Epidemiological Investigation of Bovine Tuberculosis Herd Breakdowns in Spain 2009/2011

Abstract

We analyzed the most likely cause of 687 bovine tuberculosis (bTB) breakdowns detected in Spain between 2009 and 2011 (i.e., 22% of the total number of breakdowns detected during this period). Seven possible causes were considered: i) residual infection; ii) introduction of infected cattle from other herds; iii) sharing of pastures with infected herds; iv) contiguous spread from infected neighbor herds; v) presence of infected goats in the farm; vi) interaction with wildlife reservoirs and vii) contact with an infected human. For each possible cause a decision tree was developed and key questions were included in each of them. Answers to these key questions lead to different events within each decision tree. In order to assess the likelihood of occurrence of the different events a qualitative risk assessment approach was used. For this purpose, an expert opinion workshop was organized and ordinal values, ranging from 0 to 9 (i.e., null to very high likelihood of occurrence) were assigned. The analysis identified residual infection as the most frequent cause of bTB breakdowns (22.3%; 95%CI: 19.4–25.6), followed by interaction with wildlife reservoirs (13.1%; 95%CI: 10.8–15.8). The introduction of infected cattle, sharing of pastures and contiguous spread from infected neighbour herds were also identified as relevant causes. In 41.6% (95%CI: 38.0–45.4) of the breakdowns the origin of infection remained unknown.Veterinary officers conducting bTB breakdown investigations have to state their opinion about the possible cause of each breakdown. Comparison between the results of our analysis and the opinion from veterinary officers revealed a slight concordance. This slight agreement might reflect a lack of harmonized criteria to assess the most likely cause of bTB breakdowns as well as different perceptions about the importance of the possible causes. This is especially relevant in the case of the role of wildlife reservoirs.

A review of risk factors for bovine tuberculosis infection in cattle in the UK and Ireland

“…It has been estimated through modelling that up to 24% of British herds had residual infection in at least one animal when restrictions were lifted [76]. This is congruent with estimates from a descriptive analysis in Spain, where 22% of incidents were determined to have been caused by residual cattle infection [287]. There is evidence that the TST is influenced in the presence of Johne's disease [29] and liver fluke [63,162] but the extent to which this might impede diagnosis is unknown.…”

Multiple sampling and discriminatory fingerprinting reveals clonally complex and compartmentalized infections by M. bovis in cattle

“…The presence of farms with two circulating strains is a finding that had been previously reported in Spain (Rodriguez-Campos et al, 2013) and it could result from contact with neighboring herds, residual infection or interaction with infected wild animals (Guta et al, 2014), since five of the six farms housing animals with compartmentalized infection has a semi-extensive management. To more accurately describe the infective context where our compartmentalized cases occurred, we genotyped additional animals from the farms housing these cases using MIRU-VNTR.…”

La gestión del lobo en España. Controversias científicas en torno a su caza

“…A igualdad de pérdida económica, es más impactante la presencia de un ternero muerto o herido que un prado levantado por las hozaduras de una piara de jabalíes. Además, entre los daños indirectos de los ungulados se encuentra la transmisión de enfermedades al ganado (Muñoz-Mendoza et al, 2013;Guta et al, 2014), que en la reserva de caza de Riaño representa la primera preocupación de los ganaderos, muy por encima que la causada por los daños del lobo. De veinte ganaderos de la reserva entrevistados en 2014, el 85% estaban preocupados por las enfermedades del ganado, el 20% por la proliferación de ciervos y jabalíes y solo el 5% estaban preocupados por el lobo (Exploring traditional husbandry methods to reduce wolf predation on freeranging cattle in Portugal and Spain).…”