TBE serodiagnosis in sentinel dogs – improving TBE surveillance in risk areas and health care for service dogs (Poster abstract)

Philipp Girl^{a, b}, Maja Haut^c, Sandra Riederer^{c, d}, Martin Pfeffer^c, Roman Wölfel^{a, b}, Gerhard Dobler^{a, b}

^a Bundeswehr Institute of Microbiology, Munich, Germany

^bGerman Centre for Infection Research (DZIF), partner site Munich, Germany

^c Institute of Animal Hygiene and Veterinary Public Health, Faculty of Veterinary Medicine, University of Leipzig, Germany

^d Veterinarian Dr. Christian Cronenberg, Wenzenbach, Germany

Introduction

Tick-borne encephalitis (TBE) virus is an emerging pathogen that causes severe infections in humans. It is endemic in large parts of Europe and Asia and is the most important vector-borne viral infection in Europe, with approximately 10,000–12,000 human cases per year. TBE risk areas are still defined based on the frequency of human cases. However, increasing vaccination rates lead to a decrease in clinical TBE cases in humans, thus complicating risk assessment.

To assess the true risk of infection, examination of sentinel animals such as dogs can help. This requires serological assays that reliably and specifically detect antibodies against TBE in dogs. However, studies on sensitivity and specificity in the detection of TBE antibodies in dogs are completely lacking. In our study, we investigated antibody prevalence in a dog population from a known TBE endemic area in south-eastern Germany, comparing the suitability of the three most commonly used antibody detection methods – neutralization test [NT], enzyme-linked immunosorbent assay [ELISA] and immunofluorescence assay [IIFA] - for epidemiological investigation in dogs.

Figure 2: Positive antibody detection in an indirect immunofluorescence assay: Cytoplasm shows TBE-typical fluorescence

Figure 3: Completed neutralization test: The blue stained wells (positive results) show an intact cell lawn indicating that all viruses are neutralized by the serum antibodies. In the unstained wells (negative results) not all viruses could be neutralized, the cell lawn was destroyed by virus growth.

Figure 4: Distribution of (A) Vienna units (VIEU)/mL determined by ELISA within negative and positive neutralization test (NT) results and (B) of NT-titers within negative and positive IIFA results. The significantly poorer sensitivity of ELISA and IIFA compared to NT is clearly evident from the false negative results (red and green bubble, respectively).

Materials and Methods

A total of 208 dog serum samples were included in the study, taken in a veterinary practice for pets between 2018 and 2019. All sera were tested in an all-species ELISA (PROGEN Biotechnik GmbH, Heidelberg, Germany) and an IIFA (Euroimmun AG, Lübeck, Germany) according to the manufacturer’s instructions. Sensitivity and specificity were determined for both assays compared to results from an in-house micro-neutralization assay.

Results

Of all 208 samples, 22 % were tested positive in the micro-NT. A total of 8.3 % of the samples showed characteristic fluorescence in the IIFA and were, thus, judged positive. In comparison to the micro-NT, the accepted gold standard test, a sensitivity of 78.3 % and a specificity of 98.8 % were obtained. In the ELISA, 9.2 % of samples were tested positive, with a sensitivity of 84.8 % and a specificity of 99.4 %.

Conclusions

The ELISA is a highly sensitive test for TBE-antibody detection in dogs and should be well suited for acute diagnostics. However, due to the detected deficits in sensitivity in dog samples, it cannot replace the NT, at least for epidemiological studies. With even lower specificity and sensitivity, the same applies to IIFA.

For the authors

Major (VC) Dr. Philipp Girl

Bundeswehr Institute for Microbiology, Munich, Germany

E-Mail: philippgirl@bundeswehr.org

Poster presented at the 52. Annual Conference of the German Association for Military Medicine and Military Pharmacy on October 15. 20121, in Coblenz, Germany