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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 89, Num. 2, 1994, pp. 251-252
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Mem. Inst. Oswaldo Cruz, Rio de Janeiro, Vol. 89(2):
251-252, apr./jun. 1994
RESEARCH NOTE
Susceptibility Status of Aedes taeniorhynchus to
Organochlorine and Organophosphate Insecticides
Domingo Montada, Rosa Tang, Agustin Navarro, Francisca A Garcia
Code Number: OC94052
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Instituto de Medicina Tropical "Pedro Kouri", Autopista Novia de
Mediodia, Km 6, e/ Autopista Nacional y Carretera Central, Apartado
601, Lisa, Ciudad de la Habana, Cuba
Key words: Aedes taeniorhynchus - susceptibility -
organochlorine - organophosphate
Aedes taeniorhynchus play an important role in the
transmission of Eastern Equine Encephalomyelitis (EEE), an important
medical- veterinary arbovirus. A Fernandez et al. (1973 Rev Cub
Hig Epid 19: 35-40) isolated EEE virus from Ae.
taeniorhynchus in Havana, incriminating it as a vector and
demonstrating its involvement in arbovirus transmission. Chemical
control strategies against Ae. taeniorhynchus are very
important to control vector populations and transmission of EEE.
However, it is first necessary to determine the susceptibility
status of vector population to various insecticides. Hence, we
reported data on this subject using organophosphorus (5) and
organochlorine (1) insecticides.
Larvae susceptibility tests in the laboratory followed the WHO
procedure (WHO/VBC 81.807) using stock solutions of malathion,
fenthion, fenitrothion, temephos, chlorpyrifos and DDT obtained from
WHO. Late-third or early-fourth instar of Ae. taeniorhynchus
larvae, collected in Rosario Beach, Guines, Habana Province were
used. Eight tests were done for each insecticide. Each test
consisted of four replicates each of six concentrations obtained by
serial dilutions from each solution. Water used in the tests was
obtained from inmature habitats and ranged from 10-12 mg/l salinity
(pH values ranged from 7.5 to 8.0 and were not significantly
different).
Tests were conducted with mosquito samples collected during the
rainy (May-October) and dry (November-April) seasons.
LC50 and LC90 values were calculated by probit analysis (M Raymond
1985 Cahiers ORSTOM 23: 117-121). Control mortality was
corrected using Abbott's formula (WS Abbott 1925 J Econ Entomol
18: 265-267). Replicates with larval mortality > 20% were
discarded and repeated. All tests were conducted under laboratory
conditions at 26 +/- 1 oC.
LC50 and LC90 values are shown in the Table. Ae taeniorhynchus
was more susceptible to chlorpyrifos than the other insecticides
tested. According to the WHO procedure, above mentioned, we found
the following discriminating doses to chlorpyrifos (0.008 mg/l); DDT
(0.02 mg/l); fenthion (0.02 mg/l); fenitrothion (0.04 mg/l);
malathion (1.0 mg/l) and temephos (0.008 mg/l). LC50 and LC90 values
reported here for fenthion and malathion insecticides are very
similar to those found by AH Boike et al. (1978 Mosq News 38:
210-217) using a susceptible strain from Florida, U.S.A.
Discriminating insecticide dosages for Ae. taeniorhynchus
obtained here, for the first time in Cuba, provide baseline data for
monitoring the development of resistance to those insecticides used
against this mosquito.
TABLE
Susceptibility of Aedes taeniorhynchus larvae to
organochlorine and organophosphate insecticides collected in Habana
Province, Cuba, 1991-1992
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Insecticides
95% Fiducial
limits for
LC 50 LC 90 LC 90
(mg/l) (mg/l) LCL UCL
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Chlorpiryfos 0.00043 0.00107 0.00093 0.00129
DDT 0.00172 0.00352 0.00318 0.00400
Fenthion 0.00131 0.00318 0.00281 0.00373
Fenitrothion 0.00149 0.00441 0.00377 0.00533
Malathion 0.02588 0.09535 0.08260 0.11366
Temephos 0.00068 0.00152 0.00136 0.00173
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Insecticides Regression
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Equation F F Chi^2
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Chlorpiryfos 5.16 + 3.2 lnX 12.90*** 9.37
DDT 5.33 + 4.1 InX 153.61*** 4.38
Fenthion 5.26 + 3.3 InX 11.52*** 5.84
Fenitrothion 5.22 + 2.7 InX 25.26*** 8.64
Malathion 5.63 + 2.2 InX 123.19*** 8.94
Temephos 5.12 + 3.6 InX 6.14** 5.44
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Copyright 1994 Fundacao Oswaldo Cruz - FIOCRUZ
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