Test and vaccinate or remove: Methodology and preliminary results from a badger intervention research project.

BACKGROUND: In the British Isles, it is generally accepted that the Eurasian badger (Meles meles) plays a role in the maintenance of bovine tuberculosis (bTB) in cattle. Non-selective culling is the main intervention method deployed in controlling bTB in badgers along with smaller scale Bacillus Calmette-Guérin (BCG) vaccination areas. This paper describes the use of selective badger culling combined with vaccination in a research intervention trial. METHODS: In Northern Ireland, a 100 km2 area was subjected to a test and vaccinate or remove (TVR) badger intervention over a 5-year period. Badgers were individually identified and tested on an annual basis. Physical characteristics and clinical samples were obtained from each unique badger capture event. RESULTS: A total of 824 badgers were trapped with 1520 capture/sampling events. There were no cage-related injuries to the majority of badgers (97%). A low level of badger removal was required (4.1%-16.4% annually), while 1412 BCG vaccinations were administered. A statistically significant downward trend in the proportion of test positive badgers was observed. CONCLUSION: This is the first project to clearly demonstrate the feasibility of cage side testing of badgers. The results provide valuable data on the logistics and resources required to undertake a TVR approach to control Mycobacterium bovis in badgers.

A Bayesian analysis of a Test and Vaccinate or Remove study to control bovine tuberculosis in badgers (Meles meles).

A novel five year Test and Vaccinate or Remove (TVR) wildlife research intervention project in badgers (Meles meles) commenced in 2014 in a 100km2 area of Northern Ireland. It aimed to increase the evidence base around badgers and bovine TB and help create well-informed and evidence-based strategies to address the issue of cattle-to-cattle spread and spread between cattle and badgers. It involved real-time trap-side testing of captured badgers and vaccinating those that tested negative for bTB (BadgerBCG-BCG Danish 1331) and removal of those that tested bTB positive using the Dual-Path Platform VetTB test (DPP) for cervids (Chembio Diagnostic Systems, Medford, NY USA). Four diagnostic tests were utilised within the study interferon gamma release assay (IGRA), culture (clinical samples and post mortem), DPP using both whole blood and DPP using serum. BCG Sofia (SL222) was used in the final two years because of supply issues with BadgerBCG. Objectives for this study were to evaluate the performance of the DPP in field conditions and whether any trend was apparent in infection prevalence over the study period. A Bayesian latent class model of diagnostic test evaluation in the absence of a gold standard was applied to the data. Temporal variation in the sensitivity of DPP and interferon gamma release assay (IGRA) due to the impact of control measures was investigated using logistic regression and individual variability was assessed. Bayesian latent class analysis estimated DPP with serum to have a sensitivity of 0.58 (95% CrI: 0.40-0.76) and specificity of 0.97 (95% CrI: 0.95-0.98). The DPP with whole blood showed a higher sensitivity (0.69 (95% CrI: 0.48-0.88)) but similar specificity (0.98 (95% Crl: 0.96-0.99)). The change from BCG Danish to BCG Sofia significantly impacted on DPP serum test characteristics. In addition, there was weak evidence of increasing sensitivity of IGRA over time and differences in DPP test sensitivity between adults and cubs. An exponential decline model was an appropriate representation of the infection prevalence over the 5 years, with a starting prevalence of 14% (95% CrI: 0.10-0.20), and an annual reduction of 39.1% (95% CrI: 26.5-50.9). The resulting estimate of infection prevalence in year 5 of the study was 1.9% (95% CrI: 0.8-3.8). These results provide field evidence of a statistically significant reduction in badger TB prevalence supporting a TVR approach to badger intervention. They give confidence in the reliability and reproducibility in the DPP Whole Blood as a real time trap-side diagnostic test for badgers, and describe the effect of vaccination and reduced infection prevalence on test characteristics.

Bayesian estimation of the sensitivity and specificity of individual fecal culture and Paralisa to detect Mycobacterium avium subspecies paratuberculosis infection in young farmed deer.

A Bayesian latent class model was used to estimate the sensitivity and specificity of an immunoglobulin G1 serum enzyme-linked immunosorbent assay (Paralisa) and individual fecal culture to detect young deer infected with Mycobacterium avium subsp. paratuberculosis. Paired fecal and serum samples were collected, between July 2009 and April 2010, from 20 individual yearling (12-24-month-old) deer in each of 20 South Island and 18 North Island herds in New Zealand and subjected to culture and Paralisa, respectively. Two fecal samples and 16 serum samples from 356 North Island deer, and 55 fecal and 37 serum samples from 401 South Island deer, were positive. The estimate of individual fecal culture sensitivity was 77% (95% credible interval [CI] = 61-92%) with specificity of 99% (95% CI = 98-99.7%). The Paralisa sensitivity estimate was 19% (95% CI = 10-30%), with specificity of 94% (95% CI = 93-96%). All estimates were robust to variation of priors and assumptions tested in a sensitivity analysis. The data informs the use of the tests in determining infection status at the individual and herd level.

A matched cohort study investigating the risk of Mycobacterium bovis infection in the progeny of infected cows.

The aim of this study was to quantify the risk of bovine tuberculosis in the progeny of cows confirmed as having bovine tuberculosis. Historical computerised records were used to undertake a retrospective cohort study. The exposed cohort was defined as the last calf of dams that were diagnosed as having bovine tuberculosis during 2002. The progeny were only retained for subsequent analysis if they were born in the 9 months preceding slaughter of the dam and if they lived for more than 15 months. The unexposed cohort comprised of animals born in the same herd within 1 month of the exposed cohort and was matched one-to-one. The resultant dataset contained 1156 matched cohorts. Forty-two animals from the exposed cohort and 35 from the unexposed cohort had bovine tuberculosis. The relative risk was estimated at 1.2 (95% confidence interval 0.8-1.79). It was concluded that progeny of tuberculous dams were not at a significantly increased risk of Mycobacterium bovis infection.