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

Abstract

Background Poultry 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. Methods A 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. Results Throughout 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. Conclusion Fluralaner 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.

Effects of the poultry red mite (Dermanyssus gallinae) load on the plumage condition in commercial laying hen farms

“…To the authors’ knowledge, this is the first time that the effect of the PRM load on the plumage condition has been demonstrated in a longitudinal study design over the laying period. Recently, Petersen et al [ 13 ] and Temple et al [ 12 ], using direct behavioral observations, found a reduction in SFP with treatment-induced decrease in the PRM load in laying flocks treated with fluralaner, which is an isoxazoline to be administered via the drinking water for mite control. Temple et al [ 12 ] discussed the concomitant reduction in pain and frustration with the reduction in the PRM load in the flocks as relevant to their findings.…”

“…PRM infestation is accompanied by a reduction of laying performance and egg weights [ 12 ]. Due to the particular lifestyle of PRMs, with includes long stays away from their hosts in hiding places that are difficult to access [ 1 ], alternative strategies, such as the heat treatment of barns [ 32 ] or medical treatment of hens via drinking water [ 12 , 13 ], are becoming increasingly important. Decru et al [ 33 ] recommended an integrated pest management approach to PRM control, with the prevention of introduction and the monitoring of parasite loads as key approaches.…”

“…To the authors' knowledge, this is the first time that the effect of the PRM load on the plumage condition has been demonstrated in a longitudinal study design over the laying period. Recently, Petersen et al [13] and Temple et al [12], using direct behavioral observations, found a reduction in SFP with treatment-induced decrease in the PRM load in laying flocks treated with fluralaner,…”

“…A cross-sectional study by Heerkens et al [ 11 ] observed lower PD in flocks without PRM compared to those with PRM infestations. Recent studies that included direct behavioral observations showed a decrease in SFP due to a treatment-induced reduction in PRM infestation in laying flocks [ 12 , 13 ]. A more practical approach to the assessment of behavioural disorders that can be implemented in farm routines is integument scoring [ 14 ], which is an indirect method used to quantify SPF and cannibalism [ 15 ].…”

Dermanyssus gallinae: the long journey of the poultry red mite to become a vector

“…The poultry production system considers infestation by Dermanyssus gallinae , commonly referred to as the poultry red mite (PRM), to be a matter of concern because of its deleterious impact on both productivity and welfare of the animals [ 1 , 2 ]. In addition, in highly infested environments, poultry workers may also be at risk of infestation by PRMs, with clinical conditions varying from itching, dermatitis and erythematous rashes to papules, urticarial plaques and erythema [ 3 – 7 ].…”