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CSU 78/2010: OFF THE BEATEN PATH, TWICE -- USE OF ATTRACTIVE TOXIC SUGAR BAIT METHODS AGAINST A. GAMBIAE

Monday, 23rd of August 2010 Print
CSU 78/2010:  OFF THE BEATEN PATH, TWICE
Occasionally one sees articles in the literature which, except to the specialist, are surprising finds. Here are two.

Note to readers: do you enjoy reading items like these, or should I stick to things which will make their way into The Economist and the New York Times?
BD

1)
  USE OF ATTRACTIVE TOXIC SUGAR BAIT METHODS AGAINST 
 A. GAMBIAE  IN MALI

From the Malaria Journal, a new wrinkle in malaria vector control from Mali. Those with concerns about insecticide resistance and/or environmental impacts of conventional insecticides may find this method interesting.Full text is at http://www.malariajournal.com/content/pdf/1475-2875-9-210.pdf

Muller GC, Beier JC, Traore SF, Toure MB, Traore MB, Bah S, Doumbia S, Schlein Y

Reference:  Malaria Journal 2010, 9:210 (21 July 2010)

Contact email: guntercmuller@hotmail.com

Background


Based on highly successful demonstrations in Israel that attractive toxic sugar bait (ATSB) methods can decimate local populations of mosquitoes, this study determined the effectiveness of ATSB methods for malaria vector control in the semi-arid Bandiagara District of Mali, West Africa.
 
Methods

Control and treatment sites, selected along a road that connects villages, contained man-made ponds that were the primary larval habitats of Anopheles gambiae and Anopheles arabiensis. Guava and honey melons, two local fruits shown to be attractive to An. gambiae s.l., were used to prepare solutions of Attractive Sugar Bait (ASB) and ATSB that additionally contained boric acid as an oral insecticide. Both included a color dye marker to facilitate determination of mosquitoes feeding on the solutions. The trial was conducted over a 38-day period, using CDC light traps to monitor mosquito populations. On day 8, ASB solution in the control site and ATSB solution in the treatment site were sprayed using a hand-pump on patches of vegetation. Samples of female mosquitoes were age-graded to determine the impact of ATSB treatment on vector longevity.
 
Results

Immediately after spraying ATSB in the treatment site, the relative abundance of female and male An. gambiae s.l. declined about 90% from pre-treatment levels and remained low. In the treatment site, most females remaining after ATSB treatment had not completed a single gonotrophic cycle, and only 6% had completed three or more gonotrophic cycles compared with 37% pre-treatment. In the control site sprayed with ASB (without toxin), the proportion of females completing three or more gonotrophic cycles increased from 28.5% pre-treatment to 47.5% post-treatment. In the control site, detection of dye marker in over half of the females and males provided direct evidence that the mosquitoes were feeding on the sprayed solutions.
 
Conclusion

This study in Mali shows that even a single application of ATSB can substantially decrease malaria vector population densities and longevity. It is likely that ATSB methods can be used as a new powerful tool for the control of malaria vectors, particularly since this approach is highly effective for mosquito control, technologically simple, inexpensive, and environmentally safe.

2) PLAGUE OUTBREAKS IN PRAIRIE DOG POPULATIONS

The study of how pathogens survive under challenging conditions is of interest both to students of human and veterinary health. This is especially so for plague, now rare in human populations.

This open source contribution is from the Proceedings of the National Academy of Sciences. Full text is at  http://www.pnas.org/content/107/32/14247.full.pdf+html

 

Abstract:

Plague outbreaks in prairie dog populations explained by percolation thresholds of alternate host abundance

1.   Daniel J. Salkelda,1,2,

2.   Marcel Salathéb,2,3,

3.   Paul Stappc, and

4.   James Holland Jonesa

+ Author Affiliations

1.    aWoods Institute for the Environment and Department of Anthropology, Stanford University, Stanford, CA 94305;

2.    bDepartment of Biology, Stanford University, Stanford, CA 94305; and

3.    cDepartment of Biological Science, California State University, Fullerton, CA 92834

·         3Present address: Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, PA 16802.

1.     Edited by Simon A. Levin, Princeton University, Princeton, NJ, and approved June 15, 2010 (received for review March 5, 2010)

2.     2D.J.S. and M.S. contributed equally to this work.

Abstract

Highly lethal pathogens (e.g., hantaviruses, hendra virus, anthrax, or plague) pose unique public-health problems, because they seem to periodically flare into outbreaks before disappearing into long quiescent phases. A key element to their possible control and eradication is being able to understand where they persist in the latent phase and how to identify the conditions that result in sporadic epidemics or epizootics. In American grasslands, plague, caused by Yersinia pestis, exemplifies this quiescent–outbreak pattern, because it sporadically erupts in epizootics that decimate prairie dog (Cynomys ludovicianus) colonies, yet the causes of outbreaks and mechanisms for interepizootic persistence of this disease are poorly understood. Using field data on prairie community ecology, flea behavior, and plague-transmission biology, we find that plague can persist in prairie-dog colonies for prolonged periods, because host movement is highly spatially constrained. The abundance of an alternate host for disease vectors, the grasshopper mouse (Onychomys leucogaster), drives plague outbreaks by increasing the connectivity of the prairie dog hosts and therefore, permitting percolation of the disease throughout the primary host population. These results offer an alternative perspective on plague's ecology (i.e., disease transmission exacerbated by alternative hosts) and may have ramifications for plague dynamics in Asia and Africa, where a single main host has traditionally been considered to drive Yersinia ecology. Furthermore, abundance thresholds of alternate hosts may be a key phenomenon determining outbreaks of disease in many multihost-disease systems.

Footnotes

·         1To whom correspondence should be addressed. E-mail: dsalkeld@stanford.edu.

·         Author contributions: D.J.S., M.S., and P.S. designed research; D.J.S., M.S., P.S., and J.H.J. performed research; D.J.S., M.S., and J.H.J. contributed new reagents/analytic tools; D.J.S., M.S., P.S., and J.H.J. analyzed data; and D.J.S. and M.S. wrote the paper.

·         The authors declare no conflict of interest.

·         This article is a PNAS Direct Submission.

·        This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1002826107/-/DCSupplemental.

Freely available online through the PNAS open access option.



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