Current vaccines, experimental immunization trials, and new perspectives to control selected vector borne blood parasites of veterinary importance

Authors: ALZAN, HEBA - Washington State University; SAIED, MONA - Washington State University; Suarez, Carlos

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2024
Publication Date: 11/13/2024
Citation: Alzan, H.F., Saied, M.M., Suarez, C.E. 2024. Current vaccines, experimental immunization trials, and new perspectives to control selected vector borne blood parasites of veterinary importance. Frontiers in Veterinary Science. 11. Article 11484787. https://doi.org/10.3389/fvets.2024.1484787.
DOI: https://doi.org/10.3389/fvets.2024.1484787

Interpretive Summary: Vector-borne blood parasites cause significant economic losses in farm animals worldwide and can also infect humans in some cases. In this review, we examine current vaccines available, vaccine research approaches, and trials for diseases caused by selected Babesia, Theileria, Anaplasma, and Trypanosoma parasites. Control of these parasites primarily relies on vector control, chemotherapeutic treatment, and disease prevention through vaccination. However, most of these approaches have practical limitations, including environmental concerns related to chemical agents used for vector control or chemotherapeutic treatment. Although vaccines against these blood parasites are already available, they still have many disadvantages such as lack of practicality, unsuitability in non-endemic regions, and the spread of other infectious agents, especially applicable for live vaccines. This review highlights recent vaccine development efforts to control blood parasites in farm animals and discusses approaches to vaccine development based on recombinant antigens, vector vaccines, and live attenuated and/or genetically modified parasites. Despite intensive efforts, effective subunit vaccines against blood-stage parasites have remained to be developed. Using lessons learned from previous vaccine development efforts and emerging technologies to define the immune mechanisms of protection, appropriate adjuvants, and protective antigens will help expand the toolkit for control of these burdensome diseases.

Technical Abstract: Parasite infections, which are transmitted by vectors such as ticks and blood-sucking arthropods, pose a significant threat to both human and animal health worldwide and have a substantial economic impact, particularly in the context of worsening environmental conditions. These infections can manifest in a variety of symptoms, including fever, anemia, jaundice, enlarged spleen, neurological disorders, and lymphatic issues, and can have varying mortality rates. In this review, we will focus on the current state of available vaccines, vaccine research approaches, and trials for diseases caused by vector-borne blood parasites, such as Babesia, Theileria, Anaplasma, and Trypanosoma, in farm animals. Control measures for these infections primarily rely on vector control, parasiticidal drug treatments, and vaccinations for disease prevention. However, many of these approaches have limitations, such as environmental concerns associated with the use of parasiticides, acaricides, and insecticides. Additionally, while some vaccines for blood parasites are already available, they still have several drawbacks, including practicality issues, unsuitability in non-endemic areas, and concerns about spreading other infectious agents, particularly in the case of live vaccines. This article highlights recent efforts to develop vaccines for controlling blood parasites in animals. The focus is on vaccine development approaches that show promise, including those based on recombinant antigens, vectored vaccines, and live attenuated or genetically modified parasites. Despite intensive research, developing effective subunit vaccines against blood stage parasites remains a challenge. By learning from previous vaccine development efforts and using emerging technologies to define immune mechanisms of protection, appropriate adjuvants, and protective antigens, we can expand our toolkit for controlling these burdensome diseases.