How does a tick become infected? - briefly
Ticks acquire pathogens during a blood meal from an infected animal, allowing the microorganisms to move from the gut to the salivary glands for later transmission. Co‑feeding on the same host can also transfer infections between nearby ticks.
How does a tick become infected? - in detail
Ticks acquire pathogens primarily during the blood meal taken from an infected vertebrate host. The ingested pathogen enters the midgut, where it survives, multiplies, and eventually migrates to the salivary glands. When the tick attaches to a new host, the pathogen is transmitted through saliva.
Each developmental stage—larva, nymph, adult—feeds once before molting or reproducing. Infection can occur at any stage if the host carries the appropriate microorganism. The most common routes of acquisition include:
- Direct ingestion of infected blood while feeding.
- Co‑feeding transmission, where an uninfected tick acquires a pathogen from a nearby infected tick feeding on the same host, without systemic infection of the host.
- Transovarial passage, where infected female ticks transmit pathogens to their offspring through eggs.
After entry into the tick’s midgut, pathogens must cross the gut epithelium, survive immune defenses, and colonize the salivary glands. This process often involves specific surface proteins that facilitate attachment and migration. Once established in the salivary glands, the pathogen is ready for delivery during the next feeding event.
Several variables affect the likelihood of acquisition:
- Host competence: species that sustain high pathogen loads increase infection risk.
- Pathogen density in the host’s blood: greater concentrations raise the probability of successful ingestion.
- Tick species and genetics: some vectors possess innate susceptibility or resistance to particular microorganisms.
- Environmental temperature and humidity: favorable conditions accelerate pathogen replication within the tick.
- Microbiome composition: symbiotic bacteria can inhibit or promote pathogen colonization.
The infection cycle concludes when the tick, now carrying the pathogen in its salivary glands, attaches to a new host and injects the organism during feeding, perpetuating the transmission cycle.