Delete dublicates for each row from several columns

I made the the fowolling list in order to explain what i need too do:

1st pet 2nd pet 3rd pet 4th pet
dog cat dog
cat bunny
bunny bunny cat dog
fish dog


I want to remove duplicated pets in each row. For each row where there is a repeating pet,I have to remove it (dog in the first row third column and bunny 3-rd row ,secod column.)
The real list is with 800 rows and 15 columns.
Can you please advise me how to do it