Our guest columnist in this two-part series is world expert on dengue, Professor Dave D. Chadee from the Department of Life Sciences, University of the West Indies who questions the dengue control strategies used in T&T.
…In Tobago as early as 2003 a switch in major mosquito breeding sites from water drums to small containers was reported because of the replacement of water drums by tanks, especially in the Central district. Why, for example, did Trinidad not adopt the strategy of replacing water storage drums with closed tanks? A more dramatic effect may have been expected in Trinidad where drums account for 70 per cent of mosquito breeding sites while, prior to replacement, only 35 per cent in Tobago. The Ministry of Health figures show over 1800 reported dengue cases in July 2011 and the current dengue programmes are being run by three different ministries–Local Government is conducting a source reduction programme or clean-up campaign but unfortunately this will remove less than 5 per cent of the mosquito breeding sites. This strategy was advocated in the 1980s by the Pan American Health Organization and was evaluated in 4 different geographical areas but they all failed to reduce the vector populations to below disease transmission levels. The education programme being run by the Ministry of External Affairs and Communication is targeting householders and is excellent but will have long term benefits rather than short term relief to householders.
Long-lasting insecticidal nets have been one of the least expensive and most effective weapons in the fight against malaria. According to the new report, the number of bed nets delivered to malaria-endemic countries in sub-Saharan Africa increased from 88.5 million in 2009 to 145 million in 2010. An estimated 50% of households in sub-Saharan Africa now have at least one bed net, and 96% of persons with access to a net use it.
There has also been further progress in rolling out diagnostic testing, which is crucially important to separate malaria from other febrile illnesses. The number of rapid diagnostic tests delivered by manufacturers climbed from 45 million in 2008 to 88 million in 2010, and the testing rate in the public sector in the WHO African Region rose from 20% in 2005 to 45% in 2010.
Worldwide, the volume of antimalarial medication delivered to the public sector has also increased. In 2010, 181 million courses of artemisinin-based combination therapies (ACTs) were procured, up from 158 million in 2009, and just 11 million in 2005. ACTs are recommended as the first-line treatment for malaria caused by the most deadly malaria parasite, Plasmodium falciparum.
Malaria rebounded in the 1970s when mosquitoes became resistant to pesticides and the parasites that cause the disease became resistant to chloroquine. Eradication programs begun in the colonial era fell apart as newly independent countries sank into poverty.
The Global Fund is desperate for money. The $2 billion donors give annually is only about a third of what is needed, the report said.
Although 145 million mosquito nets were delivered to Africa in 2010, they tear easily and the insecticide embedded in them fades within three years.
Resistance to artemisinin, hailed as the new miracle cure, persists in southeast Asia and could spread; 28 small companies, defying the W.H.O., still sell pills containing only artemisinin, which encourages resistance. The agency endorses multidrug cocktails, but they cost more and the partner drugs often taste bitter.
For the study, Dimopoulos and his team genetically engineered Anopheles mosquitoes to produce higher than normal levels of an immune system protein Rel2 when they feed on blood. Rel2 acts against the malaria parasite in the mosquito by launching an immune attack involving a variety of anti-parasitic molecules. Through this approach, instead of introducing a new gene into the mosquito DNA, the researchers used one of the insect’s own genes to strengthen its parasite-fighting capabilities. According to the researchers, this type of genetically modified mosquito could be further developed and used to convert malaria-transmitting to Plasmodium-resistant mosquito populations. One possible obstacle for this approach is the fitness of the genetically modified malaria resistant mosquitoes, since they would have to compete with the natural malaria-transmitting mosquitoes. The researchers showed with their study that the Rel2 genetically modified mosquito strain lived as long, and laid as many eggs, as the non-modified wild type mosquitoes, thereby suggesting that their fitness had not become significantly impaired.
Estimates of malaria incidence derived from routine surveillance data suggest that 225 million episodes of malaria occurred worldwide in 2009. This estimate is lower than other published figures, such as those from the Malaria Atlas Project (MAP), particularly for estimates of malaria incidence outside Africa. Richard Cibulskis and colleagues at the WHO in Geneva, Switzerland present a critique of different estimation methods of the worldwide incidence of malaria in this week’s PLoS Medicine.
“Vaccines against malaria are notoriously difficult to develop,” said Adrian Hill of Britain’s Oxford University, who worked on the vaccine research team.
This vaccine builds on work published last month by the same team, who pinpointed a single receptor for a protein called RH5 that is critical for the malaria parasite to gain entry into red blood cells where it multiplies and spreads.
The researchers said in November they thought that by blocking this process, they could halt the disease in its tracks – and Tuesday’s results confirm their thinking.
“What’s exciting about RH5 is that we’ve shown that antibodies against this protein have so far knocked down every parasite we’ve been able to test in the laboratory,” Simon Draper of Oxford’s Jenner Institute, who also worked on the study, said in a telephone interview.
Cost-effectiveness of malaria microscopy and rapid diagnostic tests versus presumptive diagnosis: implications for malaria control in UgandaPosted: December 19, 2011
Conclusion: RDT was cost effective in both low and high transmission settings. With a global campaign to reduce the costs of AL and RDT, the Malaria Control Programme and stakeholders need a strategy for malaria diagnosis because as the cost of AL decreases, presumptive treatment is likely to become more attractive.