Department of Health Services Research, Management, and Policy, University of Florida, Gainesville, USA.
Vet Q. 2013;33(1):25-9. doi: 10.1080/01652176.2013.772690. Epub 2013 Mar 12.
Captive elephants infected with tuberculosis are implicated as an occupational source of zoonotic tuberculosis. However, accurate estimates of prevalence and incidence of elephant tuberculosis from well-defined captive populations are lacking in the literature. Studies published in recent years contain a wide range of prevalence estimates calculated from summary data. Incidence estimates of elephant tuberculosis in captive elephants are not available.
This study estimated the annual point prevalence, annual incidence, cumulative incidence, and incidence density of tuberculosis in captive elephants within the USA during the past 52 years.
We combined existing elephant census records from captive elephants in the USA with tuberculosis culture results obtained from trunk washes or at necropsy. This data set included 15 years where each elephant was screened annually.
Between 1960 and 1996, the annual point prevalence of tuberculosis complex mycobacteria for both species was 0. From 1997 through 2011, the median point prevalence within the Asian elephant population was 5.1%, with a range from 0.3% to 6.7%. The incidence density was 9.7 cases/1000 elephant years (95% CI: 7.0-13.4). In contrast, the annual point prevalence during the same time period within the African elephant population remained 0 and the incidence density was 1.5 cases/1000 elephant years (95% CI: 0.7-4.0).
The apparent increase in new cases noted after 1996 resulted from a combination of both index cases and the initiation of mandatory annual tuberculosis screening in 1997 for all the elephants. This study found lower annual point prevalence estimates than previously reported in the literature. These discrepancies in prevalence estimates are primarily due to differences in terminology and calculation methods. Using the same intensive testing regime, the incidence of tuberculosis differed significantly between Asian and African elephants.
Accurate and species specific knowledge of prevalence and incidence will inform our efforts to mitigate occupational risks associated with captive elephants in the USA.
感染结核病的圈养大象被认为是动物源性结核病的职业传染源。然而，文献中缺乏来自明确圈养种群的大象结核病患病率和发病率的准确估计。近年来发表的研究包含了从汇总数据计算得出的广泛范围的患病率估计。圈养大象中结核病的发病率估计值尚不可用。
本研究估计了过去 52 年中美国圈养大象中结核病的年时点患病率、年发病率、累积发病率和发病率密度。
我们将美国圈养大象的现有普查记录与从气管冲洗液或尸检中获得的结核分枝杆菌培养结果相结合。该数据集包括 15 年，其中每只大象每年都接受筛查。
1960 年至 1996 年，两种物种的结核病复合分枝杆菌的年时点患病率均为 0。1997 年至 2011 年，亚洲象种群内的中位数时点患病率为 5.1%，范围为 0.3%至 6.7%。发病率密度为 9.7 例/1000 头年（95%CI：7.0-13.4）。相比之下，同期非洲象种群的年时点患病率仍为 0，发病率密度为 1.5 例/1000 头年（95%CI：0.7-4.0）。
1996 年后新病例的明显增加是由于索引病例的综合影响，以及 1997 年对所有大象强制实施年度结核病筛查的开始。本研究发现的年时点患病率估计值低于文献中先前报道的值。这些患病率估计值的差异主要是由于术语和计算方法的不同。使用相同的强化检测方案，亚洲象和非洲象的结核病发病率存在显著差异。
准确的、具有物种特异性的患病率和发病率知识将有助于我们努力减轻美国圈养大象相关的职业风险。
