Two Parasites Are Better Than One: Co-Infection Reduces Cattle-Death

First Posted: Mar 23, 2015 04:46 PM EDT

If you heard that you were infected with two parasites, you'd probably think of this as a really bad thing. Well, not necessarily, according to recent findings published in the journal of Science Advances (at least for cattle, that is.) 

Researchers found that when calves were infected by two parasite species at the same time, one parasite rendered the other far less deadly.

"We now know that certain parasite co-infections can have strong protective effects--as strong as those offered by vaccines--against certain deadly diseases," said infectious disease epidemiologist Thumbi Mwangi of Washington State University's Paul G. Allen School for Global Animal Health, in a news release

This is a huge issue for those in parts of east and central Africa. Every year, millions of cattle die each year from tick bites that infect cows that then inject the parasite Theileria parva (T. parva) via saliva, attacking the white blood cells, causing what's similar to fast-moving lymphoma in humans.

In the study, researchers monitored 548 shorthorn zebu calves that belonged to consenting smallholder farmers from birth to one year. Before the end of the year, findings showed that about 17 percent of the calves died, with blood tests revealing that 454 of those who survived, 86 percent were infected by the parasite. Yet only 18 percent showed symptoms.

While studying the animals, researchers found that the healthy calves were also infected by a less harmful but related parasite species known as Theileria mutans or Theileria velifera.

"A working hypothesis is that the well-known immunomodulatory effects of T. parvaare moderated by the presence of (T. mutans and T. velifera), thereby reducing the severity of infection," researchers noted.

The vaccine to help with East Coast fever is effective. However, with anything, there are drawbacks. It is expensive and it must be administered along with a syringe-full of antibiotics.

Yet in the future, it may be possible to vaccinate calves with benign T. mutans or T. velifera parasites--which would be less costly and easier to do.

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