Assessment of fluralaner as a treatment in controlling Dermanyssus gallinae infestation on commercial layer farms and the potential for resulting benefits of improved bird welfare and productivity

Ivo Petersen,Eric Pagot,Déborah Temple,Eva Zschiesche,Katharina Johannhörster,Damian Escribano,Emmanuel Thomas

doi:10.1186/s13071-021-04685-7

Ivo Petersen, Eric Pagot + Show 5 more

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https://doi.org/10.1186/s13071-021-04685-7

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Abstract

BackgroundPoultry red mite (PRM) (Dermanyssus gallinae) infestations are a cause of anaemia, impaired productivity and stress-related behaviours linked to reduced hen welfare. A study investigated the potential health, welfare and productivity benefits following fluralaner treatment to eliminate PRM from infested hens.MethodsA PRM-infested layer house was selected on a free-range farm (5400 hens) and an aviary farm (42,400 hens). Fluralaner (Exzolt®; 0.5 mg/kg body weight) was administered twice, 7 days apart (Weeks 0 and 1), via drinking water. Mite populations were monitored by traps. Cameras recorded nighttime hen behaviours weekly, pre- and post-treatment. On the free-range farm, daytime behaviours were also recorded weekly. For pre- and post-treatment corticosterone assessments, eggs were randomly collected on both farms, and blood samples were collected from 50 randomly selected aviary farm hens. Production parameters were assessed using farm records.ResultsThroughout the post-treatment period, fluralaner efficacy against PRM was > 99% on both farms. On the aviary and free-range farms, treatment was followed by significant nighttime increases in the proportion of resting hens (P < 0.0001; P = 0.0175, respectively). Significant post-treatment versus pre-treatment nighttime reductions were observed in head shaking (aviary, P < 0.0001; free-range P = 0.0233) and preening (P = 0.0032; P = 0.0018) and on the aviary farm in bouts of body shaking (P = 0.0108), vertical wing shaking (P = 0.0002), head scratching (P = 0.0335), and gentle feather pecking (P < 0.0001). On the free-range farm there were significant daytime reductions in head scratching (P < 0.0001), head shaking (P = 0.0492) and preening (P = 0.0012). Relative to standard production parameters, no differences were detected on the aviary farm, but on the free-range farm the laying rate decline with increasing age was less than expected and the increase in egg weight greater than expected. Post-treatment increases in egg and plasma corticosterone were suggestive of stress factors in addition to mite infestation. Red blood cell counts and haematocrit increased following treatment.ConclusionFluralaner treatment eliminated mite challenge, leading to improved hen welfare and health, based on reductions in stress-related behaviours and restoration of the anaemia-inducing effects of mite blood feeding.Graphical

Highlights

Poultry red mite (PRM) (Dermanyssus gallinae) infestations are a cause of anaemia, impaired productivity and stress-related behaviours linked to reduced hen welfare
The objective was to assess the effects of mite elimination by an acaricidal treatment with fluralaner on behavioural welfare parameters in chickens naturally infested with D. gallinae
Counts of Dermanyssus gallinae Prior to treatment, the mite counts on the aviary farm comprised approximately 70% adults and 30% nymphs and on the free-range farm approximately equal proportions of adults and nymphs, with only a few larvae (≤ 1% of motile mite life stages) identified on each farm

Summary

Introduction

Poultry red mite (PRM) (Dermanyssus gallinae) infestations are a cause of anaemia, impaired productivity and stress-related behaviours linked to reduced hen welfare. Laboratory infestations of poultry have been found to be a cause of stress and impaired welfare, manifested by behavioural changes such as an increase in grooming and head scratching [5], increased levels of plasma corticosterone, adrenaline and β-globulins, and reductions in γ-globulins in infested hens compared to uninfested controls [6, 7]. There has been a substantial increase in the number of laying hens in Europe [4] These losses are attributed to the negative impact of PRM infestations on the feed conversion ratio, egg production, proportion of downgraded eggs, susceptibility to intercurrent disease and mortality rate [1, 3, 4, 9]. The problem of flock infestations with the PRM has been exacerbated by the difficulties of implementing measures that are effective in the face of increasing resistance to registered chemicals, while being safe for birds, workers and the environment and avoiding egg and meat residues that could have a detrimental effect on human health [1, 4, 10, 11]

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