Varolis was founded to bundle IP, knowledge, research data and expertise into one company with
the aim to develop Lithium as veterinary drug under the trade name LIMITEX. LIMITEX is a novel,
effective and easy to apply agent to control the parasitic Varroa mites (Varroa destructor).
Honey Bees are instrumental as pollinators both ecologically and economically. The parasitic mite
Varroa destructor is the greatest biological threat to honey bees (Apis mellifera) worldwide and has
globally infested every hive. Untreated colonies die within few years. Current methods of Varroa
control include chemical acaricides, organic acids, essential oils and manual procedures. All these
approaches are labor intensive or insufficient, cause resistance formation in Varroa mites and can
harm adult bees and larvae. Despite all treatment efforts, colony losses as consequence of Varroa
infestation are increasing.
The project started in 2015, when Scientists at SiTOOLs Biotech GmbH explored the possibilities to
use siRNAs as novel agents against the Varroa mite, Varroa destructor. In collaboration with the
apicultural state institute in Hohenheim, headed by Dr. Peter Rosenkranz, siRNAs directed against
essential genes in Varroa were fed to bees. The concept was based on siRNAs entering the
hemolymph of bees after ingestion and passing them on to parasitic mites feeding on honey bees’
hemolymph. Once siRNA was taken up by Varroa, the siRNA would bind to complementary RNA-
strands within the mite, downregulate the expression of essential Varroa genes and eventually kill
the parasite. For this, experiments with caged bees carrying mites were carried out: Mites on bees
that were fed sucrose syrup containing siRNAs were killed efficiently in a period of only few days.
However, negative controls performed in parallel indicated that RNAi might not be the mechanism by
which the mites were killed.
Thorough and patient follow experiments then demonstrated that not siRNAs but a contaminating
salt, Lithium Chloride, was responsible for the observed effect. SiRNAs without Lithium Chloride did
not exhibit anti-Varroa activity, whereas LiCl alone was highly effective in killing mites by systemic
administration to honey bees.
In the following years the collaboration between siTOOLs Biotech GmbH and the apicultural state
institute in Hohenheim developed a robust and reliable treatment regimen based on Lithium salts.
The therapy is highly effective, killing more than 95% of mites under field conditions, adult bees
tolerate Lithium salts well and Lithium does not leave residues in bee products as honey, bee bread
or wax. The treatment is reliable and the application is easy. In fact, Lithium containing sugar water is
offered to the bees as part of the feeding after honey harvest in late summer. In 2023 Dr. Stefan
Hannus set out to finally obtain market approval as veterinary medicine for the treatment of
Varroosis. He founded Varolis in March 2023 together with Prof. Dr. U. Jacob, Dr. D. Buehler, and Dr.
Frank Becker.