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Abstract Background Balamuthia mandrillaris is a free-living ameba that causes rare, nearly always fatal disease in humans and animals worldwide. B. mandrillaris has been isolated from soil, dust, and water. Initial entry of Balamuthia into the body is likely via the skin or lungs. To date, only individual case reports and small case series have been published. Methods The Centers for Disease Control and Prevention (CDC) maintains a free-living ameba (FLA) registry and laboratory. To be entered into the registry, a Balamuthia case must be laboratory-confirmed. Several sources were used to complete entries in the registry, including case report forms, CDC laboratory results, published case reports, and media information. SAS© version 9.3 software was used to calculate descriptive statistics and frequencies. Results We identified 109 case reports of Balamuthia disease between 1974 and 2016. Most (99%) had encephalitis. The median age was 36 years (range 4 months to 91 years). Males accounted for 68% of the case patients. California had the highest number of case reports, followed by Texas and Arizona. Hispanics constituted 55% for those with documented ethnicity. Exposure to soil was commonly reported. Among those with a known outcome, 90% of patients died. Conclusions Balamuthia disease in the United States is characterized by a highly fatal encephalitis that affects patients of all ages. Hispanics were disproportionately affected. The southwest region of the United States reported the most cases. Clinician awareness of Balamuthia as a cause of encephalitis might lead to earlier diagnosis and initiation of treatment, resulting in better outcomes. We describe 109 case reports of Balamuthia disease in the United States between 1974 and 2016. Most were male with encephalitis, had a median age of 36 years, and were reported from southwestern states. Ninety percent of patients died.

Balamuthia mandrillaris is a highly lethal free-living ameba that primarily affects the skin and central nervous system, manifesting clinically as chronic granulomatous lesions and granulomatous encephalitis. Once the central nervous system is involved, the mortality rate exceeds 90%. No standardized treatment regimen has yet been established. In this review, we summarized 66 cases reported from China. The median patient age was 36 years (range 10 months-77 years); 62.12% patients were male and 37.88% female. Fifty-five (83.33%) patients were immunocompetent. For 42 (63.64%) patients, initial symptoms were cutaneous manifestations; of those, central nervous system involvement subsequently developed in 25 (59.52%) patients. Twenty-four (36.36%) patients were hospitalized initially with encephalitis. Among the 63 patients with a known outcome, 43 (68.25%) succumbed to infection. For patients with cutaneous-only disease, the survival rate was 93.75%, whereas once the central nervous system was affected, mortality reached 96.00%.

Amebiasis remains a public health challenge in Mexico, especially in areas with poor sanitation. Despite declining prevalence (2014-2023), hotspots persist because of socioeconomic factors such as poverty. Addressing regional disparities through targeted interventions, improved infrastructure, and education is crucial to further reduce the disease burden and prevent future outbreaks.

[b]Abstract Introduction[/b]. Among free-living amoebae that are widely distributed in nature only four genera/species are known as agents of human infections:[i] Acanthamoeba spp., Naegleriafowleri, Balamuthia mandrillaris[/i] and[i] Sappiniapedata[/i]. These amoebae are not well adapted to parasitism, and could exist in the human environment without the need for a host. Infections due to these amoebae, despite low morbidity, are characterized by relatively high mortality rate and pose serious clinical problems. [b]Objectve[/b]. This review study presents and summarizes current knowledge about infections due to pathogenic and opportunistic free-living amoebae focused on epidemiology, clinical manifestations, diagnosis and treatment based on global literature. [b]State of knowledge[/b]. All four genera have been recognized as etiologic factors of fatal central nervous system infections and other serious diseases in humans. [i]N. fowleri[/i] causes an acute fulminating meningoencephalitis in children and young adults. [i]Acanthamoeba spp[/i]. and [i]B.mandrillaris[/i] are opportunistic pathogens causing granulomatous amoebic encephalitis and disseminated or localized infections which could affect the skin, sinuses, lungs, adrenals and/or bones. [i]Acanthamoeba spp[/i]. is also the main agent of acute eye infection -[i] Acanthamoeba keratitis, [/i]mostly in contact lens wearers. However, there is only one recognized case of encephalitis caused by [i]S. pedata. [/i] [b]Conclusions[/b]. Amoebic diseases are difficult to diagnose which leads to delayed treatment, and result in a high mortality rate. Considering those issues, there is an urgent need to draw more attention to this type of diseases.

Entamoeba histolytica is a protozoan parasite that causes amebic colitis, a leading cause of severe diarrheal disease worldwide, and amebic liver abscess, the most common extraintestinal manifestation of infection. The disease burden is highest in resource-limited settings but remains clinically important in travelers and men who have sex with men in non-endemic regions. Although most infections are asymptomatic, severe and fulminant disease is associated with high mortality, particularly among individuals exposed to corticosteroids or other forms of immunosuppression. The increasing use of molecular diagnostic tools has improved understanding of the epidemiology of E. histolytica and enabled distinction from morphologically identical but nonpathogenic Entamoeba species; however, these diagnostics remain underutilized in many endemic settings due to cost and infrastructure limitations. Treatment options remain limited, with nitroimidazoles constituting the only drug class available for symptomatic invasive disease, leaving few alternatives for patients who cannot tolerate therapy or in the event of emerging resistance. Despite advances in understanding parasite pathogenesis and the application of high-throughput technologies, no licensed vaccine exists, and progress toward vaccine development has been minimal. These persistent gaps highlight the need to reprioritize amebiasis as a neglected tropical disease and to accelerate investment in diagnostics, therapeutics, and preventive strategies.

Amebiasis cases in Japan are reported to the government according to the Infectious Diseases Control Law. Previous studies have shown significant reductions in total case numbers after 2018 and during the COVID-19 pandemic. This study aimed to clarify the recent trends of amebiasis cases in Japan, including during the pandemic period, with details on places of infection, using government surveillance data from January 1, 2001, to December 31, 2022. Change of time trends were modeled through piecewise mixed-effect regression model with knots set at 2018 and 2020. Year-to-year differences in case numbers were statistically assessed using Poisson regression model. And descriptive analyses of amebiasis cases reported in Japan by sex, age class, and prefecture (from 2001 to 2022) were conducted. Piecewise time trends of male-domestic cases showed increasing trend by 59.5 cases per year (p < 0.0001) before 2008. The trend slowed but still increased during 2008–2018, showing annual increase of 15.2 cases per year (p = 0.0014). A sharp decline occurred during 2018–2020, with cases decreasing by 219.0 cases per year (p < 0.0001). After 2020, the trend did not show statistically significant change (−16.9 cases per year, p = 0.6532). Poisson regression confirmed significant reductions in total and domestic cases between 2017–2018 and 2019–2020, while imported cases declined significantly only between 2019 and 2020. Male cases predominated, with most male cases in their 40s and 50s. Most cases of amebiasis have been reported in metropolitan areas. These results suggest that the decreased case numbers during the COVID-19 pandemic were due to not only the travel ban, but less socioeconomic activity. Furthermore, the epidemiology of amebiasis is similar to that of HIV infection in Japan, but the case numbers of amebiasis have not yet increased through 2022, showing a different trend from HIV infection and syphilis, the reason of which is unclear and needs further investigation.

About the Authors: Debbie-Ann T. Shirley Affiliation: Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America ORCID logo http://orcid.org/0000-0003-1718-0901 Koji Watanabe Affiliation: AIDS Clinical Center, National Center for Global Health and Medicine, Shinjuku, Tokyo, Japan Shannon Moonah * E-mail: sm5fe@virginia.edu Affiliation: Department of Medicine, University of Virginia School of Medicine Charlottesville, Virginia, United States of America Introduction Nearly 150 years since the first detailed description of the invasive, tissue-destroying intestinal parasite, Entamoeba histolytica, amebiasis remains an infection of consequential global importance. In a large, multinational, prospective case-based study of children with moderate-to-severe diarrhea using molecular methods to identify etiology, however, amebiasis ranked among the top 15 causes of diarrhea in the first two years of life in children living in developing countries, where diarrhea remains the fifth leading cause of death in children under the age of five years [1, 3–5]. Amebiasis was the third most frequently isolated pathogen among returning travelers presenting to one of 42 GeoSentinel Surveillance Network sites globally and seeking medical attention for gastrointestinal infection [14]. Several properties of the E. histolytica cyst, such as low infectious dose and relative resistance to chlorine, facilitate the ease with which it can be disseminated through contamination of food and water supplies, even in low incidence areas. [...]E. histolytica is classified as a category B priority biodefense pathogen by the National Institute of Allergy and Infectious Diseases.

In 2008 a fatal case of primary amoebic meningoencephalitis, due to the amoeboflagellate Naegleria fowleri, occurred in Guadeloupe, French West Indies, after a child swam in a bath fed with geothermal water. In order to improve the knowledge on free-living amoebae in this tropical part of France, we investigated on a monthly basis, the presence of Naegleria spp. in the recreational baths, and stream waters which feed them. A total of 73 water samples, 48 sediments and 54 swabs samples were collected from 6 sampling points between June 2011 and July 2012. The water samples were filtered and the filters transferred to non-nutrient agar plates seeded with a heat-killed suspension of Escherichia coli while sediment and swab samples were placed directly on these plates. The plates were incubated at 44°C for the selective isolation of thermophilic Naegleria. To identify the Naegleria isolates the internal transcribed spacers, including the 5.8S rDNA, were amplified by polymerase chain reaction and the sequence of the PCR products was determined. Thermophilic amoebae were present at nearly all collection sites. The pathogenic N. fowleri was the most frequently encountered thermophilic species followed by N. lovaniensis. The concentration of N. fowleri was rather low in most water samples, ranging from 0 to 22 per liter. Sequencing revealed that all N. fowleri isolates belonged to a common Euro-American genotype, the same as detected in the human case in Guadeloupe. These investigations need to be continued in order to counsel the health authorities about prevention measures, because these recreational thermal baths are used daily by local people and tourists.

This study examines the potential implications of biofouling management on the development of an infectious disease in Norwegian farmed salmon. The hydroid Ectopleura larynx frequently colonises cage nets at high densities (thousands of colonies per m2) and is released into the water during regular in-situ net cleaning. Contact with the hydroids’ nematocysts has the potential to cause irritation and pathological damage to salmon gills. Amoebic gill disease (AGD), caused by the amoeba Paramoeba perurans, is an increasingly international health challenge in Atlantic salmon farming. AGD often occurs concomitantly with other agents of gill disease. This study used laboratory challenge trials to: (1) characterise the gill pathology resulting from the exposure of salmon to hydroids, and (2) investigate if such exposure can predispose the fish to secondary infections–using P. perurans as an example. Salmon in tanks were exposed either to freshly ‘shredded’ hydroids resembling waste material from net cleaning, or to authentic concentrations of free-living P. perurans, or first to ‘shredded’ hydroids and then to P. perurans. Gill health (AGD gill scores, non-specific gill scores, lamellar thrombi, epithelial hyperplasia) was monitored over 5 weeks and compared to an untreated control group. Nematocysts of E. larynx contained in cleaning waste remained active following high-pressure cleaning, resulting in higher non-specific gill scores in salmon up to 1 day after exposure to hydroids. Higher average numbers of gill lamellar thrombi occurred in fish up to 7 days after exposure to hydroids. However, gill lesions caused by hydroids did not affect the infection rates of P. perurans or the disease progression of AGD. This study discusses the negative impacts hydroids and current net cleaning practices can have on gill health and welfare of farmed salmon, highlights existing knowledge gaps and reiterates the need for alternative approaches to net cleaning.

Background Amebiasis represents a significant global health concern. This is especially evident in developing countries, where infections are more common. The primary diagnostic method in laboratories involves the microscopy of stool samples. However, this approach can sometimes result in the misinterpretation of amebiasis as other gastroenteritis (GE) conditions. The goal of the work is to produce a machine learning (ML) model that uses laboratory findings and demographic information to automatically predict amebiasis. Method Data extracted from Jordanian electronic medical records (EMR) between 2020 and 2022 comprised 763 amebic cases and 314 nonamebic cases. Patient demographics, clinical signs, microscopic diagnoses, and leukocyte counts were used to train eight decision tree algorithms and compare their accuracy of predictions. Feature ranking and correlation methods were implemented to enhance the accuracy of classifying amebiasis from other conditions. Results The primary dependent variables distinguishing amebiasis include the percentage of neutrophils, mucus presence, and the counts of red blood cells (RBCs) and white blood cells (WBCs) in stool samples. Prediction accuracy and precision ranged from 92% to 94.6% when employing decision tree classifiers including decision tree (DT), random forest (RF), XGBoost, AdaBoost, and gradient boosting (GB). However, the optimized RF model demonstrated an area under the curve (AUC) of 98% for detecting amebiasis from laboratory data, utilizing only 300 estimators with a max depth of 20. This study highlights that amebiasis is a significant health concern in Jordan, responsible for 17.22% of all gastroenteritis episodes in this study. Male sex and age were associated with higher incidence of amebiasis ( P = 0.014), with over 25% of cases occurring in infants and toddlers. Conclusions The application of ML to EMR can accurately predict amebiasis. This finding significantly contributes to the emerging use of ML as a decision support system in parasitic disease diagnosis. Graphical Abstract