4. Plasmodium species: Objectives
• List the human malarial parasites indicating the
species found in Sri Lanka
• Describe the life cycle (LC)
• Identify stages that are useful in diagnosis
• Evaluate methods of laboratory diagnosis
• Identify points in the LC where preventive
measures are applicable
4
5. 5
MALARIA
Mal-aria (bad air)
Very important
tropical disease
200 million
infected
1 million
deaths/year –
African children
Not only in Man.
Mammals, reptiles, birds have their own malarial
parasites
6. 6
5 Plasmodium spp. causing HUMAN MALARIA
3.P.malariae
band form
1. P.falciparum
small rings
2. P.vivax
large rings & schizonts
4.P.ovale
red cell has oval shape
Found in SL Not in SL
Common
Species
worldwide
5. P.knowlesi
Monkey parasite.
Human disease
South-East Asia
11. 11
Plasmodium vivax- Vivax Malaria
Earlier called ‘benign tertian malaria’
World wide highest in Asia.
Africa: Pf higher
West Africa – no Pv
because NO Duffy Blood Group Antigen)
Liver cycle- av. 8 days; hypnozoites ++
Erythrocytic cycle: reticulocytes preferred
Parasitaemia less than 2%
12. 12
ERYTHOCYTIC CYCLE - P vivax
Trophozoites
rings-
amoeboid-
compact-
Schizonts-early/late - 24-48h
Gametocytes
female & male
Rbc: enlarged
Schuffner’s stippling
(fine, numerous, pink-red)
12-24 merozoites
6 h
16 h
24 h
&
16. 16
late trophozoite 24h -
compact, pigment black
Schizogony in capillaries of internal
organs - SEQUESTRATION
Schizonts 24-48h
Merozoites 8-24
Gametocytes- late (10 days)
persists- 4 months
Crescent shape
Female & Male
P falciparum- No amoeboid
or schizonts
in peripheral
blood
18. 18
Plasmadium malariae - quartern malaria
Mature rbc preferred.
Trophozoites: rings
band-form
pigment dark brown
Rbc: not enlarged; Zeimann’s stippling (v fine)
SCHIZOGONY- 72 h
Schizont: 6-12 merozoites
(daisy head)
Gametocytes: Similar to vivax but rbc not enlarged
19. 19
Plasmodium ovale- ovale malaria
Confined to Africa. Common in West Africa
(P.vivax absent – Duffy blood gp Ag absent)
Parasitized red cells appear oval
parasite ‘vivax -like’
20. 20
5th
Human Malaria Parasite
Plasmodium knowlesi
Rapidly multiply –
Quotidian 24h
Erythrocytic cycle
Early Trophozoites:
small rings similar to
P.falciparum
Late Trophozoites :
band-forms like
P.malariae
26. 26
Formation of oocyst & sporozoites
Sporozoites- 14 µ m
Duration of sporogony in mosquito
•Temperature
•Humidity
•Mosquito species
•Parasite species
Pv,Pf
10-12 d
Pm
15-20 d
oocyst
27. 27
FEVER with chills & rigors
Palpable
SPLEEN
ANAEMIA – Falciparum malaria
Severe anaemia = leading cause
of death in children
28. 28
Severe falciparum
malaria
3yr old cerebral malaria
& opisthotonos
Dysconjugate (asymmetric)
gaze in comatose Gambian
child with cerebral malaria.
29. 29
Malaria - Laboratory diagnosis
2 Main Methods :
(1) Microscopy – thin & thick blood film x 3
(2) Antigen detection
= detection of parasite derived products
proteins or enzymes
(3) PCR – only for research
(4) Antibody detection – screen blood donors
in non-endemic countries
30. 30
Microscopy – identify parasite
Thin & Thick film x3 Consecutive days
GOLD STANDARD
THICK FILM
(3-5 µl)
Very Sensitive
Limit of detection 10-20 p/µl
Can quantify against WBCs
THIN FILM
(1µl)
Accurate species
identification
31. 31
Falciparum malaria - peripheral parasitaemia
could underestimate the total parasite burden
The parasites causing the clinical symptoms are
SEQUESTERED in the capillaries of deep organs
- In microvascular circulation
In synchronous cycles:
peripheral parasitaemia could be (-)ve
Repeat blood films daily – 3 consecutive days
37. 37
(2). ANTIGEN DETECTION
RAPID DIAGNOSTIC TESTS [RDTs]
Dipstick/card methods
2. Pf only Detects
Histidine Rich Protein = pf HRP2
in plasma, urine
+ve for 3 weeks after parasites killed.
Not suitable to assess drug resistance
1. Most useful commercial tests detecting
Pf + Pv
Detects
parasite Lactate dehydrogenase ( pLDH)
depends on LIVE parasites
CAN USE TO TEST DRUG RESISTANCE
38. 2. RDTs – sensitivity is low
(won’t detect below 100 – 200 parasites/μl)
38
ANTIGEN DETECTION
RAPID DIAGNOSTIC TESTS [RDTs]
WHO malaria RDT performance evaluation - Round 2
1. High cost
Disadvantages
Advantages
1.Easy to do in field
2.Don’t need trained persons
39.
40. Prevention & Control of Malaria
40
Interrupt transmission @ different stages
1. MAN
3. PARASITE
2. VECTOR
A
C
B
A
A
41. 41
A.Prevent Man-Vector Contact &
B.Reduce Vector Density
most useful strategies
Insecticide Treated Nets [ITN]
Insecticide Residual Spraying [IRS]
Prevention & Control of Malaria
C. Reduce Parasite Population
Early detection & treatment of patients
42. Prevention & Control of Malaria in SL
Ministry of Health – Anti Malaria Campaign
ELIMINATION of Malaria transmission in SL by 2015
42
200,000 cases in 2000
23 in 2012
(99.99% reduction)
2012 lowest number of
malaria cases since
1963
Dramatic reduction of microscopically confirmed case load
http://www.malariacampaign.gov.lk
43. 43
SL – Malaria
Control Map
Previously
Ministry of Health
Anti Malaria Campaign
Goal -
ELIMINATION
of malaria transmission
in SL by 2015
Highest no. of cases
Kilinochchi
Mullaitivu
Vavuniya
Hambantota
Moneragala
44. Sri Lanka Malaria transmission
High risk groups
OCCUPATIONS
• construction workers working in
rehabilitation projects in North East
• persons engaged in “slash & burn” type
cultivations
• illegal gemming in dry zone
44
Traveller’s malaria -
increased travel to
malarial areas of the
world
45. References
Websites
• World health Organization: WHO - www.who.int/
• Centers for Disease Control and Prevention (cdc)
website : www.cdc.gov/
Books
1. Manson’s Tropical Diseases – 22nd
Ed
2. Worms & Human Disease – Ralph Muller & Derek
Wakelin
Atlases
• Color Atlas of Tropical Medicine and Parasitology. Wallace
Peters, Herbert M. Gilles.
