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40 Cards in this Set
- Front
- Back
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Which amoeba is responsible for Primary Amebic Meningoencephalitis (PAM)?
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Naegleria fowleri
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What is the incubation period, prodromal signs, and clinical presentation of Naegleria fowleri?
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Incubation period: 3-7 days
Prodromal signs: prefrontal headache and fever Progresses to: classic signs of meningitis, nausea, vomiting, high fever, headache, stiff neck, confusion, coma Death usually occurs 3-6 days after onset of serious symptoms |
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What is the transmission of N. fowleri?
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Entry through olfactory nerves
Swimming/diving in warm, turbid water Neti pots - introducing water into nasal cavity |
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T or F: Only trophozoites of N. fowleri are infective or found in the patient.
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True
Flagellated forms may be found in CSF but not routinely N. fowleri encysts in the winter |
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How is PAM diagnosed?
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Microscopy of fresh CSF, nasal discharge, tissue biopsy - motile trophozoites with broad pseudopods (no cysts)
Autopsies - brain lesions with trophozoites (no cysts) RT-PCR assay developed by CDC Immunofluorescent assay Flagellated forms can be induced by placing trophozoites into water at 37 C |
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What is the treatment for PAM?
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No known treatment
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What are the trypanosomes that are responsible for West African and East African Sleeping Sickness?
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West African: Trypanosoma brucei gambiense
East African: Trypanosoma brucei rhodesiense |
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What is the transmission of T. brucei gambiense?
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Vector: the Tsetse fly
Infection is characterized by a painful lesion/chancre at the bite site |
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How long is the incubation period of T. brucei gambiense?
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Few days - weeks
Patient is asymptomatic |
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What happens in the hemolymphatic stage of T. brucei gambiense?
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Febrile attacks followed by non-febrile periods
Headaches, malaise, weakness, night sweats, anorexia, lymphadenopathy, pruritus, joint edema Winterbottom's sign: enlargement of post-cervical lymph nodes |
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What happens in the meningoencephalitic stage of T. brucei gambiense?
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CNS invasion
Headaches, abnormal behavior, somnolence Leads to eventual loss of consciousness, coma, death |
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How is T. brucei diagnosed?
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Microscopy of chancre fluid, lymph node aspirates, blood, bone marrow, or CSF (late stages) - looking for trypomastigotes
Patients diagnosed with Trypanosomiasis must undergo LP for CSF analysis (trypanosomes) For T. brucei gambiense, conc. techniques may be required due to low # trypanosomes in peripheral blood |
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What disease does Plasmodium cause and what is its transmission?
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Malaria
Transmission: Anopheles mosquito Plasmodium is injected into blood stream Migrates to liver, initial replication Then out into blood - infects RBCs |
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What are the four species of the genus Plasmodium?
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P. ovale
P. vivax P. malariae P. falciparum - causes nearly all of the CNS complications assoc. with malaria |
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What is cerebral malaria?
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Plasmodium falciparum infects RBCs
Infected RBCs stick to sides of blood vessels Sequestration of infected RBCs in vessels and capillaries = blockages Loss of BBB integrity and inflammation are also believed to play a role |
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What are the incubation period and early symptoms of P. falciparum?
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Incubation: 8-12 days
Early symptoms: fever, severe headache, sweats, chills, nausea Tertian parasite - bouts of fever usually last 6-10 hrs and occur every other day |
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What are the symptoms of cerebral malaria?
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Disorientation, severe headaches, irritability, psychosis
Children: coma comes quickly, seizures are common Adults: coma comes gradually, seizures less common Brain swelling is commonly seen Late stages: coma and death (25-50% untreated cases) |
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How is P. falciparum diagnosed?
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Can see infected RBCs in blood smear
Peripheral blood smears: greatest # parasites found late in febrile period Ring-form trophozoites and gametocytes Gold standard |
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Why is malarial retinopathy important and what is it?
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Presence of malarial retinopathy can distinguish malaria-infected pts from those with alternate pathologies
1. Retinal whitening (macular or peripheral) 2. Vessel changes (color, tramlining) 3. Retinal hemorrhages 4. Papilledema (but not on its own) |
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What is Toxoplasma gondii?
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Causes toxoplasmosis - one of most common human infections
Obligate intracellular protozoan - forms tissue cysts containing bradyzoites Cysts in skeletal muscle, myocardium, brain Lifetime infection - chance for reactivation |
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What are the risk groups for toxoplasmosis?
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Newborns
Fetuses Immunocompromised |
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What is the mode of transmission for T. gondii?
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Undercooked meat
Congenital transmission Transfusion Cat fecal contamination - cat is the definitive host |
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What is the clinical presentation of toxoplasmosis in normal individuals?
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Most asymptomatic
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What is the clinical presentation of toxoplasmosis in immunocompromised individuals?
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Great risk for cerebral toxoplasmosis
Sub-acute onset of focal neurologic abnormalities (hemiparesis, personality changes, aphasia) Headache, seizures, ataxia, and/or facial weakness Usually a reactivation of a chronic infection AIDS pts: 1/3 with T. gondii IgG will develop encephalitis |
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How is toxoplasmosis diagnosed?
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Serology - useful in immunocompetent only
Microscopic analysis - tachyzoites in tissue samples Specimen isolation and inoculation - IP inoculation of mice with bodily fluids PCR Imaging - ring-enhancing lesions in basal ganglia |
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Describe the two stage lifecycle of Taenia solium.
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1. Adult tapeworm: humans (definitive host) ingest pork contaminated with cysts which mature into adult worms in GI and adult worms pass eggs through feces
2. Cyst stage: pigs ingest eggs from human feces, eggs hatch, larvae migrate to muscle and develop into cysts in the muscle |
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What is the difference between taeniasis and cysticercosis?
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Taeniasis: ingestion of cysticerci = adult worm grows in GI tract
Cysticercosis: ingestion of EGGS = cysticerci form throughout the body |
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What is neurocysticercosis?
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Involves CNS and is most serious form
Most common cause of late-onset seizures |
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What are the risk groups for neurocysticercosis?
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Often males of hispanic descent between 15-54 years old
Low income communities, close contact with pigs, undercooked pork |
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What are the clinical symptoms of neurocysticercosis?
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Asymptomatic phase may last for many years
Initial symptoms: non-specific neurological problems, headaches, confusion, ataxia Seizures are most common symptom Possible additional: increased ICP, nausea, focal neurologic defects Death occurs in 2-3% of cases |
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How is neurocysticercosis diagnosed?
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CT and MRI scans: cysts proceed through stages (immature, mature, inflamed, granuloma, calcification)
Cysts 0.5-2cm in diameter, often a bull's eye in middle Eggs or proglottids on microscopy not diagnostic for cysticercosis Serology: more useful in invasive stages of infection |
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How is T. solium controlled?
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Cook pork thoroughly
Hygiene - hand washing |
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What is Loa loa?
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Causative agent of Loiasis
Filarial infection: thread-like nematodes Adult, female worms give birth to microfilariae (don't develop further in human host, found in blood or lymph) Worms survive several yrs before symptoms Migrate through tissue, including conjunctiva Symptom - inflammatory swellings in extremities |
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What is the transmission and two stage life-cycle of Loiasis?
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Transmission: Mango or Deer flies
2 stage lifecycle: deer fly and human Diurnal periodicity - microfilaria are released into bloodstream between 10AM - 2PM (deer flies active at this time) |
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How is Losiasis diagnosed?
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Thick blood smears will show microfilariae (draw blood between 10AM - 2PM)
Eosinophilia will also be seen |
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What is Onchocerca volvulus?
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Causative agent of River Blindness
Filarial nematode (similar 2 stage lifecycle as Loa loa) Transmission: black flies |
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What are the signs and symptoms of O. volvulus?
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Early skin involvement due to migration: mild pruritus, papular rash, erosions, and lichenification
Classic lesion: firm, painless, non-movable nodule under the skin |
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What are the ocular symptoms of O. volvulus?
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Microfilariae within cornea migrate freely in anterior chamber, vitreous humor
Head microfilariae = massive inflammatory response = corneal opacification Bacterium Wolbachia sp. plays a role (endosymbiont) |
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How is O. volvulus diagnosed?
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Skin snips - microscopy will reveal microfilariae (found in abundance in tissues)
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What is the control and prevention of ocular parasites?
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Insect repellent (DEET)
Avoid muddy areas along rivers |
