Acanthamoebiasis is a protozoal lesion of the eyes, skin and central nervous system caused by free-living amoebas. The disease occurs in the form conjunctivitis and keratitis, dermatitis or granulomatous encephalitis. Complications can be corneal perforation, the formation of abscesses of internal organs. The diagnosis is established by detecting amoebas and their cysts in lacrimal fluid, corneal scrapings, skin biopsies, cerebrospinal fluid. Local and systemic treatment is carried out with antibiotics of the aminoglycoside group (in the form of eye drops, ointments, injections).
ICD 10
B60.1 Acanthamoebiasis
General information
Acanthamoebiasis is a protozoism caused by pathogenic amoebas of the genus Acanthamoeba. In most cases, acanthamoebiasis occurs in the form of acanthamoebic keratitis and acanthamoebic skin lesions. Sporadic cases of acanthamoebic dermatitis are more often reported in countries with subtropical and tropical climates. Acanthamoebic keratitis usually occurs in people using contact vision correction. Acanthamoebic granulomatous encephalitis is less commonly diagnosed. There are about 400 cases of acanthamebiasis occurring with CNS damage in the world; survival in this form is only 2-3%. T. A., acanthamebiasis is an urgent interdisciplinary problem solved by specialists in the field of ophthalmology, dermatology and neurology.
Causes
Among the free-living pathogenic amoebas of the genus Acanthamoeba, 6 species are dangerous to humans: A. hatchetti (cause eye damage), A. palestinensis and A. astronyxis (cause CNS damage), A. polyphaga, A. Culbertsoni, A. castellanii (cause various lesions, including skin). During the life cycle, amoebas of the genus Acanthamoeba undergo a vegetative stage (trophozoite) and a cyst stage.
Acanthamoebae are aerobic organisms living in soil, standing freshwater of natural and artificial reservoirs, especially those polluted by wastewater discharges. In addition, unicellular protozoa safely live in tap water, sewage, water from heating pipes. The increase in the population of acanthamoeba is facilitated by the water temperature above 28 ° C and the presence of various organic substances in it. In the case of a decrease in ambient temperature or drying of the reservoir, acanthamoebae are incised. In the state of cysts, parasites tolerate fluctuations in temperature and pH well, exposure to antiseptics and disinfectants.
When ingested into the human body, the pathogens of acanthamebiasis again pass into a vegetative state and become capable of parasitism. The source of the invasion is soil and water contaminated with acanthamoeba. Human infection is carried out by contact, household, food and waterways. Acanthamoebiasis of the eyes usually occurs in patients who do not follow the hygienic rules of wearing and caring for soft contact lenses: do not take them off during bathing and showering, neglect disinfection measures, do not treat their hands before putting on lenses, etc. In healthy people, acanthamoebae are often found in nasopharyngeal mucus and feces, but the development of acanthamoebiasis of the central nervous system is mainly affected by persons with immunodeficiency (especially HIV infection), diabetes mellitus, malignant neoplasms, alimentary insufficiency.
Symptoms of acanthamoebiasis
Acanthamoebiasis most often occurs in the form of acanthamoebic keratitis. The initial symptoms of an eye infection include redness of the eyes, cutting pain in the eyes, photophobia, lacrimation, blurred vision, feeling of a foreign body in the eye. In the late period, a ring-shaped or disc-shaped opacity of the cornea becomes noticeable. Alternation of exacerbations and remissions in acanthamebiasis of the eyes often leads to uveitis, scleritis, iridocyclitis, the formation of hypopion. Without adequate therapy, acanthamebiasis progresses rapidly, causing corneal perforation.
Acanthamoebiasis of the skin can occur primarily (independently) or secondarily, due to the initial lesion of the central nervous system. Primary acanthamoebic skin lesion occurs when water contaminated with amoeba cysts enters open wounds of the skin. At the same time, single or multiple nodules, papules or spots of gray-black color, reaching a diameter of 0.5-3 cm, are formed on the skin of the face, chest, back, limbs. In the future, these elements are transformed into skin ulcers covered with scab. With a prolonged course, the formation of acanthamoebic abscesses of muscles, lymph nodes, liver, lungs and other internal organs is possible. Secondary acanthamoebiasis of the skin is caused by the dissemination of acanthamoebae from the primary focus.
The defeat of the central nervous system in acanthamebiasis causes the development of granulomatous acanthamoebic encephalitis. This rare pathology usually occurs when acanthamoeba is hematogenically introduced into the brain from primary foci. Amoebic lesion can affect the substance of the brain, vascular or arachnoid membrane, basal ganglia. With normal resistance of the body, granulomatous inflammation develops; with reduced – necrotic process. The incubation period for acanthamoebic brain damage lasts from several weeks to a month or more. The initial period of acanthamebiasis is characterized by unstable subfebrility, drowsiness, headache, seizures, convergence disorders. The progression of CNS acanthamebiasis leads to the development of coma and death.
Diagnosis and treatment
Depending on the form of acanthamebiasis, its diagnosis and treatment is carried out by ophthalmologists, dermatologists, neurologists. The diagnosis of acanthamoeba lesions of the eyes, skin, and brain is confirmed by the detection of vegetative and cystic forms of acanthamoeba in the studied material. With acanthamoebic keratitis, it is lacrimal fluid, corneal flushes and scrapings; with acanthamoebic dermatitis, it is the discharge of infiltrates, skin biopsies; with granulomatous encephalitis, it is cerebrospinal fluid. In addition to microscopic examination of drugs, a culture method, serological tests, and a biological sample are used to verify the diagnosis of acanthamebiasis. If acanthamebiasis is suspected, keratitis, encephalitis and dermatoses of other etiology should be excluded from the patient.
Treatment of acanthamoebic keratitis requires the refusal to wear contact lenses. Local therapy includes hourly instillation into the conjunctival cavity of antibacterial drugs (gentamicin, neomycin, polymyxin B, etc.), corticosteroids; the use of antifungal agents (amphotericin B, ketoconazole). In combination with eye drops, ointment applications are used for the eyelid of the same funds. With progressive changes in the cornea, keratoplasty may be indicated.
With acanthamebiasis of the skin, systemic antibiotic therapy with drugs from the group of aminoglycosides, local application of ointments with neomycin, polymyxin, etc. is carried out. The most difficult task is the therapy of acanthamoebic encephalitis. In this clinical form of acanthamebiasis, intravenous administration of amphotericin B, the appointment of a combination of trimethoprim and sulfamethoxazole, aminoglycosides is indicated. Treatment of acanthamebiasis of the central nervous system is effective only in isolated cases.
Prognosis and prevention
With acanthamoebic lesions of the skin and eyes, the prognosis for life is favorable, but acanthamoebiasis of the brain in the vast majority of cases ends fatally. Prevention of acanthamoebic keratitis consists in observing the rules for the use and care of contact lenses, storing them only in special sterile solutions, processing lens containers, periodic instillation of bactericidal agents into the eyes (sodium sulfacyl, etc.), the need to remove contact lenses while bathing, visiting the bath and sauna, washing under the shower. To prevent acanthamoebiasis of the skin and the central nervous system, compliance with the rules of personal hygiene, limiting contact with polluted reservoirs, which are habitats of acanthamoebae.