Proceedings of the 10th International Colloquium on Paratuberculosis

#205
Sensitivity <strong>of</strong> environmental sampling for paratuberculosis
Weber MF 1 , van Maanen C 1 , von Bannisseht-Wijsmuller T 1 , Lam TJGM 1
1 GD Animal Health Service, Deventer, The Ne<strong>the</strong>rlands
INTRODUCTION
Environmental sampling (ES) has been recommended in <strong>the</strong> U.S. for classification <strong>of</strong> dairy
herds as infected or not infected (Collins et al., 2006), based on studies in US dairy herds
(Raizman et al., 2004; Lombard et al., 2005; Berghaus et al., 2006). However, <strong>the</strong> diagnostic
test characteristics <strong>of</strong> ES in Dutch dairy herds were unknown. Therefore, <strong>the</strong> aim <strong>of</strong> this
study was to quantify <strong>the</strong> relative sensitivity <strong>of</strong> ES in comparison to <strong>the</strong> test-scheme <strong>of</strong> <strong>the</strong>
initial assessment <strong>of</strong> <strong>the</strong> Dutch Bulk Milk Quality Assurance Program (BMQAP), i.e.
individual milk samples <strong>of</strong> all lactating cattle followed by confirmatory fecal culture.
MATERIALS AND METHODS
In 246 herds with � 1 milk-ELISA-positive cattle in <strong>the</strong> initial herd assessment <strong>of</strong> <strong>the</strong> BMQAP,
a pooled sample from <strong>the</strong> slurry pit and a pooled fecal sample from cow alleyways were
collected. At <strong>the</strong> same point in time, individual fecal samples were collected from all ELISApositive
cattle. All samples were cultured on modified Löwenstein-Jensen media (Kalis et al.,
1999; Kalis et al., 2000).
RESULTS
In 216 (88%) <strong>of</strong> <strong>the</strong> 246 herds, �1 milk-ELISA-positive cattle were found to be individual fecal
culture-positive. In <strong>the</strong> remaining 30 herds, all ELISA-positive cattle were individual fecal
culture-negative. These 30 herds were excluded from our analyses because <strong>the</strong>y were
considered test-negative in <strong>the</strong> initial assessment <strong>of</strong> <strong>the</strong> BMQAP.
The pooled sample from <strong>the</strong> slurry pit was culture-positive in 199 (92%) <strong>of</strong> <strong>the</strong> 216 herds with
�1 cattle being both ELISA- and fecal culture-positive. The pooled sample from <strong>the</strong> cow
alleyways was culture positive in 189 (88%) <strong>of</strong> <strong>the</strong> 216 herds. In 205 (95%) <strong>of</strong> <strong>the</strong> 216 herds,
at least one <strong>of</strong> <strong>the</strong>se pooled samples was culture-positive. Therefore, <strong>the</strong> relative diagnostic
sensitivity (exact 95% CI) <strong>of</strong> culture <strong>of</strong> a pooled sample from <strong>the</strong> slurry pit, a pooled sample
from <strong>the</strong> cow alleyways, and parallel testing <strong>of</strong> a pooled sample from <strong>the</strong> slurry pit and a
pooled sample from <strong>the</strong> cow alleyways was 92% (88%, 95%), 88% (82%, 92%) and 95%
(91%, 97%), respectively.
DISCUSSION
ES was found to have a reasonably high relative sensitivity in comparison to <strong>the</strong> test-scheme
<strong>of</strong> <strong>the</strong> initial assessment <strong>of</strong> <strong>the</strong> Dutch BMQAP. However, if ES would have been used as a
pre-screening prior to individual milk sampling, 5% to 12% <strong>of</strong> herds would have tested falsenegative.
It is yet unknown whe<strong>the</strong>r <strong>the</strong> infection in <strong>the</strong>se herds could be detected by
repeated environmental samplings. Fur<strong>the</strong>rmore, <strong>the</strong> relative specificity <strong>of</strong> ES in ELISAnegative
herds and <strong>the</strong> relative sensitivity <strong>of</strong> ES as compared to <strong>the</strong> test-regimen for
surveillance <strong>of</strong> certified herds are yet unknown. Finally, in small to medium sized herds, <strong>the</strong>
costs <strong>of</strong> ES exceed <strong>the</strong> costs <strong>of</strong> testing by milk-ELISA. We conclude that fur<strong>the</strong>r research is
needed to solve <strong>the</strong>se issues.
REFERENCES
Berghaus RD, Farver TB, Anderson RJ, Jaravata CC, Gardner IA, 2006. Environmental sampling for
detection <strong>of</strong> Mycobacterium avium ssp. paratuberculosis on large California dairies. J. Dairy Sci.
89, 963-970.
Collins MT, Gardner IA, Garry FB, Roussel AJ, Wells SJ, 2006. Consensus recommendations on
diagnostic testing for <strong>the</strong> detection <strong>of</strong> paratuberculosis in cattle in <strong>the</strong> United States. J. Am. Vet.
Med. Assoc. 229, 1912-1919.
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