Lábrea fever
Lábrea fever, also known as
Lábrea's black fever and
Lábrea hepatitis, is a lethal
tropical viral infection discovered in the
1950s in the city of
Lábrea, in the
Brazilian Amazon basin, where it occurs mostly in the area south of the
Amazon River, in the states of
Acre,
Amazonas and
Rondônia . The disease has also been diagnosed in
Colombia and
Peru. The similar form in Colombia has been named
Santa Marta fever.
Its main manifestation is a
fulminant hepatitis which may kill in less than a week, and which characteristically affects children and young adults, and more males than females. It is accompanied also by an
encephalitis in many cases. The disease is highly lethal: in a study carried out in 1986 at
Boca do Acre, also in the Amazon, 39 patients out of 44 died in the
acute phase of the disease.
Survivors may develop
chronic disease.
Lábrea fever has a sudden onset, with
jaundice (bilious color of the skin),
anorexia (lack of appetite),
hematemesis (blood
vomits),
headache,
fever and severe
prostration. Death occurs by
acute liver failure (ALF). In the last phase,
neurological symptoms such as agitation,
delirium,
convulsions and hemorrhagic
coma commonly appear.
Lábrea fever is a
coinfection or
superinfection of
hepatitis D (HDV) and
hepatitis B (HVB).
The infection by HDV may occur in a patient who already has the HVB, or both viruses may infect at the same time a previously uninfected patient. VHD can only multiply in the presence of VHB, therefore
vaccination against VHB prevents infection. Thus, American and Brazilian scientists have determined that the HVD, or delta, virus, which is a small circular
RNA virus, is normally unable to cause illness by itself, due to a defect. When it is combined with the
hepatitis B virus, Lábrea hepatitis may ensue. The main discovery of HVD and HVB association was done by Dr.
Gilberta Bensabath, a leading tropical virologist of the
Instituto Evandro Chagas, of
Belém, state of
Pará, and her collaborators.
Infected patients show extensive destruction of
liver tissue, with
steatosis of a particular type (microsteatosis, characterized by small fat droplets inside the cells), and infiltration of large numbers of inflammatory cells called
morula cells, comprised mainly by
macrophages containing HDV
antigens.
In the 1987 Boca do Acre study, scientists did an epidemiological survey and reported delta virus infection in 24% of asymptomatic hepatitis B virus carriers, 29% of acute nonfulminant hepatitis B cases, 74% of fulminant hepatitis B cases, and 100% of chronic hepatitis B cases. The delta virus seems to be
endemic in the Amazon region.
Treatment is similar to hepatitis B, but due to its high letality, more aggressive therapeutic approaches are recommended in the acute phase. In absence of a specific
vaccine against HDV, the vaccine against hepatitis B (HBV) must be given soon after birth in
risk groups.
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