26.4 Fungal and Parasitic Diseases of the Nervous System
3 min read•june 18, 2024
Fungal and parasitic infections can wreak havoc on our nervous system. From causing to attacking the brain, these microbes are no joke. Understanding how they invade and impact our central nervous system is crucial for diagnosis and treatment.
Parasites like , transmitted by tsetse flies, can lead to sleeping sickness. This nasty infection progresses from fever and headaches to confusion and even coma if left untreated. Recognizing the symptoms and lifecycle of these parasites is key to combating their neurological effects.
Fungal Diseases of the Nervous System
Common fungi and parasites in nervous system
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- Cryptococcus neoformans
- Encapsulated yeast surrounded by a
- Causes inflammation of the (membranes covering the brain and spinal cord)
- Naegleria fowleri
- Free-living found in warm freshwater (lakes, rivers, hot springs)
- Causes rapidly progressive and often fatal infection of the brain
-
- Free-living amoeba found in soil, water, and air
- Causes chronic, progressive infection of the central nervous system
-
- Obligate intracellular protozoan parasite that infects cats as definitive hosts
- Causes life-threatening condition in individuals (HIV/AIDS)
- Demonstrates , preferentially infecting neural tissues
Cryptococcal meningitis: key aspects
- Transmission
- Inhalation of spores from the environment, particularly from soil contaminated with bird droppings (pigeons)
- Spores enter the lungs and disseminate to the central nervous system via the bloodstream
- Symptoms
- Headache often severe and persistent
- Fever usually low-grade
- Neck stiffness due to meningeal irritation
- Altered mental status confusion, lethargy, or personality changes
- Photophobia sensitivity to light
- Nausea and vomiting due to increased intracranial pressure
- Diagnosis
- Lumbar puncture and ###Cerebrospinal_Fluid_()_0### analysis
- Positive reveals encapsulated yeast cells
- Positive detects capsular antigens
- Culture of CSF on yields mucoid colonies of Cryptococcus neoformans
- Radiographic imaging (CT or MRI) may show meningeal enhancement or (fungal granulomas in the brain)
- Lumbar puncture and ###Cerebrospinal_Fluid_()_0### analysis
Neuroinvasion and Host Factors
- : Pathogens use various mechanisms to cross this protective barrier
- : Increases susceptibility to opportunistic infections of the nervous system
- : Some nervous system pathogens are transmitted from animals to humans
Parasitic Diseases of the Nervous System
Trypanosoma brucei lifecycle and effects
- Life cycle
- Transmitted by the bite of an infected ()
- enter the bloodstream and lymphatics and multiply extracellularly
- Parasites cross the and invade the central nervous system
- Trypomastigotes continue to multiply in the blood, lymph, and cerebrospinal fluid
- Neurological effects
- (sleeping sickness)
- caused by more acute and rapidly progressive
- caused by more chronic and slowly progressive
- Early stage (hemolymphatic stage)
- Fever often intermittent
- Headache due to meningeal irritation
- Lymphadenopathy particularly posterior cervical lymph nodes ()
- enlargement of the liver and spleen
- Late stage (neurological stage)
- inflammation of the and brain
- Progressive confusion and cognitive impairment
- Personality changes apathy, irritability, or aggression
- Reversal of sleep-wake cycle daytime somnolence and nighttime insomnia
- Seizures generalized or focal
- Coma terminal stage if left untreated
- Diagnosis often involves to detect parasites and assess CNS involvement
- (sleeping sickness)
Other Parasitic Infections
- : Caused by larval cysts of the tapeworm in the brain
Key Terms to Review (72)
Acanthamoeba spp.: Acanthamoeba spp. are free-living amoebae that can cause serious infections in the human nervous system, particularly a rare but severe condition known as granulomatous amoebic encephalitis (GAE). These opportunistic parasites are ubiquitous in the environment and can pose a threat to immunocompromised individuals.
African sleeping sickness: African sleeping sickness, also known as human African trypanosomiasis, is a parasitic disease caused by protozoa of the genus Trypanosoma. It is transmitted by the bite of an infected tsetse fly.
African trypanosomiasis: African trypanosomiasis, also known as sleeping sickness, is a parasitic disease caused by the protozoan Trypanosoma brucei and transmitted by the tsetse fly. It primarily affects the nervous system and can lead to severe neurological complications if left untreated.
Albendazole: Albendazole is a broad-spectrum anthelmintic medication used to treat a variety of parasitic worm infestations. It works by inhibiting the microtubule synthesis in parasites, leading to their death.
Amoeba: Amoeba are single-celled eukaryotic organisms characterized by their ability to change shape and move using pseudopodia. Certain amoebae can cause severe infections in the human nervous system.
Amoebic keratitis: Amoebic keratitis is a rare but serious infection of the cornea caused by the free-living amoeba Acanthamoeba. It primarily affects contact lens wearers and can lead to severe pain, vision impairment, and even blindness if untreated.
Antigenic variation: Antigenic variation is the process by which a pathogen alters its surface proteins to evade a host's immune response. This mechanism enables pathogens to persist in the host and cause chronic or recurrent infections.
Balamuthia: Balamuthia is a free-living amoeba that can cause a serious infection known as Balamuthia mandrillaris. This pathogen primarily affects the central nervous system, leading to granulomatous amoebic encephalitis (GAE).
Blood-brain barrier: The blood-brain barrier (BBB) is a selective permeability barrier that separates the circulating blood from the brain and extracellular fluid in the central nervous system. It protects the brain from harmful substances while allowing essential nutrients to pass through.
Blood-Brain Barrier: The blood-brain barrier is a highly selective semipermeable membrane that separates the circulating blood from the brain and extracellular fluid in the central nervous system. It acts as a protective barrier, regulating the passage of substances between the bloodstream and the brain.
Blood-Brain Barrier Penetration: The blood-brain barrier is a highly selective semipermeable membrane that separates the circulating blood from the brain and central nervous system (CNS). Blood-brain barrier penetration refers to the ability of substances, such as drugs or pathogens, to cross this barrier and enter the CNS.
Cerebrospinal Fluid (CSF): Cerebrospinal fluid (CSF) is a clear, colorless fluid that circulates through the brain's ventricles, the central canal of the spinal cord, and the space between the arachnoid membrane and the pia mater surrounding the brain and spinal cord. It provides cushioning and protection for the central nervous system.
Cerebrospinal Fluid Analysis: Cerebrospinal fluid (CSF) analysis is a diagnostic procedure that involves the collection and examination of the fluid that surrounds the brain and spinal cord. This analysis is crucial in the context of fungal and parasitic diseases of the nervous system, as it can provide valuable insights into the underlying pathological processes affecting the central nervous system.
Cryptococcal Antigen Test: The cryptococcal antigen test is a diagnostic tool used to detect the presence of cryptococcal antigens, which are proteins released by the fungus Cryptococcus, in a person's body fluids. This test is particularly important in the context of fungal and parasitic diseases of the nervous system, as Cryptococcus is a common cause of life-threatening infections, such as cryptococcal meningitis, that primarily affect the central nervous system.
Cryptococcal Meningitis: Cryptococcal meningitis is a serious fungal infection of the membranes surrounding the brain and spinal cord, caused by the yeast-like fungus Cryptococcus neoformans. It primarily affects individuals with weakened immune systems, such as those living with HIV/AIDS or undergoing immunosuppressive therapies.
Cryptococcomas: Cryptococcomas are focal lesions or granulomas that can develop in the brain or other organs as a result of a Cryptococcus fungal infection. These lesions are a characteristic feature of cryptococcosis, a serious fungal disease that primarily affects the central nervous system.
Cryptococcus neoformans: Cryptococcus neoformans is an encapsulated yeast that primarily causes infections in immunocompromised individuals. It is notable for causing severe respiratory and central nervous system infections.
CSF: Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the brain and spinal cord. It cushions the central nervous system and provides vital nutrients while removing waste products.
Cysticerci: Cysticerci are the larval stage of the pork tapeworm, Taenia solium, which can cause serious infections in humans when ingested through undercooked pork or contaminated water. These larvae can migrate to various tissues, including the nervous system, leading to neurocysticercosis.
Dexamethasone: Dexamethasone is a potent corticosteroid with anti-inflammatory and immunosuppressant properties. It is often used to treat inflammation associated with nervous system infections, including those caused by fungal and parasitic pathogens.
East African trypanosomiasis: East African trypanosomiasis, also known as East African sleeping sickness, is a parasitic disease caused by Trypanosoma brucei rhodesiense. It primarily affects the central nervous system, leading to severe neurological symptoms and can be fatal if untreated.
Eflornithine: Eflornithine is a drug used to treat certain parasitic infections, notably African trypanosomiasis (sleeping sickness). It inhibits ornithine decarboxylase, an enzyme crucial for parasite proliferation.
Epilepsy: Epilepsy is a neurological disorder characterized by recurrent, unprovoked seizures due to abnormal electrical activity in the brain. It can be influenced by various factors, including infections and infestations.
Flucytosine: Flucytosine is an antifungal medication used to treat serious fungal infections. It works by inhibiting fungal DNA and RNA synthesis.
Folinic acid: Folinic acid, also known as leucovorin, is a form of folate used in the body to aid DNA synthesis and repair. It is often utilized as an adjuvant therapy for certain infections and chemotherapeutic agents.
Glossina spp.: Glossina spp. refers to a genus of blood-feeding flies, commonly known as tsetse flies, that are vectors for the parasitic diseases trypanosomiasis in humans and animals. These flies are found exclusively in sub-Saharan Africa and play a crucial role in the transmission of these devastating neurological disorders.
Granulomatous amoebic encephalitis (GAE): Granulomatous amoebic encephalitis (GAE) is a rare but severe brain infection caused by free-living amoebae, such as Acanthamoeba spp. and Balamuthia mandrillaris. It primarily affects immunocompromised individuals and leads to chronic inflammation of the brain.
Granulomatous Amoebic Encephalitis (GAE): Granulomatous amoebic encephalitis (GAE) is a rare and severe infection of the central nervous system caused by free-living amoebae, typically Acanthamoeba or Balamuthia species. It primarily affects immunocompromised individuals and can lead to a devastating, often fatal, inflammation of the brain and surrounding tissues.
Hepatosplenomegaly: Hepatosplenomegaly is the simultaneous enlargement of both the liver (hepato-) and spleen (splenomegaly). This condition is often associated with various fungal and parasitic diseases that can affect the nervous system.
Human African trypanosomiasis: Human African trypanosomiasis, also known as sleeping sickness, is a parasitic disease caused by Trypanosoma brucei. It primarily affects the central nervous system and is transmitted by the tsetse fly.
Immunocompromised: Immunocompromised refers to a weakened or impaired immune system, which reduces the body's ability to fight off infections and diseases. This condition can make individuals more susceptible to viral, fungal, and parasitic infections, including those that affect the gastrointestinal tract and nervous system.
Immunosuppression: Immunosuppression refers to the reduction or inhibition of the normal immune response, either through natural means or through medical intervention. This can have significant implications in various areas of health and disease.
India Ink Staining: India ink staining is a simple and inexpensive technique used in microbiology to visualize and identify certain microorganisms, particularly fungi and parasites, in clinical samples. The dark, opaque India ink provides contrast against the clear background, allowing for the easy detection of structures that would otherwise be difficult to see.
Melarsoprol: Melarsoprol is an arsenic-based medication primarily used to treat late-stage African trypanosomiasis, also known as sleeping sickness. It is effective against the Trypanosoma brucei parasite that invades the central nervous system.
Meninges: Meninges are three protective membranes that envelop the brain and spinal cord. They consist of the dura mater, arachnoid mater, and pia mater.
Meninges: The meninges are the protective membranes that surround the brain and spinal cord. They play a crucial role in the anatomy of the nervous system and can be affected by various fungal and parasitic diseases.
Meningitis: Meningitis is an inflammation of the protective membranes covering the brain and spinal cord, known as the meninges. It can be caused by bacterial, viral, fungal, or parasitic infections.
Meningoencephalitis: Meningoencephalitis is the inflammation of both the meninges and the brain tissue, often caused by infections such as bacteria, viruses, fungi, or parasites. It can lead to severe neurological damage and requires prompt medical attention.
Meningoencephalitis: Meningoencephalitis is a severe inflammation of the brain (encephalitis) and the membranes (meninges) that surround it. This condition can be caused by various infectious agents, including viruses, bacteria, fungi, and parasites, and can lead to significant neurological complications if not properly treated.
Miltefosine: Miltefosine is an antimicrobial agent effective against certain protozoal infections, particularly leishmaniasis and amoebic meningoencephalitis. It works by disrupting cell membrane integrity and inhibiting cellular functions of the parasites.
Naegleria fowleri: Naegleria fowleri is a free-living amoeba that can cause a rare and devastating infection of the central nervous system known as primary amebic meningoencephalitis (PAM). It is a parasite that primarily affects the nervous system, making it a key topic within the context of Fungal and Parasitic Diseases of the Nervous System.
Neurocysticercosis: Neurocysticercosis is a parasitic infection of the central nervous system caused by the larval stage of the pork tapeworm, Taenia solium. It is a leading cause of acquired epilepsy in endemic regions.
Neurocysticercosis: Neurocysticercosis is a parasitic infection of the central nervous system caused by the larval stage of the pork tapeworm, Taenia solium. It is a significant public health concern, particularly in developing countries where the parasite is endemic.
Neuroinvasion: Neuroinvasion refers to the ability of certain pathogens, such as bacteria, viruses, fungi, and parasites, to infiltrate and invade the nervous system, causing various neurological diseases and disorders. This process is a critical factor in understanding the pathogenesis and progression of many infectious diseases that target the central and peripheral nervous systems.
Neuromycoses: Neuromycoses are fungal infections that affect the nervous system, including the brain and spinal cord. These infections can cause serious neurological damage and require prompt diagnosis and treatment.
Neurotoxoplasmosis: Neurotoxoplasmosis is a severe infection of the central nervous system caused by the parasite Toxoplasma gondii. It typically occurs in immunocompromised individuals, such as those with AIDS.
Neurotropism: Neurotropism refers to the ability of certain pathogens, such as viruses, bacteria, fungi, and parasites, to specifically target and infect the nervous system. These pathogens possess the unique capability to recognize, bind, and invade nerve cells, leading to various neurological diseases and disorders.
Pentamidine: Pentamidine is an antimicrobial drug used primarily to treat certain parasitic and fungal infections. It is often employed when other treatments are ineffective or contraindicated.
Polysaccharide Capsule: A polysaccharide capsule is a protective layer surrounding certain bacterial and fungal cells, composed of complex carbohydrate molecules. This structure plays a crucial role in the pathogenesis and virulence of various infectious diseases affecting the nervous system.
Polysaccharide capsules: Polysaccharide capsules are protective layers composed of carbohydrate molecules that surround the cell walls of certain bacteria. They play a critical role in bacterial virulence by helping the bacteria evade the host's immune response.
Pork tapeworm: Pork tapeworm, or Taenia solium, is a parasitic flatworm that can cause neurocysticercosis when its larvae infect the human brain. It is primarily acquired by consuming undercooked pork containing cysticerci.
Praziquantel: Praziquantel is an antiparasitic medication used to treat infections caused by various species of parasitic worms, specifically schistosomiasis and liver flukes. It works by causing severe spasms and paralysis of the worms' muscles, leading to their death.
Primary amoebic meningoencephalitis (PAM): Primary amoebic meningoencephalitis (PAM) is a rare but often fatal brain infection caused by the free-living amoeba Naegleria fowleri. It typically occurs when contaminated water enters the nose and reaches the brain.
Primary Amoebic Meningoencephalitis (PAM): Primary Amoebic Meningoencephalitis (PAM) is a rare and severe infection of the brain and central nervous system caused by a free-living amoeba known as Naegleria fowleri. This parasite can invade the brain through the nasal cavity and cause a rapidly progressing and often fatal form of meningoencephalitis.
Sabouraud dextrose agar: Sabouraud dextrose agar is a selective and differential culture medium used for the isolation and cultivation of fungi, particularly those that may cause fungal infections of the nervous system. It is formulated to support the growth of a wide range of fungi while inhibiting the growth of bacteria.
Sulfadiazine: Sulfadiazine is a sulfonamide antibiotic used to treat various bacterial infections by inhibiting the synthesis of folic acid in bacteria. It is often combined with other drugs to enhance its efficacy.
Suramin: Suramin is a medication used to treat parasitic diseases such as African trypanosomiasis (sleeping sickness). It works by inhibiting enzymes necessary for the parasite's survival.
T. b. gambiense: T. b. gambiense is a subspecies of the protozoan parasite Trypanosoma brucei, which is the causative agent of West African trypanosomiasis, also known as Gambian sleeping sickness. This parasite primarily infects humans and is transmitted through the bites of infected tsetse flies.
T. b. rhodesiense: T. b. rhodesiense is a subspecies of the protozoan parasite Trypanosoma brucei, which is the causative agent of African sleeping sickness or human African trypanosomiasis. This parasite is primarily transmitted by the tsetse fly and primarily affects the nervous system, leading to the characteristic symptoms of the disease.
Taenia solium: Taenia solium is a parasitic tapeworm primarily found in pigs and humans. It can cause neurocysticercosis, a serious nervous system infection.
Toxoplasma gondii: Toxoplasma gondii is an intracellular parasitic protozoan that can infect a wide range of warm-blooded animals, including humans. It is the causative agent of toxoplasmosis, a disease that can have significant health implications, particularly for pregnant women and individuals with compromised immune systems.
Toxoplasmic Encephalitis: Toxoplasmic encephalitis is a life-threatening infection of the brain caused by the parasite Toxoplasma gondii. It primarily affects individuals with weakened immune systems, such as those with HIV/AIDS, cancer, or who have undergone organ transplants.
Trypanosoma brucei: Trypanosoma brucei is a parasitic protozoan that is the causative agent of African trypanosomiasis, also known as sleeping sickness. It is a hemoflagellate parasite that infects the circulatory and lymphatic systems, as well as the central nervous system in humans and other mammals.
Trypomastigotes: Trypomastigotes are a life stage of certain parasitic protozoa, such as Trypanosoma cruzi, the causative agent of Chagas disease. They are flagellated, spindle-shaped cells that are adapted for transmission between hosts and invasion of host cells.
Tsetse fly: The tsetse fly is a blood-feeding insect known for transmitting Trypanosoma brucei, the parasite responsible for African sleeping sickness. It primarily affects the central nervous system, leading to severe neurological symptoms and potentially fatal outcomes.
Tsetse Fly: The tsetse fly is a blood-feeding insect that serves as the vector for the parasitic protozoa that cause African trypanosomiasis, also known as sleeping sickness, in humans and nagana in animals. It is a key component in the transmission of these parasitic infections within the circulatory and lymphatic systems.
Undulating fever: Undulating fever is a type of fever characterized by periods of high temperature followed by periods of normal temperature, typically seen in chronic infections. It can be associated with certain parasitic and fungal diseases affecting the nervous system.
Virulence factor: A virulence factor is a molecule or structure produced by a pathogen that contributes to its ability to cause disease. These factors enable the pathogen to invade the host, evade the immune system, and obtain nutrients from the host.
West African trypanosomiasis: West African trypanosomiasis, also known as sleeping sickness, is a parasitic disease caused by Trypanosoma brucei gambiense. It primarily affects the central nervous system leading to severe neurological symptoms.
Winterbottom’s sign: Winterbottom’s sign is the swelling of lymph nodes in the posterior cervical region, commonly associated with African trypanosomiasis (sleeping sickness). It serves as a clinical indicator of the early stage of this parasitic infection.
Winterbottom's sign: Winterbottom's sign is a clinical finding associated with the parasitic infection of the nervous system caused by the trypanosome protozoan Trypanosoma brucei gambiense, which is the causative agent of West African sleeping sickness. It refers to the swelling of lymph nodes, particularly those located at the back of the neck.
Zoonotic Transmission: Zoonotic transmission refers to the process by which infectious diseases are transmitted from animals to humans. This term is particularly relevant in the context of various microbiology topics, as it highlights the importance of understanding the complex interplay between different species and the potential for disease spread across the animal-human interface.