Elimite
[Laboratory evaluation of alpha-cypermethrin insecticide efficacy on Anopheles gambiae populations of Cote d'Ivoire resistant to permethrin and deltamethrin]

[Article in French]

Koffi AA, Darriet F, N'Guessan R, Doannio JM, Carnevale P.

Institut Pierre Richet (OCCGE), Bouake, Cote d'Ivoire.

Susceptibility tests were carried out in laboratory conditions to evaluate the efficacy of alpha-cypermethrin (a synthetic pyrethroid never used in Cote d'Ivoire) for malaria vector control. Five wild populations of Anopheles gambiae originating from M'be, Yaokoffikro, Korhogo, Kafine and Daola and two laboratory reared strains (Kisumu susceptible and Kou permethrin resistant selected strain) were tested. The diagnostic dosage of alpha-cypermethrin for the sensitive strain Kisumu was 2.5 x 10(-3)%. A comparative study of the susceptibility of samples of wild populations of An. gambiae was carried out according to the WHO standard susceptibility test. Impregnated papers with 4% DDT, 0.25% permethrin, 0.025% deltamethrin and 0.0025% alpha-cypermethrin were used. The results showed that except for mosquitoes from M'be, all the other populations were resistant to these insecticides. Bioassays were carried out with alpha-cypermethrin at the operational dosage of 20 mg a.i./m2 on the same population and laboratory reared strains. The results showed the efficacy of this insecticide on both the Kisumu strain and the population from M'be, a maintained efficacy for the Daloa, Kafine and Korhogo mosquito populations, but the wild anopheline population from Yaokoffikro clearly appeared fully resistant.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10214526&dopt=Abstract permethrin Elimite



Elimite
[Impact of resistance of Anopheles gambiae s.s. to permethrin and deltamethrin on the efficacy of impregnated mosquito nets]

[Article in French]

Darriet F, Guillet P, N'Guessan R, Doannio JM, Koffi A, Konan LY, Carnevale P.

l'Unite de Recherche et de Lutte contre le Paludisme, l'Institut Pierre Richet, OCCGE, Bouake, Cote d'Ivoire. darriet bouake.orstom.ci

Trials to assess the impact of resistance of Anopheles gambiae s.s. to permethrin and deltamethrin on the efficacy of insecticide-treated bednets were carried out from October 1997 to April 1998 in six experimental huts at the Yaokoffikro testing station in Cote d'Ivoire. Six polyester bednets were used. Two bednets were treated with permethrin at a dose of 500 mg/m2 and two with deltamethrin at 25 mg/m2. The remaining two untreated bednets served as controls. The number of Anopheles gambiae s.s. entering the hut was reduced 18% with permethrin-treated bednets and 43% with deltamethrin-treated bednets. Threefold fewer female mosquitoes were found under insecticide-treated bednets than under untreated nets (controls). The number of mosquitoes passing through the treated net was threefold lower. The number of mosquitoes exiting from the treated bednets increased twofold. The blood-feeding rate dropped by 55%. Forty percent of mosquitoes entering the permethrin-treated bednets and 56% entering the deltamethrin-treated bednets died. Immediate mortality was always greater (> 85%) than delayed mortality (< 15%). Bioassays confirmed the results from hut experiments. A lower knockdown effect was recorded with permethrin in the resistant strain. Conversely deltamethrin showed the same knockdown effects in the susceptible (Kisumu) and resistant (Yaokoffikro) strain. Mortality rates were low with both permethrin and deltamethrin. This study shows that, even in areas where Anopheles gambiae s.s. is resistant to permethrin and deltamethrin, bednets treated with these insecticides remain effective and can still be considered as an excellent method of personal protection.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10399691&dopt=Abstract permethrin Elimite



Elimite
Effects of synthetic pyrethroids and methidation on activities of some digestive enzymes in carp (Cyprinus carpio L.).

Simon LM, Laszlo K, Kotorman M, Vertesi A, Bagi K, Nemcsok J.

Department of Biochemistry, Jozsef Attila University, Szeged, Hungary.

The effects of pyrethroid pesticides (deltamethrin, permethrin and cypermethrin) and an organophosphate ester (methidation) on the activities of carp trypsin, alpha-chymotrypsin, carboxypeptidase A and lipase were studied. The enzymes were isolated from the gastrointestinal tract and the effects of the pesticides were investigated during incubation for 5 min. The activity of trypsin was influenced only slightly by the presence of deltamethrin and methidation, whereas permethrin and cypermethrin caused significant inhibition. The pyrethroid pesticides at lower concentrations resulted in a slight activation of alpha-chymotrypsin. Methidation inhibited the alpha-chymotrypsin activity by about 20%. These pesticides modified the lipase activity to a lesser extent; the highest inhibition was measured with cypermethrin. The carboxypeptidase A activity was inhibited by both pyrethroid pesticides and methidation. The results suggest that these pesticides might interact with the active conformation of the studied hydrolytic enzymes, resulting in changes in their activities.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10466103&dopt=Abstract permethrin Elimite



Elimite
Allozyme polymorphism and variability in permethrin tolerance in British populations of the parthenogenetic stored product pest Liposcelis bostrychophila (Liposcelididae, Psocoptera).

Ali N, Turner B.

Division of Life Sciences, King's College London, SE1 8WA, London, UK

Variability in allozyme patterns is demonstrated among 111 British populations of Liposcelis bostrychophila (Badonnel), an obligatory parthenogenetic liposcelid species that is a common domestic pest in the United Kingdom. In addition four tropical strains and a laboratory culture were included in the analysis. Permethrin toxicity was measured in a subset of the populations.Using cellulose acetate paper electrophoresis, 16 of 34 enzymes tested were found in the liposcelid material and, of these, four were polymorphic. A total of 47 distinct morphs were recognised. This enzyme variation appears to be random with respect to geography throughout the country.Permethrin tolerance was highly variable among populations. A significant relationship was demonstrated between the mean LC(50) for permethrin and latitude such that there appears to be higher levels of tolerance in southern, than in northern, Britain.No link could be established between the allozyme polymorphisms, particularly in the esterases, and permethrin tolerance.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11124375&dopt=Abstract permethrin Elimite



Elimite
Impact of pyrethroid-impregnated curtains on Phlebotomus papatasi sandflies indoors at Khartoum, Sudan.

Elnaiem DA, Aboud MA, El Mubarek SG, Hassan HK, Ward RD.

Department of Zoology, University of Khartoum, Sudan. dialnaiem hotmail.com

Laboratory and field investigations were made in an endemic focus of cutaneous leishmaniasis in Khartoum State, Sudan, to evaluate the effects of permethrin-impregnated curtains on the human-biting activity, nocturnal activity and resting behaviour of the vector sandfly Phlebotomus papatasi (Diptera: Psychodidae) indoors. Laboratory bioassays showed that curtains impregnated with 0.5, 1.0 or 1.5 g/m2 permethrin all gave 100% mortality within 24h of exposure of P. papatasi for 3 min. Under natural field conditions, the biting activity indoors and the resting density of P. papatasi were significantly reduced (P<0.001 and P=0.036, respectively) in rooms provided with permethrin-impregnated curtains as compared to control rooms left without curtains or fitted with unimpregnated curtains. No significant difference was found between the numbers of nocturnally active P. papatasi collected in rooms provided with impregnated curtains and rooms left without curtains or provided with unimpregnated curtains (P=0.377). Evidently P. papatasi was not repelled by these doses of permethrin on curtains, but the survival rate of sandflies collected from test rooms provided with permethrin-impregnated curtains was significantly reduced (P=0.036). We conclude that use of permethrin-impregnated curtains may provide a good control method for P. papatasi and other endophilic and/or endophagic sandfly vectors of leishmaniasis.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10484165&dopt=Abstract permethrin Elimite