Question

Please answer questions in short answer or paragraphs. Write enough to provide clarity and answer each questions thoroughly in the sake of brevity.
How do seasons influence tick development? How does this seasonality influence the timing of disease transmission?

Answer 1

Ticks are ectoparasites (parasites that live outside the host). They feed on blood of animals. They act as vector for several pathogens. African tick-bite fever, rickettsialpox, lyme diseases, tick paralysis etc. are some of the diseases transmitted by ticks.

Seasonal changes are critical for tick distribution and density. It also increases the risk of transmission of tick-borne pathogens to human beings. Ticks are found around the world, especially in warm and humid climates.

In the present warmer world, tick population is booming. They are now able to survive in more places than earlier increasing the risk of tick-related diseases. Rising global temperatures and increased rainfall accelerates life cycle of ticks. Ticks require humid climate to stay hydrated, hence relative humidity needs to be 80% or above for them to survive. This high humidity enables them to absorb moisture from the air and stay hydrated. Moreover, low temperatures (below 44 degree Fahrenheit) make it difficult for the ticks to survive. Warmer temperature allows them to move around easily and find its potential hosts.

Hence, ticks are sensitive to climate changes. Warmer winters, extended autumn, summer, and spring seasons have been found to increase the distribution and density of several tick species. Studies have shown that from 1973 to 2003, incidence of tick-borne diseases like Lyme Borreliosis, tick-borne encephalitis, etc. has increased by 400 percent owing to increased global temperature.

The risk of tick borne diseases is related to the density of active infected ticks, which is in turn related to climate change, host community, and distribution of vegetation. Temperature, in particular, can impact the dynamics of tick-borne infection. They alter the contact pattern and pathogen transmission amongst the ticks and their hosts.

Seasonality has strong influence on tick density. Higher tick abundance is seen during spring-summer seasons (tick seasons). Adult ticks are found to be more active and plentiful during these seasons. Adult females lay eggs which also hatches at this time and are able to find their host very easily. Hence, tick attachment and disease transmission is more during these seasons.