The human Infected variant is the Loups-Garoux and in Runner's Companion they are described thusly:

"The brutal transformation costs most loup-garou their intelligence, leaving them feral and animal-like."

Does that mean ALL the time or simply during the peak of its 28 day cycle? Can lopus-garoux at least communicate with others when they aren't peaking?

The book didnt say if loups-garoux were part of the Infected population that had been recognized and granted limited recognition.

Like all brain-damage/mental trauma brought on by HMHVV, the issue is largely left up to the gamemaster's discretion rather than set in stone by mechanics.

Ghouls are intelligent, so I don't think HMHVV destroys all intelligence necessarily. On some cases, sure, but not on all. Like goblinization causes brain damage, but doesn't destroy all intelligence.

They only lose 1 point of Logic, but for a typical person (Int 3), that means becoming Underdeveloped. Seeing as how Loup-Garou only lose 1 point of Int as well, I'd say that they usually are a little slow intellectually, and during their period they become near-feral.

After reading the description of the Loup-Garou I'm starting to think that they have a feral intelligence all the time. It just happens that during a full moon that they go berserk and the full extent of their transformation becomes apparent. In the Critters book it states that the human loses their intelligence but gains animal cunning (that would account for only a -1 to Int). It further goes on to say that 4-6 days out of every 28 days it becomes a raving monster. I would treat a low cycle loup-garou as a wild animal (like a wolf), and the high cycle loup-garou as a rabid animal.

Except that a Loup-Garou does not loose Sentience, meaning it is never a 'wild animal'.

A Loup-Garou is basically a Human with slightly lower than norm cognitive function, still far above a level of retardation or non-sentience.