By Claire Taylor

A breakthrough in diagnosing one of the sheep industry’s most financially debilitating diseases, toxoplasmosis, may lead to future drug developments to get rid of the scourge.

Researchers at the University of Glasgow have identified a weakness in the toxoplasmosis-causing parasite within humans, which might pave the way for future drug developments, both in livestock and humans.

Toxoplasmosis is a highly infectious disease most commonly known in the UK for leading to abortions in pregnant sheep and brain damage in unborn human infants. Infection in sheep costs the industry millions of pounds each year in lost production and inefficiency.

It is the second biggest cause of abortion in sheep, recorded in 24% of cases and in 2017, 1277 cases of abortions in sheep by the disease were found.

A Glasgow study in the human form of toxoplasmosis revealed that a key enzyme, thioredoxin, is essential for the survival of the toxoplasma parasite which, if targeted, could potentially be a catalyst for new drugs to kill it.

Dr Sheiner, from the University’s of Glasgow’s Wellcome Centre for Molecular Parasitology, said: “More and more studies highlight the parasite’s sensitivity to redox imbalance – a key function of the enzyme we have studied. Targeting the thioredoxin enzyme may make them vulnerable at stages of their life that are important for infection and dissemination.

“Finding enzymes in the parasite that that we can target and that don’t influence the human host, unravels this potentially deadly parasite’s Achilles’ heel,” stressed Dr Sheiner.

The research team at Glasgow said that a potential drug could take 5-10 years before reaching clinical trials, but was a pivotal step in that process.

Toxoplasma parasite is transmitted through undercooked meat, soil, or most prominently from contact with cat faeces. Elisabeth Innes, of Moredun Research Institute, expanded on the transmission of the disease: “Cats are the definitive host of the parasite. If a young cat goes out hunting and ingests an infected bird, or mouse then it will shed the eggs from the parasite in their faeces.

“These eggs are very resistant in the environment and can live for up to three years whilst carrying the infection. These eggs will naturally become widespread, where they can be picked up by humans or, as our research shows, grazing sheep.”

Studies have shown that up to 33% of the population in the UK carry a dormant form of the parasite, but symptoms of infection in healthy adults generally go unnoticed. However, toxoplasmosis can be dangerous to unborn children and in people with compromised immune systems.

Ms Innes welcomed the knowledge of a breakthrough in research by the University of Glasgow: “Any breakthrough within the human or veterinary side of research can help inform one another, as we are dealing with the same parasite.

“Although there is a very good vaccine available for sheep, it involves a live parasite so hasn’t been licensed for use in people and its availability and administration isn’t as successful as we would like due to a very short shelf life. Therefore, any progress in identifying a weakness in the parasite is extremely important, as it may provide future answers in the development of livestock research to target toxoplasmosis also,” she added.