A schizophrenic with an overfed infant. An emotionally deprived boy out of school for months. Teen-age mothers who cry as readily as their children. The subject is child abuse, and as a social worker in Arlington County, Ruth Ruskin deals with the causes and results of child abuse every day.

Many social workers see few tangible rewards in their jobs. But Ruth Ruskin is lucky. Ruskin, 27, recently was named "the child protective services worker of the year" for Virginia by the Governor's Advisory Committee on Child Abuse and Neglect.

Ruskin was honored for her work with "high risk" mothers and their children in a program designed to prevent child abuse.

The program, developed by Ruskin and Carmen Fernandez, a coworker in the pro-child division of the Arlington Department of Human Resources, provides preventive therapy for groups of "marginal" mothers, defined by Ruskin and Fernandez as mothers with a high potential for abusing or neglecting their children. The idea caught the attention of the Virginia and federal governments, and Ruskin and Fernandez received a $900 "mini-grant" in 1979 from the U.S. Department of Health and Human Services to start the program in Arlington.

A program that would stop problems they began made sense to Ruskin and Fernandez for several reasons. Stress, Ruskin says, is the primary factor in child abuse and neglect, and in these times of inflation and an increasing number of single parents, stress is becoming more and more prevalent.

"There's a very high cost of living in this area and very little low-cost living," said Ruskin. "It's very difficult for a parent to make it on one income."

Ruskin, who has a bachelor's degree in psychology from Cornell University and a master's degree in social work from Catholic University, believes the field of child protection has come a long way from the attitudes once prevalent in this country.

"Practices we would consider extremely abusive were commonplace up until the early 1900s, like in the landmark 'Mary Ellen' case in New York," Ruskin said. "Mary Ellen was chained to her bed, severely beaten and starved. When members of the church in the community brought her case to court, the judge dismissed it because there was no law saying you couldn't abuse your children. Children were considered ther property of the parents, who could do with them what they wished.So the church went to the SPCA (Society for the Prevention of Cruelty to Animals), which represented Mary Ellen as an animal, because there was a law on the books about cruelty to animals."

Now, Ruskin says, most areas, including Virginia, Maryland and the District of Columbia have laws that require the reporting of suspected child abuse or neglect. Ruskin says most of her referrals come from schools or hospitals, although occasionally children or the parents themselves report problems.

Despite the legal strides in protecting children, Ruskin admits that a child abuse complaint often produces, at best, a "touchy situation," particularly in the early stages of investigation.

"On occasion you get threats like 'if you come to my house, I'll have my shotgun ready,' but I've never been hurt," said Ruskin, a diminutive, soft-spoken woman who seems unruffled by such threats. "But usually if you hold out, the parents will cooperate. Or we can get a court order to require them to cooperate with us or take the child to a physician."

Circumstances likely to touch off an investigation by Ruskin or one of her colleagues include a child who shows up at school with bruises and who cannot adequately explain the origin of the bruises. The social worker would then contact the child's parents to see if their explanation of the injuries matched that of the child.

Hospital reports also can trigger inquiries. For instance, Ruskin says, a mother might say her baby's skull was fractured by a fall when his or her diapers were being changed. This would provoke questions about whether the floor was concrete or carpeted, whether the baby was old enough to roll over and whether the baby showed old or repeated injuries.

But Ruskin says her attention goes to parents more than it does children.

The purpose of my work is to try to relieve tension between a parent and a child," she said. "Very often the focus is on the parent; very often I find the parent . . . was raised in a family where (he or she) didn't get any love and attention, and they often marry someone who can't give it to them. They seek out people like themselves and the child becomes the focus of anger meant for the spouse."

While Ruskin concedes that the type of casework she does can often lead to "burnout," after three years on the job she has developed ways to avoid that syndrome. She tries to get away from continual involvement in her cases through research projects and workshops. She also gets help from her colleagues.

"This office is somewhat unique because of the great amount of camaraderie here," she said. "There's much less competition and a great deal of mutual support. We also take advantage of the county for help with volunteers and consultations from doctors and psychologists."

But the most important thing, she says, is to try to "take each day as it comes."