Memoria para optar al Título Profesional de Médico Veterinario / El Scrapie es una enfermedad perteneciente al grupo de las EETs que afecta a ovejas y cabras. Este prototipo de enfermedad priónica, se caracteriza porque en las etapas iniciales de su patogenia el prión se deposita en los tejidos linforreticulares (TLR). Esta cualidad permite que se realicen pruebas diagnósticas preclínicas, en base a la detección de la proteína priónica patológica por medio de Inmunohistoquímica (IHQ) en zonas anatómicas donde es posible reconocer TLR. Según los informes entregado por la OIE en Chile no se han descritos casos de Scrapie, ni tampoco se posee sistema de vigilancia sobre esta enfermedad., No obstante, se establece que si se llegasen a presentar casos, estos se deben declarar obligatoriamente. Sin embargo, el SAG realiza vigilancia post mortem utilizando muestras de óbex con las que se llevan a cabo las técnicas diagnósticas de histopatología, IHQ y ELISA. Debido al potencial ganadero ovino del país, se hace importante poseer herramientas diagnósticas ante mortem de fácil realización, que permitan la implementación de programas de control epidemiológico en vivo. Es así como para esta memoria, se eligió el tejido de la mucosa rectal para validar la técnica diagnóstica por IHQ. Debido a que esta zona anatómica se caracteriza por presentar folículos linfoides dispersos cercanos a la unión recto anal, lo cual la hacen ser un área accesible por medio de una biopsia in vivo. A la vez, se realizó un análisis para determinar cual es la mejor región anatómica que permita obtener la mayor cantidad de folículos linfoides, ya que se requieren como mínimo 4 centros foliculares para realizar la técnica de IHQ con valor diagnóstico preclínico de Scrapie, reconocido internacionalmente. Para alcanzar este objetivo se trabajó con los últimos 4 cm del recto obtenidos de 54 ovinos mayores de 2 años, todos ellos provenientes de mataderos ubicados en la Región de Magallanes y Antártica Chilena. De cada trozo de recto, se analizaron 5 cortes a las distancias de 0,5; 1,0; 1,5; 2,0; 2,5 cm desde la línea recto anal hacia craneal. Estos cortes fueron sometidos a tinción de H/E, posteriormente se observaron e hizo un conteo de la presencia de folículos linfoides para así, clasificar la muestra como apta o no para realizar la IHQ. De esta manera, evaluando la aptitud de la muestra se observó que de los 54 individuos, en 33 (61%) al menos una de las cinco muestras fue considerada como apta y en 21 (39%) de ellos, no se presentaron muestras aptas en ninguno de sus cortes. Una vez obtenido los datos de la cantidad de folículos presentes por corte estos se sometieron a un análisis estadístico de chi cuadrado (2), el que arrojó como resultado que la mejor zona para obtener una muestra útil para el diagnóstico, es el área comprendida entre los 0,5 y 1,5 cm desde la unión recto anal. Así, del total de 270 cortes obtenidos, 74 cortes fueron aptos para realizar la IHQ, correspondiente al 61,1 % de los individuos muestreados. Todos estos cortes fueron negativos a Scrapie al no presentar el precipitado granular rojo de la inmunotinción y al compararlos con controles positivos y negativo que se disponían. De esta forma, la técnica basada en la biopsia rectal entrega una herramienta potencialmente útil para el diagnóstico precoz del Scrapie, debido a que el tejido linfoide rectal es fácilmente accesible en ovinos vivos, lo que facilita una rápida toma de muestras con un mínimo malestar para el animal. Esta técnica tendrá su mayor efectividad cuando se utilice una biopsia obtenida en la zona comprendida entre los 0,5 y 1,5 cm desde la unión recto anal. Por lo tanto, con este estudio se logró estandarizar la zona más adecuada para la toma de muestra, por medio de una biopsia rectal in vivo, además de validar la técnica de IHQ en estos tejidos, para así utilizarla como posible técnica in vivo de screening en programas de cuarentena y control de Scrapie para el país / Financiamiento: Proyecto FIV no. 121014019102002

No description available.

No description available.

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are a group of invariably fatal neurodegenerative diseases of both humans and animals, thought to be caused by the abnormally folded prion protein PrPSc. Prion disease research continues to be faced by a number of difficult challenges. First, the unequivocal diagnosis of most prion diseases currently requires the post-mortem collection of central nervous system tissue, either for histological examination or Western blot analysis; second, a viable treatment for clinical stage disease has not yet been identified; third, the exact details of disease pathogenesis have not been elucidated; and fourth, the normal function of PrPC is not definitively known. The primary objective of the studies presented here was to diagnose prion disease in live animals, using Magnetic Resonance Imaging (MRI). Increases in T2 relaxation time and apparent diffusion coefficient (ADC) were observed very early following the infection of Syrian golden hamsters with the 263K strain of scrapie. These changes were evident well before the appearance of either clinical symptoms or the typical histological changes characteristic of prion disease, suggesting that they are the result of the progressive accumulation of fluid, and that this may constitute a novel early marker of prion disease pathogenesis. Following the establishment of this model system, a secondary objective was composed: to test the viability of a potential treatment (pentosan polysulphate) using a number of different treatment regimens. It was determined that pentosan polysulphate (PPS) was ineffective as a treatment unless it was administered intra-cerebrally very early in infection, although it was shown to slow the appearance of the histological hallmarks of prion disease. In response to the results of these studies, a potential model was proposed, relating PrP, aquaporin-4 (AQP4) regulation, and oedema. Although speculative, this model may have implications for both normal PrPC function and disease pathogenesis. / February 2009

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are a group of invariably fatal neurodegenerative diseases of both humans and animals, thought to be caused by the abnormally folded prion protein PrPSc. Prion disease research continues to be faced by a number of difficult challenges. First, the unequivocal diagnosis of most prion diseases currently requires the post-mortem collection of central nervous system tissue, either for histological examination or Western blot analysis; second, a viable treatment for clinical stage disease has not yet been identified; third, the exact details of disease pathogenesis have not been elucidated; and fourth, the normal function of PrPC is not definitively known. The primary objective of the studies presented here was to diagnose prion disease in live animals, using Magnetic Resonance Imaging (MRI). Increases in T2 relaxation time and apparent diffusion coefficient (ADC) were observed very early following the infection of Syrian golden hamsters with the 263K strain of scrapie. These changes were evident well before the appearance of either clinical symptoms or the typical histological changes characteristic of prion disease, suggesting that they are the result of the progressive accumulation of fluid, and that this may constitute a novel early marker of prion disease pathogenesis. Following the establishment of this model system, a secondary objective was composed: to test the viability of a potential treatment (pentosan polysulphate) using a number of different treatment regimens. It was determined that pentosan polysulphate (PPS) was ineffective as a treatment unless it was administered intra-cerebrally very early in infection, although it was shown to slow the appearance of the histological hallmarks of prion disease. In response to the results of these studies, a potential model was proposed, relating PrP, aquaporin-4 (AQP4) regulation, and oedema. Although speculative, this model may have implications for both normal PrPC function and disease pathogenesis.

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are a group of invariably fatal neurodegenerative diseases of both humans and animals, thought to be caused by the abnormally folded prion protein PrPSc. Prion disease research continues to be faced by a number of difficult challenges. First, the unequivocal diagnosis of most prion diseases currently requires the post-mortem collection of central nervous system tissue, either for histological examination or Western blot analysis; second, a viable treatment for clinical stage disease has not yet been identified; third, the exact details of disease pathogenesis have not been elucidated; and fourth, the normal function of PrPC is not definitively known. The primary objective of the studies presented here was to diagnose prion disease in live animals, using Magnetic Resonance Imaging (MRI). Increases in T2 relaxation time and apparent diffusion coefficient (ADC) were observed very early following the infection of Syrian golden hamsters with the 263K strain of scrapie. These changes were evident well before the appearance of either clinical symptoms or the typical histological changes characteristic of prion disease, suggesting that they are the result of the progressive accumulation of fluid, and that this may constitute a novel early marker of prion disease pathogenesis. Following the establishment of this model system, a secondary objective was composed: to test the viability of a potential treatment (pentosan polysulphate) using a number of different treatment regimens. It was determined that pentosan polysulphate (PPS) was ineffective as a treatment unless it was administered intra-cerebrally very early in infection, although it was shown to slow the appearance of the histological hallmarks of prion disease. In response to the results of these studies, a potential model was proposed, relating PrP, aquaporin-4 (AQP4) regulation, and oedema. Although speculative, this model may have implications for both normal PrPC function and disease pathogenesis.

Thesis (Ph. D.)--Washington State University, December 2008. / Title from PDF title page (viewed on Oct. 22, 2009). "College of Veterinary Medicine." Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.

Memoria para optar al Título Profesional de Médico Veterinario Departamento de Patología Animal / Las encefalopatías espongiformes transmisibles (EETs) son a un grupo de enfermedades neurodegenerativas, de progresión lenta y finalmente fatales. Afectan tanto a humanos como a los animales. Dentro de éstas, los ovinos pueden presentar una enfermedad que es conocida hace más de 250 años, el Scrapie. El agente etiológico del Scrapie y del resto de las encefalopatías espongiformes, se denomina “prión” (partícula infecciosa proteinácea), que corresponde a la forma alterada (PrPSc) de una proteína constitutiva de membrana celular (PrPC). El Scrapie, luego de presentar largos períodos de incubación, manifiesta un cuadro clínico principalmente neurológico con cambios de conducta, tremores e incluso convulsiones, además de prurito, perdida de lana, debilidad y deterioro de la condición corporal. La presentación de la enfermedad está fuertemente determinada genéticamente y se transmite en forma vertical y horizontal. Actualmente el país cuenta con varias técnicas diagnósticas para enfrentar la encefalopatía espongiforme que afecta a los bovinos (EEB), no así para el Scrapie. Por este motivo, esta memoria de título buscó demostrar que la técnica de inmunohistoquímica es completamente confiable para ser utilizada como herramienta diagnóstica del Scrapie, bajo las condiciones particulares del laboratorio Oficial del país, perteneciente al Servicio Agrícola y Ganadero (SAG). Se procesaron 100 muestras de tejido nervioso a nivel de óbex, provenientes de ovinos sanos clínicamente mayores de 2 años, sacrificados en mataderos de la XII región, con el propósito de aplicar la técnica inmunohistoquímica, además de describir los hallazgos histopatológicos más importantes a través de una tinción de H-E modificada. La totalidad de las muestras fueron negativas a Scrapie mediante la tinción inmunohistoquímica. Por otra parte, en las mismas muestras se pudieron observar a través 4 de la tinción histopatológica de H-E modificada para EETs, lesiones microscópicas inflamatorias, hemorrágicas, pigmentarias y otras sin lesiones, sin embargo resultaron ser inespecíficas y no se asociaron a ninguna enfermedad específica. La realización de la inmunohistoquímica presentó 100% de sensibilidad y especificidad, reafirmando que esta técnica es confirmatoria para el diagnóstico del Scrapie, tal y como lo recomienda la Organización Mundial de Sanidad Animal (OIE) / Servicio Agrícola y Ganadero SAG) y Proyecto FAVET /04-35

Scrapie ou paraplexia enzoótica dos ovinos é uma doença neurodegenerativa fatal que acomete ovinos e raramente caprinos. A doença é influenciada por polimorfismos nos códons 136, 154 e 171 do gene prnp que codifica a proteína priônica. Os animais podem ser susceptíveis ou resistentes, de acordo com as sequências alélicas observadas nos referidos códons. No Brasil ocorreram apenas casos de animais que foram importados, sendo o país considerado livre da doença. Neste trabalho foi realizada a genotipagem dos diferentes polimorfismos associados ao desenvolvimento do scrapie e a categorização em animais susceptíveis e resistentes. Foram sequenciadas 118 amostras provenientes de ovinos da raça Santa Inês criados em propriedades localizadas no Estado de São Paulo. Destas amostras foram identificados 6 alelos e 11 genótipos (ARQ/ARQ, ARR/ARQ, ARQ/AHQ, ARQ/VRQ, AHQ/AHQ, ARR/ARR, ARR/AHQ, VRQ/VRQ, ARQ/TRQ, TRR/TRR, TRQ/TRQ), dentre os quais o genótipo ARQ/ARQ teve ocorrência de 56,7%. Em nosso estudo foi detectada a presença da tirosina no códon 136, observação rara na medida em quenão existem relatos nacionais e relatos envolvendo a raça Santa Inês descrevendo este polimorfismo. Com os resultados obtidos, foi possível determinar a existência de grande variabilidade genética relacionada à raça Santa Inês no Estado de São Paulo, apesar da variabilidade, apenas 1,69% dos genótipos observados são extremamente resistentes ao scrapie. Estes dados demonstram que a raça nativa Santa Inês pode ser considerada potencialmente susceptível ao scrapie. / Enzootic paraplexia or scrapie is a fatal neurodegenerative disease affecting mainly sheep and rarely goats. The disease is influenced by polymorphisms at codons 136, 154 and 171 of prnp gene that encodes the prion protein. The animals may be susceptible or resistant to the development of the disease according to the allelic sequences observed in these codons. In Brazil there were only cases of scrapie in imported animals, therefore the country is considered free of the disease. This study performed the genotyping of different polymorphisms associated to the development of scrapie. Then, based on these findings the animals were categorized in resistant and susceptible. A total of 118 samples were sequenced from the Santa Ines sheep raised on properties located in the State of Sao Paulo. From these samples, 6 alleles and 11 genotypes were identified (ARQ / ARQ, ARR / ARQ, ARQ / AHQ, ARQ / VRQ, AHQ / AHQ, ARR / ARR, ARR / AHQ, VRQ / VRQ, ARQ / TRQ, TRR / TRR, TRQ / TRQ), the genotype ARQ / ARQ presented a frequency of 56.7%. It was also detected the presence of tyrosine at codon 136, which may be considered a rare observation, since there is no report regarding Santa Ines breeding presenting this polymorphism. These results showed the great genetic variability in Santa Ines in Sao Paulo and only 1,69% of the genotypes observed are extremely resistant to scrapie. These data demonstrate that the Santa Ines sheep can be considered potentially susceptible to scrapie.