Treatment and Prevention of Lassa Fever-
Dr. Faozat Aragbaiye
Lassa fever is a zoonotic disease, meaning that humans become infected from contact with infected animals. The animal reservoir or host, of Lassa virus is a rodent of the genus Mastomys, commonly known as the multimamate rat. Mastomys rats infected with Lassa virus do not become ill, but they can shed the virus in their urine and faeces.
Lassa fever is known to be endemic in Benin (where it was diagnosed for the first time in November 2014), Ghana diagnosed for the first time in October 2011), Guinea, Liberia (diagnosed for the first time in February 2009), Sierra Leone and Nigeria but probably exists in other West African countries as well.
Humans usually infected with Lassa virus from exposure to urine or faeces of infected Mastomys rats. Lassa virus may also be spread between human through direct contact with blood, urine, faeces or other bodily secretions of a person infected. Person-to-person transmission occurs in both community and healthcare setting, where the Virus may be spread by contaminated medical equipment such as reused needles, sexual transmission of Lassa fever has be reported. There is no epidemiological evidence supporting air-borne spread between humans.
Lassa fever occurs in all ages and both sexes. People at greatest risk are those living in rural areas where Mastomys rats are usually found, especially in community with overcrowding and poor sanitation.
Health workers caring for Lassa fever patients without adequate protection are also at risk.
Symptoms of Lassa Fever
The incubation period of Lassa fever rages from 6 – 21 days. The Onset of the disease when it is symptomatic is usually gradual, starting with fever, general weakness and malaise. After a few days, headache, sore throat, muscle pain, chest pain, nausea vomiting, diarrhea, cough and abdominal pain may follow. In severe cases, facial swelling, pleural effusion, and bleeding from all orifices, shock, seizures, tremor, disorientation and coma may set in at the later stages.
Death usually occurs within 14 days of onset in fatal cases. The disease is especially severe in pregnancy, with maternal death of and or fetal death occurring in more that 80% of cases Deafness occurs in 25% of patients who survive the disease. In half of these cases, hearing returns partially after 1- 3 months. Transient loss and loss of gait may occur during recovery.
Because of the symptoms of Lassa Fever are so varied and non-specific, clinical diagnosis is often difficult especially early in the course of the disease Lassa Fever is difficult to distinguish from other viral diseases as well as other diseases that cause fever, including malaria, typhoid fever, yellow fever and shigellosis
Lassa virus infection can only be diagnosed definitely in the laboratory using the following tests.
RTPCR, ELISA, antigen detection tests and virus isolation by self culture.
Intravenous Ribavirin injection given at the early stage of the illness, is effective. Intravenous fluids, electrolytes and oxygenation. This treatment reduced mortality from 50% to 5% if given early in serious Illness
Other than acute illness, the most common implication or after effect of Lassa fever is hearing loss, which has been observed during recovery in 20 – 30% of cases of Lassa virus is believed to be a common cause of sudden deafness in affected patient. Pregnant women, especially in the 3rd trimester are at risk for serious disease. Spontaneous abortion occurs in 95% of infection with Lassa fever.
Prognosis of Lassa fever is generally good considering that many individuals in affected areas are having antibodies to Lassa fever and do not recall illness. Most illness is mild and does not require hospitalization. Of those hospitalized from the community with Lassa fever up to 15% die. Mortality may be up to 65% in cases of hospital associated transmission, perhaps because patients do not seek or receive correct treatment until late into illness
There is no vaccine available as yet against Lassa Fever, but research is ongoing.
Oral riboflavin given as prophylaxis or preventive treatment has been studied in a limited fraction during an outbreak with no evidence of transmission.
The most important preventive methods against Lassa fever outbreaks is to eliminate rodent habitats by improving sanitation, safe food storage and preparation and clean water access. The public must be taught about limiting consumption or safety preparing bush meat by careful use of gloves and thorough cooking. This measure also helps to prevent other hemorrhagic fever outbreaks such as Ebola virus.
In healthcare facilities suspected cases require strict infection control precautions to prevent contact with blood, body fluids and contaminated surfaces around infected patients.
Hand hygiene requires washing with soap and water and / or using alcohol based sanitizer between patients. Medical personnel managing Lassa fever patient, should wear protective garment with gloves and face mask.
Safe injection practices require use of disposable needles. Similar personal protective measures are needed for safe laboratory handling and safe mortuary services.