RESUMO
Blood sucking parasites not only cause economic loss but also transmit numerous diseases. Dermanyssus gallinae, an obligatory blood feeding ectoparasite causes huge production loss to the poultry industry. Mosquitoes act as vector for transmitting several viral and parasitic diseases in humans. Acaricide resistance limits the control of these parasites. The present study was aimed to control the parasites using chitinase that have selective degradation of chitin, an important component in exoskeleton development. Chitinase was induced in Streptomyces mutabilis IMA8 with chitin extracted from Charybdis smithii. The enzyme showed more than 50% activity at 30-50 °C and the optimum activity at 45 °C. The enzyme activity of chitinase was highest at pH 7.0. The kinetic parameters Km and Vmax values of chitinase were determined by non-linear regression using Michaelis-Menten equation and its derivative Hanes-Wolf plot. The larvicidal effect of different concentrations of chitinase was evaluated against all instar larvae (I-IV) and pupae of An. stephensi and Ae. aegypti after 24 h of exposure. The percentage of mortality was directly proportional to the chitinase concentration. Bioassay for miticidal activity showed that chitinase had excellent miticidal activity (LC50 = 24.2 ppm) against D. gallinae. The present study suggested the usage of Streptomyces mutabilis for preparation of chitinase in mosquito and mite control.
