Does malaria make you smell more attractive to mosquitoes?

Malaria parasites could change the way people smell and make them more enticing to mosquitoes, according to the findings of new research published in the journal Proceedings of the National Academy of Sciences.

Scientists based at the Swiss Federal Institute of Technology and Pennsylvania State University in the US analysed the odour of mice with and without malaria for a period of 45 days.

To their amazement, the scientists discovered that the scent of the infected mice was significantly different to the mice without the malaria parasite.

The infected mice did not have a completely different odour, however the level of compounds already in the mouse odour was altered.

This was more obvious in the mice that were still infectious but not displaying any symptoms of malaria – an important stage of the parasite’s life cycle.

Professor Consuelo De Moraes of Pennsylvania State University and one of the lead authors involved in the research said: “There appears to be an overall elevation of several compounds that are attractive to mosquitoes.”

The researchers say it is likely that infected people smell more attractive but do not have any highly specific body odours, especially as the malaria pathogen can actually have bad effects for the mosquitoes themselves.

“Since mosquitoes probably don’t benefit from feeding on infected people, it may make sense for the pathogen to exaggerate existing odour cues that the insects are already using for host location,” said study leader Professor Mark Mescher.

Most interesting of all was perhaps that the researchers found that the mice that had been infected seemed to have an alteration in body odour – permanently.

Despite these mice no longer showing any signs of the disease, tests on body odour proved they were carriers of the pathogen.

Those involved in study think it is high probable that there is a similar effect in humans and are now recruiting volunteers in Africa to determine if this is indeed correct.

Professor Mark Mescher told the BBC: “One of the major potential values of this research is if it can help us identify people who do not show symptoms of the disease. Without symptoms people carry the disease without treatment and still transmit it.

“But there is still a long way to go. In mice we have a very controlled environment. In humans there are so many different factors at play – from diverse environments to diverse genes.”

As well as hoping to advance methods of preventing malaria transmission by mosquitoes, researchers also hope to find ways of creating non-invasive diagnostic procedures that would enable the efficient screening of populations for the malaria infection, which would find those who don’t necessarily display malaria symptoms but are still able to spread the disease.

Malaria-infected mosquitoes more enticed by human odour

Malaria-carrying mosquitoes are more drawn to human scent compared with mosquitoes that do not carry the parasite, suggests the findings of a new study.

For the study, led by Dr James Logan of the London School of Hygiene and Tropical Medicine, mosquitoes carrying the malaria parasite Plasmodium falciparum were exposed to nylon socks that had been worn by one of the study authors (Renate Smallegange from Wageningen University in the Netherlands) for about 20 hours previously.

Ms Smallegange state the socks were used as ‘bait’ for the 176 mosquitoes that were analysed in the laboratory. She says: “Volatiles emitted by human feet are known to be highly attractive to Anopheles gambiae females.”

It was estimated that the infected mosquitoes were approximately three times more likely to land and try and bite on the worn socks compared to the mosquitoes without any parasite. For study purposes, the species of mosquito analysed was the Anopheles gambiae – the cause of high transmission rates of malaria in Africa. Both infected and healthier mosquitoes were not particularly keen on unworn socks that were also tested.

Experts are already aware that Anopheles gambiae mosquitoes have certain odour receptors which are effective at picking out specific human scents. The scientists involved in the study are convinced that it is the parasites which are creating a heightened craving for human smells, ergo increasing a risk of UK holiday makers being bitten in the dangerous areas for malaria.

Dr Logan was interviewed by BBC News and explained the findings in the study, commenting: “We think the parasite is giving them a heightened sense of smell. We are hypothesizing there is an alteration somewhere in their olfactory system that allows them to find us quicker,” which would make it more likely that the parasite enters the blood stream, ensuring its survival and the spread of the disease.”

The researchers conclude they are unsure how precisely the parasite alters mosquitoes’ sense of smell, in addition to which component(s) of human odour is the most is deemed most appealing to the mosquitoes as human skin emits over 350 different odour molecules. If this information could be attained from future studies, effective traps could be devised to catch the infected mosquitoes and hopefully lessen the risk of a disease that infects around 200,000 million people around the world each year, killing over 600,000.

If you are about to travel abroad and are unsure of what potential health risks there are or which medications are suitable for your area of travel, Medical Specialists Pharmacy recommend visiting the NHS Fit For Travel website.

Here you can click onto the continent and country you are about to travel to, see a highly detailed list of preventative measures to take before and during travel, what diseases are prominent in that particular country as well as a list of the symptoms of each, and also what medications/immunisations are advisable – i.e. Malarone, Paludrine and Doxycycline are all prescription medications to prevent malaria, with Malarone also able to treat the disease if you contract it. All three are available now from the Medical Specialists Holiday and Travel area of the website, where you can also find treatments for the prevention and control of travel sickness; Kwells, Kwells Kids and Avomine.

New mosquito threatens to bypass current safety measures

A potentially dangerous new malaria transmitting mosquito has been discovered in Kenya by scientists from the London School of Hygiene & Tropical Medicine. This species, which has previously been unknown, poses a threat because it bites humans at times when they are not protected by current malaria control techniques.

The commonly caught Anopheles mosquitoes that transmit malaria in Africa generally prefer to rest indoors and feed on humans at night. This led to the development of programmes to stop the spread of malaria, such as spraying insecticide in homes and issuing bed nets for people to sleep under. However, this mosquito was found to be active outdoors and bite people, earlier in the evening and soon after sunset.

Researchers said the discovery is worrying because the insect does not behave like normal mosquitoes. Already nearly one million people a year die from malaria caused by bites. But that number would be much higher if not for mosquito nets.

They prevent the female Anopheles, the main cause of the disease from biting at night, when it sucks blood as part of its egg production cycle. Nearly one million people are thought to have cheated death over the past 12 years by sleeping under nets coated with insecticide.

The new type of mosquito, however, does not wait until night time; it bites while people are outdoors in the early evening. Even more worrying for the scientists is that they are as yet unable to match the DNA of the new species to any existing mosquito variety.

Jennifer Stevenson of the London School of Hygiene and Tropical Medicine, who was part of the research group, said, “We observed that many mosquitoes we caught including those infected with malaria did not physically resemble other known malaria mosquitoes. Analysis indicated that their DNA differed from sequences available for known malaria transmitting mosquitoes in Africa.”

Researchers are worried that the daytime feeding pattern of the new tropical bug, posed a serious challenge to controlling the disease. Andrew Griffiths, from the children’s charity World Vision, said, “The findings are a setback in the worldwide battle against malaria. It’s concerning because bed nets are one of the most important tools in combating malaria and we’ve seen deaths go down dramatically.”

He added, “That while nets are not the only answer to reducing the incidence of the disease, they are one of the main ways. It would mean that one of the important parts in the response to malaria would be taken away. We have to be talking about protecting yourself at different times of the day and put even more focus on the community and other systems, without too much reliance on bed nets.”

The researchers concluded by saying that, “As these mosquitoes had so far been seen only in one location in Kenya, it was essential that tourists still protected themselves with a mosquito net, treated with a long lasting insecticidal treatment whilst travelling.”

Potentially fatal West Nile Virus sweeps across America

Have you ever heard of the ‘West Nile Virus’? If not, you probably will this week as news has emerged of the highly deadly mosquito-borne disease that is causing hundreds of deaths in the United States and health officials are bracing themselves for what could be the worst year ever for the particular virus.

The West Nile Virus (WNV) received its name after first being identified in the West Nile sub-region of the East African nation of Uganda in 1937. The condition ends up eventually effecting humans after a person is bitten by a mosquito that has previously bitten an infected bird. It is thought that the majority of cases of WNV are not serious and have no symptoms. The milder form of the disease is segregated as ‘West Nile fever’.

However, generally one in five people will feel unwell and the early symptoms are very similar to another mosquito-related disease, Malaria. They include headache, muscle aches, fever, diarrhoea, nausea, vomiting and lack of appetite. These milder flu-like symptoms will usually last for around 3-6 days. Unfortunately, there is one in 150 who go on to develop more severe symptoms, which can be sometimes life-threatening. The more serious cases can see the sufferer experience disorientation, loss of consciousness, stiffness to the neck and even paralysis.

Before the mid-1990s, WNV was relatively uncommon and not considered to be a huge risk for humans. Then in 1994, Algeria was hit with an outbreak of the virus and then Romania witness a similar occurrence in 1996. In fact it was not until 1999 that the Western Hemisphere first witnessed a case of the disease, when a diagnosis was made in New York City.

Since then, the problem has become global, which brings us to the present day. Since the beginning of 2012 there have been 118 deaths that are connected to West Nile virus according to the Centres for Disease Control and Prevention (CDC).  This has gone up from a figure of 87 reported on 2 September, meaning the death toll is rapidly increasing. The number of cases to be reported this year in total stands at 2,636 and on 2 September the number stood at 1,993, a 32% increase in less than a fortnight.

The primary area of danger appears to be in the state of Texas which is accountable for 40% of all of the latest human cases of the disease, the CDC confirmed. Other states in the U.S. that have been breakouts of the disease include Louisiana, South Dakota, Mississippi, Michigan and Oklahoma.
The previous most deadly year of the WNV came a decade ago in 2002 when approximately 3,000 severe cases of the virus were reported, resulting in 284 fatalities. Many of the deaths occur because of the fatal complications that can eventually develop, such as meningitis or encephalitis.

On the CDC website, it states: “The 2,636 cases reported thus far in 2012 is the highest number of West Nile virus disease cases reported to CDC through the second week in September since 2003.” The risks show no sign of slowing though, with Dr. Lyle Petersen, director of the Division of Vector-Borne Infectious Diseases for the CDC commenting, “We are still seeing many, many new cases continue to come in”, adding that the number of deaths is predicted to keep on rising.