Archive for the 'Vector control' Category

All aboard the Malaria Express

Innovative vector control as reported in The Hindu (thanks Anup Anvikar) using a locomotive to spray larvicide along train tracks through the city of Delhi. As we see malaria transmission decline from improved control efforts, the remaining foci will increasingly be limited to specific ecotypes. Examples include urban and forest malaria, which have proved refractory, and we will need strategies specific to their peculiarities.

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Genetically modified mosquitoes released in Malaysia

6,000 Aedes mosquitoes (the species that transmits dengue) were released in an uninhabited site in the center of the country. The purpose of the field trial is to study the dispersal and life span of these modified mosquitoes under natural conditions. The idea is simple:  replace natural mosquitoes with insects engineered to be either resistant to a microbe or ones with defective offspring in later generations as in this case. Still, in order to replace existing populations, new mosquitoes must out-compete their natural relatives. Not surprisingly, many civil society groups are concerned about potential harms if a new super mosquito that is able to transmit diseases emerges. I’m just skeptical that a single new variant could dominate products of long-term evolution especially across multiple ecological niches. Similar research is underway with malaria transmitting Anopheles mosquitoes – is it as far along?

President's Malaria Initiative and Angola Part 2

Below is a comment, on the PMI clarification, from one of the authors of the WHO Bulletin article.

In regard to the Director’s response to criticisms about the PMI program in Angola, I would like to make a few comments, having written the article in English, with the approval of my two colleagues, especially Martinho Somandjinga, the first author and an experienced and highly competent malaria control official.

The primary fault in the whole story was the use of administrative reports on malaria, based on clinical diagnoses of malaria, which in fact were simply diagnoses of fever and headache.  No blood slides were taken to confirm these administrative reports.  Therein lies the problem.

The secondary problem we pointed out is that WHO, in their global planning and analysis, uses the same faulty administrative reports of fevers, instead of making lab diagnoses for the malaria parasite.

Thirdly, although Mr. Somandjinga and I worked out and recommended to PMI a monitoring plan complete with labs, blood slide collections, and microscopic diagnoses, PMI has continued to ignore the need for this more precise process for monitoring and evaluating their effort in Angola and in the rest of Africa.

The First Law for attacking malaria in Africa is that it is like building a huge cathedral or mosque, it will take generations.  So evaluation and monitoring is essential if we are to make progress over the next several decades.  You cannot control malaria in Africa with public relations, it is a tough disease.

A really good sign however, is the increased role of epidemiologists from CDC in PMI and in Geneva.  These folks know the score.  Some have run studies showing that the false positivity rate of these clinical diagnoses is erratic and can be very high, like 50%!  And a recent study in Khartoum showed a false positive rate of 90%.  So the administrative data is useless, and I trust Robert Newman and Larry Slutsker will work towards establishment of microscopic diagnoses on appropriate sentinel populations.  Then we will know what the problem really is, and where to put our efforts.

It will take a while, but we can do it.  And now is a wonderful time to capture the popular enthusiasm for malaria control in Africa.

Bill Jobin
Cortez, Colorado

Did USAID, President's Malaria Initiative blunder malaria control in Angola?

The title of this post is a bit sensational for my tastes but honest in regards to the charges levied by Somandjinga et al in the Bulletin of the WHO. The history of malaria control is replete with stories of gaffes small and large. However, the “policy and practice” article contains frank and detailed criticism, which rarely ever appear in print, about USAID/PMI (previously introduced here) operations in Angola. Before summarizing the alleged mistakes, it should be stressed that all human efforts will be imperfect. Seems obvious but we often fail to recognize the difficulties faced in executing programs. This does not excuse lapses in critical thinking – rather it is to stress the importance of process. That the ability to acknowledge errors, learn from them, and iterate efforts may be more important than our propensity to commit mistakes.

Here are the USAID/PMI mistakes as stated, sometimes directly and at other times in between the lines, by the authors:

– Failure to gain demonstrated national commitment (in the form of increased malaria staff or local funds) prior to beginning the program

– Rush to implement the program

– Poor understanding and use of routine data

– Selection of a single control measure

– No pretreatment evaluation

– Disregard for objections from the authors (one of whom is the regional public health manager)

– False assurances regarding CDC support and data collection

– Communication barriers from a lack of language proficiency (Portuguese)

– All of which culminated in the spraying of the homes of 500,000 people in an area without adult mosquitoes or breeding sites, i.e. likely no to minimal malaria transmission

– Overall, inexperience of PMI-Angola leadership in malaria control

Does PMI accept these critiques? Have they learned from their mistakes? I emailed PMI asking if there was a public response to the article or if they wished to provide another perspective on this post. I was pleased to receive a kind and prompt reply which is posted below in its entirety. Readers can draw their own conclusions.

PMI Clarification:

Dear Mr. Naman Shah,

Thank you for your query sent to “Ask the Malaria Coordinator” regarding the recent World Health Organization Bulletin article authored by Somandjinga et al., which critiques some aspects of the President’s Malaria Initiative’s (PMI) work in Angola in 2005/2006.  The indoor residual spraying (IRS) program referred to in the article was the very first round of IRS supported by the PMI in any country.  Although important lessons were undoubtedly learned during implementation of this first spray round in Angola, the implementation of this campaign was considered a success with a 90% acceptance rate among householders in the communities targeted for spraying, more than 590,000 people residing in houses sprayed were protected from malaria, and with no outbreaks of malaria detected in these areas following the spraying campaign.

There are several statements found within the article that are factually incorrect.  It is inaccurate to state that PMI failed to secure national commitment prior to beginning the spray program.  Angola was selected as one of the first three PMI countries.  The process for country selection for the President’s Malaria Initiative has always included high level consultation between US Ambassadors and the host country leadership including Ministries of Health, and Angola was no exception.  The first annual operational plan for PMI support in Angola including support for the aforementioned IRS campaign, as with subsequent annual plans, was prepared in consultation and collaboration with the Angola National Malaria Control Program (NMCP).

Although the article points out that the target areas for the first spray round were areas later found to have low levels of malaria transmission, PMI selected the areas targeted for spraying with the support of the Ministry of Health of Angola and with direct guidance from the Angola National Malaria Control Program Director.  It is important to note that this first spray round was part of a multi-donor effort in the southern provinces of Angola, with PMI support complementing the IRS program supported by WHO in an adjacent province.   Furthermore, the spraying of these malaria-epidemic prone areas was consistent with current WHO guidance for selecting areas appropriate for IRS and the success of the first IRS campaign in Angola carried out in these low transmission areas provided the experience and confidence to enable successful targeting of IRS in higher transmission areas in future spray rounds.

Finally, PMI, working in direct collaboration with NMCPs in the 15 PMI countries and together with other donors and partners, has demonstrated significant progress in scaling-up malaria prevention and control interventions, with clear evidence of reductions in malaria burden in many of the PMI countries.  Specifically related to IRS, since 2005/2006 PMI has been leading efforts to incorporate IRS as a major component of malaria control programs in Africa.  PMI-supported IRS programs work in close collaboration with national and district government counterparts and have expanded emphasis on building local capacity to implement quality IRS activities, including placing significant attention to environmental issues and best practices surrounding the intervention.  Prior to the launch of PMI, IRS was only being implemented by NMCPs in a few southern African countries and in Ethiopia and Eritrea, in addition to limited private sector investments in a handful of African countries.  PMI has played a key role in re-introducing IRS as an effective malaria control tool in Africa.  Currently many African countries that are not among the 15 PMI countries, have begun or are planning implementation of IRS programs after having learned from the successful experience demonstrated by their neighboring NMCPs in collaboration with PMI.

It is important to note that two of the three authors of this article were former contract employees of the PMI IRS implementing partner.

Communicating research: a case from vector molecular biology

The mosquito vector, and by extension local ecology, drives malaria transmission. So understanding vector biology is important to malaria control. Classical studies of mosquito flight range, feeding preferences, and resting habits were crucial in the development and application of control strategies. Modern vector biology research, dominated by molecular studies, has produced new tools for monitoring insecticide resistance in mosquitoes as well as identifying Anopheles sibling species among whom the potential for transmitting malaria can broadly vary.

Recently, I browsed through a malaria journal article (open access!) whose potential I have difficulty understanding. Can someone explain to me how research on variation in chromosomal inversions and their relationship with stress responses will improve malaria control? Looking carefully through the manuscript, the sole rationale that I could find was:

Polymorphism for the 2La inversion creates heterogeneity in the stress response within A.gambiae, which could directly or indirectly reduce the efficacy of vector control measures, and influence the reaction of vector populations to environmental variation including climate change.

I find this single sentence advanced by the authors both incomplete and unsatisfying. It tells you very little. So let’s think through the rationale ourselves. Understanding the ability of a vector to exploit different habitats is certainly useful – we could predict how mosquito ranges and other characteristics may change with the climate. Understanding the molecular basis of that ability might further help – if the molecular changes had a clear association with a phenotype of interest (i.e. real world characteristics of the mosquito) and were such that they could easily be monitored. Understanding polymorphisms in those molecular mechanisms and their relationship to stress response variation however is not intuitively valuable (perhaps for modelling purposes?). To be clear, my aim is not cast the research as meaningless (though it may be). Sometimes the impact of basic science take years or decades to be realized. Rather, I’m surprised the authors, and especially the reviewers, did not seek to clearly convey the value of the work. If the purpose of public health research is to improve health, then the communication of such research should describe its relevance in explicit and detailed language.

The DDT debate and malaria control

Everyone likes to talk about DDT and malaria, and a friend of mine asked me to post about the topic. No way! I am not walking into that mess.

Suffice to say, I am frustrated with both sides of the debate. My personal views probably lie closest to those eloquently expressed here.

Filling puddles for malaria control

“Pool-filling could control malaria” an article at AllAfrica.com says.

True, but so could swatting enough mosquitoes with your hands. The existence of an intervention does not mean its viable. Media communication of science research or public health news (previously discussed here) is consistently poor. To be fair, the environmental control of malaria can be an appropriate tool.  Historically, Brazil, Italy, Panama and a few other countries have used it with good success. Why did it work there? First, reducing mosquito density will have little effect on transmission in highly endemic areas, but these countries had the right ecotype. Second, environmental control is labor intensive and requires strong management, both of which were provided through military-style campaigns.


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