MAIN CLINICAL FEATURES OF SYMPTOMATIC ARBOVIRAL INFECTIONS

1. Infections presented by fever, myalgia, arthralia & skin rash (Febrile systemic disease)

   • Incubation period: 3-7 dys

   • Clinical manifestations: Suddenly rised fever with chills, severe headache, anorexia, lymphadenopathy, ocular pain, conjunctivitis, nausea-vomiting, myalgia-arthralgia (muscle, bone, joint pains), maculopapular skin rash, leucopenia

   • Prognosis: Mortality is very low

   • Examples: Dengue virus types 1,3,4 (breakborne fever), West Nile, O’nyong nyong, Chikungunya, Ross River, Sandfly fever

   • Treatment: Symptomatic, no specific therapy

2. Infections presented by aseptic meningitis & encephalitis

   • Incubation period: 3-15 dys

   • Clinical manifestations: High fever, severe headache, malaise, nausea-vomiting, diffuse myalgia, photophobia, maculopapular skin rash, neurological findings (neck stiffness, paralysis, decreased consciousness, convulsions), peripheral leucocytosis and neutrophilia

   • Prognosis: Mortality differs from 2%-80%, and approximately in 5-20% of patients irreversible neurologic sequelae occur

   • Examples: EEE, WEE, VEE, TBE, SLE, CE, JE, LCM

   • Treatment: Supportive, no specific therapy. Hyperimmune serum may be used in severe infections.

   • Prevention: Inactivated and/or live-attenuated equine encephalitis vaccines are developed but in trial yet

3. Infections presented by hemorrhagic fever with multi-organ involvement

   • Incubation period: 3-8 dys

   • Clinical manifestations: Sudden onset, high fever, headache, generalized myalgia, conjuntivitis, followed by hypotension and hemorrhagic manifestations (organ bleedings: hemoptysis, hemathemesis-black vomit-, melena, petechiae-echymoses), severe liver (hepatitis) and kidney damage, Disseminated Intravascular Coagulation (DIC), shock, coma, death. Progressive leukopenia, proteinuria, hemaglobin values decrease when bleeding occurs, bilirubin and hepatic enzymes increase in ichteric cases.

   • Prognosis: Mortality differs from 1%-50%.No sequelae, the patient either die or recover completely.

   • Examples: Y.fever (black vomit disease, severe jaundice), Dengue Hem.Fever (Dengue virus type 2), CCHF, Hantaviruses, Marburg, Ebola, Arenaviral infections.

   • Treatment: Supportive and symptomatic. Ribavirin has in-vitro activity against Yellow fever virus but in-vivo trials show no effective therapeutic effects. Alpha interferon therapy supposed to be useful. Hyperimmune serum may be used in severe infections.

   • Prevention: Live-attenuated vaccine for Y.fever prepared from 17D strain of the virus in embryonated egg. Vaccination is required for travel to endemic zones.

LABORATORY DIAGNOSIS

• Virus isolation : Difficult & not practical, hazardous for lab. staff, should performed only in reference lab. with biosafety level 4.

  • Specimens: Blood, CSF, organ biopsy material

  • Inoculation to: Cell lines, yolk sac of chick embryo or suckling mice

  • Viral replication can be confirmed by hemagglutination test. Arboviruses agglutinates chick, goat or pig erythrocytes.

• Serology: Antibodies against a specific virus can be determined by Complement Fixation, Hemagglutination Inhibiton, Neutralization, ELISA and immunofloresce antibody methods

• Direct antigen detection by immunofloresce method

• Nucleic acid detection by molecular methods

Category: Microbiology Notes