How are ticks examined for infections? - briefly
Ticks are collected, surface‑sterilized, homogenized, and their nucleic acids extracted for multiplex PCR screening of bacterial, viral and protozoan pathogens; positive detections are confirmed by sequencing or, when possible, culture. This workflow provides rapid, sensitive identification of infection agents within the arthropod vector.
How are ticks examined for infections? - in detail
Ticks collected from the environment or hosts are processed through a series of laboratory steps designed to detect bacterial, viral, and protozoan agents. The workflow begins with species identification based on morphological keys or molecular barcoding, ensuring that pathogen prevalence can be linked to specific tick taxa. Specimens are then surface‑sterilized, usually with ethanol and sterile water, to remove external contaminants before homogenization.
The homogenate is subjected to nucleic‑acid extraction using silica‑column kits or magnetic‑bead protocols, yielding DNA and RNA suitable for downstream assays. Quantitative PCR (qPCR) or real‑time PCR panels target conserved gene regions of common tick‑borne pathogens such as Borrelia burgdorferi, Anaplasma phagocytophilum, Rickettsia spp., and Babesia spp. Multiplex formats allow simultaneous detection of several agents in a single reaction, increasing throughput and reducing reagent consumption.
For viruses, reverse‑transcription PCR (RT‑PCR) converts RNA to cDNA before amplification. In cases where pathogen load is low, nested PCR or digital droplet PCR provides enhanced sensitivity. Positive amplifications are confirmed by sequencing the amplicon, comparing it to reference databases to verify species‑level identification.
When viable organisms are required, tick homogenates are inoculated onto cell cultures (e.g., Vero or tick‑derived lines) or onto selective agar plates for bacterial isolation. Cultured isolates undergo phenotypic testing and whole‑genome sequencing to characterize antimicrobial resistance and virulence factors.
Serological methods, such as enzyme‑linked immunosorbent assays (ELISA) and immunofluorescence assays (IFA), detect pathogen antigens or antibodies in tick extracts, offering an alternative to nucleic‑acid techniques, especially for spirochetes and protozoa that may be difficult to amplify.
Quality control includes the use of negative extraction blanks, positive control strains, and internal amplification controls to monitor inhibition. Data are recorded in a laboratory information management system, linking each tick’s metadata (location, host, developmental stage) to the pathogen results, facilitating epidemiological analysis.
Key procedural steps
- Morphological or molecular tick species identification
- Surface sterilization and homogenization
- DNA/RNA extraction with validated kits
- Pathogen‑specific qPCR/RT‑PCR or multiplex panels
- Amplicon sequencing for confirmation
- Culture of viable agents when required
- Serological assays for antigen/antibody detection
- Implementation of rigorous quality‑control measures
This comprehensive approach yields reliable detection of infectious agents carried by ticks, supporting public‑health surveillance and risk assessment.