Epidemiology & control of
tropical disease
Dr. Nadia Aziz
C.A.B.C.M.
Department of community medicine
Baghdad medical college
MALARIA ICD-10 B50-B54
Objectives
1- Identify Malaria & its different types
2- Describe its occurrence
3- Identify signs & symptoms of the clinical disease
4- Identify the diagnostic methods
5- Describe the methods of control
MALARIA
A
parasitic
disease infections with the 4 human
types of malaria.
The fever pattern of the first few days of
infection resembles early stages of many other
illnesses.
MALARIA
The
most serious
malarial infection,
falciparum
malaria presents a clinical picture including
fever, chills, sweats, anorexia, nausea,
lassitude, headache, muscle and joint pain,
cough and diarrhea.
Anaemia and/or splenomegaly.
Complications
Acute
encephalopathy
(cerebral malaria),
severe
anemia
,
icterus
,
renal failure
(black-water
fever),
hypoglycaemia
,
respiratory distress
,
lactic
acidosis
and more rarely
coagulation defects
and
shock. Severe malaria is a possible cause of coma
and other CNS symptoms.
Blackwater fever
Also called malarial
hemoglobinuria
, one of the
less common yet most dangerous complications
. It occurs almost exclusively with
infection from the
falciparum
.
has a high
The passage of urine that is black or dark red in
colour
The distinctive colour of the urine is due to the
presence of large amounts of
released during the extensive destruction of the
patient’s red blood cells by malarial parasites.
High Risk population
Pregnant
women and
young children
when
infected are highly susceptible to development
of severe and complicated malaria.
Malaria in a pregnant woman increases the risk
of
maternal death
,
miscarriage
,
stillbirth
and
neonatal death
.
Case-fatality
Among untreated children and adults can reach
10%–40%
or higher.
Types of Malaria
The other human malarias:
Vivax
malariae
and
ovale
Are
not usually life-threatening
.
MALARIA
After a fever-free interval, the cycle of
chills
,
fever
and
sweating
recurs daily, every other day
or every third day.
MALARIA
True relapses with no parasitaemia (in
vivax
and
ovale
infections) may occur at irregular
intervals for up to
5 years
.
Infections with P.
malariae
may
persist for life
with or without recurrent febrile episodes.
Diagnosis
1- Demonstration of malaria
parasites in
blood films
. Repeated microscopic
examinations
every 12–24
hours may
be necessary because the blood density of
parasites varies.
Diagnosis
Both
thick
&
thin blood films
should be done.
Thick
film
find parasites
that may be present in
small numbers.
Thin
film for
species identification
and
determination of
degree of parasitemia
( the
percentage of erythrocytes harboring parasites)
Diagnosis
2-
Rapid diagnostic
tests that detect plasmodial
antigens in the blood.
3-
PCR
is the most sensitive method.
4-
Antibodies
, demonstrable by
IFA
(not helpful
for diagnosis of current illness)
Infectious agents
Plasmodium
falciparum
, P.
vivax
, P.
ovale
and P.
malariae
,
protozoan parasites with asexual and sexual
phases.
Occurrence
The disease causes over 1 million deaths per
year in the world, most of these in
young
children
in Africa.
Reservoir
Humans
are the only important reservoir of
human malaria.
For
P. malariae
, which is common to man, the
African
apes
and probably some South
American
monkeys
.
Mode of transmission
1- Bite of an infective
female Anopheles
mosquito
.
Most species feed at night,
some important vectors
also bite at
dusk
or in the
early
morning
.
Mode of transmission
2- Injection or
transfusion of infected blood
3- Use of
contaminated needles
and syringes
(e.g. injecting drug users).
4-
Congenital
transmission occurs rarely.
Incubation period
The period between an infective bite and
detection of the parasite in a thick blood smear
is the “
prepatent period
,” which is typically 6–
12 days for P. falciparum, 8–12 days for P. vivax
and P. ovale and 12–16 days for P. malariae,
But may range up to about 2 months
pregnant women are more
vulnerable
to
falciparum malaria (and possibly other
Plasmodium species) that
infect the placenta
and cause
low birth-weight
,
anemia
,
abortion
and
premature delivery.
Period of communicability
Humans may infect mosquitoes as long as
infective gametocytes are present in the blood
;
this varies with parasite species and with
response to therapy.
The
mosquito remains infective for life.
Methods of control
A. Preventive measures
:
I. Local community measures
1)
Insecticide-treated mosquito nets
(ITNs) are
the most universally useful measure for the
prevention of malaria. (pyrethrinoids should be
repeated once or twice a year)
Preventive measures
2)
Indoor residual spraying with insecticides
(IRS) targeting adult mosquitoes, where they
rest indoors on sprayable
surfaces.
Preventive measures
3) In epidemic-prone areas, malaria
surveillance
should be based on weekly
reporting and
monitoring
important factors
environmental conditions
and human
population movements
.
Preventive measures
4)
protection from biting
mosquitoes is of
paramount importance.
5)
prophylaxis with antimalarial drugs
for
travellers to malarious areas, and “
standby
” or
emergency self-treatment is recommended
when a febrile illness occurs in a falciparum
malaria area.
Malaria prophylaxis
Chloroquine
(5 mg base/kg/week) plus
Proguanil
(3 mg/kg/day) may be safely given to
infants.
Standby treatment
The most important factors that determine the
survival
of patients with falciparum malaria are
early diagnosis
and
immediate treatment
.
Prophylaxis
1-
Chloroquine
Minor side-effects
2-
Hydroxychloroquine
less side – effects
3-
Mefloquine
It is
not
recommended
for
women
in first trimester
of pregnancy(serious
side-effects with long-term use)
4-
Doxycycline
alone (100 mg once daily)
Prophylaxis
5-
Primaquine
0.5 mg base/kg/day for adults
(do not have G6PD deficiency).
With the exception of primaquine,
chemosuppressive
drugs
do not eliminate
intrahepatic parasites
, so clinical relapses of vivax
or ovale malaria may occur after the drug is
discontinued.
B. Control of patient, contacts and the
immediate environment
1)
Isolation
: For hospitalized patients,
blood
precautions
. patients should be in
mosquito-
proof areas
from dusk to dawn.
B. Control of patient, contacts and the
immediate environment
2)
Investigation of contacts and source of
infection
:
Determine
history
of previous infection or of
possible exposure e.g. sharing needles or
transfusion-induced malaria.
Treatment
3) Specific treatment for all forms of malaria:
1-
Chloroquine
- sensitive P. falciparum, P. vivax, P.
Malariae and P. ovale is the oral administration of
a total of 25 mg of chloroquine base/kg
administered
Plasmodium
falciparum
is nowadays
resistant
to
chloroquine and to sulfadoxine-pyrimethamine
Treatment
2)
Quinine dihydrochloride
, for emergency
treatment of adults with severe or complicated
infections or unable to retain orally medication,
20 mg salt/kg ,diluted in 10 ml/kg of isotonic
fluid, by slow IV
Treatment
3)
Primaquine
, is the drug of choice for
prevention of relapses of P. vivax and P. ovale
infections.
Thank you