A QUEENSLAND-developed vaccine for a hitherto incurable disease in northern cattle effectively stopped the infection, scientists have reported.
All bulls vaccinated against the venereal disease Trichomonosis cleared the infection, said UQ veterinary science professor Gry Boe-Hansen.
The vaccinated bulls exhibited a significantly shorter infection duration, only 14 day compared with 40 days, and had a lower parasite load compared to control animals.
Prof Boe-Hansen (pictured) said successful development of a vaccine could save valuable seedstock which currently have to be culled to prevent them infecting cows during natural mating. The condition causes cows to abort, or renders them infertile. Bulls show no symptoms.
It is currently estimated that between 10 and 15pc of bulls slaughtered from northern herds carry the infection.
Bovine trichomoniasis is caused by a protozoan parasite, Tritrichomonas foetus. Vaccines for the protozoa are available overseas, but not in Australia, however these overseas vaccines do not prevent infection.
Addressing the 2025 TropAg conference in Brisbane, Prof Boe-Hansen said vaccines were available in South America, Latin America and North America that reduce the shedding of the organism and the incidence of their spread, to a certain degree.
“But they’re not registered in Australia and that’s the big deal here. These two vaccine types are available overseas but we don’t have them in Australia due to our biosecurity issues,” she said.
“So, since they are unavailable we have to deal with the fact that we have to use test-and-slaughter of positive animals to reduce infection rates in our herds.”
She continued: “Treatment would be great, but the problem is that it’s a protozoa organism. We don’t have any products available on the market registered for food animals.”
A 2023 MLA project was established at UQ from which strains from the NT and Queensland were selected. An initial pilot vaccine trial of an experimental vaccine delivered a 67% efficacy rate among tropically adapted bulls aged five to eight years. Older bulls proved the most resistant.
A more recent vaccine trial at UQ’s Pinjarra Hills research facility used younger bulls. The research team gave 30 bulls two doses four weeks apart and then challenged them with infection twice. The team compared the bulls’ responses to those of another 30-head control group.
“We kept assessing them using blood samples and scrapings from the preputium (foreskin) area of the bull to detect what response we had,” Prof Boe-Hansen said.
Among the vaccinated bulls, immune levels lifted immediately post the first vaccine, and levels increased after the second dose.
Vaccinated bulls exhibited a significantly shorter infection duration, only 14 day compared with 40 days, and had a lower parasite load compared to the control animals. “So the risk of infection was actually decreased,” she added.
Prof Boe-Hansen said the vaccine was well-tolerated, causing only mild local reactions and made with no significant differences in weight or ADG.
Longevity of effectiveness will be the focus of the next round of trials. Researchers will be looking at the vaccine as a preventative measure, rather than treatment, to reduce infection rates, she said, adding a future vaccine could possibly combined with other venereal-type vaccines.
“This vaccine is potentially a very important tool in regions of high prevalence where testing and culling may be logistically or economically challenging,” she said.
Other researchers involved in the work were Harvey Santos, Dr Kieren Mccosker, Michael McGowan, Dr Hannah Siddle, Dr Loan Nguyen, Ali Raza and Professor Ala Tabor.