UNIT 7.1 APICOMPLEXA: MALARIAL PARASITES

Ague

Paludism

Tropical Fever

Malaria is also known as

MALARIA

• It is actually a vector-borne disease of the blood

• It commonly occurs in developing countries located in the tropics, where the tropical climate favors transmission.

Plasmodium spp. (of the class Sporozoa)

• P. falciparum

• P. vivax

• P. malariae

• P. ovale

• P. knowlesi

Malaria etiology

P. falciparum

• 70%

• cerebral malaria

Malarial Parasites

• causes aestivo-autumnal malaria, blackwater fever, or malignant tertian malaria

• Most common in the Philippines, around ____ of cases

• This species is the most common etiologic agent in the Philippines

• Causes severe or complicated malaria and death if not treated promptly and appropriately, particularly ______________

Cerebral malaria

______________ occurs when infected red blood cells travel through the small blood vessels of the brain and block these vessels, interfering with normal brain function. This can lead to coma and eventually death if not managed properly.

William Welch; 1897

P. falciparum was first Described by __________ in _____

P. vivax

• 30%

• Relapse

Malarial Parasites

• causes benign tertian malaria

• Around ____ of cases in the country

• Very rarely causes severe disease

• ________ is common if not treated adequately

Giovanni Battista Grassi & Raimondo Feletti; 1890

P. vivax was Described by _________________ and __________________ in _______;

P. vivax (and P. ovale);

hypnozoite

Among the Plasmodium species, relapse is most commonly associated with ________________ This is because these parasites have a __________ stage.

hypnozoite;

liver

The _________ stage is a dormant stage in the ______, where the parasite remains inactive for a period of time. When it becomes active again, it can cause a recurrence of infection even after the initial illness has resolved.

Malarial Parasites

P. malariae;

• 1%

• 50 years

Malarial Parasites

• causes quartan malaria

• Less than ____ of cases in the country

• Infection is usually not severe but may last up to _________ if not treated

• Although infections are generally milder, they may persist for decades if untreated.

Charles Louise Alphonse Laveran; 1880

P. malariae was Described by ________________ in _____

P. ovale

• 2 cases

• 1950s

Malarial Parasites

• causes benign tertian ovale malaria

• Very rare, last documented ______ in the Philippines in the ______

• Relapse may occur if not treated adequately due to the presence of the hypnozoite (dormant) stage in the liver.

John William Watson Stephens; 1922

P. ovale was Described by ________________ in _____;

P. knowlesi

• macaque monkeys (Macaca mulatta)

Malarial Parasites

• causes primate malaria

• This parasite is primarily associated with malaria in monkeys, particularly ___________________

• Very similar with P. malariae

• Because of this similarity, laboratory technologists performing malaria microscopy previously reported infections as P. malariae when P. knowlesi was actually present.

Female anopheles mosquito

Malarial parasites vector

male Anopheles

The __________ feeds exclusively on nectar and fruit juices; do not bite humans.

female Anopheles

The _________ feeds primarily upon blood.

Need blood for egg development

livestock;

zooprophylaxis.

Because mosquitoes may feed on animals, in some communities people place _______ (e.g., carabao or cows) near houses so mosquitoes will bite the animals instead of humans. This practice is called _____________

~30 days

Average life span of an Anopheles mosquito:

Anopheles flavirostris

PRIMARY VECTOR

• Breeds in slow-flowing, partly shaded clear streams

• Indoor and outdoor biter

• Bites both man and animals

Aedes aegypti

Unlike ___________ (vector of dengue and chikungunya) which breeds in clean stagnant water.

Flight range of 1.5 to 2.0 kilometers

Peak biting time of 9:00PM to 2:00AM

Anopheles flavirostris Flight range & Peak biting time

Anopheles litoralis

Anopheles maculatus

Anopheles mangyanus

Anopheles balabacensis

SECONDARY VECTORS

A. litoralis

SECONDARY VECTORS

• Coastal areas

A. maculatus

SECONDARY VECTORS

• Semi-stagnant streams along sides of shallow rivers with mat of algae

A. magyanus

SECONDARY VECTORS

• Slow-flowing streams in wooded areas

A. balabacensis

SECONDARY VECTORS

• Stagnant water in forested areas, hoofprints, animal wallow

Race

• Black Americans

• Duffy antigen

BASIC FACTORS IN MALARIA TRANSMISSION

• Some populations are naturally resistant to certain malaria species.

• For example, many _____________ lack the ______________ on their red blood cells (RBCs). The Duffy antigen acts as a binding site for Plasmodium vivax. Without this receptor, the parasite cannot attach to and penetrate the RBCs, making these individuals resistant to infection by P. vivax

Sex

• males

BASIC FACTORS IN MALARIA TRANSMISSION

• Studies suggest that ______ may have a slightly higher probability of acquiring malaria, possibly due to occupational exposure or lifestyle habits that involve outdoor activities

partial

Immunity in malaria is only ________

This means that previous exposure does not give complete protection against the disease.

• Young children

• Pregnant women

• Non-immunes: Their immune defenses are weaker or less developed

More susceptible population to malaria

1. Temperature

2. Rainfall

3. Relative Humidity

Environmental Factors Affecting Transmission

Temperature;

• +20°C to +30°C

Environmental Factors Affecting Transmission

• The best conditions for the development of malaria parasites in the mosquito and the transmission of infection are when the mean temperature range is ______________

Rainfall

Environmental Factors Affecting Transmission

• umerous breeding places are created; Increase density of mosquitoes; Rise in relative humidity; Higher probability of survival of mosquitoes

Relative humidity;

• 60%

Environmental Factors Affecting Transmission

• lengthens the life of the mosquito and enables it to live long enough to transmit the infection to several persons

• should at least be ____ to favor malarial growth

Asexual cycle (Schizogony)

GENERAL LIFE CYCLE OF THE MALARIA PARASITES

• occurs in humans

• Humans are the intermediate host.

Sexual cycle (Sporogony)

GENERAL LIFE CYCLE OF THE MALARIA PARASITES

• occurs in mosquito

• The mosquito is the definitive host because sexual reproduction occurs here.

anticoagulant

The mosquito saliva also acts as an ____________, allowing the mosquito to feed on blood easily.

• Infective stage to humans: Sporozoite

• Infective stage to mosquito: Gametocyte

Malarial parasite infective stage

• Intermediate host: Human

• Definitive host: Anopheles mosquito

Malarial parasite IH and DH

1. Liver Stage: Pre-erythrocytic/Hepatic Cycle)

2. Blood Stage: Erythrocytic Cycle

3. Sexual Cyle in MOsquito (Sporogony)

3 STAGES OF MALARIA PARASITES

1. Chills

2. Fever

3. Sweating

CLINICAL SIGNS AND SYMPTOMS

Acute;

• cerebral malaria

PATHOLOGY

• May present as non-severe acute febrile illness

• If not treated promptly and adequately, it may progress to __________ and death

Chronic

• Anemia

• placental malaria

PATHOLOGY

• May be asymptomatic

• _______

  • Need for multiple blood transfusions

  • Developmental disorders

  • Death

• May occur during pregnancy

  • May cause ____________ to low birth weight, then increased infant mortality rate.

Examination of Thick and Thin Blood Smear

Using a microscope with an oil immersion objective and immersion oil.

The gold standard for laboratory diagnosis of malaria infection.

1. Trophozoite

2. Schizont

3. Gametocyte

When examining the blood smear (blood film), we can observe three developmental stages seen in blood films:

Trophozoite and gametocyte

_____________________ are used for identifying the species of Plasmodium.

1. Nucleus/Chromatin dot

2. Vacuole

3. Cytoplasm

4. Stippling

Structure of Plasmodium spp.

stippling

Refers to granules that appear in the infected red blood cell (RBC).

stippling name for each plasmodium spp.

P. vivax

P. ovale

Size of infected RBCs enlarged?

thin smear

To determine enlargement, compare the infected RBC with surrounding RBCs in the _________

P. falciparum

P. malariae (occasionally smaller than normal)

Not enlarged RBC?

P. vivax

Single infection (1 parasite per RBC)

P. falciparum

Multiple infection (several parasites in one RBC)

Multiple ring forms within a single RBC. Up to five parasites may infect one RBC.

P. vivax

P. ovale

Presence of stippling (dots in RBC)

P. falciparum

P. malariae

Stipplings not clearly visible:

P. vivax (Schuffner’s dots)

When stippling appears coarse and granular, it usually suggests _______

P. falciparum trophozoite

TROPHOZOITE (DIAGNOSTIC POINTS OF EACH)

➔ Small, regular, fine to fleshy cytoplasm

➔ Infected RBCs not enlarged

➔ Numerous, multiple infection is common

➔ Ring, comma (incomplete), marginal, or accole forms are seen; often have double chromatin dots

➔ Maurer's dots not clearly visible

Maurer’s dot

P. falciparum

• It is also called the ring form because of its ring-like appearance. It may appear half-moon shaped.

• thin smear = intact and round RBC

• thick smear = RBCs rupture during hemoflobinization; parasite stages

P. falciparum

• In thin smear, RBCs remain ___________

• In thick smear, RBCs are ruptured during _______________, so only ______________ remain visible.

P. vivax

TROPHOZOITE (DIAGNOSTIC POINTS OF EACH)

➔ Infected RBCs usually enlarged

➔ Irregular or fragmented cytoplasm (amoeboid)

➔ Mature ring forms tend to be large and coarse

➔ Schuffner's dots are frequently visible, but cannot be seen as well in some cases.

P. malariae

TROPHOZOITE (DIAGNOSTIC POINTS OF EACH)

➔ small, few

➔ Ring to rounded, compact, vacuolated or non-vacuolated

➔ Band forms seen

➔ Dark, scattered pigment

➔ Ziemann's dots not clearly visible

➔ Infected RBCs not enlarged, or smaller

Bands

This is the key identifying feature of P. malariae trophozoites

TROPHOZOITE (DIAGNOSTIC POINTS OF EACH)

P. ovale trophozoite

TROPHOZOITE (DIAGNOSTIC POINTS OF EACH)

➔ James’ dots present at early ring forms; dots may be larger and darker than P. vivax

➔ Ring larger than P. vivax

• Few

➔ Ring to rounded, compact

• Ring shape maintained until late in development

➔ Single, prominent chromatin

➔ Reported in the Philippines

P. falciparum schizont

SCHIZONT (DIAGNOSTIC POINTS OF EACH)

P. vivax schizont

SCHIZONT (DIAGNOSTIC POINTS OF EACH)

P. malariae schizont

SCHIZONT (DIAGNOSTIC POINTS OF EACH)

➔ Small, compact, dark ➔ Usually few

➔ 6 – 12 merozoites in ‘rosette’ formation, but more often in irregular cluster

• The rosette formation resembles a flower or star pattern, making the schizont easier to identify.

➔ Concentrated pigments

P. ovale

SCHIZONT (DIAGNOSTIC POINTS OF EACH)

P. falciparum

GAMETOCYTE (DIAGNOSTIC POINTS OF EACH)

Plasmodium falciparum gametocyte (FG).

P. falciparum

• In reporting results, it is not necessary to specify macro- or microgametocyte. The report simply indicates ____________________________

Microgametocyte

P. falciparum Gametocyte

• Broader, shorter, and more sausage-shaped

• Loosely scattered chromatin

• Golden brown pigments scattered at the central half

Macrogametocyte

P. falciparum Gametocyte

• Small, compact, central chromatin dot

• Pigments closely adhere to the chromatin

P. vivax gametocyte

GAMETOCYTE (DIAGNOSTIC POINTS OF EACH)

P. malariae gametocyte

GAMETOCYTE (DIAGNOSTIC POINTS OF EACH)

P. vivax

GAMETOCYTE (DIAGNOSTIC POINTS OF EACH)

P. malariae

GAMETOCYTE (DIAGNOSTIC POINTS OF EACH)

P. ovale

GAMETOCYTE (DIAGNOSTIC POINTS OF EACH)

MIXED INFECTIONS

Infection of an individual by more than one species of Plasmodium

MULTIPLE INFECTION

when more than one parasite infects a single red blood cell, which is commonly seen in Plasmodium falciparum.

P. vivax and P. falciparum

Possible mixed infection with ____________________