Targeting cattle for malaria elimination: marked reduction of Anopheles arabiensis survival for over six months using a slow-release ivermectin implant formulation
Chaccour CJ (1,2,3), Ngha'bi K (4,5), Abizanda G (6), Irigoyen Barrio A (7), Aldaz A (8), Okumu F (9,10), Slater H (11), Del Pozo JL (9,12,13), Killeen G (4,14).
(1) Instituto de Salud Tropical, Universidad de Navarra, Pamplona, Spain.
(2) ISGlobal, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain.
(3) Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, United Republic of Tanzania.
(4) Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, United Republic of Tanzania.
(5) School of Health Sciences, University of Dar es Salaam, Dar es Salaam, Tanzania.
(6) Centro de Investigación Médica Aplicada, Pamplona, Spain.
(7) Drug Development Unit Universidad de Navarra (DDUNAV), Pamplona, Spain.
(8) Department of pharmacy, Clínica Universidad de Navarra, Pamplona, Spain.
(9) Instituto de Salud Tropical, Universidad de Navarra, Pamplona, Spain.
(10) School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.
(11) MRC Centre for Outbreak Analysis & Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
(12) Department of Microbiology, Clínica Universidad de Navarra, Pamplona, Spain.
(13) Infectious Diseases Division, Clínica Universidad de Navarra, Pamplona, Spain.
(14) Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
Mosquitoes that feed on animals can survive and mediate residual transmission of malaria even after most humans have been protected with insecticidal bednets or indoor residual sprays. Ivermectin is a widely-used drug for treating parasites of humans and animals that is also insecticidal, killing mosquitoes that feed on treated subjects.
Mass administration of ivermectin to livestock could be particularly useful for tackling residual malaria transmission by zoophagic vectors that evade human-centred approaches. Ivermectin comes from a different chemical class to active ingredients currently used to treat bednets or spray houses, so it also has potential for mitigating against emergence of insecticide resistance. However, the duration of insecticidal activity obtained with ivermectin is critical to its effectiveness and affordability.
A slow-release formulation for ivermectin was implanted into cattle, causing 40 weeks of increased mortality among Anopheles arabiensis that fed on them.
For this zoophagic vector of residual malaria transmission across much of Africa, the proportion surviving three days after feeding (typical mean duration of a gonotrophic cycle in field populations) was approximately halved for 25 weeks.
This implantable ivermectin formulation delivers stable and sustained insecticidal activity for approximately 6 months. Residual malaria transmission by zoophagic vectors could be suppressed by targeting livestock with this long-lasting formulation, which would be impractical or unacceptable for mass treatment of human populations.
CITATION Parasit Vectors. 2018 May 4;11(1):287. doi: 10.1186/s13071-018-2872-y