What should be tested in a tick for encephalitis? - briefly
Testing should include detection of tick‑borne encephalitis virus by PCR or serology (IgM/IgG). Screening for co‑circulating agents such as Borrelia burgdorferi, Anaplasma phagocytophilum, and Rickettsia species is also recommended.
What should be tested in a tick for encephalitis? - in detail
When a tick is collected for investigation of potential encephalitic agents, the laboratory workflow should address viral, bacterial and, where relevant, protozoan pathogens known to cause central‑nervous‑system infection.
The primary target is the tick‑borne encephalitis virus (TBEV) and its genetic variants. Detection strategies include:
- Quantitative reverse‑transcription PCR (qRT‑PCR) on homogenized tick material, providing rapid confirmation of viral RNA.
- Nested RT‑PCR for low‑copy‑number samples, increasing sensitivity for pooled specimens.
- Virus isolation in cell culture (e.g., Vero or BHK‑21 cells) when viable virus is required for further phenotypic analysis.
- Immunofluorescence assay using TBEV‑specific monoclonal antibodies to visualize viral antigens in tick sections.
Co‑circulating flaviviruses that may produce encephalitis should also be screened. Multiplex RT‑PCR panels can simultaneously identify Powassan virus, Louping‑ill virus and other related agents. Sequencing of amplified products, preferably by next‑generation sequencing, confirms species and genotype.
Bacterial agents capable of neuroinvasion merit inclusion in the testing scheme:
- PCR targeting Borrelia burgdorferi sensu lato complex, with primers for the flagellin (flaB) gene, to detect Lyme‑disease spirochetes.
- Real‑time PCR for Anaplasma phagocytophilum and Ehrlichia species, which can produce meningoencephalitis in rare cases.
- Conventional PCR for Rickettsia spp., followed by sequencing of the ompA or gltA genes for species identification.
Serological approaches, although less common for tick extracts, can complement molecular data. Enzyme‑linked immunosorbent assays (ELISA) detecting IgM or IgG against TBEV antigens may be applied to tick homogenates when viral load is insufficient for nucleic‑acid detection.
Quality control measures include:
- Processing negative extraction controls to monitor contamination.
- Using positive control RNA/DNA for each target pathogen to validate assay performance.
- Implementing internal amplification controls to detect PCR inhibition caused by tick tissue inhibitors.
Reporting should specify the pathogen detected, the method employed, and the quantitative result (e.g., cycle threshold values for qRT‑PCR). When multiple agents are present, each should be listed separately to inform clinical risk assessment and public‑health interventions.