True, Warwick clears fast but pre-6 his ganks are, at best, sub-par. Compare with Fiddle and Naut who can gank at 4 and SHaco who can gank at 2. Thus you should focus on farming to 6 and covering lanes for mid and top when they b and only gank if the enemy is an idiot and so overextended its a free kill if you can stick to them.
I have never built wriggles on Warwick unless I am being hopelessly outfarmed, and there aren't a lot of junglers that outfarm Warwick with his crazy sustain... Except the junglers that farm your jungle too. The best protection against them pre-6 and even post-6 is to have the corresponding lane ward red when you are done with blue. If the enemy started red and they come after your blue, well, odds are you killed your blue a lot faster than they did their red and will be long gone by the time they get there, meaning they wasted their time. If they start blue and invade your red, you see it. Free kill + red to either you or the laner(s, depending on which team your are on) when you both rush him. If they are super aggressive like Shaco or Lee you may want to ward golems too as those will get attacked. Wards wards wards, and some teamwork. Those will keep you from getting counterjungled pre-6. Post-6 your xp and gold tends to come from your lockdown ganks anyway and at that point you should have a couple points in HS meaning a couple HS+Smite can burst their buff creeps down rather fast pre-11.
Knowing when to toggle E is important too. If the enemy jungler is in their own jungle at 50%- having it on will alert them to your presence- But if you are also low, that will give you time to flee as well. If you are feeling confident against the enemy jungler, you can leave it off in their jungle so they become none the wiser and don't ping madly when they see the eyes above their head, instead wandering right into you where you can butcher them. If, however, you aren't sure, you should leave it on and maybe not even be there if you are worried enough.
Also, toggle it off when camping for a gank, then switch it on right as you run out. That way you don't give yourself away. Hearing the howl and seeing the eyes is an instant red alert for the target and a green light for everyone else.