Temporal changes in distribution, prevalence and intensity of northern fowl mite (Ornithonyssus sylviarum) parasitism in commercial caged laying hens, with a comprehensive economic analysis of parasite impact

Low levels of chicken body louse (Menacanthus stramineus) infestations affect chicken welfare in a cage-free housing system

BACKGROUND

The chicken body louse is an obligate ectoparasite of domestic chickens. Chicken body lice feed on feathers, and infestation with this louse is linked to decreases in egg production, hen weight, and feed conversion efficiency. However, it is unknown how chicken body lice impact egg-laying chickens in cage-free environments. Welfare and behavior metrics were collected from flocks of egg-laying chickens either infested with chicken body lice or left uninfested.

METHODS

In two trials, two flocks of cage-free commercial egg-laying chickens were infested with chicken body lice or maintained as uninfested controls. At three timepoints, behavior and welfare of all chickens was measured. On-animal sensors were used to quantify pecking, preening, and dustbathing behavior. Other animal-based welfare metrics included recording comb wounds and skin lesions.

RESULTS

Birds infested with chicken body lice exhibited significantly more preening behaviors than uninfested birds, even at low louse levels. Moderate or severe skin lesions were detected on birds that were moderately infested with chicken body lice while skin lesions were never detected on uninfested birds.

CONCLUSIONS

The welfare of chickens was impacted by the chicken body louse, a chewing louse that primarily feather feeds. Evidence of skin lesions on infested birds suggests that lice may cause more damage to birds than previously thought, and further evaluation of louse economic damage is necessary.

In Vivo Characterization of the Anti-Glutathione S-Transferase Antibody Using an In Vitro Mite Feeding Model

Poultry red mites (Dermanyssus gallinae, PRMs), tropical fowl mites (Ornithonyssus bursa, TFMs), and northern fowl mites (O. sylviarum, NFMs) are blood-feeding pests that debilitate poultry worldwide. Glutathione S-transferase (GST) plays an important role in the detoxification and drug metabolism of mites. However, research on avian mite GSTs as vaccine antigens is still lacking. Therefore, we aimed to evaluate the potential of avian mite GSTs for vaccine development. We identified GST genes from TFMs and NFMs. We prepared recombinant GST (rGST) from TFMs, NFMs, and PRMs, and assessed their protein functions. Moreover, we evaluated the cross-reactivity and acaricidal effect of immune plasma against each rGST on TFMs, NFMs, and PRMs. The deduced amino acid sequences of GSTs from TFMs and NFMs were 80% similar to those of the PRMs. The rGSTs exhibited catalytic activity in conjugating glutathione to the 1-chloro-2,4-dinitrobenzene substrate. Immune plasma against each rGST showed cross-reactivity with rGST from different mite species. Moreover, the survival rate of PRMs fed with immune plasma against the rGST of TFMs and NFMs was significantly lower than that of the control plasma. These results demonstrate the potential application of GST as an antigen for the development of a broad-spectrum vaccine against avian mites.

Advances in Non-Chemical Tools to Control Poultry Hematophagous Mites

The blood-sucking mites Dermanyssus gallinae ("red mite"), Ornithonyssus sylviarum ("northern fowl mite"), and Ornithonyssus bursa ("tropical fowl mite") stand out for causing infestations in commercial poultry farms worldwide, resulting in significant economic damage for producers. In addition to changes in production systems that include new concerns for animal welfare, global climate change in recent years has become a major challenge in the spread of ectoparasites around the world. This review includes information regarding the main form of controlling poultry mites through the use of commercially available chemicals. In addition, non-chemical measures against blood-sucking mites were discussed such as extracts and oils from plants and seeds, entomopathogenic fungi, semiochemicals, powder such as diatomaceous earth and silica-based products, and vaccine candidates. The control of poultry mites using chemical methods that are currently used to control or eliminate them are proving to be less effective as mites develop resistance. In contrast, the products based on plant oils and extracts, powders of plant origin, fungi, and new antigens aimed at developing transmission-blocking vaccines against poultry mites provide some encouraging options for the rational control of these ectoparasites.

Characterization of cysteine proteases from poultry red mite, tropical fowl mite, and northern fowl mite to assess the feasibility of developing a broadly efficacious vaccine against multiple mite species

Infestation with poultry red mites (PRM, Dermanyssus gallinae) causes anemia, reduced egg production, and death in serious cases, resulting in significant economic losses to the poultry industry. As a novel strategy for controlling PRMs, vaccine approaches have been focused upon and several candidate vaccine antigens against PRMs have been reported. Tropical (TFM, Ornithonyssus bursa) and northern (NFM, Ornithonyssus sylviarum) fowl mites are also hematophagous and cause poultry industry problems similar to those caused by PRM. Therefore, ideal antigens for anti-PRM vaccines are molecules that cross-react with TFMs and NFMs, producing pesticidal effects similar to those against PRMs. In this study, to investigate the potential feasibility of developing vaccines with broad efficacy across mite species, we identified and characterized cysteine proteases (CPs) of TFMs and NFMs, which were previously reported to be effective vaccine antigens of PRMs. The open reading frames of CPs from TFMs and NFMs had the same sequences, which was 73.0% similar to that of PRMs. Phylogenetic analysis revealed that the CPs of TFMs and NFMs clustered in the same clade as CPs of PRMs. To assess protein functionality, we generated recombinant peptidase domains of CPs (rCP-PDs), revealing all rCP-PDs showed CP-like activities. Importantly, the plasma obtained from chickens immunized with each rCP-PD cross-reacted with rCP-PDs of different mites. Finally, all immune plasma of rCP-PDs reduced the survival rate of PRMs, even when the plasma was collected from chickens immunized with rCP-PDs derived from TFM and NFM. Therefore, CP antigen is a promising, broadly efficacious vaccine candidate against different avian mites.

Diversity and Prevalence of Ectoparasites on Poultry from Open Environment Farms in the Western-United States of Washington, Idaho, Oregon, and California

Open-environment poultry farms that allow chickens to forage outdoors are becoming increasingly common throughout the United States and Europe; however, there is little information regarding the diversity and prevalence of ectoparasites in these farming systems. Eight to 25 birds were captured and surveyed for ectoparasites on each of 17 farms across the states of Washington, Idaho, Oregon, and California. Among the farms sampled, six louse species (Phthiraptera: Ischnocera & Amblycera) and two parasitic mite species (Acari: Mesostigmata) were collected and identified: Goniodes gigas (Taschenberg, 1879; Phthiraptera: Menoponidae) on one farm, Menacathus cornutus (Schömmer, 1913; Phthiraptera: Menoponidae) on one farm, Menopon gallinae (Linnaeus, 1758; Phthiraptera: Menoponidae) on six farms, Lipeurus caponis (Linnaeus, 1758; Phthiraptera: Philopteridae) on five farms, Menacanthus stramineus (Nitzsch, 1818; Phthiraptera: Menoponidae) on nine farms, Goniocotes gallinae De Geer (Phthiraptera: Philopteridae) on 11 farms, Dermanyssus gallinae (De Geer, 1778; Mesostigmata: Dermanyssidae) on two farms, and Ornithonyssus sylviarum (Canestrini & Fanzago, 1877; Mesostigmata: Macronyssidae) on one farm. The diversity of ectoparasites on these open environment poultry farms highlights a need for additional research on ectoparasite prevalence and intensity in these poultry farming systems.

Factors associated with prevalence and intensity of the northern fowl mite (Ornithonyssus sylviarum) in commercial poultry farms of Argentina

The haematophagous mite Ornithonyssus sylviarum may cause important economic losses in commercial poultry farms whilst also potentially affecting the health of farm workers. The dynamics of this ectoparasite has been linked to several factors, including wild birds, fomites, farm workers, management of hen houses, and host traits. Along two consecutive years, we carried out systematic sampling at three laying hen farms located in Santa Fe province, Argentina, with the aim of identifying factors that may influence O. sylviarum prevalence and intensity. We found that the density of feathers around the hen vent area and the presence of Menoponidae lice were negatively associated with mite abundance. We also found that the density of hens in the cages was negatively associated with mite prevalence, suggesting a possible dilution effect, whereas prior reports found a positive association with hen density. In addition, summer was the season with minimum mite prevalences and intensities, contrary to previous studies in northern farms where warm weather appeared to prompt an increase in mite populations. Another factor associated with mite intensity was age, but this effect varied depending on the season, which hints that the association between hen's age and mites is complex. Basic epidemiological knowledge on O. sylviarum in poultry farms from South America may aid in a more efficient and integrative approach to its control.

Epidemiologia e avaliação de risco associado à presença de ácaros hematófagos em galpões de granjas avícolas de postura

RESUMO Este estudo teve como objetivo caracterizar a epidemiologia da presença de ácaros hematófagos em granjas de postura no estado de Minas Gerais. Foi utilizado um banco de dados secundário, com informações de 402 galpões de 42 propriedades comerciais. As variáveis utilizadas para compor o modelo de correspondência foram selecionadas por meio do teste qui-quadrado (P≤0,05). Foi construído um índice para a presença de ácaros hematófagos, considerando alguns fatores de risco. Além disso, um estudo da análise espacial foi realizado para avaliar a presença de ácaros hematófagos em Minas Gerais. Observou-se a presença de ácaros hematófagos em 48% dos galpões, sendo a de O. sylviarum de 45,5%, O. bursa de 17,4% e D. gallinae de 2,7%. Houve associação entre o índice de risco com os intervalos de remoção de fezes e com a presença ou a ausência de aves sinantrópicas. Verificou-se que granjas mais tecnificadas não utilizam acaricida em seus galpões. A presença de ácaros hematófagos foi observada na mesorregião Sul/Sudoeste de Minas Gerais e entre as mesorregiões Oeste de Minas e Metropolitana de Belo Horizonte. Esses resultados fornecem conhecimento sobre a epidemiologia desses ectoparasitos e podem contribuir na tomada de decisões, reduzindo os riscos de possíveis infestações em aves de postura.

Collecting and Monitoring for Northern Fowl Mite (Acari: Macronyssidae) and Poultry Red Mite (Acari: Dermanyssidae) in Poultry Systems

The two most economically important poultry ectoparasites are the northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), and the poultry red mite, Dermanyssus gallinae (De Geer). Both mites are obligate blood feeders but differ in where they reside. Sampling methods thus focus on-host, especially the vent feathers, for northern fowl mite and off-host, especially cracks and crevices near the nighttime roosting areas, for poultry red mite. Much remains unknown, however, about the basic biology and ecology of both mites. Here we discuss mite detection, quantification, and decision making and provide thoughts on future directions for research.

Mesostigmatid mites (Acari: Mesostigmata) at the domestic-wildlife interface: Poultry and passerine birds of central Argentina

Wild birds may be considered a possible source of parasitic mesostigmatid mites for poultry, but only few studies explored this hypothesis. In addition, there is very little information about the parasitic mites present in commercial poultry systems from southern South America. To contribute with data on parasitic mesostigmatid mites at the domestic-wildlife interface, we conducted a study in which samples were systematically collected from laying hens and wild birds (adults and nestlings), for two years at three commercial laying hen farms. The occurrence of mesostigmatid mites were compared among hosts. A proportion of the collected mites were morphologically identified to the species level, finding that host preference varied greatly depending on mite species: laying hens were only parasitized by Ornithonyssus sylviarum, wild bird nestlings were mostly parasitized by Ornithonyssus bursa, and in small proportion, by O. sylviarum, while adult passerines were parasitized by both Ornithonyssus species, and sporadically by Pellonyssus cf. reedi and Dermanyssus cf. triscutatus. In laying hens, there was intra- and inter-annual variability in mite occurrence, but no consistent seasonal pattern, whereas in adult wild birds, mites showed the highest prevalence in spring and the lowest in summer. Not coinciding with this general pattern, the occurrence of O. bursa matched the reproductive activity of wild birds. A phylogenetic analysis based on a fragment of the 16S rRNA gene was carried out for a subsample of the mites collected, showing that the O. sylviarum mites present on adult wild birds and laying hens had the same haplotype (100% identity). Additionally, mites obtained from wild birds morphologically identified as O. bursa presented two distinctive haplotypes (89.8% identity), one phylogenetically related to O. sylviarum and the other to O. monteiroi. These findings show that in central Argentina commercial laying hens are parasitized mainly by O. sylviarum while wild birds are also hosts to other mite species. Adult wild passerines, especially house sparrows, may be a source of O. sylviarum for commercial poultry.

Parasitic mites alter chicken behaviour and negatively impact animal welfare

The northern fowl mite, Ornithonyssus sylviarum, is one of the most common and damaging ectoparasites of poultry. As an obligate blood feeding mite, the northern fowl mite can cause anaemia, slower growth, and decreased egg production of parasitized birds. However, the impact of mites or other ectoparasites on hen behaviour or welfare is not well studied. Here, we use activity sensors (three-axis accelerometers) affixed to individual birds to continuously record hen movement before, during, and after infestation with mites. Movements recorded by sensors were identified to specific bird behaviours through a previously trained algorithm, with frequency of these behaviours recorded for individual birds. Hen welfare was also determined before, during, and after mite infestation of hens using animal-based welfare metrics. Northern fowl mites significantly increased hen preening behaviour and resulted in increased skin lesions of infested birds.

Genetic Structure of Northern Fowl Mite (Mesostigmata: Macronyssidae) Populations Among Layer Chicken Flocks and Local House Sparrows (Passeriformes: Passeridae)

The northern fowl mite (NFM) Ornithonyssus sylviarum Canestrini and Fanzago is a blood-feeding ectoparasite found on many wild bird species and is a pest of poultry in the United States. It is unknown where NFM infestations of poultry originate, which has made it difficult to establish preventative biosecurity or effective control. We used microsatellite markers to evaluate genetic variation within and among NFM populations to determine routes of introduction onto farms and long-term persistence. We compared NFM from flocks of chickens (Gallus gallus) on different farms in California, Washington, and Georgia, and we compared NFM collected over a 5-yr interval. On three farms we collected NFM from chickens and house sparrows (Passer domesticus) nesting on each farm, which we used to assess movement between host species. There was strong genetic structure among mites from different poultry farms and low estimates of migration between farms. There were significant differences between mites on chickens and house sparrows on two farms where sparrows nested near flocks, indicating no exchange of mites. Only one farm showed evidence of NFM movement between chickens and sparrows. There was high genetic similarity between mites collected 5 yr apart on each of two farms, indicating that NFM infestations can persist for long periods. The genetic patterns did not reveal sources of NFM infestations on chicken farms. The data suggest that NFMs are strongly differentiated, which likely reflects periodic population declines with flock turnover and pesticide pressure.

Molecular characterization and genetic diversity of Ornithonyssus sylviarum in chickens (Gallus gallus) from Hainan Island, China

BACKGROUND

The northern fowl mite (NFM), Ornithonyssus sylviarum, is an obligatory hematophagous ectoparasite of birds and one of the most important pests in the poultry industry on several continents. Although NFM poses a serious problem, it remains a neglected pest of poultry in China and other Asian countries. Therefore, a molecular analysis was conducted to provide baseline information on the occurrence, genetic diversity and emergence of NFM in poultry farms from China.

METHODS

This study focused on morphological description and identification of adults based on electron microscopy, molecular sequencing of the mitochondrial cox1 gene and phylogenetic analysis. We have also used the DNA sequences of the cox1 gene to study the genetic diversity, population structure and demographic history. The neutrality tests were used to analyze signatures of historical demographic events.

RESULTS

The mites collected were identified as the northern fowl mite Ornithonyssus sylviarum based on external morphological characterization using electron microscopy. Molecular analysis using a 756-bp long partial fragment of the cox1 gene revealed 99-100% sequence identity with NFM and phylogenetic inferences showed a bootstrap value of 99% indicating a well-supported monophyletic relationship. Molecular diversity indices showed high levels of haplotype diversity dominated by private haplotypes, but low nucleotide divergence between haplotypes. The Tajima's D test and Fu's Fs test showed negative value, indicating deviations from neutrality and both suggested recent population expansion of mite populations supported by a star-like topology of the isolates in the network analysis. Our genetic data are consistent with a single introduction of NFM infestations and the spread of NFM infestation in Hainan poultry farms and a private haplotype dominance, which suggest that infestations are recycled within the farms and transmission routes are limited between farms.

CONCLUSIONS

To our knowledge, this is the first time a molecular report of NFM in chicken from China including other Asian countries using DNA barcoding. The findings have potential implications with respect to understanding the transmission patterns, emergence and populations trends of parasitic infestations of poultry farms that will help for setting the parameters for integrated pest management (IPM) tactics against mite infestations.

Resistance and tolerance to mixed nematode infections in relation to performance level in laying hens

Modern chickens have been genetically developed to perform high under optimal conditions. We hypothesized that high-performance is associated with a higher sensitivity to environmental challenges in laying hens. By using nematode infections as an environmental stressor, we assessed performance-level associated host responses in a high (i.e. Lohmann Brown Plus, LB) and in a lower performing, a so-called dual-purpose chicken genotype (i.e. Lohmann Dual, LD). The hens were infected with 1000 eggs of Ascaridia galli and Heterakis gallinarum at 24 weeks of age. Hen performance parameters, humoral immune responses in plasma and egg yolks and worm burdens were assessed at several occasions over a period of 18 weeks post infection (wpi). While infections had no significant effect on feed intake (P = 0.130) and body weight in both genotypes (P = 0.392), feed conversion efficiency was negatively affected by infections (P = 0.017). Infections reduced both laying rate and egg weight and thereby per capita egg mass in both genotypes (P < 0.05). While laying rate in infected LB hens decreased significantly (P < 0.05) in the early infection period (i.e. by 3 wpi), the decrease in LD hens appeared much later (i.e. by 14 wpi). Worm burdens resulting from the experimental infection were not different between the genotypes for both worm species (P > 0.05), whereas LB hens were more susceptible (P < 0.05) to re-infections than LD hens. Changes in humoral immune responses (i.e. ascarid-specific IgY antibodies in plasma and egg yolks) of the two genotypes over time reflected closely the corresponding changes in larval counts of the hens, descending from both experimental and subsequent natural infections in both genotypes. Infections caused a shift in egg size classes, leading to smaller frequency of larger eggs in both genotypes. Infections reduced egg weight (P = 0.018) and led to a reduced fat content in the egg yolks (P = 0.045). The proportion of poly-unsaturated fatty acids (PUFA), especially n-6-PUFA, was also lower in egg yolks of the infected hens (P = 0.032). We conclude that tolerance to nematode infections in laying hens is dependent on host-performance level. The impairment in host tolerance was both genotype and time dependent, likely due to differences in genetic programming for production peak and persistency of the two genotypes. The two genotypes exhibited similar levels of resistance after a fully controlled experimental infection, but the high performing hens were more susceptible to subsequent natural infections. Infections negatively affected economically important egg-quality traits, including egg weight, fat content and fatty acid profiles in egg yolks.

Haematophagous mites on poultry farms in the Republic of the Union of Myanmar

Haematophagous ectoparasites of poultry, such as Ornithonyssus sylviarum, northern fowl mites (NFMs), Dermanyssus gallinae, poultry red mites (PRMs), and Ornithonyssus bursa, tropical fowl mites (TFMs) are prevalent worldwide. Although poultry farming is a major industry in Southeast Asia, there are only a few reports concerning the prevalence of avian mites in this region. In this study, we sampled twenty farms in four major poultry farming areas in Myanmar. We detected the mites on six farms, and they showed morphological similarities to NFMs and TFMs. The nucleotide sequences of cytochrome c oxidase subunit I indicated that some mites were NFMs. This is the first report confirming the presence of NFMs and TFMs among the hematophagous mites infesting chickens on Myanmar poultry farms.

New species of parasitic nasal mites infesting birds in Manitoba, Canada (Mesostigmata, Rhinonyssidae)

Mites (Acari, Acariformes, Parasitiformes) are one of the most diverse and abundant groups of arthropods associated with birds. Several families of mites have colonised the respiratory tract of birds, the Rhinonyssidae (Mesostigmata) being the most diverse. There are 66 species of rhinonyssids (59 named, seven undescribed species) reported from Canadian birds. Two new species of rhinonyssids were discovered while surveying nasal mites from birds in Manitoba, Canada, and are herein described as Sternostomagallowayisp. n. from the horned lark (Eremophilaalpestris), and Vitznyssusericisp. n. from the common nighthawk (Chordeilesminor).

Essential oils: effects of application rate and modality on potential for combating northern fowl mite infestations

The northern fowl mite (NFM), Ornithonyssus sylviarum (Mesostigmata: Macronyssidae), is the primary blood-feeding ectoparasite found on poultry in the U.S.A. Three experiments were conducted in vitro to test the acaricidal properties of cade, garlic, lavender, lemongrass, pine and thyme essential oils against NFM, and to evaluate whether these effects are altered by adjusting oil application rates and application modality (direct vs. vapour contact). Applied at the rate of 0.21 mg/cm² , the essential oils of cade, thyme, lemongrass and garlic resulted in higher NFM mortality at 24 h post-application than lavender and pine oils, and the untreated and ethanol-treated controls. Cade and thyme were the most consistent and fast-acting of the essential oils in terms of toxicity to NFM. Cade applied at 0.21 mg/cm² and 0.11 mg/cm² and thyme applied at 0.21 mg/cm² were effective in eliminating NFM within 2 h through direct contact. The modality of application did not affect the efficacy of cade and thyme essential oils. The results suggest that essential oils may be utilized as alternatives to chemical pesticides and could be used as fumigants for the control of NFM.

Microclimate and host body condition influence mite population growth in a wild bird-ectoparasite system

Parasite populations are never evenly distributed among the hosts they infect. Avian nest ectoparasites, such as mites, are no exception, as their distribution across the landscape is highly aggregated. It remains unclear if this pattern is driven by differences in transmission events alone, or if the environment that parasites inhabit after transmission also plays a role. Here, we experimentally examined the influence of the post-transmission microclimate, nest characteristics, and host condition on ectoparasite population growth in a bird-ectoparasite system. We infested barn swallow (Hirundo rustica erythrogaster) nests with a standardized number of Northern Fowl Mites (Ornithonyssus sylvarium) and analyzed both biotic (nestling mass, wing length, number of other arthropods present in the nest, and brood size) and abiotic (temperature, humidity, nest lining, nest dimensions, and substrate upon which the nest was built) predictors of mite population growth. Our results suggest that mite populations were most successful, in terms of growth, in nests with higher temperatures, lower humidity, few other arthropods, and hosts in good condition. We also found that nests built on wooden substrates support larger populations of mites than those constructed on metal or concrete. These findings lend insight into the factors that drive large-scale patterns of ectoparasite distributions.

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Experimental manipulations of nest mites controls for initial transmission.

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Tested the role of microclimate and host factors on mite population growth.

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Mite populations grow larger in warmer, drier nests with high body condition hosts.

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Nests on wooden substrates had more stable microclimate and larger mite populations.

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Presence of other arthropods was negatively correlated with mite population growth.

Efficacy and safety assessment of a water-soluble formulation of fluralaner for treatment of natural Ornithonyssus sylviarum infestations in laying hens

Background

Northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago, 1877), infestations can stress birds, impairing welfare and causing substantial economic losses. A study was undertaken to determine the efficacy of an ectoparasiticide solution (fluralaner) for oral administration in the treatment of mite-infested hens.

Methods

Clinically healthy, naturally mite-infested laying hens (n = 132), approximately 32 weeks of age, were ranked by Day -9 mite vent counts and randomized among 12 study pens, each to hold one of four treatment groups. Three groups received fluralaner-medicated water by oral gavage at dose rates of 0.25, 0.5 or 1.0 mg/kg on Days 0 and 7; one group was an untreated control (three pens for each group). Five naturally infested untreated birds were included in each pen to act as mite-infested source birds. Thus each pen, treated and control, had six non-source birds for assessment of efficacy, plus five source birds to provide ongoing challenge. Primary efficacy assessments were based on mean O. sylviarum vent counts from non-source birds in the control and treated group pens on Days 1, 2, 6, 8, 12, 15, 19, 22 and 26.

Results

Source-birds maintained infestations throughout the study, validating the challenge to study birds. On Days 1 through 22, mean control group mite counts were significantly greater than those of the treated groups (P ≤ 0.013). Relative to the control group, mean O. sylviarum counts were reduced by at least 90% from Day 6 through Days 19, 22 and 22 in the fluralaner 0.25, 0.5 and 1.0 mg/kg groups, respectively. On Day 19, mean mite counts were lower in the 0.5 and 1.0 mg/kg groups compared with the 0.25 mg/kg group (P ≤ 0.018), and in the 1.0 mg/kg compared with the 0.5 mg/kg group (P = 0.014). There were no adverse events in treated birds.

Conclusions

A fluralaner solution administered twice by gavage to laying hens with a one-week between-treatment interval was safe and effective in quickly controlling O. sylviarum infestations despite continuous challenge from infested birds. By eliminating mites, this fluralaner solution has the potential to improve bird health and productivity, and to eliminate the burden of topical pesticide application.

A review of the biology, ecology, and control of the northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae)

The northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago, 1877), is found on several continents and has been a major pest of poultry in the United States for nearly a century. Lack of earlier USA reports in the United States suggests an introduction or change to pest status in domestic poultry systems occurred in the early 1900s. Though predominantly a nest-parasite of wild birds, this obligate hematophagous mite is a permanent ectoparasite on domestic birds, especially egg-laying chickens. Economic damage is incurred by direct blood feeding and activation of the of host's immune responses. This in turn causes decreased egg production and feed conversion efficiency, and severe infestations can cause anemia or death to birds. Here we review the biology, ecology, and recent control measures for the northern fowl mite. Photomicrographs are included of adult males and females, protonymphs, and larvae with key characters indicated. Special emphasis is placed on current knowledge gaps of basic and applied science importance.

Comparative in vitro evaluation of contact activity of fluralaner, spinosad, phoxim, propoxur, permethrin and deltamethrin against the northern fowl mite, Ornithonyssus sylviarum

Background

Northern fowl mites (Ornithonyssus sylviarum) are obligate hematophagous ectoparasites of both feral birds and poultry, particularly chicken layers and breeders. They complete their entire life-cycle on infested birds while feeding on blood. Infestations of O. sylviarum are difficult to control and resistance to some chemical classes of acaricides is a growing concern. The contact susceptibility of O. sylviarum to a new active ingredient, fluralaner, was evaluated, as well as other compounds representative of the main chemical classes commonly used to control poultry mite infestations in Europe and the USA.

Methods

Six acaricides (fluralaner, spinosad, phoxim, propoxur, permethrin, deltamethrin) were dissolved and serially diluted in butanol:olive oil (1:1) to obtain test solutions used for impregnation of filter paper packets. A carrier-only control was included. Thirty adult northern fowl mites, freshly collected from untreated host chickens, were inserted into each packet for continuous compound exposure. Mite mortality was assessed after incubation of the test packets for 48 h at 75% relative humidity and a temperature of 22 °C.

Results

Adult mite LC₅₀ /LC₉₉ values were 2.95/8.09 ppm for fluralaner, 1587/3123 ppm for spinosad, 420/750 ppm for phoxim and 86/181 ppm for propoxur. Permethrin and deltamethrin LC values could not be calculated due to lack of mortality observed even at 1000 ppm.

Conclusions

Northern fowl mites were highly sensitive to fluralaner after contact exposure. They were moderately sensitive to phoxim and propoxur, and less sensitive to spinosad. Furthermore, the tested mite population appeared to be resistant to the pyrethroids, permethrin and deltamethrin, despite not being exposed to acaricides for at least 10 years.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2289-z) contains supplementary material, which is available to authorized users.

Timing Diatomaceous Earth-Filled Dustbox Use for Management of Northern Fowl Mites (Acari: Macronyssidae) in Cage-Free Poultry Systems

Northern fowl mite management on conventionally caged birds relies on synthetic pesticide sprays to wet the vent. Cage-free chickens cannot be effectively treated this way, and pesticide use is restricted in organic production. Dustbathing behavior is encouraged in newer production systems for increased hen welfare. Diatomaceous earth (DE) is an approved organic insecticide that can be mixed with sand in dustboxes, suppressing mites but not excluding them, and potentially allowing development of mite immunity. We tested two hypotheses: 1) that DE-filled dustboxes placed before northern fowl mite introduction (prophylactic use) prevents mite populations from reaching economically damaging thresholds, and 2) that bird exposure to low mite numbers allows for protective hen immunity to develop and suppress mites after dustboxes are removed. We also tested if different beak trimming techniques (a commercial practice) affect mite growth. Mites were introduced to birds after dustboxes were made available. Average mite densities in flocks remained below damaging levels while dustboxes were available. Average mite populations rebounded after dustbox removal (even though DE persisted in the environment) regardless of the timing of removal. Mite densities on birds where a traditional hot-blade beak trimming technique was used (trial 1) were high. Mite densities in trial 2, where a newer precision infra-red trimming was used, were lower. The newer infra-red trimming method resulted in nearly intact beaks, which were better for mite control by bird grooming behaviors. The combination of early dustbox use and infra-red beak trimming should allow producers to avoid most mite damage in cage-free flocks.

Sulfur Dust Bag: A Novel Technique for Ectoparasite Control in Poultry Systems

Animal welfare-driven legislation and consumer demand are changing how laying chickens are housed, thus creating challenges for ectoparasite control. Hens housed in suspended wire cages (battery cages) are usually treated with high-pressure pesticides. This application type is difficult in enriched-cage or cage-free production. Alternatives to pesticide sprays are needed in enriched-cage or cage-free systems. In this study, we tested the efficacy of sulfur dust deployed in "dust bags" for control against the northern fowl mite (Ornithonyssus sylviarum), which causes host stress, decreased egg production, and reduced feed conversion efficiency. Dust bags were hung from the tops of cages or were clipped to the inside front of cages. We also tested permethrin-impregnated plastic strips, marketed for ectoparasite control in caged or cage-free commercial and backyard flocks. Previous work has shown sulfur to be very active against poultry ectoparasites; however, we found that the placement of bags was important for mite control. Sulfur in hanging bags reduced mites on treatment birds by 95 or 97% (depending on trial) within one week of being deployed, and mite counts on these birds were zero after 2 wk. Clipped sulfur bags acted more slowly and did not significantly reduce mites in one trial, but reduced mite counts to zero after 4 wk in trial 2. Permethrin strips had no effect on mite populations. This may have been due to mite resistance, even though this mite population had not been exposed to pyrethroids for several years. Sulfur bags should be effective in caged or cage-free systems.

Northern fowl mite (Ornithonyssus sylviarum) effects on metabolism, body temperatures, skin condition, and egg production as a function of hen MHC haplotype

The northern fowl mite, Ornithonyssus sylviarum, is the most damaging ectoparasite on egg-laying hens in the United States. One potential strategy for management is breeding for mite resistance. Genes of white leghorn chickens linked to the major histocompatibility complex (MHC) were previously identified as conferring more (B21 haplotype) or less (B15 haplotype) mite resistance. However, immune responses can be energetically costly to the host and affect the economic damage incurred from mite infestations. We tested energy costs (resting metabolic rate) of mite infestations on egg-laying birds of both MHC B-haplotypes. Resting metabolic rates were documented before (pre-) mite infestation, during (mid-) infestation, and after peak (late) mite infestation. Mite scores, economic parameters (egg production, feed consumption), and physiological aspects such as skin inflammation and skin temperature were recorded weekly. Across experiments and different infestation time points, resting metabolic rates generally were not affected by mite infestation or haplotype, although there were instances of lower metabolic rates in infested versus control hens. Skin temperatures were recorded both at the site of mite feeding damage (vent) and under the wing (no mites), which possibly would reflect a systemic fever response. Ambient temperatures modified skin surface temperature, which generally was not affected by mites or haplotype. Feed conversion efficiency was significantly worse (4.9 to 17.0% depending on trial) in birds infested with mites. Overall egg production and average egg weight were not affected significantly, although there was a trend toward reduced egg production (2 to 8%) by infested hens. The MHC haplotype significantly affected vent skin inflammation. Birds with the mite-resistant B21 haplotype showed earlier onset of inflammation, but a reduced overall area of inflammation compared to mite-susceptible B15 birds. No significant differences in resting energy expenditure related to mite infestation or immune responses were detected. Potential breeding for resistance to mite infestation using these two haplotypes appears to be neutral in terms of impact on hen energy costs or production efficiency, and may be an attractive option for future mite control.

Diversity and Prevalence of Ectoparasites on Backyard Chicken Flocks in California

Peridomestic ("backyard") chicken flocks are gaining popularity in the developed world (e.g., North America or Europe), yet little is known regarding prevalence or severity of their ectoparasites. Therefore, five birds on each of 20 properties throughout southern California were surveyed in summer for on-host (permanent) and off-host dwelling (temporary) ectoparasites. Only four premises (20%) were entirely free of ectoparasites. In declining order of prevalence (% of premises), permanent ectoparasites included six chicken louse species: Menacanthus stramineus (Nitzsch) (50%), Goniocotes gallinae (De Geer) (35%), Lipeurus caponis (L.) (20%), Menopon gallinae (L.) (15%), Menacanthus cornutus (Schömmer) (5%), and Cuclotogaster heterographus (Nitzsch) (5%). Only one flea species, Echidnophaga gallinacea (Westwood) (20%), was found. Three parasitic mite species were observed: Ornithonyssus sylviarum (Canestrini & Fanzago) (15%), Knemidocoptes mutans (Robin & Lanquetin) (10%), and Dermanyssus gallinae (De Geer) (5%). Many infestations consisted of a few to a dozen individuals per bird, but M. stramineus, G. gallinae, M. cornutus, and E. gallinacea were abundant (dozens to hundreds of individuals) on some birds, and damage by K. mutans was severe on two premises. Off-host dwelling ectoparasites were rare (D. gallinae) or absent (Cimex lectularius L., Argasidae). Parasite diversity in peridomestic flocks greatly exceeds that is routinely observed on commercial chicken flocks and highlights a need for increased biosecurity and development of ectoparasite control options for homeowners.

Temperature governs on-host distribution of the northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae)

The northern fowl mite, Ornithonyssus sylviarum (Canestri & Fanzago), is an ectoparasite of more than 70 species of North American wild birds, but it has a particularly significant impact on chickens, where it is a permanent resident of vent feathers. Improved control practices depend on a better understanding of host-mite relationships. ISA Brown hens were inoculated experimentally with northern fowl mite adults, and northern fowl mite populations developed naturally. Using a fast-response microprobe, temperatures of individual vent feathers (n = 15) were recorded at 5-mm increments along the length of the feather shaft. Immediately after temperatures were recorded, the individual feathers were quickly clipped at the skin surface and then flash-frozen between 2 small blocks of dry ice, freezing all northern fowl mite stages in situ. The feathers then were cut into 5-mm sections for careful mite enumeration by life stage. There were no overall differences among life stages in the distributions on the feather. Mite positions on feathers (distance from skin) varied distinctly with feather zone temperatures, as well as with ambient and average temperatures over the prior 24 hr. Ambient temperature at time of sampling affected the positions of the 2 mobile categories, adults and larvae/nymphs, but showed no statistical relationship with egg distribution. In contrast, ambient 24-hr temperature influenced the positions of all life stages. On-host feather temperatures reflected ambient temperatures. Feathers collected on hot days (ambient temperatures of 23-33 C) provided a narrow and quite warm range of temperature conditions for mites (often >30-36 C). Temperatures on cool days (ambient temperatures of <23 C) provided much wider on-host temperature ranges for mites to occupy (13-35 C). Mites were farther from the skin on warmer days. When mites had a broad range of temperatures, the feather temperature zone occupied by all life stages averaged 28-29 C. Mites move to occupy favorable temperature conditions on-host. When further out on feathers in warm weather, and under thermal stress, northern fowl mites either move off host or are dislodged. They then become a human pest, are noticed by farmers, and are more likely to disperse.

Arrhenotoky and oedipal mating in the northern fowl mite (Ornithonyssus sylviarum) (Acari: Gamasida: Macronyssidae)

Background

The northern fowl mite (NFM; Ornithonyssus sylviarum) is a blood-feeding ectoparasite of birds and a major pest of poultry in the United States. Mite populations spread rapidly in commercial flocks, reach peak burdens of >70,000 mites per bird and have developed resistance to many pesticides. Despite decades as a pest in the United States, the reproductive biology of NFM remains unclear. Based on karyotypes, the NFM has haplodiploid sex determination, which suggests unmated females could produce male offspring (arrhenotoky). Thus, unmated females could disseminate to a new host and initiate an infestation by producing and mating with sons (oedipal mating).

Methods

We used small capsules to isolate and recover NFM on host chickens. Mites in capsules could blood feed, develop and reproduce, but could not contact other mites. Individual larvae were matured in isolation to produce known, unmated females. We evaluated reproduction of (I) previously mated females (i) in isolation, or (ii) paired with a male, and (II) unmated (virgin) females in isolation. In each treatment we recorded the number and sexes of offspring produced over time.

Results

Mated NFM produced female and male offspring in isolation, or when paired with a male. When paired with a male, females produced a female-biased sex ratio of the offspring (F:M ratio ~5:1). Unmated, female NFM produced exclusively male offspring when in isolation. When paired with their sons that had developed to maturity, the "virgin" females were able to mate and subsequently produce female offspring.

Conclusions

This study found that females with immediate access to sperm produced mostly female offspring. Virgin female NFM initially produced only male offspring and subsequently used oedipal mating to produce female offspring. Using this reproductive system NFM could successfully colonize new hosts as immature, or unmated females. The strong female-biased sex ratio of NFM populations suggests a large proportion of the parasite population is capable of disseminating to new hosts, which is essential for an obligate parasite to persist.

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

Hen housing (cage or cage-free) did not impact overall abundances of northern fowl mites, Ornithonyssus sylviarum (Canestrini & Fanzago) (Acari: Macronyssidae), or chicken body lice, Menacanthus stramineus (Nitzsch) (Phthiraptera: Menoponidae). Cage-free hens received a dustbox with sand plus diatomaceous earth (DE), kaolin clay or sulphur. Weekly use varied from none to 100% of hens; 73% of hens used the dustbox at least once. Ectoparasite populations on dustbathing hens (users) were compared with those on non-user cage-free and caged hens. All materials reduced ectoparasites on user hens by 80-100% after 1 week of dustbox use. Diatomaceous earth and kaolin failed to reduce ectoparasites on non-user hens, and ectoparasites on user hens recovered after dustbox removal. A sulphur dustbox eliminated mites from all hens (including non-users) within 2-4 weeks. Residual sulphur controlled mites until the end of the experiment (up to 9 weeks), even after the dustbox was removed. Louse populations on hens using the sulphur dustbox were reduced in 1-2 weeks. Residual sulphur effects were less evident in lice, but the use of a sulphur dustbox by a higher proportion of hens extended louse control to all hens. This is the first experimental study to show that bird dustbathing in naturally and widely available dust materials (particularly kaolin) can suppress ectoparasites and thus the behaviour is probably adaptive.

Beak condition drives abundance and grooming-mediated competitive asymmetry in a poultry ectoparasite community

OBJECTIVE

Ornithonyssus sylviarum (northern fowl mite) and Menacanthus stramineus (chicken body louse) are key poultry pests currently controlled by exclusion or pesticide application. We studied how host beak condition affected their populations over time and how the lice and mites might interact on a host.

METHODS

Beak-trimmed or beak-intact white leghorn hens were infested initially with either mites or lice and subsequently challenged using the alternate ectoparasite species (reciprocal transfer), while other hens harboured only the initial ectoparasite species.

RESULTS

Beak-trimmed hens had far higher ectoparasite numbers relative to beak-intact hens, and the 2 ectoparasites showed evidence of grooming-mediated competitive asymmetry. On beak-trimmed hens, larger numbers of lice quickly nearly completely excluded mites in competition for enemy-free space (lower abdomen), while in the reciprocal transfer mites did not affect louse numbers on beak-trimmed hosts. The 2 ectoparasites co-existed on beak-intact hens, which were better able to defend the lower abdomen habitat by grooming.

CONCLUSION

Lice are somewhat less damaging and much easier to control relative to mites, and might be used to eliminate mites in commercial, beak-trimmed flocks. Beak trimming impairs host grooming and contributes greatly to the high ectoparasite populations seen in commercial flocks. The study adds incentives for poultry breeders to develop more docile hen strains that can be held without beak trimming. This has advantages both to welfare advocates and producers who may no longer need to use insecticides for pest control or be concerned about worker exposure to pesticides.

Hen welfare in different housing systems

Egg production systems have become subject to heightened levels of scrutiny. Multiple factors such as disease, skeletal and foot health, pest and parasite load, behavior, stress, affective states, nutrition, and genetics influence the level of welfare hens experience. Although the need to evaluate the influence of these factors on welfare is recognized, research is still in the early stages. We compared conventional cages, furnished cages, noncage systems, and outdoor systems. Specific attributes of each system are shown to affect welfare, and systems that have similar attributes are affected similarly. For instance, environments in which hens are exposed to litter and soil, such as noncage and outdoor systems, provide a greater opportunity for disease and parasites. The more complex the environment, the more difficult it is to clean, and the larger the group size, the more easily disease and parasites are able to spread. Environments such as conventional cages, which limit movement, can lead to osteoporosis, but environments that have increased complexity, such as noncage systems, expose hens to an increased incidence of bone fractures. More space allows for hens to perform a greater repertoire of behaviors, although some deleterious behaviors such as cannibalism and piling, which results in smothering, can occur in large groups. Less is understood about the stress that each system imposes on the hen, but it appears that each system has its unique challenges. Selective breeding for desired traits such as improved bone strength and decreased feather pecking and cannibalism may help to improve welfare. It appears that no single housing system is ideal from a hen welfare perspective. Although environmental complexity increases behavioral opportunities, it also introduces difficulties in terms of disease and pest control. In addition, environmental complexity can create opportunities for the hens to express behaviors that may be detrimental to their welfare. As a result, any attempt to evaluate the sustainability of a switch to an alternative housing system requires careful consideration of the merits and shortcomings of each housing system.

Responses of Ornithonyssus sylviarum (Acari: Macronyssidae) and Menacanthus stramineus (Phthiraptera: Menoponidae) to gradients of temperature, light, and humidity, with comments on microhabitat selection on chickens

Responses of the northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini & Fanzago) (Acari: Macronyssidae), and the chicken body louse (CBL), Menacanthus stramineus (Nitzsch) (Phthiraptera: Menoponidae), to variation in temperature, light, and humidity were assessed in bioassays. The location on a continuous thermal gradient at which each ectoparasite arrested was recorded and analyzed. NFM adults arrested at an average temperature of 30.09 +/- 0.34 degrees C. Adult CBL and first-instar CBL nymphs arrested at 33.69 +/- 0.20 degrees C and 34.99 +/- 0.26 degrees C, respectively. Groups of each ectoparasite were placed into clear glass vials (n = 10/vial) with one half shaded, and vials were exposed to three light levels, as follows: high (200 micromolm(-2)s(-1)), low (4 micromolm(-2)s(-1)), and nearly no light (0 micromolm(-2)s(-1)). The vial cap edges provided an opportunity to assess the interactive effect of light with harborage. NFM avoided light and sought harborage. In low light, the harborage preference overrode the tendency to avoid light. CBL avoided the harborage and showed a minimal preference for light. A four-level humidity gradient was established in two separate experimental arenas for NFM and CBL. Trials were run in ambient light (4 micromolm(-2)s(-1)) for the NFM and in nearly no light for the CBL. The NFM gradient used 38 +/- 2%, 54 +/- 7%, 73 +/- 3%, and 90 +/- 4% RH, whereas the CBL gradient used 42 +/- 5%, 48 +/- 7%, 63 +/- 4%, and 73 +/- 5% RH. NFM showed no humidity response in the walking bioassay, but the CBL settled at the lowest humidity level. Temperature and humidity on different hen body regions were related to the bioassay results and observed on-host ectoparasite distributions.

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

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.

Host inflammatory response governs fitness in an avian ectoparasite, the northern fowl mite (Ornithonyssus sylviarum)

Vertebrate immune responses to ectoparasites influence pathogen transmission and host fitness costs. Few studies have characterized natural immune responses to ectoparasites and resultant fitness effects on the ectoparasite. These are critical gaps in understanding vertebrate-ectoparasite interaction, disease ecology and host-parasite co-adaptation. This study focused on an ectoparasite of birds--the northern fowl mite (NFM) (Ornithonyssus sylviarum). Based on prior evidence that chickens develop resistance to NFM, these experiments tested two hypotheses: (i) skin inflammation blocks mite access to blood,impairing development, reproduction and survival; and (ii) host immunogenetic variation influences the inflammatory response and subsequent effects on the ectoparasite. On infested hosts, histology of skin inflammation revealed increased epidermal cell number and size, immigration of leukocytes and deposition of serous exudates on the skin surface. Survival of adult mites and their offspring decreased as the area of skin inflammation increased during an infestation. Inflammation increased the distance to blood vessels beyond the length of mite mouthparts (100-160 lm) and prevented protonymphs and adults from reaching a blood source. Consequently, protonymphs could not complete development, evidenced by a significant inverse relationship between inflammation and protonymph feeding success, as well as an increasing protonymph/adult ratio. Adult females were unable to feed and reproduce, indicated by an inverse relationship between inflammation and egg production, and decreasing female/juvenile ratio. These combined impacts of host inflammation reversed NFM population growth. Intensity of inflammation was influenced by the genotype of the major histocompatibility complex(MHC), supporting previous research that linked these immunological loci with NFM resistance. Overall, these data provide a model for a mechanism of avian resistance to an ectoparasitic arthropod and the fitness costs to the parasite of that host defense.

MHC haplotype involvement in avian resistance to an ectoparasite

Research on immune function in evolutionary ecology has frequently focused on avian ectoparasites (e.g., mites and lice). However, host immunogenetics involved with bird resistance to ectoparasites has not been determined. The critical role of the major histocompatibility complex (MHC) in adaptive immunity and high genetic variation found within the MHC make this gene complex useful for exploring the immunogenetic basis for bird resistance to ectoparasites. The objective of this study was to determine if the avian MHC influenced resistance to a blood-feeding ectoparasite. Four congenic lines of chickens, differing only at the MHC, were comparatively infested with a cosmopolitan ectoparasite of birds-northern fowl mite (NFM)-which is also a serious pest species of poultry. Mite infestations were monitored over time and mite densities (weekly and maximum) were compared among lines. Chickens with the MHC haplotype B21 were relatively resistant to NFM, compared with birds in the B15 congenic line (P < 0.02). To test for similar effects in an outbred genetic background, a separate experiment was performed with 107 commercial chickens (white leghorn, W-36 strain) infested with NFM. Hens were genotyped using a MHC microsatellite marker (LEI0258) and associations between MHC haplotype and NFM density were tested. The highest peak NFM populations occurred more often on hens with the B15 haplotype versus the B21 haplotype (P = 0.012), which supported the results of the congenic study. These data indicate the avian MHC influences ectoparasite resistance, which is relevant to disease ecology and avian-ectoparasite interaction.