CHARLESTON, W.Va. -- One of the great animal welfare success stories of the last half-century is the end of dog overpopulation and wholesale euthanasia in many parts of the United States. After decades of effort, Americans embraced the message of responsible dog ownership in the 1970s and began spaying and neutering their pets, fencing their yards, and keeping their dogs on leashes.

In less than two generations, these practices have produced astounding results. We are caring for more than twice as many dogs today as in the 1970s, yet the number of dogs entering shelters in most of the country is just a fraction of what it was 40 years ago.

That's good news, but progress always carries with it the potential for unintended consequences. In this case, efforts at reducing dog overpopulation have been so successful that in parts of the country there are not enough dogs to meet local demand.

Shady pet dealers operating outside the regulated pet market, as well as retail rescue and shelter operations, are rapidly filling that vacuum in high-demand areas. These groups move dogs from distant states and foreign countries -- and have thereby created a largely unregulated industry that perpetuates the existence of deplorable kennels; a situation that regulated breeders and traditional shelters have worked for decades to eliminate. These practices also raise serious public health concerns.

This is a matter of particular interest in West Virginia and other states where animal shelters do not yet record and report information on the animals they handle. The lack of such information renders a huge part of the pet industry unaccountable, and poses serious problems to both animals and potential owners.

Fueled by wider access to transportation, instant communication, and lax or unenforced laws, moving dogs is faster and easier than ever. Hundreds of organizations -- both legitimate and illegal -- move dogs from the southern United States into the Northeast and other "high-demand" areas each year.

Last year in Colorado, for instance, shelters imported over 12,000 dogs from out of state. The Centers for Disease Control and Prevention estimate that nearly 200,000 dogs crossed into the United States from Mexico in 2006 alone.

Taking in thousands of dogs from distant states or foreign countries -- often without vaccinations or health certificates -- is asking for trouble. An infected dog can introduce foreign diseases and parasites -- and thereby endanger local pets, livestock, and even humans. It should be no surprise that cases of heartworm and canine brucellosis are rising in the northern United States, or that many of the recent cases of canine-strain rabies in this country have surfaced in dogs rescued from foreign countries.

There are social and ethical issues to consider, too. The unregulated movement of dogs obscures their origins. Many arise as "castoffs" from illegal, underground breeders -- and thus perpetuate their cruel and illegal operations. Others come from foreign countries where health and welfare standards are nonexistent or much lower than in the United States.

Sadly, importation by rescue and shelter groups -- though often well-intentioned -- displaces local homeless dogs without attacking the root of the problem. When an adorable puppy or small-breed dog from a distant land is adopted instead of a local, three-year-old lab or pit mix, one dog's life is simply traded for another.

Such an act does nothing to change the practices, policies, or culture of the imported dog's breeder, home state, or country. Instead, it enables irresponsible behavior and provides some of the worst kennels imaginable with an "overstock outlet" for the puppies they produce. Some importing shelters even refuse admittance to local dogs in favor of more "adoptable" ones from outside the area.

The solution? States must require that shelters and rescue groups transparently report data on the animals they take in -- and the animals they adopt out.

Virginia shelters have reported their shelter data in very detailed format for several years. West Virginia might benefit from reviewing its eastern neighbor's highly successful program.

Not long ago, the stated goal of most humane societies was to put themselves out of business by solving the dog overpopulation crisis. But today's practices create a perpetual pet supply chain for many shelters that allow them to function as unregulated pet stores.

In today's global marketplace, navigating pet-acquisition process is more confusing and than ever. Buyers and adopters need to beware.

Before obtaining a family dog, prospective owners must do their homework. They must carefully consider the source of their next pet.

Strand is director of the National Animal Interest Alliance, naiaonline.org.