MANAGUA, Nicaragua--Defense Minister Humberto Ortega said yesterday that an aide who defected to the United States was a "little worm" who took with him several documents of questionable strategic value to the CIA.

Ortega said he expected the Reagan administration to "try to make a big show" out of the October 25 desertion of Maj. Roger Miranda Bengoechea, 34, who was chief supervisor of Ortega's staff.

The Defense Ministry had reported Friday that Miranda took $15,000 in government money when he left Nicaragua while the government was auditing the ministry's finances.

Ortega, brother of Nicaraguan President Daniel Ortega, said Miranda traveled October 25 to Mexico and turned himself over to the U.S. Embassy in Mexico City.

An Embassy spokesman in Mexico City, William Graves, said Tuesday night he had "no information about that."

The Defense Ministry said earlier Tuesday it did not know Miranda's whereabouts. In Washington, a Reagan administration official confirmed the defection but refused further comment.

Ortega, acknowledged Miranda's position would have given him access to "important information" that could by now be in the hands of the CIA.

But he attempted to minimize the value of anything taken by Miranda, saying he was certain Miranda "stupidly would have believed he was taking extremely useful, extremely important information."

For example, Ortega said, Miranda may have taken "photocopies of the military defense operations of the capital, of the air force, of the tank and artillery brigades."

"But when have we ever hidden from thousands of Nicaraguans the preparations for defense?" Ortega said.

Miranda recently would have had access to Ortega's own conversation with the high command about "strategy, doctrine, even where the war in Central America would go in case of a U.S. intervention," the defense minister said.

Ortega also said Miranda could have taken with him information on the Sandinistas' negotiations to obtain MIG fighter jets from the Soviet Union.

"When have we hidden from the world that we are seeking to acquire fighter jets to defend ourselves?" Ortega said, noting it was already known abroad that the Sandinistas have built an airfield at Puente Huete, about six miles north of Managua, for the aircraft.

Ortega disputed published reports, in the United States, quoting anonymous sources, that Miranda had been spying for the U.S. government for a long time before his defection.

Instead, Ortega said Miranda was "reached by and fell in love with the CIA" in the United States when he accompanied Nicaragua's first lady, Rosario Murillo, to California on September 5 to visit a demonstrator injured while protesting U.S. aid to the anti-Sandinista rebels, called Contras.