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Questions and Answers
Which neoplastic disease in sheep is characterized by pearly white nodules in the lungs?
What is the characteristic appearance of neoplastic lesions in the small intestine in sheep?
What distinguishes the atypical presentation of Ovine Pulmonary Adenocarcinoma from the classical form?
What are common clinical signs of Ovine Mammary Gland Carcinoma in sheep?
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Which statement about OPA and OMGC is true?
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What is the main defining characteristic of neoplasia according to Willis?
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What are some similarities between neoplastic diseases in sheep and human tumors?
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Where is small intestinal adenocarcinoma (SIA) highly prevalent according to the text?
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What is the typical age range for animals affected by small intestinal adenocarcinoma (SIA)?
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How do sheep clinically affected by SIA typically behave based on available descriptions?
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In which inspected adult sheep population did the prevalence of SIA range from 0.2 to 1.6%?
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What are some common symptoms exhibited by sheep affected by small intestinal adenocarcinoma?
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Study Notes
Neoplasia in Sheep: An Overview of Small Intestinal Adenocarcinoma and Other Neoplastic Diseases
Neoplasia, defined by Willis as "an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the surrounding normal tissues, and persists in the same excessive manner after cessation of the stimuli which evoked the change," is a common cause of weight loss and emaciation in sheep. Despite its relative infrequency in this species, there are three main neoplastic diseases of economic relevance in the sheep industry.
Small Intestinal Adenocarcinoma
Small intestinal adenocarcinoma (SIA) is a naturally occurring neoplasia of the small intestine in sheep, which is highly prevalent in some countries like New Zealand and Australia. It is also commonly recorded in Scotland, Norway, and Iceland, with sporadic cases reported elsewhere in the world. SIA occurs at all ages but is mostly recorded in animals aged 5-7 years old. The prevalence of SIA in abattoir studies ranged from 0.2 to 1.6% in inspected adult sheep in New Zealand, Scotland, and Australia[6, 7].
Clinically, recorded cases of SIA did not include detailed descriptions of the affected sheep because they were often found dead before examination. In the few instances where clinical descriptions are available, first signs were not specific, and sheep looked dull, separated from the mob during delivery, walked with a rolling gait, and showed signs of constipation. The neoplastic lesions in the small intestine can be grey or purple in color, not protruding significantly on the surface, and have increased consistency. The cut surface of the tumor lesion has a granular appearance and is moist, and a frothy fluid pours from the bronchioles and bronchi with slight pressure.
Other Neoplastic Diseases in Sheep
In addition to SIA, there are two other neoplastic diseases of economic relevance in the sheep industry: ovine pulmonary adenocarcinoma (OPA) and ovine mammary gland carcinoma (OMGC). These diseases are of interest for comparative oncology due to their similarities to respiratory and digestive human tumors[4, 5].
OPA is characterized by two pathological forms: classical and atypical. In the classical presentation, the lungs do not collapse when the chest is opened and are enlarged, with neoplastic lesions occurring in any part of the lungs but more frequently in cranio-ventral parts. The cut surface of the tumor lesion has a granular appearance and is moist, and a frothy fluid pours from the bronchioles and bronchi with slight pressure. In contrast, the atypical presentation is more nodular in both early and advanced tumors, with the nodules often located in the diaphragmatic lobes. These nodules are pearly white in color and have a very hard consistency. Both forms may be present in a flock and in individual sheep, and intermediate and mixed forms have been described.
OMGC is one of the main causes of mammary gland neoplasia in sheep. The tumors are often benign and show no signs of invasion, but malignant forms have been reported. The clinical signs of OMGC are not specific and include swollen teats, lameness, and loss of appetite. The tumors may be unilateral or bilateral, and the size varies from a few millimeters to several centimeters.
Conclusion
Neoplasia in sheep, particularly small intestinal adenocarcinoma, is a common cause of weight loss and emaciation, with economic relevance for leading sheep-rearing countries. Understanding the epidemiology, clinical features, and pathology of these neoplastic diseases is crucial for effective diagnosis and treatment. Comparative oncology studies can also provide valuable insights into human cancer research.
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Description
Explore the key neoplastic diseases affecting sheep, focusing on Small Intestinal Adenocarcinoma (SIA), Ovine Pulmonary Adenocarcinoma (OPA), and Ovine Mammary Gland Carcinoma (OMGC). Learn about the epidemiology, clinical features, and pathology of these conditions in sheep.
