Browse categories and answer follow-up questions to refine your symptom profile.
Approach to the Critical Patient
Immediate stabilization
High risk parasitic syndrome stabilization
Airway risk
If GCS < 13, airway preparation and critical care activation
If ongoing seizure, benzodiazepine protocol and antiseizure loading
Breathing risk
If hypoxemia, oxygen escalation with continuous SpO2 monitoring
If ARDS pattern, lung protective ventilation strategy
Circulation risk
If shock, sepsis pathway with early vasopressor if fluid nonresponsive
If severe anemia with hemodynamic compromise, transfusion protocol
Rapid severity screen
Travel or residence in malaria endemic area with fever, presume malaria until excluded
Immunosuppression with eosinophilia concern, presume Strongyloides risk before steroids
Time-critical diagnostics and consultation triggers
Time-critical parasitic threats
Malaria suspicion
STAT thick and thin smear within 24 hours of presentation
If initial smear negative with high suspicion, repeat every 12 to 24 hours for 3 sets
CNS parasite concern
New seizure, focal deficit, altered mental status, urgent neuroimaging pathway
If raised ICP concern, avoid lumbar puncture until imaging
Hydatid disease concern
Large liver or lung cyst symptoms, avoid cyst aspiration without specialist plan
Severe diarrhea with dehydration
Rapid volume and electrolyte correction with stool pathogen testing plan
Consult triggers
If suspected malaria, infectious diseases and critical care early
If suspected neurocysticercosis, neurology and infectious diseases early
If suspected helminth hyperinfection, infectious diseases early
Key concepts
Key parasitic infection concepts
Protozoa
Malaria with hemolysis, microvascular sequestration, multiorgan dysfunction risk
Amoebiasis with colitis and liver abscess risk
Giardia with malabsorption and prolonged watery diarrhea
Helminths
Strongyloides autoinfection with hyperinfection risk in immunosuppression
Schistosomiasis with freshwater exposure risk and chronic organ fibrosis
Taenia solium with neurocysticercosis seizure risk
Eosinophilia pattern
Helminth infections common cause
Acute malaria typically without eosinophilia
History
Exposure and risk profile
Exposure and risk profile
Travel itinerary and dates
Countries and regions
Departure and return dates
Vector exposure
Mosquito bites and nighttime exposure
Tick exposure
Water exposure
Freshwater swimming or rafting
Untreated drinking water
Food exposure
Undercooked pork, beef, fish, crab, crayfish
Unwashed produce
Animal exposure
Dogs or livestock
Cat feces exposure
Sexual exposure
Oral anal contact
New partners with diarrheal illness
Household and institutional exposure
Daycare outbreaks
Shelter or crowding exposure
Host risk
Pregnancy
HIV or other immunosuppression
Steroid use or planned steroid therapy
Asplenia
Symptom pattern and timelines
Symptom pattern and timelines
Fever pattern
Onset relative to travel
Rigors and sweats
GI pattern
Watery diarrhea
Bloody diarrhea
Abdominal pain localization
Respiratory pattern
Cough and wheeze
Hemoptysis
Neurologic pattern
Seizure
Headache
Confusion
Focal neurologic deficit
Dermatologic pattern
Pruritic rash
Migratory serpiginous rash
GU pattern
Hematuria with freshwater exposure
Systemic red flags
Syncope
Oliguria
Jaundice
Bleeding
Physical Exam
General and vitals
General and vitals
Vitals trend
Fever
Hypotension
Tachycardia
Tachypnea
Perfusion
Capillary refill
Mottling
Mental status
Agitation or somnolence
Delirium features
Hydration
Mucous membranes
Orthostasis
Bleeding signs
Petechiae
Oozing at venipuncture sites
Focused systems
Focused systems
HEENT
Scleral icterus
Conjunctival pallor
Cardiopulmonary
Crackles
Wheeze
Signs of heart failure
Abdomen
Hepatomegaly
Splenomegaly
RUQ tenderness
Peritoneal signs
Neuro
Meningismus
Focal deficits
Papilledema
Skin
Urticarial rash
Larva currens pattern concern
Cutaneous larva migrans pattern concern
GU
Suprapubic tenderness
External genital lesions
Differential Diagnosis
Life-threatening and must not miss
Life-threatening differential
Severe malaria, Plasmodium falciparum, ICD-10 B50.9
Altered mental status
Acidosis
Severe anemia
Cerebral malaria, ICD-10 B50.0
Coma
Seizure
Fulminant amoebic colitis, ICD-10 A06.0
Toxic megacolon pattern
Perforation risk
Amoebic liver abscess, ICD-10 A06.4
Fever with RUQ pain
Pleuropulmonary extension risk
Strongyloides hyperinfection, ICD-10 B78.7
Immunosuppression
Sepsis with Gram negative bacteremia pattern
Neurocysticercosis, ICD-10 B69.0
New onset seizure
Hydrocephalus risk
Echinococcosis with cyst rupture risk, ICD-10 B67.9
Anaphylaxis risk
Secondary seeding risk
Common syndrome-based alternatives
Syndrome-based differential
Febrile traveler
Malaria
Dengue, ICD-10 A90
Typhoid fever, ICD-10 A01.0
Rickettsial disease, ICD-10 A79.9
Persistent watery diarrhea
Giardiasis, ICD-10 A07.1
Cryptosporidiosis, ICD-10 A07.2
Cyclospora, ICD-10 A07.4
Bloody diarrhea
Entamoeba histolytica colitis, ICD-10 A06.0
Shigellosis, ICD-10 A03.9
Campylobacter enteritis, ICD-10 A04.5
Eosinophilia with pulmonary symptoms
Helminth larval migration syndromes
Drug reaction
Allergic disease
Seizure with ring enhancing lesions
Neurocysticercosis
Toxoplasmosis, ICD-10 B58.2
Tuberculoma
Laboratory Tests
Core ED labs
Core ED labs
CBC with differential
Anemia pattern
Thrombocytopenia pattern
Eosinophilia pattern
Electrolytes and renal function
Hypokalemia from diarrhea
AKI from dehydration or severe malaria
Liver panel
Hemolysis pattern jaundice
Transaminitis pattern for hepatitis differential
Glucose
Hypoglycemia concern in severe malaria
Hyperglycemia stress pattern
Venous blood gas with lactate
Metabolic acidosis concern
Lactate elevation for shock severity
Coagulation studies
DIC concern in severe systemic illness
Blood cultures
Sepsis pattern with possible Strongyloides hyperinfection translocation
Parasitology and targeted infectious testing
Parasitology and targeted testing
Malaria smear microscopy
Thick smear for detection
Thin smear for speciation and percent parasitemia
If initial smear negative with high suspicion, repeat every 12 to 24 hours for 3 sets
Rapid diagnostic test for malaria
Adjunct when microscopy delayed
Negative test does not exclude low parasitemia early infection
Stool ova and parasite
Multiple specimens on separate days for intermittent shedding
Lower yield for some protozoa without specific antigen or PCR
Stool antigen or PCR panels
Giardia
Cryptosporidium
Entamoeba histolytica
Serology when tissue invasive concern
Strongyloides serology in eosinophilia and exposure
Schistosoma serology in traveler with freshwater exposure and delayed symptoms
Urinalysis
Hematuria pattern for urogenital schistosomiasis concern
Severe disease adjuncts
Severe disease adjuncts
Hemolysis assessment
LDH
Haptoglobin
Bilirubin fractionation
Pregnancy testing when relevant
Medication selection impact
Imaging selection impact
HIV testing when appropriate
Opportunistic parasite risk modification
Toxoplasmosis risk modification
Diagnostic Tests
Scoring Systems
Scoring systems
Sepsis severity tools
qSOFA for rapid bedside risk stratification
NEWS2 for deterioration risk stratification
Severe malaria criteria framework
Any impaired consciousness or coma
Multiple seizures
Respiratory distress or ARDS
Shock
Acidosis with elevated lactate
Hypoglycemia
Severe anemia
Hyperparasitemia percent parasitemia reporting on thin smear
MRI
MRI indications and protocols
Neurocysticercosis evaluation
Parenchymal cysts and edema characterization
Ventricular or subarachnoid disease assessment
Spinal or cerebral parasite complications
Myelitis concern
Vasculitis concern
Limitations
Unstable patient transport risk
Time to imaging delay risk
CT
CT indications and protocols
Head CT with contrast when safe
New seizure with concern for neurocysticercosis
Ring enhancing lesions pattern
CT abdomen and pelvis
Liver abscess localization
Complication evaluation for fulminant colitis
CT chest
Hydatid cyst pulmonary concern
Parasitic pulmonary hemorrhage concern
Ultrasound
Ultrasound applications
RUQ ultrasound
Liver abscess characterization
Hydatid cyst pattern recognition
POCUS shock evaluation
Volume status estimation
Cardiac function screening
Soft tissue ultrasound
Subcutaneous cyst or abscess differentiation
Disposition
Admission and higher level care
Admission and higher level care criteria
Suspected or confirmed malaria with severity features
Altered mental status
Acidosis or elevated lactate
AKI
Hypoglycemia
Severe anemia
Respiratory distress
CNS parasitic infection concern
New seizure
Focal deficits
Hydrocephalus concern
Inability to tolerate oral therapy
Persistent vomiting
Severe dehydration
Immunocompromised host
Steroid therapy need with Strongyloides risk
Advanced HIV with toxoplasmosis concern
Social barriers
Unreliable follow up
Unsafe home environment
Discharge criteria and follow up
Discharge criteria and follow up
Nonsevere illness with stable vitals
No altered mental status
No significant dehydration
Confirmed diagnosis with oral regimen and tolerance
First dose observed when feasible
Clear return precautions provided
Follow up plan
Infectious diseases or travel medicine
Repeat testing plan when initial tests pending or early negative
Treatment
Immediate therapy for unstable presentations
Immediate therapy for unstable presentations
Sepsis bundle alignment
If shock, vasopressor titration to perfusion targets
If severe metabolic derangement, targeted correction with close monitoring
Hypoglycemia management
IV dextrose bolus for symptomatic hypoglycemia
Dextrose infusion if recurrent hypoglycemia
Seizure management
Benzodiazepine first line
Levetiracetam or phenytoin loading per institutional protocol
Anaphylaxis management
If suspected hydatid cyst rupture with anaphylaxis, epinephrine protocol and airway readiness
Antiparasitic regimens
Antiparasitic regimens selection
Severe malaria, initial parenteral therapy
Artesunate IV 2.4 mg/kg at 0 hours
Artesunate IV 2.4 mg/kg at 12 hours
Artesunate IV 2.4 mg/kg at 24 hours
Transition to complete oral antimalarial course after clinical improvement and parasite density decline
Choice guided by species, resistance region, and local guidance
Uncomplicated malaria, oral options
Artemisinin-based combination therapy per local protocol
Directly observed first dose when feasible
Repeat smear plan to document clearance when indicated
Strongyloidiasis, uncomplicated
Ivermectin 200 microg/kg PO daily for 1 to 2 days
Relative contraindication, suspected Loa loa coinfection
Alternative, albendazole 400 mg PO twice daily for 7 days
Schistosomiasis
Praziquantel therapy
Timing, at least 6 to 8 weeks after last freshwater exposure for travelers
Specialist dosing protocol selection based on species and setting
Neurocysticercosis, viable parenchymal disease
Albendazole 15 mg/kg/day in 2 divided doses, typical 10 to 14 days, max 1200 mg/day
Anti-inflammatory co-therapy planning to reduce treatment related edema
Antiseizure therapy for seizure control and prevention
Toxoplasmosis, severe or CNS disease concern
Pyrimethamine based regimen with leucovorin to reduce marrow toxicity
Sulfadiazine co-therapy when tolerated
Infectious diseases consultation for regimen tailoring and duration
Supportive care and complications
Supportive care and complications
Fluids and electrolytes
Oral rehydration for mild to moderate dehydration
IV crystalloid for severe dehydration with frequent reassessment
Electrolyte correction with repeat labs
Anemia management
Transfusion threshold individualized to symptoms and comorbidity
Consider exchange transfusion discussion for extreme hyperparasitemia per specialist guidance
Frequent hemoglobin monitoring in hemolysis pattern
Medication safety checks
QT prolongation risk review with antimalarials and co-medications
G6PD status consideration for specific antimalarials where relevant
Pregnancy compatible regimen selection
Steroid caution in exposure risk
If planned high dose steroids with Strongyloides risk, infectious diseases consultation and empiric ivermectin consideration
Special Populations
Pregnancy
Pregnancy considerations
Maternal fetal risk stratification
Malaria in pregnancy with higher severe disease risk
Lower threshold for admission and parenteral therapy if malaria suspected
Obstetrics consultation for fetal monitoring plan
Medication safety
Avoid teratogenic antiparasitics when alternatives exist
Shared decision making with obstetrics and infectious diseases
Breastfeeding compatibility check for selected agents
Diagnostic modifications
Radiation sparing imaging when feasible
Ultrasound first strategy for hepatobiliary concerns
MRI preferred over CT when clinically equivalent and stable
Geriatric
Geriatric considerations
Atypical presentation risk
Blunted fever response
Delirium as primary sign of severe infection
Lower threshold for admission
Medication risk
QT prolongation and polypharmacy interaction review
Renal dosing adjustments with AKI risk
Falls risk with dehydration and orthostasis
Complication risk
Higher risk from severe anemia and hypoxemia
Lower physiologic reserve in sepsis physiology
Early escalation planning
Pediatrics
Pediatric considerations
Weight based dosing
Artesunate dosing weight based for children and adults
Ivermectin relative contraindication in weight < 15 kg
Pharmacy verification for all antiparasitics
Dehydration risk
Rapid progression in diarrheal illness
Oral rehydration therapy prioritization
IV therapy threshold lower with poor intake
Neuro presentations
Seizure threshold considerations
Neuroimaging pathway when red flags present
Close observation needs for postictal or persistent symptoms
Background
Epidemiology
Epidemiology
Malaria importation relevance
Returning traveler fever with malaria risk until excluded
Many labs have limited smear experience in low incidence settings
Repeat smears needed in nonimmune low parasitemia early disease
Helminth exposure patterns
Strongyloides endemic in tropical and subtropical regions
Chronic infection possible for decades
Hyperinfection triggered by immunosuppression
Freshwater exposure patterns
Schistosomiasis linked to contaminated freshwater exposure
Symptom onset may be delayed after exposure
Treatment timing after exposure affects efficacy
Pathophysiology
Pathophysiology
Malaria
RBC infection with hemolysis
Microvascular obstruction and tissue hypoxia in falciparum
Multiorgan dysfunction pathways
Protozoal diarrhea
Enterocyte disruption and malabsorption
Secretory diarrhea and dehydration
Prolonged shedding and reinfection risk
Helminth infections
Tissue migration and eosinophilic inflammation
Chronic granulomatous response in schistosomiasis
Autoinfection in Strongyloides
Neurocysticercosis
Cyst degeneration with inflammatory edema
Seizure generation via cortical irritation
Hydrocephalus risk in ventricular disease
Therapeutic Considerations
Therapeutic considerations
Malaria management principles
Immediate parenteral therapy for severe malaria
Artesunate dosing at 0, 12, 24 hours
Transition to oral regimen after improvement
Strongyloides management principles
Ivermectin first line 200 microg/kg for 1 to 2 days
Avoid ivermectin in suspected Loa loa coinfection
Steroid exposure risk amplification for hyperinfection
Schistosomiasis management principles
Praziquantel most effective against adult worms
Traveler timing at least 6 to 8 weeks after exposure
Repeat treatment sometimes needed based on response and species
Neurocysticercosis management principles
Albendazole typical dosage 15 mg/kg/day divided, max 1200 mg/day
Antiparasitic therapy can worsen edema temporarily
Anti-inflammatory and seizure control co-management essential
Patient Discharge Instructions
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Diagnosis and expectations
Parasitic infection suspected or confirmed based on testing and clinical features
Symptoms may improve over days after starting therapy
Some tests may still be pending
Medications
Take antiparasitic exactly as prescribed
Avoid alcohol with nitroimidazoles if prescribed
Call if rash, severe nausea, jaundice, or new confusion
Hydration and diet
Oral rehydration solution for diarrhea
Small frequent fluids
Resume normal diet as tolerated
Return to ED now
Trouble breathing
Fainting or severe weakness
Confusion, severe headache, seizure
Persistent vomiting with inability to keep fluids down
Bloody stool or black stool
Decreased urination or severe dehydration signs
Fever with recent travel to malaria region, especially within months of return
Worsening jaundice or dark urine
New chest pain or severe abdominal pain
Follow up
Follow up with infectious diseases or travel clinic within recommended timeframe
Repeat labs or stool testing if directed
If malaria suspected, return for repeat smears if symptoms persist despite initial negative testing
References
Clinical guidelines and key sources
Clinical guidelines and key sources
CDC, Treatment of Severe Malaria, artesunate dosing 2.4 mg/kg at 0, 12, 24 hours
CDC, Evaluation and Diagnosis of Malaria, repeat smears every 12 to 24 hours for 3 sets if high suspicion
Canada, CATMAT, repeat smears at 12 and 24 hours if symptoms persist
CDC, Clinical Care of Strongyloides, ivermectin 200 microg/kg PO for 1 to 2 days and contraindication considerations
CDC, Clinical Care of Schistosomiasis, traveler treatment timing 6 to 8 weeks after freshwater exposure
IDSA, Neurocysticercosis guideline, albendazole 15 mg/kg/day divided with max 1200 mg/day
CDC, Clinical Care of Toxoplasmosis, pyrimethamine based regimen with leucovorin
HIV clinical guidelines, toxoplasmosis dosing framework for adults
Source specification and formatting requirements
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.