Effects of ivermectin on Culex quinquefasciatus larvae

Abstract

The effects of ivermectin, a semi-synthetic drug widely used for treatment of livestock parasite diseases, were observed on Culex quinquefasciatus larvae. Toxic effects and mortality evaluation were carried out after 5, 15, 30 and 60 minutes of exposure to 1, 5 or 10 ppm of ivermectin solutions. Observations were made 24 and 48 hours after the beginning of the experiment, and loss of mobility, progressive paralysis and high mortality of larvae were recorded. The observed effects of ivermectin on the mosquito larvae is probably correlated with chloride channel activation on cell membranes.

Effect of ivermectin on the life cycle and larval fat body of Culex quinquefasciatus

“…However, action of the ivermectin may be associated with neurotransmitter release in conjunction with the GABA antagonist, probably contributing for excitatory signals of poisoning (Turner and Schaeffer, 1989;Bloomquist, 1996). In the present study, the majority of the larvae of C. quinquefasciatus exposed to the 1.5 ppb solution of ivermectin presented ataxia, followed by death, suggesting binding of this insecticide to the GABA with consequent lethal action for C. quinquefasciatus, which agreeed with results obtained by Freitas et al (1996). Therefore, the ivermectin may be acting in the hyperpolarization of the fat body cell membranes inhibiting lipid, carbohydrate and/or protein uptake making with that these cytoplasmic inclusions became minors.…”

“…However, in the ivermectin exposed larvae, F 1 generation shortened about 1 day its development from egg to adult, suggesting that the ivermectin exposure of parental generation may cause a rapid development to avoid the environment stress. Ivermectin caused paralysis in Culex quinquefasciatus larvae, as observed by Freitas et al (1996) which could be results of the activation of chlorine canals as suggested by Bloomquist (1996). Ivermectin binds to GABA, which increase the possibility of the GABAa in activating chloride canals of postsynaptic membranes.…”

“…Previous studies have shown that the avermectins are lethal for immature and adult stages of some insect orders (Strong and Brown, 1987) and efficient for the control of Culex quinquefasciatus (Freitas et al, 1996). It is not necessary its ingestion, because the contact with the same already is effective in the majority of the cases (Strong, 1993).…”

Susceptibility of Aedes aegypti (Linnaeus) (Diptera: Culicidae) Immature Forms to Ivermectin

“…However, action of the ivermectin may be associated with neurotransmitter release in conjunction with the GABA antagonist, probably contributing for excitatory signals of poisoning (Alves et al 2004). In the present study, the majority of the larvae of A. aegypti exposed to concentrations of 1, 5 and 10 ppm of ivermectin solution presented ataxia, followed by death, suggesting binding of this insecticide to the GABA with consequent lethal action for A. aegypti, which agreed with results obtained by Freitas et al (1996) and Alves et al (2004) for Cx. quinquefasiatus.…”

“…Also, several studies have recently reported a decrease in the persistence of temephos, the main larvicide used to control A. aegypti in Brazil, suggesting that mosquito populations have developed resistance to this organophosphate in several states (Carvalho et al 2004) Ivermectin is a group of macrocyclical lactones, derived from 22,23-dihydro avermectin B1, with low water solubility that is produced by Streptomyces avermitilis, being largely used as anti-parasitic in the domestic animals (Benz et al 1989). Previous studies have shown that the avermectins are lethal for immature and adult stages of some insect orders and highly efficient for the control of larvae of Aedes, Anopheles and Culex (Freitas et al 1996, Alves et al 2004 when exposed to low concentrations of ivermectin. It is not necessary its ingestion, because the contact with the same is effective in the majority of the cases (Strong 1993).…”