Lassa Fever: A Disease Spread by Multimammate Rodents

Lassa Fever: A Disease Spread by Multimammate Rodents
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Lassa virus is an animal-borne, single-strand RNA virus, named for the town of Lassa, Borno State, Nigeria. Lassa fever symptoms do not affect everyone severely, so overall, approximately 5,000 individuals (1-in-60 persons, or less than 2 percent) die from this disease each year.

The Lassa virus can spread to almost all body tissues. It initially infects the mucous membranes, then moves to the intestines, the respiratory system and the urinary tract. Finally, the virus attacks the body’s vascular system.

Infection by Animals

The Lassa virus can be contracted from animals—specifically Mastomys or so-called multimammate rodents. Multimammate rodents are quite common in Africa. They are often in and about households. The virus spreads through the animal’s urine and feces, whether by touch, such as by an open sore, through food contamination, or even directly by ingestion, as some eat Mastomys. If the environment is dry, viral exposure can result from airborne particles of bodily waste.

Transmission by Humans

Although statistically, only one percent or so of hospitalized victims die of Lassa fever, the numbers are not evenly distributed across all sectors of society. Pregnant women during their third trimester die much more frequently than others. Tragically, only about five percent of fetuses survive infection. Nursing infants can be infected by their mother’s breast milk.

Healthcare workers are frequent victims, through exposure to contaminated body fluids.

Fever Symptoms

The incubation period for this disease is between six and twenty-one days. The sufferer will complain of fever and facial swelling. He may experience conjunctivitis. Other symptoms include:

  • Chest Pain
  • Cough
  • Diarrhea
  • Difficulty Swallowing
  • Elevated Heart Rate
  • High Blood Pressure
  • Low Blood Pressure
  • Nausea
  • Seizures
  • Vomiting

Lassa fever may be difficult to diagnose, since symptoms are similar to those of Ebola and malaria. An infected person excretes the virus for between three and nine weeks. An infected man will carry the virus in his semen for three months.

Lassa Virus

Image Credit: CDC

Prevention and Treatment

Avoid Mastomys! Store food in rodent-proof containers. Do not consume multimammate rodents as food. Trap them, when possible. Infected individuals should be attended in an isolation ward. Careful disposal of bodily fluids and excrement is essential. Administering the anti-viral Ribavirin may be indicated. If so, it should be given as soon as possible—preferably intravenously. The Centers for Disease Control also advises close attention be given to fluid and electrolyte balance, as well as oxygenation and blood pressure.

References and Resources

Centers for Disease Control, Special Pathogens Branch: Lassa fever

Stanford University: Arenaviridae - Lassa fever virus

Health Protection Agency (UK): Lassa fever - fact sheet for health professionals

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