Initial Assessment of the Ability of Ivermectin to Kill Ixodes scapularis and Dermacentor variabilis Ticks Feeding on Humans

Abstract

We demonstrate a novel method to confine ticks to human subjects to study tick-borne diseases. While there was a trend toward I scapularis morbidity and mortality in the ivermectin arm, the low number of ticks that attached in the placebo group limited our analysis. Most ticks began feeding in the last 12 hours of the experiment, significantly limiting their exposure to ivermectin. Ivermectin does not cause early death in D variabilis adults.

The Use of Ivermectin to Kill Ixodes Scapularis Ticks Feeding on Humans

“…However, too few ticks attached to study subjects to reach statistically meaningful conclusions. 11 In this study, we increased the number of study subjects, ticks, and attachment time to increase the number of attached ticks. 11…”

“…11 In this study, we increased the number of study subjects, ticks, and attachment time to increase the number of attached ticks. 11…”

“…8 A single 150 to 200 mg/kg dose of ivermectin has shown effectiveness against several human parasites, including the ectoparasites lice, scabies, mosquitoes, and bed bugs. [9][10][11][12] Ivermectin has been used extensively in the control of Onchocerciasis (river blindness) and filariasis and is administered to an estimated 50 million people annually. 13,14 As the only approved endectocide for human use, approximately 1 billion ivermectin treatments have been given to humans over the past 30 years.…”

“…14,15 Although ivermectin has been used in veterinary medicine to kill ticks on animals, there is only a single previous report about the use of ivermectin to kill ticks on humans. 11 Our study was designed to determine whether a single dose of oral ivermectin could be used to kill I scapularis nymphs and adult females attached to the body of human hosts. We reasoned that if ivermectin could kill I scapularis within 30 hours of tick attachment, then B burgdorferi could not be transmitted and ivermectin potentially could be used to prevent tick-borne disease.…”

“…Previously it has been shown that ivermectin is effective at killing several different human parasites at 200 mg/kg, but 400 mg/kg was shown to be more efficacious for lice with few additional side effects. [8][9][10][11][12][13][14][15] We chose to use 400 mg/kg in our study with the rationale that a single large dose of the drug would be the ideal option should ivermectin ever be adopted for wider use in the prevention of tick-borne disease. Hypothetically, ivermectin could be taken shortly after a person has a potential tick exposure and would kill the tick when it starts to feed but before transmitting tickborne disease.…”