This explains the earlier identification of local herd density as risk predictor [ 7].
Nevertheless, the alteration in the profile of the lactation curve may pose an opportunity of early identification of a herd reproductive problem that reaches beyond estrus detection and A.I. management.
The matrix was built in the following way: evaluation of all possible pathways (succession of edges) between two herds for each pair of herds; identification of the shortest path(s) between each pair of herds.
Every prescription is registered with identification of veterinarian and herd, drug identification, quantity of antimicrobial and disease group.
These epidemiological investigations evaluate movement of cattle up to five years previous to the time of identification of an affected herd [ 3].
If M. bovis is confirmed in a herd, the subsequent investigation may include identification of all epidemiologically linked (contact) herds: adjacent (immediate neighboring) and surrounding herd(s) (in the vicinity), trace-ins to find the source of infection, and trace-outs through registered sales and livestock auction markets to find other exposed animals and herds [ 3],[ 20].
As the likelihood of detecting at least one test positive animal increases with the number of individual samples collected per herd, identification of clusters and their spatial location might be biased if the herds from which two or more blood samples (19% of the studied herds) were collected are not evenly geographically-distributed.
Re-testing of herds after the identification of a 'standard reactor' or an 'inconclusive reactor', at two-month intervals also aims at reducing the likelihood of misclassifying animals due to this effect.
Nonetheless, detailed knowledge about individual risk factors for suckling pigs is lacking, although the identification of risk factors in individual herds, mainly comprised by husbandry and management factors, and their reduction is a prerequisite for disease control and prevention.
Introduction of the IFN-γ assay for the identification of infected animals in positive herds resulted in an increase on the values of βt (Table 1), likely as a consequence of an increase in the sensitivity of the detection, as expected when this technique is used as an ancillary test [ 18, 19].
