Dr. Marks is a veterinary gastroenterologist and nutritionist who runs the Companion Animal Gastrointestinal Laboratory. Dr. Marks graduated from the University of Pretoria, South Africa, in 1986 and completed an internship in small animal medicine and surgery at the University of Missouri, Columbia in 1987. He completed a small animal residency program at the University of Florida and an oncology residency program at the University of California, Davis. Stan earned his PhD in nutrition from the University of California, Davis. He is currently on staff at U.C. Davis.

His research group have been characterizing enteric bacteria (Clostridial species, Campylobacter, Salmonella) and protozoa (Giardia, Cryptosporidium, Tritrichomonas foetus) associated with diarrhea in dogs and cats, and evaluating diagnostic tests and therapeutic strategies to eradicate the organisms. His group has also studied antimicrobial susceptibilities of Clostridium isolates to commonly utilized antimicrobial drugs, and evaluated the incidence of antimicrobial resistance genes in canine Clostridium perfringens isolates. The GI laboratory is fully equipped for performing aerobic and anaerobic microbiology, parasitology examinations, DNA extraction and purification, PCR, gel electrophoresis, and immunoassays. The laboratory has several ongoing studies evaluating the protozoan, Tritrichomonas foetus, an important cause of bovine infertility and abortion, and a recently characterized cause of chronic diarrhea in cats.