April 2016

The Miracle of Bti

Dr. Yoel Margalith

When Dr. Yoel Margalith (1933 – 2011) observed dying Culex pipiens larvae in a temporary pond in the Negev desert in 1976, the course of public health – indeed, all of human history – would forever be changed. From samples of that pond bed, Margalith isolated Bacillus thuringiensis israelsis (Bti), the soil bacterium turned biological insecticide that has since saved of millions from mosquito- and black fly-borne diseases.

Following his discovery, Dr. Margalith devoted much of his career introducing the concept of Integrated Vector Management (IVM) around the world, with Bti featured as a cornerstone intervention. His work earned him the nickname “Mr. Mosquito,” particularly in Africa, South America, the Middle East, and Central Europe – parts of the developed and developing world most affected by mosquito-borne disease. In 2003, Margalith was awarded the prestigious Tyler Prize for Environmental Achievement.

While it is impossible to precisely quantify the full magnitude of Margalith’s discovery, it is widely accepted that use of Bti is responsible for saving millions of lives around the world. Bti has been called “the most powerful and environmentally-friendly biological alternative component in integrated programs to control disease vectors.”1 In addition to its strong and highly specific toxicity to Aedes, Culex, Anopheles, and other Dipteran larvae, the power of Bti resides in its ability to circumvent the onset of resistance.

Bti contains four major and two minor polypeptide cry toxins (cry4Aa, cry4B*a, *cry11Aa, cyt1Aa, cry10Aa, and cyt2Ba) that combine to compromise Dipteran gut membranes with synergistic interaction and multiple modes of action. Given its complex nature, no field resistance of Bti has been observed since it was first registered in 1983. Use of Bti as a foundational element in IVM programs continues to gain momentum around the world. Continuing advancements in formulation and application technology have made it a proven intervention for a host of vector-borne diseases such as malaria, chikungunya, dengue, West Nile virus, Onchocerciasis, and Zika virus, among others.

1 Ben-Dov, Eitan.”Bacillusthuringiensis subsp. israelensis and Its Dipteran Specific Toxins.”Toxins 2014, 6, p. 1223.


The percentage of dengue and malaria vectors susceptible to Bti.


The percentage of documented cases of field resistance for Bti after more than 30 years of use.