POVERTY: Neglected tropical diseases: Control, elimination or eradication?

Michael Regnier 7 Feb, 2012

 Last week, the world’s pharmaceutical companies announced new and renewed commitments to donating drugs needed to treat neglected tropical diseases (NTDs). Tackling these diseases requires more than providing hospitals and pharmacies with pills – usually, these drugs are actively distributed through mass administration programmes with the aim of controlling disease as well as treating the affected individuals. Michael Regnier spoke to Professor Moses Bockarie of the Liverpool School of Tropical Medicine to find out more about the strategies used.
There are basically three choices when deciding our response to endemic infectious diseases: control, elimination or eradication. On the face of it, it may seem obvious to pick eradication every time, but in all human history we have only managed to eradicate one disease – smallpox. Eradication is not easy, even when the characteristics of the disease in question are favourable. For many neglected tropical diseases (NTDs), control has been the most practical strategy.

Control
Control reduces the impact of a disease in a given area until it is no longer a major public health issue, explains Professor Moses Bockarie, Director of the Centre for Neglected Tropical Diseases at the Liverpool School of Tropical Medicine*. As a prime example, he describes the Onchocerciasis Control Programme (OCP), which was sponsored by four UN agencies including the World Health Organization (WHO) and the World Bank.

 Rivers like this one in West Africa were breeding sites for blackfly

Onchocerciasis, or river blindness, is caused by nematode worms that are passed from blackflies to humans. OCP began in 1974, using helicopter spraying to kill blackfly larvae in the rivers of 11 countries in west Africa. In 1987, the pharmaceutical company Merck Sharpe & Dohme (MSD, known as Merck & Co in North America) started to provide its drug ivermectin free to OCP so that the programme could expand to include a strategy of mass drug administration. The company’s donation continues today and MSD has committed to providing ivermectin free for as long as it is needed.
Bockarie says OCP was one of the most successful efforts of its kind: “It opened up thousands of acres of land for agriculture but the main outcome was it reduced onchocerciasis to a level where it was no longer of public health significance.” By 2002, transmission of onchocerciasis had been drastically reduced – almost stopped – in all of the participating countries except Sierra Leone, which was then in the grip of civil war.
According to the WHO, 600 000 cases of onchocerciasis were prevented by OCP and 18 million children born in areas where the risk of onchocerciasis is now controlled and minimal. OCP was followed by the African Programme for Onchocerciasis Control (APOC), which has extended the mass drug administration of ivermectin to the remaining African countries with endemic onchocerciasis.
The success of OCP was encouraging for similar schemes for other diseases such as lymphatic filariasis and schistosomiasis, although later efforts to implement disease control programmes were often initiated by scientists working in the field rather than international agencies or national governments. That there are several disease control programmes currently in place is a testament to the advocacy and dedication of those scientists, as well as the funders who support them and the national and international agencies that are helping to deliver the programmes on the ground.
A key feature of today’s disease control programmes is the level of coordination between them. “The common features of certain NTDs – their association with poverty, they are easily treated and the drugs are donated by pharmaceutical companies – allows for combination, improved ‘packaging’ to target them all together through preventive chemotherapy,” explains Bockarie. “Funders are happier to support these integrated programmes.”
By 2005/06, a package was in place to treat seven NTDs, saving 50 per cent on the cost of administrating each drug separately. Mass drug administration works for these diseases not only because the drugs are donated or provided at low cost, but also because the drugs can be given orally in a single dose every six or twelve months.

Elimination
Lymphatic filariasis (also called elephantiasis) is one of the diseases being controlled through integrated programmes – it is also treated with ivermectin – but it has already been successfully eliminated from China, Korea and ten African countries. Elimination means stopping transmission in a particular territory.
Elimination of lymphatic filariasis in certain countries has been possible because ivermectin is so effective, but there are other factors working in our favour, according to Bockarie: “The drug is very good, tools for diagnosis are very good. There is no natural reservoir for the parasite, so if you can eliminate it from humans, it is gone. If you reduce the parasite load in the community to less than 1 in 1000, transmission is impossible.”

 Man with elephantiasis of the lower regions, 1904

Like onchocerciasis, lymphatic filariasis is caused by thread-like nematode worms, although the worms that cause lymphatic filariasis are transmitted by mosquitoes rather than blackflies. Infection leads to thickening of the skin and other tissues, and massive swelling, particularly of the legs and male genitals. Of course, there are still many people with lymphatic filariasis in the countries where transmission has been successfully interrupted – it will take many more years for the signs of the disease to disappear.
Since OCP ended, strategies for onchocerciasis have also moved more towards elimination in certain countries. These were prompted, says Bockarie, by the recent upsurge in interest in NTDs generally. “We have the resources to monitor and evaluate progress and there is a bigger workforce available which means we can put in place protocols for effective monitoring.”
In its roadmap for NTDs published last week, the WHO says elimination of onchocerciasis is feasible in Latin America by 2015. In Africa, the WHO estimates the 12 APOC and 11 ex-OPC countries may all have achieved elimination by 2020, out of a total of 31 African countries affected by the disease.
Although onchocerciasis and lymphatic filariasis are treated with the same drug, it will not be simple to eliminate both diseases in all countries. “One of the biggest challenges is co-infection,” says Bockarie. “We can control onchocerciasis and lymphatic filariasis with existing tools but only in certain settings.”
One problem is another parasite called Loa loa, which is also sensitive to ivermectin. Unfortunately, in patients with large numbers of Loa loa parasites in their bodies, treatment with ivermectin can cause serious, potentially fatal, effects when dead Loa loa worms enter the bloodstream. So ivermectin cannot be used to treat onchocerciasis or lymphatic filariasis where Loa loa infections are also prevalent. This does not mean, however, that we have to give up.
“Different strategies are being developed,” says Bockarie, “such as more refined, higher resolution mapping.” Knowing precisely where the diseases are endemic is vital to using resources in the most efficient and effective way. The standard approach for onchocerciasis and lymphatic filariasis has been to go to a district and sample the people. If more than 1 per cent are infected, the whole district is classed as endemic and is eligible for treatment. This does not work in areas with Loa loa – mapping has to be done at the village level if the status of all three infections is to be accurately determined and the right strategy implemented.
In areas with co-infection of Loa loa, the drug albendazole can be used first to reduce the levels of Loa loa infection in order to dampen the adverse effects of treatment with ivermectin that follows. Of course, as with the early days of OCP, control and elimination efforts do not have to focus on drugs. Other approaches include using antibiotics to kill Wolbachia, a bacterium that lives in lymphatic filariasis and onchocerciasis parasites but not in Loa loa. The parasites are dependent on Wolbachia, so killing the bacterium kills the parasites. However, there are other issues with using antibiotics: treatment is over one or two weeks rather than in a single annual dose as with the antiparasitic drugs, which makes it harder to ensure people get the full course of treatment.
Targeting the insects that transmit the parasites – the flies that carry Loa loa, or the mosquitoes that transmit the worms that cause lymphatic filariasis – is called vector control, and it is an approach that Bockarie has been championing for years: “What pushed me into public health and advocacy,” he explains, “was that vector control was being ignored. The lymphatic filariasis control programme had two main objectives: drugs to reduce infection in humans, and reduce or manage morbidity. Vector control was missing. When the lymphatic filariasis programme was developing, there was no space to talk about mosquitoes.”

 Mosquitoes killed by insecticide on a treated net

Bockarie’s early training was in medical entomology – the use of scientific knowledge about insects to understand and address human disease. He began studying malaria but mosquitoes that transmit malaria also transmit lymphatic filariasis and other NTDs, although this sometimes seems to get overlooked: “In the last two to three years, we’ve seen the impact of [insecticide treated] bed nets on malaria,” he says. “But we know bed nets would impact on lymphatic filariasis as much as, if not more than, malaria – what’s happening in lymphatic filariasis?”
While the integrated efforts to control and eliminate various NTDs are growing, it seems there is a need to integrate them further with efforts against the big three infectious diseases – malaria, tuberculosis and HIV/AIDS – as well.

 Collecting water from an unprotected pond in Benin

Eradication

Eradication can be simply defined as global elimination. It was achieved in the 20th century with smallpox and we may be close to eradicating a second disease in the form of dracunculiasis, or Guinea worm disease. How? “Stop people drinking infected water,” says Bockarie. “It’ll completely eradicate it, get rid of the parasite completely.” It sounds simple, although as dracunculiasis is another neglected tropical disease, simple doesn’t necessarily mean easy, but the WHO has set a firm target in its NTDs roadmap to eradicate dracunculiasis by 2015.
Professor David Molyneux, acting chair of the UK Coalition against NTDs and one of the scientists who introduced the term ‘neglected tropical diseases’, has described progress on dracunculiasis so far as remarkable: “The total number of cases has declined from well over three million in the late 1980s to only 1060 reported in 2011. The end is in sight. What is remarkable is that this has been done without a drug or a vaccine. Applying basic public health principles – health education, case containment, surveillance, water filtration and enhanced access to safe water has been critical.
“Success is in sight but as always, the cost remains as we travel down the final mile and need to identify the last infected villages and isolate final cases.”
The Carter Center has been a particularly strong advocate for action against dracunculiasis over the past 25 years and will play a role along with a number of funders including the UK Department for International Development and the Gates Foundation in achieving the 2015 eradication target. Another NTD called yaws is set for eradication by 2020 but for the other NTDs, control and national or regional elimination strategies remain crucial.
 Professor Moses Bockarie

Implementing the strategy
Bockarie is Sierra Leonean. I finish our interview by asking him about science in Africa. Although he recognises the current lack of capacity as an important issue, he is optimistic about the growth of African science and its role in tackling NTDs.
“We have funding to support countries to achieve elimination,” he says. “This includes support for governments to do mass drug administration, operational research and capacity building. In Sierra Leone, just introducing operational research led to an increase in Sierra Leonean-led publications in the last couple of years compared to the 20 years prior to that.
“At the Liverpool School, we have part-time PhD students in Africa, basing their PhD research on the work they’re doing at home; we’ve built regional laboratories.
“We’re also working to take a more scientific approach to evaluating capacity-building,” he adds, “working to measure the effect of such programmes. Capacity-building will lead to sustainability and it will provide the local support and resource to do the required surveillance on which elimination of NTDs depends.”
This is one of a series of blog posts accompanying a Wellcome News feature on neglected tropical diseases. Next week: ‘One Health’ – why looking at human and animal health together can help in the fight against NTDs.

* The Liverpool School for Tropical Medicine and the University of Liverpool are collaborative partners in the Liverpool Wellcome Trust Tropical Centre and in the Wellcome Trust’s Major Overseas Programme in Malawi.
Related resources: The Wellcome Trust website has a number of scientific animations showing the life cycles of many parasites, bacteria and viruses that cause disease including many NTDs such as Lymphatic filariasis.
http://wellcometrust.wordpress.com/2012/02/07/neglected-tropical-diseases-control-elimination-or-eradication/#more-8966

MALARIA: Mosquitoes score in chemical war

Declan Butler : 07 Jul 2011 : Nature
Key weapons in the fight against malaria, pyrethroid insecticides, are losing their edge. Over the past decade, billions of dollars have been spent on distributing long-lasting pyrethroid-treated bed nets and on indoor spraying. Focused in Africa, where most malaria deaths occur, these efforts have greatly reduced the disease's toll. But they have also created intense selection pressure for mosquitoes to develop resistance.
"Data are coming in thick and fast indicating increasing levels of resistance, and also of resistance in new places," says Jo Lines, an entomological epidemiologist and head of vector control at the Global Malaria Programme of the World Health Organization (WHO) in Geneva, Switzerland. The WHO now intends to launch a global strategy to tackle the problem by the end of the year.
Pyrethroids are the mainstay of malaria control because they are safe, cheap, effective and long-lasting. Alternatives such as organophosphates and carbamates are available for indoor spraying, although they cost more and are less effective. But pyrethroids are the only insecticides approved by the WHO for use in bed nets. "We have lots of our eggs in the pyrethroid basket," says Robert Newman, director of the Global Malaria Programme.
The international community has been slow to respond to the threat despite warnings, says Janet Hemingway, director of the Liverpool School of Tropical Medicine, UK, and chief executive of the non-profit Innovative Vector Control Consortium, a public-private venture set up in 2005 to develop new insecticides and monitoring tools. "A number of us had been banging the drums, saying: 'As soon as you scale up you are going to get resistance.'" But Lines says that the malaria-control community felt too many lives were at stake to let the threat of resistance stand in the way of massively scaling up the bed-net and spraying campaigns.
Teasing out the impact of resistance on the success of malaria-control interventions is difficult because so many other factors influence their outcome. More systematic and more sophisticated monitoring of resistance is also vital, says Lines. The best surveillance data (see 'Resistance on the rise'), although useful, do not give a complete picture of where resistance is emerging and how prevalent it is, he says. Malaria-control programmes often lack insect-resistance monitoring, and detection of all forms of resistance is not easy. Quick, cheap tests can pick out gene mutations that help the mosquitoes' nerve cells withstand pyrethroid attack. But other forms of resistance, which depend on increased levels of mosquito enzymes that can destroy pyrethroids before they reach their target, require more complex tests to detect (H. Ranson et al. Trends Parasitol. 27, 91-98; 2011).
But uncertainties about the extent of resistance or its impact are "no excuse for inaction", says Newman, arguing that the proposed WHO strategy needs to be urgently implemented, and also rolled out preemptively in places where resistance has yet to be detected. The WHO's plan will recommend, for example, that control programmes rotate insecticides sprayed indoors, using pyrethroids one year and a different class the next. This would be more costly and less effective than relying only on pyrethroids, however, so control programmes may be reluctant to adopt this measure.
Lines says that new combinations of insecticides also need to be developed, so that mosquitoes resistant to one would be killed by the other. In areas where pyrethroid bed nets are used, a different class of insecticides should be used for wall spraying, he adds.
Ultimately, entirely new classes of insecticides — particularly those that can be applied to bed nets — are needed to alleviate the dependence of malaria-control efforts on pyrethroids. For indoor spraying, some longer-lasting and more cost-effective non-pyrethroid insecticides should be available by next year, Hemingway says, although developing wholly new classes will take five to seven years. Repurposed agricultural insecticides might also act as a stopgap were resistance to pyrethroids to develop rapidly. Research targeting mosquito control is "grossly underfunded" compared with that on malaria drugs and vaccines, she adds, which is why control efforts have had so few options to call on.
http://www.nature.com/news/2011/050711/full/475019a.html

MALARIA: Mosquitoes score in chemical war: Growing resistance is threatening global malaria-control efforts

5 July 2011 : Declan Butler
Key weapons in the fight against malaria, pyrethroid insecticides, are losing their edge. Over the past decade, billions of dollars have been spent on distributing long-lasting pyrethroid-treated bed nets and on indoor spraying. Focused in Africa, where most malaria deaths occur, these efforts have greatly reduced the disease's toll. But they have also created intense selection pressure for mosquitoes to develop resistance.
"Data are coming in thick and fast indicating increasing levels of resistance, and also of resistance in new places," says Jo Lines, an entomological epidemiologist and head of vector control at the Global Malaria Programme of the World Health Organization (WHO) in Geneva, Switzerland. The WHO now intends to launch a global strategy to tackle the problem by the end of the year.
Pyrethroids are the mainstay of malaria control because they are safe, cheap, effective and long-lasting. Alternatives such as organophosphates and carbamates are available for indoor spraying, although they cost more and are less effective. But pyrethroids are the only insecticides approved by the WHO for use in bed nets. "We have lots of our eggs in the pyrethroid basket," says Robert Newman, director of the Global Malaria Programme.


For larger image http://www.nature.com/news/2011/110705/full/475019a/box/1.html

The international community has been slow to respond to the threat despite warnings, says Janet Hemingway, director of the Liverpool School of Tropical Medicine, UK, and chief executive of the non-profit Innovative Vector Control Consortium, a public–private venture set up in 2005 to develop new insecticides and monitoring tools. "A number of us had been banging the drums, saying: 'As soon as you scale up you are going to get resistance.'" But Lines says that the malaria-control community felt too many lives were at stake to let the threat of resistance stand in the way of massively scaling up the bed-net and spraying campaigns.
Teasing out the impact of resistance on the success of malaria-control interventions is difficult because so many other factors influence their outcome. More systematic and more sophisticated monitoring of resistance is also vital, says Lines. The best surveillance data (see 'Resistance on the rise'), although useful, do not give a complete picture of where resistance is emerging and how prevalent it is, he says. Malaria-control programmes often lack insect-resistance monitoring, and detection of all forms of resistance is not easy. Quick, cheap tests can pick out gene mutations that help the mosquitoes' nerve cells withstand pyrethroid attack. But other forms of resistance, which depend on increased levels of mosquito enzymes that can destroy pyrethroids before they reach their target, require more complex tests to detect (H. Ranson et al. Trends Parasitol. 27, 91–98; 2011).
But uncertainties about the extent of resistance or its impact are "no excuse for inaction", says Newman, arguing that the proposed WHO strategy needs to be urgently implemented, and also rolled out preemptively in places where resistance has yet to be detected. The WHO's plan will recommend, for example, that control programmes rotate insecticides sprayed indoors, using pyrethroids one year and a different class the next. This would be more costly and less effective than relying only on pyrethroids, however, so control programmes may be reluctant to adopt this measure.
Lines says that new combinations of insecticides also need to be developed, so that mosquitoes resistant to one would be killed by the other. In areas where pyrethroid bed nets are used, a different class of insecticides should be used for wall spraying, he adds.
Ultimately, entirely new classes of insecticides — particularly those that can be applied to bed nets — are needed to alleviate the dependence of malaria-control efforts on pyrethroids. For indoor spraying, some longer-lasting and more cost-effective non-pyrethroid insecticides should be available by next year, Hemingway says, although developing wholly new classes will take five to seven years. Repurposed agricultural insecticides might also act as a stopgap were resistance to pyrethroids to develop rapidly. Research targeting mosquito control is "grossly underfunded" compared with that on malaria drugs and vaccines, she adds, which is why control efforts have had so few options to call on.
http://www.nature.com/news/2011/110705/full/475019a.html?s=news_rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+news%2Frss%2Fnews_s21+%28NatureNews+-+Developing+world%29

POVERTY: AFRICA: Sleeping sickness in cattle

JOHANNESBURG, 20 May 2011 (IRIN)

 Photo: Chris/Flickr
Hardier Zebu in the not too distant future

New research on sleeping sickness in African cattle is holding out the possibility that in the not too distant future Africa could start seeing the introduction of cattle resistant to sleeping sickness - a disease which kills billions of dollars worth of livestock every year.
The research claims to have isolated two genes critical in the development of disease-resistant cattle.
Harry Noyes, lead author of a paper on this published in the Proceedings of the National Academy of Sciences of the USA (PNAS) on 16 May, told IRIN their research had been prompted by the fact that while East African humped cattle breeds are susceptible to trypanosome parasites which cause sleeping sickness, the N’Dama, a humpless West African breed, is not seriously affected by the disease.
African animal trypanosomosis - also known as `nagana’ (Zulu: "to be depressed") or tryps - is transmitted through the bite of an infected species of the tsetse fly and is endemic from Senegal to Tanzania, and Chad to Zimbabwe (an area almost the size of the USA).
“The humped cattle [zebu] originated in India, where the tsetse fly is not found, while N’Dama, which probably had been exposed to [the] trypanosome parasite for thousands of years had developed a mechanism to control the impact of the disease,” explained Noyes, a senior researcher at Liverpool University.
Over the past two decades the researchers found at least 10 genes which control the impact of the disease in the N’ Dama breed.
This, of course, does not mean that poor farmers will soon have cattle that are resistant to sleeping sickness
“Out of those resistant genes we isolated what we feel are the two most significant ones for our purposes,” said Steve Kemp, a geneticist with the Nairobi-based International Livestock Research Institute (ILRI), who also collaborated on the study.
Now that the scientists know what they are looking for, they have embarked on the task of isolating humped cattle breeds which also carry the two genes.
Over the next three years, ILRI intends to breed humped cattle varieties with at least one of the genes. The humped cattle breeds produce more milk than the N’Dama.

Decades away?
“This, of course, does not mean that poor farmers will soon have cattle that are resistant to sleeping sickness,” said Kemp. ILRI scientists will only be able to test resistance in the humped cattle after three years.
Thereafter it will take decades before sleeping sickness resistant breeds find their way down the chain to small farmers, the researchers believe.
“We can make the sperm and semen available for dissemination,” said Noyes, adding, however, that it was up to governments and extension services to make it accessible to all farmers.
Developing a resistant breed is critical as most of the drugs claiming to offer immunity to the disease are proving ineffective as new and drug-resistant strains of the disease evolve, according to the researchers. Furthermore, many of the new drugs are unaffordable for poor farmers.
In the week the discovery was published, the Global Alliance for Livestock Veterinary Medicines (GALVmed), announced a five-year plan to help livestock keepers in Africa access better drugs, diagnostics and maybe even a vaccine to deal with the disease.
Initially, the programme will identify ongoing research which could help livestock farmers.
At least three million cattle die from the disease in Africa every year, according to GALVmed. An estimated 50 million cattle and 70 million sheep and goats are at risk of tryps every year. Although best known for causing human sleeping sickness, the trypanosome parasite’s most devastating blow to human welfare comes when farmers have sick, unproductive cattle, said PNAS in a press release.
http://www.irinnews.org/report.aspx?reportID=92773

MALARIA: Saudi research centre to target malaria and dengue

Marwan Almuraisy : 22 April 2011
 The new centre will be based in Jazan, south of Riyadh : Flickr/Abe World!

[RIYADH] The Middle East will soon have a research centre dedicated to the monitoring and control of insect-borne infectious diseases such as malaria and dengue.
Saudi Arabia's Ministry of Health has allocated US$5.5 million as seed funding for a joint research centre to develop innovative ways to monitor, evaluate and control major diseases transmitted by vectors, with help from the UK-based Liverpool School of Tropical Medicine and the Innovative Vector Control Consortium.
"We are very excited about this new venture with two world-class leaders in research and development in infectious diseases," said Saudi health minister Abdullah Bin Abdul Aziz Al Rabeeah at the signing of the agreement this month (4 April).
The deputy health minister, Ziad Memish, told SciDev.Net that the centre, to be based south of Riyadh in Jazan, "is expected to open in early 2012, to act as a link between the research efforts related to infectious diseases of the three parties of the agreement".
He explained that it is part of a larger effort to build national and regional capacity in science and technology. It is envisaged as a regional centre of excellence that would help develop world-class scientists though PhD and Master's courses, as well as shorter training courses.
Staff recruitment and training will start immediately, and the first project will be to develop an Arabic version of the Malaria Decision Support System — a computer package that tracks the incidence of malaria and helps efforts to control the mosquito vectors.
"The centre will trace the infectious diseases in the [nearby] countries of the region, like Yemen, which is facing a rise in the number of patients with infectious diseases compared to other neighbouring countries," said Memish.
It could help to eliminate malaria in Saudi Arabia, he added, where just over half the population is at risk from the disease, according to the WHO. Saudi Arabia is "in the final stages" of eliminating malaria, Memish said, adding that the plan is to make the country malaria-free within four years.
Najia A. Al-Zanbagi, a professor of parasitology at King Abdulaziz University, said that the centre could help Saudi scientists do world-class research. It could help limit the spread of pathogens and "encourage attempts to provide new treatments for many tropical diseases", she said.
Nuha Zelai, a biology lecturer at the same university, told SciDev.Net the centre "is like a dream that came true just in time". She said that a well-equipped centre that specialises in disease research could make it easier and quicker to obtain biological materials for research from abroad and to carry out research projects.
The project's partners will try to raise an additional US$21.5 million, which is needed for infrastructure, education programmes and research activities.
http://www.scidev.net/en/news/saudi-research-centre-to-target-malaria-and-dengue-1.html

MALARIA: the monkey reservoir

8 April 2011  James Gallagher: Health reporter, BBC News

 

A type of malaria could move from monkeys to humans, say scientists

Macaques in south east Asia are a vast source of Plasmodium knowlesi which can spread to people, they write in PLoS Pathogens.
They believe that growing human populations and increased deforestation in the region could lead to the parasite switching host.
But those changes could also reduce the spread of the disease.
Around one million people die each year as a result of malaria.
It is caused by parasites and is spread by mosquitoes when they drink blood.

'Huge reservoir'
P. knowlesi is known as the fifth malarial parasite in humans.
It mostly exists in monkeys, however, there have been human cases and it has been shown in the laboratory to be able to spread from human to human.
With increasing human populations and deforestion we may get a shift to humans”
In south east Asia, the macaques are the second most common primate after humans.
Blood tests on 108 wild macaques showed that more than three quarters were infected with the malaria parasite.
Professor Balbir Singh, from the Malaria Research Centre at Universiti Malaysia Sarawak, told the BBC: "they are a huge reservoir of Plasmodium knowlesi."
Genetic analysis showed that P. knowlesi had existed in monkeys since before humans settled in south east Asia. The researchers said humans were being infected from the 'reservoir', rather than the disease spreading between humans.
Prof Singh raised concerns about what could happen in the future: "We don't know how mosquito behaviour will change.
"With increasing human populations and deforestation we may get a shift to humans. The number of malaria cases is coming down so there is also decreased immunity. Or would deforestation reduce numbers? It could go either way."
Dr Hilary Ranson, from the Liverpool School of Tropical Medicine, said: "It seems a very reasonable thing to speculate.
"Deforestation or any perturbation of the ecosystem frequently leads to humans being exposed to an expanded range of biting insects and the pathogens they transmit, yellow fever is a good example of this."
She said if humans catch the parastite more often then P knowlesi may evolve to target humans.
"To me the important message is that disruption of the environment exposes people to a range of known and potentially unknown pathogens transmitted by blood feeding insects that do not typically feed on humans" she added
http://www.bbc.co.uk/news/health-13001294

MALARIA: New mosquito type raises concern

3 February 2011 : By Jonathan Amos : Science correspondent, BBC News

 Anopheles gambiae is responsible for the vast majority of malaria cases in Africa

 

Scientists have identified a new class of mosquito.

It is a subtype of Anopheles gambiae, the insect species responsible for most of the malaria transmission in Africa.
Researchers tell Science magazine that this new mosquito appears to be very susceptible to the parasite that causes the disease - which raises concern.
The type may have evaded classification until now because it lives away from human dwellings where most scientific collections tend to be made.
Michelle Riehle, from the Pasteur Institute in Paris, and colleagues made their discovery in Burkina Faso, where they gathered mosquitoes from ponds near villages over a period of four years.
When they examined these insects in the lab, they found many to be genetically distinct from any A. gambiae insects previously recorded.
The team grew generations of the unique subtype in the lab to assess their susceptibility to the malaria parasite and revealed them to be especially vulnerable, more so than indoor insect types.
But the scientists caution that these mosquitoes' significance for malaria transmission is not yet established.
Team-member Dr Ken Vernick, from the Pasteur Institute in Paris, said further study was needed: "We are in a zone where we need to do some footwork in the field to identify a means to capture the wild adults of the outdoor resting sub-group; so then we can test them and measure the level of infection with malaria, and then we can put a number on how much - if any - of the actual malaria transmission this outdoor resting subgroup is responsible for."
The researchers tell Science magazine the new subgroup could be quite a recent development in mosquito evolution and urge further study to understand better its consequences for malaria control.

 Larvae are collected from pools of water for study

 

Commenting on the study, Dr Gareth Lycett, a malaria researcher from the Liverpool School of Tropical Medicine in the UK, said it was an interesting advance that might have important implications for tackling malaria.

"To control malaria in an area you need to know what mosquitoes are passing on the disease in that district, and to do that you need sampling methods that record all significant disease vectors," he told BBC News.
"You need to determine what they feed on, when and where, and whether they are infectious. And where non-house-resting mosquitoes are contributing to disease transmission, devise effective control methods that will complement bed-net usage and house spraying. A recent 12m-euro multinational project (AvecNET), funded by the European Union, and led by the Liverpool School of Tropical Medicine has the specific aims of doing just this."
According to the World Health Organization (WHO), there are more than 200 million cases of malaria worldwide each year, resulting in hundreds of thousands of deaths, most of them in Africa.
Malaria is caused by Plasmodium parasites. The parasites are spread to people through the bites of infected female Anopheles mosquitoes
http://www.bbc.co.uk/news/science-environment-12352565

TUBERCULOSIS: Malawi: Tuberculosis (TB) and poverty

07 Dec 2010
Bobby Ramakant - CNS

Tuberculosis (TB) continues to affect society's most vulnerable - those who live in abject poverty, are marginalized or economically and socially isolated. The poor and vulnerable people are much more likely to suffer from TB due to socioeconomic factors. The poor face significant costs and delays in accessing TB services and treatment outcomes are more likely to be adverse, said Rachael Thomson from Liverpool School of Tropical Medicine (LSTM) who was nominated by the TB and poverty sub-working group of Stop TB Partnership to speak at the Biennial Conference of Irish Forum for Global Health (IFGH) held in Maynooth, Ireland (29-30 November 2010). The IFGH meet was organized by IFGH with support from Combat Diseases of Poverty Consortium (CDPC), Irish Aid and National University of Ireland Maynooth (NUIM).
"In urban Malawi poorer patients face costs six times their monthly income to access a diagnosis from 'free' facilities, and in rural Malawi this cost rises to ten times" said Rachael.
New TB case detection in many countries is low because the poor people are least likely to access TB care services. The process of accessing care is impoverishing making the people accessing care even poorer, said Rachael.
The lack of adequate diagnosis, treatment and cure means the burden of TB in poorer communities continues to increase.
Not surprisingly, the poor people have higher risk of infection, higher prevalence of disease and worse outcome of disease too. Moreover the poor people have greater health care needs, said Rachael.
Social and economic determinants at individual, household and community levels affect a person's vulnerability to TB.
Special situations such as massive population movements - the displacement of people and refugee flows - and living or working in vulnerable conditions also increase the risk of a person contracting TB. In developed countries, ethnic minorities and other marginalized communities are at a greater risk of contracting the disease.
There is a need to combat TB by addressing the barriers faced due to poverty such as infrastructural, housing, employment, educational and nutritional deficiencies.
Rachael explained that poverty is more than economic poverty (living on less than USD 1.25 per day) and encompasses lack of opportunities, voice and representation, and is a major determinant of vulnerability to disease - especially TB.
One of the major steps forward in addressing poverty and TB will be to put health on the poverty agenda and poverty on the health agenda, said Rachael.
Rachael gave an overview of the TB and poverty sub-group of the Stop TB Partnership. TB and poverty is the sub-group of the DOTS Expansion Working Group (DEWG) of the Stop TB Partnership and is a network of individuals and organisations interested in the needs of poor and vulnerable populations with respect to TB. Since September 2010, the secretariat of the TB and Poverty sub-working group of the Stop TB Partnership is housed in the south-east Asia regional office of The Union in New Delhi, India.
A two-days consultative workshop of the TB and poverty sub-working group was also held in Gurgaon, India on 29-30 October 2010 which brought together the national TB programme managers from India, Nepal and Thailand, state TB officers from eight poorest states of India, and partners from various other organizations like WHO, the World Bank, World Vision, GFATM Round 9 members, media (CNS, Asia Tribune), National Partnership for TB care and control in India among others, said Rachael.
http://www.reliefweb.int/rw/rwb.nsf/db900sid/MMAH-8BW7BZ?OpenDocument

MALARIA: 'Exciting' new odour sensors found in malaria mosquitoes

María Elena Hurtado
3 September 2010
An array of new mosquito repellents and lures may be possible following the discovery by researchers of a new set of sensors that the principal species of malaria-carrying mosquito uses to sniff out its targets.
Until now, research has focused on a family of odour receptors found in the antennae and other head appendages of Anopheles gambiae, the main carrier of the malaria parasite.
Work by researchers at Vanderbilt University in the United States, published in PLoS Biology last month (August), confirmed that this set of receptors is sensitive to DEET, the most commonly used repellent, and to a large number of other scents.
These receptors do not detect other important odours released by people, such as ammonia, butylamine and lactic acid. The researchers discovered a new set of receptors can detect these smells. Mike Lehane, head of the vector group at Liverpool School of Tropical Medicine in the United Kingdom, described the research as "highly skilful and exciting".
Fredros Okumu, a researcher at the Ifakara Health Institute, Tanzania, and the London School of Hygiene and Tropical Medicine, said the findings "open up even greater possibilities to screen for more compounds that could be used to compose blends of synthetic human odours that are super-attractive to human-biting mosquitoes".
The next step is to develop substances that these new receptors — known as ionotropic receptors — will respond to.
Laurence Zwiebel, senior author of the study, told SciDev.Net his team is already working on novel compounds that can both attract and repel mosquitoes. "We expect to bring these tools online in the next five to ten years," he said.
These substances could be used to lure mosquitoes to traps. Traps are being investigated to clear tsetse flies that transmit sleeping sickness and are in use to control biting mosquitoes around salt marshes in the United States.
"An efficient push-pull approach – repelling and attracting/trapping – to malaria vector control would be particularly useful in countries where mosquitoes bite outside the home, as in parts of Asia," Lehane told SciDev.Net.
"Given the good results of indoor methods for malaria control such as insecticidal nets and spraying, traps fitted with synthetic odours should especially target outdoor transmission," Okumu agreed.
"Once we have enticing lures we will need to find the best places to locate the traps and, perhaps more importantly, ensure that they at least match the cost of existing interventions," he said.
http://www.scidev.net/en/news/-exciting-new-odour-sensors-found-in-malaria-mosquitoes.html