LOS ANGELES — Signs that pay TV’s pricey bundles of channels are beginning to unravel are starting to take a toll on major media companies.

Media stocks were hammered for a second day Thursday as Viacom’s underwhelming earnings gave investors another reason to sell. Earlier in the week, industry bellwether Disney trimmed a profit outlook because of more people cutting the cord on pay-TV packages.

Although there have long been signs that consumers love online video distributors such as Netflix, Hulu and Amazon, it’s the first time that signs of trouble for the traditional cable and satellite TV business have sent such a powerful shudder through the stock market.

Disney’s stock is down 14 percent since Tuesday, when it reported that it was trimming its forecast for TV subscriber-fee profit growth through next year because of subscriber losses at its flagship ESPN sports network.

Over two days, Viacom is down 22 percent, Time Warner is off 13 percent, CBS has shed 7 percent and Discovery Communications is down 11 percent. Twenty-First Century Fox is down nearly 13 percent.

“Questions around the death of pay TV are now front and center even if the size and pace of declines are likely being overstated by press and (Wall) Street commentary,” wrote analyst Michael Nathanson of MoffettNathanson Research.

Dish said Wednesday that its satellite TV subscriber losses accelerated in the quarter through June, falling 81,000 to 13.9 million, nearly double the loss of 44,000 a year ago.

Viacom Inc., which owns Comedy Central and Nickelodeon, reported Thursday that its profit fell in the most recent quarter. While that is largely because of a lack of big films this year, there have been questions about how it will handle a shift in the ways that people consume media. Its shares have fallen 41 percent this year.

“There is no question that our industry is in the midst of significant change,” Viacom CEO Philippe Dauman told investors Thursday.

Analysts say that popular channels like ESPN would likely survive any dramatic shift in consumer preference toward online channel packages such as Sling TV, which at $20 a month is far cheaper than traditional pay TV packages.

The question, wrote analyst Martin Pyykkonen of Rosenblatt Securities, is “whether the revenue substitution from skinnier bundles and/or a la carte channel plans will at least approximate the traditional cable bundle revenue over time.”