Multimammate rats responsible for Lassa fever outbreak in Nigeria, West Africa nations.
If you are already used to rats living in or around your house like room mates, neighbors or co-tenants, you may want to have a rethink and get hostile, because these rodents may be as dangerous as the dreaded Ebola virus itself.
In 1969, two missionary nurses died in Nigeria, it was found out that they died as a result of Lassa fever caused by rats. Its origin is traceable to Borno state where it was named after the town where it first occurred. Also, in Nov 2014 in Benin, lassa fever was diagnosed.
What is Lassa fever?
Lassa fever is an acute viral illness that has been recorded in several West African nations such as Sierra Leone, Liberia, Guinea and Nigeria. It is likened to the infamous ebola virus . The virus is animal-borne and it is a single-stranded RNA virus that belong to the virus family Arenaviridae.
Quick tips on lassa fever
According to WHO, about 80% of persons infected with Lassa virus show no symptoms. It is an acute viral illness that can be transmitted by rodents such as rats.
The hosts of the Lassa virus are rodents commonly referred to as the “multimammate rat” and though infected with the Lassa virus, they do not become ill, yet they can shed the virus in their urine and faeces.
- The incubation period of Lassa fever ranges from 6-21 days.
- It can last between 1-4 weeks.
- Once food or other house hold items are contaminated by urine or feces from rats, the virus can be transmitted to humans.
- it can be transmitted from Person-to-person
- It can also be transmitted via laboratory transmissions, especially in hospitals with poor or inadequate infection prevention and control measures.
- The Lassa virus cannot be transmitted via skin-to-skin or other bodily contact that does not involve exchange of body fluids.
- In severe cases, the virus affects several organs such as the liver, spleen and kidneys
- Deafness occurs in 25% of patients who survive the disease
- There is currently no vaccine that protects against Lassa fever.
- According to the WHO, “early supportive care with re-hydration and symptomatic treatment improves survival”.
Prevention of outbreaks
Detection of the disease in affected persons may be difficult because the clinical course of the disease is so variable, however, the following measures will be key to prevent outbreaks.
- Timely isolation of affected patients
- Infection protection and quality control measures
- Effective trail of persons who may have contacted the disease is essential to prevent outbreaks.
Signs of Lassa fever: It may start with fever, general weakness, and malaise.
Headache, sore throat, nausea, vomiting, muscle pain, diarrhoea, chest pain, cough, and abdominal pain may follow after a few days.
When Lassa fever is severe, it can lead to any of the following conditions;
Low blood pressure, swelling in the face, nose, vagina or gastrointestinal tract fluid in the lung cavity, bleeding from the mouth, protein in the urine, shock, seizures, disorientation, tremor or even coma.
In addition, it can lead to deafness, as seen in 25% of patients who survive the disease. After 1-3 months, patient may gradually regain hearing, but this is obtainable in half of the cases.
- During recovery, transient hair loss and gait disturbance may occur
- If fatal, it can lead to death within 14 days of onset and may be severe late in pregnancy.
What you should know about the host
The “multimammate rat” or Mastomys natalensis which is the host or reservoir of the Lassa virus, is commonly found in homes and areas where food is stored. This makes the spread of the virus effective between humans and the rodent. The rodent may carry the virus for as long as its life time and excrete the virus in urine and droppings or even direct contact with house hold materials.
The rodent produces numerous off springs frequently and is commonly found in west and east Africa, especially in the savannas and forests of west, east and central Africa.
Because Mastomys rodents often live in and around homes and feed on leftover human food items or poorly stored food, direct contact transmission is common.
- The Lassa virus is commonly transmitted to humans via ingestion or inhalation.
- Direct contact with already infected objects or surfaces
- Exposure to open cuts or sores, can lead to infection.
- Some persons eat these rodents hence infection may occur when they are been caught and prepared.
- Sweeping or other cleaning activities may lead to aerosol or airborne transmission; this may occur when a person inhales contaminated air. The air may be infected with rodent excretions.
- Contact with urine or faeces of infected astomys rats.
- There are reported cases of sexual transmission of Lassa virus
- Direct contact with the blood, urine, faeces, or other bodily secretions of a person infected with Lassa fever.
- Infected medical equipment like reused needles in care facilities may spread the virus.
- Person-to-person transmission may occur after exposure to virus in the blood, tissue, secretions, or excretions of a Lassa virus-infected individual.
Nosocomial transmission is more common to health care settings. The Lassa virus may be spread from person-to-person, especially in the absence or use of proper personal protective equipment (PPE).
Who is at risk of Lassa fever?
- It can affect all age groups or gender.
- If you live in areas with so much rats
- Health care providers caring for patients without adequate prevention and control practices
In May 25th, CDC and New Jersey department of health confirmed a death from Lassa fever in a traveler returning to the United States.
Because the symptoms of Lassa fever are so varied and non-specific, clinical diagnosis is often difficult, especially in the early course of the disease. Lassa fever is difficult to distinguish from other viral haemorrhagic fevers such as Ebola virus disease; as well as other diseases that cause fever, including malaria, shigellosis, typhoid fever and yellow fever.
Testing may be required for definitive diagnosis. This should be done only in specialized laboratories considering that laboratory specimens may be hazardous, hence should be handled cautiously.
The following test may be used for definitive diagnosis of lassa virus infections in the laboratory;
· antibody enzyme-linked immunosorbent assay (ELISA)
· antigen detection tests
· reverse transcriptase polymerase chain reaction (RT-PCR) assay
· Virus isolation by cell culture.
Treatment and vaccines
If given early on in the course of clinical illness, the antiviral drug ribavirin may be effective for treatment of Lassa fever, however, according to the WHO, there is currently no evidence to support the role of ribavirin as post-exposure prophylactic treatment for Lassa fever.
At the moment, there is no known vaccine for protection against Lassa fever.
Prevention and control
- Ensure good personal, environmental and communal hygiene to prevent rodents from invading your homes.
- Avoid storing waste from food or other consumables inside your house.
- Do not keep waste in the open for rodents to prey on.
- Dispose waste far away from your home
- Store waste and food items in closed containers where they cannot eat through
- You may consider keeping cats.
- Avoid contact with blood or body fluids or sick persons especially while caring for sick persons.
Prevention in Health care facilities
Health care facility workers should use personal protective equipment and ensure compliance with standard infection prevention and control precaution.
According to recommendation by the WHO, health-care workers caring for patients suspected to have Lassa fever should immediately contact local and national experts for advice and to arrange for laboratory testing.