Infectious Diseases and Parasitology: Key Pathogens, Transmission, and Treatments

Roundworms (e.g., Ascaris)

Spread: fecal-oral. Presentation: mild GI symptoms to obstruction. Diagnosis: stool O&P, ELISA, PCR. Treatment: Albendazole, Mebendazole, Ivermectin; surgery for obstruction.

Hookworm (nematode)

Spread: skin penetration; blood > lungs > cough up and swallow. Presentation: iron-loss GI disease. Diagnosis: stool O&P. Treatment: Albendazole, Mebendazole, Ivermectin.

Schistosomiasis (fluke) (flat)

Spread: freshwater snails, skin penetration. 2nd only to malaria. Contaminated water with urine/feces. Presentation: intestinal or urogenital symptoms, hematuria, anemia. IMMUNE RXN IS TO THE EGGS. Presentation: ascites, HSM, general GI. Diagnosis: urine/stool ova, serology. Treatment: Praziquantel TID for 1 day.

Tapeworms (Taenia spp.) (flat)

Spread: undercooked beef/pork. Presentation: abdominal pain, proglottids in stool. Can migrate elsewhere in body when larva, otherwise intestines. Diagnosis: stool O&P. Treatment: Praziquantel PO once; recheck stool at 1 and 3 months.

Malaria

Spread: Anopheles mosquito. infected blood, not contagious. Can be dormant in liver before blood. Presentation: fever, chills, cerebral malaria. Diagnosis: thick/thin smears x3, PCR. Treatment: IMMEDIATE Chloroquine/hydroxychloroquine if sensitive; artemether-lumefantrine or atovaquone-proguanil if resistant.

Toxoplasmosis

Cat lady disease. Spread: undercooked meat, cat feces, vertical, transfusion. Leading cause of food related death. Presentation: cervical LAD w/out pain, CNS disease if immunocompromised. Diagnosis: serology, PCR, CT/MRI WITH RING LESIONS. Treatment: EMPIRICAL Pyrimethamine + Sulfadiazine + Leucovorin for 6 weeks, then maintenance.

Blastomycosis

Spread: inhalation from soil. Present in Ohio/Mississippi RV

Presentation: pulmonary disease, crusted plaques, lytic bone lesions. (blasted face and bones) Diagnosis: KOH sputum, biopsy, culture (slow but specific). CXR/CSF to see involvement

Treatment: Itraconazole; Amphotericin B for severe/CNS.

Coccidioidomycosis (Valley Fever)

Spread: inhalation of soil spores. California/Arizona disease! Presentation: often asymptomatic, mimics community acquired pneumonia 30% in endemic areas. Diagnosis: EIA, PCR if immunocompromised, Biopsy if disseminated. Treatment: Fluconazole or Itraconazole. relapse possible.

Cryptococcosis

Spread: inhalation from environment, bird feces. Crypto likes to fly! Can become latent/disseminate to CNS

Presentation: pneumonia, CNS meningoencephalitis. Diagnosis: fungal culture!!!, India ink, antigen detection. Treatment: Fluconazole for mild pulmonary disease.

Histoplasmosis

Spread: inhalation from bird/bat droppings. Present in Ohio/Mississippi RV. Histo for historically gross (birds/bats/ohio), get that antigen first.

Presentation: 1 % symptomatic: mild to disseminated disease, meinigitis and lung infection. AIDS DEFINING. Delayed onset.

Diagnosis: antigen EIA (gold standard), culture (use when severe), microscopy. Treatment: Itraconazole for mild/moderate; Amphotericin B for severe/disseminated/CNS.

Pneumocystis jirovecii pneumonia

Spread: person-to-person respiratory (unique). Presentation: Flu-like, exertional dyspnea, dry cough. Think AIDS

Diagnosis: CXR, CT (with ground glass), sputum, bronchoscopy. Treatment: IV TMP-SMX (Bactrim) for severe disease.

Prion diseases (e.g., CJD)

Spread: misfolded protein, infected meat, inherited. Presentation: rapidly progressive dementia. Diagnosis: MRI, LP, EEG, biopsy. Treatment: supportive only.

Pinworms

nematodes (round); fecal oral route; females lay eggs at night in perianal area > itchy > ingest eggs. 1/3 asymptomatic; tape test for 5 days. Treat with Albendazole, Mebendazole, Pyrantel Pamoate; 1 big dose, then a f/u dose later

Rx for flatworms?

praziquantel (different dose for kids/adults based for tapeworms, same dose for schistosomiasis)