Interactions between cattle and badgers at pasture with reference to bovine tuberculosis transmission

The normal behaviour of badgers, as described here, would not result in direct transmission of tuberculosis from badgers to cattle via air expired by badgers or via bodily contact. All activities of wild badgers in cattle fields at three different sites were observed at night for a total of 359 h. In addition, all activities of pairs of wild caught badgers were observed in a 0.5 ha enclosure with an artificial sett on 20 nights when cattle were present. Badger foraging in cattle fields was infrequent during dry conditions and variable at other times. Clover fields were preferred to grass pastures in two autumnal studies and under dry conditions the badgers did not prefer to forage on short pasture. Badgers consistently avoided close contact with cattle by changing routes from sett to foraging site and by foraging much less in areas of fields occupied by cattle. When foraging they preferred to remain at least 10-15 m from cattle and they avoided compact groups of cattle more than individuals. Some cattle would move towards badgers, especially if they were carrying out unusual behaviour, but badgers fled rapidly from every approach. In all potential encounters badgers were able to keep at least 2-3 m from approaching cattle. Badgers in the artificial sett delayed entering the enclosure if cattle were within 15 m of the entrance. When cattle were managed on a strip-grazing (rotational) system the whole area which they occupied was avoided by the badgers. However, badgers came closer to individual cattle and foraged in areas grazed by the cattle more if the cattle were set-stocked. If cattle are managed so that they are concentrated in a small area (rotational) system the risk of disease transmission is minimized because they are less likely to encounter badgers or their fresh products than are cattle managed on a large area (set-stocked) system.     

Effects of farm management practices on cattle grazing behaviour and the potential for transmission of bovine tuberculosis from badgers to cattle

Despite the large body of circumstantial evidence to suggest a link, the means by which bovine tuberculosis is passed from badgers to cattle remains unclear; pasture contamination with the urine, faeces and/or sputum of infectious badgers is believed to be the main route of transmission. Therefore the behaviour of grazing cattle was studied to determine whether they avoided investigating and/or grazing pasture contaminated with badger excreta, and whether different farm management practices enhanced the potential for disease transmission. Active latrines were avoided by most cattle until the sward length in the rest of the field was reduced, after which there was an increasing likelihood that active badger latrines would be grazed. Most of the cattle grazed active badger latrines, but cattle of low rank within the herd grazed latrines more heavily. Farm management practices that reduced the availability of long swards shortened the period of investigative behaviour and greatly enhanced the risk that cattle would graze active badger latrines. Cattle were more likely to graze pasture away from latrines that was contaminated either with badger urine or single faeces. Because bacilli remain viable in the soil for up to 2 years, there is the potential for bacilli to accumulate at active badger latrines, and these could pose a significant risk to cattle, even when the latrine is no longer being used by badgers. Cattle readily grazed the lush sward at disused latrines, during which they could ingest contaminated soil; the amount of soil ingested increases as sward length decreases.     

Spatial relationship between Mycobacterium bovis strains in cattle and badgers in four areas in Ireland

We investigated whether strains (restriction fragment length polymorphism, RFLP-types) of Mycobacterium bovis isolated from badgers and from cattle clustered among and within four areas in Ireland. The spatial scan test and nearest-neighbor analysis were used as the spatial cluster-detection techniques. In addition, for each of the major strains, associations between the distance to badger setts and the "centroid" of the cattle farm were assessed in a logistic model. Overall, between September 1997 and May 2000, 316 and 287 M. bovis samples, from badgers and cattle, respectively, were strain-typed. The distribution of strains in badgers, and separately in cattle, differed among areas. Within each of the four large areas, badgers and cattle tended to have similar strains; this is consistent with the sharing of M. bovis strains within an area. In more detailed within-area analyses, some spatial clusters of M. bovis strains were detected, separately, in both cattle and badgers. Almost half of the infected badger setts with a specific strain were located outside of the "detected" clusters. There was no association between the number of infected badgers with a specific M. bovis strain within 2 or 5 km distances to cattle herds, and the risk of the same strain in cattle. We speculate about the dynamic nature of badger movements, as an explanation for the absence of more clusters of most of the strains of M. bovis isolated from badgers, and its impact on trying to study transmission of M. bovis between cattle and badger.