Proceedings of the 10th International Colloquium on Paratuberculosis

agreement (�=0.696). The highest relative and complementary sensitivity values were
obtained with microbiological methods (RTi-PCR and Culture)(Table 1.).
DISCUSSION
Microbiological methods as well as histopathological examination corroborated that most
PTB infected animals were between 3 and 5 years old as traditionally described. Our
serological findings were in agreement with <strong>the</strong> assumption <strong>of</strong> <strong>the</strong> age <strong>of</strong> 2.5 to 4.5 years as
<strong>the</strong> highest risk <strong>of</strong> detecting antibodies against MAP suggested by o<strong>the</strong>r authors (Nielsen
Ersbøll, 2006). The fact <strong>of</strong> finding one seropositive 18 months-old animal with diffuse lesions
and MAP isolation from gut tissue may support <strong>the</strong> implication <strong>of</strong> animals younger than 2
years in horizontal MAP spread suggested by o<strong>the</strong>r authors (Wells et al., 2000).
With regard to diagnostic tests, RTi-PCR showed a similar sensitivity to MAP
isolation. The good agreement between ELISA and HP indicates that ELISA could be a good
predictor <strong>of</strong> intestinal lesion and <strong>the</strong>refore might anticipate clinical disease. However, <strong>the</strong>
poor complementary sensitivity <strong>of</strong> ELISA and culture and RTi-PCR indicates that humoral
immune response is a bad predictor <strong>of</strong> subclinical infection. Therefore, a combination <strong>of</strong> RTi-
PCR and ELISA appears to give <strong>the</strong> best chances to maximize PTB diagnosis.
CONCLUSION
Based on <strong>the</strong> yearly infection rates obtained from this study it seems appropriate to intensify
time testing at <strong>the</strong> age <strong>of</strong> 3-5 years in order to maximize <strong>the</strong> likelihood <strong>of</strong> detecting infected
animals before <strong>the</strong>y spent a too long time in <strong>the</strong> herd acting as a source <strong>of</strong> infection for <strong>the</strong>
rest <strong>of</strong> <strong>the</strong> susceptible animals. On <strong>the</strong> o<strong>the</strong>r hand, we can conclude that no single test can
detect all infected individuals and that, <strong>the</strong>refore, a combination <strong>of</strong> tests yields <strong>the</strong> maximum
sensitivity.
ACKNOWLEGMENTS
This study was funded by a grant from <strong>the</strong> Plan Nacional de Investigación Científica,
Desarrollo e Innovación Tecnológica. Ministerio de Ciencia e Inovación (MICINN). Spain.
(AGL2006-14315-CO2).
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