Tropical Infections in ICU

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Case Presentation:32-year male PC: fever x 7 days, jaundice x 3 days, confusion x 1 day Exam: Temp - 105 0 F; PR 128/min; RR 24/min; BP 90/70 mm Hg; icteric; drowsy, confused & disoriented; hepatomegaly present

Acute Undifferentiated Febrile Illness:Acute -- <14 days Undifferentiated -- initial symptoms and signs non-contributory Fever -- oral temperature ≥101 0 F

Differential Diagnosis:Malaria ( P falciparum ),Scrub typhus, Leptospirosis, Dengue fever

Mechanical microcirculatory obstruction Caused by cytoadherence to the vascular endothelium of parasitized RBC  sequestration & obstruction of small vessels Intra-vascular hemolysis

Clinical Features:
Severe Malaria:
Severe Malaria Cerebral malaria (unarousable coma not attributable to any other cause in a patient with falciparum malaria) Severe normocytic anemia (< 5 gm/dl) Hypoglycemia Metabolic acidosis Acute renal failure (S. creatinine > 3 mg/dl) ARDS Shock ("algid malaria") DIC Hemoglobinuria Hyperparasitemia (>5%)

Parasitological Diagnosis:
Microscopy Rapid diagnostic tests QBC Antigen detection

Microscopy:Low cost High sensitivity & specificity Species identification Quantification
Quantitative Buffy Coat (QBC) Test:Staining of the centrifuged & compressed red cell layer with acridine orange & examining under UV light source Comparison with peripheral smear: Faster More sensitive Species identification possible Specialized equipment & consumables Expensive
Rapid Tests: Immunochromatographic tests Capture of the parasite antigens from the peripheral blood using either monoclonal or polyclonal antibodies Histidine-rich protein 2 of P. falciparum Pan-malarial Plasmodium aldolase Parasite specific LDH

Scrub Typhus:
Etiology: O tsutsugamushi Three major serotypes - Karp, Gilliam & Kato Vector: chiggers (larva of trombiculid mite) Reservoir: chiggers & rats Transovarian transmission Normal cycle: rat to mite to rat Humans are accidentally infected

Pathophysiology No known toxins Destruction of cells Endothelial injury Lympho-histiocytic vasculitis

Clinical Features:
Incubation period: 1 to 3 weeks Sudden onset of fever, headache & myalgia Delirium, nausea, vomiting, cough, jaundice Maculopapular rash Begins on trunk and spreads to extremities (centrifugal spread) Eschar

Hepatitis ,Aseptic meningitis / meningoencephalitis ,Thrombocytopenia ,ARDS / Pneumonitis ,Renal failure ,Shock ,Fetal loss

When should scrub typhus be suspected?:
Undifferentiated febrile illness with: Pathognomonic eschar Evidence of multisystem involvement, especially with: - Transaminase elevation - Thrombocytopenia - Leukocytosis

Lab Diagnosis:
Serology Weil-Felix: poor sensitivity & specificity IFA: ‘gold standard’ ELISA for Ig G & Ig M antibodies (recombinant 56 kd antigen): sensitivity & specificity >90%

Etiology: L interrogans Most widespread zoonosis in the world Peak incidence during rainy season Occupational & recreational exposures Source of infection in humans: direct or indirect contact with the urine of an infected animal Portal of entry: abrasions or cuts on skin, conjunctiva

Clinical Features:
Biphasic clinical presentation Acute or bacteremic phase lasting ~1 week Immune phase, characterized by antibody production and leptospiruria Anicteric leptospirosis Abrupt onset of fever, chills, headache, myalgia, abdominal pain, conjunctival suffusion , transient skin rash Icteric leptospirosis (Weil’s disease) Occurs in 5-15% of patients Jaundice Proteinuria, hematuria, oliguria and/or anuria Pulmonary hemorrhages, ARDS Myocarditis

CPK levels Culture (blood, CSF, urine) Positive serology Microscopic Agglutination Test (MAT) (using a range of Leptospira strains for antigens that should be representative of local strains) IgM ELISA..

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