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an epidemiological study of listeriosis in dairy cattle

an epidemiological study of listeriosis in dairy cattle

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a) Faecal samples:<br />

A total <strong>of</strong> 202 milk<strong>in</strong>g cows were exam<strong>in</strong>ed on this farm. Of these 28.2%<br />

(57/202) shed L. monocytogenes, 18.3 (37/202) L. <strong>in</strong>nocua, 1.5% (3) L. seeligeri <strong>an</strong>d<br />

52% (105/202) no Listeria spp. Dur<strong>in</strong>g the period <strong>of</strong> the <strong>study</strong> only 29.2% (59/202)<br />

milk<strong>in</strong>g cows were consistently sampled at each visit. The rest (70.2%, 143/202) were<br />

either removed from or <strong>in</strong>cluded <strong>in</strong> the milk<strong>in</strong>g herd dur<strong>in</strong>g the survey, therefore were<br />

sampled less frequently (Table 6. 5). Of these 59 <strong>an</strong>imals, 40.7% shed L.<br />

monocytogenes (24/59) 20.3% L <strong>in</strong>nocua (12/59), 3.4% L. seeligeri (2/59) <strong>an</strong>d the rest<br />

(35.6% 21/59) did not excrete <strong>an</strong>y species <strong>of</strong> Listeria.<br />

When the frequency <strong>of</strong> excretion was estimated for each month the lowest rates<br />

were observed between November <strong>an</strong>d February <strong>in</strong>clusive, around 1% <strong>of</strong> <strong>an</strong>imals shed<br />

Listeria spp. <strong>an</strong>d L. monocytogenes (Figure 6. 5). The highest proportion <strong>of</strong> <strong>an</strong>imals<br />

excret<strong>in</strong>g Listeria spp. <strong>an</strong>d L. monocytogenes were detected <strong>in</strong> March (43.3%, 52/120)<br />

<strong>an</strong>d October (21.4%, 27/126) respectively. These figures were signific<strong>an</strong>tly higher th<strong>an</strong><br />

those obta<strong>in</strong>ed <strong>in</strong> other months (P

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