First Cases of Malaria

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QUESTION

What is the first infected person with Plasmodium?

ANSWER

Plasmodium, the single-celled parasite which causes malaria, has been infecting humans since ancient times. In fact, the first written reference to its symptoms dates back almost 5000 years, to an ancient Chinese manuscript! It was also known from the writings of other ancient peoples, such as the Greeks, Romans and Egyptians; when Europeans arrived in the Americas, they found that local tribes had long recognised the dangers of malaria, and already had natural remedies for fever, including the bark of the cinchona tree, which was later used to make quinine (a moden anti-malarial). As such, it is impossible to say now who the first person infected with Plasmodium was, but it definitely occurred many thousands of years ago.

However, it was only until the late 19th century that people understood that Plasmodium parasites caused malaria, and knew how to observe the infection in the patient’s blood. This was done was Charles Louis Alphonse Laveran, a French physician working in Algeria. As such, you could argue that the first person known to have Plasmodium was the patient he observed the parasite within, when he first described Plasmodium. Unfortunately, the patient had died of the disease; Laveran examined the blood after the patient had perished. I am not sure the patient’s name was recorded.

What is the Meaning of the Word “Malaria”?

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QUESTION

The word malaria comes from two medievial Italian words meaning?

ANSWER

Malaria comes from “mal” and “aria,” which means “bad air.” Before the parasite that caused malaria was discovered, people thought the disease was caused by foul air, and associated it with marshes and low-lying swamps. They were not 100% wrong—those areas are perfect breeding grounds for the mosquitoes which transmit malaria, and so infection often occurs in and around these areas.

Malaria, Hepatitis and Cholera Deaths

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QUESTION

Up to now how many people died of malaria?

Up to now how many people died of Hepatitis A?

Up to now how many people died of Cholera?

ANSWER

It is believed that malaria is singly responsible for the most deaths of humans in history. However, the exact number is impossible to know. Our modern concept of disease as caused by a particular organisms or pathogen is very new, having only really developed in the 19th century, though dating back to the work of Anton van Leeuwenhoek in the late 17th century (he has since been described as “the father of microbiology”).

As such, in the past, diseases were often mistaken for each other, and particularly since malaria has such general symptoms (fever, aches, chills—these are commonly seen in many other illnesses as well), it is hard to determine what people actually died from malaria and which died from other causes. Indeed, this difficulty remains today, making it hard to estimate accurately the number of people who die from malaria even now. The World Health Organisation currently estimates that approximately 700,000 people died last year of malaria, from close to 700 million cases – this actually represents a very low death rate, thanks is large part to global efforts to improve access to diagnosis and treatment.

Hepatitis A is far less common than malaria; there are an estimated 1.4 million cases per year. Most of these are asymptomatic or mild, with a low fatality rate (4 deaths per 1000 people infected in people under 50; that rises to 17.5 per 1000 for people over 50, as older people tend to have more severe manifestations of the disease and a greater risk of subsequent liver complications – note that these data are from the CDC back in 1991). There is a very safe and effective vaccine available against hepatitis A virus (HAV)—almost 100% of people given the vaccine develop antibodies against infection.

Cholera is slightly more common than HAV (3-5 million estimated cases each year, according to the World Health Organisation) but similarly, most cases are of mild severity. Less than 20% of patients develop “typical” cholera with severe, life-threatening dehydration. 100,000-120,000 people are estimated to die from cholera each year.

How long do I need to carry a Malaria Risk Card

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QUESTION

Hello, 13 months ago I worked in Nigeria, Africa for a period of 6 weeks. During which time I took Malarone tables daily. I think I was only bitten once or twice when there – but have never had Malaria. I currently carry a Malaria Risk Card in my wallet. At the time I was told I could potentially contract Malaria up to a period of 2 years after exposure – is this correct, or can I now remove the Risk Cards from my wallet?

ANSWER

If you never had malaria while you were in Nigeria, then you certainly would not still be at risk from it now. The only case in which you might still be at risk is if you had been diagnosed with either Plasmdodium ovale or P. vivax (two of the five forms of malaria that infect humans) – these can cause relapses months or even years after initial infection.

However, as I said above, since you did not have malaria at all, this does not apply to you. It is true that malaria has a latent phase, and so can sometimes only start to cause symptoms after someone returns home from a malarial area, but this period is usually one or two weeks, and certainly not months or years!

Malaria Transmission

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QUESTION

Can one get malaria through contact with the infected person or is it airborne?

ANSWER

Malaria cannot be transmitted through direct contact with an infected person, nor is it airborne! It is actually transmitted directly via the bite of an infected mosquito. Only certain female mosquitoes, of the genus Anopheles, can carry malaria. The mosquito picks up the malaria parasite (there are five different types of malaria that infect humans, though all are transmitted in exactly the same way) when it feeds on the blood of an infected person. The parasite then undergoes a cycle of reproduction in the mosquito, before new parasites migrate once again to the mosquitoes salivary glands. From here, they are able to escape into the blood of a new human host when the mosquito takes another blood meal by biting the person.

Since malaria is transmitted by blood, there have been a some reports of malaria transmission via organ donor or blood transfusion, though most countries now screen for malaria before using donated blood or organs. Additionally, if a pregnant woman gets malaria, the parasite can be passed to her baby either across the placenta or during delivery; this is called “congenital malaria”, and can be quite harmful to the baby. As such, and also because pregnant women themselves are especially vulnerable to malaria, many campaigns have dedicated themselves to providing pregnant women with long-lasting insecticide treated bednets and other measures to prevent and treat malaria.

Aging and Malaria

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QUESTION

Is there any evidence that successfully treated malaria (when young or a young adult), has any deleterious effects for patients in their 70s and 80s? Is risk of vascular disease, stroke, or MIs any greater?

ANSWER

I don’t think there is any evidence for any long-term deleterious effects of malaria that was successfully treated, particularly if the malaria infection was non-complicated and did not result at the time in any severe cerebral complications (coma, impaired consciousness, etc).

Mosquitoes with Malaria

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QUESTION:

Do mosquitoes with malaria get sick like people do?

ANSWER:

That’s a great question! As far as I know, the jury is still out in terms of what overall effect being infected with malaria has on mosquitoes, and to a large extent, it appears to vary due to lots of factors, such as the compatibility between the mosquito and the particular type of malaria parasite, the intensity of malarial infection, and even environmental conditions, to name but a few. However, what is clear is that mosquitoes don’t seem to get ‘sick’ like we do, with fevers, chills and the like—their immune system is just too different from ours! Instead, with mosquitoes, it’s more a question of whether malaria decreases their lifespan, reduced their reproductive success, or other such effects.

A meta-analysis (Ferguson & Read, 2002, ‘Why is the effect of malaria parasites on mosquito survival still unresolved?’, in Trends in Parasitology) of studies that looked on the effect of malaria on mosquito survival demonstrated that 41% of studies reported a detrimental effect of malaria on mosquitoes, whereas 59% reported no effect (none reported a positive effect, which is interesting).

Also worth noting is that the length of the study seemed to have an effect on whether it would report a detrimental effect; this might be due to early stages of infection with malaria not having a negative impact on the host, while the malaria parasite is developing; then, once it is mature, it may be that the parasite’s virulence towards its host increases. Similarly, at this stage in its life cycle, the parasite might induce changes in the mosquito’s behaviour, encouraging it to feed more, which can result in higher mortality to the mosquito (think of swatting away annoying, biting mosquitoes, whereas you’re less likely to go for ones that leave you alone!).

More recently, a study by EJ Dawes and colleagues at Imperial College, London (2009, ‘Anopheles mortality is both age- and Plasmodium-density dependent: Implications for malaria transmission, in Malaria Journal) found evidence for the age of the mosquito and the intensity of malaria parasitism influencing mortality of the insects. Similarly, another research group found that infected female mosquites had significantly lower fecundity than non-infected mosquitoes (Gray & Bradley, 2006, ‘Malarial infection in Aedes aegypti: Effects on feeding, fecundity and metabolic rate’, in Parasitology). These examples begin to swing the balance of the debate in favour of malaria having a negative impact on mosquitoes, at least at certain points in the timeline of an infection (i.e. near the beginning, and then after parasite maturation).

You might ask why mosquitoes that are commonly infected with malaria don’t become resistant to infection, given that they seem to suffer ill-effects when they are parasitised—well, some recent research may have provided the answer to that one. Researchers looking at population growth rates in malaria-susceptible mosquitoes versus those resistant to infection noticed significantly slower growth rates in the resistant population, suggesting that in terms of reproduction, resistance at a population level might come at a cost to growth (Voordouw et al., 2009, ‘Rodent malaria-resistant strains of the mosquito, Anopheles gambiae, have slower population growth than -susceptible strains’, in BMC Evolutionary Biology). However, there may be ways in which this effect can be by-passed, in order to control malaria transmission at the level of the mosquito; one group of researchers recently published the results of a study, where they showed that when resistant and susceptible male mosquitoes rae released into a population of females (bearing in mind only the females feed on blood, and so males are not implicated in transmission), the females tend to mate first with the earlier-hatching resistant males, and moreover, lay a greater number of eggs with these males! So it may be that research on the effect of malaria on mosquitoes can be used in the future to decrease malaria transmission, which would be a hugely positive step for public health in many parts of the world.

It would be great if any malaria researchers out there would comment on the above answer, especially if there are more up-to-date examples of research on the effect of malaria on mosquitoes!

U.S. Budget Cuts May Drastically Reduce Funding for Malaria Bed Nets and Treatment Programs

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Recently the House of Representatives passed a Continuing Resolution to fund the federal budget for the rest of the fiscal year 2011. The legislation slashes programs that save the lives of some of the poorest people on the planet. These programs have been championed by Republicans and Democrats in the past, but now some of the most cost-effective programs our government funds to help combat pandemic diseases and eliminate poverty are on the chopping block. [Read more…]

Anti-Infective Drugs Market to Reach $66 Billion by 2013, Says Report

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The anti-infective drugs market will jump to $66 billion by 2013, according to a recently published report.

Anti-infective drugs include: anti-viral therapeutics, antibiotics, anti-fungal agents and prophylactic treatments such as vaccines. Six infectious diseases — pneumonia, tuberculosis, diarrheal diseases, malaria, measles and HIV/AIDS — account for half of all premature deaths worldwide. With a worldwide death toll from infectious diseases exceeding 14 million, anti-infective drugs are vital.

To date, the most successful anti-infective drugs target the human immunodeficiency virus (HIV, the virus that causes AIDS), the herpes virus (HSV-1 and HSV-2), bacterial infections and hepatitis C (HCV). Truvada, Valtrex, Cravit, Floxin, Atripla, Pegasys, Kaletra and Reyataz are among the anti-infective drugs with the highest global sales.

The report, entitled  “Anti-Infective Drugs Markets,” was produced by TriMark Publications.

The “Anti-Infective Drugs Markets” report covers:

  • Pneumonia
  • Influenza
  • Avian Bird Flu
  • Sinusitis
  • Acute Suppurative Thyroiditis
  • Complicated Skin and Skin Structure Infections (cSSSIs)
  • Lymphadenitis
  • Pharyngotonsillitis
  • Vascular Infections
  • Pancreatitis
  • Urinary Tract Infections (UTIs)
  • Viral Encephalitis
  • Reye’s Syndrome
  • Blood-Borne Infections
  • Malaria
  • West Nile Virus

The “Anti-Infective Drugs Markets” report examines companies manufacturing anti-infective drugs equipment and supplies in the world. Companies covered include: Abraxis Bioscience, Acambis, Achillion, Adlyfe, Advanced Life Sciences Holdings, Affinium, Akonni Biosystems, Alnylam, APP, Aquapharm Biodiscovery, Arbor Vita, Arpida, Avexa, Basilea, Baxter, Biophage Pharma, CEL-SCI, Cerexa, Combimatrix, Cubist, Daiichi Sankyo, Hospira, Idenix, Incyte, Medivir, Meiji Holdings, MerLion, Mutabilis, Nanobio, Nanosphere, Nanoviricides, Novabay, Obetech, Optimer, Panacos, Paratek, Pharmasset, Pico, Polymedix, Powdermed, Presidio, Progenics, Protez, Rib-X, Ribomed, Targanta, Theravance, Trius, Vertex and X-GEN.

Detailed charts with sales forecasts and marketshare data are included.

More information: TriMark Publications.

Source: Business Wire