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Gamasoidosis, also known as dermanyssosis, is a frequently unrecognized form of zoonotic dermatitis, following human infestation with avian mites of the genera Dermanyssus or Ornithonyssus. It is characterized by pruritic erythematous , macules and urticaria, with itching and irritation resulting from the saliva the mites secrete while feeding. These bites are observed all over the body. The avian mite Dermanyssus gallinae can also infest various parts of the body, including the ear canal and scalp.
Diagnosis is challenging due to the mites' size, requiring microscopic identification by a medical entomologist, and the clinical symptoms often mimic other conditions, such as scabies or allergic reactions. The atypical or delayed responses to mite bites, coupled with widespread ignorance and misinformation among healthcare providers, scientists, and pest control professionals, contribute to frequent underdiagnosis and misdiagnosis, hindering effective management and treatment.
Gamasoidosis is linked to avian mites infesting residential, public and agricultural spaces, with a potential health threat due to the transmission of zoonotic pathogens by D. gallinae. Treatment involves eliminating mites from the environment—a process complicated by their resilience and rapid reproduction—and managing patient symptoms, which are typically self-limiting but may require supportive care.
The condition poses a growing public health concern, linked to urbanization, occupational risks, and zoonotic pathogens. Limited awareness and misdiagnoses highlight the need for a "One Health" approach, integrating experts to improve diagnosis, prevention, and treatment for better human and animal health.
Bites can be found anywhere on the body. Described areas affected include the waist, trunk, upper extremities, abdomen, legs, finger webs, , groin, buttocks, and face. Bites are frequently reported to be grouped and more pronounced in areas where clothing applies pressure, such as along a belt line or beneath the breasts. When feeding happens during sleep, bedding may show red stains from crushed mites or their droppings.
Additional symptoms include pinpricks, secondary infections, scarring and hyperpigmentation.
Gamasoidosis in farm workers is associated with Poultry farming, with a "19% incidence of contact dermatitis reported in a two-year survey of workers on 58 European poultry farms". D. gallinae exposure is so common that it is considered an occupational hazard for these workers.
For pets, there are currently no registered products for treating gamasoidosis in mammals. The scientific literature documents medications which have been used Off-label use to treat the condition, including sarolaner in dogs, selamectin in cats and permethrin in horses.
Avian and rodent mites have been documented as infesting residential buildings, work spaces, schools and hospitals. Despite this, widespread ignorance and misinformation about human infestation with D. gallinae exists across the healthcare, scientific, and pest control sectors, which in turn has led to increasing numbers of infestations and a dangerous propagation of the disease.
Because gamasoidosis is a rare diagnosis and its skin reactions are often atypical, most physicians are unfamiliar with the condition. As a result, gamasoidosis is frequently overlooked or misdiagnosed. One misdiagnosis is scabies; however, unlike Scabies mite, avian mites can be seen with the naked eye and do not burrow. Bites can also be mistaken for those caused by other conditions such as cheyletiellosis ( Cheyletiella), trombiculosis ( Trombicula), bedbug infestations ( Cimex lectularius), or Hives. Additionally, these lesions are sometimes misattributed to allergic reactions or misinterpreted as symptoms of delusional parasitosis. Dermatoscopy can help differentiate mite infestations from delusional parasitosis, aiding in accurate diagnosis.
Allergists and dermatologists should prioritize inspecting potential sources to locate, collect, and accurately identify mites, a task best handled by skilled parasitologists. Identification of the species is best carried out by a medical entomologist using a microscope. Distinguishing Ornithonyssus from Dermanyssus and identifying cryptic species within D. gallinae is difficult due to overlapping traits and reproductive isolation. D. gallinae mainly infests poultry globally, while special lineage L1 targets pigeons, posing zoonotic risks in urban areas. DNA analysis, including mitochondrial markers, is required for precise identification. Accurate species determination is crucial for recommending appropriate treatment methods.
Gamasoidosis usually affects only one person in a household, as the condition requires both mite exposure and an allergic sensitivity. However, there have been reported cases where all members of a nuclear family experience symptoms in response to avian mite bites.
Many cases of gamasoidosis go unreported, suggesting that the actual incidence is higher than generally believed. As a result, in cases of unexplained bites in residential areas, the involvement of D. gallinae should always be considered, especially during late spring and early summer when wild birds make their nests. Diagnosing the responsible agent in symptomatic workers can be challenging. Over time, workers may develop a tolerance to mite bites, decreasing the likelihood of reporting such incidents. Nonetheless, outbreaks can occur after periods of reduced exposure or when new employees are introduced to the workplace.
Blood-feeding starts at the protonymph stage, with adults feeding briefly at night every two to three days. Engorged females turn red and lay eggs soon after feeding. They may also feed during the day if the room is sufficiently dark. Attacks in public and office buildings tend to occur during the daytime. O. bursa is an exception as it generally remains on its hosts and will feed during the day.
In urban homes D. gallinae may be commonly found in the bedroom or where the patient sleeps, as they prefer to stay close to their host for optimal feeding. Typically, it visits its host for 1–2 hours, departing after completing its blood meal. They are highly mobile and can locate potential hosts through temperature changes, vibrations, chemical signals, and carbon dioxide emissions. Avian mites can travel through various pathways such as floors, walls, ceilings, and most commonly via ventilation or air conditioning systems.
Avian mite species, such as Dermanyssus gallinae, can survive for over nine months without a blood meal. Their nocturnal behavior and tendency to leave the host after brief feeding sessions to hide in cracks and crevices further complicate eradication efforts. Eggs and larvae are often located away from birds or humans, typically hidden in hard-to-reach crevices that may be distant from treated areas.
Under favorable conditions, avian mite populations can expand rapidly. For instance, a single female mite can lay up to 30 eggs in her lifetime and prolonged darkness can significantly accelerate their growth. D. gallinae thrives at temperatures of 20–25°C and a relative humidity of 70–90%, while low humidity and extreme temperatures (below 5°C or above 45°C) hinder their development and survival.
Avian mites are also capable of digesting human blood and it is widely believed that they cannot reproduce without avian blood. However, some studies, such as those by George et al., suggest that avian mites may develop and sustain prolonged infestations on human blood, challenging this assumption.
The treatment of gamasoidosis is further complicated by pesticide resistance among avian mites and their diverse ecological behaviors, which require tailored treatment strategies. Employing a variety of techniques, following a Integrated Pest Management approach, can reduce the likelihood of major re-infestations and limit the development of resistance to specific insecticides.
Attempts to eradicate infestations are often prolonged and ineffective, leading to significant financial burdens and psychological issues such as depression, particularly when patients are forced to relocate or invest heavily in pest control measures.
D. gallinae may pose a threat to public health as the mite may be a Disease vector or reservoir of several Zoonosis pathogens, such as Chlamydia psittaci, Erysipelothrix rhusiopathiae, Salmonella spp., Mycobacterium spp., Coxiella burnetii, Bartonella, Borrelia afzelii, Venezuelan equine encephalitis virus, Eastern equine encephalitis virus, and Fowlpox virus. An association has not been found with gamasoidosis and alpha-gal allergy.
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