INVESTIGADORES
TOLOZA Ariel Ceferino
congresos y reuniones científicas
Título:
Is there any alternative insecticide to control pyrethroid-resistant Triatoma infestans populations (Hemiptera: Reduviidae) in the Gran Chaco Ecoregion?
Autor/es:
CARVAJAL GUILLERMO; MARIA INE S PICOLLO; A. C. TOLOZA
Reunión:
Congreso; ESA 61ST ANNUAL MEETING; 2013
Institución organizadora:
ESA
Resumen:
The kissing bug Triatoma infestans (Klug) is the main vector of Chagas disease,
which is a public health concern in most Latin American countries, where 10
million people are infected and over 90 million people are at risk of
infection. The prevention of Chagas
disease is mainly based on the chemical control of the vector using pyrethroid
insecticides. In the last decade, high resistance levels to these insecticides have
been detected in the geographic ecoregion of the Gran Chaco. Actually, the
alternative insecticides to control pyrethroid populations are based in the use
of organophosphate compounds. Thus, there is a need in the finding of new synthetic
insecticides against T. infestans resistant populations.
The aims
of the present study were: a) to analyze the toxicity of eight non-pyrethorid insecticides
against two T. infestans populations, a susceptible (S) and a deltamethrin-resistant (R) population
with a resistant level (RL) of 1031, b) to evaluate the delayed toxicity and the
influence of the nutritional state, and c) to test the effectiveness of
different commercial formulations (emulsifiable concentrate (EC) 35%, wettable
granule (WG) 70%, and 10% pour-on) against T.infestans.
Topical
application of the insecticides amitraz, flubendiamide, ivermectin, indoxacarb
and spinosad showed no insecticidal activity (lethal dose 50% (LD50) > 200 ng/insect). Nevertheless,
imidacloprid had lethal effect on both populations (LD50 values of
5.2 and 9.2 ng/insect). Based on these data, imidacloprid may be considered as
an alternative to non-pyrethroid insecticide for the control of pyrethroid-resistant
populations.
There was no significant variation
in the LD50s after 24, 48 and 72 h of initial topical application on
both S (LD50=5.2 ng/insect) and R (LD50= 9.2 ng/insect) populations.
This could indicate that the toxicological effect of the active ingredient
remains stable through the time. The nutritional condition (starvation/feeding)
of the insects had no significant influence on the insecticidal activity of the
imidacloprid on either populations S (LD50starved= 5.2 ng/i and LD50feeded=3.9 ng/i)
or R (LD50starved= 9.2
ng/I and LD50feeded=10.8 ng/i). Thus, the rate of penetration
associated with physicochemical modifications of cuticle after feeding seems
not to alter the relatively fast-acting effect after topical application.
Concerning commercial
formulations of imidacloprid, EC and WP were ineffective on glass surface LC50 >1g/m2,
while the pour-on formulation applied at the recommended dose of the 0.1µl/g to
pigeons showed a high effect of 100% mortality against T.infestans. The above results indicate that the neonicotinoid
imidacloprid seems to be a possible alternative to pyrethroid insecticides in
areas of Gran Chaco where T. infestans
developed resistance. However, the adequate formulation of the active
ingredient is essential in their effectiveness. Finally, the implementation of
an integrative control strategy is also discussed.