Beak condition and cage density determine abundance and spatial distribution of northern fowl mites, Ornithonyssus sylviarum, and chicken body lice, Menacanthus stramineus, on caged laying hens

Abstract

Adult White Leghorn hens (Hy-Line strain W-36) were inoculated with either northern fowl mites or chicken body lice, and the ectoparasite populations were monitored over periods of 9 to 16 wk. Two beak conditions (beak trimmed or beak intact) and 2 housing densities (1 or 2 hens per 25 × 31 cm suspended wire cage) were tested. Populations of both ectoparasites were at least 10 times lower on beak-intact hens compared with populations on beak-trimmed hens. Cage density did not influence mite numbers, but higher numbers of lice (2 to 3 times) developed on hens held at the higher cage density. Louse distribution on the body and louse population age structure were also influenced by host beak condition. Beak-intact hens had a higher proportion of lice under the wings, whereas beak-trimmed hens had the majority of lice on the lower abdomen. Louse populations on beak-trimmed hens also comprised relatively more immature stages than populations found on beak-intact hens. The effects are likely related to decreased grooming efficiency by beak-trimmed hens and, in the case of lice, the higher host density. The high mite and louse populations on most commercial caged laying hens are probably a direct result of beak trimming. However, selection of more docile breeds that can be held without trimming may allow the hens themselves to reduce ectoparasites below economically damaging levels. This could benefit producers, animal welfare advocates, and human health by reducing 1) costs of beak trimming, 2) pesticide treatment costs (including human and bird chemical exposure concerns), and 3) objections to beak trimming from the animal welfare community.

A gallery of the key characters to ease identification of Dermanyssus gallinae (Acari: Gamasida: Dermanyssidae) and allow differentiation from Ornithonyssus sylviarum (Acari: Gamasida: Macronyssidae)

“…Apparent confusion with similar mite species, primarily O. sylviarum which may cohabit with D. gallinae and pose similar problems for hen [7,9,32] and human [4,18,20-23,33] health, may also hamper positive identification and appropriate treatment of both species. Hence, the current work also makes comparison among these two mites for the benefit of the end user.…”

Dustbathing behavior: Do ectoparasites matter?

“…If infestation with different kinds of parasites does not change dustbathing behavior, it would strengthen the hypothesis that dustbathing is not functionally related to the removal of ectoparasites. In addition, it is known that hens with an intact beak are able to reduce their ectoparasite loads (Mullens et al, 2010) via preening directed to the body areas that are most severely infested (Vezzoli et al, 2015b). However, to our knowledge there have been no studies evaluating the interactive effects of preening and dustbathing in beak-intact hens on ectoparasite loads.…”

Housing and dustbathing effects on northern fowl mites (Ornithonyssus sylviarum) and chicken body lice (Menacanthus stramineus) on hens

“…In the present study, mite populations on cage-free hens occasionally tended to be higher early in infestation than those on hens in cages, but large or consistent 'density' effects on mites were not seen. Mullens et al (2010) showed that hens held in pairs per cage supported about twice as many lice as hens held singly in cages, presumably because crowded hens were less efficient in grooming. In the present study, no significant housing effects on CBL abundance emerged in any trial.…”