Difference between revisions of "Sheep Pulmonary Adenomatosis"
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[[Category:Respiratory_Viral_Infections]] | [[Category:Respiratory_Viral_Infections]] | ||
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+ | [[Category:Respiratory System - Hyperplastic/Neoplastic Pathology]] |
Revision as of 17:54, 19 February 2011
This article is still under construction. |
Antigenicity
- The virus cannot be grown in culture, although it can be seen by EM on tumor cells of infected sheep
Pathogenesis
- Causes a proliferation of alveolar lining cells, producing massive amounts of fluid
- Proliferative foci project into alveoli and bronchi and from slow-growing tumors
- Death occurs between 3-4 years of age
Clinical signs:
- Low exercise tolerance
- Gradual weight loss
- Dyspnoea
- Coughing
- Nasal fluid discharges during wheelbarrow test
- Secondary bacterial infection by Pasteurella hemolytica often precipitates death
- PM reveals fawn-gray tumor (for more see here)
Epidemiology
- Found in 25% of pneumonia cases in Scotland
- Absent in USA, common in UK
Diagnosis
- Electron microscopy on lung biopsy
Control
- Cull clinically affected animals
- Also called pulmonary carcinomatosis
- Infectious bronchiolar-alveolar carcinoma caused by a retrovirus
- Commonest under intensive management systems which favour aerosol transmission and close contact of disease
- Behaves like chronic pneumonia
- Takes months to years to express itself clinically as coughing and exercise intolerance
- Gross pathology:
- Heavy lungs which fail to collapse
- The lesions progress from small firm grey/white nodular lesions to extensive confluent areas with replacement by neoplastic tissue
- Cut surface oozes fluid
- There is often coexistent infection present
- Occasional metastases to bronchial and mediastinal lymph nodes can occur
- Histopathology:
- Widespread proliferation of alveolar (Type 2) and terminal bronchiolar epithelium, lining the alveoli and lower airways
- Multiple neoplastic foci of cuboidal/columnar cells forming papillary projections into the lumen
- Metastases of the same in the bronchial and mediastinal lymph nodes
- There is no serological test, and diagnosis depends upon raising the animal by the hind limbs whereupon a clear fluid issues from the nose = "Wheelbarrow test"
More information
Overview
Etiology: Type B/D Retrovirus (also known as the jaagziekte retrovirus‑‑JSRV)
Condition: Pulmonary carcinomatosis.
Synonyms: Jaagsiekte, sheep pulmonary adenomatosis, ovine pulmonary carcinoma.
General
- Pulmonary carcinomatosis (OPC) is an infectious form of bronchioalveolar tumor with behavior of a low-grade carcinoma.
- Associated with (and strong evidence that is caused by) a type B/D retrovirus of family Retroviridae (single-stranded RNA).
- Occurs in Africa, Europe and the Americas.
- Susceptibility among breeds varies; Merino sheep are highly susceptible.
- The condition is considered to be a transmissible neoplasm with uncommon metastasis to regional lymph nodes and rare metastasis to other sites. Most growth is by local expansion and infiltration.
- The disease spreads via aerosol transmission and is less common in areas where the sheep are dispersed.
Pathogenesis
- The retrovirus associated with OPC is generally referred to as the jaagsiekte retrovirus (JSRV). This virus is morphologically distinct from all known retroviruses but has yet to be cultured.
- The target cells are type II alveolar epithelial cells and, less frequently, nonciliated bronchiolar epithelium.
- The virus-transformed epithelial cells proliferate, filling alveoli, spilling into adjacent airways and compressing and invading pulmonary parenchyma.
- The exact mechanism of carcinogenesis is unknown.
- Naturally occurring ovine pulmonary carcinomatosis has a long incubation period (months to up to 2 years), but experimentally, the time course of the disease can be reduced to a few weeks by inoculating lung tumor or lung fluid from affected sheep into neonatal lambs.
Clinical Signs
- Coughing
- Exercise intolerance (thus the Afrikaan name jaagsiekte, “driving sickness”).
- Crackles and wheezes.
- Abundant watery exudate which is discharged from the nose, especially when the head is lowered. The discharge is an important diagnostic clinical feature.
- Dyspnea.
Findings
Gross Findings
- Lung parenchymal masses ranging from 1 – 20 mm dia. gray-blue-white nodules (early) to large gray nodular and confluent masses (later). The larger masses often have fibrotic centers.
- The lungs are enlarged, heavy, and fail to collapse.
- Coexisting bronchopneumonia, verminous pneumonia, chronic progressive pneumonia, or combinations of the three.
- Right ventricular hypertrophy and dilation.
- Deaths result from heart failure, hypoxia or secondary bacterial pneumonias.
Laser Disc: 2395; 2396; 11702; 15547.
Microscopic Findings
- Multiple proliferative foci of cuboidal or columnar cells which line alveoli and form papillary projections into their lumina (i.e., adenomatous hyperplasia, adenomas and adenocarcinomas).
- In larger masses the pattern is obscured and fibroplasia often occurs in more disorganized and degenerative areas.
- Early or uncomplicated lesions may have little to no accumulation of inflammatory cells; however, there are usually low to moderate aggregations of alveolar macrophages in alveolar lumina.
Ultrastructure
Some cells have cytoplasmic lamellar bodies characteristic of alveolar type II epithelial cells; others have secretory granules and glycogen compatable with secretory bronchiolar epithelial (Clara) cell origin.
Differential Diagnosis
- Chronic progressive pneumonia (maedi - lentivirus) --lymphofollicular interstitial pneumonia (with little to no significant alveolar epithelial hyperplasia).
- Remember, bacterial bronchopneumonias and verminous pneumonias may be present in addition to OPC.
Comparative Pathology
- Human bronchio‑alveolar carcinoma shares many histologic and behavioral characteristics with OPC.
- Type D retroviruses have been implicated in caprine and ovine nasal adenocarcinomas.
References
1. Hecht SJ, Sharp JM, and Demartini JC: Retroviral Aetiopathogenesis of Ovine Pulmonary Carcinoma: A Critical Appraisal. Br Vet J (1996) 152:395-406. 2. Dungworth DL: The Respiratory System, In:Pathology of Domestic Animals, 4th edition, ed. Jubb KVF, Kennedy PC, and Palmer N, pp.690-2, Academic Press, San Diego, CA, 1993. 3. Fenner FJ, Gibbs EPJ, Murphy FA, Rott R, Studdert MJ, and White DO: Retroviridae, In: Veterinary Virology, 2nd edition, pp. 578-9, Academic Press, Inc., San Diego CA, 1993. 4. Kimberling CV: Diseases of Adult Sheep, In: Jensen and Swift’s Diseases of Sheep, 3rd edition, pp. 270-3, 1988.
Written and revised by GD Young, 1988; BH Williams, 1991; WD Fall, 1994; TO Johnson, 1999.