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Malaria - Coggle Diagram
Malaria
Life cycle and transmission
It is at the blood stage of infection that the person will become infectious and demonstrate symptoms of malaria. When a mosquito feeds on the infectious human host they will ingest parasites and start the vector lifestyle.
The plasmodium parasite requires two distinct lifecycles to occur, one in a vertebrate host and the other in a mosquito vector, in order to successfully transmit infection.
The malaria lifecycle starts when a mosquito infected with Plasmodium parasites takes a blood meal from a human. While feeding, the parasites are injected into the human host where they move to the liver and invade the liver cells where they mature. Once the liver parasites are mature they will rupture releasing large quantities of merozoites into the blood stream. Within the cell where they mature and then rupture releasing hundreds more parasites into the circulation.
This process occurs every 24-48 hours and results in the number of parasites increasing exponentially each cycle.
Anopheles mosquitoes are native to every continent except Antarctica. This geographical distribution correlates not only to malaria-endemic regions, but also to countries that are potentially vulnerable for the establishment of active malaria transmission.
Anopheles mosquitos are either nocturnal or crepuscular, will prefer to feed either indoors (endophagic) or outdoors (exophagic) and prefer to rest indoors (endophillic) or outdoors (exophillic)
Blood borne disease and as such it is possible for parasites to be transmitted from human to human. This form of transmission can occur through blood transfusions, liver transplants. or the reuse of blood contamination needles and syringes.
Clinical symptoms
First observed symptoms: fever, headache, chills, sweating, muscle fatigue, nausea and vomiting. These symptoms are often mild and nonspecific and therefore it is difficult to diagnose.
If the correct treatment is not given quickly enough, malaria infections can rapidly progress to severe illness and often death.
Usually appear 10-15 days after the infected mosquito bite
Children with severe malaria experience high fever, prostration, altered consciousness, lethargy, coma, respiratory distress, severe anaemia, convulsions and cerebral malaria. Adults with malaria may experience organ failure.
The Spatial and Temporal Distribution of Malaria
Global distribution of malaria transmission
Malaria transmission is restricted to tropical and subtropical regions extending between the Tropic of Cancer and the Tropic of Capricorn.
There were 91 countries found to be endemic for malaria transmission with 15 of these countries accounting for 80% of the cases.
The majority of the malaria cases occur in the African Region, follows by South East Asia.
Climate change, economic development, antimalarial resistance, and implementation of malaria eradication policies are all variables that have significantly influenced the spatial distribution of malaria
Due to economic development MEDCs are able to eradicate active transmission.
Biophysical processes influencing malaria transmission
Temperature
The duration of the Plasmodium lifecycle within the mosquito vector is highly dependent on the ambient temperature. The higher the temperature, the faster the cycle. Min temp for parasite development is 18, max is 40.
Altitude
Influences the transmission of malaria indirectly, through its effect on temperature, as altitude increases, temp decreases. Malaria is a disease where transmission is highest at lowland
Rainfall
In many regions, transmission is seasonal with the highest rates occurring during the wet monsoonal season, when constant water breeding sites are available.
Rainfall that is collected in ditches, storm drains, rice fields, tree holes, artificial containers, and house gutters are all potential breeding grounds for mosquitoes, as they breed in stagnant, standing fresh water.
Relative humidity
Affects mosquito activity and survival. Mosquitos are more active and survive better in areas of high humidity as they can avoid dehydration. If the monthly humidity is less than 60%, the lifespan of the mosquito is so short that malaria transmission cannot occur.
Vector Lifespan
Malaria transmission is higher in areas where the mosquito vector can live longer. The duration of the parasite lifecycle is 8 to 15 days and the adult Anopheles mosquito has a lifespan of one to four weeks. If the mosquito dies before the completion of the parasite lifecycle it is not capable of transmitting malaria.
Biting preference
Mosquitos have a preference of blood, transmission rates are correlated to regions where the Anopheles vector preferentially feeds on humans, rather than animals.
Climate Change
As Climate change may cause an increase un the global temperature and altered precipitation patterns, it is expected that there will be a shift and redistribution of malaria endemic countries.
Human processes influencing malaria transmission
Malaria is also effected by the economic status of the country, hence why malaria is called the 'epidemic of the poor'. Developing nations generally a reduced ability to maintain well-resourced health infrastructure, invest in vector control measures and have a large proportion of the population living in impoverished conditions. The three human factors that most importantly influence transmission are economic status, maintenance of safe water and sanitisation and ability to participate in control strategies.
Prevention diagnosis and treatment
Diagnosis
Rapid Diagnostic test (RDT): A droplet of blood is mixed with active reagent onto a filter paper card. If malaria is present, the reagent will change colour and form a positive line on the card.
Microscopy: Droplets of patients blood are placed on a glass slide and viewed under a microscope. Malaria is diagnose by visualising the parasites within patient red blood cells.
Presumptive diagnosis: Diagnosis based on the clinical symptoms that the patient exhibits
There have been over 50 antimalarial drugs used in the clinical setting for malaria treatment. However due to the emergence of drug resistant parasites, most of these treatments have been rendered useless.
Protection and Prevention
(treatment)
Indoor Residual Spraying (IRS): Used in areas were native mosquitos have endophillic tendencies. A coating of insecticide is sprayed onto the walls and internal roof were mosquitos rest. 12 Chemicals are used and rotated regularly to prevent resistance.
Chemoprophylaxis: Intermittent preventive treatment in pregnancy (IPTp) and in infants (IPTi) are policies adopted in several malaria endemic countries. Antimalarial drugs that protect the vulnerable.
Long Lasting insecticide treated nets: Reduces parasite transmission from the human to mosquito then back to humans. Polypropylene nets are treated in pyrethroid insecticides, that instantly kill the mosquito. People are encourage to sleep with these due to mosquitos nocturnal endophagic tendencies.
The nature of the risks to be managed
Morbidity and Mortality
In 2016, the WHO reported an estimated 216 million cases of malaria. The majority of which were reported in population groups who have an immature or weakened immune system; young children, pregnant women, HIV/AIDS patients, or travellers from non-malaria endemic regions.
Children under the age of five years are the most vulnerable population and account for more than two thirds of malaria related deaths.
In 2016, the African region dominated the number of morbidities accounting for 91% of all malaria related deaths.
Effect on jobs and the economy
Significant economic impact: Due to the cost of health care, absenteeism from work, the number of days lost in education, decreased productivity, and loss of international investment and tourism. It is estimated that the economic cost of malaria yearly is $12 billion dollars.
It is suggested that greater than 70% of African businesses report that malaria has a negative impact and is considered 'bad for business'. It results in significantly decreased productivity, increased employee absenteeism, increased company health care costs and can often have a negative impact on the company's reputation.
One African business reported that in 2012 it had 10% of its workforce absent from work and a total of 1,644 working hours lost to malaria
Each household will lose up to 25% of their annual income due to malaria infection
Interventions working towards the global control and elimination of Malaria