Herd-Level Prevalence and Within-Herd Prevalence in Infected Herds
According to the survey data of Whittington et al. (2019), respondents of very few countries reported a herd-level prevalence of less than 1%, based on objective laboratory test data (Fig.
21.2a). A significant association between herd size and herd-level prevalence of paratuberculosis for dairy cattle was present: for each one log increase in herd size the odds of a country having a higher category of prevalence increased by 9.7 (p = 0.001; 95% CI 1.9-48.8).Only a few countries had an average within- herd prevalence of less than 1%, based on objective laboratory test data (Fig. 21.2b). An average within-herd prevalence estimate >10% for most species was common. Within-herd prevalence was unknown in 12 countries with dairy cattle, 18 with beef cattle, 26 with sheep and 2 7 with goats.
In 18 of 48 countries, MAP infection is present in free-living ruminants and wildlife. Those countries show no geographic clustering, however, contact with farmed livestock and wildlife has been documented. A great variety of species were affected including omnivorous, herbivorous and carnivorous mammals and even some birds (see Chapter 15 this volume for more information on infection in non-ruminant wildlife). In 26 countries, the MAP prevalence in wildlife was unknown.
21.3