LASSA FEVER

This is also known as Lassa Haemorrhagic Fever. It is an acute viral haemorrhagic illness caused by Lassa Virus, a member of the ARENAVIRUS family of viruses. Lassa fever frequently infects people in West Africa.

 

CAUSE

Lassa virus is ZOONOTIC. It spreads to humans from rodents, specifically multimammate mice (probably the most common mice in equatorial Africa) ubiquitous in human households and eaten as a delicacy in some areas.

In these mice, infection is in a persistent asymptomatic state.

The virus is shed in their excreta (urine and faeces), which can be aerosolized. Infection in human typically occurs by exposure to animal excrement through the respiratory or gastrointestinal tract.

Inhalation of tiny particles of infectious materials (aerosols) is believed to be the most significant means of exposure or through broken skin or mucus membrane directly exposed to infectious material.

 

TRANSMISSION

The virus is transmitted to humans from contact with food or household items contaminated with rodent excreta.

Person-to-person infections and lab transmissions can also occur, particularly in the hospital environment in the absence of adequate infection control measures, presenting a disease risk for healthcare workers.

 

SIGNS AND SYMPTOMS

In 80% of cases, its sasymptomatic. In the remaining 20%, the infection takes a complicated course.

After an incubation period of 6 to 21 days, acute illness with multiorgan involvement develops. General symptoms are fever, facial swelling, mucosal bleeding, muscule fatigue, conjunctivitis, etc. Others include nausea, bloody vomit, bloody diarrhea, dysphagia (for the gastrointestinal tract), cough, chest pain, pharyngitis (respiratory tract), hypertension, hypotension, tachycardia (cardiovascular system), encephalitis, meningitis, seizures (nervous system), etc.

This infection is difficult to distinguish from other viral haemorrhagic fevers such as Ebola, Maburg and Malaria.

The virus is excreted in urine for 3-9 months and in semen for 3 months.

 

PREVENTION

The control of rodent population is impractical, measures to prevent the infection can be achieved by keeping rodent out of homes and food supplies as well as maintaining effective personal hygiene. Goggles, masks, lab coats and gloves are advised while in contact with an infectious person.

 

DIAGNOSIS

This can be made using ELISA test for antigen and IgM antibodies. This gives 88% sensitivity and 90% specificity for the presence of the infection.

Other lab findings for lassa include Lymphopenia (low white blood cell count), Thrombocytopenia (low platelet count), Cerebro Spinal Fluid assessment and increased aspartate aminotransferase.

 

TREATMENT

Persons suspected of lassa fever infection should be admitted to isolation facilities and their body fluids and excreta, properly disposed of.

Early and aggressive treatment is achieved using RIBAVIRIN ( a prodrug which acts by interfering with viral replication by inhibiting RNA-dependent nucleic acid synthesis)  especially when given intravenously.

Patients can also receive supportive care consisting of maintenance of appropriate fluid and electrolyte balance,oxygenation and blood pressure.

 

Compiled by Pharm Feyisayo Odebunmi

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