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Updated: Jul 14, 2026
Clinical Examination Protocol to Detect Atypical and Classical Scrapie in Sheep
Published on: January 19, 2014
Experimental Naegleria fowleri meningoencephalitis in sheep: light and electron microscopic studies
Abstract:
A sheep infected intranasally with Naegleria fowleri of human origin died 7 days after inoculation. The olfactory lobes were distinctly soft and friable. Histologic findings indicated suppurative leptomeningitis and hemorrhagic necrosis in the olfactory lobes. Protozoa were disseminated in the necrotic areas, particularly in perivascular locations; vasculitis was also observed. Meningitis and perivascular cuffing with lymphocytes were evident in the cerebrum, cerebellum, pons, medulla, and cervical spinal cord. Electron microscopy disclosed trophozoites only in the olfactory lobes. The amebae contained a central nucleus with a distinct, electron-dense nucleolus. The cytoplasm contained myelinated figures, lipid-like vacuoles, open vesicles, electron-dense granules, mitochondria, numerous free ribosomes, scant rough endoplasmic reticulum, and occasionally a phagocytized erythrocyte. Trophozoites were grouped close to arterioles, except when phagocytized by a neutrophil or endothelial cell.
Insights
Naegleria fowleri, a brain-eating amoeba, caused fatal meningitis and necrosis in sheep after intranasal infection. The study details the amoeba
Area of Science:
- Neuroscience
- Pathology
- Parasitology
Background:
- Naegleria fowleri is a free-living amoeba known to cause primary amebic meningoencephalitis (PAM) in humans.
- Intranasal inoculation is a common route of infection for Naegleria fowleri.
Purpose of the Study:
- To investigate the pathological effects of Naegleria fowleri infection in a sheep model.
- To characterize the histological and ultrastructural changes associated with Naegleria fowleri infection.
Main Methods:
- Intranasal inoculation of a sheep with Naegleria fowleri of human origin.
- Necropsy and gross examination of the brain and spinal cord.
- Histopathological examination of central nervous system tissues.
- Electron microscopy of olfactory lobe tissues.
Main Results:
- Sheep died 7 days post-inoculation, exhibiting soft and friable olfactory lobes.
- Histology revealed suppurative leptomeningitis, hemorrhagic necrosis in olfactory lobes, vasculitis, and perivascular cuffing throughout the CNS.
- Naegleria fowleri trophozoites were identified in necrotic areas, particularly in perivascular locations within the olfactory lobes.
- Electron microscopy confirmed the presence of Naegleria fowleri trophozoites in the olfactory lobes, detailing their ultrastructural features.
Conclusions:
- Naegleria fowleri infection in sheep leads to severe meningoencephalitis and widespread CNS pathology.
- The sheep model effectively replicates key pathological features of human primary amebic meningoencephalitis.
- Olfactory lobes are a primary target site for Naegleria fowleri, with trophozoites found in perivascular locations.
