Acaricide residues in laying hens na- turally infested by red mite Dermanyssus gallinae

In poultry industry, the control of the red mite Dermanyssus galli- nae (De Geer, 1778) (Mesostigmata: Dermanyssidae) (PRM) pri- marily relies worldwide on acaricides; the most widely used are carbamates, followed by amidines, pyrethoids and organophospho- rus. Despite their proved efficacy against D. gallinae, none of these compounds is specifically registered in Italy for use against red mites, except for the very recently labeled organophosphate and spinosad-based products. This means that farmers have always used -and continue to use - acaricides registered for use in agricul- ture or for other farm animal species. In the last few years, some acaricides have become worldwide less effective; thus, to control mite infestations farmers are keen to use chemicals at higher con- centrations, more frequently and repeatedly. This improper use of acaricides to control PRM could lead firstly to the development of acaricide-resistant D. gallinae populations, as previously observed also in Italy (Marangi M et al, 2009, Exp Appl Acarol, 48:11–18), and, more importantly, to the accumulation of acaricides in chick- ens’ organs, in tissues and in eggs. AIM: To highlight some concealed situations of risk for human health, we investigated three farms (denoted A, B and C) in a southern Italian region where D. gallinae populations were found to be significantly tolerant to carbammates and permethrins (Marangi M et al, o.c.), likely due to the high chemical pressure. MATERIALS AND METHODS: Fifteen laying hens at the end of their production cycle and destined to the slaughterhouse were taken from each farm. In the necropsy lab, all 45 hens were euth- anized, and a total of 225 samples were taken from skin, fat, liver, muscle, hearth, and kidney. Feed samples were also collected from each farm. Analysis was carried out using a HPLC coupled to a QQQ Triple Quadrupole Mass Detector for the residual contents of carbaryl and permethrin from all matrices and detection limits and the average pesticide recoveries were performed. Statistical analysis (one-way variance analysis, Duncan’s test and one-tailed t-student test) was applied and the Statistica 6.0 software package was used. RESULTS: Thirty-seven (82.2%) laying hens were positive for car- baryl residues and 4 (8.8%) for permethrin. Ninety-one (40.4%) samples resulted positive for carbaryl (25 skin, 27 fat, 8 liver, 16 muscle, 15 heart and kidney samples), showing a mean concentra- tion of 5 ppm, 0.04 ppm, 0.05 ppm, 0.14 ppm, 0.04 ppm, respec- tively. Four samples (1.7%) resulted positive for permethrin (2 fat and 2 liver samples), with a mean concentration of 0.012 ppm and 0.006 ppm, respectively. On one farm (Farm B), all investigated hens were found to be contaminated by carbaryl, and 80% of their organs and tissues contained residues of the compound, with the highest concentrations in the skin (16 ppm), fat (0.11 ppm) and muscle (0.3 ppm). Concentrations of carbaryl exceeding the detec- tion limit (0.005 ppm) were registered in the skin and fat of birds from two farms (p<0.01), although these concentrations remained below the maximum residue limit (MRLs) (0.05 ppm) (p<0.01). All organs/tissues of hens from a third farm were significantly more contaminated, with skin and muscle samples exceeding the MRL (0.05 ppm) (p<0.01). CONCLUSIONS: This study shows that most laying hens (37 out of 45) from all three investigated farms were contaminated by car- baryl, and that the hens of one farm also contained permethrin. Furthermore, with different accumulation levels among animals - possibly due to differences in factors like management strategies and unpredictable individual predispositions - all organs/tissues were contaminated by carbaryl, with the highest levels found in skin, fat, and muscle. These data are all worrying, because: a) car- baryl was banned by the EU in 2007 (Allegato I, Direttiva 91/414, 1376/07, 07/355); b) no carbaryl-based products specifically la- beled for use against D. gallinae infestation were available on the Italian market before the ban; c) no registered permethrin-based products are available on the market for use against red mite in- festation; and d) tissues and organs from laying hens can be con- sumed as food. The detection of acaricide residues in tissues/organs of laying hens seems to confirm - at least in the studied area - their extensive and improper use by farmers against D. gallinae. It also shows up the illegal use and persistent commercialization of pesticides banned years ago (carbaryl), and more importantly, it indi- cates that some specific/restricted situations of misuse or abuse of chemicals may remain undetectable. The current availability on the Italian market of licensed products against D. gallinae may help farmers to better manage infestation and to limit the consequences of misuse of chemicals.