Advances in Non-Chemical Tools to Control Poultry Hematophagous Mites

Simple Summary The mites that infest laying hens and broiler chickens in poultry farms have caused great inconvenience to the industry due to the difficulty of controlling or eliminating their populations within the production systems. Dermanyssus gallinae and Ornithonyssus spp. are the mites that mainly interfere with the health of the poultry, damaging the production and quality of the end product, with special emphasis on Ornithonyssus sylviarum and Ornithonyssus bursa. The objective of this article is to analyze the impact of hematophagous mites that infest commercial egg and meat production systems and the consequences of this form of parasitism, and discuss the chemical and non-chemical methods of control associated with the use of plants, entomopathogenic fungi, and products based on diatomaceous earth and synthetic silica, and new lines of research aimed at developing vaccines as a new way of controlling these pests. Abstract 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.


Introduction
According to the United Nation's Food and Agriculture Organization (FAO), the growth in the global poultry sector is driven by a greater demand and purchasing power of the consumer market.Egg production has increased considerably in the past three decades, increasing from 15 million tons in 1961 to 87 million tons in 2020, and chicken meat production increased from 9 million tons in 1961 to 133 million 2020 [1].The countries with significant numbers associated with chicken production are the United States, China, Brazil, and the European Union [2].Brazil exports the most chicken meat to the world [3].China stands out as the largest egg producer, followed by the United States, the European Union, India, and Mexico, with Brazil currently in sixth place [2][3][4].
Dermanyssus gallinae spends its life cycle hiding in nests, cracks, and crevices and feeds on its host at night.In contrast, Ornithonyssus sp.spends its entire cycle on a host, located in the feathers and down around the cloaca region.In cases of severe infestations, Ornithonyssus sp. can be found throughout the environment [11][12][13].The mites are transmitted through direct physical contact between animals, through indirect contact with instruments, cages, and materials infested with the mites, and through wild birds that frequent the laying hens and broilers houses [9,14,15].These mites can also bite humans, causing ectoparasitic dermatitis [8,16,17].
The elimination or control of these mites has become increasingly difficult due to their resistance to the chemical products available on the market [6,7,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] combined with a change in the system of raising animals in battery cages to that of enriched cages or "cage free" systems that make it difficult to control and observe the animals as they start to live free in sheds and roam freely in pastures [33][34][35].Due to this scenario, new technologies to control the hematophagous mites without the use of chemical acaricides are needed, such as plant-derived products, entomopathogenic fungi, diatomaceous and silica-based products, semiochemicals, and vaccines.Therefore, this review aimed to compile information regarding D. gallinae, O. sylviarum, and O. bursa, including geographic distribution and the biotechnological advances in the development of new tools against these mites using non-chemical repellent substances.

Materials and Methods
The data involving the geographic distribution and importance of hematophagous mites as well as chemical control and new technological trends (plant-derived products, entomopathogenic fungi, diatomaceous earth, volatile organic compounds (VOCs), and vaccines) to control them were assessed using the PubMed platform (https://pubmed.ncbi.nlm.nih.gov/.Access from December 2022 to June 2023) and Medical Subject Headings (MeSH terms).Additional information was searched in the Google Scholar database and government websites with data published on the subject.The information was then grouped according to the subject for further analyses: (a) bird mites, (b) poultry mite control methods, (c) biological control of poultry mites, (d) chemical control of poultry mites, and (e) vaccines against poultry mites.The information recovery was used to assess the following: (a) the forms of control that have been currently used against mites present in poultry production farms, (b) the impact caused by infestations of poultry mites, (c) the impact of mite infestation on animal and human health, and (d) the effectiveness of the current control methods and the new perspectives and technologies used or suggested for the control of avian mites.
The review procedure was outlined in topics to maintain the linearity of the information.These topics encompass the following: (a) the mites' geographically distribution and economic importance in poultry production, (b) the main forms of control that have been used against bird mites and their implications, and (c) new perspectives that have been developed and studied by different research groups that target effective ways to induce mortality or repellency in poultry hematophagous mites.

Mites' Distribution and Their Economic Impact on the Poultry Production System
Hematophagous mites are distributed worldwide and found in poultry farms in various countries (Figure 1).D. gallinae is considered the most prevalent mite in poultry farms around the world, with emphasis on European breeding models [29,[36][37][38].It is estimated that approximately 83% of European laying, pullet, and breeder farms, are infested with D. gallinae [39][40][41] with losses ranging between USD 130 million and USD 231 million per year [17,22,31,[42][43][44][45].all the maintenance costs of the farms.In addition, O. bursa is described as the mite primarily responsible for causing infestations and dermatitis in humans [52,64].The current management of poultry farms for egg production underscores the need to establish new practices related to preventive hygiene [69].This may be related to the fact that these types of poultry farms are systems where poultry remain for a long period of time [41,70].It is important to emphasize that raising poultry with systems with a high animal density presents an additional challenge when it comes to controlling poultry hematophagous mites [6,9,11,12,28,71,72].
In the intensive meat production systems, the chickens remain on the farm for 40-50 days [73], and following their slaughter, the environment and all materials and instruments are thoroughly cleaned and sanitized.The short amount of time that the animals remain in the environment, combined with constant cleaning of the facilities and sanitizing of the areas, does not allow mites to reach concentrations to be considered as an infestation: >100,000 mites/poultry for O. sylviarum [25,38] and 500,000 mites/poultry for D. gallinae [8,39].
Discussions on animal welfare have gained prominence in recent years.The physical spaces in which the animals are kept do not allow them to express their natural behavior [35,38,[74][75][76] and consequently impair their health and performance [35,70,76].Since 2012, the practice of poultry farming in battery cages has been banned in the European Union for ethical reasons and is being replaced by enriched cage systems or "cage free" systems, where animals remain confined, but not in cages [40,41,66,67,[77][78][79].This system makes it difficult to clean the environment, allowing the accumulation of organic matter and creating an ideal environment [66] for mites, such as D. gallinae [11], which is reflected in the increase in infestation problems in commercial poultry farms in all of Europe [40].In addition to affecting laying hen farms, the poultry red mite (PRM) is cosmopolitan in range, being able to infest other animals and humans, leading to intensely itchy dermatitis [6,7,37,46] with a zoonotic character [40,[46][47][48] and acts as a transmitter vector of disease-causing pathogens [6,22,30,40,44,46,[49][50][51][52][53][54].
According to Spagarano (2009), the cost of losses due to preventive and control measures against D. gallinae are difficult to calculate.The cost in France has been estimated at EUR 4.33/100 poultry and EUR 3.83/100 poultry for cages; in the Netherlands, it ranges from EUR 0.14/poultry to EUR 0.29/poultry [41,49] with productivity losses reaching EUR 0.57 to EUR 2.50 per poultry in one year [62].
After a severe infestation by hematophagous mites, the poultry becomes anemic, develops dermatitis, exhibits pecking behavior and plucks their feathers, and suffers skin wounds and secondary infections [12,28,38,67].Poultry infested with O. sylviarum also lose weight and have a lower feed conversion ratio, while in laying hens, there is a reduction in egg production and its quality (shell thickness, egg specific gravity, egg weight, and yolk color), resulting in a decrease in the Haugh unit (a measurement of egg protein quality) [13,26].
In a study conducted on a commercial egg farm to evaluate the impact of O. sylviarum infestations, Mullens et al. [25] observed a reduction of up to 4% in egg production, along with a reduction in feed conversion and in egg weight of around 0.5% to 2.2%, resulting in estimated losses of 0.70 to 0.10 euros per animal.These numbers, when multiplied by the number of animals from intensive systems, reveal huge losses when associated with all the maintenance costs of the farms.In addition, O. bursa is described as the mite primarily responsible for causing infestations and dermatitis in humans [52,64].
The current management of poultry farms for egg production underscores the need to establish new practices related to preventive hygiene [69].This may be related to the fact that these types of poultry farms are systems where poultry remain for a long period of time [41,70].It is important to emphasize that raising poultry with systems with a high animal density presents an additional challenge when it comes to controlling poultry hematophagous mites [6,9,11,12,28,71,72].
In the intensive meat production systems, the chickens remain on the farm for 40-50 days [73], and following their slaughter, the environment and all materials and instruments are thoroughly cleaned and sanitized.The short amount of time that the animals remain in the environment, combined with constant cleaning of the facilities and sanitizing of the areas, does not allow mites to reach concentrations to be considered as an infestation: >100,000 mites/poultry for O. sylviarum [25,38] and 500,000 mites/poultry for D. gallinae [8,39].
Discussions on animal welfare have gained prominence in recent years.The physical spaces in which the animals are kept do not allow them to express their natural behavior [35,38,[74][75][76] and consequently impair their health and performance [35,70,76].Since 2012, the practice of poultry farming in battery cages has been banned in the European Union for ethical reasons and is being replaced by enriched cage systems or "cage free" systems, where animals remain confined, but not in cages [40,41,66,67,[77][78][79].This system makes it difficult to clean the environment, allowing the accumulation of organic matter and creating an ideal environment [66] for mites, such as D. gallinae [11], which is reflected in the increase in infestation problems in commercial poultry farms in all of Europe [40].
In addition to changes in production systems, global climate changes in recent years have become a key factor in spreading ectoparasites around the world [80,81], accelerating the development of hemoparasites within the vectors [82].In general, PRM live well in temperatures ranging from 25 • C to 35 • C and relative humidity from 60% to 80%, so the rise in temperature, combined with changes in wind and rain, contribute to the increased dispersion of mites [83].The cross-transmission of mites between commercial poultry and wild birds is considered responsible for the dissemination and distribution of the PRM and Ornithonyssus spp.[6,50,67].
Unfortunately, although these acaricides can be sprayed into the environment, they do not reach some areas, such as crevices, or pass through feathers of the poultry, thus preventing mites from coming into contact with the chemical compounds [31,53,85].However, the most recent molecule, isoxazoline, can be administered through drinking water [4].
The use of chemicals generates inconvenience for the poultry production industry since most of them are (i) highly toxic, becoming a risk to both the animals and humans; (ii) highly polluting to the environment, leaving residue in water and soil; and (iii) can expose consumers to contaminated eggs and meat [6,7,51,53].
Furthermore, one of the main concerns in using acaricides is the selection of resistant mite populations [7,51,53,86].These products are used indiscriminately and many producers ignore the legal restrictions in their countries [7,9,19,84], and many of the active compounds are banned in Europe and/or in EU member states [19,50].* Result considering higher dose and after the end of the last treatment dose; # 100% mortality dilution of mites.The numbers 1,2,3,4,5,6 correspond to product, chemical class, test environment, and mortality.
Fipronil is forbidden to be used in animal used as food [19].Products belonging to the class of carbamates, organophosphates, and pyrethroids have been banned in the EU for use against D. gallinae.The Phoxim is the only veterinary drug registered for the treatment of D. gallinae infestations.However, it is not available in all EU countries [49,62].Moreover, Fluralaner has been widely used to combat ectoparasites, and its use against D. gallinae was approved in the EU, but in a restricted way, leading to many producers to resort to and rely on unlicensed chemicals [19].
There is a growing tendency to restrict the use of chemicals, especially in food production systems, to avoid food contamination, exposing workers to potentially harmful substances [19].

Non-Chemical Measures against Blood-Sucking Mites
Extracts and oils from plants and seeds, entomopathogenic fungi, semiochemicals, powder such as diatomaceous earth and silica-based products, and vaccines show promising results and could be investigated as alternatives in addition to being safer methods [22,27,28,53].Better ways of applying these methods need to be tested in the field, and they could be a part of an integrated management plan that would reduce the use of chemical acaricides [66].

Plant-Derived Compounds
Isolated compounds of plant extracts and essential oils are being studied as possible weapons to be used to combat mites on commercial farms [7,53,91,92].Some products can be sprayed or administered through contact impregnation in traps (Table 2).These compounds cause mortality or repellence [54].However, few field assays have been developed.Plant-based products are a promising method because they do not contaminate the environment and can be controlled in doses that do not cause health problems in animals and humans and do not leave residues in food products [6,7,27,51,53].
Under laboratory conditions in which almost all contact between mites and plantderived oils and extracts is guaranteed, it was possible to obtain mortality rates above 80%, demonstrating the effectiveness of the products [10,23,54,77,97,99,100].
Lundh et al. [94] and Abdel-Ghaffar et al. [1] obtained good efficacy in tests conducted in the field on laying farms using oil and vegetable extracts impregnated in traps.However, for the oil or extract to have an effect on the mite, it needs to come into contact with the product and its effectiveness when used in a trap is limited to captured mites [94].When used as a spray, it is necessary to develop new methods that ensure the dispersion and maintenance of the product in the environment and in animals for a longer period of time [54], in addition to avoiding the formation of oil films [85].

Entomopathogenic Fungi
These fungi occur naturally in the environment, and as a mechanism of action, they germinate and penetrate the body of arthropods through the cuticle causing paralysis of essential organs resulting in the host's death [7].Entomopathogenic fungi are being studied as a tool for use in the control of mites on commercial farms for egg production through spraying in or impregnating traps [7,51,53,85] (Table 3).
It has been demonstrated good results when using entomopathogenic fungi, mainly under laboratory conditions, to control the mite population [51,53,54].The efficiency of using these fungi to combat bird mites in the field may face some challenges, such as the capacity for fungus proliferation in an uncontrolled risks to animal and human health and does not leave any residue in the end products [7,51,53].

Diatomaceous Earth and Synthetic Silica-Based Products
Both diatomaceous earth (DE) and silica-based products are wettable or in the form of a dry powder that acts on mites with acaricidal efficacy.Their main ingredient, silicon dioxide (SiO 2 ), adheres to the mite's body and immobilizes it leading to desiccation and death [50,102] (Table 4).The authors described general toxic effect on the mites without any association with the system affected.The numbers 1,2,3,4,5,6 correspond to product, chemical class, and mortality.
The mite remains inside crevices, in organic materials, protected from contact with the products sprayed in the environment [7,53,102].Ulrich and Han [103] obtained good mortality results against D. gallinae with products based on diatomaceous earth under laboratory conditions, but did not obtain significant results when using the same products in field tests, which may have been influenced by the physical properties of the products [103], ambient humidity [78], or changes in climate that did not allow the mites to absorb the products [103].The numbers 1,2 correspond to product, chemical class, and mortality.
Although the method does not pose a risk of intoxication [102], silica varies in purity and size, threatening user and animal safety because it irritates the respiratory tract when inhaled [49,62,104].

Semiochemicals
Hematophagous arthropods use chemical (semiochemical) signals to find their hosts and mates.Chemical signals produced by other mites of the same species (pheromones) attract them [105] and chemicals produced by the hosts (allelochemicals) attract (kairomones) or repel them (allomones) [62,104].
Volatile organic compounds (VOCs) were isolated from the uropygial gland of a duck (non-host mite) and can be added directly to chicken feed.After ingestion, chickens release these compounds through the uropygial gland and repel hematophagous mites (D. gallinae and Ornithonyssus sp.), interrupting their feeding and social behavior [62,106].
Aufray et al. [105] showed that hungry female PRM on a French farm were attracted to a complex mixture of five synthetic VOCs: R-1-octen-3-ol, octanal, nonanal, (E)-2-nonenal, and nonanoic acid, combined in equivolumetric proportions or with (E)-2-nonenal as the main constituent [105].Cunha (2008) conducted a study on the response of protonymphs to scents from the extracts of conspecific mites and observed that the protonymphs of D. gallinae produce a pheromone capable of attracting and stimulating encounters with other protonymphs of D. gallinae [16].
Chemical ecology studies involving repellency or attraction in hematophagous mites are still poorly understood, but the results so far indicate a new field for new research and different approaches aimed at developing new products for use against poultry hematophagous mites.

Vaccines
Vaccine research aimed at identifying additional forms of poultry mite control has presented new perspectives in recent years [7,42,51,107] (Table 5), driven by an increase in egg and meat production and consumer demand, and it is performed in an environmentally responsible and organic way [27,96].
It is important to emphasize that vaccines are recognized as solutions that offer protection and can also be used in IPM to cut back on the use of and expenses due to acaricides and the labor involved in spraying them.In addition, vaccines are safe for poultry and do not pollute the environment, leave residues in meat and eggs, or pose a risk of triggering resistance in mites [7,22,27,42,62].Recent studies have shown vaccines to be effective against ectoparasites, for example, transmissionblocking vaccines (TBVs) [7,27,42,51,[107][108][109][110][111][112] (Table 5).
The vaccination process triggers a memory immune response with specific antibody production against the antigenic target, thus providing protection against pathogens that can be controlled by the humoral immune response [47].TBVs, unlike conventional vaccines, aim to generate a humoral immune response in the vaccinated host, triggering the specific antibody production that is transferred to ectoparasites during blood feeding [18,27,[108][109][110]112].The transferred antibodies act by binding to proteins that are essential for ectoparasite's survival, disrupting its reproduction, and transmission of pathogens [27,47,[111][112][113].
The development of TBVs applied to vector-borne diseases was previously described against the sporozoite forms of Plasmodium that cause malaria.The specific antibody production triggered by the recombinant Pfs25 protein acts within the insect vector, interfering in pathogen transmission [108,111].The antibodies that are transferred during vector blood feeding recognize the gamete surface antigen of Plasmodium, affecting the parasite's life cycle inside the mosquito by preventing its sexual development and interrupting its biological cycle and transmission [18,108,109,111,113].According to Shimp et al. [113], in the first clinical trial, the experimental sporozoite vaccine reduced the incidence of disease over a 14-month period in about 50% of vaccinated infants and children by preventing subsequent blood-stage infection.
Another example includes the vaccines against Rhipicephalus microplus, the cattle tick, TickGARD ® in Australia and Gavac ® in Cuba, developed from the recombinant Bm86 glycoprotein extracted from the tick's gut [31,50,112,114].The mechanism of action is associated with the induction of specific antibodies that target cells in the tick's gut and either impede their development or cause their death [27,107,112].Table 5 describes the potential vaccine trials aimed at identifying antigenic targets for blocking the transmission of D. gallinae.Harrington et al. [17] used an extract of D. gallinae and obtained efficacy of around 50% in a laboratory study.Harrington et al. [17] hypothesized that the feeding chamber interfered with the mite's feeding, reducing the transfer of antibodies induced by vaccination.Similarly, Xu et al. [107] proposed that their low protection rate could be explained by interference from the feeding chamber, as reported by Harrington (2008).
Harrington et al. [50] used recombinant antigen Bm86 and Subolesin from R. microplus against D. gallinae, which were able to generate an immune response, but with low efficacy (23.03% and 35.1%, respectively).Bm86 and Subolesin are not found in D. gallinae, a fact that may have hampered the development of an effective immune response [50].
Wright et al. [31] and Price et al.
[43] extracted proteins from D. gallinae macerate to act as possible vaccine candidates but obtained results below 50%.Additionally, Price et al. [43] proposed that the low efficacy may have occurred because of the lack of a specific humoral immune response to the antigen used due to low levels of antigen expression or incorrect folding of the expressed protein.
Bartley et al. [42] obtained a potential vaccine candidate using extracted protein from D. gallinae macerate, achieving results of around 50% of protection under laboratory conditions, but it was ineffective when using recombinant proteins and submitting it to a field test.The reason may have been the lack of proper selection of antigen, inducing an inadequate protective immune response [59].Xu et al. [107], Fujisawa et al. [14], and Murata et al. [115] developed recombinant proteins, rDg-CatD-1, Dg-APMAP-N, and Deg-CPR-1, respectively with an efficacy rate above 50% under laboratory conditions, thus paving the way for new studies.
The transmission-blocking vaccines against poultry mites need to be improved in terms of efficacy, especially for applicability in the field.Poultry farms have large numbers of animals that make administering vaccines time-consuming and costly for the producer.Yet, the expense and time would be justified if poultry farmers had access to effective vaccines that yielded long-term results, making them an advantageous, competitive option compared to the low-cost acaricides currently available on the market [27,111].In fact, consumers are pressuring the market for sustainable products, particularly food products that replace the use of chemicals with vaccines.
The control methods now in use still show a wide variation in effectiveness, making it difficult to determine their treatment efficacy, especially in the field (Figure 2).For mites that infest and feed on the feathers and epidermis of poultry, such as Megninia spp.[28,72] and Allopsoroptoides galli [4,116,117], and for the hematophagous mite Ornithonyssus spp., no published references of ongoing research to identify antigens for possible vaccine development were found.With regard to the mites that infest the feathers and epidermis of poultry, antigenic compounds that trigger specific antibodies For mites that infest and feed on the feathers and epidermis of poultry, such as Megninia spp.[28,72] and Allopsoroptoides galli [4,116,117], and for the hematophagous mite Ornithonyssus spp., no published references of ongoing research to identify antigens for possible vaccine development were found.With regard to the mites that infest the feathers and epidermis of poultry, antigenic compounds that trigger specific antibodies cannot be transferred to the ectoparasite during the blood meal because the form of feeding does not contain blood, thus limiting the application of TBVs.

Integrated Pest Management (IPM)
Integrated pest management (IPM), or integrated control [28,40], consists of using associated identification, certification, and monitoring techniques to eliminate or control mites on poultry farms [40,78,118].The IPM requires a study in the environment to better understand the difficulties and choose techniques, methods, or products capable of increasing mite mortality in environments [40,44].
Furthermore, the IPM approach may include chemical control measures using commercial products that are normally sprayed within environments and on animals [31,40,53,85].In addition, IPM can be used with mechanical or physical measures, including cleaning the environment to remove organic matter and sanitizing the materials and equipment afterward [44].Importantly, biological controls can be applied through traps impregnated with oils or plant extracts [17,28,40,111].

Conclusions
Poultry mites present on commercial farms continue to be a problem that needs to be addressed.The accelerated multiplication of mites and the expansion of their geographic distribution due to climate change, associated with the difficulty of developing effective forms of control and their role as a vector, call attention to the role mites play in the poultry industry.
The chemical methods currently used to control or eliminate them are proving to be less effective as they develop resistance.Those chemicals that are still effective can also become less effective over time due to their indiscriminate use.Biological control methods offer many advantages related to animal, human, and food safety, but their efficiency remains low when used in poultry farms, making the need for integrated controls even more essential, but generating higher costs.Moreover, the major limitation of this revision is the restricted information available for mite vaccines that could promote a more effective development in this field.
The development of products based on plant oils and extracts, powders of plant origin, fungi, and new antigens aimed at developing transmission-blocking vaccines against poultry mites so as to provide some encouraging options for the rational control of these ectoparasites.

Figure 1 .
Figure 1.Geographic distribution of D. gallinae and Ornithonyssus spp.throughout the world.

Figure 1 .
Figure 1.Geographic distribution of D. gallinae and Ornithonyssus spp.throughout the world.

Figure 2 .
Figure 2. Distinct approaches for controlling mites in laying hens and broilers.

Figure 2 .
Figure 2. Distinct approaches for controlling mites in laying hens and broilers.

Table 1 .
Efficiency of chemicals tested against poultry hematophagous mites.

Table 2 .
Efficiency of plant-derived compounds tested against poultry hematophagous mites.

Table 3 .
Efficiency of entomopathogenic fungi tested against poultry hematophagous mites.
* Result considers a higher dose and is obtained after the end of the last treatment dose.The numbers1,2correspond to product, chemical class, test environment, and mortality.

Table 4 .
Efficiency of diatomaceous earth and synthetic silica-based products tested against poultry hematophagous mites.