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PubMed1981

Relative toxicity of decamethrin, chlorphoxim and temephos (abate) to simulium larvae.

Tolerance levels Simulium larvae (S. ornatum and S. equinum) to chlorphoxim and decamethrin, relative to those with Abate, were determined in rapid through-flow laboratory test vessels; a 1-hour exposure followed by 24-hour mortality observations being the standard of comparison of the three chemicals. In addition, a further comparison between chlorphoxim and Abate was made on the basis of a 15-minute exposure in a miniature simulated stream, with the same mortality criteria. On the basis of LC95/1-hour data the results showed that decamethrin was approximately 4 times as lethal as chlorphoxim, and approximately 20 times more than Abate. On the basis of a 15-minute exposure, chlorphoxim was found to be even more toxic than Abate--approximately 10 times more--than with the 1-hour exposure--viz 5 times more. Concentration/mortality curves indicate that with both the organophosphorus larvicides there is a critical zone where mortality increases sharply with increase in concentration of toxinant. With decamethrin, there is a more uniform rate of increase in mortality with increasing concentration, these differences being illustrated by comparison at both LC50 and LC95 levels. These findings are discussed firstly, in relation to other laboratory test methods in use, and secondly with reference to the scarcity of comparable laboratory data for Simulium damnosum in the Onchosceriasis Control Programme (OCP) in the Volta River basin area of West Africa.

Animals↗
PubMed1982

Laboratory and field tests of temephos (AbateR) on mosquito larvae and non-target organisms in rice fields in Malaysia.

The toxic effects of Abate (temephos) on mosquito larvae and non-target organisms were studied in the rice-field and in the laboratory. In the laboratory tests, Culex tritaeniorhychus larvae and cladoceran zooplanktons (predominantly Diaphanosoma and Moinodaphnia species) were found to be highly susceptible to Abate with LC50 values of 0.27 and less than 0.10 parts per billion respectively. Other non-target species in decreasing degree of susceptibility to Abate were copepods (Tropodiaptomus spp.), Aplocheilus panchax and Tubifex worms. In field study, Abate at concentrations 60, 100 and 200 gm hectare-1 is effective in maintaining the rice-fields free of Anopheles and Culex mosquitoes for at least 2 days. No mortality was observed for Aplocheilus panchax and Tubifex worms at the above concentrations; nevertheless, populations of cladoceran zooplanktons and copepods were reduced up to seven days posttreatment.

Animals↗
PubMed1982

[Effect of temephos on the acetylcholinesterase activity of the brain of Tilapia guineensis. 1: Experimental study at operative doses].

After having exposed during 10 minutes the Tilapia guineensis to a concentration of 0,05 mg/l of temephos (concentration of a larvicide used for the field test), the authors note a lowering of the acetylcholinesterastic activity of the brain to an order of 25%. The return to a normal activity is achieved within 20 to 25 days. A new exposure, happening one week after the first, provokes a further lowering before the return to a normal value. The authors question themselves on the consequences of these chemical attacks repeated on a weekly basis during antilarval treatments in the struggle against the onchocercose.

Acetylcholinesterase↗
PubMed1982

[Effect of temephos on the acetylcholinesterase activity of the brain of Tilapia guineensis. 2: Experimental study of 24-hour exposure to the toxic compound].

The exposition of the Tilapia guineensis to concentrations used in the field to destroy the simulium larvae in their aquatic biotopes is 0,05 mg/l/10 minutes. The authors have previously remarked a significant lowering of acetylcholinesterasic brain activity in this fish. In the case of a much prolonged contact (24h corresponding 144 times the theoretic time of contact), it is noticed that, if this immediate effect is not more pronounced, on the other hand it is noticeable for a much longer acetylcholinesterasic activity extends beyond forty days. In the same conditions, three successive weekly treatments lead the acetylcholinesterasic activity to the level of vital activity.

Acetylcholinesterase↗
PubMed1983

[Effect of temephos on acetylcholinesterase activity in the brain of Tilapia guineensis. 3: Comparative effect of temephos and 3 substitute insecticides].

The Onchocerciasis Control Programme (OCP) is realized in the major part of the treated area by weekly applications of temephos in biotopes of simulles larvae. This insecticide is very effective and its impact on the aquatic fauna is evaluated by means of periodic samplings of the fauna. Therefore, the most sensitive way of tracking down fish poisoning is by studying the brain acetylcholinesterase depression. Evaluated on Tilapia guineensis this lowering is moderate when operational doses are used by OCP. The discovery of resistence to temephos incited researchers of OCP to try remplacement insecticides. Among these, chlorphoxim, chlorpyrifos-methyl and pirimiphos-methyl proved to be the most effect of these three organophosphorus compounds to that of temephos on the acetylcholinesterasic activity of the brain of Tilapia but using a much higher dosage (0,05 mg/l during 24 hrs that is 144 times more than for temephos). The results demonstrate that the three remplacement insecticides have on inhibitive effect plainly more important than that of temephos and that the retour to normal activity requires a much longer time.

Acetylcholinesterase↗
PubMed1976

Laboratory insecticide susceptibility tests against Mansonia larvae.

Insecticides Abate, DDT, Dowco-214, Dursban, fenitrothion, fenthion, gamma-HCH, and malathion were tested against the field collected fourth instars larvae of Mansonia from Penang Island, Malaysia. The larvae appeared to be highly susceptible to Dursban and Abate with LC50 values of 1.54 and 1.92 parts per billion respectively. Other chemicals, in decreasing degree of effectiveness, were gamma-HCH, fenthion, P,P'-DDT, Dowco-214, fenithrothion and malathion. The potential use of these chemicals in Mansonia control was discussed. A simple method for collecting and testing Mansonia larvae was also described.

Animals↗