Factors Driving Paederus Outbreaks In Human Settings: Climatic Factor Or Human Intervention?
  Key Words  
  Dermatitis linearis, rove beetle, insecticide resistance, habitat disturbance
  Kok-Boon Neoh and Lee-Jin Bong
  Dermatitis linearis is skin irritation resulting from contact with the hemolymph of rove beetles from the genus Paederus. Paederus neither bite nor sting, but accidental crushing on human skin causing the release of the toxin paederin. Massive outbreaks are frequently reported in tropical regions of Asia and sporadic cases are documented elsewhere in temperate countries. It was hypothesized that climate factors have been the major determinant causing the massive dispersal to human settings as most outbreaks coincided with warmer summer months. In the present study, a year-long weekly sampling was conducted at infestation-prone human settings in Malaysia. The correlation between the numbers of rove beetle capture and climatic factors as well as the crop cycle activity was tested using Principal Component Analysis. The dispersal activity of P. fuscipes showed two peaks, which was from February to March and August to October. However, the result rejected the null hypothesis. Habitat disturbance and site unsuitability due to human intervention have been the main factors. In particular, massive dispersal of rove beetle was frequently observed during rice harvesting, including straw burning, and cultivation. The activity may disrupt the habitat, normal activities and reduce its prey. This activity could have rendered the rice fields unfavorable refuges and driven the rove beetles away to human settings. In addition, the management challenges such as the development of insecticide resistance owing to widespread use of insecticide in agricultural field is also discussed in this paper.