A 74-year-old woman on a morning walk in San Francisco was grabbed and dragged into the home of a man, attacked by a pit bull, held captive for five hours and repeatedly raped before being left semi-conscious on the sidewalk, investigators said.

The San Francisco district attorney’s office is asking a judge this week to deny bail for the defendant, who has no criminal convictions, on grounds that his alleged crime is so horrific that he would be a danger to the public if allowed to go free, even temporarily.

Manuel Jesus Amador, 47, is being held in San Francisco County jail on suspicion of kidnapping and raping the woman. The Chronicle is withholding the victim’s name because of the nature of the crime.

“This case is particularly egregious,” District Attorney George Gascon and Assistant District Attorney Margaret Buitrago wrote in their petition to the Superior Court. The “defendant’s lack of criminal history should not dilute the severity of (his) conduct.”

At about 8 a.m. on May 10, the petition said, the victim was walking along Prague Street, a one-way street of neat bungalows in the city’s southeast corner near McLaren Park.

Amador grabbed the woman and pulled her up his driveway toward a side door of the house, according to the petition. As he allegedly forced her into the home, a pit bull that belonged to his roommate bit the victim’s ankle, left hip and feet.

Amador then locked the woman in a room, pushed her onto a bed and raped and sexually assaulted her repeatedly during four to five hours, according to the petition.

Amador admitted in an interview with police that he forcibly raped the woman, and that she lost consciousness for 30 minutes, the petition said. The victim told police that the man strangled her.

Eventually, Amador allegedly dressed the woman, dragged her back out to the street and left her barely conscious on the sidewalk.

A passerby noticed her and called 911. The victim was taken to San Francisco General Hospital.

A week later, on Friday, police booked Amador into county jail and charged him with rape by force, violence or threat of bodily injury, and kidnapping to commit another crime.

“The police did an excellent investigation that led to this arrest,” said Max Szabo, adding that the district attorney’s office provides a range of services to violent-crime victims, including counseling, paying medical bills, and providing a variety of compensation.

Three Prague Street neighbors told The Chronicle that they didn’t recognize Amador’s name or know of a vicious dog in the area. They had heard about the assault, however, and declined to give their names.

In arguing that Amador should be detained without bail, Gascon and Buitrago noted that crimes against elderly victims carry additional penalties under the law.

Their petition also cites a 2008 state victim’s rights bill known as Marsy’s Law, which requires judges to strongly consider “public safety and the safety of the victim” when reducing or denying bail.

A judge is expected to rule on bail at Amador’s arraignment, scheduled for 9 a.m. Thursday in Dept. 11 at 850 Bryant St., San Francisco.

Nanette Asimov and Lauren Hernandez are San Francisco Chronicle staff writers. Email: nasimov@sfchronicle.com and lauren.hernandez@sfchronicle.com Twitter: @NanetteAsimov and @LaurenPorFavor