Proceedings of the 10th International Colloquium on Paratuberculosis

#103
Persistence <strong>of</strong> Mycobacterium avium subsp. paratuberculosis (Map) in field dried hay
fertilized with bovine slurry from Map infected herds
Arrigoni N, Cammi G, Belletti GL
Istituto Zoopr<strong>of</strong>ilattico Sperimentale della Lombardia e dell’Emilia Romagna, Piacenza, Italy
ABSTRACT
Objective: Use <strong>of</strong> Map contaminated slurry or manure to fertilize crop fields is generally considered a
risk factor for <strong>the</strong> Map transmission, although data on survival <strong>of</strong> Map in crops are sparse. Therefore,
<strong>the</strong> persistence <strong>of</strong> Map on crops fertilized during <strong>the</strong> autumn-winter period with slurry or manure
coming from Map infected herds was studied.
Methods: Ten Map infected herds with different prevalence levels <strong>of</strong> infection were selected. Culture
and PCR tests were performed on environmental samples collected from <strong>the</strong> infected farms to assess
<strong>the</strong> level <strong>of</strong> Map contamination. The same tests were performed on crop samples collected at three
different time-points: (1) on fresh hay before harvesting; (2) on hay after field drying; (3) on dried hay
at <strong>the</strong> beginning <strong>of</strong> its use for animal feeding.
Results: The environmental samples had massive presence <strong>of</strong> Map in <strong>the</strong> manure and slurry used to
fertilize <strong>the</strong> fields. The tests performed on <strong>the</strong> fresh hay samples, collected before harvesting, showed
a single positive result by PCR (10%) and were always negative by culture. The hay samples
collected after field drying and at <strong>the</strong> beginning <strong>of</strong> <strong>the</strong>ir use for animal feeding were always negative in
both culture and PCR.
Conclusion: These results suggested that under <strong>the</strong> described conditions, <strong>the</strong> contamination risk for
field dried hay, although possible, is <strong>of</strong> limited importance for <strong>the</strong> spreading <strong>of</strong> infection. On <strong>the</strong> o<strong>the</strong>r
hand this must not be underestimated in uninfected herds purchasing forage.
Key words: Paratuberculosis, forages, survival, slurry, manure
INTRODUCTION
Mycobacterium avium subsp. paratuberculosis (Map), <strong>the</strong> causal agent <strong>of</strong> Paratuberculosis, can
survive outside <strong>the</strong> animal for extended periods (163 days in river water, 270 days in pond water, 11
months in bovine faeces and soil, but only 7 days in urine) (1) . The fermentative processes in packed
manure should, if treated correctly, result in higher temperatures than in slurry, <strong>the</strong>reby also reducing
<strong>the</strong> risk <strong>of</strong> Map survival compared to in slurry (2). Map survival in bovine slurry has under experimental
conditions been demonstrated to be 98 days at 15 °C, but can reach 252 days at 5 °C (7)..
Because modern management procedures <strong>of</strong> dairy manure do not provide optimal conditions for Map
inactivation, control plans against Map usually recommend not to fertilize forages with slurry from Map
infected herds.. Spreading faeces on fields from which forage is later harvested and fed to animals <strong>of</strong>
any age group is statistically correlated to <strong>the</strong> risk <strong>of</strong> Map infection in <strong>the</strong> herd (3).
Therefore, <strong>the</strong> persistence <strong>of</strong> Map in crop fertilized during <strong>the</strong> autumn-winter period with slurry or
manure coming from bovine infected herds was studied.
MATERIAL AND METHODS
A serologic survey was carried out on bulk milk samples coming from <strong>the</strong> dairy herds <strong>of</strong> North Italy,
using an ELISA commercial kit (Institut Pourquier, France). Among <strong>the</strong> herds positive to <strong>the</strong> ELISA
test, 10 were selected because <strong>the</strong>y used to spread faeces on fields for forage use..
A visit in <strong>the</strong>se 10 farms was carried out to provide information about <strong>the</strong> incidence <strong>of</strong> clinical cases <strong>of</strong>
Paratuberculosis and procedures used to manage and spread manure and/or liquid slurry on fields..
The liquid slurry was stoked in lagoons (50%) or in intered containers (50%) and spread on forages
without an adequate period <strong>of</strong> maturation, unlike <strong>the</strong> manure. The manure and/or <strong>the</strong> slurry were
spread on <strong>the</strong> fields in autumn (45%) or winter (55%). The spread quantity varied from a minimum <strong>of</strong> 8
x 10 2 to a maximum <strong>of</strong> 5 x 10 4 Kg per hectare.
A serologic survey was carried out on individual milk samples <strong>of</strong> all <strong>the</strong> lactating cows <strong>of</strong> <strong>the</strong> herds (Kit
ELISA Institut Pourquier) to confirm that <strong>the</strong> clinical cases were related to Map infections and to
estimate <strong>the</strong> within-herd seroprevalence <strong>of</strong> Paratuberculosis..
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