it would depend on which monster actually comes onto the field first.
if bloo-d was already on the field before Vennominaga the Deity of Poisonous Snakes is summoned to the field, then Vennominaga the Deity of Poisonous Snakes' effect would be negated, definitely.
if Vennominaga the Deity of Poisonous Snakes was on the field, then i believe bloo-d would NOT negate its effect.
quoting from official rulings:
This card is not affected by the effects of any other Monsters, Spells or Traps, even effects that do not target.