A bird macrophages infected with the fungal pathogen Cryptococcus neoformans (green).

Discovery may prevent humans contracting bird flu

New research has revealed how birds can carry potential fatal infections to humans but not get ill.

Birds carry the fungus known as Cryptococcis neoformans and their droppings are thought to be a source of human infection. But how the birds themselves do not get ill has baffled scientists for some time.

Now, experts have shown that a particular white blood cell within the bird’s system, called a macrophage, is able to completely block the growth of the fungus.

In the study, the scientists found that the fungus grows slowly within the bird’s digestive tract, but it if tries to invade the bird’s body then the immune system destroys it immediately. This explains why healthy birds can still help spread the infection.

“Birds have a higher body temperature than humans, 42°C instead of 37° C, but this alone is not enough to fully stop the fungus,” said lead researcher Dr Simon Jonston.

“By studying bird cells under the microscope, we have seen that macrophage cells have the ability to completely block the growth of the fungus, which can be fatal in humans.

“Understanding where the disease comes from and how it spreads is critical. If we can learn how some animals are able to resist infection we might be able to gain insights into how we can improve the human immune response to this fungus.”

Cryptococcis neoformans is a fungus that causes fatal infections in people with a weakened immune system. It is most dangerous to individual with AIDS and is thought to cause hundreds of thousands of deaths worldwide, every year.

The research, published in Nature Scientific Reports, was carried out by the University of Sheffield and the University of Birmingham. It is part of wider, international efforts to understand and eliminate Cryptococcosis.

Dr Johnston added: “We are now working with leading scientists from all over the world to try and understand where this pathogen came from, how our bodies fight it and what we can do to help our own immune system defend us from this fungus and other related infections.

“Many human diseases are spread by birds, but we know surprisingly little about their immune systems. Discovering how they resist otherwise fatal infections offers the hope of improving our ability to intervene in this cycle and prevent a diverse range of human diseases.”

He added: “In addition, infectious diseases of birds themselves are a major threat to agriculture, such as when 170,000 poultry were culled due a suspected bird flu outbreak.

“Learning more about the bird immune system is an important step in developing new ways to combat such infections.”

Image (C) The University of Sheffield.