Biology Reference
In-Depth Information
US Food and Drug Administration (FDA) approved RDT is the Binax
NOW Malaria Test, a card-based diffusion immunochromatographic assay
which detects the presence of
P. falciparum
-specific histidine-rich protein
II (HRPII) and a pan-malarial antigen common to all four human spe-
cies. When used in endemic locations where prevalence of malaria is high,
the overall sensitivities and specificities for
P. falciparum
exceeded 95%.
Performance for diagnosis of
P. vivax
is much lower, sensitivity 69% and
specificity 100%, and does not meet the WHO recommended minimum
panel detection score. Because RDT sensitivity is directly related to para-
site density, health care providers cannot rely on a negative RDT result to
rule out malaria, particularly for vivax malaria. However, a positive result
may be helpful in making management decisions before a microscopic
diagnosis can be made.
6. TREATMENT OF UNCOMPLICATED VIVAX MALARIA
The goals of antimalarial chemotherapy are to reduce the immedi-
ate risk to the host, eradicate peripheral asexual parasitaemia, prevent the
recurrent infection and interrupt the cycle of transmission. No drug on its
own has the ability to achieve all of these aims. Of particular importance
for the chemotherapy of
P. vivax
is its ability to form dormant liver stages
(hypnozoites) capable of causing relapsing infections weeks to months after
the initial blood stage infection. The chemotherapy of
P. vivax
is therefore
complex and requires a strategy targeting a variety of specific key elements
of the parasite life cycle (
Fig. 4.1
).
6.1. Treatment of
P. vivax
Erythrocytic Stages
6.1.1. Chloroquine
Chloroquine has been the treatment of choice for
P. vivax
malaria for almost
70 years. By the 1940s, clinical studies confirmed chloroquine to be an
extremely potent antimalarial agent, effective against all plasmodia species,
and its slow elimination from the blood allowing curative regimens to be
achieved with short-course treatment regimens. Clinical experience in a
huge number of patients demonstrated the drug to be safe and well tol-
erated, including its use in pregnant women and young infants. By the
1950s, its wide availability, familiarity amongst health care staff and low cost,
resulted in it becoming the first-line treatment for both
P. falciparum
and
P.
vivax
, with almost 90 metric tonnes of the drug being administered annually
during its heyday.
