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New strangles vaccine unveiled

Strangles: treatment of carrier animals

Strangles: diagnosis of carrier animals

Hope of a vaccine for strangles

New strangles vaccine unveiled

Blood test for strangles carriers

Strangles Vaccine Breakthrough

Report by Mark Andrews. Published online 22.02.18

It has been a long time coming, but now an effective vaccine for strangles may finally be on the horizon.

Strangles is one of the most common bacterial infections of horses. Streptococcus equi, the organism responsible, causes horses to suffer from large pus-filled abscesses in their throat and neck. It is found throughout the world.

The disease causes significant economic losses due to the prolonged recovery time and the quarantine measures needed to restrict the spread of the disease.

Although vaccines have been available before, they have not been universally effective and have often produced unacceptable side effects. Reported problems have included abscesses at the site of injection, and clinical disease in vaccinated horses. An additional problem is that the immune response to current vaccines cannot be differentiated from that of infected animals. This complicates the management of outbreaks.

Now scientists at the Swedish University of Agricultural Sciences, the Karolinska Institute and Intervacc AB, and the Animal Health Trust (AHT), have developed a new protein-based vaccine to protect horses from strangles.

The researchers assessed the response of ponies to vaccination with various combinations of recombinant fusion proteins.

They found that optimal protection was conferred by a prototype multicomponent subunit vaccine, Strangvac 4, which contained eight proteins CNE, SclC, SclF, SclI, EAG (fused as CCE), SEQ_402, SEQ_0256 (fused as Eq85) and IdeE.

None of the ponies with any of the trial vaccines developed adverse reactions.

One further advantage of the vaccine is that it should not interfere with differentiating infected animals from those that have been vaccinated. The researchers explain that none of the antigens contained in the vaccine are included in the current ELISA tests for the detection of exposure to S. equi, and as it does not contain live or dead bacteria it will not be detected by the S. equi qPCR tests.

 “The vaccine was designed using information from sequencing the DNA of Streptococcus equi and highlights the potential that the genome-era heralds for improving the health of animals and people” explained Dr. Andrew Waller, Head of Bacteriology at the AHT.

 “We are delighted to have shown that our Strangvac vaccine protected over 80% of horses from this dreadful disease,” said Prof. Jan-Ingmar Flock, CEO of Intervacc AB, the company that produced the vaccine. “Strangles is a scourge of the equine world and the development of Strangvac has the potential to prevent many thousands of horses from falling ill each year.”

 “Transfer of the manufacturing process and production of commercial batches are underway towards the registration and launch of Strangvac,” continued Prof. Flock, “and we anticipate that Strangvac will be available for use during 2020.”

The research has been published in the journal Vaccine.

For more details, see (Open access article) :

Strangvac: a recombinant fusion protein vaccine that protects against strangles, caused by Streptococcus equi.

Carl Robinson, Lars Frykberg, Margareta Flock, Bengt Guss, Andrew S. Waller and Jan-Ingmar Flock.

Vaccine, (2018) 36,  1484–1490