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Title: Mechanism of resistance to synthetic pyrethroids in buffalo flies in south-east Queensland

Author
item ROTHWELL, J - University Of Queensland
item MORGAN, JAT - Queensland Department Of Primary Industries & Fisheries
item JAMES, P - Queensland Department Of Primary Industries & Fisheries
item BROWN, G - Queensland Department Of Primary Industries & Fisheries
item Guerrero, Felicito
item JORGENSEN, W - Queensland Department Of Primary Industries & Fisheries

Submitted to: Australian Veterinary Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2010
Publication Date: 3/1/2011
Citation: Rothwell, J.T., Morgan, J., James, P., Brown, G., Guerrero, F., Jorgensen, W. 2011. Mechanism of resistance to synthetic pyrethroids in buffalo flies in south-east Queensland. Australian Veterinary Journal. 89(3):70-72.

Interpretive Summary: Buffalo fly (Haematobia irritans exigua) and horn fly (Haematobia irritans irritans) cause irritation and production loss in much of the cattle producing area of the world. These two species are closely related and in Australia losses from buffalo fly were recently estimated at A$78m per year. Buffalo fly control is largely performed by using organophosphate(OP)/carbamate, synthetic pyrethroid(SP) and macrocyclic lactone insecticides formulated for topical use. In Australia buffalo fly resistance to SPs was first recorded in 1980. Resistant flies were 45 times less sensitive to the SP fenvalerate than susceptible flies and 29 x less susceptible to the SP cypermethrin. By the 1990s resistance to the SPs was widespread in populations from coastal northeastern Australia. Resistance in American horn flies was found to be associated with specific mutations in the gene coding for the sodium channel protein, the target of SP activity. Our study assessed resistance to SPs at the University of Queensland, Pinjarra Hills farm and investigated whether SP resistance-associated sodium channel gene mutations were present in buffalo fly. We used a PCR assay developed to detect the SP resistance-associated gene mutations in the horn fly to assay for these gene mutations in buffalo fly. The kdr sodium channel gene mutation was found in the buffalo fly, however, the super-kdr mutation was not detected in this buffalo fly population.

Technical Abstract: Buffalo fly (Haematobia irritans exigua) and horn fly (Haematobia irritans irritans) cause irritation and production loss in much of the cattle producing area of the world. In Australia losses from buffalo fly were recently estimated at A$78m per year. Control is largely performed by using organophosphate(OP)/carbamate, synthetic pyrethroid(SP) and macrocyclic lactone insecticides formulated for topical use. In Australia resistance to SPs was first recorded in buffalo flies in 1980 associated with oversprays of DDT and fenvalerate. Resistant flies were 45 times less sensitive to fenvalerate than susceptible flies, 29 x less susceptible to cypermethrin and more than 1000 x less susceptible to DDT. By the 1990s resistance to the SPs was widespread in populations from coastal northeastern Australia. Resistance in American horn flies was associated with the kdr and super-kdr point mutations in the gene encoding the voltage gated sodium channel. This study assessed resistance to SPs at the University of Queensland, Pinjarra Hills farm and investigated whether the kdr and super-kdr mutations were present in buffalo fly. The multiplex PCR assay developed to detect the kdr mutations in the horn fly was successful in detecting the kdr mutation in buffalo fly. The super-kdr mutation was not detected in this buffalo fly population.