ABSTRACT
@#Malaria, a mosquito-borne disease, is caused by protozoa of the genus Plasmodium and constitutes a serious public health problem. Because current insecticides used to control malaria face resistance due to continuous use, new alternatives are prompted. Considering this context, and the insecticidal potential of vertebrate venoms/secretions, crude and methanolic extracts from two frog species were tested as larvicides against Anopheles darlingi. Skin secretions of Rhinella marina and Rhaebo guttatus were obtained by manual stimulation. Then, methanol was added to obtain steroidal fractions from both venoms. Mosquitos were captured in suburban areas of Porto Velho and An. darlingi females were later fed with blood and stimulated to oviposit. The larvae were fed with fish food until the 3rd and 4th instars. For the larvicidal assays, crude secretions and methanolic fractions of both frog species were evaluated, and larvae mortality was recorded after 48 hours. Crude extracts and steroidal fractions from both species had larvicidal effects, with an LC50 of 127.5 and 133 ppm for the crude extract and steroidal fraction of R. marina, and an LC50 of 37.5 and 35.8 ppm for the crude extract and steroidal secretion of R. guttatus, respectively. The present work reports for the first time the larvicidal effects of the skin secretions from bufonid species occurring in the western Amazon region. Further studies should be carried out to investigate the purified components responsible for the observed activity.
ABSTRACT
@#Toxic baits, widely used against insect pests, are being successfully used to control mosquito vectors. In the present study, basic aspects for Attractive Toxic Sugar Baits (ATSBs) use as a control tool against Aedes aegypti including insecticide dosage, bait composition and plant application under laboratory conditions were evaluated. The Lethal Concentrations (LC 50 and 90) of boric acid (insecticide) Ae. aegypti engorgement and mortality were determined using ATSBs prepared using fruits (guava, mango and cupuaçu) and offered to mosquitoes on cotton discs and also sprayed on a Kalanchoe blossfeldiana plant. LCs of Ae. aegypti males and females did not differ significantly and varied from 0.53 to 2.46%, decreasing from 24 to 48 hours. No significant difference in the proportion of engorged male mosquitoes in ATSB (0.60) and Attractive Sugar Bait (ASB) (0.65) was found, but females engorged more on ASB (control bait) (0.80) compared to ATSBs (0.67). General mortality rate of mosquitoes in ATSB and ASB were 0.81 and 0.10 for males, respectively; 0.61 and 0.12 for females, respectively. Fruit composition affected neither engorgement nor mortality. ATSB applied on plants caused the mortality of males and females ranging from 0.75-0.87 while mortality on ASB sprayed plants varied from 0.07-0.14. Different common fruit juices and a low toxic oral insecticide are readily accepted, engorged and causes a high mortality both males and females Ae. aegypti using ATSBs. Moreover, the use of a common indoor plant in the region sprayed with ATSB under laboratory conditions leads to significant mosquito mortality.