Malaria Flashcards
1
Q
What mosquito transmits malaria?
A
Female anopheles mosquito.
2
Q
- Which species of malaria parasite afflict humans? (in order of increasing prevalence)
- Which causes most deaths?
A
- P. falciparum
- P. vivax
- P. ovale
- P. malariae
- P. knowlesi
- Falciparum most severe, causes most deaths
3
Q
- What is the global burden of malaria disease?
- How many cases?
- How many deaths?
A
- 214 million cases per year
- 438,000 deaths
4
Q
- How many deaths per year from Malaria?
- What percent in Africa?
- What percent in Kids?
A
- 438,000
- 90% in Africa
- 7% in SEARO
- 70% in kids
5
Q
- How much has the incidence of malaria fallen this century?
A
- Since 2000 the incidence of malaria has fallen by 37%
6
Q
- What is the geographic distribution of the various species of malaria in order of global prevalence?
A
- P. falciparum: throughout tropics and subtropics, esp. sub-Saharan Africa
- P. vivax: south, SE asia; East Africa, largely absent west Africa; Amazon
- P. ovale: pred West Africa, Phillipines, East Indonesia, Pap New Guinea
- P. malariae: throughout tropics & subtropics (but much less prev than falciparum)
- P. knowlesi: Zoonotic species, restricted to SE Asia: Borneo and peninsular Malaysia
7
Q
- Name four geographic factors affecting the distribution of malaria.
A
- Temperature: affects life cycle of mosquito
- Altitude: restricted to altitudes below 1500 m
- Seasonality: more common in wet season due to mosq. life cycle
- Population movement.
8
Q
- Name the 6 forms malaria parasite takes during its life cycle.
- Briefly describe each.
A
- sporozoites - dormant stage injected into human host via pregnant female anopheles salivary glands, travels to and infects liver cells
- schizonts - host liver or red blood cell containing mature forms soon to rupture, divides (schizogeny) then releases merozoites
- merozoites - parasite stage released from liver or rbc, then goes on to infect rbc’s
- trophozoites - developing intra-erythrocytic parasite phase visible on blood film
- gametocytes - sexual stage of parasite life-cycle that go on to infect mosquito, where they combine to form oocytes, which develop into sporozoites
- hypnozoites - a dormant form of P. ovale and P. vivax which can hide in the liver to cause relapses
9
Q
- What are the usual symptoms of malaria?
A
- very non-specific
- fever
- rigors
- headache
- myalgias
10
Q
- What species of plasmodium cause severe malaria?
A
- P. FALCIPARUM FAR AND AWAY MOST COMMON CAUSE OF SEVERE MALARIA, others known as “benign malaria”.
- P. vivax and knowlesi also cause it but much less common
11
Q
- Describe the classical malaria fever patterns and which species of malaria they are associated with.
A
- Not a reliable guide, but pts may report “paroxysms” of rigor
- Tertian malaria, fever about every 48 hrs
- P. falciparum, vivax, ovale
- Quartan malaria, fever about every 72 hrs (q 3rd day)
- P. malariae
12
Q
- What are WHO criteria for severe malaria due to P. falciparum.
A
- Peripheral blood parasitemia plus one of:
- impaired consciousness (including unrousable coma)
- prostration, i.e. generalized weakness so that the patient is unable to sit, stand or walk without assistance
- multiple convulsions: more than two episodes within 24h
- deep breathing and respiratory distress (acidotic breathing)
- acute pulmonary oedema and acute respiratory distress syndrome
- circulatory collapse or shock, systolic blood pressure < 80mm Hg in adults and < 50mm Hg in children
- acute kidney injury
- clinical jaundice plus evidence of other vital organ dysfunction
- abnormal bleeding
13
Q
What makes falciparum more severe than the other “benign” species?
A
- ability to parasitize all ages of erythrocytes (and therefore reach high levels of parasitemia)
- ability to ‘sequester’ in blood vessels - adhere to capillary endothelial cells, obstructing microvasculature and causing ischemia
14
Q
What is the treatment of severe falciparum malaria?
A
- IV artesunate
- if unavailable give iv quinine until available or follow with ACT
15
Q
What is treatment for non-severe falciparum?
A
- Oral artenisin based combination therapy (ACT) x 3 days
16
Q
- Which are the “benign” malarias and how are they treated?
A
- P. vivax, ovale, malariae, knowlesi
- Treate with Chloroquine or ACT
- ACT if any doubt about dx of parasite or mixed infection or if P. vivax infection from areas of chloroquine resistance (Indonesia and parts of Oceania).
17
Q
- What is the ABCD of malaria prevention?
A
- Awareness of symptoms of malaria
- Bite Prevention: repelants, insecticide treated bednets
- Chemoprophylaxis of malaria if necessary
- Diagnose and treate symptoms promptly
18
Q
What is Ro and what is its significance?
A
- the number of infections introduced into a fully susceptible host (human).
- If Ro>1, infection will spread.
- Goal for eradication is to get Ro<1.
19
Q
- Describe the Blantyre Coma Scale and How to Score it.
A
- Motor
- Pressure to fingernail bed: 0=no response or extensor response only. If withdrawal then pressure to supraorbital ridge or sternum.
- withdrawal =1
- pushes the hand away =2
- Verbal
- no response = 0
- moan or abnormal cry = 1
- normal cry or speech = 2
- Visual
- unable to open eyes = 0
- able to close eyes to avoid light or blink to visual threat = 1
- able to track moving object, eg face of examiner = 2
20
Q
What are the microscopic characteristics of P. Falciparum?
A
- immature ring forms predominate (more mature forms generally sequestered): nucleus stains red, cytoplasm appears as blue-stained ring
- RBC’s remain normal in size
- multiple invasion: may have single RBC infected by >1 trophozoite
- some rings have double chromatin rods
- accolé forms, parasite lies flat along membrane of cell
- high numbers of trophozoites
- older trophozoites:
- Maurer’s dots
- knobs (distinguish from artefactual crenation of rbc’s due to osmotic drying)
-
schizonts rarely seen except heavy parasitemia or resistant strain
- haemozin (haemosome, Malaria pigment) produced as end product of Hgb breakdown
- appears as brown-black refractive granules within infected red cell
- haemozin (haemosome, Malaria pigment) produced as end product of Hgb breakdown
- lipid trigger causes some parasites to develop into gametocyte
-
crescent shaped sexual forms which reinfect mosquito
- female bluish cytoplasm, compact nucleus
- male reddish cytoplasm, diffuse nucleus
-
crescent shaped sexual forms which reinfect mosquito
21
Q
P. falciparum thick film:
What can be seen?
A
- red cells lyzed, so see
- trophozoites and
- gametes
- appearing to be extracellular
22
Q
In what clinical situations do you see malarial pigment/haemozin?
A
- Red cells, late stage infections
- White blood cells
- may be seen in absence of other stages of parasites
- sometimes post treatment
- pts (esp children) with chronic malaria
23
Q
- What are the factors that influence the severity and outcome of malaria?
A
- Host factors
- genetic
- specfic immunity
- age
- nutrition
- HIV
- adherence
- pharmacokinetics
- Parasite Factors
- species
- drug resistance
- ?virulence
- Circumstances
- access to health care and early treatment
- drug efficacy
- drug quality
24
Q
How do incidence and prevalence of malaria relate to the age distribution?
A
- In areas of high incidence and prevalence the disease afflicts primarily children under 5 and pregant women.
- As the incidence and prevalence of malaria decline it afflicts relatively more older children and adults because they did not acquire immunity in early chilhood.
25
Q
What technical factors may influence the diagnosis of malaria?
A
- diagnosis based primarily on interpretation of thick film
- exerptise may be lacking or thick film may not have been properly examined
- ngegative films do not exclude malaria due to
- poor interpretation
- partial treatment
- prophylaxis
- Rapid Diagnostic Tests are sensitive for falciparum and vivax
- Films should be repeated 3 x if clinical suspicion of malaria is high
26
Q
4 terms referring to types of recurrent malaria.
Name and define them.
A
- Recurrence = any return of malaria after previous clear smear.
- Relapse = recurrence of malaria in P. vivax and P. ovale infection because of hypnozoite
- Recrudescence = recurrence of malaria in any malarie species due to failure to completely eliminate parasites (treatment failure)
- Re-infection = NEW infection with malaria (bitten by mosquito again).
27
Q
What are the clinical features of uncomplicated malaria?
A
- fever in over 90%
- Non-specific symptoms
- fever, ‘flue-like’ illness, headache, rigors, sweats, jaundice, respiratory or GI symptoms.
- high index suspicion necessary
28
Q
Which species of malaria form liver hypnozoites?
A
P. vivax
P. ovale
29
Q
In which species of malaria does sequestration play a big role in pathogenesis?
In which species will parasitemia reflect the total parasite load?
A
- Sequestration of p. falciparum plays a large role in pathophysiology via impaired microcirculation leading to widespread tissue ischemia and acidosis.
- In P. vivax, ovale and malariae, parasitemia reflects total parasite load
30
Q
What are the four cardinal features of severe malaria in children?
A
- cerebral malaria
- severe anemia
- respiratory distress/acidosis
- hypoglycemia is common
- due to impaired liver glycogenolysis
- poss effect of quinine
31
Q
What is the clinical significance of respiratory distress in severe malaria?
A
- represents acidosis due to widespread tissue ischemia due to impaired microcirculation and anemia
- indicator of physiological decompensation and a powerful predictor of mortality in children not given a blood transfusion
-
HOWEVER
- as incidence of malaria declines, overdiagnosis remains a possibility and
- parasitemia in high transmission setting does not always mean the cause of presentation is malaria.
- ALWAYS consider other diagnoses as well
32
Q
- How common is raised ICP in cerebreal malaria?
- Should children with suspected cerebral malaria have Lumbar puncture?
A
- ICP is common in children with cerbral malaria (up to 50%).
- however in over 1000 children with suspected cerebral malaria, no evidence of LP’s leading to excess mortality, even if signs of raised ICP.
- So yes, they should have LP unless there are signs of impending herniation.
33
Q
- How common are seizures in children with severe malaria?
A
- very common
- may be febrile seizure brief with quick recovery of consciousness.
- true seizures occur in 80% of children with Cerebral Malaria
- often complex, or prolonged, may be subtle
- may only be detectable on EEG = a trial of treatment may be warranted.
34
Q
What is the pattern of severe malaria in adults?
A
- most symptoms are attributable due to sequestration of falciparum and disruption of micro-circulation leading to multi-system failure including shock, DIC, acidose
- cerbral malaria
- renal failure
- severe anemia relatively rare
- pulmonary edema problematic
- older children behave like adults
35
Q
- What species of malaria cause severe disease?
A
- falciparum most commonly associated with severe disease because most prevalent in sub-Saharan Africa and because of sequestration and effects on microcirculation.
- however increasing recognition that p. vivax and p. knowlesi can also cause severe malaria
36
Q
- What is the pattern of mortality for children with severe malaria?
- For adults?
A
- case fatality rates for severe malaria remain between 15 & 20%
- children tend to die early
- in first 24 hours of admission
- adults die later with multi-system disease
37
Q
- What supportive therapies are useful in Severe Malaria?
- Which ones are NOT?
A
- YES
- antipyretics, acetaminophen
- transfuse if appropriate
- renal support if required
- glucose
- anticonvulsants if required
- fluids
- NO
- hyperimmune serum
- dexamethasone
- mannitol
- adrenaline
- dopamine
- heparin
- prophylactive anticonvulsants
- anti-TNF monoclonals
- desferrioxamine
38
Q
What are the indications for transfusion in severe malaria?
A
- low transmission setting
- hgb<7g/dl (hct 20%) if clinically stable and AT ANY HGB IF SIGNS OF DECOMPENSATION
- High transmission setting
- hgb<4 g/dl (hct 12%) if clinically stable and AT ANY HGB IF SIGNS OF DECOMPENSATION
- use lower thresholds (<7g/dl) if resp distress, acidosis, heart failure or shock, impaired consciousness (rapid if resp distress/acidosis).
39
Q
How dow you define and manage hypoglycemia in severe malaria?
A
- severe malaria definition <2.2, in practice <3.0
- Initial tx:
- 5 ml/kg 10% D10W IV rapidly
- Maintenance
- D10W in NS or RL for maintenance
- Avoid concentrations over 20%
40
Q
- At what levels of parasitemia should malaria be considered and treated as severe?
- Discuss
- What is the realationship between parasitemia and regional levels of transmission.
A
- Laloo: consider as severe hyperparasitemia (>10% circulating erythrocytes infected)
- (also treat as severe, monitor closely if parasitemia 4-10% because of risk of rapid progression).
- WHO: high parasitemia undoubtedly a risk factor for mortality, but level at which sig varies with regional transmission rates. In areas of low transmission, parasitemia >2% may be associated with sig mortality. In areas of higher transmission areas of higher transmission tolerated. Levels > 20% associated with high risk in any epidemiological context.
41
Q
How do you distinguish adult female anopheles from culicines?
A
- Different palp lengths: female anopheles have long palps, longer than their antennae; culicines have short palps
- Resting position of abdomen relative to substrate: female anopheles tilted up, culicines down
- large spots on anterior edge of wing in Anopheles
42
Q
- How are female anopheles wings different from culicines?
A
- The anterior edge of their wings have spots.
43
Q
- How do you tell femal anopheles from culicines by palp lengths?
A
- anopheles female palps are longer than antennae, culicines are short
44
Q
- How do you tell female anopheles from culicines by body position when feeding?
A
- anopheles tail points up to sky, culicines is angled down
45
Q
- How do you tell anopheles larvae from culicines?
A
- orientation: anopheles larvae are parallel to surface of water, whereas culicines are angled down and anchored to the surface by a
- siphon
46
Q
- What diseases or parasites do anopheles transmit?
A
- malaria
- plasmodia
- lymphatic filiarisis
- Wuchereria bancrofti
- Brugia malayi
- viral
- O’nyong nyong
47
Q
How big is an erythrocyte?
A
- Approximatel 6-8 µm diameter
- 1-2.5 µm thick
48
Q
Describe the gametocyte of p. falciparum.
A
- Crescent-shaped
- Male and female can be distinguished from each other by their different staining reactions; the female has a bluish cytoplasm and a compact nucleus, the cytoplasm of the male is much redder in colour.
49
Q
Describe the appearance of P. vivax.
A
- Main criteria:
- large pale RBC
- Schuffner’s dots
- round gametocytes
- large ameboid trophozoite with pale pigment
- red cells are 1.5-2 times larger than normal
- shape normal or oval
- Schuffner’s dots present in all stages except early ring form
- occasional red cells with multiple parasites per cell
- all stages of trophozoite present in peripheral blood
- ring form: ring 1/2-1/2 diameter of cell
- heavy chromatin dot
- developing schizont:
- enlarged, chromatin divided into two or more discrete red areas, but cytoplasm not divided, malaria pigment present
- mature schizont: 12-24 merozoites in rosette filling entire RBC
- gametocytes round or oval
50
Q
Describe the appearance of P. ovale
A
-
Main Criteria:
- Oval RBC with fimbriated edges characteristic but not alwasy present; generally like P. vivax
- In P.ovale although both parasite and red cell do increase in size, the red cell remains more oval in shape, with fimbriated (jagged) ends while the parasite is more compact.
- As for P. ovale, red cells are 1.5-2 times larger than normal
- shape normal or oval but differ from P. ovale in that some have irregular fimbriated edges
- As for P. ovale:
- Schuffner’s dots present in all stages except early ring form
- occasional red cells with multiple parasites per cell
- all stages of trophozoite present in peripheral blood
- ring form: ring 1/2-1/2 diameter of cell
- heavy chromatin dot
- As for P. ovale and P. malariae:
- developing schizont: enlarged, chromatin divided into two or more discrete red areas, but cytoplasm not divided, malaria pigment present.
- Mature shizont : 8-12 merozoites (P. vivax has 12-24)
51
Q
Describe P. vivax (Main Criteria only)
A
- Main criteria:
- large pale RBC
- Schuffner’s dots
- round gametocytes
- large ameboid trophozoite with pale pigment
52
Q
Describe the appearance of P. Malariae.
A
- In P.malariae the parasite is quite solid and stretched across the red cell which is often smaller than normal, termed microcytic.
-
Main Criteria:
- Red Cell normal or slightly smaller
- trophozoites compact and intensely stained
- band form suggestive
- no Schuffner’s dots
- coarse and dark pigment
53
Q
Describe the schizont of P. vivax
A
- Schizonts are round with
- 12-24 merozoites in rosette filling entire RBC
- Schuffner’s dots visible
- haemozin may also be seen
54
Q
Describe P. vivax gametocytes.
A
- Gametocytes are large, solid, and usually rounded, filling most of the infected red cell. There is a single chromatin mass (nucleus) which is either compact (female gametocytes) or more diffuse (male gametocytes)
- The parasitised red cell is enlarged and schűffners dots are usually visible.
- Fine pigment granules may be scattered throughout the cytoplasm (centre and right above)
55
Q
Describe P. ovale trophozoites.
A
- parasites generally more compact than p. vivax
- Schuffner’s dots
- Oval shape, with some having fimbriations is diagnostic (up to 30% will have this)
56
Q
Describe the P. ovale Schizont.
A
- Round form
- 8-12 merozoites
57
Q
Describe P. ovale gametocyte
A
- round form, solid in appearance, filling most of RBC
- Schuffner’s dots may be seen around periphery
58
Q
Describe the appearance of p. malariae younger trophozoites.
A
- younger ring form may initially appear similar to young ring of p. falciparum; but both nucleus and cytoplasm are thicker and stain more deeply
- ‘solid ring’ form: chromatin may be rounded or streaky, cytoplasm is usually fairly compact
- ‘birds eye form’: nucleus situated in middle
- may be haemozin present in parasitized red cell
59
Q
Describe older trophozoites of p. malariae
A
- band form diagnostic: nucleus and cytoplasm stretched across middle of host red cell
- basket form: parasite more oval with vacuole forming the basket
- chromatin usually single mas
60
Q
Describe P. malariae Schizonts
A
- seen in normal sized or smaller (microcytic) red cells
- 8-12 merozoites often arranged in rosette or irregular cluster
- generally low level parasitemia but high proportion of circulating parasites may be schizonts
61
Q
Describe P. malariae Gametocytes
A
- compact, tend to fill host rbc
- nucleus and cytoplasm often deeply stained
- no enlargement of rbc and may be microcytic
62
Q
- Insect Repellants
- List 5 types and efficacy
A
*
63
Q
What is the differential for typical xray picture of miliary TB?
A
- histoplasmosis
- sarcoid
- varicella
- pneumonitis
- berylliosis.
64
Q
Describe the identifying characteristics of P. vivax shizont & gametocyte.
A
- developing schizont:
- enlarged, chromatin divided into two or more discrete red areas, but cytoplasm not divided, malaria pigment present
- mature schizont: 12-24 merozoites in rosette filling entire RBC
- gametocytes round or oval
65
Q
Describe the appearance of P. vivax gametocyte.
A
- P. vivax gametocytes are round to oval with scattered brown pigment and may almost fill the rbc
66
Q
What is this?
What are the diagnostic features?
A
- P. falciparum thin smear.
- nucleus (chromatin dot) stains red while cytoplasm of parasite stains blue
- some rings have double chromatin dots
- in some red cells parasite lies flat along membrane of the cell (accolé form)
- some red cells contina more than one parasite (multiple invasion of red cell)
67
Q
Describe the features of p. falciparum on a thin smear.
A
- multiple invasion
- high rate of parasitemia
- accolé form
- double chromatin dot
- in attached picture note scanty cytoplasm of young ring form trophozoites
68
Q
What is this?
What are the distinctive features?
A
- P. falciparum: older trophozoites
- both nucleus and cytoplasm have become thicker and coarser
- a few Maurer’s dots (clefts) may be seen in t the cytoplasm of the red cells
- these irregular reddish dots are another diagnostic feature of older trophozoites of P. falciparum and can be used to distinguish from Schuffners dots in P. vivax/P. ovale.
69
Q
What is this?
Describe the characteristics.
A
-
P. falciparum Schizont
- normally occur in capillaries of spleen, liver and brain
- not often seen in blood except heavy parasitemia or resistant strain
- nucleus begins to divide, then cytoplasm, producing mature schizont with 16-32 merozoites
- nb hemozoin
- schizont rupture blocks brain caps leading to cerebral malaria, coma, death
- toxins produce typical malaria attack
70
Q
What is this?
A
- P. falciparum gametocytes
- crescent shaped gametocytes diagnostic
- distinguish by different staining reactions: female bluish cytoplasm and compact nucleus, male redder or pink
- do not develop further unless ingested by female Anopheles mosquito
71
Q
What is this?
What are the advantages, differences from thin film?
A
- P. falciparum thick film
- red cells piled thickly, irregularly, not fixed with methanol prior to staining.
- aqueous stain allows red cells to hemolyze, leaving purple staining white cells
- malaria parasites appear extracellular
72
Q
What is this?
A
- P. falciparum gametocyte in thick film
- likely male because of reddish tinge to cytoplasm
- crescent shape identifies as p. falciparum
73
Q
What is this?
A
- as p. falciparum infections often intense, WBC’s containing hemozoin may often be seen after phagocytozed
74
Q
Describe malaria life cycle.
A
75
Q
What is this?
Characteristics?
A
- P. vivax mature trophozoite
- both parasite and red cell become very enlarged and ameboid in shape
- Schuffner’s dots present in both Ovale and Vivax
76
Q
what is this?
Characteristics?
A
- P. ovale
- both parasite and red cell increase in size but red cell remains more oval in shape, with fimbriated ends in 20%
- parasite more compact
- Schuffners dots present in both Ovale and Vivax, but there are more present in Ovale
77
Q
What is this?
A
- P. malariae thin film - basket form
- In the picture below parasite is solid and streteched across red cell, which is often smaller than normal (microcytic)
- no Schuffner’s dots
78
Q
What is this?
In what species is it found?
How are they treated?
A
- hypnozoites in liver ceslls, found in P. Vivax and P. Ovale
- dormant stage leading to Relapsing Malaria occurring months or years after initial infection
- round, intra-cytoplasmic, non-dividing, uni-nucleate bodies about 5 µm in size.
- similar to but smaller than schizonts, also found in liver tissue
- detectable by immunofluorescence (right) 36-40 hours after sporozoite inoculation
79
Q
What is this?
Characteristics?
A
- P. vivax trophozoites, mature
- parasitized red cell enlarged and irregular in shape, increasing as parasite develops
- parasite also irregular or ameboid shape
- large red nucleus, often to one side
- cytoplasm blue, forming large, irregular mass
- Schuffner’s dots visible.
80
Q
What is this?
Characteristics?
A
- P. vivax trophozoite, mature
- parasitized red cell enlarged and irregular in shape, increasing as parasite develops
- parasite also irregular or ameboid shape
- large red nucleus, often to one side
- cytoplasm blue, forming large, irregular mass
- Schuffner’s dots visible.
81
Q
Describe the features of P. vivax
A
- large (macrocytic) red cell
- ameboid irregular cytoplasm of parasite
- ameboid shape to parasitized cell
- trophozoite cytoplasm stains blue with large heavily staining red nucleus
- cytoplasm increasinly large and ameboid as parasite matures
- Schuffner’s dots
82
Q
What is this?
Characteristics?
through maturation?
How long does it take?
A
- P. vivax schizont
- in early schizonts as nucleus begins to divide, cytoplasm remains dense
- as nuclear division continues cytoplasm also begins to divide and surround nuclei forming merozoites
- mature schizont may contain 16-24 merozoites
- schizogony complete after ~48 hrs
- parasitised rbc enlarged, Schuffners dots present
- haemozoin may also be seen
83
Q
What is this?
Characteristics?
A
- P. vivax gametocytes
- large, solid, usually rounded, filling most of rbc
- Single chromating mass (nucleus) either compact (female gametocyte) or more diffuse (male)
- left male, right female
84
Q
What is this?
characteristics?
A
- P. vivax thick film
- enlarged late trophozoites of P. vivax ameboid, irregular in shape and size on thick film
- cytoplasm may appear fragmented
- Schuffners dots may be seen as pink ‘halo’ around some of larger parasites, giving useful indication of size and shape of original red cell before lysis
- large round or oval gametocytes and developing schizonts may be seen
85
Q
What is this?
Characteristics?
A
- P. ovale younger trophozoite
- well stained, compact ring form
- red cell slightly enlarged, round or oval shape
- parasites gen more compact than P. vivax with Schuffner’s dots
*
86
Q
What is this?
Characteristics?
A
- P. ovale older trophozoite
- large nucleus, large solid cytoplasm
- red cell macrocytic
- schuffners dots clearly visible
- some fimbriation (seen about 30%, diagnostic)
*
87
Q
Describe characteristics of P. ovale.
Of late troph.
A
- macrocytic red cell, but not as large as P. vivax, may be better defined
- oval shaped
- fimbriation diagnostic, but only seen in 20-30%
- Schuffner’s dots
- large parasite with more cytoplasm than early trophozoite
88
Q
What is this?
characteristics?
A
- P. ovale schizont
- red cells sl enlarged, round or oval shape
- up to 30% fimbriated ends
- parasites more compact than p. vivax, with Schuffner’s dots visible
- Schizonts 8-12 merozoites when mature
89
Q
What is this?
characteristics?
A
- P. ovale gametocyte
- macrocytic cell, but smaller than p. vivax
- Schuffner’s dots
- gametocyte round and solid, filling most of infected cell , schuffner’s dots around periphery
- malarial pigment (hemozin) in later stages
90
Q
What is this?
Characteristics.
A
- P. malariae
- infected cell is normal size or smaller
- younger ring form may appear superficially like young P. falciparum ring form, but both nucleus and cytoplasm are thicker and stain more deeply.
91
Q
what is this?
characteristics
A
- microcytic red cell
- chromatin round or streaky
- cytoplasm usually fairly compact
- “solid ring form”
92
Q
What is this?
Birds eye form of P. malariae
A
- microcytic rbc
- some rings may appear to have nucleus located in middle
- “bird’s eye” form
93
Q
what is this?
characteristics?
A
- P. malariae Band form
- now as trophozoites mature, nucleus may be stretched across middle forming “band form”
- diagnostic as P. malariae
- malarial pigmen granules become larger, tend to have more peripheral arrangement, may be yellowish and refractive
94
Q
A
- P. malariae basket form
95
Q
Describe characteristics of P. malariae
A
96
Q
A
- P. malariae young schizont
- microcytic red cell
- 8-12 merozoites
97
Q
A
- P. malariae mature schizont
- 8-12 merozoites, arraged in rosette or irregular cluster
- nearly fill host red cell , pigment is coarse, golden brown and usually cntral
- Schizonts can be common in peripheral blood circulation
98
Q
What is this?
A
- P. malariae gametocyte
- compact, tend to fill hospt RBC
- nucleus and cytoplasm often deeply stained
- abundant dark refractile pigment may be scattered through the cytoplasm
99
Q
What is this?
What groupings of organism may be seen?
Where.
A
- mixed infection with P. falciparum and P. vivax
- common in South-East Asia, this one from Thailand
- P. falciparum mixed with p. malariae often seen West Africa
127
Q
What is the effect of Malaria in Pregnancy on the Mother?
Compare Low Transmission with High Transmission Areas.
A
- increases the rates of fever, severe anemia and severe malaria (cerebral malaria, hypoglycemia, renal failure, pulmonary edema)
- this is more pronounced in areas of Low Transmission (because of lack of prior exposure and immunity)
- in areas of High Transmission, these effects occur to a lesser extent and malaria infection is more likely to be assymptomatic
- increases the rates of Heavy Placental Infection with malaria
- more pronounced in areas of High Transmission because of density of infection and lack of placental immunity in primigravids and 2nd babies
- in areas of high transmission, all effects are seen primarily in primigravids; in areas of low transmission the risk applies to all pregnancies.
129
Q
What is the Effect of malaria in pregnancy on the fetus?
Compare High and Low Transmission Areas.
A
- in areas of high transmission, affect primarily primigravids; in low transmission, applies to all parities
- Increased risks include
- Low Birth Weight
- IUGR esp primis in HTA
- preterm deliveries esp all preg in LTA
- Abortion/stillbirth esp LTA
- Congenital Malaria more likely to be symptomatic in LTA
- Fetal anemia
- additionally it appears that in HTA there is reduced placental transfer of Ab and cellular immunity to the fetus (e.g. to Tetanus, measles, Strep. pneumonia). This effect may be present in LTA, but has not been demonstrated.
- Other possible effects include poor developmental and behavioural outcomes, poss increase risk of metabolic disease, short stature.
- Low Birth Weight
142
Q
Outline the treatment guidelines 2015 for treatment of Malaria in pregnancy.
A
- nb quinine resistance for Vivax very rare.
146
Q
Distinguish between WHO definitions of Control, Elimination and Eradication of Malaria (2006)
A
- in pre-elimination phase slide positivity rate in fever cases is <5%
- in elimination phase <1 case/1000
- between 2000 and 2015 17 countries eliminated malaria (0 cases for 3 yrs), 6 certified as having eliminated malaria, UAE, Morocco, Turkmenistan, Armenia, and most recently 2016 Kyrgyzstan and Sri Lanka.
148
Q
What is the Ross MacDonald Model?
- What does it take account of?
- What does it not account for?
A
- Factors in the Ross-MacDonald model
- Mosquito factors
- # of female mosquitoes per human host
- average lifespan of mosquitoes
- biting rate of mosquitoes on humans
- (has to bite at least twice to spread infection)
- extrinsic incubation period, i.e. time for a mosquito to become infectious after biting an infected human
- mosquitoes must survive this incubation period to transmit disease
- extremely important as temp affects development rate so highly affected by environment
- Human Factors
- length of a human infection
- Mosquito/human interactions
- susceptibility of mosquitoes to malaria, i.e prob of acquiring infection when biting
- susceptibility of humans to malaria, ie prob of human acquiring infection when bitten
- Mosquito factors
- Does not account for human immunity or
- “Superinfection” - where through repeated bites, a person is infected with more than 1 strain of parasite
152
Q
Stable vs Unstable malaria
What determines the difference?
A
- stability determined by the average # of feeds that mosquito takes on human during its life - the stability index a/u. Threshold of 2.5 differentiates
- stable malaria - insensitive to natural and man-made perturbations
- unstable - very sensitive to climate and amenable to control
- intermediate range between them
153
Q
What is the geographic distribution of the 5 species of malaria?
A
- Falciparum
- through tropics esp SSA & Melanesia
- Vivax
- Central/S. America, N. Africa, Middle East and India/Pakistan
- Ovale: West Africa
- Malariae: Worldwide
- Knowlesi: Borneo and peninsular Malaysia
163
Q
Re Malaria prophylactic drugs:
- What areas are still chloroquine sensitive?
- Where is chloroquine/mefloquin resistant plasmodium reported>
A
- chloroquine sensitive: Central America and Caribbean, Egypt, northern parts of Arabian Peninsula, northern Argentina
- Chloroquine/mefloquine resistance: South East Asia (Thai, Cambodia, Laos, Myanmar)
- (one thing that may influence slowness to develop resistance is latitude. Cooler latitudes are areas of unstable malaria where mosquito barely has time to feed 3 times so likely very little mosquito superinfection and little opportunity for malaria genetic change.)
