Dissertation

DISSERTATION IVERMECTIN MASS DRUG ADMINISTRATION TO HUMANS FOR MALARIA PARASITE TRANSMISSION CONTROL Submitted by Kevin Kobylinski Department of Microbiology, Immunology and Pathology In partial fulfillment of the requirements For the Degree of Doctor of Philosophy Colorado State University Fort Collins, Colorado Summer 2011 Doctoral Committee: Advisor: Brian D. Foy Lars Eisen Kathryn P. Huyvaert Ronald Rosenberg Copyright by Kevin Conrad Kobylinski 2011 All Rights Reserved ABSTRACT IVERMECTIN MASS DRUG ADMINISTRATION TO HUMANS FOR MALARIA PARASITE TRANSMISSION CONTROL Every year, an estimated 500 million people are afflicted with malaria worldwide, killing more than one million people, most of whom are children in sub- Saharan Africa. The current malaria eradication program requires novel vector control methods to reduce the transmission of Plasmodium, the causative agent of malaria. These new methods must: target exophagic and exophilic Plasmodium vectors, integrate with current vector control efforts, be evaluated in the field in combination with other interventions, evade potential behavioral mechanisms that mosquitoes may evolve to avoid the intervention, new agents should have different modes of action, reduce the risk of physiological resistance development, and affect vector population age structure. This dissertation addresses how ivermectin mass drug administration, meets and exceeds all of these issues. Laboratory-based experiments demonstrated that ivermectin at human relevant pharmacokinetics affects Anopheles gambiae s.s. survivorship and that cumulative ivermectin blood meals compound mortality, blood feeding frequency, knockdown, and recovery. Field-based experiments demonstrate that ivermectin mass drug administration to humans reduces the survivorship of wild-caught Anopheles gambiae s.s. and probably Anopheles arabiensis up to six days post-administration. Most ii importantly, ivermectin mass drug administration to humans was shown to reduce the proportion of field-caught Plasmodium falciparum-infectious Anopheles gambiae s.s. for at least 12 days post-treatment. Ivermectin mass drug administration could be a powerful addition to malaria eradication campaign efforts. iii ACKNOWLEDGEMENTS I thank Dr. Massamba Sylla for his support and prodigious efforts to make the field work in Senegal possible. I thank Dr. Massamba Sylla‟s family and friends for their gracious hospitality and kindness. I thank Dr. Moussa Dieng Sarr and the Senegalese Ministry of Health for their assistance and willingness to let us work in their country. I thank Dr. Doudou Sene, Mactar Mansaly, Rigobert Keita, and Filly Keita for performing the mass drug administrations. I thank Cheikhtidiane Diagne for his assistance in the field. I thank Dr. Phillip Chapman and Tan Hongyu for their statistical consulting services. I thank Drs. Lars Eisen, Kate Huyvaert, and Ron Rosenberg for their critical comments and suggestions. I thank Dr. William Black IV for his assistance with developing the mermithid Maximum Parsimony tree. I thank Ines Marques da Silva, Anna Winters, and Saul Lazano-Fuentes for their assistance with GIS issues. I thank Matt Butters, Meg Gray and Ines Marques da Silva for their laboratory support. I thank Dr. Alvaro Molina-Cruz and the MR-4 repository for providing Plasmodium positive control samples. I especially thank the kind people of Ndebou, Boundoucondi, Damboucoye, Nathia, and Ibel for allowing us to work in their villages and their overreaching generosity and enthusiasm for this project. iv TABLE OF CONTENTS Abstract …………………………………….……………………………………………. ii Acknowledgements ………………..……………………………………………………. iv Table of contents ………………………………………………………….…………...… v List of abbreviations …………………………………………………….…………….... vi Chapter 1 – Literature review ………………………………………...…………………. 1 Chapter 2 – The effect of anthelmintics used for mass drug administration on Anopheles gambiae s.s. survivorship ……………………………………………………..... 45 Chapter 3 – Sublethal effects of ivermectin on Anopheles gambiae s.s. ………………. 63 Chapter 4 – Bionomics of Plasmodium vectors in southeastern Senegal ……………… 90 Chapter 5 – Survivorship of field-caught Anopheles from ivermectin MDA-treated villages in southeastern Senegal …………………………………………….... 123 Chapter 6 – Ivermectin mass drug administration to humans disrupts Plasmodium transmission in Senegalese villages ……………………………………...…… 143 Chapter 7 – Mermithid nematodes in adult Anopheles from southeastern Senegal ….. 150 Chapter 8 – Conclusions and remarks ………………………………………………... 160 References …………………………………………………………………………….. 176 v LIST OF ABREVIATIONS ACT – Artemisinin-based combination therapy AE – adverse event AIC – Akaike‟s Information Criterion ALB – albendazole APOC – African program for onchocerciasis control BMGF – the Bill and Melinda Gates Foundation CDC – center for disease control CDD – community-directed drug distributor CGoVC – Consultative Group on Vector Control Cl - chloride CMFL – community-directed treatment with ivermectin CNS – central nervous system DDT – dichloro-diphenyl-trichloroethane DEC – diethylcarbamazine DMSO – dimethylsulfoxide EIR – entomological inoculation rate GABA – gamma aminobutyric acid GluCL – glutamate gated chloride GMAP – global malaria action plan GMEP – global malaria eradication program GPELF – global program to eliminate lymphatic filariasis vi HBI – human blood index HBM – health belief model HLC – human landing catch IRS – indoor residual spraying ITN – insecticide-treated net IVM – ivermectin LC50 – lethal concentration that kills 50% LF – lymphatic filariasis LLIN – long-lasting insecticide-treated net malERA – malaria eradication research agenda MDA – mass drug administration MDP – Mectizan donation program MDSR – median daily survival rate MEC – Mectizan expert committee mf – microfilariae MoH – Ministry of Health MST – mass screening and treatment NGDO – non-governmental developmental organization NOC – national onchocerciasis coordinator NOCP – national onchocerciasis control program NOTF – national onchocerciasis task force NTD – neglected tropical disease OCP – onchocerciasis control program vii OEPA – Onchocerciasis Elimination Program for the Americas PBS – phosphate buffered saline PHC – primary health care PMI – president‟s malaria initiative RAPLOA – rapid assessment procedures for loiasis RBC – red blood cell RBMP – Roll Back Malaria Partnership RDT – rapid diagnostic test REA – rapid epidemiological assessment SAE – severe adverse event SAS – statistical analysis software SOx – sulfoxide STH – soil-transmitted helminth TDR – tropical disease research WHO – world health organization viii Chapter 1 – Literature review I) Malaria burden Every year, an estimated 500 million people are afflicted with malaria worldwide, killing more than one million people, most of whom are children in sub-Saharan Africa (Snow et al. 1999, Rowe et al. 2006, Hay et al. 2010a). There are now five recognized species of Plasmodium that cause malaria in humans (Cox-Singh and Singh 2008). Plasmodium falciparum is the most virulent of the Plasmodium species (Greenwood 2008), although Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, and Plasmodium knowlesi are an important cause of morbidity in areas where they occur (Singh et al. 2004, Mueller et al. 2007, Price et al. 2007, Cox-Singh and Singh 2008). Malaria represents not only a major cause of morbidity and mortality but also a severe impediment to economic development and prosperity in Africa (Gallup and Sachs 2001, Sachs and Malaney 2002, Sachs 2005). Plasmodium falciparum occurs throughout tropical and subtropical regions of Africa, Latin America, Asia, and the South Pacific (Hay et al. 2010a). Recent advancements and use of PCR-based diagnosis of human malaria infections has revealed more widespread distribution and a greater contribution of non-falciparum malaria than previously thought (Snounou et al. 1993, Rubio et al. 1999, Singh et al. 2004). Plasmodium vivax occurs in Asia, the Middle East, Latin America, and the South Pacific and has a range that extends beyond that of P. falciparum (Price et al. 2007). 1 Plasmodium vivax accounts for 50% of the malaria burden in South and Southeast Asia (Luxemburger et al. 1996, Zhou et al. 2005), between 70-80% in Latin America (Duarte et al. 2004), and about 5% in Africa (Mendis et al. 2001) although this may be an underestimate for the malaria burden in Africa (Ryan et al. 2006, Rosenberg 2007). Plasmodium malariae distribution is reported as patchy in most malaria endemic regions of the world and is most common in sub-Saharan Africa and the southwest Pacific (Mueller et al. 2007). The distribution of P. ovale is primarily limited to Africa although it has been reported from the Middle East, the Indian subcontinent, and parts of Southeast Asia (Mueller et al. 2007). Plasmodium knowlesi was only recently recognized as a significant cause of human infection (Singh et al. 2004). The distribution of P. knowlesi is restricted to Southeast Asia where macaques, the primary zoonotic reservoir hosts, occur (Cox-Singh and Singh 2008). In 2007, the Bill and Melinda Gates Foundation (BMGF) declared that malaria eradication was one of their primary goals (Roberts and Enserink 2007). Unlike the previous Global Malaria Eradication Programme (GMEP) launched by the World Health Organization (WHO), research is a major emphasis of both the current eradication agenda and the Global Malaria Action Plan (GMAP) (RBMP 2008). Both the WHO and the Roll Back Malaria Partnership endorse the eradication agenda

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