GETTY/NC Mohamed Abrini was found with a rudimentary dirty bomb

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Mohamed Abrini was said to have made the rudimentary bomb with the intention of spreading bacterial infection when he wreaked havoc in the worst terror attack in Belgian history. The 31-year-old, who was also involved in last year's Paris attacks, was identified as the "man in the hat" after going on the run following the suicide bombings which resulted in 32 deaths and 270 injuries at the airport and at the city’s Maelbeek subway station.

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Now a leading expert says the animal testes bomb shows ISIS leaders are continually trying to develop terrifying biological weapons - even in their crudest form - to literally sicken the public. Dr Amesh Adalja, a Senior Associate at the University of Pittsburgh Medical Center for Health Security, said: "The news that ISIS may have been interested in a biological weapon is not surprising, as terrorist groups from Al Qaeda and Aum Shinrikyo have expressed this same effort.

PA Abrini was identified as the ’man in the hat’ involved in the Brussels attacks

"Biological weaponry is as old as civilisation and through history has moved from the very crude such as poisoning wells to the very sophisticated.

It is a dangerous step that demonstrates unequivocal interest in biological weapons Dr Amesh Adalja

"Belgian reports that the suspect had plastic bag filled with animal excrement and testes argues that the potential capacity of this particular individual is towards the more basic end of the spectrum. “Such crude preparations hearken back to ancient history when warriors would coat their spears and swords in animal excrement so as to heighten the chance of a post-traumatic infection occurring. “Similarly, during the Vietnam War the Vietcong placed stakes that were laden with feces, called Punji sticks, in the paths of US troops with the intention of them being impaled and then infected with the fecal bacteria.

"These types of biological weapons are not, under ordinary circumstances, able to inflict wide scale harm as, for example, an aerosol release of anthrax could, but are still very effective in fomenting fear. “However, creating such crude preparations cannot be ignored, as it is nonetheless a dangerous step that demonstrates unequivocal interest in biological weapons." In February, British and American special forces trained in secret for a biological or chemical attack in the UK.

NC Experts have warned that ISIS are developing biological weapons

The special operatives undertook Chemical, Nuclear, Radiological and Biological (CBRN) training sanctioned by COBRA, Britain's emergency cabinet response team chaired by David Cameron. Belgian police, acting after the March terror attacks, conducted a number of raids in apartments across the city following the attacks and discovered explosive devices containing nails and an ISIS flag. They also discovered Abrini had created a bomb using animal testes and fecal matter before he was finally apprehended in April.

Brussels terrorist attacks Wed, March 22, 2017 The Brussels airport and Metro bombings in pictures, including the aftermath of the tragic scenes. Play slideshow AFP/Getty Images 1 of 61 A member of the civil protection holds his face in his hands as he come back from the Maalbeek metro station in Brussels