Malaria Red Blood Cell Infections Biology Essay

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Malaria is caused by a parasite known as Plasmodium, a very small organism called Protozoans. When these mosquitoes (known as anopheles) bites, the plasmodium parasite injects its saliva into the blood vessel, and travels from the mosquito through the bloodstream to the liver, where the parasites begin to divide and multiply. They then re-enter the bloodstream and begin invading the red blood cells, damaging the cells -producing more parasites, which therefore maintains the ongoing cycle of invading the unaffected cells.

Aside from the above types of malaria, many have caught the illness from blood transfusions, sharing needles and also new born babies have developed malaria from their mothers who themselves were infected with the disease, so a human-to human transmission via the bloodstream took place.

In the last decade, Malaria has shown to be a serious worldwide problem, with an estimation made by (GHO) in 2008, that approximately 243 million cases of malaria were reported globally and 863,000 deaths.

It was found that 85% of these reported cases originated from African localities, with the majority of deaths being shown amongst children in Sub-Saharan Africa.

MDG6_Malaria_mortality_trends.png

Figure 1: A map summarising the reduced malaria cases from 2000-2008. (Taken from World Malaria report, 2009)

3. Prior to the current study, by what route was this pathogen believed to have come from to infect humans?

Until now scientists were uncertain to where the source of the human malaria parasite, known as Plasmodium falciparum originated from.

However, researchers found that chimpanzees carry a malaria parasite, known as Plasmodium reichenowi, which is very similar to the human malaria.

The close relationship between the two Plasmodium parasites has enabled researchers to explain that the parasites initially existed within both humans and in chimpanzees, before the split off, five to seven million years ago and so therefore have evolved from a common ancestor.

Due to the two parasite strains being so similar, scientists have clarified that malaria did not originate in humans, but was introduced by mosquitoes injecting their saliva into chimpanzees, therefore highlighting the jump from animal to human transmission.

In addition, similar to the link between the parasite carried by the chimpanzees and the human malaria parasite, studies have also confirmed that many chimpanzees carried the virus, known as SIVcpz, which was very similar to the AIDS virus that is currently spreading globally and causing high numbers of deaths.

4. What were the main weaknesses in the previous research on the topic?

In relation to the weaknesses, studies were conducted on small numbers of apes, and so sampling was inadequate. The larger the sample size for an investigation, the more significant and realistic the findings tend to be. In addition many of the apes used for the studies were held in captivity, which raises questions of accuracy, as apes in general display genetic similarities and human-like behaviour. This could put an uncertainty on the traits shown by the apes due to them living so closely to humans, making the results inaccurate.

Dr Edward Holmes and many other researchers including Dr Rayner have agreed that it was impossible for the evidence obtained from the research to determine when the cross-infection from gorillas to humans took place. There are theories to when the 'jump' took place but no actual evidence. Therefore, studies have provided evidence for what the parasite originated from but scientists have not had the opportunity to find out the true origination of when the pathogenic disease crossed from animals to humans, which is currently killing millions worldwide. (Daily Mail, 2010) (Connor, 2010)

Until the discovery of the human Plasmodium being related to the gorilla Plasmodium parasite, evidence has suggested that the reason for not distinguishing the correct relationship between the 2 parasites. This was due to the studies only being carried out on chimps so studies were limited as they did not research on other types of apes, only chimps and so did not come across the gorilla parasite (Alcock, 2010).

5. What were the key differences in the current study?

In relation to the current studies, a much larger sample size was used. The larger the sample size the more realistic the findings are so researchers can generalise with a realistic attitude.

For example, Dr Hahn of the University of Alabama at Birmingham collected 2700 samples of ape faeces, from 2 different types of gorillas-western and eastern and also used common chimpanzees as well as bonobos.

Another set of studies were conducted on 3000 specimens from wild apes, living in 57 different sites in central Africa, found that western lowland gorilla was the most likely source of the malaria parasite, which supports the findings of other studies that the malaria parasite is linked to the gorilla parasite and not linked to chimpanzees (Connor, 2010).

The above studies used a good sample size as well as using different types of gorillas and chimpanzees. This enabled the researchers to obtain a much more realistic and valid results as the researchers have a wider specie range to compare to (Alcock, 2010).

However, with research on chimpanzees studies were conducted on 94 chimpanzees that contained the malaria in Cameroon and Ivory Coast and found that eight samples of the chimpanzee parasite which were genetically linked to the human parasite.

The sample size was much smaller in comparison to the recent studies and only experimented on one type of chimpanzee, which limited the findings to a comparison of chimpanzees used within the experiment and no other type of apes (Myers, 2009).

Current research has been conducted in various locations, both in and outside of Africa, including the US and Europe, therefore increasing the reliability of the findings and so producing a much more globally generalised conclusion.

With the earlier suggestion, that the Plasmodium reichenowi in chimps and the malaria parasite was linked, provided a straightforward timescale of evolutionary malaria. However with recent findings, in regards to jumping the barrier from gorillas into human transmission, the timescale for malaria is now an unknown mystery, as researchers, including Dr Rayner believe there is no possible way of finding out when exactly the cross-infection from gorillas to humans happened, therefore the unknown mystery remains a hidden one. (Holmes, 2010) (Connor, 2010)

6. What are the main conclusions to the new research?

Many of the studies have come to the same conclusion and disproved the previous findings that chimpanzees were the reservoir of human Plasmodium falciparium, and instead it was gorilla parasite that was more similar to the human parasite.

Several studies including Liu et al have supported the above statement, where they studied 2700 ape faeces of 2 types of gorillas and 2 types of chimpanzees, and analysed the DNA from the faeces with various techniques and so separated the DNA from different species of the parasite and found that the findings supported the above conclusion that the human parasite was of gorilla origin rather than chimpanzees, disproving the earlier suggestions (Alcock, 2010).

Further investigations are being currently done in order to have a better understanding about the relationship between the human and the gorilla parasite, and so studies have begun to search for differences that the gorilla and human parasite might have.

A statement from Dr Hahn said "it is possible that they are even the same species, and that cross infection between the humans and gorillas may be going on right now" (Alcock, 2010). This statement shows that theories have been made and now need evidential findings to back up their hypotheses.

Another investigation that is currently taking place is to see whether there is a possibility of transmission between gorillas and humans at a local level. Dr Peeters and other researchers have been observing hunters and loggers in Cameroon (western Africa) to see whether the workers could potentially transmit the malaria parasite from the gorillas, as they spend a substantial amount of time in the forests within the habitats of the apes. If the findings do imply that they carry the parasite then the possibility of new infections from other species can still arise (Alcock, 2010).

In addition, researchers do not know the true effect of the parasite on gorillas and so research teams are seeking ways to find out if apes remain unaffected after catching the malaria parasite (Connor, 2010).

Studies have shown that chimps carrying the HIV virus do not show AID-like symptoms. Therefore current studies are being carried out to find out why the animals do not become ill, when humans do.

Humans share 98.4% of DNA with chimpanzees and bonobos, which raises questions to why humans react so badly to the virus, whereas chimpanzees show no symptoms towards the virus.

Enhanced sampling will enable further discoveries to be made and help determine why Plasmodium was absent in eastern gorillas and in bonobos, 'perhaps due to the animals not being infected in the first place or it is at very low prevalence' (Holmes, 2010).

7. Comment specifically on the coverage of the research in the Daily Mail,

the Independent and on the BBC website- e.g. Was it correct? Was it

clear?

All three news articles agree with the fact that, there is an evident relationship between the malaria parasite Plasmodium falciparum and the parasite found within the great apes causing the disease.

In relation to the BBC News article, they have described the research in some detail and have described the techniques used to obtain the results. The findings reflect the title of the article, and have also explained the potential for future discoveries.

This article has enabled the reader to obtain a basic understanding about the topic, and has used simple scientific terminology, so the reader doesn't necessarily need to have previous scientific knowledge.

In addition, the article is set out in essay format, where subheadings have been used to make it easier for the reader to follow. However, the article contains no images, which could have aided the reader to visualise the studies conducted and how the 'jump' from animal to human transmission took place, by the use of images within the text.

Like the BBC article, the Independent gave a brief explanation of the studies carried out, giving the reader a simple overview of the findings.

Several quotations have been highlighted in this article, where not enough explanations have been placed with the quotations, which could cause levels of uncertainty for the reader.

For example, the article briefly mentions the AIDS virus, but does not explain how the 'studies of the primate precursors of HIV have unravelled many aspects of AIDS'. This highlights that fact that the article is a very brief overview about the related topic.

In relation to the last article, the Daily Mail also describes the studies in brief but in more dept in comparison to the Independent article, as the article contained more scientific detail. This article has incorporated images within the text. However, instead of selecting an image of the animal, a relevant diagram e.g. showing the evolutionary pattern for the strains could have helped to understand the origin of the human malaria parasite.

To conclude, all of the above articles have been written by reporters which suggests that the articles itself may not be entirely reliable as the topic is about science and experts with a scientific background ought to write these articles in order for the writing to be more accurate and reliable.

News articles are normally aimed at the general public and contain less in depth scientific detail so that the general public are able to understand the science being told. However with scientific journals, the articles will contain many scientific terminologies that an audience with very little science knowledge will perhaps have difficulty understanding the depth of the science used. Therefore the target audience for scientific journals tends to be for scientists or for an audience with an understanding of scientific details, and news articles are aimed at the general public to keep them informed of new discoveries.

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