BIOPSIA RETAL EM OVINOS E CAPRINOS PARA MONITORAMENTO E DIAGNÓSTICO ANTE MORTEM DE SCRAPIE: NÚMERO DE FOLÍCULOS LINFOIDES EM DUAS COLHEITAS CONSECUTIVAS

This study aimed to evaluate the amount of lymphoid tissue associated with the rectal mucosa obtained by rectal biopsy and the possibility of two consecutive biopsies at different time intervals, for monitoring and ante-mortem diagnosis of scrapie. Rectal mucosa samples were collected from 56 sheep and 32 goats in two steps. In the first step, on day 0, all animals were tested and, for the second step, the animals were divided into groups and each group was subjected to collection on different dates: for sheep 7, 14, 21, and 28 days after the first one and, for goats, on days 14, 21, and 28. From 176 samples, 151 (85.8%) were collected from the rectal mucosa, and in 25 (14.2%) there was a collection failure. Considering the rectal mucosa samples (151), 56.86% of the sheep samples and 51.61% of the goat samples, on day 0, had more then ≥3 lymphoid follicles (LF). In the second collection, 58.97% of the sheep samples showed ≥ 3 LF and 33.33% of the goat samples. Comparing the number of LF of the same animals between the first and second collections, there was a significant difference (p <0.05) between days 0 and 7 for sheep (with more FL on day 0) and days 0 and 28 (with more LF on day 28) and days 0 and 28 for goats (with more FL on day 0). There was no significant difference in the number of FL assessed on dates 0, 14, and 21 when comparing the different species, sheep and goats. On day 28, sheep samples showed a higher number (p <0.05) of LF than goats. It was concluded that rectal biopsy technique involves useful method for obtaining lymphoid tissue associate to mucosa for immunohistochemistry assessment to monitoring and ante-mortem diagnosis of scrapie in sheep and goats. However, inappropriate sampling or insufficient numbers of FL can generate the necessity to repeat the technique, which could be done 14 days after the first collection, without reduction in the number of the FL.