Tag Archives: malaria

Now is the Time to Coordinate Efforts between Malaria and Lymphatic Filariasis Control

malaria, NTDs,

 

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Image: Flickr user 4Cheungs/CC

By: Greg Simon

A new study published in the New England Journal of Medicine further strengthens the evidence that sleeping under insecticide treated bed-nets (ITNs) helps to eliminate Lymphatic filariasis (elephantiasis or LF) and malaria.

Lymphatic filariasis (elephantiasis or LF) is a parasitic-worm infection that affects approximately 120 million people worldwide. The World Health Organization (WHO) estimates that 120 million people suffer from LF — one-third of which have been disfigured or debilitated by the disease. The WHO has a goal of eliminating LF as a public health problem by the year 2020. With approximately 1.4 billion people living in endemic areas, the task is an enormous one which will require multiple interventions. Global efforts to eliminate LF have been based on the annual mass drug administration (MDA) of anti-filarial drugs to reduce the microfilaria reservoir available to the mosquito vector. While the stand alone MDA approach can work in areas where the infection rate is low, areas with high infection rates may need to incorporate other measures to reduce the incidence of LF.

The New England Journal of Medicine study titled: “Insecticidal Bed Nets and Filariasis Transmission in Papua New Guinea,” studied five villages in which five annual MDAs were performed in cooperation with ITN distribution. According to the research, the ITNs block female mosquitoes from securing blood, which is essential for them to produce offspring; the insecticide also cuts in half the insect’s life span, preventing the parasite from being transmitted.

The study noted the rates of bites from mosquitoes were reduced 6.4 to 61.3 bites per person per day before the bed-net distribution to 1.1 to 9.4 bites for 11 months after distribution. During the same period, the rate of detection of parasite in mosquitoes decreased 78%, and the rate of detection of filarial DNA decreased 23%.  The study found the annual transmission potential was 5 to 325 infective larvae inoculated per person per year before the ITN distribution and 0 after the distribution. It noted that among all five villages with a prevalence of parasite of 2 to 38 percent, the probability of transmission cessation increased from less than 1.0 percent before the bed-net distribution to a range of 4.9 to 95 percent in the 11 months after distribution.

While this study demonstrates the power of combined interventions to prevent both LF and malaria, it is not the first. Another successful program was a five-year malaria treatment program in Togo initiated in 2005 and funded by the Global Fund to Fight AIDS, tuberculosis and malaria. In addition to providing artesunate plus lumefantrine for treatment of malaria, this program also provided ivermectin and albendazole treatment via MDA to populations at risk for LF and malaria.

The current international financial crisis has caused many donors to concentrate on funding programs that can demonstrate high cost-effectiveness. Many organizations have found it necessary to integrate multiple programs in order to increase efficiencies and reduce costs. Hence, incorporation of simple, inexpensive interventions that causes little interference to the main program(s). This study provides excellent examples of ways to combat two different diseases that use the same mechanisms of infection and that affect millions of people world-wide. Linking these disease controls can also promote effective partnerships with national strategic plans and country ownership; investment in human capital; introduction of innovative financing strategies and improvement in health service delivery models.

Trinidad and Tobago. A Success Story in the Fight Against NTDs.

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This Caribbean country has succeeded in controlling or eliminated most NTDs. Dr. Dave Chadee, Professor of Environmental Health at the University of the West Indies, shares his vision about this success story, and highlights ideas that can be applied in other countries where the Neglected Tropical Diseases Initiative for LAC is implementing several projects.

Dr. Chadee, what is the situation regarding NTDs in Trinidad and Tobago?

The situation regarding NTDs in my country is quite different from that of our neighbor’s. The country has eliminated lymphatic filariasis (LF) as well as malaria, and leprosy has been reduced to less than 1 case in every 100,000 inhabitants so it is no longer considered a major public health problem. We have also reduced the incidence of hookworms and recent surveys have not found cases of this infection. Today, the NTDs that are still considered a real challenge are yellow fever, which still persists in some pockets in forested areas (a zoonosis), and dengue, the most extensive  and problematic vector-borne disease in Trinidad and Tobago and the Caribbean region.

Dr. Dave Chadee

In your opinion, what are the main factors that have helped control and eliminate these diseases in the country?

Well, first of all the fact that Trinidad and Tobago has an universal, free to all health care system that has helped in controlling or eliminating most of the local and imported diseases. This is an advantage compared to other countries in the Caribbean region, because offering free treatments to all for any NTD makes it easier for people to seek help when they need it, no matter their ability to pay for these services and whether they are nationals or non nationals.

I also think that having staff that have received specific training on NTDs is key, and not only do they need to acquire the knowledge: they need to keep informed of new developments in their field by receiving updates or refresher training.

Another success story for the country involves the strategy against NTDs – which involves continuing monitoring and evaluation activities. We know of programs that have implemented wonderful strategies but did not incorporate internal audits to check their effectiveness, strengths and weaknesses over time, significantly reducing the efficacy of the programs.

Last but not least, I believe that the political support of local authorities is key, both for the implementation of effective programs and to keep morale high among health workers. NTD work can be tedious because it is a battle that is never complete, so keeping the morale of the teams high, making workers feel appreciated, is very important.

What is the importance of vector management in the fight against NTDs?

Our experience has demonstrated that integrated vector management can help combat these diseases more effectively. At my university we have developed vector control strategies that are effective against Culex quinquefasciatus and other container breeding mosquitoes. Also, our research demonstrates that integrated vector management can be useful if used together with mass drug administration programs, and can help raise awareness about LF and other NTDs among communities.

Based on your latest research about transmission of LF, what are the changes you have observed in the habits of the Culex mosquito in the last years?

Based on my research, there is evidence that the blood feeding times of the Culex quinquefasciatus mosquito, the main vector for the transmission of LF, have shifted significantly. Previous studies showed the peak biting times in Trinidad and Tobago was between 10 pm and 3 am. Now we are finding a bimodal pattern with an early peak between 7 and 9 pm, as well as the 10-3am peak. This shift may be due to any of several factors like the use of air conditioning and fans in the household and the change of light regimens in cities such as the use of indoor lights and security lights from dusk to dawn. This means that the Culex mosquitoes  have access to people  between 7 and 11 pm, when they  are relaxing  at home and are likely to be casually dressed and  exposing larger skin surface area to foraging mosquitoes. In addition, our preliminary study shows more biting in areas around the legs and arms, thereby increasing the possibility of LF transmission at an earlier time during the night than previously thought. We think it is important to take these factors into account when designing programs to fight LF and other vector-born NTDs.

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PROFILE

Dr. Dave D. Chadee is a Professor of Environmental Health in the Department of Life Sciences, UWI. His breakthrough research includes the development of the Xenomonitoring/PCR approach to Lymphatic filariasis, a new assay method for detecting mosquito preferences, the pupal index for dengue epidemiology and control, detected and eradicated two malaria outbreaks in Trinidad and the paper published in Science entitled, Genetics: a breakthrough for global public health.

Prof. Chadee has published over 200 papers and book chapters and has numerous collaborations in the USA and the UK. Prof. Chadee is a graduate of Naparima College, Trinidad, Dalhousie University (BSc Hons.), The University of the West Indies (MPhil) and the University of Dundee (PhD, M.PH, DSc).

Agustin Caceres is a Communications and Outreach Officer in the Social Protection and Health Division of the Inter-American Development Bank (IDB) in Washington DC.

Vaccine fever

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By: Charles Ebikeme

Last month, the results of the largest malaria study of its kind was published in the New England Journal of Medicine, spelling out the possibility of new hope for fighting a disease that accounts for 800,000 lives lost on a yearly basis – most of them children under the age of 5. This sparked a promise of hope in controlling a disease that causes so much human death and suffering. But it is by no means the last word. As we all take a step back from the ground-breaking news of the most advanced new malaria vaccine in the field so far – the pros and cons, drawbacks and potential of the RTS,S vaccine is being debated. Those of us interested in NTDs are drawn to the next logical question: how far along are we in vaccine development for NTDs?

With NTDs a heady mix of infections caused by bacterial and parasitic agents, vaccine development for many of the NTDs will have to overcome much of the same problems of the malaria vaccine – both technically and clinically.

The benefit of a vaccine is clear for all to see, and may be complemented with drug administrations as part of a total strategy to eliminate or eradicate many of these diseases. But despite the lack of research and development that plagues the NTDs, there is some progress at hand – or, at least, there is a realization and drive for developing more ‘antipoverty’ vaccines.

Of all the NTDs on the list, only rabies is vaccine-preventable with Buruli ulcer coming in a far second (the current Bacille Calmette-Guérin (BCG) vaccine appears to offer some short-term protection). A vaccine for hookworm, the almost vampiric parasite that ingests enough blood to cause anaemia, is in development. Schistosomiasis, arguably the most important human helminth infection in terms of mortality, has one antigen vaccine in clinical trials and a number in preclinical studies. The situation is promising – many have suggested that schistosomiasis could be the next disease to be ‘consigned to history’ by the next time the MDGs have to be rewritten. We wait in hope. Continue reading →

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“Human Time Bomb for Mosquitoes”

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Echoing several articles published last week, Donald McNeil Jr. of the New York Times also shed light on the recent study conducted in the American Journal of Tropical Medicine and Hygiene by scientists from Senegal and Colorado State University.

As mentioned previously, the study demonstrated that ivermectin, a drug used to treat onchocerciasis, can also kill mosquitoes.

Scientists such as Dr. Peter Hotez, President of the Sabin Vaccine Institute, are enthusiastic about this study’s effects on combating malaria and other mosquito borne illnesses, however, the article also provided some cautious perspectives from others. For the drug to effectively kill mosquitoes, nearly everyone in an infested area would need to take the pill simultaneously. In addition, the mosquito killing effects fade after a month so ivermectin, which is typically only distributed once or twice a year to a community, would need to be distributed more frequently.

The article goes on to say, “Also, when people with lots of worms are treated, they suffer fever and intense itching as the worms die. Though that might be bearable once a year, it discourages people from seeking treatment more frequently. And ivermectin is dangerous for a few people — those infested with large numbers of a relatively rare West African worm, the loa loa. These worms circulate in the blood and lungs and may jam capillaries when they die, potentially causing coma or death. Detecting them means drawing blood and viewing it under a microscope.”

Read the full article here

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