LASSA FEVER VIRUS- an insight

Lassa fever is a zoonotic, acute viral haemorrhagic fever that was named after Lassa town in Borno State, Nigeria. That was where the index case was first identified and referred to Evangel Hospital (now Bingham University Teaching Hospital) Jos in 1969 and where recent infections are still being reported as at 10^th April 2014.

The bush rat may come contaminate foodstuff and stored products with their urine and faeces that may also be aerosolized and can be inhaled. This happens more often during dry harmattan season when bush burning cause rodents to seek refuge and food in human habitats. Human to human transmission of infection is rapid such that healthcare workers are at immediate risk of infection. Community transmission through close relatives and other contacts then result in large outbreaks.

While Lassa fever has no observable symptoms in about 80% of people infected with the virus, the remaining 20% may have severe illness with case-fatality rate reaching 50%. Clinical presentation follows an incubation period of about 6-21 days. These include abrupt fever that may be mistaken for malaria, nausea, pains, diarrhea and vomiting that are usually bloody. Vascular and endothelial damage leads to overt bleeding, shock, pulmonary edema followed by liver and renal failure. Multi organ failure usually results in death.

Upon infection, Lassa fever virus can be diagnosed from whole blood or serum by virological techniques like RT-PCR, antigen detection, and virus isolation or immunological techniques to detect IgG and IgM antibodies. However, all laboratory procedures must be carried out in a biosafety level 3 and 4 facility to avoid risk of exposure to personnel.

No vaccine has been developed for the control of Lassa fever virus but antiviral like ribavirin when given intravenously can ameliorate clinical condition and convalescent phase plasma has been used in the past to treat Lassa fever. Prevention is however better than cure, therefore avoiding contact with host vectors particularly in endemic region is important. Avoid unprotected contacts with rodents and protect food from their contamination. Persons that are at great risk of exposure such as animal researchers/handlers, healthcare workers must take special precautions and always observe biosecurity measures including the use personal protective equipments (PPE), regular hand washing, strict hygiene and barrier nursing while attending to suspected cases.

In conclusion, “onehealth” approach may offer a more effective control of incessant outbreaks of Lassa and other viral haemorrhagic fever virus in West Africa.  Understanding the ecology of animal reservoir hosts, human-animal disease interface and directing counter measures against the primary cause may be less costly, more, timely and safe many lives.

This piece was contributed by Dr. Clement Meseko, a seasoned veterinary doctor and internationally trained virologist