The Lingvo 6.5 Dictionary gives us:

служащий, изучающий условия жизни неблагополучных семей и лиц, нуждающихся в материальной или моральной поддержке

Well, c a s e w o r k e r s, along with other social workers, are contained in the following excerpt from Britannica:
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Social philosophers and c a s e w o r k e r s generally regard family life as the ideal context for the promotion of social welfare. Family
welfare programs seek to preserve and strengthen the family unit through both economic assistance, where available, and personal
assistance with a variety of services. Personal assistance services include marriage counseling in most developed countries and in urban
centres of developing countries; maternal, prenatal, and infant care programs; family planning services; family-life education,
which promotes both the enrichment of family relationships and the improvement of home economics; "home-help" or "homemaker"
services providing household assistance to families burdened with chronic illness, handicaps, or other dependencies; and care of the
aged through such programs as in-home meal services, transportation, regular visitation, and reduced-cost medicines.
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Within the Russian realities (last word is used "a la Gorby":) we have a special category of social workers, called социальный работник. They mainly are giving help to old and alone persons, persons with deficiencies, those who are in need of help in view of mental disorders, etc.
In the capacity of an example, I can describe my neighbor, her name is Olga Ivanovna. She had a son with a serious deficiency from childhood (amiotonia), her son died after a car collision, and she then decided to help to others as a social worker. Her tasks were related to 2 persons: one was a 75 years old women with walk disability, so Olga went to shops to get alimentary, washed her, cleaned her flat, etc. The second person was a 43 years old son of an old women, a mathematician, which was disabled by hard form of sclerosis (he was disabled, could not move, etc.) So, Olga helped to this family by shopping, cleaning etc. For each case of that kind our District Departments for Social Aid (not Social Welfare!) are organizing social workers with specific programme of aid. It is very different if we compare with, eg., USA (I know it because I translated a special manual with the title CAREGIVING with detailed description of the role of caregivers, their bosses, etc.).
In Olga's "trudovaya knizhka" (labo(u)r book) her work is called СОЦИАЛЬНЫЙ РАБОТНИК.
So, I am sure you might use namely this term in translation into Russian if the difference between foreign and Russian Social Services mustn't be taken into account:). Otherwise, please use the term
(прикрепленный) работник службы социальной помощи (и/или адаптации),
which rather closely describes their role in USA.. Here пркрепленный serves to designate the word CASE.

Best regards,
Dr. Tagir S. Tagirov
KSU.