Environmental effects on behavioral and physiological traits of the housefly Musca domestica in the transmission of pathogenic bacteria

This study was focused in the evaluation in the effects of temperature and relative humidity on behavioral and physiological characteristics of Musca domestica, as well as the role played by it on the mechanical transmission of pathogenic bacteria under controlled laboratory conditions. Adult houseflies caught in the urban area were reared in the laboratory and kept at different temperatures (20 ± 2 °C, 25 ± 2 °C, and 30 ± 2 °C) and relative humidity level (40 ± 5%, 60 ± 5% and 80 ± 5%) Behavioral parameters such as locomotor activity, frequency of flying, number of landings and duration of contact with surfaces were recorded while physiological indicators such as survival rate, general activity and visible stress responses were monitored on day-to-day basis. Samples from external body surface, mouthparts and digestive system were checked for the presence of the bacteria using the standard microbiological method and the results of the analyses were analyzed by means of univariate analysis of variance with a level of significance of P ≤ 0.05. The results showed that the behavioral activity increased with increasing temperature and moderate to high humidity when compared to rates of physiological stress and mortality which were higher under extreme environmental conditions. In addition, the percentage of bacteria positive samples improved significantly with the increase of the temperature and the humidity level, showing a positive correlation between the environmental condition, the fly activity and the potential of the mechanical transmission of pathogen bacteria, with all of the observed differences being statistically significant (P ≤ 0.05).