A revolutionary field test for East Coast fever

A highly sensitive, affordable and rapid test has been developed for East Coast fever (ECF) by scientists at the International Livestock Research Institute (ILRI).

The test breaks new ground by using a variant of the Cas enzyme, popularized for its use in CRISPR gene editing and has been specifically tailored for farmers to carry out in field conditions at the pen-side of livestock holdings.

And the technology poses more exciting possibilities.

'The beauty of it is you can adapt this technology to any disease,' says Nicholas Svitek, ILRI senior scientist and PhD supervisor of Robert Muriuki, the two researchers who developed the test.

ECF is a pervasive disease of cattle which is caused by the Theileria parva parasite, a single-celled microorganism small enough to live inside cattle white blood cells.

T. parva is spread by another, larger parasite, the tick, which sucks up and injects sporozoites (the infecting stage of the parasite) in cattle when feeding.

The disease is a major constraint on cattle farming. Endemic in over a dozen African countries, its symptoms can range from mild to severe in cattle, causing fever, difficulty breathing and muscle wasting. Cattle may die within 3 weeks after infection, and any that survive will remain weaker and less productive.

There are drugs to treat ECF, and there is a vaccine. But these options are often limited by costs and availability.

If a farmer notices an animal appearing sick, they need to know the best course of action. What treatment drugs should they purchase? If it looks like an infectious disease, are other animals likely to have been affected, and which should be vaccinated?

Furthermore, as ECF can be so prevalent in some areas, farmers will often assume it is the cause of symptoms and provide treatment accordingly. But if the cause is actually another disease, they will still end up losing an animal.

In short, what farmers need is a reliable, sensitive and fast test for ECF that can be used in the field. This has not existed-until now.

The current method to diagnose ECF relies on taking a blood sample, then transporting it to a specialized laboratory to analyze it for traces of T. parva DNA.

This process can take weeks, and in the meantime the disease might continue to spread within herds or across land regions as cattle are moved. Animals might die, and a farmer and family's livelihood may be ruined.

Svitek and colleagues thought of another approach in 2021.

Since its first publication in 2012, the Nobel Prize-winning technology of CRISPR-Cas9 gene editing has been making a growing wave in the field of molecular biology.

The approach uses specialized DNA components found in bacteria-the so-called CRISPR section can identify specific DNA sequences, while the Cas9 enzyme can cut them out.

Photo credit: Cattle in Isiolo County, Kenya (ILRI/Geoffrey Njenga)

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