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J) Public Health Medicine [Term 2] > Malaria > Flashcards

Malaria Flashcards

1
Q

The Mosquito

A
  • When it comes to killing people, the most deadly animal in the world is a tiny insect: the mosquito!
  • Unlike other dangerous creatures, mosquitoes do their deadly work by spreading diseases - one of the worst of these is malaria.
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2
Q

Epidemiological Triad

A
  • Disease is the result of forces within a dynamic system consisting of:
    • Agent of infection
    • Host
    • Environment
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3
Q

What is the Vector?

A

A vector is a carrier and spreader of disease. A vector-borne disease caused by single celled parasites, the Plasmodium protozoa, and transmitted by female Anopheles mosquitoes.

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4
Q

Aetiology of Malaria?

A

The word aetiology means: the cause, set of causes, or manner of causation of a disease or condition.

  • For malaria, it is caused by Plasmodium protozoa [there are different species]
    • Plasmodium falciparum (the deadliest)
    • Plasmodium malariae
    • Plasmodium ovale
    • Plasmodium vivax (the most common)
  • Within each species there are different strains.
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5
Q

The Life cycle of Malaria

A
  • Sporozoites infect liver cells.
  • The sporozoites mature into schizonts, which rupture and release merozoites.
    • This is of note, inP. vivaxandP. ovalea dormant stage [hypnozoites] can persist in the liver (if untreated) and cause relapses by invading the bloodstream weeks, or even years later.)
  • After this initial replication in the liver (exo-erythrocytic schizogony), the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony).
  • Merozoites infect red blood cells. The ring stage trophozoites mature into schizonts, which rupture releasing merozoites.
  • Some parasites differentiate into sexual erythrocytic stages (gametocytes).
  • Blood stage parasites are responsible for the clinical manifestations of the disease.
  • The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by anAnophelesmosquito during a blood meal.
  • The parasites’ multiplication in the mosquito is known as the sporogonic cycle.
  • While in the mosquito’s stomach, the microgametes penetrate the macrogametes generating zygotes. The zygotes in turn become motile and elongated (ookinetes)which invade the midgut wall of the mosquito where they develop into oocysts.
  • The oocysts grow, rupture, and release sporozoites, which make their way to the mosquito’s salivary glands. Inoculation of the sporozoitesinto a new human host perpetuates the malaria life cycle.
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6
Q

Malaria Transmission cycle - Summary of Life cycle

A
  • Plasmodium sporozoites
  • Enter first vector [mosquito]
  • Then the vector infects first human host
  • In the Human liver infection occurs [if its a pregnant female - then there’ll be in utero transmission]
  • Then Blood infection
  • The second vector is infected when they bite the infected first host.
  • The second host now infects the next human host, cycle continues.
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7
Q

Clinical Manifestation of Malaria

A
  • The incubation period is from 7 to 30 days (7-12, 13-15, 24-30)
  • Malaria paroxysm:comprises three successive stages
    • Chills, fever and sweating
  • Periodicity: feelings of fever chills and sweating
    • Every 48 hours for Vivax and Ovale
    • Every 72 hours for malariae
    • Every 36-48 hours for falciparum
  • Between these attacks you may:
    - feel fine [vivax, ovale or malariae]
    - Or feel miserable [falciparum]
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8
Q

Clinical manifestations of malaria in the early stages, symptoms might be similar to those of many other infections such as:

A
  • Fever
  • Chills
  • Headache
  • Fatigue, nausea and vomiting
  • Sweats
  • Dry cough
  • Muscle and or back pain
  • Enlarged spleen
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9
Q

Chiling stage [during malaria attack]

A

20 min ~ 1h feel cold and true shaking chills, accompanied with malaise, headache, vomiting or diarrhea.

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10
Q

Hot stage [during malaria attack]

A

2 - 6 hours, Temperature usually as high as 41 degrees, tachycardia, hypotension, cough, headache, backache, but normal consciousness

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11
Q

Sweating stage [during malaria attack]

A

30 min~ 1hour, Temperature falls with diaphoresis, fatigue, and weakness. Common signs: anemia, splenomegaly.

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12
Q

Clinical Manifestations of a severe attack - Cerebral malaria

A
  • P. falciparum infection, T, antimalarial drugs.
  • Obstruction of vessels and hypoglycemia.
  • Severe headache, high fever.
    Impairment of consciousness: confusion, obtundation, seizures, and coma
  • Neurologic sign: hyper-flexion and bilateral Babinski’s sign. Focal neurologic finding occurs rarely.
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13
Q

Complication [in malaria]

A
  1. Hemolytic urinemic syndrome [black water fever]
  2. Pulmonary edema
  3. Hyperreactive malarial splenomegaly
  4. Shock, hypotension
  5. Diarrhoea. jaundice, splenic rupture
  6. Anemia, hemorrhage, DIC
  7. Hypoglycemia, metabolic acidosis
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14
Q

Epidemiology of Malaria 2019

A
  • Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes. It is preventable and curable.
  • In 2019, there were an estimated 229 million cases of malaria worldwide.
  • The estimated number of malaria deaths stood at 409 000 in 2019.
  • Children aged under 5 years accounted for 67% (274 000) of all malaria deaths worldwide.
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15
Q

Malaria incidence 2018-19

A
  • Africa continues to carry the highest burden of malaria globally
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16
Q

Why is Africa the most affected area by malaria?

A
  • A very efficient mosquito is responsible for high transmission [Anopheles gambiae complex]
  • The predominant parasite species is Plasmodium falciparum, which is the species that is most likely to cause severe malaria and death
  • Local weather conditions often allow the transmission to occur year round.
  • Socio-economic status
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17
Q

Malaria in South Africa

A
  • Malaria is seasonal in South Africa (SA)
    • Peaks occurring during the rainy months from September to May.
    • January to April are the months with highest transmission each year
  • Endemic in three of South Africa’s nine provinces:
    • Limpopo,
    • Mpumalanga
    • and KwaZulu-Natal
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18
Q

Malaria Epidemiology in South Africa

A
  • By March 2017, a total of 9 478 malaria cases and 76 deaths had been reported in SA compared to 6 385
  • Factors contributing to the upsurge:
    • Rise in ambient temperature, rainfall and humidity reported over the season
    • Reduction in indoor residual spraying (IRS) in areas where malaria cases had declined in recent seasons.
    • Stock outs of rapid diagnostic test (RDT) kits and oral antimalarials for complicated malaria results in patients being referred for treatment and hospitals being overburdened malaria cases and 58 deaths in 2015/16 season.
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19
Q

Risk factors for Malaria

A

Biological factors

  • Breeding sites
  • Insecticide resistance
  • Knowledge
  • Age and health status

Human related factors

  • Migration
  • Health access
  • Gender
  • Treatment
  • Livestock

Environmental factors

  • Temperature
  • Altitude
20
Q

Who is at Risk for Malaria?

A
  • Young children and infants
  • Pregnant and breastfeeding women
  • People with HIV/AIDS
  • International travellers
  • non-immunes,
  • comorbid disease, splenectomised and immunocompromised patients(including those with HIV and AIDS, taking corticosteroids or on chemotherapy]
  • Comorbid disease and concurrent medications
21
Q

Travellers Risk factors for Malaria

A
  • The malaria risk in the area being visited
  • The length of stay in the area
  • The time of year (in areas of seasonal malaria transmission)
  • The inclusion of an overnight stay (as transmission occurs between dusk and dawn)
  • Any outdoor activities between dusk and dawn
  • The intensity of transmission and prevalence of drug resistant malaria in the area
22
Q

Predisposing or risk factors for Malaria

A
  • The type of accommodation (e.g. air conditioned rooms, camping)
  • Mode of travel (e.g. backpacking, motoring, flying) •
  • Whether the destination is rural or urban .
23
Q

Host risk factors for malaria

A
  • Disease of poverty, affecting primarily the poor who are resident in malaria-prone rural areas with poorly-constructed dwellings that offer few barriers against mosquitoes.
  • Limited formal education, poor engineering and construction, and inaccessibility of healthcare, contribute to increase malaria risk in impoverished rural populations.
  • Community beliefs can affect control, with opposition to indoor spraying, or early treatment seeking, with delays occasioned by initial care provided by traditional healers.
24
Q

Environmental Factors: Climate Factor

A
  • Climatic factorsthat directly affect malaria transmission are temperature, rainfall and humidity
  • As the temperaturedecreases, the number of days necessary to complete the developmentincreasesfor a givenPlasmodiumspecies.
  • P. vivaxandP. falciparumhave the shortest development cycles and are therefore more common thanP. ovaleandP. malariae.
  • Time needed for the parasite to complete its development in the mosquito, decreases to less than 10 days as temperature increases from 21°C to 27°C, with 27°C being the optimum
  • Below 18°C, the life cycle ofP. falciparumin the mosquito body is limited. The minimum temperatures are between 14–19°C, withP. vivaxsurviving at lower temperatures thanP.falciparum.
  • Malaria transmission in areas colder than 18°C can sometimes occur because theAnophelesoften live in houses, which tend to be warmer than the outside temperature.
25
Q

Temperature and Mosquito development

A
  • Development of the mosquito larva also depends on temperature – it develops more quickly at higher temperatures.
  • Higher temperatures also increase the number of blood meals taken and the number of eggs laid by the mosquitoes, which increases the number of mosquitoes in a given area.
  • The minimum temperature for mosquito development is between 8–10°C;
  • The optimum temperature is 25–27°C, and the maximum temperature for is 40°C.
  • As altitude increases, temperature decreases, so highlands are colder and lowlands are warmer.
26
Q

Rainfall and malaria

A
  • Anopheline mosquitoes breed in water.
  • Right amount of rainfall is often important for them to breed.
  • malaria do not breed in foul-smelling polluted water
  • Anopheline mosquitoes prefer to breed in fresh water collections created after the rainy season.
  • Such water bodies may be clear or muddy but they are not polluted.
27
Q

Drought and malaria

A
  • Lessrainfall and drought can favour mosquito breeding and malaria transmission.
  • Usually covered by vegetation throughout the year and streams and rivers often flow rapidly.
  • When the rains fail or are delayed, the flow of streams is interrupted and pooling occurs along the stream.
  • Pooling creates a favourable environment for mosquito breeding.
  • Malaria vectors mainly breed in stagnant water collections, rarely in slightly moving waters and never in rapidly flowing rivers and streams.
28
Q

Humidity and mosquitoes

A
  • Mosquitoes survive better under conditions of high humidity.
  • They also become more active when humidity rises. This is why they are more active and prefer feeding during the night – the relative humidity of the environment is higher at night.
  • If the average monthly relative humidity is below 60%, it is believed that the life of the mosquito is so short that very little or no malaria transmission is possible.
29
Q

Non climatic factors [with regards to malaria]

A
  • Malaria vector:
  • Water development projects
  • Unplanned rapid urbanization
  • Population movement and migration
  • Population movement
  • Population displacement
30
Q

Malaria vector as a factor affecting malaria

A

A. gambiae group are very good vectors of malaria is that they prefer to bite humans more than animals.

  • Mosquitoes that feed on humans and animals equally are much weaker vectors of malaria.
  • The type of Anopheles mosquitoes and their feeding behaviour influence the intensity of transmission in an area.
  • Mosquitoes adapted to breeding close to human settlements, and able to breed in a wide range of environments
  • A. gambiae mosquitoes breed in a wide range of habitats, including small water collections such as hoof-prints, water-filled holes in rocks and trees, as well as dams, river beds and lake shores.
  • Stagnant water collections in borrow pits, ponds, micro-dams, pools in small rivers, and streams created immediately after the rainy season, are the most important breeding habitats for this vector.
31
Q

Water development projects as a factor affecting malaria.

A
  • Irrigation channels, dams and ponds, can increase the incidence of malaria in villages that are located near such projects.
32
Q

Unplanned Rapid urbanisation

A
  • crowded;
  • housing is often of poor quality or is of temporary construction;
  • The provision of health care and sanitation is often inadequate.
  • Settlers tend to dig several pits to extract stone and soil for house construction, creating numerous breeding grounds for mosquitoes.
33
Q

Population movement and migration

A
  • People moving from the highlands to the malaria-endemic lowlands as seasonal labourers.
  • Employed as daily labourers in the crop fields during the planting and harvesting seasons when malaria transmission is at its peak.
  • Poor living conditions and inadequate health care in such agricultural projects often worsen the problem of malaria.
  • Migrants from malaria-free highlands lack immunity against the disease, as well as the appropriate knowledge of the transmission process and how to avoid being bitten by mosquitoes.
34
Q

Population movement

A
  • Major environmental transformations like deforestation, and new construction etc, take place during resettlement, enhancing the proliferation of mosquito breeding sites, and resulting in major malaria outbreaks.
  • Population movements and migration also make the malaria problem worse.
  • Temporary migrant workers often bring the parasites back to the malaria-free highlands and local transmission can be readily established as many of these communities could support vector breeding.
  • Such sporadic epidemics could affect a large number of people, as the population in malaria-free areas is generally non-immune.
35
Q

Population displacement

A
  • War and civil unrest, or natural causes like drought and famine, flooding and earthquakes, etc.
  • Displaced people from areas with malaria can introduce or reintroduce malaria into areas that are malaria free, and in some cases spread drug-resistant malaria.
  • Displaced populations can in some cases be at a higher risk of getting sick or dying from malaria because:
    • Displaced people may not have proper housing.
    • They often camp near water bodies that serve as mosquito breeding sites.
    • They could be non-immune, if moving from malaria-free to malaria-endemic areas.
    • Malnutrition can worsen the malaria problem.
    • The health care system can be overburdened, so there may be very limited malaria care and preventive measures
36
Q

Insecticide and Drug Resistance

A
  • The mosquitoes may developinsecticideresistance, which means that they are no longer killed by the insecticides.
  • This means a large number of mosquitoes will survive in the community, and the risk of malaria infections rises and many people can be affected.
  • drug-resistant malaria parasitesare not cleared by treatment from infected individuals, they are easily picked up by vector mosquitoes, and transmitted to new susceptible individuals who then develop drug-resistant malaria. Moreover, more people who are not getting cured by drug treatment means that more will die of malaria.
37
Q

Reducing malaria Disease Burden:

A
  • The ABC of malaria prevention
    • A- awareness and assessment of malaria risk
    • B- bites by mosquito avoidance
    • C- compliance with chemoprophylaxis
    • D- detection [early] of malaria disease
    • E- effective treatment
38
Q

Mosquito Bite Avoidance:

A
  • Remain indoors between dusk and dawn
  • wear long sleeved clothing, long trouser, socks when going out at night
  • close doors at night
  • apply a DEET containing repellent to exposed skin
  • Use mosquito mats
  • Use mosquito nets
  • ceiling fans and air conditioners are very effective
  • Treat clothes with an insecticides registered for this purpose e.g. a pyrethroid
39
Q

Early diagnosis of malaria

A
  • Malaria should be suspected in any person presenting with any of the symptoms, who has a history of travel to or is resident in a malaria transmission area, irrespective of the time of year or whether or not they have taken chemoprophylaxis
40
Q

Effective treatment of malaria

A
  • Malaria must be treated as a medical emergency. The sooner effective treatment is started, the better the prognosis.
  • Treatment of uncomplicated malaria
41
Q

Main methods for control of malaria

A

Control patient
Control of patients contacts
Control of immediate environment
Malaria surveillance systems

42
Q

ERADICATION VS ELIMINATION

A

Eradication = Permanent reduction to zero of the worldwide incidence of malaria as a result of time-bound deliberate efforts. Intervention measures are no needed once eradication has been achieved.

Elimination = Reduction to zero of the incidence of malaria in a defined geographical area as a result of deliberate efforts. Continued measures to prevent re-establishment of transmission are required.

43
Q

Shared commonalities between the countries successfully eliminated malaria.

A
  • Political stability
  • Good infrastructure
  • High quality of training and personnel
  • Developed and functional health system
  • Absence of internal or external conflict
  • Absence of major population movement from neighboring malaria-endemic countries.
  • Malaria originally unstable or of low-grade intermediate stability
44
Q

Is malaria elimination feasible in Africa now?

A

Maybe yes - in some settings because it depends on the local epidemiological context “one size does not fit all”

45
Q

Elimination programs

A
  • They detect and cure malaria patients
  • Interrupt local mosquito-born malaria transmission
  • Identify and eliminate residual foci of malaria transmission
  • Develop and implement special surveillance system for maintaining the malaria free status.
  • Prevent re-establishment of transmission despite continuing importation of parasites
  • Collaborate with neighboring endemic countries to reduce malaria transmission in the region

J) Public Health Medicine [Term 2] (10 decks)

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