Immunogenicity and efficacy of an Australian whole‑cell killed Tritrichomonas foetus vaccine in experimentally challenged young bulls.

Whole-cell killed T. foetus vaccine reduces infection duration and parasite burden in bulls.

This study evaluated a novel whole-cell killed Tritrichomonas foetus vaccine developed from an Australian isolate (TfOz5 Queensland strain) in young bulls. Sixty tropical composite bulls were divided into vaccinated (n=30) and control (n=30) groups. Vaccinated animals received two subcutaneous doses of heat-inactivated vaccine adjuvanted with Montanide ISA 61 VG (5×10⁷ cells/dose) one month apart. Both groups underwent experimental challenge with live T. foetus at two and six weeks post-vaccination using a Northern Territory isolate. The vaccine demonstrated excellent safety, causing only mild local reactions with no impact on weight gain. Vaccinated bulls showed significantly reduced infection duration (14 versus 40 days, p=0.0044) and lower parasite DNA burden compared to controls. The vaccine induced robust systemic IgG responses but failed to generate meaningful mucosal IgA responses. These findings support the development of this locally sourced vaccine as a potential control strategy for bovine trichomonosis in Australia, addressing a significant gap in available preventive options for this economically important reproductive disease.

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