Short and long-term effects of azadirachtin A on development and egg production of Rhodnius prolixus

Abstract

Azadirachtin A was given through a blood meal to 4th-instar larvae and to adult females of Rhodnius prolixus. Development (ecdysis) and egg production were inhibited in a dose-dependent manner. Long-term experiments with subsequent four feedings on azadirachtin-free blood were performed with 4th-instar larvae and with adult females. Only in the low-dose azadirachtin larval groups (0.01 and 0.1 microgram/ml of blood), development was partially restored; after a single 1.0 microgram/ml treatment about 50% of the treated larvae were still alive 120 days later without any adult emergence. Similarly fed females had a dose-dependent lower survival and egg deposition rate. The results are discussed in relation to the mode of azadirachtin A action.

Impact of repeated NeemAzal®-treated blood meals on the fitness of Anopheles stephensi mosquitoes

“…In our study, the survival of mosquitoes appeared not to be affected by the repeated NeemAzal® administration even at the highest tested dosage (data not shown). This finding is in line with other azadirachtin studies that showed a moderate impact on insect longevity in repeated exposure schemes [ 33 , 46 ]. Azadirachtin exerts cytotoxic effects at high concentrations; however, in Rodnius prolixus and Locusta migratoria the compound was found to be rapidly metabolized and excreted in the form of dihydroazadirachtin although small amounts could be retrieved in the head and visceral tissues weeks after its application [ 52 , 53 ].…”

“…For comparison, in C. tarsalis and C. quinquefasciatus the oviposition rate and size of egg raft was found to be reduced when females were fed on sucrose solutions containing 10 ppm azadirachtin before blood feeding [ 33 ]. Studying the azadirachtin effects on the haematophagous vector of chagas desease Rhodnius prolixus , Garcia and colleagues (1990) observed a strong reduction of the number of eggs laid by females after administration of 1 and 5 μg/ml azadirachtin by membrane feeding [ 46 ]. By administering 3 consecutive plain blood meals after the treated one, the effect was found to be irreversible in the 5 μg/ml group and only partially reversible at 1 μg/ml.…”

“…By administering 3 consecutive plain blood meals after the treated one, the effect was found to be irreversible in the 5 μg/ml group and only partially reversible at 1 μg/ml. The authors hypothesized that small amounts of azadirachtin may stably bind to various insect organs including brain, prothoracic glands and ovaries and thus interfere with endocrine regulation [ 46 , 47 ]. An irreversible impact on vitellogenesis was also observed by Dhar and colleagues [ 48 ], studying the effects of long-term exposure to neem volatiles on An.…”

The effect of azadirachtin on fresh isolates of Trypanosoma cruzi in different species of triatomines

“…The azadirachtin dose that prevents molting is slightly dierent for dierent triatomine species (Garcia et al 1989a(Garcia et al , 1990, and other parameters, e.g., reproduction rate and mortality are also dose-dependently aected (Garcia et al 1990). Dose-dependent effects on T. cruzi have only been investigated in the system Dm28/R.…”

Rhodnius prolixus: effects of the neolignan burchellin on in vivo and in vitro diuresis

“…These eects are part of a disease syndrome that also includes retardation of larval development (Schaub 1992). This is also evident if the blood is supplemented with azadirachtin, a compound isolated from neem-tree seeds and used as an insecticide (summarized by Garcia et al 1990;Garcia and Azambuja 1991;Kollien and Schaub 1999). Also, more widely distributed compounds of plants, lignans and neolignans (Gottlieb andYoshida 1989, 1990;Gottlieb 1991), strongly deter feeding and inhibit the molting of dierent insects (Harmatha and Nawrot 1984;MacRae and Towers 1984;Miyazawa et al 1994).…”