02.02.2013 Views

Proceedings of the 10th International Colloquium on Paratuberculosis

Proceedings of the 10th International Colloquium on Paratuberculosis

Proceedings of the 10th International Colloquium on Paratuberculosis

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

#276<br />

Eliminati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> Mycobacterium avium subspecies paratuberculosis<br />

from dairy farms: fact or ficti<strong>on</strong>?<br />

Schukken YH * , Mitchell RM, Pradhan AK, Lu Z, Smith R, Cho J, Dressler J, Tauer LW, Gröhn<br />

YT<br />

Department <str<strong>on</strong>g>of</str<strong>on</strong>g> Populati<strong>on</strong> Medicine and Diagnostic Sciences, College <str<strong>on</strong>g>of</str<strong>on</strong>g> Veterinary<br />

Medicine, Cornell University, Ithaca, NY, USA;<br />

ABSTRACT<br />

In this key note paper, we discuss whe<str<strong>on</strong>g>the</str<strong>on</strong>g>r eliminati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> Mycobacterium avium subspecies<br />

paratuberculosis (MAP) from dairy farms is a realistic opti<strong>on</strong> for modern dairy farms.<br />

L<strong>on</strong>gitudinal observati<strong>on</strong>al studies have shown that farms may have low apparent prevalence<br />

<str<strong>on</strong>g>of</str<strong>on</strong>g> MAP for l<strong>on</strong>g periods <str<strong>on</strong>g>of</str<strong>on</strong>g> time. This is remarkable as it may be expected that a low<br />

prevalence would result in infecti<strong>on</strong> fade out from a substantial proporti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> farms. We<br />

present data that would indicate that <str<strong>on</strong>g>the</str<strong>on</strong>g> true MAP prevalence <strong>on</strong> dairy farms is much higher.<br />

Data from tissues collected at slaughter in cows from l<strong>on</strong>gitudinally studied herds show an<br />

apparent prevalence <str<strong>on</strong>g>of</str<strong>on</strong>g> infecti<strong>on</strong> in culled cows <str<strong>on</strong>g>of</str<strong>on</strong>g> approximately twenty-five percent. The<br />

reas<strong>on</strong>s for this high prevalence are discussed. The impact <str<strong>on</strong>g>of</str<strong>on</strong>g> this high prevalence for c<strong>on</strong>trol<br />

programs is evaluated using both ma<str<strong>on</strong>g>the</str<strong>on</strong>g>matical, ec<strong>on</strong>omical and molecular tools. We<br />

c<strong>on</strong>clude that eliminati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> MAP for most dairy farms is more ficti<strong>on</strong> than fact.<br />

INTRODUCTION<br />

Johne’s disease or paratuberculosis is an infectious disease in cows, caused by<br />

Mycobacterium avium subspecies paratuberculosis (MAP). In many countries, <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

prevalence <str<strong>on</strong>g>of</str<strong>on</strong>g> MAP in dairy herds has been estimated, and <str<strong>on</strong>g>the</str<strong>on</strong>g>se estimates are usually very<br />

close. Most studies show an apparent prevalence <str<strong>on</strong>g>of</str<strong>on</strong>g> infected cows in herds in <str<strong>on</strong>g>the</str<strong>on</strong>g> 5-10%<br />

range (Woodbine et al. 2009, VanSchaik et al. 2003). Given this low estimated prevalence, it<br />

is surprising that no reports have been published <strong>on</strong> l<strong>on</strong>g term infecti<strong>on</strong> free herds.<br />

Fig. 1. Prevalence <str<strong>on</strong>g>of</str<strong>on</strong>g> shedding, infected animals and <str<strong>on</strong>g>the</str<strong>on</strong>g> incidence <str<strong>on</strong>g>of</str<strong>on</strong>g> MAP infecti<strong>on</strong> during a<br />

20-year l<strong>on</strong>gitudinal study in a dairy herd going through a MAP c<strong>on</strong>trol program (from<br />

Benedictus et al. 2007).<br />

Most studies that report <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> implementati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> c<strong>on</strong>trol programs, report a dramatic<br />

decrease in incidence and prevalence, but never a full eliminati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> infecti<strong>on</strong>. An<br />

example <str<strong>on</strong>g>of</str<strong>on</strong>g> such a c<strong>on</strong>trol program in a well m<strong>on</strong>itored dairy herd is shown in Figure 1<br />

109

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!