Wide geographical variations in cattle tuberculosis in England
In Wales incidence and prevalence have decreased. Incidence and revalence are highest in the High Risk Area of England (HRA) and lowest in the Low Risk Area of England (LRA) and in Scotland.
Between the 12 months ending December 2016 and the previous 12 month period, there was a decrease in the number of new TB incidents in the HRA, LRA, Wales and Scotland.
In the Edge Area of England there was an increase in the number of incidents.
Prevalence at end December 2016 (the percentage of herds which were not Officially TB Free (OTF) due to a TB incident) increased in the Edge Area of England and decreased in the HRA and LRA compared to December 2015.
In Scotland the number of non-OTF herds is very low and approximately 45% of cattle herds are now exempt from routine TB surveillance testing.
In Scotland and the LRA, there are proportionately more false positive results to the tuberculin skin test than elsewhere in GB.
Consequently it is also important to consider the number of new TB incidents where OTF status is withdrawn (OTFW) following confirmation of TB by postmortem examination or laboratory culture of tissue samples.
During the 12 months ending December 2016 there were 38 such incidents in the LRA, compared to 51 in the previous 12 months. In Scotland there were 9 OTFW incidents in the period ending September 2016 and 10 in the 12 months to end September 2015.
The OTFW incidence rate in the LRA was 0.3 breakdowns per 100 herd-years at risk in both periods.
In Scotland the OTFW incidence rate of breakdowns per 100 herd-years was 0.1 in both periods. ■