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 10th 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