Lassa fever causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ammu Susheela, M.D. [2]

Synonyms and keywords: Lassa hemorrhagic fever; LHF

Overview

Lassa fever is caused by the Lassa virus, a member of the Arenaviridae family. It is an enveloped, single-stranded, bisegmented RNA virus. Mastomysrodents shed the virus in urine and droppings. The direct contact with these materials or ingestion or inhalation, can lead to infection. Lassa virus enters the cell by the receptor-mediated endocytosis and undergoes very rapid replication and manifest the disease.

Causes

Taxonomy

• Viruses; ssRNA viruses; ssRNA negative-strand viruses; Arenaviridae; Mammarenavirus

Biology

• Lassa virus belongs to Arenaviridae .
• The Arenaviridae are a family of viruses whose members are generally associated with rodent-transmitted diseases in humans. Each virus usually is associated with a particular rodent host species in which it is maintained.

Structure

• Lassa virus is an enveloped, single-stranded, bisegmented, ambisense RNA virus.

Genome

• Lassa virus genome is contained in two RNA segments, each of which encodes 2 viral proteins (total 4 viral proteins)
  • The large segment encodes RNA polymerase (L) and a small zinc-binding protein (Z) that regulates transcription and replication
  • The small segment encodes the nucleoprotein (NP) and the surface glycoprotein precursor (GP or viral spike). The GP protein is cleaved into the envelope glycoproteins, GP1 and GP2, that bind to the alpha-dystroglycan receptor and mediate host cell entry
• Nucleotide studies of the genome have shown that Lassa has four lineages: Three in Nigeria and a fourth in Guinea, Liberia, and Sierra Leone. The Nigerian strains are thought to be ancestral to the others..

Natural Reservoir

• The most common natural reservoir of Lassa virus is the rodent, Mastomys natalensis. Mastomys natalensis is commonly known as the “multimammate rat” due to the female’s multiple and prominent mammary glands.
• The mastomys rodents are abundant in the Savannas and forests of West, Central, and East Africa.

• Once infected, the rodent is able to excrete the virus in the urine for an extended time period. Mastomys rodents breed frequently, produce large numbers of offspring, and commonly inhabit human homes with food storage. All of these factors contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.

Mastomys natalensis or the natal multimammate mouse.

Mastomys natalensis is commonly known as the “multimammate rat” due to the female’s multiple and prominent mammary glands.

• Mastomysrodents shed the virus in urine and droppings and direct contact with these materials, through touching soiled objects, eating contaminated food, or exposure to open cuts or sores, can lead to infection. Because Mastomys rodents often live in and around homes and scavenge on leftover human food items or poorly stored food, direct contact transmission is common. Mastomys rodents are sometimes consumed as a food source and infection may occur when rodents are caught and prepared. Contact with the virus may also occur when a person inhales tiny particles in the air contaminated with infected rodent excretions.

Gallery

The images below display key features of the Lassa virus.

• 

  This transmission electron micrograph (TEM) demonstrates Lassa virus virions adjacent to host cell debris.Retrieved from the Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This highly magnified transmission electron micrograph (TEM) demonstrates ultrastructural details of 3 Lassa virus virions.Retrieved from the Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This transmission electron micrograph depicted eight virions (viral particles) of an Arenavirus.Retrieved from the Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

References

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