Detection of Anti‐BrucellaAntibodies in Llama (Lama glama)

Evaluation of three immunological assays to mitigate the risk of transboundary spread of Coxiella burnetii by alpacas

Coxiella burnetii causes coxiellosis in animals and Q fever in humans, a potentially debilitating zoonotic disease commonly transmitted through domestic ruminants. To prevent transboundary spread of C. burnetii, animals may be tested prior to export. In alpacas, this process is complicated by the lack of scientific evidence for C. burnetii infection in the species, and the unique composition of camelid antibodies, which may cause false-positive results in assays developed for ruminants. We evaluated a complement fixation test (CFT; currently recommended for alpacas in New Zealand), an enzyme-linked immunosorbent assay (ELISA) and an immunofluorescence assay (IFA). Positive analytical control samples were generated through vaccination of alpacas with a human Q fever vaccine, whereas negative analytical control samples were sourced from New Zealand (deemed free of C. burnetii). Immunological assays were conducted on 131 alpaca sera submitted for export testing. Test characteristics (sensitivity, specificity, positive and negative predictive values) for CFT, ELISA and IFA were determined using Bayesian latent class analysis. Due to anticomplementary activity, 37 (28.2%) of the CFT results were inconclusive, making CFT unsuitable for routine use. Of the remaining 94 samples, 10.6%, 0% and 7.4% were positive for C. burnetii antibodies based on CFT, ELISA and IFA, respectively, yielding estimated sensitivities of 58%, 26% and 78%, and estimated specificities of 95%, 98% and 95%, with the estimates for sensitivity being imprecise, as evidenced by wide 95% credible intervals. Positive predictive values were similar across assays, albeit very low at the estimated seroprevalence of 5%. Our results indicate that, of the tests available, IFA appears to be the most appropriate for use in alpacas. Higher sensitivity of antibody detection, use of antigen detection assays and availability of samples from individuals with evidence of infection could provide additional insight into the risk of transboundary spread of C. burnetii by alpacas.

Evaluation of up-converting phosphor technology-based lateral flow strips for rapid detection of Bacillus anthracis Spore, Brucella spp., and Yersinia pestis

Bacillus anthracis, Brucella spp., and Yersinia pestis are zoonotic pathogens and biowarfare- or bioterrorism-associated agents that must be detected rapidly on-site from various samples (e.g., viscera and powders). An up-converting phosphor technology-based lateral flow (UPT-LF) strip was developed as a point-of-care testing (POCT) to satisfy the requirements of first-level emergency response. We developed UPT-LF POCT to quantitatively detect the three pathogens within 15 min. Sample and operation-error tolerances of the assay were comprehensively evaluated. The sensitivity of UPT-LF assay to bacterial detection reached 10(4) cfu · mL(-1) (100 cfu/test), with a linear quantitative range of 4 to 6 orders of magnitude. Results revealed that the UPT-LF assay exhibited a high specificity with the absence of false-positive results even at 10(9) cfu · mL(-1) of non-specific bacterial contamination. The assay could tolerate samples with a wide pH range (2 to 12), high ion strengths (≥ 4 mol · L(-1) of NaCl), high viscosities (≤ 25 mg · mL(-1) of PEG20000 or ≥ 20% of glycerol), and high concentrations of bio-macromolecule (≤ 200 mg · mL(-1) of bovine serum albumin or ≥ 80 mg · mL(-1) of casein). The influence of various types of powders and viscera (fresh and decomposed) on the performance of UPT-LF assay was determined. The operational error of liquid measurement exhibited few effects on sensitivity and specificity. The developed UPT-LF POCT assay is applicable under field conditions with excellent tolerance to sample complexity and operational error.