WHAT YOU NEED TO KNOW ABOUT LASSA FEVER

Most people think that rodents such as rats are just harmless opportunistic survivors that often live with and near humans. However, it turns out that there are rat related health hazards & diseases. One common disease caused by rats is Lassa fever.

What is lassa fever?

Lassa fever is an acute viral haemorrhagic fever of 1-4 weeks duration. The illness was first discovered in 1969 in the town of Lassa, Borno state, Nigeria and was found to be caused by Lassa virus, (named after the town where the first cases originated). Lassa fever is known to be endemic (i.e, constantly present), in Guinea, Liberia, Sierra Leone and parts of Nigeria, but probably exists in other West African countries. In these areas this infection causes 300,000–500,000 cases annually, with approximately 5,000 deaths.

How is lassa virus transmitted?

Lassa virus is a single-stranded RNA virus that is zoonotic or animal-borne. This means that humans become infected from contact with infected animals. The primary animal host of the virus is the multi-mammate rat species which is the most common rodent in sub-saharan Africa. Because this rat specie often lives in human households and is eaten as a delicacy in some areas, the virus is easily transmitted to humans. The rats themselves do not show symptoms of the disease but they shed the virus freely in their excreta (urine and faeces), and secrete the virus in their saliva.

Transmission occurs via direct contact with infected excreta or saliva; or via ingestion of excretion-contaminated food or water. Victims can also become infected via skin breaks, and via mucous membranes (inhaling tiny particles of infected material). Humans can also contract the disease from other humans via aerosol transmission (coughing), or from direct contact with infected human blood, urine, or semen.

What are the risk factors of lassa fever?

Lassa fever occurs in all age groups and in both men and women. Persons at greatest risk are those living in rural areas where rats are usually found, especially in areas of poor sanitation or crowded living conditions. Health care workers are at risk if proper barrier nursing and infection control practices are not maintained. Laboratory workers can also become infected usually from contact with rodent saliva.

What are the symptoms and signs of lassa fever?

While Lassa fever is mild or has no observable symptoms in about 80% of infected individuals, the remaining 20% have a severe multisystem disease where the virus affects several organs in the body, such as the liver, spleen and kidneys. The onset of the disease is usually gradual, starting with fever and general weakness. After a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal pain may follow. Severe cases may progress to show facial swelling, fluid in the lung cavity, bleeding from mouth, nose, or gastrointestinal tract, and low blood pressure. Shock, seizures, tremor, disorientation, and coma may be seen in the late stages.

How is lassa fever diagnosed?

Lassa fever is most often diagnosed by using enzyme-linked immunosorbent serologic assays (ELISA), which detect the presence of antibodies to the Lassa virus. The virus itself may also be isolated from blood, urine, or throat washings. Other laboratory findings for Lassa fever include lymphopenia (low white blood cell count), thrombocytopenia (low platelets), and elevated aspartate aminotransferase (AST) levels in the blood.

What is the treatment for lassa fever?

Ribavirin, an antiviral drug, has been used with success for treating lassa fever patients. It has been shown to be most effective when given early in the course of the illness. Patients should also receive supportive care consisting of maintenance of appropriate fluid and electrolyte balance, oxygenation and blood pressure.

How can I prevent lassa fever?

Primary transmission can be prevented by avoiding contact with rodents, especially in the regions where outbreaks occur. Putting foodstuffs in rodent-proof containers, disposing of garbage properly and keeping the home clean can help discourage rodents from entering homes. Using these rodents as a food source is not recommended. Trapping in and around homes can help reduce rodent populations. However, the wide distribution of multi-mammate rats in Africa makes complete control of this rodent reservoir impractical.

When caring for patients with Lassa fever, further transmission of the disease through person-to-person contact or can be avoided by taking preventive precautions against contact with patient secretions. Such precautions include wearing protective clothing, such as masks, gloves, gowns, and goggles; using infection control measures, such as complete equipment sterilization; and isolating infected patients from contact with unprotected persons until the disease has run its course.