Structure & Property

Transmission

Clinical findings

Laboratory diagnosis

Treatment

Three main pathogenic groups:

- Lassa fever virus

- Tacaribe complex of viruses: Junin (Argentina), Machupo (Bolivia), Guanarito (Venezuala), Sabia (Brazil)

- Lymphocytic choriomeningitis

Genome: single strand, circular, -ve polarity RNA.

Size: 80-130nm

Helical nucleocapsid

Enveloped particles with internal granules.

Natural hosts are mice or rat.

Lassa fever virus: small rodent Mastomys, which undergoes chronic lifelong infection.

Infection is acquired by inhalation or ingestion of materials contaminated with rodent excreta, or direct contamination of cuts.

Secondary transmission among hospital personnel.

Asymptomatic infection is widespread in endemic areas.

Lassa fever:

- fever and sore throat

- vomiting, cough, weakness, malaise.

- ulcers in the mouth and pharynx and cervical lymphadenopathy.

- facial edema

- abdominal pain

- myalgia with diarrhea.

- encephalopathy with headache.

- hemorrhage and shock.

- deafness.

Tacaribe complex: severe diseases with hemorrhagic, renal, cardiovascular and neurological symptoms.

Lymphocytic chorioneningitis:

- widespread natural infection in mice.

- rare cause of aseptic meningitis, indistinguishable from the more frequent viral causes.

- fever, headache, vomiting, stiff neck, changes in mental state.

Serology:

- ELISA

- immunofluorescence

Diagnosis:

- isolate virus

- detect a rise in antibody titer.

Aseptic meningitis: spinal fluid shows an increased number of cells, mostly lymphocytes with an elevated protein level and a normal or low sugar level.

Ribavirin reduces the mortality rate if given early.

Hyperimmune serum from persons who recovered from disease is useful in some cases.

No vaccine is available.

Prevention:

- proper infection practices.

- rodent control