FDA Letter to Stakeholders about the Asian Longhorned Tick and Theileriosis
August 21, 2026
Dear Veterinary, Animal Health, and Industry Partners,
The FDA’s Center for Veterinary Medicine (CVM) is aware of the emerging threat of the Asian longhorned tick (ALHT), which can spread an infectious disease called Theileriosis, and the need for effective countermeasures to combat this threat. Theileriosis, caused by certain genotypes of T. orientalis, can cause serious health problems in cattle, including anemia, fever, weakness, loss of pregnancy, and death. Presently, there are no products in the U.S. that are FDA-approved to control ALHT or treat/prevent Theileriosis in cattle. CVM encourages drugs sponsors with candidate therapeutic products that could prevent, treat, or control ALHT or T. orientalis to approach the Agency.
CVM has reviewed available literature about therapeutic products related to both ALHT and T. orientalis and has been in communication with the U.S. Department of Agriculture, international partners, and academic experts to gather as much information as possible about the management of ALHT and T. orientalis. We are aware of research being conducted on a drug called buparvaquone.1, 2 Buparvaquone is not currently FDA-approved as an animal drug in the United States. Literature and publicly available information from New Zealand and Australia indicate the drug may remain in certain muscle and liver tissue of cattle up to and beyond 300 days.3, 4 The product is not approved in either New Zealand or Australia, although both have permitted limited, restricted use.5, 6 CVM believes additional research and investment are necessary to speed the identification and development of therapeutics for T. orientalis.
CVM is optimistic about possible products to treat, control, and/or prevent ALHT in cattle and such products may qualify for FDA’s expanded conditional approval pathway and/or FDA’s priority zoonotic animal drug designation program. There is evidence that ALHT can harbor and spread zoonotic diseases, and reports of this tick biting humans in the U.S.7
The Emergency Use Authorization (EUA) mechanism to facilitate access to animal drugs is not currently available to address ALHT or T. orientalis. FDA can issue Emergency Use Authorizations (EUAs) only when there has been a declaration made by the Secretary of Health and Human Services that circumstances exist to justify the use of this authority, such as in cases of a potential public health emergency, as set by statute. The statute does not contain an explicit statutory pathway for the use of EUA authority to address emerging animal health threats that do not pose a public health risk. The first and only determination and declaration made that has allowed the Agency to issue EUAs for animal drugs has been for New World screwworm.
CVM is committed to working with our veterinary, animal health, and cattle producer partners to review the safety and efficacy of drug submissions with indications for the prevention, control, and/or treatment of Theileriosis and ALHT.
If sponsors have a product that could help control ALHT or T. orientalis, or if sponsors or research partners are interested in receiving technical assistance on potential research into ALHT or T. orientalis products please email us at AskCVM@fda.hhs.gov.
Sincerely,
FDA’s Center for Veterinary Medicine
1 Transient efficacy of buparvaquone against the US isolate of Theileria orientalis Ikeda genotype in sub-clinically infected cattle - PMC
2 https://pmc.ncbi.nlm.nih.gov/articles/PMC8540055/
3 https://pubmed.ncbi.nlm.nih.gov/27373797/
4 https://www.mla.com.au/research-and-development/reports/2013/buparvaquone-tissue-residue-study/
5 https://www.mpi.govt.nz/dmsdocument/51262-Animal-Products-Notice-Specified-Agricultural-Compounds2022
6 https://permits.apvma.gov.au/PER87537.PDF
7 First Recognized Human Bite in the United States by the Asian Longhorned Tick, Haemaphysalis longicornis | Clinical Infectious Diseases | Oxford Academic