Gabriel laporta: Biodiversity can help prevent malaria outbreaks in tropical forests

Outline Background Results and Discussion Conclusion Final Remarks

Biodiversity Can Help Prevent MalariaOutbreaks in Tropical Forests

Gabriel Laporta1, Paulo Prado2, Roberto Kraenkel3, RenatoCoutinho3, Anice Sallum1

1Department of Epidemiology, FSP-USP2Department of Ecology, IB-USP

3Institute of Theoretical Physics, UNESP

October 25, 2013

Laporta et al., 2013 Funding: Fundação de Amparo à Pesquisa no Estado de São Paulo (FAPESP)

Biodiversity Can Help Prevent Malaria Outbreaks in Tropical Forests


Biodiversity Can Help Prevent Malaria Outbreaks inTropical ForestsGabriel Zorello Laporta1*, Paulo Inacio Knegt Lopez de Prado2, Roberto Andre Kraenkel3, Renato

Mendes Coutinho3, Maria Anice Mureb Sallum1

1 Departamento de Epidemiologia, Faculdade de Saude Publica, Universidade de Sao Paulo, Sao Paulo, Sao Paulo, Brazil, 2 Departamento de Ecologia, Instituto de

Biociencias, Universidade de Sao Paulo, Sao Paulo, Sao Paulo, Brazil, 3 Instituto de Fısica Teorica, Universidade Estadual Paulista Julio de Mesquita Filho, Sao Paulo, Sao

Paulo, Brazil

Abstract

Background: Plasmodium vivax is a widely distributed, neglected parasite that can cause malaria and death in tropical areas.It is associated with an estimated 80–300 million cases of malaria worldwide. Brazilian tropical rain forests encompass host-and vector-rich communities, in which two hypothetical mechanisms could play a role in the dynamics of malariatransmission. The first mechanism is the dilution effect caused by presence of wild warm-blooded animals, which can act asdead-end hosts to Plasmodium parasites. The second is diffuse mosquito vector competition, in which vector and non-vector mosquito species compete for blood feeding upon a defensive host. Considering that the World Health OrganizationMalaria Eradication Research Agenda calls for novel strategies to eliminate malaria transmission locally, we usedmathematical modeling to assess those two mechanisms in a pristine tropical rain forest, where the primary vector ispresent but malaria is absent.

Methodology/Principal Findings: The Ross–Macdonald model and a biodiversity-oriented model were parameterized usingnewly collected data and data from the literature. The basic reproduction number (R0) estimated employing Ross–Macdonald model indicated that malaria cases occur in the study location. However, no malaria cases have been reportedsince 1980. In contrast, the biodiversity-oriented model corroborated the absence of malaria transmission. In addition, thediffuse competition mechanism was negatively correlated with the risk of malaria transmission, which suggests a protectiveeffect provided by the forest ecosystem. There is a non-linear, unimodal correlation between the mechanism of dead-endtransmission of parasites and the risk of malaria transmission, suggesting a protective effect only under certaincircumstances (e.g., a high abundance of wild warm-blooded animals).

Conclusions/Significance: To achieve biological conservation and to eliminate Plasmodium parasites in human populations,the World Health Organization Malaria Eradication Research Agenda should take biodiversity issues into consideration.

Citation: Laporta GZ, Prado PIKLd, Kraenkel RA, Coutinho RM, Sallum MAM (2013) Biodiversity Can Help Prevent Malaria Outbreaks in Tropical Forests. PLoS NeglTrop Dis 7(3): e2139. doi:10.1371/journal.pntd.0002139

Editor: Edwin Michael, University of Notre Dame, United States of America

Received May 4, 2012; Accepted February 12, 2013; Published March 21, 2013

Copyright: � 2013 Laporta et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permitsunrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: MAMS received financial support from Fundacao de Amparo a Pesquisa no Estado de Sao Paulo (process n. 05/53973-0). GZL is a recipient of a FAPESPpostdoctoral fellowship n. 2012/09939-5. RMC is a recipient of a FAPESP doctorate fellowship n. 2010/09464-1. The funders had no role in study design, datacollection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

* E-mail: [email protected]

Introduction

The dynamics of malaria transmission involve a tritrophic

interaction among vector mosquitoes (Anopheles species), protozoan

parasites (Plasmodium species), and vertebrate hosts. Malaria is

endemic in tropical and subtropical regions [1–3]. The Global

Malaria Eradication Program adopted in the 1950s has failed to

meet expectations for malaria control in tropical and subtropical

countries. One of the causes of that failure was the lack of an in-

depth knowledge of the ecology of malaria-parasite transmission

[4]. In addition, Plasmodium vivax malaria has been neglected as a

chronic disease [5].

The prevalence of malaria remains high, especially in Africa,

the Americas, Asia, and the western Pacific. In those regions

collectively, the prevalence was 2% in 2011, most cases occurring

in children [6]. Recently, Murray et al. suggested that, although

malaria mortality rates have remained stable worldwide, the

World Health Organization underestimated malaria mortality for

the last two decades, purporting that the number of deaths from

malaria among adults in Africa, as well as among adults and

children outside of Africa, was substantially higher than that

reported [7]. Because of the suffering caused for malaria to

humans mainly in developing countries, elimination of this disease

is a challenge for the Malaria Eradication Research Agenda [8].

According to the World Health Organization agenda for vector

control, there is an urgent need to identify key knowledge gaps in

vector ecology and biology [9]. Such knowledge will be important

to define strategies for mosquito control, as well as to reduce the

PLOS Neglected Tropical Diseases | www.plosntds.org 1 March 2013 | Volume 7 | Issue 3 | e2139




Outline

1 Background

2 Results and Discussion

3 Conclusion

4 Final Remarks




Background

Epidemiological Background:Plasmodium vivax is a widely distributed and neglectedparasite.

It is associated with an estimated 80–300 million cases ofmalaria worldwide.




Background

Epidemiological Background:Plasmodium vivax is a widely distributed and neglectedparasite.It is associated with an estimated 80–300 million cases ofmalaria worldwide.




Background

Ecological Background:Tropical rain forests encompass host- and vector-richcommunities, in which two hypothetical mechanisms play arole in the dynamics of malaria transmission.

The first mechanism is the dilution effect caused bypresence of wild warm-blooded animals, which can act asdead-end hosts to Plasmodium parasites.The second is diffuse mosquito vector competition, in whichvector and non-vector mosquito species compete for bloodfeeding upon a defensive host.




Background


The first mechanism is the dilution effect caused bypresence of wild warm-blooded animals, which can act asdead-end hosts to Plasmodium parasites.

The second is diffuse mosquito vector competition, in whichvector and non-vector mosquito species compete for bloodfeeding upon a defensive host.




Background


The first mechanism is the dilution effect caused bypresence of wild warm-blooded animals, which can act asdead-end hosts to Plasmodium parasites.The second is diffuse mosquito vector competition, in whichvector and non-vector mosquito species compete for bloodfeeding upon a defensive host.




Main goal

We used mathematical modeling to assess those twomechanisms in a pristine tropical rain forest, where theprimary vector is present but malaria is absent.




The Study System




Outline

1 Background


3 Conclusion

4 Final Remarks




What have we done?

The Ross–Macdonald model and a biodiversity-orientedmodel were parameterized using newly collected data anddata from the literature.




Ross-Macdonald model: null weak interactions

dXh

dt= −bThmXhYm

N+ γYh (1)

dYh

dt=

bThmXhYm

N− γYh (2)

dXm

dt= µYm − bTmhXmYh

N(3)

dYm

dt=

bTmhXmYh

N− µYm (4)




Biodiversity-oriented model: ecological interactions

dXh

dt= − bThmXhYm

(B + N)(

1 + 1h

C+MB+N

) + γYh (5)

dYh

dt=

bThmXhYm

(B + N)(

1 + 1h

C+MB+N

) − γYh (6)

dXm

dt=

αbM1 + 1

hC+MB+N

− µXm − bTmhXmYh

(B + N)(

1 + 1h

C+MB+N

) (7)

dYm

dt=

bTmhXmYh

(B + N)(

1 + 1h

C+MB+N

) − µYm , (8)




Main results

The basic reproduction number (R0; 2.18) estimatedemploying Ross–Macdonald model indicated that malariacases occur in the study location.

However, no malaria cases have been reported since1980.In contrast, the biodiversity-oriented model corroboratedthe absence of malaria transmission (R0; 0.93).




Main results

The basic reproduction number (R0; 2.18) estimatedemploying Ross–Macdonald model indicated that malariacases occur in the study location.However, no malaria cases have been reported since1980.

In contrast, the biodiversity-oriented model corroboratedthe absence of malaria transmission (R0; 0.93).




Main results

The basic reproduction number (R0; 2.18) estimatedemploying Ross–Macdonald model indicated that malariacases occur in the study location.However, no malaria cases have been reported since1980.In contrast, the biodiversity-oriented model corroboratedthe absence of malaria transmission (R0; 0.93).




Dilution effect and diffuse competitionSomatory of weak interactions can modulate the dynamics of malarial transmission




The diffuse competition mechanism was negativelycorrelated with the risk of malaria transmission

0 200 400 600 800Human population size (N)

0

2000

4000

6000

8000

Abundance

of

non-v

ect

ors

(C

)

0.39

0.00

0.15

0.30

0.45

0.60

0.75

0.90

1.05

1.20

1.35

1.50

R0




There is a non-linear, unimodal correlation betweenthe mechanism of dead-end transmission of parasitesand the risk of malaria transmission

0 200 400 600 800Human population size (N)

0

200

400

600

800

Abundance

of

non-h

ost

s (B

)

0.39

0.00

0.15

0.30

0.45

0.60

0.75

0.90

1.05

1.20

1.35

R0




Outline

1 Background


3 Conclusion

4 Final Remarks




To achieve biological conservation and to eliminatePlasmodium parasites in human populations, all malariaeradication programs should take biodiversity issues intoconsideration.




Outline

1 Background


3 Conclusion

4 Final Remarks




Big Data toolbox and approach can be also useful forhypothesis-driven scientific researches.

Big Data philosophy can create a new category of studydesign in Epidemiology.




Big Data toolbox and approach can be also useful forhypothesis-driven scientific researches.Big Data philosophy can create a new category of studydesign in Epidemiology.



Gabriel laporta: Biodiversity can help prevent malaria outbreaks in tropical forests

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