cyhalothrin and Ectoparasitic-Infestations

Infestations of the bed bug, Cimex lectularius L. (Heteroptera: Cimicidae), are increasing around the world at an alarming rate and have become a major public health concern. The evolution of insecticide resistance could be a primary factor in explaining this resurgence. Extremely high levels of resistance to two pyrethroid insecticides, deltamethrin and lambda-cyhalothrin, relative to a susceptible colony, were detected in populations collected from human dwellings in Kentucky and Ohio. Offspring of a cross between a resistant and susceptible colony had intermediate susceptibility. Evaluations of populations from across the United States indicate that resistance to pyrethroid insecticides is already widespread. Without the development of new tactics for bed bug management, further escalation of this public health problem should be expected.

Topics: Animals; Bedbugs; Ectoparasitic Infestations; Insect Control; Insecticide Resistance; Insecticides; Lethal Dose 50; Nitriles; Nymph; Pyrethrins; United States

A field study was conducted from 1991 through 1997 to evaluate the use of pyrethroid and organophosphate (OP) ear tags, alternated yearly, for the control of a pyrethroid resistant horn fly, Haematobia irritans (L.), population in Louisiana. Fly resistance was monitored by weekly fly counts, filter paper bioassays and diagnostic polymerase chain reaction (PCR) assays for the presence of pyrethroid resistance-associated mutations in the sodium channel gene coding region. Fly control in the first study year was poor, as pyrethroid ear tags were effective for only 7 wk. The following year, OP ear tags provided 15 wk of fly control. However, in all subsequent years, fly control was poor with both types of ear tags. The PCR assays showed that there were very few female flies homozygous for the pyrethroid susceptible sodium channel allele, never rising above 10% of the total females in the population. A fitness cost appeared to be associated with the pyrethroid resistant allele, as the resistant form was selected against in the absence of the pyrethroid ear tags. Despite this selection in favor of the susceptible allele and the annual alternation of pyrethroid and OP ear tags, the percentage of homozygous susceptible flies never reached over 19% of the population, resistant alleles of the sodium channel remained at high levels in the population, and horn fly control on cattle with either type of tag quickly became minimal.

Topics: Animals; Cattle; Cattle Diseases; Ectoparasitic Infestations; Female; Genotype; Insect Control; Insecticide Resistance; Insecticides; Male; Muscidae; Nitriles; Polymerase Chain Reaction; Pyrethrins; Sodium Channels