Flashcards in Exam #7: Fungal & Parasitic Infections of the CNS Deck (52):
What is the leading cause of fungal meningitis?
What two systemic fungi most commonly cause meningitis?
How are the systemic mycoses acquired?
Inhalation of fungal elements
What form of Coccidioides immitis infects man?
Filamentous mold infects man, which is then converted to yeast in tissues during infection
*Remember, "mold in the cold, yeast in the heat"
What form of crytococcus neoformans infections man?
Note that this is particular to cryptococcus neoforms, it is an encapsulated yeast BOTH in the environment & in infected individuals
Where is Coccidioidomyocsis endemic? When do most endemics occur?
- San Joaquin Valley of California & in Southern Arizona i.e. Southwestern US
- Drought-rain-drought pattern with large numbers of fungal elements present in blowing dust
What form of Coccidioides is found in man?
Spherule= a multinucleated structure that produces hundreds of single nucleated spores
What clinical syndromes are caused by Coccidiomycosis?
- Pulmonary disease= mild to moderate flu-like illness that largely resolves spontaneously
- Coccidial meningitis= chronically developing headache, fever, & stiff neck
*Note that in comparison to bacterial meningitis, fungal meningitis is has a SLOW onset
How is Coccidiomycosis diagnosed?
- Antigen detection in CSF
How is Coccidiomycosis treated?
How is cioccidial meningitis diagnosed?
- Mainly based on history
- Antigen detection in CSF
- Serology i.e. antibody presence, which has limited utility in areas where coccidiomyocses is common
Note that cultivation is rarely successful
Where is cyrptococcus neoformans found?
Abundant in soil contaminated with bird droppings
What clinical syndromes are caused by Cryptococcus neoformans?
- Pulmonary Disease= asymptomatic to mild flu-like illness that is self-resolving
- Cryptococcal meningitis= *the most common cause of fungal meningitis
Describe the presentation of cryptococcal meningitis.
- Chronic onset of typical meningeal symptoms (weeks-->months)
- Intermittent headache, irritability, dizziness, & other CNS findings
How does the presentation of cryptococcal meningitis differ in AIDS & HIV+ patients?
Acute onset instead of chronic onset
How is Cryptococcosis diagnosed?
India ink i.e. stain that reveals encapsulated yeast
How is cryptococcal meningitis treated?
Amphotericin B & Flourocytosine
What additional therapy is needed following cryptococcal meningitis in AIDS patients?
What causes rhinocerebral mucromycosis? What patient population is it most common in?
- Zygomycoses that begins as sinusitis that eventually spreads into the eye & CNS
- Most common in diabetic patients
What are the causative organisms of rhinocerebral mucromycosis?
What are the features of the Zygomycetes? How is zygomycoses (mucormycosis) diagnosed?
- Observation of non-septate (aspetate) hyphae
- Observed in blood vessels branching at 90 degrees
What is Entamoeba histolytica?
Parasite that causes amoebic dysentery & brain abscesses
What is Trypanosoma brucei?
African trypanosome that causes sleeping sickness
What is plasmodium falciparum?
Causative organism of cerebral malaria
What are opportunistic amoeba?
Protozoa/ amoebas that are normally found in the environment & occasionally infect humans
What are the three genera of opportunistic amoeba?
- Thought to normally reside in fresh water & accidental parasites of man
- All cause fatal infections in man
What is PAM?
Primary emebic meningoencephalitis that causes:
What causes PAM?
What is PAM associated with?
How is PAM diagnosed?
Observation of trophozoite forms of amoeba in the CSF
How is PAM treated?
There has been some success in treatment with Amphotericin B, but infection is usually fatal
What is GAE? How does GAE compare to PAM?
Granulomatous amoebic encephalitis that causes a SLOWER onset of:
What causes GAE?
What is Acanthamoeba keratitis?
Chronic amoebic infection of the cornea that is associated with contact lens use
What is Toxoplasmosis?
- One of the most common parasitic infections in humans & animals
- Most infections are asymptomatic
- Becomes a problem in the immunosuppressed--> encephalitis
What causes Toxoplasmosis? What patient populations are at risk for Toxoplasmosis?
- Congenital infection to child
Describe the lifecycle of Toxoplasma gondii. How is Toxoplasmosis transmitted to humans?
Humans acquire Toxoplasmosis by eating tissue cysts in undercooked meat or ingestion of oocysts in contaminated soil.
- A single tissue cyst is enough to cause disease, and these are readily found in pork and lamb in the US
- Soil contamination by cat feces is a major source of oocysts
*Thus, contaminated meat= tissue cyst. Cat feces= oocysts. This is why pregnant women are instructed to avoid cat litter boxes.
What are the outcomes of congenitally acquired Toxoplasmosis?
- Mental retardation
- Neurological disorders
What are the recommendations for pregnant women because of Toxoplasmosis?
- Avoid cats/ cat liter
*Concern is about a woman having a newly acquired infection during the first trimester
- If maternal infection in 1st trimester= 15-25% chance of SEVERE disease
- If maternal infection in 3rd trimester= 65% chance of less severe disease
What are the symptoms of Toxoplasmosis?
- Asymptomatic mostly
- Symptoms are "flu-like"
- Eventually walls off & forms a bradyozite filled cyst
*If the immune system is weakened, reactivation can occur
How is Toxoplasmosis diagnosed?
- Serologic testing
- Congenital infection tested with PCR for amniotic fluid
- Maternal= IgM (new infection) or rising IgG titer
*ring-enhancing lesion on imaging studies*
What is the importance of rising IgM & IgG titers of toxoplasmosis?
Such titers indicate that an acute infection is likely
How is toxoplasmosis prevented?
- Cooking meat thoroughly
- Avoid contact with cat feces, especially if pregnant or immunosuppressed
How is toxoplasmosis treated?
Immunocompetent= rarely require treatment
Pregnant mother= early treatment to prevent transmission
Children= treatment for 1 year
Immunocompromised= prophylactic therapy
What is the name of the pork tapeworm?
What form of Taenia solium causes disseminated infection in man?
- Ingestion of embyronated eggs from an infected individual
- Ingested eggs hatch in the intestine & release larvae that enter circulation & travel to site where they encyst
- Encysting causes space filling lesions that induce localized inflammation
What is the name of the infection of the brain caused by Taenia solium?
Who is at risk for Neurocyticercosis?
Endemic to South America; increasing prevalence in immigrant families in the US
How is Neurocyticercosis diagnosed?
- "Swiss cheese" morphology on imaging
What is visceral larval migrans?
- Infection of man by ascarid worms that normally infect & cause intestinal disease in dogs & cats
- Transmission to man is by ingestion of eggs
- Eggs hatch and larvae migrate to numerous body sites, die, and then a granuloma forms
How is visceral larval migrans diagnosed?
*Note that eggs will NOT be in feces of humans