosal and cut surfaces of the liver. Moderate splenomegaly was noted. Lungs were congested and multiple petechia were diffusely distributed over visceral pleural surfaces. The left carpal joint contained cloudy yellow fluid.
Laboratory Results: Actinobacillus suis was isolated from lung, liver, kidney, spleen, skin pustules, and joint swabs of the left carpus.
Contributor's Diagnosis and Comments: Liver, hepatitis, necrotizing, random, with intralesional bacterial emboli - Actinobacillus suis.
Multiple random areas of coagulative necrosis are distributed throughout congested hepatic parenchyma. Colonies of small bacilli can be seen in centers of necrotic foci. Lesions in other organs are: moderate diffuse neutrophilic alveolitis; septic emboli in heart, kidney, spleen and intestines; and focal necrosuppurative to ulcerative dermatitis. Naturally occurring actinobacillosis of swine is characterized by multiple septic emboli in many tissues, as exhibited in this case.
AFIP Diagnosis: Liver: Hepatitis, peracute to acute, necrotizing, random, multifocal, moderate, with bacillary emboli, mixed-breed, porcine.
Conference Note: Actinobacillus suis can infect pigs of all ages, but infection is most serious in very young animals. In neonates and suckling pigs, A. suis causes an acute and rapidly fatal septicemia; death can occur within 15 hours. Cyanosis, petechial hemorrhage, fever, respiratory distress, neurologic disturbances, and arthritis may be present. Similar signs have been reported in piglets infected with A. equuli or A. equuli-like organisms. In mature animals, A. suis infection can be confused with erysipelas. These animals may have erythematous skin lesions, fever, and inappetence. Abortion, metritis, and meningitis have also been reported in sows.
A. suis infection occurs via the aerosol route or by gaining entry through breaks in the skin. The organism spreads rapidly throughout the body once it has entered the circulatory system. Relatively little is known about the virulence factors of A. suis with the exception of the ash operon, which encodes an RTX toxin. The RTX toxins described for Actinobacillus pleuropneumonia are cytolysins with the ability to lyse erythrocytes, and kill lymphocytes, epithelial cells, and macrophages. These toxins act by forming pores in the cell membranes. At sublytic concentrations, the RTX toxins affect oxidative metabolism of phagocytic cells.

Contributor: University of Nebraska, Lincoln Veterinary Diagnostic Center, Lincoln, NE 68583-0907.

1.Christianson C: Clinical significance of Actinobacillus suis. American Assoc. of Swine Practitioners, Proceedings, 1990.
2. Cutlip RC, et al: Septic embolic Actinobacillosis of swine: A case report and laboratory reproduction of the disease. Am J Vet Res 33(8):1621-1626, 1972.
3. Jang SS, et al: Actinobacillus suis-like organisms in horses. Am J Vet Res 48(7):1036-1038, 1987.
4. Jones JET, et al: Endocarditis in the pig caused by Actinobacillus equuli: A field and experimental case. Br Vet J 127:25-29, 1971.
5. Liver E, Larsen HJ: Infection with Actinobacillus suis in pigs. Acta Vet Scand 19:313-315, 1978.
6. MacDonald DW, et al: Actinobacillus suis infections in Alberta swine, 1973- 1975: Pathology and Microbiology. Can Vet J 17(10):251-254, 1976.
7. Randall CJ, et al: Actinobacillus suis infections in pigs. J Comp Path 84:113- 119, 1974.
8. Miniats OP, Spinato MT: Actinobacillus suis septicemia in an SPF swine herd - a case report. IPVS, pg. 158, 1988.
9. Pedersen KB: Actinobacillus infektioner hos svin. Nord Vet-Med 29:137-140, 1977.
10. Sanford SE, et al: Actinobacillus suis outbreaks in pigs in Ontario: Pathology and bacteriology of a creeping epidemic. IPVS, pg. 183, 1990.
11. Windsor RS: Actinobacillus equuli infection in a litter of pigs and a review of previous reports on similar infections. Vet Rec 92:178-180, 1973.
12. Gyles CL, Thoen CO (eds): Pathogenesis of Bacterial Infections in Animals. second edition, Iowa State University Press, pp. 191-194, 1993.
International Veterinary Pathology Slide Bank: None.

Case III - N96-177 (AFIP 2544359)

Signalment: 8-year-old Belgian Malinois dog.
History: This dog presented in June 1995 with clinical signs of orchitis. Castration was performed. On histopathologic examination, granulomas that contain fungal organisms consistent with Coccidioides immitis were found. Serology was also positive for coccidioidomycosis. The dog was treated with ketoconazole for 6 months. At the end of the treatment period, a positive titer for coccidioidomycosis was still present. The dog developed osteolytic and productive lesions of the second and third lumbar vertebrae. Biopsies confirmed osteomyelitis caused by Coccidioides immitis. Euthanasia was performed.
Gross Pathology: None.
Laboratory Results: None.
Contributor's Diagnosis and Comments:
1. Vertebra, (L4), periosteum, endosteum and marrow: Osteomyelitis, chronic, granulomatous, multifocal to coalescing, severe with fungal spherules/sporangia, proliferative, periostitis and endosteitis, Belgian Malinois, canine.
2. Lumbar skeletal muscle, myocytes and interstitium: Myositis, granulomatous, multifocal to coalescing, moderate, with fungal spherules/sporangia and focally extensive, myofiber regeneration.
3. Spinal cord, lumbar segment (L4), dura: Perineuritis, chronic multifocal to coalescing, mild.
4. Spinal cord, lumbar segment (L4), dura: Metaplasia, osseous, focal, mild.
Coccidioides immitis is a geophilic, dimorphic fungus. The free-living mycelial phase in the soil produces arthroconidia which are the source of infection for mammals. Animals are infected following inhalation of arthroconidia, although direct inoculation through the skin has caused infection. Once inside the mammalian host, the arthroconidia are transformed to the parasitic spherular phase. The large spherules (20 to 100 m in diameter) grow, mature and divide internally to produce endospores. When released, the endospores spread the infection locally or to distant sites via lymphatics or blood. Disseminated canine coccidioidomycosis carries a guarded prognosis. Most dogs respond well initially but relapse when treatment is discontinued, as in this case.
There is no known risk of direct transmission of C. immitis from companion animals to humans. Caution should be used in handling animals with draining cutaneous wounds and dressings from these animals.
AFIP Diagnosis:
1. Vertebra, fourth lumbar (per contributor): Osteomyelitis, granulomatous, diffuse, severe, with multiple granulomas, osteonecrosis, new bone formation, and fungal spherules, Belgian Malinois, canine, etiology consistent with Coccidioides immitis.
2. Skeletal muscle: Myositis, granulomatous, focally extensive, moderate, with granulomas, myofiber atrophy, fibrosis, and regeneration.
3. Bone marrow: Hyperplasia, myeloid, diffuse, moderate.
Conference Note: Coccidioides immitis is a soil organism restricted to the lower Sonoran life zone, which is characterized by sandy, alkaline soil, high environmental temperature, low rainfall, and low elevation. Geographically, this area includes parts of the southwestern United States, Mexico, Central America and South America. Coccidioidomycosis has been described in man, all species of domestic animals and in a variety of wild animals.
In the soil, C. immitis occurs as a saprophytic mycelial phase which gives rise to readily aerosolized arthroconidia. In host tissue arthroconidia transform into spherules that gradually enlarge up to 20-100 µm in diameter. Rarely, spherules may reach up to 200 µm in diameter. The nuclei within the spherule divide to form numerous uninucleate endospores, 2-3 µm in diameter (endosporulation). When released from the spherule, each endospore will form a new mature spherule at 37°C, or a mycelium at room temperature. In the body, the endospore may mature at the site of release or spread to other tissue via lymphatics or the blood. Endospores are not considered infectious to other animals (arthroconidia from the mycelial phase are highly infectious), although a recent case of coccidioidomycosis was diagnosed in a veterinarian exposed to disseminated coccidioidomycosis while examining a horse at necropsy.
The major route of infection is by inhalation of arthroconidia. Following inhalation, the spores enter the bronchioles and alveoli, then extend into the peribronchiolar tissue, moving toward the lung surface and causing subpleural lesions. There is an initial influx of neutrophils, followed by monocytes, lymphocytes, and plasma cells. With massive exposure or depressed cellular immunity, pulmonary infection may become extensive, and the organisms can spread to the mediastinal and tracheobronchial lymph nodes, eventually becoming widely disseminated. Boxers and Doberman Pinchers reportedly have a greater incidence of disseminated disease than other dogs. In disseminated coccidioidomycosis, the organs usually affected, in decreasing order of frequency, are bones and joints, visceral organs (primarily the spleen, liver, and kidneys), heart and pericardium, testicles, eye and retina, and central nervous system. The skin alone is rarely involved; draining fistulas are usually associated with underlying osteomyelitis. Primary localized skin lesions associated with penetrating wounds are reported but are rare.
Contributor: Department of Defense Military Working Dog Center, Lackland Air Force Base, TX.
1. Ziemer EL, Pappagianis D, Madigan JE, Mansmann RA, Koffman KD: Coccidioidomycosis in horses: 15 cases (1975-1984). J Am Vet Assoc. 201(6), pp. 910- 16, 1992.
2. Fowler ME, Pappagianis D, Ingram I: Coccidioidomycosis in llamas in the United States: 19 cases (1981-1989). J Am Vet Assoc. 201(10):1609-1614, 1992.
3. Greene RT, Troy GC: Coccidioidomycosis in 48 cats: a retrospective study (1984-1993). J Vet Int Med 9(2):86-91, 1995.
4. Stoltz JH, Johnson BJ, Walker RL, Pappigianis D: Coccidioides immitisabortion in an Arabian mare. Vet Pathol 31(2):258-59, 1994.
5. Khohn GJ, Linne SR, Smith CM, Hoeprich PD: Acquisition of coccidioidomycosis at necropsy by inhalation of coccidioidal endospores. Diagn Microbiol Infec Dis 15(6):527-30, 1994.
6. Jubb KVF, Kennedy PC and Palmer N (eds): Pathology of Domestic Animals; Academic Press, 4th ed., Vol. 2, pp. 518, 668-670, 1993.
7. Ettinger SJ and Feldman EC (eds): Textbook of Veterinary Internal Medicine,4th Edition, Vol, 1, pp. 444-448, 1995.

International Veterinary Pathology Slide Bank:
Laser disc frame #21879, 21884, 21885, 21886.

Case IV - 95:1407 (AFIP 2558104

Signalment: Mature, male, grey squirrel (Sciurus carolinensis)

History: No history was provided.
Gross Pathology: The skin of the right axilla had three raised, sparsely haired, reddened, firm nodules which were approximately 5mm in diameter.
Laboratory Results: None available.
Contributor's Diagnosis and Comments: Haired skin: Dermatitis, subacute, multifocal, nodular, moderate with fibroplasia, acanthosis, ballooning degeneration, mild orthokeratotic hyperkeratosis, and eosinophilic intracytoplasmic inclusion bodies, grey squirrel (Sciurus carolinensis).
Etiology: Leporipoxvirus (squirrel pox virus).
Squirrel pox virus in a member of the Leporipoxvirus genus of the family Poxviridae. The myxoma and Shope fibroma viruses of rabbits also belong to the genus Leporipoxvirus.
The virus has been successfully transmitted into grey squirrels by experimental inoculation and experimental transmission by mosquitoes. Infection of adult squirrels results in cutaneous lesions, whereas juveniles develop multi- organ proliferative or neoplastic epithelial and fibropapillomatous poxvirus lesions.
The cutaneous papules of squirrel poxvirus infection may be numerous and involve all areas of the skin. Histologically, the skin papules are composed of two components, a dermal and an epidermal component. The dermal component is characterized by fibroplasia with a moderate infiltrate of lymphocytes, plasma cells, histiocytes, and a few neutrophils. The overlying epidermis is acanthotic, has ballooning degeneration of the stratum spinosum and contain eosinophilic, intracytoplasmic inclusion bodies. Orthokeratotic hyperkeratosis may or may not be present. Ulceration of the epidermis can occur with crust formation and secondary bacterial or fungal infection.
AFIP Diagnosis:
1. Haired skin: Atypical mesenchymal proliferation, nodular, with epidermal hyperplasia, ballooning degeneration, spongiosis, and eosinophilic intracytoplasmic inclusion bodies, grey squirrel (Sciurus carolinensis), rodent.
2. Haired skin, subcutaneous adipose tissue: Steatitis, granulomatous, multifocal, moderate.
3. Haired skin, deep skeletal muscle: Myositis, chronic, multifocal, mild, with myofiber atrophy and regeneration.
Conference Note: Participants agreed with the contributor's diagnosis. The relationship of the steatitis and myositis to the poxviral lesion is uncertain.
In the grey squirrel, multiple fibromas have been reported to occur in the skin, heart, lung, kidney, liver, mesentery, testes, and lymph nodes. The pathogenesis of the disseminated squirrel fibroma is not completely understood, but it is believed that the virus spreads hematogenously.
Poxviruses are known to cause tumors or tumor-like lesions in man and a variety of other animals. Examples include Yaba disease in African monkeys, molluscum contagiosum in humans, horses, macropods and chimpanzees, lumpy skin disease in cattle, genital papillomatosis in swine, sheep pox, contagious ovine ecthyma, myxomatosis in European rabbits (Oryctalagus spp.), and fibromas in cottontail rabbits (Sylvilagus spp.)
Contributor: University of Connecticut, Department of Pathobiology, 61 North Eagleville Road, U-89, Storrs, CT 06269-3089.
1. O'Connor DJ, Diters RW, Nielsen SW. Poxvirus and multiple tumors in an eastern grey squirrel. JAVMA 177:792-795, 1980.
2. Hirth RS, Wyand DDS, Osborne AD, Burke, CN. Epidermal changes caused by squirrel poxvirus. JAVMA 155:1120-1125, 1969.

International Veterinary Pathology Slide Bank:
Laser disc frame #21035, 21036, 21037.
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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