Where do infections in ticks come from? - briefly
Ticks acquire pathogens mainly by feeding on infected vertebrate hosts—rodents, birds, deer, and other mammals—while some microbes also transmit transovarially from adult females to their offspring. This combination of horizontal and vertical acquisition sustains infection cycles in tick populations.
Where do infections in ticks come from? - in detail
Ticks acquire microorganisms while feeding on infected vertebrate hosts. Pathogens enter the arthropod during blood meals from mammals, birds, or reptiles that harbor the agents in their bloodstream. After ingestion, microbes colonize the tick’s midgut, then migrate to salivary glands, enabling transmission to the next host.
Key reservoirs include:
- Small mammals (e.g., rodents, shrews) that maintain bacteria such as Borrelia burgdorferi and Anaplasma phagocytophilum.
- Larger ungulates (e.g., deer, elk) that support Babesia spp. and Anaplasma marginale.
- Ground‑dwelling birds that carry Rickettsia spp. and Borrelia genospecies.
- Reptiles and amphibians that can host Rickettsia and Ehrlichia variants.
Ticks also acquire viruses from infected hosts. For instance, Powassan and Tick-borne encephalitis viruses circulate in small mammals and birds, respectively. Some viruses persist transstadially, allowing the same tick to transmit the pathogen across its developmental stages.
Vertical transmission occurs when adult females embed pathogens into their eggs, producing infected larvae. This mechanism is documented for Rickettsia spp. and certain Borrelia genotypes. Horizontal transfer between co‑feeding ticks, without a systemic host infection, has been observed for Babesia and Rickettsia.
Environmental factors influence pathogen prevalence. Habitat fragmentation, host density, and climate-driven changes in tick activity periods affect the likelihood of acquisition. Warmer temperatures extend questing seasons, increasing contact opportunities between ticks and competent reservoirs.
In summary, microorganisms that cause disease in ticks originate from the blood of infected vertebrates, can be passed from mother to offspring, and may spread between ticks sharing a feeding site. Host diversity and ecological conditions determine the composition and intensity of these infections.