Bats now deserve some new levels of respect. Like their fellow Cave dweller the Megalania, they have a chance to infect you with Mega Rabies (though only a chance rather the 100% like Megalania)
They are easy to spot and avoid using bug repellent. But due to the new Biological weapon element of them. Engage at a distance where possible. Fight them with sword and pike only as a last resort. Make sure you have a stock of Antidotes or Wyvern Milk before any Splunking
I didn't see any tip on fighting these annoying creatures. I would recommend carrying a shot gun on you. Preferably an Apprentice or higher. Many people like the pump action for the bigger clip, but simple shitty does more damage. Way until close for more damage dealt.