How likely is it for a toddler to get sepsis from a cat scratch?

Not likely. From kitten scratches one can get cat scratch fever- usually swollen lymph nodes and rarely more serious infection. A deep cat scratch that is not cleaned or tended too could maybe lead to sepsis...These are uncommon. Clean it, use neosporin and a band aid and if you have any concerns see your pediatrician. Hope this is not a stray cat as well..
Unlikely. However, cat scratches and bites can carry very serious infectious organisms. If there is redness, pain or swelling in the area seek medical attention immediately. Sepsis occurs when bacteria get into the blood and cause a dramatic immune response. Toddlers can have immature immune systems making them more likely to develop a serious infection.