Red Mite Control

The poultry red mite Dermanyssus gallinae is one of the most common poultry ectoparasites and occurs worldwide (Table 1). The prevalence of these arthropods varies depending on the production system and humidity.

Conventional cage systems have a lower prevalence of mites than other housing systems. As the egg industry moves to free-cage systems, Dermanyssus gallinae can become more abundant and difficult to control. Generally, farms with humidity below 60% had a lower risk of infestation. Global warming and higher relative humidity could be increasing its prevalence in some regions.

• These mites are generally an animal issue.
• However, recent reports have gained medical attention due to infestations among poultry workers, a condition known as gamasoidosis.
• Eventually, residences, hospitals, and office spaces can be infested by synanthropic or wild birds.
• The costs associated with control and production losses due to red mites have been estimated at €231 million per year for the European Union egg industry alone.
• The global impact is significant and deserves greater attention.

Table 1. Prevalence of Dermanyssus gallinae (red mite) across countries reported in various publications.

Red mite biology

This mite only measures 1.5 mm, and its color varies from gray to brown or red depending on its feeding status. Their host generally is laying hens, but eventually infests broilers, broiler breeders, and other poultry categories. Reports indicate that red mites can infest more than 30 species of wild birds, horses, rodents, and humans. The density of infestation per bird can reach 50,000 mites per bird in caged systems, but it can be 10 times higher.

• Dermanyssus gallinae spends most of its time off-host in the premises.
• Red mites locate their hosts using a combination of temperature stimuli, chemical signals, and responses to vibration and carbon dioxide.
• Red female mites ingest blood from the host for a short period, usually an hour, and feed only every 2 to 4 days, mainly, but not exclusively, in the darkness.
• Red male mites may have a more intermittent feeding behavior.

The development cycle of Demanyssus gallinae from egg to adult, through the larval stage and two nymphal stages, typically takes two weeks but can be as short as one week under tropical conditions. Infestations can occur year-round; however, they are generally more common during hot, humid seasons. Even after removing the birds, mites can persist in the environment for up to 8 months without feeding and can infest a new flock.

Red mites exhibit high genetic variability, enabling them to adapt rapidly to selective pressures. Acaricide-driven selection has led to increased genetic variation in populations, making them more resistant and harder to control. Resistance to carbamates and pyrethroids is well documented across Europe and may exceed 60%. 

Infestations and their implications

Mite infestations can originate from transport trucks, visitors, feed supplies, egg crates, wild birds or animals, and darkling beetles. Mites have a life cycle as short as 7 days under optimal environmental conditions, with relative humidity between 65 and 90% and temperatures between 25 and 35 °C.

• Several studies have indicated that red mite infestation can increase hen mortality by up to 10-fold in severe infestations.
• Mortality mainly results from anemia and from stress that disrupts sleep, leading to increased preening, head scratching, and feather-pecking during the day.
• Mites also increase birds’ aggressive feather pecking and cannibalistic behavior.
• Red mites also increase feed and water intake, and decrease bird condition, growth rates, feed conversion, egg production, and eggshell quality.

Mites may harbor and potentially transmit pathogens like Salmonella gallinarum, Salmonella enteritidis, Pasteurella multocida, Coxiella burnetiid, spirochetes, avian influenza virus, and fowl poxvirus. There is no definitive confirmation of disease transmission. Then, red mites are only suspected to be vectors, because finding pathogens inside a mite does not necessarily imply that they can be spread further. Red mites can reduce immunological responses, such as antibody titers, to some viral vaccines.

Control and treatment

Currently, a comprehensive integrated pest management approach is required for red mite control. Conventional treatments with chemical products are no longer effective.

• The integrated pest management includes constant hygiene, improved design and maintenance of premises, the traditional use of synthetic acaricides, the use of novel acaricides, and physical treatments such as dry heat and steam.
• Scientists are already considering biological control, use of pheromones, growth regulators, and vaccines.

Regular hygiene, biosecurity, proper ventilation to maintain relative humidity below 60%, and exposure of equipment and facilities to sunlight are vital to minimizing mite proliferation.  Heating poultry houses to over 35 °C can help reduce mite populations.

Mite control also involves monitoring pest populations by observing the birds and their premises. Targeted trapping programs are necessary to track populations.  Cardboard or plastic traps are the most common methods to trap mites. However, molecular diagnostic methods such as PCR have recently been used to confirm infestations.

Synthetic acaricides have been the primary treatment method. However, some countries have begun to restrict their use due to the emergence of acaricide resistance. Over 35 compounds have been tested for red mite control, including organochlorines, organophosphates, pyrethrins, pyrethroids, carbamates, amitraz, and endectocides.  Many are used without a license or even after they have been banned.

• Products approved for use in the European Union include Phoxim, abermectin, pyrethroids, and Cyfluthrin.
• Some that are not specifically approved but are still widely used include Bendiocarb, Amitraz, permethrin, carbaryl, carbamates, organophosphates, Propoxur, dichlorvos, Metrifonate, and propoxur.
• Products banned in the European Union since 2007 are fenitrothion, carbaryl, dichlorvos, and propoxur.

Conventional acaricide use includes lengthy post-spraying product withdrawal periods and restrictions on treatment while birds are laying to avoid egg residues. The novel acaricides include biopesticides and plant-derived products.

One novel product with high efficacy is Exzolt, a fluralaner oral solution for birds administered in drinking water at 0.5 mg/kg BW per treatment day, repeated seven days later.

• This is a systemic parasiticide that works by antagonizing ligand-gated chloride channels in the arthropod nervous system causing paralysis and death within four hours of feeding.
• This product also impairs mite reproduction, helping with total eradication in the facilities.

Fluralaner is a member of the novel class of isoxazoline-substituted benzamide derivatives. It is rapidly absorbed into the chicken’s bloodstream and widely distributed throughout the body, including skin and fat. This product does not leave residues in eggs, but at withdrawal period of 14 days after last administration of Exzolt is required for human consumption of meat and offal.

The biopesticides include:

1. Spinosad with 97% efficacy after a single dose, with residual efficacy of at least 28 days.
2. Bacillus thuringiensis

The current plant-derived products available are:

1. Garlic-based acaricides
2. Essential oils based on thyme (Thymus spp.), burdock (Arctium spp.), and tansy (Tanacetum vulgare).
3. Geraniols and forms of cinnamaldehyde.

Products combining diatomaceous earth, kaolin, silica, essential oils, and plant-derived ingredients have been evaluated with mixed results. There are several products commercially available. They normally absorb lipids from the mite’s surface, which leads to dehydration.

Future potential methods of control

Biological control includes the use of fungi, nematodes, bacterial endosymbionts, and predatory mites such as Androlaelaps casalis, Hypoaspis aculeifer, Hypoaspis miles, and Stratiolaelaps scimitus, which consume red mites. However, these mites are not commercially available for widespread use. 

Dermanyssus gallinae are susceptible to fungal isolates of Beauveria bassiana, Metarhizium anisopliae, Trichoderma album, and Paecilomyces fumosoroseus under lab conditions, but the efficacy in semifield conditions has been very low so far. Endosymbiotic bacteria coexisting with mites are critical for their oogenesis. Then, controlling these bacteria may help to control mites. In red mites, two bacteria Candidatus cardinium and Spiroplasma, have shown potential for future mite control.

• Mites use kairomones and pheromones to communicate and call aggregation in a bird.
• These products have been identified for control in combination with conventional acaricides, but no products are available yet.
• Growth regulators like Triflumuron can disrupt chitin synthesis, leading to delayed or premature pupal or adult development, respectively.

Vaccines against red mites have also been evaluated with very low efficacy so far. However, antigen research has demonstrated some potential to develop a vaccine against Dermanyssus gallinae based on somatic or recombinant proteins, with any vaccine likely to combine both exposed and concealed antigens. However, significant technical challenges must be overcome to develop a commercial vaccine.

In conclusion, red mites are a significant concern for the poultry industry, particularly for egg production worldwide. Hygiene and biosecurity are the most critical measures to prevent infestation, but the development of novel acaricides and the implementation of integrated pest management programs are also necessary.