1. Kevin Kobylinski 1,2, Alongkot Ponlawat 2, Ratawan Ubalee 2, Brian Foy 3, Joel Tarning 4, Thanaporn Wattanakul 4, MAJ Wes McCardle 2, CDR Dan Szumlas 1, and LTC Jason Richardson 1,2,5 kevin.kobylinski.gst@afrims.org 1 Walter Reed Army Institute of Research (WRAIR): Entomology Branch 2 Armed Forces Research Institute of Medical Sciences (AFRIMS): Department of Entomology 3 Colorado State University: Department of Microbiology, Immunology and Pathology 4 Mahidol-Oxford Tropical Medicine Research Unit 5 Armed Forces Pest Management Board Ivermectin mass drug administration to humans as a potential tool for malaria elimination Lethal concentration of ivermectin that kills GMS Anopheles Ivermectin concentration (ng/ml) dirus sawadwongporni campestris minimus gambiae = LC 50 = LC 25 = LC 5 n=5029, r=6 n=1431, r=4 n=2786, r=4 n=2376, r=6 n=2013, r=8 (reference) Various concentrations of ivermectin were blood fed to An. dirus, An. sawadwongporni, An. campestris and An. minimus via membrane feeders Mosquito survivorship was monitored for seven days A non-linear mixed model (Kobylinski et al. 2010) was used to estimate the lethal concentration that killed 50, 25, and 5 (LC 50, LC 25, LC 5 ) percent of mosquitoes 180 160 140 120 100 80 60 40 20 0 0 1 2 3 4 5 6 7 200 μg/kg 400 μg/kg 800 μg/kg Ivermectin concentration (ng/ml) Time (days) Model estimates for 200, 400, 800 μg/kg doses GMS Anopheles LC 50 ( ) and LC 25 ( ) values plotted on model estimates dirus sawadwongporni campestris minimus gambiae Time (hours) Ivermectin concentration (ng/ml) P=0.0129 P=0.0007 P=0.0010 P=0.0003 P=0.0032 P=0.0002 P<0.0001 Number of oocysts per An. dirus Sporontocidal impact of ivermectin on P. vivax in An. dirus Funding Sources The Military Infectious Disease Research Program, US Armed Forces Health Surveillance Center: Global Emerging Infections Surveillance Network, Colorado State University CRC 1686174, the Bill & Melinda Gates Foundation OPP1095931 and Grand Challenges Explorations grant 51995, and the National Institute of Allergy and Infectious Diseases grants R21-A1079528 and R01- A1094349-01A1. This research was performed while the author held a National Research Council Research Associateship Award at the Walter Reed Institute of Research – Armed Forces Research Institute of Medical Sciences. Disclaimer Material has been reviewed by the Walter Reed Army Institute of Research – Armed Forces Research Institute of Medical Sciences. There is no objection to its publication. The opinions or assertions contained herein are the private views of the authors, and are not to be construed as official, or as reflecting true views of the Department of the Army or the Department of Defense. Background Ivermectin is an extremely safe oral drug, with over 300 million treatments distributed annually by mass drug administration (MDA) for onchocerciasis and lymphatic filariasis elimination in Africa and Latin America Ivermectin can reduce the survivorship of African Anopheles including: An. gambiae (Chaccour et al. 2010, Sylla et al. 2010, Ouédraogo et al. 2014), An. arabiensis (Fritz et al. 2012), and An. funestus (Ouédraogo et al. 2014), suppresses P. falciparum transmission (Kobylinski et al. 2011, Alout et al. 2014) and effects four out of five variables in the vectorial capacity equation (see right figures) A recent clinical trial showed that ivermectin is safe and well tolerated when administered with artemther-lumefantrine (Ouédraogo et al. 2014), and modelling efforts predict that ivermectin MDA coupled with artemisinin combination therapy (ACT) MDA in Africa would accelerate elimination efforts (Slater et al. 2014) Ivermectin can reduce the survivorship of Greater Mekong Subregion (GMS) Anopheles including: An. dirus, An. minimus, An. campestris, and An. sawadwongporni (see below) Ivermectin MDA fulfills many of the demands for novel vector control interventions put forth by the Malaria Eradication Research Agenda Consultative Group on Vector Control (Alonso et al. 2011) including: a different mode of action from currently used insecticides, it targets both indoor- and outdoor-feeding Anopheles, an avoidance of behavioral resistance mechanisms, an integration with current vector control tools, and it alters the mosquito population age structure (Alout et al. 2014) Ivermectin MDA directly targets exophagic and endophagic human-feeding Anopheles regardless of feeding time, thus it could be a powerful new tool to aid the current artemisinin-resistance containment in the GMS and malaria elimination efforts worldwide (www.mectizan.org) (Kobylinski) Vectorial Capacity V – average number of potentially infective bites that will be delivered by all vectors feeding on a single host in one day p – daily probability of adult mosquito survivorship a – daily probability an Anopheles feeds on a human (human bloodmeal index x feeding frequency) n – duration of the extrinsic incubation period b – vector competence (ie. proportion of Anopheles that ingest Plasmodium and successfully become infectious) m – vector density in relation to the host m a 2 p n b -lnp V = Ivermectin ingestion delays the time to re-feed in An. gambiae (Kobylinski et al. 2010) (χ 2 = 23.83, P < 0.0001, Hazard ratio = 7.656 [3.487, 18.63]) Effect of ivermectin in an African context Effect of ivermectin in a Greater Mekong Subregion context Ivermectin PK data from 23 adult Thai (12 F: 11M) (Na-Bangchang et al. 2006) raw data kindly provided by Dr. Kesara Na-Bangchang Data re-fitted using nonlinear mixed-effects modelling (NONMEM) Standard dosing of 200 ug/kg was assumed (no individual dose data) Simulations (n=500) were performed for a standard person weighing 56 kg pharmacokinetic models kindly created by Dr. Joel Tarning and Thanaporn Wattanakul Escalating concentratins of ivermectin reduce number of P. vivax oocysts per An. dirus Ongoing work indicates that ivermectin also reduces proportion of vectors that develop P. vivax oocysts The 400 μg/kg concentration appears to be ideal as it reaches the LC 50 of An. dirus Ivermectin (400 μg/kg ) is extremely safe and well tolerated Future directions Clinical trials to investigate combination of ivermectin and dihydroartemisinin plus piperaquine will commence soon Modelling efforts will be used to determine frequency of ivermectin MDAs to maximize impact on transmission Perform repeated ivermectin MDAs with or without ACTs in Africa and the GMS and monitor impacts on entomological (eg. vector density, population age structure, and sporozoite rate) and parasitological (eg. symptomatic and asymptomatic Plasmodium prevalence, and molecular Force of Infection) indices of transmission DDPI Stage 7 Oocyst 12 Sporozoite 14 Sporozoite χ 2 = 15.48, P = 0.0002 χ 2 = 19.96, P < 0.0001 χ 2 = 13.47, P = 0.0003 * * * Ivermectin (LC 25 ) inhibits the sporogony of P. falciparum in An. gambiae (Kobylinski et al. 2012) Ivermectin MDA reduces the proportion of wild P. falciparum-infectious An. gambiae (Alout et al. 2014) Mean percent P. falciparum infectious An. gambiae Time relative to MDA (days) *Treatment x time was significant (χ 2 = 25.89, P < 0.0001). Mean sporozoite rate in control villages did not differ significantly (P=1, while the sporozoite rate significantly reduced the first (P = 0.0074) and second (P=0.0018) weeks after MDA 60 50 40 30 20 10 0