Unexpected failures to control Chagas disease vectors with pyrethroid spraying in Northern Argentina
Date
2012-08
Journal Title
Journal ISSN
Volume Title
Publisher
Entomological Society of America
Abstract
Effectiveness of the elimination efforts against Triatoma infestans (Klug) in South
America through residual application of pyrethroid insecticides has been highly variable in the Gran
Chaco region. We investigated apparent vector control failures after a standard community-wide
spraying with deltamethrin SC in a rural area of northeastern Argentina encompassing 353 houses.
Insecticide spraying reduced house infestation less than expected: from 49.5% at baseline to 12.3 and
6.7% at 4 and 8mo postspraying, respectively. Persistent infestations were detected in 28.4% of houses,
and numerous colonies with late-stage bugs were recorded after the interventions. Laboratory
bioassays showed reduced susceptibility to pyrethroids in the local bug populations. Eleven of 14 bug
populations showed reduced mortality in diagnostic dose assays (range, 35 5% to 97 8%) whereas
the remainder had 100% mortality. A fully enclosed residual bug population in a large chicken coop
survived four pyrethroid sprays, including two double-dose applications, and was Þnally suppressed
with malathion. The estimated resistance ratio of this bug population was 7.17 (range, 4.47Ð11.50). Our
Þeld data combined with laboratory bioassays and a residual foci experiment demonstrate that the
initial failure to suppress T. infestans was mainly because of the unexpected occurrence of reduced
susceptibility to deltamethrin in an area last treated with pyrethroid insecticides 12 yr earlier. Our
results underline the need for close monitoring of the impact of insecticide spraying to provide early
warning of possible problems because of enhanced resistance or tolerance and determine appropriate
responses.
Description
item.page.type
Journal Article (peer-reviewed)
item.page.format
Keywords
TRIATOMA INFESTANS, CHAGAS DISEASE, VECTOR CONTROL, REINFESTATION, PYRETHROID RESISTANCE, VECTOR-BORNE DISEASES, PYRETHROID INSECTICIDES, INSECTICIDE RESISTANCE, INFESTATION
Citation
Gurevitz, J.M., Gaspe, M.S., Enríquez, G.F., Vassena, C.V., Alvarado-Otegui, J.A., Provecho, Y.M., et. al. (2012). Unexpected Failures to Control Chagas Disease Vectors With Pyrethroid Spraying in Northern Argentina. Journal of Medical Entomology, 49(6), 1379-1386.doi:http://dx.doi.org/10.1603/ME11157