How do naegleria fowleri reproduce

The first PAM infections were reported in in Australia. The ameba identified caused a fatal infection in and turned out to be a new species that has since been named Naegleria fowleri after one of the original authors of the report, M. Fowler 1.

The first infections in the U. Subsequent investigations in Virginia using archived autopsy tissue samples identified PAM infections that had occurred in Virginia as early as 3. Naegleria fowleri has 3 stages in its life cycle: cyst 1 , trophozoite 2 , and flagellate 3. The only infective stage of the ameba is the trophozoite. The trophozoites replicate by binary division during which the nuclear membrane remains intact a process called promitosis 4. Trophozoites infect humans or animals by penetrating the nasal tissue 5 and migrating to the brain 6 via the olfactory nerves causing primary amebic meningoencephalitis PAM.

They revert back to the trophozoite stage when favorable conditions return 1. Naegleria fowleri trophozoites are found in cerebrospinal fluid CSF and tissue, while flagellated forms are occasionally found in CSF.

Cysts are not seen in brain tissue. If the environment is not conducive to continued feeding and growth like cold temperatures, food becomes scarce the ameba or flagellate will form a cyst. It has a smooth, single-layered wall with a single nucleus. Cysts are environmentally resistant in order to increase the chances of survival until better environmental conditions occur 2. Naegleria fowleri is normally found in the natural environment and is well adapted to surviving in various habitats, particularly warm-water environments.

Although the trophozoite stage is relatively sensitive to environmental changes, the cysts are more environmentally hardy. There are no means yet known that would control natural Naegleria fowleri levels in lakes and rivers. Their work on amebo -flagellates was quite ground-breaking as it provided an example of how one protozoa can effectively live both freely in the environment, and in a human host. In the years since a total of cases have been confirmed in a variety of countries Table 2.

In Dr. Butt termed the infection resulting from N. An interesting retrospective study found the likely first recorded case of PAM occurred in Ireland in St. Symmers , Morphology Martinez, There are three distinct morphological stages in the life cycle of N.

The trophozoite is the infective stage of the amoeba. Trophozoites reproduce by binary fission and are motile due to round processes filled with granular cytoplasm called lobopodia. When free-living, trophozoites use a structure called a food-cup Figure 1D to ingest bacteria and yeast — in a human host this same structure is used to ingest red blood cells, white blood cells, and tissue.

Another important structure is the contractile vacuole. This vacuole ruptures, empties, and reforms in a rapid process and is valuable in recognizing amebic trophozoites among other tissue cells. In just minutes to a few hours trophozoites differentiate into bi-flagellated cells.

This change can be induced by placement of trophozoites from culture into distilled water. Additionally, in unfavorable conditions low nutrient, crowding, cold temperatures, desiccation , N. Figure 1: Stages of N. Life Cycle CDC, The life cycle of N. In a warm, high nutrient, aquatic environment the trophozoite stage predominates. This is the reproductive stage and a trophozoite that undergoes promitosis results in two trophozoites.

If pH or ionic changes occur surrounding the organism, the trophozoite can transition to the more mobile flagellated form. If the environment becomes depleted of nutrients, cold, or dry the trophozoite can encyst to survive the unfavorable conditions. Cysts and trophozoites can enter the human through nasal passages, usually related to water activities. Trophozoites are infective, and their penetration of the nasal mucosa and subsequent migration to the brain results in PAM. Naegleria fowleri have been isolated from soil, swimming pools, cooling towers, hospital hydrothermal pools, and sewage sludge Visvesvara et al.

Most reported infections occur after swimming in warm bodies of water. Introduction of trophozoites to the nasal passages of humans is the first step in Naegleria fowleri infection. There are no animal reservoirs of N. The bodies of water and soil contaminated with N. Incubation Period. The period between initial contact with the pathogenic N. Once symptomatic, however, progression of PAM is rapid and often fatal Ma et al.

Pathogenesis Ma et al. The portal of entry of N. After entry, the trophozoite penetrates the nasal mucosa and migrates along mesaxonal spaces of unmyelinated olfactory nerves terminating at the olfactory bulb in the subarachniod space. This space is quite vascularized and is a route of dissemination of trophozoites to other areas of the CNS. There are histopathological characteristics of the invaded tissues — for example the olfactory mucosa and olfactory bulb have hemorrhagic necrosis.

An important note is that trophozoites only are found in PAM lesions. Clinical Presentation in Humans Ma et al. After the initial incubation period, N. Sometimes early in the progression of disease changes in smell parosmia and taste ageusia occur as trophozoites damage the olfactory system.

After early signs described above, progression to coma and seizures is rapid — over a period of days. When this species is in the trophozoite phase the species will change the shape and size of the body frequently and is considered a free living amoeba Martinez and Govinda The cytoplasm of this lineage is granular and contains a great deal of vacuoles within the cytoplasm, it also contains a nucleus Martinez and Govinda The way N.

Lastly the N. This species moves in a slug-like motion Schuster and when N. At the anterior end of the N. When this species is in flagellate form N. In conclusion N. This species reproduces by binary fission and reproduces better in warmer temperatures. The certain conditions of an environment are what determine which stage the organism will be in.