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ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » Research » Publications at this Location » Publication #110778
Title: CHARCTERIZATION OF ACARICIDE RESISTANCE IN RHIPICEPHALUS SANGUINEUS (LATREILLE) (ACARI:IXODIDAE) COLLECTED FROM THE COROZAL ARMY VETERINARY QUARANTINE CENTER, PANAMA

Author
item MILLER, ROBERT - 6205-05-00
item George, John
item Guerrero, Felicito
item CARPENTER, LARRY - U S ARMY
item Welch, John

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Infestations of Rhipicephalus sanguineus Latreille, also known as the Brown dog tick, can be very hard to control. Each of the three free-living stages are capable of surviving long periods of time without a host. Samples of this tick were collected from the Corozal Army Veterinary Quarantine Center in Panama and characterized for resistance to five classes of acaricides. A resistant strain of these ticks had very high resistance to permethrin, DDT, and coumaphos; moderate resistance to amitraz; and no resistance to fipronil when compared to susceptible strains. Resistance to both permethrin and DDT suggests mutation of the sodium channel, the target site for both permethrin and DDT, is involved in the resistance mechanism. However, synergist studies suggest that metabolic enzyme activity may also be involved. The addition of triphenylphosphate, an inhibitor of metabolic enzymes known as esterases, lowered the resistance. This suggests that esterases may be involved in pyrethroid resistance. Further evidence for this is shown with gel assays which found increased esterase activity in the resistant strain compared to susceptible strains. The esterase activity was suppressed with the addition of TPP. Resistance to coumaphos in the resistant strain was not affected by the addition of TPP or PBO. This suggests that a mutation of acetylcholinesterase, the target site for coumaphos, may be involved in this mechanism of resistance.

Technical Abstract: Rhipicephalus sanguineus Latreille were collected from the Corozal Army Veterinary Quarantine Center in Panama and characterized for resistance to five classes of acaricides. These ticks had very high resistance to permethrin, DDT, and coumaphos; moderate resistance to amitraz; and no resistance to fipronil when compared to susceptible strains. Resistance to both permethrin and DDT suggests a target site mutation of the sodium channel. However, synergist studies suggest that metabolic enzyme activity may also be involved. The LC50 estimate for permethrin was lowered in the Panamanian strain with the addition of triphenylphosphate, but not with the addition of piperonyl butoxide. This suggests that esterases may be responsible for pyrethroid resistance. Further evidence for this is shown with increased esterase activity to b-naphthyl acetate that was suppressed with the addition of TPP. The LC50 estimate to coumaphos in the Panamanian strain was not lowered by the addition of TPP or PBO. This suggests that a target site mutation of acetylcholinesterase may be involved in coumaphos resistance. Resistance to amitraz was measured through a modification of the Food and Agriculture Organization Larval Packet Test.