Haemoparasite-Malaria A Detailed Study

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Haemoparasite-MalariaA Detailed Study

• Dr. Mohamed Iqbal Musani, MD
• Professor of Pathology
• Ibn Sina Medical College Jeddah

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Introduction 1
Malaria

• Malaria is a major public health problem in warm
  climates especially in developing countries.
• It is a leading cause of disease and death among
  children under five years, pregnant women and
  non-immune travellers/immigrants.

Children under 5 are the major at risk group in
malarious regions. Inset An Anopheles mosquito
taking a blood meal
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What is malaria ?
Malaria is a disease caused by the protozoan
parasites of the genus Plasmodium. The 4 species
that commonly infect man are
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The burden of malaria

• The direct burden of malaria
• morbidity and mortality
• Every year, there are about 500 million clinical
  attacks of malaria. Of these, 2-3 million are
  severe and about 1 million people die (about 3000
  deaths every day).
• Malaria in pregnancy accounts for about 25 of
  cases of severe maternal anaemia and 10-20 of
  low birthweight. Low birthweight due to malaria
  accounts for about 5-10 of neonatal and infants
  deaths.

• The indirect burden of malaria
• Human development Impaired intellectual
  development, developmental abnormalities
  (especially following cerebral malaria), lost
  school attendance and productivity at work
• Economics Malaria retards economic development
  in the developing world. The cost of a single
  bout of malaria is equivalent to over 10 working
  days in Africa. The cost of treatment is between
  US0.08 and US5.30, depending on the type of
  drugs prescribed as required by the local pattern
  of drug resistance.

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Geographical Distribution of Malaria
Although previously widespread, today malaria is
confined mainly to Africa, Asia and Latin
America. About 40 of the worlds population is
at risk of malaria. It is endemic in 91
countries, with small pockets of transmission
occurring in a further 8 countries.
Malaria is transmitted by the female anopheles
mosquito. Factors which affect mosquito ecology,
such as temperature and rainfall, are key
determinants of malaria transmission. Mosquitoes
breed in hot, humid areas and below altitudes of
2000 meters. Development of the malaria parasite
occurs optimally between 25-30oC and stops below
16oC. Indigenous malaria has been recorded as far
as 64oN and 32oS. Malaria has actually increased
in sub-Saharan Africa in recent years. The major
factor has been the spread of drug-resistant
parasites. Other important factors include the
persistence of poverty, HIV/AIDS, mosquito
resistance to insecticides, weak health services,
conflict and population migration.
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Endemicity

• Endemicity refers to the amount or severity of
  malaria in an area or community. Malaria is said
  to be endemic when there is a constant incidence
  of cases over a period of many successive years.
  
• Endemic malaria may be present in various
  degrees. Recognised categories of endemicity
  include
• A. Hypoendemicity - little transmission and
  the disease has little effect on the population.
• B. Mesoendemicity - varying intensity of
  transmission typically found in the small, rural
  communities of the sub-tropics.
• C. Hyperendemicity - intense but seasonal
  transmission immunity is insufficient to prevent
  the effects of malaria on all age groups.
• D. Holoendemicity - intense transmission
  occurs throughout the year. As people are
  continuously exposed to malaria parasites, they
  gradually develop immunity to the disease. In
  these areas, severe malaria is mainly a disease
  of children from the first few months of life to
  age 5 years. Pregnant women are also highly
  susceptible because the natural immune defence
  mechanisms are impaired during pregnancy.

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How is malaria transmitted?

• Malaria parasites are transmitted from one person
  to another by the bite of a female anopheles
  mosquito.
• The female mosquito bites during dusk and dawn
  and needs a blood meal to feed her eggs.
• Male mosquitoes do not transmit malaria as they
  feed on plant juices and not blood.
• There are about 380 species of anopheles mosquito
  but only about 60 are able to transmit malaria.
• Like all mosquitoes, anopheles breed in water -
  hence accumulation of water favours the spread of
  the disease.

Female Anopheles mosquito taking a blood
meal Sourcehttp//phil.cdc.gov/phil/quicksearch.
asp
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How does infection develop ?

• Plasmodium infects the human and insect host
  alternatively and several phases of the parasite
  life cycle are described.
• During feeding, saliva from the mosquito is
  injected into the human blood stream. If the
  mosquito is carrying malaria, the saliva contains
  primitive stages of malaria parasites called
  sporozoites.
• Hepatic, tissue or pre-erythrocytic phase
  Sporozoites invade and develop in liver cells.
  The infected hepatocyte ruptures to release
  merozoites.
• Erythrocytic phase Merozoites then invade red
  blood cells. The red cells lyse and this causes
  bouts of fever and the other symptoms of the
  disease. This cycle repeats as merozoites invade
  other red cells.
• Sexual phase Sexual forms of the parasites
  develop and are ingested when another female
  anopheles mosquito feeds. These develop into
  sporozoites in the gut of the insect host and
  travel to its salivary glands. Then the cycle
  starts again
• The life cycle of the malaria parasite is shown
  on the next slide

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The Malaria Parasite Life Cycle
Click on the diagram to explore different areas
of the life cycle
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The Malaria Parasite Life Cycle
1. Transmission Female anopheles mosquito bites
and releases sporozoites into the blood stream.
These circulate for about 30 mins and then invade
the liver.
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The Malaria Parasite Life Cycle
2. Pre-erythrocytic phase Also called the
tissue or hepatic phase Takes place in
hepatocytes. The sporozoites mature into
schizonts which rupture to release merozoites.
Duration of this phase depends on the species.
In P. vivax and P. ovale, the schizont may also
differentiate into hypnozoites. These are dormant
forms of the parasite which may remain in the
liver for several months or years and cause
relapse in the human host.
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The Malaria Parasite Life Cycle
3a. Asexual phase (Erythrocytic
schizogony) Merozoites invade red blood cells.
Here they grow and mature into trophozoites which
appear as ring forms. The trophozoites develop
into schizonts. The infected red blood cells then
rupture to release numerous merozoites from the
schizont to infect other red cells. Merozoite
release results in fever, chills, rigours and
other symptoms of malaria infection.
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The Malaria Parasite Life Cycle
3b. Sexual phase Some merozoites differentiate
into male and female gametocytes, the forms of
Plasmodia infective to mosquitoes. These are
taken up by a mosquito during another blood meal.
These fuse to form an ookinette in the gut lumen
of the mosquito. The ookinette invades the
stomach wall to form the oocyst. This in turn
develops and releases sporozoites which migrate
to the salivary gland of the mosquito. This
mosquito then goes on to infect another human
host.
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Severity of disease and host factors

• In addition to parasite factors, several host
  factors determine the outcome of exposure to
  malaria
• Naturally-acquired immunity. People who are
  constantly exposed to malaria gradually acquire
  immunity, firstly against clinical disease and
  later against parasite infection. Clinical
  manifestations of malaria are most severe in the
  non-immune. In holoendemic areas, these are
  children aged lt5 years and pregnant women
  (especially primagravidae). People of any age
  from areas that are free from malaria, or have
  limited malaria transmission, are at risk when
  they are exposed to malaria.
• Red cell and haemoglobin variants. Well known
  examples of inherited factors that protect
  against malaria are Haemoglobin S carrier state,
  the thalassaemias and Glucose-6-phosphate
  dehydrogenase (G6PD) deficiency. Malaria provides
  the best known example whereby an environmental
  factor (malaria) has selected human genes because
  of their survival advantage.
• Foetal haemoglobin (HbF) High levels of HbF
  occur in neonates, and in some people with
  inherited haemoglobin variants, protect against
  severe forms of P. falciparum malaria.
• Duffy blood group P. vivax requires the Duffy
  blood receptor to enter red blood cells.
  Therefore, people who do not carry the Duffy
  blood group are resistant to this malaria
  species. This explains the rarity of P. vivax in
  Africa, as most Africans are Duffy blood group
  negative.

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The clinical course of P. falciparum

• Following a bite by an infected mosquito, many
  people do not develop any signs of infection. If
  infection does progress, the outcome is one of
  three depending on the host and parasite factors
  enumerated in the previous slides
• Asymptomatic parasitaemia (clinical immunity)
  
• Acute, uncomplicated malaria
• Severe malaria

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A. Asymptomatic parasitaemia
This is usually seen in older children and
adults who have acquired natural immunity to
clinical disease as a consequence of living in
areas with high malaria endemicity. There are
malaria parasites in the peripheral blood but no
symptoms. These individuals may be important
reservoirs for disease transmission. Some
individuals may even develop anti-parasite
immunity so that they do not develop parasitaemia
following infection.
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B. Simple, uncomplicated malaria
This can occur at any age but it is more likely
to be seen in individuals with some degree of
immunity to malaria. The affected person, though
ill, does not manifest life-threatening disease.
Fever is the most constant symptom of malaria.
It may occur in paroxysms when lysis of red cells
releases merozoites resulting in fever, chills
and rigors (uncontrollable shivering).
Children with malaria waiting to be seen at a
malaria clinic in the south western part of
Nigeria. Identifying children with severe
malaria, and giving them prompt treatment, is a
major challenge when large numbers attend clinics.
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The periodicity of malaria fever

• Erythrocytic schizogony is the time taken for
  trophozoites to mature into merozoites before
  release when the cell ruptures.
• It is shortest in P. falciparum (36 hours),
  intermediate in P. vivax and P. ovale (48 hours)
  and longest in P. malariae (76 hours).
• Typical paroxysms thus occur every
• 2nd day or more frequently in P. falciparum
  (sub-tertian malaria)
• 3rd day in P. vivax and P. ovale (tertian
  malaria)
• 4th day in P. malariae infections, (quartan
  malaria)

Note how the frequency of spikes of fever differ
according to the Plasmodium species. In practice,
spikes of fever in P. falciparum, occur
irregularly - probably because of the presence of
parasites at various stages of development.
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Other features of simple, uncomplicated malaria
include

• Vomiting
• Diarrhoea more commonly seen in young children
  and, when vomiting also occurs, may be
  misdiagnosed as viral gastroenteritis
• Convulsions commonly seen in young children.
  Malaria is the leading cause of convulsions with
  fever in African children.
• Pallor resulting mainly from the lysis of red
  blood cells. Malaria also reduces the synthesis
  of red blood cells in the bone marrow.
• Jaundice mainly due to haemolysis.
• Malaria is a multisystem disease. Other common
  clinical features are
• Anorexia
• Cough
• Headache
• Malaise
• Muscle aches
• Splenomegaly
• Tender hepatomegaly
• These clinical features occur in mild malaria.
  However, the infection requires urgent diagnosis
  and management to prevent progression to severe
  disease.

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C. Severe and complicated malaria
Nearly all severe disease and the estimated gt1
million deaths from malaria are due to P.
falciparum. Although severe malaria is both
preventable and treatable, it is frequently a
fatal disease. The following are 8 important
severe manifestations of malaria Click on each
severe manifestation for details

• Acute renal failure
• Pulmonary oedema
• Circulatory collapse, shock or algid malaria
• Blackwater fever

• Cerebral malaria
• Severe malaria anaemia
• Hypoglycaemia
• Metabolic acidosis

Note It is common for an individual patient to
have more than one severe manifestation of
malaria!
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Summary of differences in the clinical features
of severe malaria in adults and children
Frequency of occurrence
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Diagnosis

• Malaria is a multisystem disease. It presents
  with a wide variety of non-specific clinical
  features there are no pathognomonic symptoms or
  signs. Many patients have fever, general aches
  and pains and malaise and are initially
  misdiagnosed as having flu.
• P. falciparum malaria can be rapidly progressive
  and fatal. Prompt diagnosis saves lives and
  relies on astute clinical assessment
• A good history
• Residence or a recent visit (in the preceding 3
  months) to a malaria endemic area
• History of fever (may be paroxysmal in nature)
• Recognise significance of non-specific clinical
  features such as vomiting, diarrhoea, headache,
  malaise
• Physical examination
• Identify signs consistent with malaria fever,
  pallor, jaundice, splenomegaly
• Exclude other possible causes of fever (e.g.
  signs of viral and bacterial infections)
• The diagnosis of malaria should be considered in
  any unwell person who has been in a malarious
  area recently

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Investigations
Blood Film Examination Thick and thin blood
films (or smears) have remained the gold
standard for the diagnosis of malaria. The films
are stained and examined by microscopy. Thick
blood film - Used for detecting malaria a
larger volume of blood is examined allowing
detection of even low levels of parasitaemia.
Also used for determining parasite density and
monitoring the response to treatment. Thin blood
film Gives more information about the parasite
morphology and, therefore, is used to identify
the particular infecting species of Plasmodium.
Show Me
Show Me
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Thick blood film

• A drop of blood is spread over a small area.
  When dry, the slide is stained with Fields or
  Giemsa stains. The red cells lyse leaving behind
  the parasites.
• Used to detect parasites, even if parasitaemia is
  low
• Less useful for speciation

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• A small drop of blood is spread across a
  microscope slide, fixed in methanol and stained
  with Giemsa stain.
• The microscopist finds the area of the film where
  red cells are lying next to each other. The fine
  details of the parasites can be examined to
  determine the species.
• Used for speciation
• Does not detect low parasitaemia

Thin blood film
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Appearance of P. falciparum in thin blood films
Ring forms or trophozoites many red cells
infected some with more than one parasite
Gametocytes (sexual stages) After a blood meal,
these forms will develop in the mosquito gut
http//phil.cdc.gov/phil/quicksearch.asp
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Other methods of diagnosis of malaria

• These are not routinely used in clinical
  practice. They include
• Antigen capture kits. Uses a dipstick and a
  finger prick blood sample. Rapid test - results
  are available in 10-15 minutes. Expensive and
  sensitivity drops with decreasing parasitaemia.
• PCR based techniques. Detects DNA or mRNA
  sequences specific to Plasmodium. Sensitivity and
  specificity high but test is expensive, takes
  several hours and requires technical expertise.
• Fluorescent techniques. Relatively low
  specificity and sensitivity. Cannot identify the
  parasite species. Expensive and requires skilled
  personnel.
• Serologic tests. Based on immunofluorescence
  detection of antibodies against Plasmodium
  species. Useful for epidemiologic and not
  diagnostic purposes.

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Malaria in pregnancy

• More than 45 million women (30 million inAfrica)
  become pregnant in malaria endemic areas each
  year.
• Common adverse effects of malaria in pregnancy
  include
• Maternal anaemia
• Stillbirths
• Premature delivery and intrauterine growth
  retardation result in the delivery of low birth
  weight infants
• The WHO now recommends intermittent preventive
  treatment (IPT) the administration of
  anti-malarial drugs (e.g. sulphadoxine-pyrimethami
  ne) during antenatal care whether or not women
  show symptoms. IPT has been shown to
  substantially reduce the risk of maternal anaemia
  in the mother and low birth weight in the
  newborn.
• Previously, chemoprophylaxis (e.g. with
  chloroquine) was recommended for all women living
  in malaria endemic areas.

Source http//phil.cdc.gov/phil/quicksearch.asp
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Sources of information

• Malaria. Greenwood BM, Bojang K, Whitty CJ,
  Targett GA. Review Lancet 2005 3651487-98.
• http//mosquito.who.int/cmc_upload/0/000/015/372/R
  BMInfosheet_1.htm
• These WHO fact sheets developed by the Roll Back
  Malaria Partnership cover many different aspects
  of malaria including prevention with
  insecticide-treated bed nets and treatment with
  atemesinin-based combination therapies
• http//www.cdc.gov/malaria/
• The US Centre for Disease Control and Prevention
  site for malaria
• http//www.malaria.org/
• Follow the Learn about malaria link on the
  Malaria Foundations website. This contains
  numerous useful and accessible resources.
• http//www.rph.wa.gov.au/labs/haem/malaria/
• An interactive resource from the Royal Perth
  Hospital, Western Australia. Contains useful
  self-assessment exercises in malaria diagnosis by
  microscopy that are set in the context of
  clinical cases.

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1. Cerebral malaria - clinical

• The most well-known severe manifestation of
  malaria
• Defined as
• unarousable coma persisting for more than one
  hour
• with asexual forms of P. falciparum in the
  peripheral blood
• other common causes of encephalopathy excluded
• Occurs most commonly in young children although
  non-immune adults are also at risk
• Cerebral malaria can rapidly progress to death,
  even with appropriate treatment. Case fatality is
  between 20-30.
• In survivors, resolution of coma usually occurs
  within 1-2 days in children and within 2-4 days
  in adults but may be complicated by neurological
  sequelae in 5 adults and gt10 of children.

A 4 year old boy who was deeply comatose and had
persistent deviation of the eyes
The illness may start with drowsiness and
confusion and then progress to coma. The loss of
consciousness is often preceded by repeated
convulsions. Retinal haemorrhages may be seen on
fundoscopy. None of the clinical features
are pathognomonic, malaria parasitaemia is common
in people living in endemic areas and coma may
complicate many illnesses. Therefore, a clinical
diagnosis of cerebral malaria is made only after
other common causes of coma (e.g. meningitis)
have been excluded.
Next
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Cerebral malaria - pathophysiology

• The exact pathogenesis of cerebral malaria is not
  well understood. It is believed to result from
  sequestration of parasitised red cells in the
  small blood vessels in the brain. The
  consequences of this include
• reduced cerebral blood flow
• cerebral hypoxia
• release of cytokines which in turn induce the
  release of nitrous oxide, a known depressor of
  consciousness

A young girl with cerebral malaria. Note the
abnormal, decerebrate posturing
Sequestration of parasitised red cells in
different tissues probably underlies most severe
manifestations of malaria
A 3 year old boy with impaired consciousness,
grimacing and marked extensor posturing of the
arms
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2. Severe malaria anaemia

• Defined as a haematocrit of lt15 or haemoglobin
  concentration lt5 g/dl.
• Occurs commonly in young children and pregnant
  women.
• Anaemia in malaria results from a combination of
  factors
• Destruction of parasitised red blood cells
• Destruction of unparasitised red cells by
  complement-mediated lysis
• Bone marrow suppression by cytokines produced by
  malaria parasites
• Haemolysis induced by medications in individuals
  with glucose-6-phosphate dehydrogenase deficiency
  
• Many patients require urgent transfusion. The
  condition may be rapidly fatal when blood
  transfusion is delayed.

Marked pallor in an African child with severe
anaemia due to P. falciparum infection
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3. Hypoglycaemia

• Blood sugar lt2.5 mmol/L
• Increases the risk of mortality and sequelae in
  children with cerebral malaria may present with
  convulsions or a deterioration in level of
  consciousness.
• Results from a combination of factors
• reduced glycogen stores because of reduced food
  intake
• increased metabolism due to fever and repeated
  convulsions
• glucose consumption by malaria parasites
• cytokine or quinine-stimulated hyperinsulinaemia

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4. Metabolic acidosis

• Lactic acidosis is a major contributor and
  probably results from tissue anoxia and anaerobic
  glycolysis
• Presents with deep, rapid respirations (as in
  diabetic ketoacidosis)

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5. Acute renal failure

• occurs almost exclusively in adults and older
  children in areas of unstable malaria
• affected patients are usually oliguric (urinary
  output lt400 ml/day) or anuric (lt50 ml/day)
• serum creatinine levels are elevated

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6. Acute pulmonary oedema
This is a grave and usually fatal manifestation
of severe falciparum malaria and occurs mainly in
adults. Hyperparasitaemia, renal failure and
pregnancy are recognised predisposing factors and
the condition is commonly associated with
hypoglycaemia and metabolic acidosis.
Acute pulmonary oedema, developing shortly after
delivery in a woman with severe P. falciparum
malaria
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7. Circulatory collapse, shock, algid malaria
Features of circulatory collapse (cold/clammy
skin, hypotension, peripheral cyanosis,
weak/thready pulses) may be seen in patients with
severe P. falciparum malaria. Algid malaria
is characterised by hypotension, vomiting,
diarrhoea, rapid respiration and oliguria. This
condition is associated with a poor prognosis.
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8. Haemoglobinuria or Blackwater Fever
Typical, dark urine of haemoglobinuria on day 0
which has cleared by day 3
This results from massive intravascular
haemolysis. The condition presents with severe
pallor, jaundice and passage of dark urine due to
haemoglobinuria. It may be associated with acute
renal failure.
A 3 year old boy with severe anaemia (Hb 3.3
g/dl) and dark urine (shown in the container)
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