Comparison of two coprological methods for the veterinary diagnosis of fasciolosis Comparação de dois métodos coprológicos para diagnóstico da fasciolose

The sensitivity and utility of a standard faecal sedimentation method (FSM) and a modified stool sieving staining method (FSSM), both currently employed for the diagnosis of Fasciola hepatica infection were compared. Faecal samples were obtained from 51 bovines of an endemic area for fasciolosis in Southwestern Argentina. Each sample was placed in a recipient containing 5% formalin. Eight millilitres of the suspension, equivalent to 2g of faeces, were used for each of the two methods tested. The number of eggs found per sample was recorded. The proportion of positive samples obtained by the FSSM (27/51) was significantly higher than that by the FSM (11/51) (P<0.05). The percent of agreement between methods was 41%. Over a total of 27 positive samples detected by the FSSM, the FSM missed 16, yielding 60% false negative samples. The FSSM enhanced 2.5 times the sensitivity of diagnosis. The complexity of the FSM may decrease its sensitivity through missing and loss of eggs during sample processing. These results confirmed that the commonly used FSM underestimates the prevalence and the egg output in cattle and that the FSSM is a more reliable diagnostic method.<br>Compararam-se a sensibilidade dos métodos padrão de sedimentação fecal (MPSF) e modificado da tamisação e coloração das fezes (MTCF)-quatro tamises, ambos empregados no diagnóstico de infecção por Fasciola hepatica. Amostras de fezes foram obtidas de 51 bovinos oriundos de uma área endêmica por fasciolose no Sudoeste da Argentina. Cada amostra foi colocada em um recipiente contendo formalina 5%. Oito mililitros da suspensão, equivalente a 2g de fezes, foram usados em cada método testado, registrando-se o número de ovos por amostra. A porcentagem de amostras positivas pelo MTCF (27/51) foi maior que a apresentada pelo MPSF (11/51), o que representou 60% de amostras falso-negativas. A porcentagem de concordância pelos dois métodos foi 41%. A complexidade do MPSF pode diminuir sua sensibilidade pela perda de ovos durante o processamento. Estes resultados confirmaram que o MPSF subestima a contagem de ovos e que o método MTCF é mais confiável.