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Correspondence: 1Corresponding Author: Dr. Beth A Valentine, College of Veterinary Medicine, Oregon State University, Magruder 142, Corvallis, OR 97331, e-mail: Beth.Valentine{at}oregonstate.edu
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Key Words: alpaca camelid llama neoplasia
ThereAuthor: This article has been lightly edited for grammar, style, and usage. Please compare it with your original document and make corrections on these pages. Please limit your corrections to substantive changes that affect meaning. If no change is required in response to a question, please write "OK as set" in the margin. Copy editor are numerous reports of neoplasia in South American camelids, including lymphoma,3,10,12,16,21,24,25 urogenital neoplasia,3,4,7,8,15,24,25 cutaneous and mucocutaneous neoplasia,17,20,23,25 oral neoplasia,1,2,14,24,26 intraocular neoplasia,3,5,11 malignant gastrointestinal neoplasia,22,25 mammary carcinoma,3,13,25 pulmonary neoplasia,18,19 neuroendocrine neoplasia,21 congenital hepatic neoplasia,27 osseous neoplasia,9 and neoplasia of the brain.6 Disseminated lymphoma is the most commonly reported tumor in llamas and alpacas.3,10,12,16,21,24,25 Only 2 prior studies have looked at overall prevalence and types of neoplasia in camelids.3,24 Excluding abortions, the prevalence of neoplastic disease in 72 llamas and alpacas submitted for necropsy examination at 1 laboratory over a 7-year period was 8.3%.24 Biopsy samples were not included in that study. A 1% prevalence of neoplasia was reported in a teaching hospital population of camelids, but that study was limited to malignant neoplasia.3
The purpose of this report is to describe the prevalence and types of neoplasia diagnosed by routine histopathologic evaluation in camelid biopsy and necropsy samples examined at the Veterinary Diagnostic Laboratory at Oregon State University, which provides service to an area in which llamas and alpacas are common livestock, over a 5-year period. Microscopic sections from all cases were reviewed by one author (BAV). Features of neoplasia in llamas were compared to those in alpacas. Tumor prevalence and mean age ± SD were calculated, and comparisons were performed using the Student's t-test assuming unequal variance. One case in this study has been previously reported.7
Excluding abortions, from July 2001 to July 2006 there were 551 camelid submissions for biopsy or necropsy examination. Submissions were from 368 alpacas (Lama pacos) and 180 llamas (Lama glama); species was not identified in 3 cases. Forty neoplasms were identified in 38 animals (overall prevalence of 6.9%). Results are summarized in Table 1. Thirty-four animals were from the Pacific Northwest, 3 were from the Midwest, and 1 was from Colorado. Neoplasia was identified in 20 llamas (11% prevalence) and 18 alpacas (4.9% prevalence). Neoplasia occurred in 21 females and 14 males (intact and castrated); gender of 3 animals was not specified. Excluding tumors of mammary gland and genital tract, no gender bias was apparent. Mean age of all camelids with neoplasia was 9.42 ± 4.9 years (range 0.2119 years). Mean age of alpacas with neoplasia (5.48 ± 3.7 years; range 0.2112 years) was significantly less than that of llamas with neoplasia (12.53 ± 3.2 years; range 519 years; P < 0.001).
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Disseminated lymphoma was diagnosed in 5 animals (4 alpacas and 1 llama), mean age 4.24 ± 6.2 years (range 0.2115 years). All alpacas with lymphoma were 4 years of age or less. Disseminated carcinoma or adenocarcinoma occurred in 4 llamas and 2 alpacas, and included tumors of biliary (2), gastrointestinal (2), mammary gland (1), and unknown (1) origin. Mean age of camelids with any type of carcinoma or adenocarcinoma (12.36 ± 2.8 years, range 817 years) was significantly greater than that of camelids with lymphoma (P = 0.02).
Cutaneous and oral fibroma/fibropapilloma was the most common neoplasm identified in this study, and was diagnosed in animals from 4 to 12 years of age. Multiple lesions, either submitted or reported in the history, were common (4 of 10 animals). Schulman et al.23 described mucocutaneous fibropapillomas with histopathologic features similar to equine sarcoid in five 6-year-old camelids with single to multiple lesions. Papillomavirus DNA was detected by polymerase chain reaction (PCR), and the causative virus was determined to be a unique papillomavirus.23 Several cases in this current study also had features similar to equine sarcoid, and most occurred on the head as previously reported.23 Others exhibited interlacing bundles of dense collagen more consistent with fibroma. This was particularly true of 2 of 3 tumors occurring on the distal limb and of the lesion on the hard palate. Overlying epithelium was not present for evaluation in all cases diagnosed as fibroma, and PCR testing for papillomavirus was not performed. Therefore, in this study all such lesions were grouped together with tumors diagnosed as fibropapilloma. It is suspected, however, that nonviral-associated fibroma may also occur in camelids.
Cutaneous and mucocutaneous squamous cell carcinoma was the most frequent malignant neoplasm identified in this population. Gastric squamous cell carcinoma has been reported in 5 South American camelids,22 but none were found in this study or in a prior survey.24 The prevalence of camelid squamous cell carcinoma in the Colorado study was also high, just slightly less than that of lymphoma, but tumor site was not specified.3
Lymphoma, the most common malignant neoplasm in camelids in 2 previous studies,3,24 was the second most common malignant neoplasm in this current study, and frequently occurred in young animals. The mean age of the 5 camelids with lymphoma (4.24 years) was very similar to that in a previous report of 10 cases (4.6 years).3 The diagnosis of lymphoma in this current study was based on gross pathologic and routine histopathologic findings of disseminated malignant round cell neoplasia. Sartin et al.21 found that 1 of 4 alpacas diagnosed as lymphoma based on gross pathologic and routine histopathologic examination did not express lymphocyte markers, and expression of neuron specific enolase and synaptophysin suggested neuroendocrine neoplasia. It is possible that some cases diagnosed as lymphoma in this study are neuroendocrine in nature, and additional immunohistochemical studies are needed.
Reports of disease processes typically combine data from llamas and alpacas. This study indicates that, as regards neoplasia, llamas and alpacas differ in prevalence, tumor types, and age affected. Overall prevalence of neoplasia was higher in llamas than in alpacas. Mean age of alpacas with neoplasia was, however, significantly lower than that of llamas with neoplasia. Regional differences may also exist regarding prevalence and type of neoplasia in llamas and alpacas.
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