1) Diseases come and go. Even if there was a disease last year, who is to say that it has not passed. Especially if nobody is willing to try.
2) Nobody knows for sure if this really is a disease that has affected the majority of these clams.
3) Nobody actually knows the source of the disease, if that is actually what it is.
Jumping on the bandwagon and blaming something without solid proof is how misinformation is spread. Misinformation helps nobody. Many of the deaths are simply due to improper collecting methods and terrible wholesaler conditions. Many of the less reputable wholesalers in LA mix all types of livestock together in nasty conditions. There is no doubt in my mind that dead and dying clams have been spotted in LA and that these vats may be disease infested. It is just too bad that many of these places are the same wholesalers that are selling bulk shipments into your LFS where nobody ever sees the conditions there are coming from. Then some unsuspecting customer drops on in his tank and it dies then blames the region the clams came from. This does not mean that clams from this reason are disease, especially when other wholesalers have these clams and they are healthy.
To my knowledge, the only way to determine the cause of death of a clam by the lay person. These are complicated and sensitive animals. Wild collecting compounds the many issues that can arise with clams, especially if they are collected poorly. Injuries from poorly collected specimens can take weeks to fully subdue the clams while others result in DOAs and immediate deaths at the wholesalers. Simply put, there are too many variables to intelligently attribute a cause of death at a wholesaler, though by human nature it is tempting to so.
If you however place a wild clam in a healthy tank with healthy clams and the result is the death of the other or all clams, this lends strong evidence towards a pathogen. For this reason, I am looking for current experience in this type of situation. The exact type of situation peterlin98 has setup and this situation only.
Obviously if all of these clams were diseased, our friend peter would have one heck of a mess on his hands. If you have never taken a look at his clam tank, I suggest you look up his tank thread and see exactly what I am talking about.