"Heat" - what is it, definition of the term
The term «heat» refers to the transfer of energy that occurs when a system at a higher temperature comes into thermal contact with a system at a lower temperature, resulting in an increase of internal energy in the latter; this process proceeds spontaneously, follows the second law of thermodynamics, and can be quantified by calorimetric measurements, with the amount of transferred energy expressed in joules and related to temperature change through specific heat capacity.
Detailed information
Thermal energy significantly influences the physiology and ecology of ectoparasites such as ticks, insects, lice, and fleas. Elevated temperature accelerates metabolic rates, shortening developmental periods for eggs, larvae, and nymphs. In ticks, a rise of several degrees Celsius reduces the duration of the engorgement stage, leading to faster progression to the next life phase. For insects, increased warmth enhances feeding activity and host‑seeking behavior, thereby raising infestation risk.
Temperature gradients affect geographic distribution. Species with higher thermal tolerance expand into regions experiencing warmer climates, while those adapted to cooler conditions retreat or experience population decline. Seasonal temperature peaks often correspond with peaks in host‑parasite contact, as hosts become more active and ectoparasites increase questing or crawling activity.
Control strategies exploit thermal sensitivity:
- Exposure to temperatures above species‑specific lethal thresholds (e.g., 50 °C for many flea larvae) results in rapid mortality.
- Cold treatments (e.g., −20 °C for 24 hours) can incapacitate eggs of certain lice species.
- Heat‑based decontamination of bedding, clothing, and equipment eliminates dormant stages without chemical residues.
- Environmental management that reduces ambient temperature, such as ventilation and shading, limits reproductive rates.
Understanding the relationship between temperature dynamics and ectoparasite biology enables targeted interventions, improves predictive modeling of outbreak patterns, and supports integrated pest management programs.