Molecular investigations of cytochrome c oxidase subunit I (COI) and the internal transcribed spacer (ITS) in the poultry red mite, Dermanyssus gallinae, in northern Europe and implications for its transmission between laying poultry farms

Samples of Dermanyssus gallinae (DeGeer) (Acari: Dermanyssidae) from more than 49 Norwegian and Swedish laying poultry farms, and additional samples collected from Scottish, Finnish, Danish and Dutch layer farms, were compared genetically. Analysis of partial mitochondrial gene cytochrome c oxidase subunit I (COI) sequences of mites from Norway and Sweden revealed 32 haplotypes. Only single haplotypes were found on most farms, which suggests that infections are recycled within farms and that transmission routes are few. Both Norwegian and Swedish isolates were found in the two major haplogroups, but no haplotypes were shared between Norway and Sweden, indicating little or no recent exchange of mites between these countries. There appears to be no link between haplotypes and geographical location as identical haplotypes were found in both the northern and southern Swedish locations, and haplotypes were scattered in locations between these extremes. The current data suggest that wild birds in Sweden are not a reservoir for D. gallinae infection of layer farms as their mites were genetically distinct from D. gallinae of farm layer birds. Transmission of the poultry red mite in Scandinavia is thus likely to depend on synantropic factors such as the exchange of contaminated material or infested birds between farms or facilities.     

Efficacy of a novel neem oil formulation (RP03™) to control the poultry red mite Dermanyssus gallinae

Dermanyssus gallinae (Mesostigmata: Dermanyssidae) is the most harmful ectoparasite of laying hens, represents an occupational hazard for poultry workers, and a growing threat to medical science per se . There is increasing demand for alternative products, including plant‐derived acaricides, with which to control the mite. The present study investigated the efficacy of neem oil against D. gallinae on a heavily infested commercial laying hen farm. A novel formulation of 20% neem oil, diluted from a 2400‐p.p.m. azadirachtin‐concentrated stock (RP03?), was administered by nebulization three times in 1 week. Using corrugated cardboard traps, mite density was monitored before, during and after treatment and results were statistically analysed. Mite populations in the treated block showed 94.65%, 99.64% and 99.80% reductions after the first, second and third product administrations, respectively. The rate of reduction of the mite population was significantly higher in the treated block (P < 0.001) compared with the control and buffer blocks. The results suggest the strong bioactivity of neem, and specifically of the patented neem‐based formulation RP03?, against D. gallinae . The treatment was most effective in the 10 days following the first application and its effects persisted for over 2 months. Further studies will aim to overcome observed side effects of treatment represented by an oily layer on equipment and eggs.     

Environmental interactions with the toxicity of plant essential oils to the poultry red mite Dermanyssus gallinae

The toxicity of a range of plant essential oils to the poultry red mite, Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae), a serious ectoparasitic pest of laying hens throughout Europe and elsewhere, was assessed in the laboratory. Dermanyssus gallinae may cause losses in egg production, anaemia and, in extreme cases, death of hens. With changes in legislation and consumer demand, alternatives to synthetic acaricides are needed to manage this pest. Fifty plant essential oils were selected for their toxicity to arthropods reported in the literature. Twenty-four of these essential oils were found to kill > 75% of adult D. gallinae in contact toxicity tests over a 24-h period at a rate of 0.21 mg/cm². Subsequent testing at lower rates showed that the essential oils of cade, manuka and thyme were especially toxic to adult D. gallinae . The toxicity of the seven most acaricidal essential oils was found to be stable at different temperatures likely to be encountered in commercial poultry housing (15°C, 22°C and 29°C), although results suggest that humidity and dust might influence the toxicity of some of the oils tested. The toxicity of clove bud essential oil to D. gallinae , for example, was increased at high humidity and dust levels compared with ambient levels. The results suggest that certain essential oils may make effective botanical pesticides for use against D. gallinae , although it is likely that issues relating to the consistency of the toxic effect of some oils will determine which oils will be most effective in practice.     

Wild boars: A potential source of Erysipelothrix rhusiopathiae infection in Japan

The potential role of wild boars as a source of erysipelas infection was investigated. An ELISA test of wild boar serum samples from 41 prefectures in Japan revealed that proportions of the Erysipelothrix rhusiopathiae‐positive samples were very high in all the prefectures, and the mean positive rate was 95.6% (1312/1372). Serovars of E. rhusiopathiae isolates from wild boars were similar to those of previously reported swine isolates, and all serovar isolates tested were found to be pathogenic to mice. These results suggest that wild boars in Japan constitute a reservoir of E. rhusiopathiae and may pose risks to other animals.     

How to obtain a bloodmeal without being eaten by a host: the case of poultry red mite, Dermanyssus gallinae

Abstract.  The behavioural responses of the poultry red mite, Dermanyssus gallinae , to three host-related stimuli, vibration, heat and CO₂, are studied in light and dark. Although D. gallinae usually feeds on host-blood at night, it can also be day active after a few days of starvation. However, the immediate response of the mites to CO₂ in daylight is to freeze and remain motionless. Even with simultaneous presentation of an activating stimulus (heat), the mites freeze in response to CO₂. In the case of subsequent vibrations, they start moving but only for the duration of the vibrations. After 2 min, the freezing response disappears and the level of activity is significantly higher than for mites stimulated with vibrations alone. The freezing response is interpreted as a defence against being eaten by the host that apparently is close enough to breathe on the mites. At low-light intensities, where the birds are unable to see the mites, there is no freezing response, but only a synergistic effect of heat and vibration on the level of activity. The frequency of vibration most efficient in eliciting movement during the freezing response is found at 2 kHz with a threshold value of 35 µm s⁻¹ peak-peak, suggesting that D. gallinae is more sensitive to substrate-borne vibrations than some insects (e.g. honeybees) known to use vibrations for intraspecific communication.     

Toxicity of plant essential oils to different life stages of the poultry red mite,Dermanyssus gallinae,and non‐target invertebrates

Seven essential oils with potential as acaricides for use against the poultry red mite, Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae), were selected for study. These products (essential oils of manuka, cade, pennyroyal, thyme, garlic, clove bud and cinnamon bark) were deployed against different life stages of D. gallinae in laboratory tests at the (lethal concentration) LC₅₀ level for adult mites. For all essential oils tested, toxicity to D. gallinae juveniles was as high as toxicity to adults, if not higher. However, at the LC₅₀ level determined for adults, some oils were ineffective in preventing hatching of D. gallinae eggs. The essential oils were also tested under laboratory conditions at their LC₉₀ levels for D. gallinae adults on two model non‐target species, the brine shrimp, Artemia salina (L.), and the mealworm beetle, Tenebrio molitor (L.). Results showed that not all essential oils were as toxic to A. salina and T. molitor as they were to D. gallinae, suggesting that it may be possible to select certain oils for development as acaricides against D. gallinae that would have minimal impact on non‐target organisms. However, the level of toxicity to A. salina and T. molitor was not consistent across the selected essential oils.     

The poultry red mite (Dermanyssus gallinae): a potential vector of pathogenic agents

The poultry red mite, D. gallinae has been involved in the transmission of many pathogenic agents, responsible for serious diseases both in animals and humans. Nowadays, few effective methods are available to control the ectoparasite in poultry farms. Consequently, this is an emerging problem which must be taken into account to maintain good health in commercial egg production. This paper addresses the vector capacity of the ectoparasite with special emphasis on salmonellae, pathogenic agents responsible for many of the most important outbreaks of food-borne diseases worlwide. It has been experimentally shown that D. gallinae could act as a biological vector of S. enteritidis and natural carriage of these bacteria by the mite on poultry premises has also been reported. It was also found that D. gallinae carried other pathogens such as E. coli, Shigella sp., and Staphylococcus, thus increasing the list of pathogenic agents potentially transmitted by the mite.     

Comparison of the VIDAS system, FTA filter-based PCR and culture on SM ID for detecting Salmonella in Dermanyssus gallinae

AIMS: To compare different analytical methods for detecting Salmonella in Dermanyssus gallinae. METHODS AND RESULTS: The detection limit of three Salmonella detection methods [Vitek immunodiagnostic assay (VIDAS) Salmonella immuno-concentration/immunoassay, FTA filter-based PCR, and Salmonella detection and identification medium (SM ID) preceded by a pre-enrichment step] was evaluated by crushing mites in serial dilutions of pure cultures of Salmonella enterica ssp. Enterica serotype Enteritidis. Each method was then compared for its ability to detect Salmonella in artificially contaminated mites. In 105 mites artificially engorged with Salm. Enteritidis-contaminated blood, Salmonella was isolated from 68 samples of the samples cultured on SM ID and tests were positive for Salmonella using FTA filter-based PCR and VIDAS in 77 and 65 samples, respectively. Using SM ID as our reference method, specificities and sensitivities were 97% and 94% and 73% and 98.5% for VIDAS and PCR, respectively. CONCLUSIONS: Each method allowed the detection of Salmonella in contaminated mites and is usable for screening mites. PCR is more sensitive but less specific than VIDAS for detecting Salmonella. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that the VIDAS has been used to detect pathogens in vectors. The development of analytical methods for Salmonella detection in mites is a necessary step in the study of the role of D. gallinae as a vector of salmonellae and to check the contamination of D. gallinae in poultry facilities.     

Circulation dynamics of Salmonella enterica subsp. enterica ser. Gallinarum biovar Gallinarum in a poultry farm infested by Dermanyssus gallinae

Dermanyssus gallinae (Mesostigmata: Dermanyssidae, De Geer, 1778) is an ectoparasite of poultry, suspected to play a role as a vector of Salmonella enterica subsp. enterica ser. Gallinarum. Despite an association between them being reported, the actual dynamics in field remain unclear. Therefore, the present study aimed to confirm the interactions among mites, pathogen and chickens. The study was carried out in an industrial poultry farm infested by D. gallinae, during an outbreak of fowl typhoid. The presence of S. Gallinarum in mites was assessed and quantified by a semi‐nested polymerase chain reaction (PCR) and real‐time PCR, respectively, in mites collected during two subsequent productive cycles and the sanitary break. The anti‐group D Salmonella antibodies were quantified by an enzyme‐linked immunosorbent assay. During the outbreak and the sanitary break, S. Gallinarum was constantly present in mites. In the second cycle, scattered positivity was observed, although hens did not exhibit signs of fowl typhoid, as a result of the vaccination with BIO‐VAC SGP695 (Fatro, Ozzano Emilia Bo, Italy). The data strongly suggest that D. gallinae acts as reservoir of S. Gallinarum, thus allowing the pathogen to persist in farms. Furthermore, the present study has highlighted the interactions among D. gallinae, S. Gallinarum and hens with respect to enhancing the mite‐mediated circulation of S. Gallinarum in an infested poultry farm.