Malaria Journal - Latest Comments

GMP artesunate

Arjen M Dondorp — 2012-05-11T16:17:23Z

I enjoyed reading this interesting study. I just wanted to comment on the statement made by the authors regarding the Guilin artesunate product that WHO prequalification "is not the same as GMP certification". It is a prerequisite that all WHO prequalified products are manufactured to GMP and verified as such by inspectors from WHO or a stringent authority.

Re Analysis for genotyping Duffy blood group in inhabitants of Sudan, the Fourth Cataract of the Nile

Ishag Adam — 2012-05-11T16:16:19Z

I read this article with great interest and I have to congratulate the authors.
However, It is not obvious is the methods how they approached the patients and how the patients were consented. It is var difficult to convey such study in Sudan with Polish scientists without one of the local researchers. Importantly in the ethics section authors mentioned that they received ethical clearance from Poland, we do respect this but is it valid to have an ethical clearance from Poland and fostered the study in Sudan?
I hope authors would to be able to clarify these points
Best Regards

Update on CF11 availability

Christopher Plowe — 2012-05-11T16:14:35Z

Unfortunately, as this paper went to press the manufacturer of CF11 put column production on hold, and subsequently suspended making them indefinitely. While they may resume in the future, we are investigating and evaluating alternative inexpensive means of leukocyte depletion. For updates, please visit the Molecular Module page on the website of the WorldWide Antimalarial Resistance Network www.wwarn.org.

the title

NAGUMO WALTER-RODNEY — 2012-05-11T16:11:51Z

i think the title should have stated what phase of the trial is the study

Additional IRS costing data

Michael White — 2012-05-11T16:06:09Z

Readers wishing to obtain more up to date data on the costs of indoor residual spray programmes may want to check out the following excellent report from the President's Malaria Initiative:

An economic analysis of the costs of indoor residual spraying in 12 PMI countries, 2008¿2010

Prepared by
Jeffrey Sine, Rajeev Colaco, and Hannah Frawley

http://www.pmi.gov/technical/irs/IRS_economic_analysis.pdf

Michael White

Erratum

John Frean — 2012-05-11T11:00:44Z

Table 1 legend should read:
Data shown are number of parasites and white blood cells (WC) counted per slide, as well as the white blood cell count (WCC, as leukocytes per µl) used to calculate the parasite density for each slide by manual, digital, and conventional methods.

Survival rate formula assumes stable age structure

Olivier Johan Tavai Briet — 2011-10-18T08:59:03Z

The authors use Davidson's formula (1954) to estimate the survival rate, which assumes that the mosquito population age structure is stable over the period of data collection. Since the data were collected for 10 nights in (only) one month, it is difficult to establish whether the population was approximately stable. If, for instance, the population was growing during the month surveyed, this would lead to underestimation of the survival rate. Even though there is little seasonality of rainfall in the area, the reported low survival rates should be interpreted with caution if there is no evidence that the population was stable.

Reference
Davidson, G. (1954) Estimation of the survival-rate of anopheline mosquitoes in nature. Nature, UK, 174, 792-793.

Correction of typo in additional file

Lisa White — 2011-10-18T08:58:04Z

The equation lambda=R_0*((1/L)+(1/d_treat))*(I_1+I_2)/N should be lambda=R_0*((1/L)+(1/d_in))*(I_1+I_2)/N.

Possible effects of MDA

Dan Wolf Meyrowitsch — 2011-10-18T08:57:00Z

Dear Dr. Walker,

Thank you for the comment to our recent paper, and for the interesting suggestion that ongoing Mass Drug Administration (MDA) with ivermectin applied in the study area for control of lymphatic filariasis might be the course of the observed downward trend in the Anopheles populations.

We acknowledge that ivermectin treatment may have contributed to the observed decline, but find it highly unlikely that a single annual MDA can be the only/major course of this dramatic reduction. First, the vectors were not exposed constantly to ivermectin, as indicated in your comment, but only during a few days each year. Second, the treatment coverage during each MDA was generally well below 80% of the eligible population (i.e. below 60% of the total population). Third, major declines were also observed in the years before the start of MDAs (late 2004). We do find the studies of Kobylinski et al. (2011) on the effect of ivermectin treatment on malaria transmission very interesting, but as also indicated in the paper of Foy et al. (in press) such treatment most likely needs to be given with short intervals to exert a significant effect on the Anopheles population (by the way, both of these papers became available after our paper was submitted to Malaria Journal). However, it is definitely an important issue that needs to be looked further into, and we are currently breaking down our time series of observations in order to analyse for a possible relationship between the timing of MDAs and the decline in Anopheles population.

Finally we would like to emphasize that if MDAs with ivermectin contributed to the decline in Anopheles population there is reason to be worried for the consequences after stop of the lymphatic filariasis or onchocerciasis MDA campaigns. Will the Anopheles vectors return, and will this result in dramatic malaria epidemics with many fatalities?

Best wishes,

Paul Erik Simonsen and Dan Meyrowitsch

A possible explanation for the decline: ivermectin from MDAs for LF

Edward Walker — 2011-08-29T15:12:53Z

This interesting paper reveals a long term, downward trend in relative densities of Anopheles gambiae s.l. and Anopheles funestus in a region of northeastern Tanzania where vector control measures specifically focusing on malaria control have not previously been implemented intensively. The authors conclude that the decline is therefore not due to any specific chemical intervention against the malaria vector populations and must have some other cause.

Ironically, this same research team is studying control of lymphatic filariasis at the same study sites, and have elsewhere documented significant declines in prevalence of microfilaremia, due to Wuchereria bancrofti infection, through well done longitudinal studies. Importantly, that process has been effected by mass distribution of a combination of two drugs: ivermectin and albendazole. Recently, several studies have shown that ivermectin has lethal and sublethal effects, mediated through the blood meal and in the ppb concentration, on Anopheles vectors of malaria in Africa; and also reduces vector survival and therefore vectorial capacity (see references below). It is indeed surprising that the authors here did not attribute the vector population decline to the effects of constant exposure to ivermectin in human blood meals, a decidedly strong chemical intervention whose effects would be predicted to achieve long term population declines such as were observed. That the Culex quinquefasciatus population under study did not decline in the same manner is likely because females of this species have considerably greater host breadth than either Anopheles funestus or Anopheles gambiae and so would have less overall exposure to ivermectin.

References
Fritz ML, Siegert PY, Walker ED, Bayoh MN, Vulule JR, Miller JR. Toxicity of bloodmeals from ivermectin-treated cattle to Anopheles gambiae s.l. Annals Trop Med Parasitol 2009; 103: 539-547.
Kobylinski KC, Sylla M, Chapman PL, Sarr MD, Foy BD. Ivermectin mass drug administration to humans disrupts malaria parasite ransmission in Senegalese villages. American Journal of Tropical Medicine and Hygiene 2011; 85: 3-5.
Foy BD, Kobylinski KC, Marques de Silva I, Rasgon JL, Sylla M. Endectocides for malaria control. Trends in Parasitology 2011; (article in press).