Assessment of Fluralaner Treatment in Eliminating Dermanyssus Gallinae Infestation From Commercial Layer Farms, and the Potential for Derived Benefits of Improved Bird Welfare and Productivity.

Abstract

Background. Infestations with the poultry red mite (PRM), Dermanyssus gallinae, can result in anaemia, stress-related behaviours linked to reduced laying hen welfare, and impaired productivity. A study was conducted to investigate the potential welfare benefits of PRM elimination following fluralaner treatment.MethodsA single poultry house was selected on each of two layer farms, one free-range, one aviary, containing 5,400 Lohmann LSL hens and 42,400 Lohmann Brown hens, respectively. Fluralaner (Exzolt®; 0.5 mg/kg body weight) was administered twice, seven days apart (Weeks 0 and 1). Mite populations were regularly monitored by traps left in place for one to two days. Infra-red cameras monitored night-time hen behaviours weekly, beginning five weeks pre-treatment, continuing for five and six weeks post-treatment on the free-range and aviary farms, respectively. Weekly daytime behaviours were recorded on the free-range farm. On the aviary farm, blood samples were collected from 50 randomly selected hens during Weeks -3, -1 and 5. On the free-range farm, eggs were randomly collected for corticosterone analysis during Weeks -6, 0 and 6, and on the aviary farm during Weeks -3, -1 and 5. Production parameters were assessed using farm records.ResultsFluralaner efficacy on the free-range farm was >99% following the first administration, and on the aviary farm was 100% at Week 1 and at all subsequent mite counts. On both farms, treatment was followed by significant reductions in night-time preening, head scratching, head shaking, and activity, and on the aviary farm in vertical wing shaking and gentle feather pecking. On the free-range farm there were significant daytime reductions in head scratching, head shaking and preening. Post-treatment increases in egg and plasma corticosterone were suggestive of stress factors extra to mite infestation. Red blood cell counts and haematocrit increased following treatment. On the free range farm, relative to standard production parameters for LSL hens, the decline in laying rate with increasing bird age was less than expected, and the increase in egg weight greater than expected. 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.