Trends in Parasitology I Parasite of the Month Naegleria fowleri Jose E. Piňero,1* Bibiana Chávez-Munguía,2 Maritza Omaňa-Molina,3 and Jacob Lorenzo-Morales1* 11nstituto Universitario de Enfermedades Tropicales y Salud Publica de Canarias, Departamento de Obstetricia, Ginecología, Pediatría, Medicína Preventiva y Salud Publica, Toxicología, Medicina Legal y Forense y Parasitología, Universidad de La Laguna, La Laguna, Tenerife, Spain 2Departamento de Infectómica y Patogénesis Molecular, Centra de Investigación y de Estudios Avanzados del Instituto Politécnico Nacionál (Cinvestav), Ciudad de Mexico, Mexico 3UNAM FES Iztacala Carrera de Medicina Los Reyes Iztacala, Tlalnepantla, Estado de Mexico Cyst They attack the olfactory bulb and reach the brain Olfactory bulb Cribiform plate Olfactory nerves Trophozoites enter the nasal cavity with water Trophozoites adhere to olfactory nerves and cross the cribriform plate Flagellated trophozoite Trends in Parasitology Naegleria fowleri, also known as the 'brain-eating amoeba', is a free-living amoeba capable of living in the environment, especially in bodies of warm water. Three distinct life stages exist: amoeboid trophozoite, flagellated trophozoite, and cyst. Intheamoeboidtrophozoitephasecelldivision occurs by mitosis. Thesizesofthetrophozoite forms range from 15 to 25 urn. Like most protists, the trophozoites form cysts under unfavorable conditions. The cysts measure between 7 and 10 urn and are covered by a thin double wall with one or two pores. It is possible that all three phases of N. fowleri reach or invade the human nasal mucosa, but only the trophozoite amoeboid form has been isolated in cerebrospinal fluid or tissue. It is feasible that, upon reaching the nasal area, the cyst quickly becomes a trophozoite and forms flagella before it invades the nasal and olfactory nerve tissue. Infection occurs when individuals swim or dive in /Vaeg/er/a-contaminated warm freshwater bodies such as lakes or rivers. Early stages of PAM Naegleriapores W?°o Late stages of PAM «... O v„U.,t.nl,i. ng prate.™ Antibodies ■h tmm = m 1 »,,„,»,„,, C.m,i™,« 848 Trends in Parasitology, October 2019, Vol. 35, No. 10 © 2019 Elsevier Ltd. All rights reserved. ® key facts: N. fowleri has been isolated from both soils and different types of water bodies, such as swimming pools, thermal waters, tap water, and lakes. N. fowleri can cause an aggressive infection of the human central nervous system (CNS), which is called primary amoebic meningoencephalitis (PAM). Most reported cases of PAM patients present a history of contact with N. fowleri-contaminated water bodies in the week prior to the appearance of the first symptoms. disease facts: N. fowleri penetrates through the nasal passage, where it adheres to the olfactory nerves and makes its way to the brain through the cribriform plate. The amoeba attacks the olfactory bulb, producing an inflammatory process and leading to brain infection, which is fatal in more than 97% of cases. Clinical symptoms are characterized by the sudden onset of bifrontal or bitemporal headache, high fever, stiff neck, followed by nausea, vomiting, and irritability. In advanced stages of the infection, photophobia and neurological alterations are observed, such as lethargy, seizures, confusion, coma, diplopia, or strange behavior, which leads to death within a week. The treatment is based on the use of amphotericin B in combination with other drugs such as rifampin, fluconazole, azithromycin, miltefosine, and dexamethasone. taxonomy and classification: phylum: Percolozoa class: Heterolobosea order: Schizopyrenida family: Vahlkampfiidae genus: Naegleria species: N. fowleri Trends in Parasitology https://doi.Org/10.1016/j.pt.2019.06.011 "Correspondence: jpinero@ull.edu.es (J.E. Piňero) and jmlorenz@ull.edu.es (J. Lorenzo-Morales). CelP REVIEWS Trends in Parasitology I Parasite of the Month Acknowledgments This work was supported by grant PI18/01380 of Institute de Salud Carlos III and FEDER. The figure showing the early and late stages of PAM was adapted from Martinez-Castillo ef a/., J. Med. Microbiol., 2016 (Literature No. 4) with permission. Resources www.cdc.gov/dpdx/freelivingamebic/ www.cdc.gov/parasites/naegleria/general.html www.jordansmelskifoundation.org/ Literature 1. Bellini, N.K. ef a/. (2018) The therapeutic strategies against Naegleria fowleri. Exp. Parasitol. 187, 1-11 2. Cooper, A.M. ef a/. (2019) Killer amoebas: Primary amoebic meningoencephalitis in a changing climate. JAAPA 32, 30-35 3. Garcia, D.S. ef a/. (2018) Outbreaks associated with untreated recreational water - United States, 2000-2014. Morbil. Mortal. Wkly Rep. 67, 701-706 4. Martinez-Castillo, M. ef a/. (2016) Naegleria fowleri after 50 years: is it a neglected pathogen? J. Med. Microbiol. 65, 885-896 5. Marciano-Cabral, F. (1988) Biology of Naegleria spp. Microbiol. Rev. 52, 114-133 6. Siddiqui, R. ef a/. (2016) Biology and pathogenesis of Naegleria fowleri. Acta Trop. 164, 375-394 7. Visvesvara, G.S. (2010) Free-living amebae as opportunistic agents of human disease. J. Neuroparasitol. 1, N100802 ^^^^|| Trends in Parasitology, October 2019, Vol. 35, No. 10 © 2019 Elsevier Ltd. All rights reserved. https://doi.Org/10.1016/j.pt.2019.06.011 849 REVIEWS