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Diagnosing Parasitic Infections
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
Onchocerca volvulus may lead to blindness due to an inflammatory response and high parasite burden. This is also known as river blindness and is seen almost exclusively in areas endemic for this parasite. Acanthamoeba can cause keratitis through infected contact lenses.
Acanthamoeba castellanii
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
The pathogenic Acanthamoeba spp. cause rare infections in humans with the patients with AK dominating over cases of GAE, and pulmonary and skin infection. These unicellular eukaryotes are of clinical significance in cases of diseases that come under the headings of immunosuppressive states or are the ones that make the person weak enough to mount an effective immune response. It is imperative that these infections should be avoided whenever possible from water and foodborne sources that are infected with Acanthamoeba. More research is needed to develop rapid diagnostic methods and treatment protocols to help cases with GAE and AK. Identification of Acanthamoeba in food resources needs to be further investigated, as we do not know the incidences of the infection of skin and soft tissue that could result from this source to patients with AIDS and patients suffering from other immune deficiency–related disorders. More insights are needed to know the source of these FLA detected on vegetables and beans and whether the water contamination is seeding them on food resources or they prey on foods like vegetables and beans. Answers to these questions are expected to clarify the infections caused by FLA from food resources and help prevent diseases related to them.
The cornea
Published in Mary E. Shaw, Agnes Lee, Ophthalmic Nursing, 2018
Acanthamoeba keratitis is usually associated with a history of improper cleaning of contact lenses, using homemade sodium chloride solution to clean the lenses, and swimming in fresh water or a swimming pool while contact lenses are worn. Keratitis typically begins with a foreign-body sensation followed by pain, tearing, photophobia, blepharospasm and blurred vision. Patients may have periods of symptom remission with a waxing and waning course. The condition is very painful as the organism has a predilection for the corneal nerves – radial perineuritis and a ring-shaped infiltrate are findings which would strongly suggest Acanthamoeba keratitis. Early diagnosis and treatment are paramount for improving outcomes. A high index of suspicion is needed to make the diagnosis, especially in the early stages. The earliest clue to this infection is a dendriform pattern noted on the epithelium of the cornea. Identification of Acanthamoeba consist of culture on a buffered charcoal yeast extract or with non-nutrient agar overlaid with organisms such as Escherichia coli, polymerase chain reaction of biopsy specimens and scanning confocal corneal microscopy. If corneal specimens are unremarkable, consider culturing the contact lenses and saline solution for Acanthamoeba (Kerr 2014).
Epidemiology of free-living amoebae in the Philippines: a review and update
Published in Pathogens and Global Health, 2022
Giovanni D. Milanez, Frederick R. Masangkay, Gregorio L. Martin I, Ma. Frieda Z Hapan, Edilberto P. Manahan, Jeffrey Castillo, Panagiotis Karanis
Despite the reported diversity of FLA and pathogenic genotypes in various environmental sources in the country (Figure 3), reports on morbidity and/or mortality cases of FLA-related infections remain largely unknown. Acanthamoeba keratitis (AK) was first reported in the country in 1992 [33]. Between 2002 and 2004, three more cases of AK were reported [35]. In 2009, a 76-years-old male reported pain, redness, and visual impairment of the right eye where molecular testing confirmed Acanthamoeba genotype T4 [36]. It is important to note that all these AK cases involved non-contact lens wearers and that the latter case used tap water to cleanse the face before the onset of symptoms. Surprisingly, in the study of Cruz and Rivera (2014), 4.4% (8/180) of nasal swabs from asymptomatic volunteers were positive with Acanthamoeba spp. T4 and T5 [3]. The proposed transmission route was obviously from the chronic exposure of the volunteers to garbage, soil, and dust as part of their everyday activity. In this case, it is interesting to speculate on the potential health outcomes in the event of depression or suppression of the immune system of the Acanthamoeba-positive volunteers. Also, it opens up perspectives into the health hazards on FLA-related infections faced by high-exposure groups of laborers working in unsanitary conditions and environments. Also, the predominance of Acanthamoeba genotype T4 and T5 in local human cases was potentially influenced by the propensity of the same genotypes reported in the highest frequencies in local environmental sources.
Systemic Miltefosine as an Adjunct Treatment of Progressive Acanthamoeba Keratitis
Published in Ocular Immunology and Inflammation, 2021
Andrea Naranjo, Jaime D. Martinez, Darlene Miller, Rahul Tonk, Guillermo Amescua
Acanthamoeba keratitis (AK) is one of the most challenging infections ophthalmologists encounter in practice due to its wide range of clinical manifestations, symptoms, delayed diagnosis, and frequent lack of response to standard medical treatment.1 These challenges drive the clinical and research interest in developing novel, effective therapies for the condition. Acanthamoeba spp. are protozoa that are ubiquitous in air, soil, dust, and water.2 Its virulence factors include the secretion of multiple proteases, which help it degrade the corneal stroma and reach deep into the cornea.3 The parasite is thought to feed on keratocytes and has the ability to form cysts when facing adverse environmental challenges. The cysts constitute the dormant form of the organism which are able to survive even under nutrient deficiency and exposure to noxious injury.4 Current medical treatment for Acanthamoeba includes biguanides (polyhexamethylene biguanide (PHMB) and chlorhexidine);4 diaminides such as propamidine isethionate, dibromopropamidine, and hexamidine;5 and others such as neomycin and/or oral voriconazole.6 Steroid use still remains controversial4,7: past studies have shown that steroid treatment prior to anti-acanthamoeba therapy is detrimental,8 but more recent work has suggested that steroids, when introduced after 2 weeks of anti-amoebic treatment, may aide with discomfort without impairing outcomes.7
Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis
Published in Clinical and Experimental Optometry, 2021
Lily Ho, Isabelle Jalbert, Kathleen Watt, Alex Hui
In the United Kingdom, Acanthamoeba keratitis is suggested as more common than fungal keratitis.61 Studies from the United Kingdom have reported a strong association of contact lens wear with Acanthamoeba keratitis, with approximately 90% of Acanthamoeba keratitis attributed to contact lens wear and most cases having identifiable risk factors such as poor contact lens disinfection, swimming, and/or bathing while wearing the contact lenses.62–64 An Australian study found 80% of Acanthamoeba keratitis cases presenting to Sydney Eye Hospital occur in contact lens wearers, within which poor hygiene attributed additional risk.65 Contact with contaminated water remains the major risk for Acanthamoeba keratitis.31,64