Commercially-canned foods have already been cooked

Update:29-09-2018
Summary:

Commercially-canned foods have already been cooked after sealing inside the can - and at a much higher temperature than you can provide in a kitchen: 121 degrees C (250 degr F). There is no such thing as ‘raw, canned tuna’.

Hence, it’s completely safe from that perspective.

However, tuna (also called ‘tunny’ in the UK) is a scombroidiae species, and as such it can be the source of an uncommon human illness due to too much histamine - even in the canned form. The process is due to the freshly-caught fish being kept at a warm temperature (perhaps on a trawler deck or a wharf) for several hours. During this time, a common bacterium Proteus morganii, converts the naturally occurring amino acid histadine into histamine.Canned tuna production line  This can be especially uncomfortable for people on a histaminase-reducing drugs such as Isoniazid. The reaction can be similar to a moderately-strong allergic reaction. This form of food poisoning is called Scombroid poisoning, and it can continue to be a problem even if the tuna is subsequently canned because the histamine is resistant to the retort heat process.