Malaria Flashcards
What is the pathogen that causes malaria?
These are four species of plasmodium
Plasmodium falciparum
Plasmodium malariae
Plasmodium vivax
Plasmodium ovale
What is the main method of transmission?
Insect vector: female Anopheles mosquito (about 30 different species)
What is the global distribution of malaria?
Tropics and subtropics (endemic in 106 countries)
What is the incubation period?
From a week to a year
What is the site of action of the pathogen?
Liver, red blood cells, brain
What are the clinical features of malaria?
Fever, anaemia, nausea, headaches, muscle pain, shivering, sweating enlarged spleen
What is the method of diagnosis?
Dipstick chest for malaria antigens in blood microscopy examination of blood;
signet ring appearance
What was the annual incidence worldwide in 2017
219, million cases of malaria in 90 countries (WHOS estimate) 92% of cases are in Africa
What was the annual mortality rate worldwide in 2017?
435,000 deaths (WHO estimate) 93% of deaths were in Africa
What does the genetic analysis of the infection of malaria show that some species of plasmodium that cause malaria in monkeys also affect
Humans
What is a disease vector?
An organism which carries a pathogen from one person to another or from an animal to a human
What is a disease vector?
An organism which carries a pathogen from one person to another or from an animal to a human
What is the disease vector of malaria?
The female Anopheles mosquito and she transmits the disease when she passes the infective stages into an uninfected person
What is infected stage?
The stage during which the pathogen takes a form in which it can invade its host cell
Apart from mosquitoes, what are some other methods of transmission of malaria?
It can be transmitted
during blood transfusion
when unsterile needles are reused
The pathogen can also pass across the placenta from mother to fetus
Describe the process of transmission by female Anopheles mosquitoes
-Female Anopheles mosquito feed on human blood.
-If the person they bite is infected with Plasmodium, they will take some of the pathogen’s gametes with the blood meal
-male and female gametes fuse in the misquote’s gut and develop to form infective stages.
-the infective stages move to the mosquito’s salivary glands.
-when the mosquito feeds again she injects an anticoagulant from her salivary glands that prevents the blood meal from clotting so that it flows out of the host into her body.
-The infective stages passes from the mosquito’s salivary glands into the human’ blood together with the anticoagulant
-The parasites enter the red blood cells where they multiply
Why do the female Anopheles mosquitoes feed on human blood?
To obtain the protein they need to develop their eggs
When is the transmission of pathogens of malaria more intense?
When the mosquitoes have a longer lifespan so that the parasite has time to complete its development inside the mosquito
When it prefers to bite humans rather than other animals
Why are about 90% of malaria cases in the world are in Africa?
They have a long lifespan
They have strong human biting habit
Most of the cases in Africa are caused by which pathogen
Plasmodium falciparum
Which species causes the most severe and often fatal malaria
Plasmodium falciparum
Why is the transmission of malaria seasonal in some places?
Because transmission also depends on climatic conditions which affect the number and survival of mosquitoes. And many places the peak of transmission is during and just after the rainy season.
What are the climatic conditions that affect the number of transmission of malaria?
Rainfall patterns, temperature and humidity
What are the climatic conditions that affect the number of transmission of malaria?
Rainfall patterns, temperature and humidity
When can malaria epidemics occur?
When climate and other conditions suddenly favour transmission in areas where people have little or no immunity to malaria.
They can also occur when people with immunity move into areas with intense malaria transmission
If people are continually re infected by different strains of malaria, they become immune. However, this only happens if
They survive the first five years of life when mortality from malaria is very high
The immunity from malaria only lasts as long as
people are in contact with the disease. This explains why epidemics in places where malaria is not endemic can be very serious as well as places were malaria only occurs seasonally.
Why does malaria have a disastrous effect on economy when malaria is seasonal
Because it coincides with the time of maximum agricultural activity; people cannot cultivate land when they are sick
WHO recommends that all cases of suspected malaria are first
Confirmed by using a test that shows the presence of plasmodium before treatment is started
The results of the test of malaria can be available within
30 minutes or less
What are some examples of antimalarial drug used to treat infected people?
Quinine and chloroquine
Chloroquine is also used
As a prophylactic (preventative) drug, stopping an infection occurring if a person is bitten by an infected mosquito.
When are prophylactic drugs taken?
Before during or after sitting in area where the disease (malaria) is endemic
How does chloroquine work
It inhibits protein synthesis and prevents the parasite spreading within the body
Apart from chloroquine, what other prophylactic drug is used to treat malaria
Proguanil
What added advantage does proguanil have?
Inhibiting the sexual reproduction of plasmodium inside the biting mosquito
Where anti malarial drugs have been used widely, there are
Strains of drug resistant plasmodium- the drug is no longer effective against the pathogen
Chloroquine resistance is widespread in
Parts of South America, Africa and Southeast Asia
What drug is used in areas where the pathogen are resistant to chloroquine
Mefloquine
Why is mefloquine not the preferred drug for malaria?
Because it causes unpleasant side effects such as restlessness, dizziness, vomiting, and disturbed sleep.
Why is mefloquine not the preferred drug for malaria?
Because it causes unpleasant side effects such as restlessness, dizziness, vomiting, and disturbed sleep.
Resistance to mefloquine has developed in
South east Asia
What is the best available treatment particularly for malaria caused by Plasmodium falciparum is
Artemisinin based combination therapy(ACT). These are drugs derived from the plant Artemisia annua used in combination with another drug such as mefloquine
Doctors in developed countries who see very few cases of malaria often misdiagnose it as
Influenza since the initial symptoms are similar
Why do some people not take prophylactic drugs?
Many of this cases are settled immigrants who have been visiting India or Africa to meet their relatives. These people do not take the prophylactic drugs because they do not realise that they have lost their immunity.
______ % of the worlds population lives in areas where there is a risk of malaria
40
______ % of the worlds population lives in areas where there is a risk of malaria
40
What are the three main ways of controlling malaria?
-reduce the number of mosquitoes
-avoid being bitten by mosquitoes
-Use prophylactic drugs to prevent plasmodium infecting people
What are the three main ways of controlling malaria?
-reduce the number of mosquitoes
-avoid being bitten by mosquitoes
-Use prophylactic drugs to prevent plasmodium infecting people
What is the most effective method of controlling malaria?
To kill the insect vector
Describe how mosquitoes give birth and their babies are grown
Mosquitoes lay their eggs in water. Larvae hatch and develop in water but breathe air by coming to the surface.
What are two ways that can be used to kill the insect vector and break the transmission cycle in malaria?
Oil can be spread over the surfaces of water to make it impossible for mosquito larva and pupae to breathe
Marshes can be drained and vegetation cleared to reduce breeding sites for the mosquitoes
What are two biological control measures that can be used to prevent malaria?
-stocking ponds, irrigation and drainage ditches and other permanent bodies of water with fish which feed on mosquito larvae
-spraying a preparation containing the bacterium Bacillus thuringienesis which kills mosquitoes larvae but it’s not toxic to other forms of life
Why is it impossible to eradicate malaria even after the control measures?
Because the mosquitoes will lay their eggs in any small puddle or pool which makes it impossible to completely eradicate breeding sites, especially in rainy seasons
The best protection against malaria is
To avoid being bitten
How can one avoid mosquitoes?
Use mosquito nets treated with a long lasting insecticide
Use insect repellent
When are mosquitoes the most active?
Usually at dusk
How does using mosquito net treated with long lasting insecticide reduce mortality rate from malaria significantly? How often is it recommended to replace the nets
These nets prevent mosquitoes from biting and kill any mosquitoes that lands on the nets
Insecticides are also sprayed inside houses to control malaria. For how long is this control effective?
Between three and six months depending on insecticides used and the type of surface on which there are sprayed
Who is at the most risk of dying from malaria?
Young children
The WHO recommends that pregnant woman are treated with (in regards to malaria)
A prophylactic drug each time the visit an antenatal clinic in the latter 2/3 of their pregnancy
WHO recommend that infants living in high transmission areas in Africa are given (in regards to malaria)
Doses of three doses of the same drugs (prophylactic drugs) when they attend clinic for routine vaccinations
No introduction of simple dipstick tests for diagnosing malaria means
The diagnosis can be done quickly without the need for laboratories
The whole channel of plasmodium has been sequenced, and this is leading to
Developments of new treatments and vaccines
What is RTS,S/AS01 (RTS,S) also known as
Mosquirix- is an injectable vaccine that provides partial protection against malaria in young children
What are the three factors that may lead to improvements in the control of malaria?
- use of modern techniques in gene sequencing and drug design
- Development of vaccines, targeted against different stages of the parasite’s life cycle
-A renewed international will to remove the burden of malaria from the poorest parts of the world, allied to generous donations from wealthy individuals and foundations
