Pyrethroid knock down resistance in horn fly (Diptera: Muscidae) populations in Brazil

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Pyrethroid knock down resistance in horn fly
(Diptera Muscidae) populations in Brazil

• Sabatini, G.A.1 Ribolla, P.E.M.2 Barros,
  A.T.M.3 Guerrero, F.D.4 Schmaker, T.T.S1.

1 UniFMU/ USP 2 UNESP/ Botucatu 3 EMBRAPA
CPAP 4 USDA-ARS
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1. Introduction

• Stress and reduction in rate of weight gain
  (Campbell 1976)
• efficiency of feed utilization and milk
  production by the bovine host (Kinzer et al.
  1984)
• Hide damage (Gugliemone et al. 1999)
• Losses in Brazil US 150 million per year (Grisi
  et al., 2002)

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1. Introduction

• To minimize losses insecticides - resistance
• Few studies on mechanisms of resistance
• kdr gene mutation (Guerrero et al. 1997)
• Pyrethroids sodium channel

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1. Introduction

• Sodium channel structure x pyrethroids
• Drosophila melanogaster (Meigen) (Armichot et al.
  1992)
• Blattella germanica (L.) (Dong Scott 1994)
• Musca domestica (L.) (Miyasaki et al. 1996)

• Horn fly - Guerrero et al. (1997) (L1014F and
  M918T)
• Spread of pyrethroid resistance - (Barros, 2004)
• Mechanism (s)?

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2. Material and Methods

• 2.1. Fly collections
• 30 populations (/- 50 flies each/ total of 1454
  flies) from all Regions of Brazil
• - Embrapa/ Barros, ATM
• - SP RJ RO and RS

• 2.2. Polymerase chain reactions
• Extraction of Genomic DNA (individual) Aljanabi
  Martinez (1997).
• The kdr gene mutation was detected according to
  Guerrero et al. (1998)
• PCR products were visualized on 1 agarose TBE
  gels coloured by ethidium bromide staining and UV
  illumination.

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3. Results and Discussion
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3. Results and Discussion
Table 1 Kdr detection in diferent populations of
Haematobia irritans irritans from Brazil.
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3. Results and Discussion
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3. Results and Discussion

• Control of horn fly in Brazil 91 products
  registered

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3. Results and Discussion

• Low frequencies of kdr gene
• Only 3 populations higher than 20

• Guglielmone et al., 2002 Kdr allelic frequency
  50

• Li et al., 2003
• High numbers of SS and SR individuals

Resistance to pyrethroids is sex-linked
(MacDonald Schmidt, 1987)
Adult males were more susceptible than the
females (McDonald Schmidt, 1990).
Li et al., 2003 Corroborate it in Mexican
populations, but not in American.
There was no relation between sex and kdr among
Brazilian populations.
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3. Results and Discussion

• Pyrethoroid resistance in the horn fly

Metabolic (Lockwood et al., 1985)
Behavioural (Sheppard, 1995)
KDR (Bull et al., 1988, Sparks et al., 1990)

• Frequency of kdr gene was quite low

Fitness cost (Scott et al., 1997)
kdr amplification was not observed in all
populations found to be resistant in the
bioassays.
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3. Results and Discussion
These findings indicates that there is at least
another mechanism playing an important role in
resistance to pyrethroids