Evaluation of Serodiagnostic Assays forMycobacterium bovisInfection in Elk, White-Tailed Deer, and Reindeer in the United States

Abstract

In 2011, the United States Department of Agriculture conducted a project in which elk (Cervus elaphus spp.), white-tailed deer (WTD) (Odocoileus virginianus), and reindeer (Rangifer tarandus) were evaluated by the single cervical tuberculin test (SCT), comparative cervical tuberculin test (CCT), and serologic tests. The rapid antibody detection tests evaluated were the CervidTB Stat-Pak (Stat-Pak), and the Dual Path Platform VetTB (DPP). Blood was collected from presumably uninfected animals prior to tuberculin injection for the SCT. A total of 1,783 animals were enrolled in the project. Of these, 1,752 (98.3%) were classified as presumably uninfected, based on originating from a captive cervid herd with no history of exposure to TB. Stat-Pak specificity estimates were 92.4% in reindeer, 96.7% in WTD, and 98.3% in elk and were not significantly different from SCT specificity estimates. Using the DPP in series on Stat-Pak antibody-positive samples improved specificity in the three species. Thirty one animals were classified as confirmed infected, based on necropsy and laboratory results, and 27/31 were antibody positive on Stat-Pak for an estimated sensitivity of 87.1%. The study findings indicate that rapid serologic tests used in series are comparable to the SCT and CCT and may have a greater ability to detect TB-infected cervids.

Validation of laboratory tests for infectious diseases in wild mammals: review and recommendations

“…Only a few non-M. bovis studies discussed the representativeness of source populations, including the cross-boundary collaboration between Canada and the United States to address chronic wasting disease (CWD) in white-tailed deer 111 and the validation of tests for Trichinella infections in wild boar in Sweden. 21 Additional examples of lack of representativeness between source and target populations can be also be found in other studies, 76 such as the use of a mix of experimental and field infection data, and for analysis of pooled data from wild and farmed mammals. In these instances, it is difficult to address how well the sampled animals matched the target population defined in the research question, which is a metric of internal validity of the study.…”

“…95 For test validation studies using multiple species, estimates of DSe and DSp were sometimes not reported separately for each species. 28,97 Sampling scheme: sample selection, quality, and quantity Sampling methods used in wild mammal populations are usually non-probability methods, such as convenience 76 or opportunistic sampling 90 because animals are often darted or trapped for sample acquisition. For example, the potential omission of follow-up samples for validation testing may result in over-or underestimation of DSe because of a lack of willingness of owners to allow an autopsy of M. bovis screening test-positive elk in a free-ranging herd.…”

“…Utilization of samples of known infection (archived) status was done in 20% of studies for diseases including African swine fever, Brucella abortus , epizootic hemorrhagic disease, hemorrhagic septicemia, Johne’s disease, and Trypanosoma cruzi . However, only 3 M. bovis studies 67,76,107 and 3 non– M. bovis studies 84,96,110 used field samples for validation of novel or existing tests in addition to the use of samples from reference animals or experimentally infected wild mammals. The latter sample types often result in overestimation of DSe and DSp.…”

“…For example, studies of M. bovis reported CIs for both DSe and DSp, with a few exceptions because of the sample sizes available. 8,76 Postmortem methods were shown to have DSp close to 100% with narrower CIs but low DSe with wide CIs (Suppl. Figs.…”

“…80 For example, rapid tests developed for detecting Anaplasma phagocytophilum and parvovirus were validated and reported for fishers ( Martes pennanti ) and gray foxes ( Urocyon cinereoargenteus ), respectively. 125 Additional examples can be found for M. bovis papers, including serologic assays for detection of M. bovis in wild ruminants, 76 and ELISA for detection of the organism in cattle and deer. 116 Another study addressed the use of multiple species to establish cutoff values for free-ranging bison and caribou when no reference samples were available and infection status of the tested animals was not known.…”