Assessing the Effectiveness of Tuberculosis Management in Brushtail Possums (Trichosurus vulpecula), through Indirect Surveillance of Mycobacterium bovis Infection Using Released Sentinel Pigs

Table 3

Comparison of TB prevalence rates among released sentinel and resident wild pigs in the Molesworth and Clarence study areas, following the release and recovery of 51 M. bovis-naïve sentinel pigs into the areas between May 2009 and July 2010.

	Number of pigs (gender)	Average (range) duration of postweaning exposure in days	TB prevalence as percentage (95% CI)	Average lesion severity score among culture-positive cases (95% CI)	AAI of new infections over the exposure period
Molesworth
Released sentinels	40 (22f, 18m)	259 (147–361)	20.0 (7–33)	2.6 (0.7–4.5)	0.28
Residents	59 (30f, 29m)	219 (122–397)	33.9 (21–46)	2.0 (1.7–2.3)	0.42
Clarence
Released sentinels	11 (6f, 5m)	180 (104–298)	54.5 (19–90)	2.0 (1.1–2.9)	1.11
Residents	17 (9f, 8m)	260 (92–366)	70.6 (46–95)	2.7 (2.0–3.5)	1.36

Fifty-one purpose-reared sentinel pigs were released in the two areas between May 2009 and July 2010 and then recovered at various times between January 2010 and April 2011 for necropsy, by which time the animals had received 104–361 days of exposure to the endemic force of infection. One hundred and fifty-three resident pigs were identified as having been born in the area between March 2009 and May 2010 (and thus susceptible to infection, postweaning, between May 2009 and July 2010) and, from these, 76 animals were selected as having similar exposure duration to the sentinels before they were killed and necropsied (i.e., they had been exposed to the same force of infection in the same area and over the same time period as the released sentinels).