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Role of Enhanced Detoxication in a Deltamethrin-resistant Population of Triatoma infestans (Hemiptera, Reduviidae) from Argentina
Ist Teil von
Memórias do Instituto Oswaldo Cruz, 2004-05, Vol.99 (3), p.335-339
Ort / Verlag
Brazil: Fundação Oswaldo Cruz, Fiocruz
Erscheinungsjahr
2004
Link zum Volltext
Quelle
Free E-Journal (出版社公開部分のみ)
Beschreibungen/Notizen
Deltamethrin and other pyrethroids have been extensively used in
Argentina since 1980, for the chemical control of Triatoma infestans
Klug (Hemiptera: Reduviidae). Recently, resistance to deltamethrin was
detected in field populations by the survival of bugs exposed by
topical application to the diagnostic dose estimated on the CIPEIN
susceptible strain. Results of the current study showed low resistant
ratios (RRs) to deltamethrin for the resistant populations (RR ranged
from 2.0 for San Luis colony to 7.9 for Salta colony). Biochemical
studies were made on the most resistant colony (Salta) and the
susceptible strain (CIPEIN), in order to establish the importance of
degradative mechanisms as a cause of the detected resistance. Esterase
activity was measured on 3 days old first instars through
phenyl-thioacetate and a-naphtyl acetate activities. The results showed
a significant difference in no cholinesterase esterase activity from
susceptible (7.6 ± 0,7 μM S./i.min.) and Salta resistant
colony (9.5 ± 0.8 μM S./i.min.). Cytochrome P450
mono-oxygenase (P450) activity was measured on individual insects
through ethoxycoumarine deethylase (ECOD) activity using a fluorescence
micro plate reader. The dependence of ECOD activity on age and body
region of the nymphs, and pH and time of incubation were studied in
order to optimize the measurement. As a result, comparative studies
were performed on abdomens of 2 days old first instars at pH 7.2 and 4
h incubation time. ECOD activity of first nymphs was significantly
lower in the susceptible colony (61.3 ± 9.08 pg ECOD/ insect) than
in the resistant one (108.1± 5.7 pg ECOD/ insect). These results
suggest that degradative esterases (no-cholinesterase) and
mono-oxygenases cytochrome P450, play an important role in the
resistance to deltamethrin in Salta colony from Argentina.