Eidgenössisches Departement des Innern EDI Bundesamt für Gesundheit BAG Direktionsbereich Verbraucherschutz Study on Tabanid Flies on Horses Vienna, 23. June 2016 Workshop on Repellents Stefanie Strauch Federal Office of Public Health Consumer Protection Directorate Chemical Products Division
Study on the efficacy of N,N-diethyl-3-methylbenzamide (DEET) against tabanid flies on horses Conny Herholz, Chris Kopp, Manuela Wenger; Alexander Mathis, Salome Wägeli, Nathalie Roth; Hochschule für Agrar-, Forst- und Lebensmittelwissenschaften HAFL t
Introduction
Female horse fly as a pest (Baldachino et al., 2014) Polarotactic, seeking water Prefers unicolor, humid surfaces Horses are an attractive point of attack during a ride in the field Vector of the contagious Equine Infectious Anemia (EIA) Background of the study Viral horse disease which disseminated in Europe in the last years (Issel and Foil,1984; Herholz et al., 2014) Mode of action of N,N-diethyl-3-methyl-benzamide (DEET) Modulation of the nerve signals of olfactory receptors, the exact mode of action is not yet fully clear (Leal, 2014, Pellegrino et al., 2011) Goldstandard as insect repellent for humans (Frances, 2006; Katz et al., 2008)
Aim of the study Sufficient reduction of horse fly infestation by the repellent of Huebeli-Stud Horse Care AG: Establishment of a practical field-test Test of performance and of the declared protection time (4h) = EU requirements (Guidance Efficacy Evaluation of PT 18+19)
Materials & Methods
Prior clarification of recording technique Testing of recording technique in May Video- or photo recordings?
Horse farms und test design 4 farms (A-C) in the Kanton Bern, Altitude 560 to 1000 MASL Farm A used for pre-test (test of test protocol) end of June, as well as for main test in July / August) Realisation on sunny, warm and calm days (Ø T = 34 C, Humidity 32 %)
Horses 12 horses, 10 WB, 2 FM Ø 11 J (3-20 J), 4 geldings, 8 mares Dark brown (6), brown (6) 4 horses of farm A used for pre- as well as main test (overall 16 tests without repellent, 16 tests with repellent)
Cross-over Design
Time schedule
Longe until perspiration starts
HORSE PAL fly trap Screening of species spectrum (scientific interest)
Horse fly counting Right body side at identical locations Counted and photographed Data of direct counting was used
Repellent BRUM Huebeli-Stud Horse Care AG Total 8 pumps/horse
Statistics Quantification of relative efficacy Relative efficacy rel.3h = (ohne.3h mit.3h) / ohne.3h rel.4h = (ohne.4h mit.4h) / ohne.4h Statistical analysis with R (Version 3.02)
Results
Raw data of horse fly countings
Relative efficacy 100 % relative efficacy in 8 of 16 horses after 3h & 4h Mean relative efficacy is 83% after 3h and 73% after 4h
Number of horse flies after 180 min
Number of horse flies after 240 min
Discussion
Repellent DEET Blume et al. (1971): 75% DEET-emulsion showed efficacy up to 3 hours (n=2 horses) 75% DEET caused skin abrasions In the present study, an efficacy of 3 and 4 h, resp., was shown with a concentration of 15-17% DEET (n= 12 horses) Inter-study differences regarding concentration / horse fly species?
Test design Practical study design, horse fly infestation quantifiable
HORSE PAL fly trap Horse fly trap in this study was not successful for measuring the insect pressure.
Horse fly counting Horse fly infestation counted directly as well as photographed Direct counting of horse flies in default time frame was successful Obvious difference between treated and non-treated horses strong defensive movements Difference between flies and horse flies more distinct for direct counting than on photos
Conclusion DEET in a 15-17% oil-water-emulsion can be recommended as a repellent against horse flies on horses 80% resp. 71% relativ efficacy 3 resp. 4 hours after application (confidence 89%) Consider manufacturer specifications: Toxicity
Open questions (CH authorities) DEET in a 15-17% oil-water-emulsion can be recommended as a repellent against horse flies on horses For 3 or 4 hours? 80% resp. 71% relative efficacy 3 resp. 4 hours after application (confidence 89%) is a confidence level of 89% sufficient or should it be >90%? Is an efficacy of 71% with a confidence level of 89% sufficient to claim 4h?
Acknowledgment All horse owners & farm managers Huebeli Stud Horse AG for providing of the repellent & partical financing of the project
Eidgenössisches Departement des Innern EDI Bundesamt für Gesundheit BAG Direktionsbereich Verbraucherschutz Time for questions