Malaria Flashcards
(23 cards)
What are Anopheline’s 9 superpowers?
- Main African malaria vector
- Breeds in manmade habitats so they can be closer to us
- Large and rapid reproductive output
- Prefers feeding on people (anthropophilic)
- Attracted to human odours
- Adapted to feed and rest indoors
- Bits in the early hours of the morning
- Intraspecies variability and therefore very adaptive to changing environments
- Multiple resistance mechanisms to insecticides
What is the Anophelines breeding site and biting habit?
Breeding sites in open, unpolluted and ephemeral e.g. hoof prints, or open permanent bodies of water e.g. rice fields
Bites at night
What aspect of the Ross MacDonald equation (basic reproductive rate) does Indoor Residual Spraying (IRS) target?
m = mosquito density p = daily survival rate of mosquito (this aspect is what has made IRS the most effective at reducing prevalence of malaria, 62%)
What are the challenges of IRS?
- Must time the spray right, yearly
- Community fatigue
- Disturbance e.g. moving furniture
- Logistics e.g. planning, infrastructure, training
- Safety e.g. need for PPE
- Insecticide resistance
What part of the Ross MacDonald equation for basic reproductive rate of malaria does long lasting insecticide treated nets (LLITN) act on?
a = daily biting frequency p = daily survival rate
50% reduction in incidence of malaria in stable transmission area
What are the advantages of LLITN?
- Protects vulnerable groups such as children under 5 and pregnant women as it is a personal protective measure
- Lasts for over 3 years and over 20 washes
- Easy to distribute through ANC and mass distribution initiatives
- Treating with insecticide means that % reduction in biting remains relatively stable even when the nets have holes (98% without holes versus 83% with holes)
What part of the Ross MacDonald equation for basic reproductive rate of malaria does larval control address?
m = mosquito density
Therefore not very effective at reducing malaria prevalence but useful when used in conjunction with other measures such as ITN
What are the challenges of larval control measures?
- Larval sites need to be contained and accessible; few and fixed; mosquitoes need to have short flight ranges
- Needs repeated applications and therefore logistically challenging
- Covering larger breeding sites e.g. River Gambia is challenging
- Resistance to some larvicides
What is the difference between relapse and recrudescence of malaria?
Relapse is the return of detectable fever and asexual parasites (merozoites, trophozoites, schizont) due to the rupture of hepatic hypnozoites (reactivation of dormant liver stage)
Recrudescence is the return of detectable fever and asexual parasites without hypnozoites (treatment ineffective)
Where are the different malaria species found?
Falciparum most endemic to SSA, but also South America and the Asia Pacific Ovale in West Africa Malariae in all of Africa Vivax in Latin America and Asia Knowlsei in Borneo
What is severe malaria defined as?
One or all of malaria with:
- Severe respiratory distress e.g. respiratory acidosis, ARDS and pulmonary oedema
- Severe anaemia due to parasitised red cells and splenic sequestration
- Impaired consciousness/cerebral malaria
All require parenteral treatment
How do you diagnose cerebral malaria?
- Clinically with GCS less than 11 or BCS less than 3
- Laboratory with presence asexual parasites on blood film
- No alternative cause of presentation
Infection: meningitis/encephalitis
Metabolic or electrolyte disturbances
Severe sepsis
What are the advantages and disadvantages of thick films for the diagnosis of malaria?
Advantages are:increased sensitivity (increases chance of seeing parasites), quick
Disadvantages are: inability to speciate easily, need to know how to use a microscope as well as pay for/maintain etc a microscope
What are the advantages and disadvantages of thin films for the diagnosis of malaria
Advantages are: able to speciate (because you see red cell morphology), calculate parasitaemia
Disadvantages: less likely to see parasites and therefore lower sensitivity, need to know how to use a microscope and have access to one/maintain one
What kind of test is a malaria RDT?
Antigen test found in Plasmodium falciparum only:
- Histadine rich protein 2 (HRP-2)
- Lactate dehydrogenase (LDH)
What are the limitations of HRP-2 RDT?
- HRP-2 persists for several weeks and therefore has reduced specificity for identifying active disease (versus recent infection) in high transmission areas
- Increasing HRP-2 gene deletion amongst falciparum and therefore danger of false negatives (reported in the Amazon basin)
- Can only detect falciparum and can’t speciate
- Can’t calculate parasitaemia
How do you treat uncomplicated malaria during the 1st trimester of pregnancy?
Quinine and clindamycin for 7 days
*Avoid ACT in the 1st trimester but can use thereafter
How do you treat uncomplicated malaria in HIV positive individuals?
ACT but avoid SP if on cotrimoxizole; and amodiquine if on efavirenz or zidovudine
How do you treat uncomplicated malaria in infants less than 5kg?
ACT mg/kg
How do you treat uncomplicated malaria by vivax, ovale, malariae and knowlesi?
ACT or chloroquine if no chloroquine resistance
Except pregnant women in their 1st trimester use quinine
What medications are used to target the hypnozoites and therefore prevent relapse in ovale and vivax malaria in children and adults?
Primaquine 0.25-0.5mg/kg daily
Except: G6PD deficient/pregnant women/children under 6 months/breastfeeding)
How do you treat severe malaria in children and adults?
IV or IM Artesunate for 24 hours
Step down to oral ACT for 3 days when they can tolerate oral medications
*Second line to Artesunate use Artemether. If Artemether not available then can resort to Quinine
How do you treat uncomplicated falciparum malaria in adults and children?
ACT for 3 days
+/- Primaquine in low transmission settings (except pregnant women, infants and breastfeeding infants) to reduce transmission
e.g. Artemether and Lumefantrine (always short acting Artemether in combination of longer acting second drug)
