In vitro activity of fluralaner and commonly used acaricides against Dermanyssus gallinae isolates from Europe and Brazil

Abstract

BackgroundThe poultry red mite Dermanyssus gallinae negatively impacts bird welfare and health, and interferes with egg production and quality, while emerging acaricide resistance limits control options. Fluralaner, a novel miticide for administration in drinking water, is approved for control of D. gallinae infestations. Mite sensitivity testing is relevant to gauge field isolate susceptibility to available treatments.MethodsThirteen D. gallinae isolates collected during 2014 through 2016 from farms in Germany, France, Spain and Brazil, and a 2001 laboratory-maintained isolate were used for acaricide contact sensitivity testing. Tested compounds were cypermethrin, deltamethrin, phoxim, propoxur, and the recently available acaricides, spinosad and fluralaner. In each study, at least one isolate was exposed to increasing concentrations of at least one acaricide. In one study, additional testing determined the sensitivity of the 2001 isolate to fluralaner using a mite-feeding test, and of fluralaner, phoxim and spinosad using an immersion test. At least two replicates were used for each dilution. Vehicle and untreated controls were also included.ResultsBased on 90% mortality (LC90) values, the laboratory isolate was susceptible to fluralaner (15.6–62.5 parts per million, ppm), phoxim (< 500 ppm), propoxur (< 125 ppm), and deltamethrin (500–1000 ppm). All field isolates remained sensitive to fluralaner concentrations ≤ 125 ppm. Spinosad LC90 values for laboratory and field isolates ranged between 2000–4000 ppm. For phoxim, relative to the laboratory isolate, there was reduced sensitivity of two German isolates (LC90 up to 4000 ppm) and two French isolates (> 4000 ppm). An isolate from Spain demonstrated reduced sensitivity to phoxim, propoxur and deltamethrin; an isolate from Brazil showed reduced sensitivity to propoxur and cypermethrin. Mite LC90 when exposed to fluralaner by blood feeding was < 0.1 ppm.ConclusionsContact sensitivity testing indicated apparent resistance to at least one of phoxim, deltamethrin, cypermethrin and propoxur in 13 field isolates from Europe and Brazil. All isolates were highly susceptible to fluralaner. Fluralaner was approximately 1000 times more active by feeding than by contact. Fluralaner’s distinct mode of action and efficacy against isolates largely refractory to those acaricides, makes it a promising option for the control of D. gallinae infestations of poultry.

Efficacy ofλ-cyhalothrin, amitraz, and phoxim against the poultry red miteDermanyssus gallinaeDe Geer, 1778 (Mesostigmata: Dermanyssidae): an eight-year survey

“…Pyrethroids, such as λ-cyhalothrin and bifenthrin, were largely used in poultry farms to fight the house fly Musca domestica L. (Abbas et al, 2016), and this may have contributed to selection of resistant individuals of D. gallinae, too. This could account for the early rise of resistant D. gallinae populations, which was firstly documented more than 20 years ago (Beugnet et al, 1997) and it has been repeatedly reported from mites collected in poultry farms (Nordenfors et al, 2001;Thomas et al, 2018). A similar trend was observed for O. sylviarum populations collected in the field in California (Mullens et al, 2017).…”

“…Conversely, out of the three tested drugs, phoxim was the only one authorized for use in the presence of animals in poultry farms of Italy, and its operating procedures were adequately conceived and set up, especially in terms of dosage and administration schedule. This fact may have helped to keep low the proportion of resistant groups of D. gallinae, insomuch that less susceptible populations have recently been detected (Thomas et al, 2018). In this investigation, phoxim-resistant populations were only found in 2015, and it is possible that factors other than contacts with acaricides should be intervened.…”

“…Nowadays, the emergence and spread of resistant pest populations is still a major problem worldwide (Sparks & Nauen, 2015), which impacts on wide areas of human and veterinary medicine and agriculture. In this scenario, D. gallinae does not represent an exception, as the presence of PRM populations resistant to one or more acaricides has been reported from 1985 (Zeman & Železný, 1985) up to the present time (Thomas et al, 2018).…”

Use of oral fluralaner (Bravecto) to successfully manage adult‐onset generalised demodicosis in a silver fox (Vulpes vulpes)

“…Anecdotal evidence suggests that these products have a high efficacy rate at the doses labelled for flea and tick prevention against parasites including Demodex species, Sarcoptes species, Otodectes species, Cheyletiella species, Lynxacarus species and various poultry mites 2 12–15. Use in off‐label hosts including poultry, pigs, rabbits, hedgehogs and wildlife suggest this drug class has a wide margin of safety 16–24. Consideration for use in human beings using porcine models of disease may lead to promising breakthroughs in control of parasitic infections in endemic regions of the world 25.…”

The evaluation of feeding, mortality and oviposition of poultry red mite (Dermanyssus gallinae) on aging hens using a high welfare on-hen feeding device

“…Positive results are followed by field testing, which by necessity involves large numbers of parasites and hens in order to account for the many variables involved in infestation of hens within a henhouse (e.g. Bartley et al , 2015 ; Bartley et al , 2017 ; Thomas et al , 2018 ; Wright et al , 2016 ). The in vitro method of testing novel systemic control compounds (e.g.…”