The theme of supersition is a key element of this novel in the way that Jim is shown to be subject to the belief in superstition and how it impacts on his life. In Chapter Ten we have but one example of this, as Huck mocks Jim for the way that he believes that talking about the dead man they discovered would bring bad luck. Note what Huck says to him after they discovered some money from the clothes they took from the dead man:
No you think it's bad luck. But what did you say when I fetched in the snake-skin that I found on teh top of the ridge day before yesterday? You said it was the worst bad luck in the world to touch a snake-skin with my hands. Well, here's your bad luck! We've raked in all this truck and eight dollars besides. I wish we could have some bad luck like this every day, Jim.
However, Jim maintains that bad luck is "a-comin'," as is shown by the subsequent snakebite that Jim suffers. Clearly Huck is initially sceptical about Jim's supersition, but as the novel progresses, Huck gradually is shown to gain in respect for Jim and his deep understanding of the world and nature that has so much to teach Huck. Thus, who knows if Jim's bite was the result of superstition? What is important to ask is how supersition is used in the novel and in particular in the maturity of Huck as he comes to find a deep-seated respect for somebody that he initially regards as being "under" him because of the colour of his skin.
Considering The Adventures of Huckleberry Finn is full of satire and superstitions, the episode of Jim being bit by a snake and working to cure himself is most definitely a result of Huck and Jim's beliefs of such things. One of the main characteristics of Huck is his education in superstitions and the fact that he is in the Deep South with people who live their lives based on following how to survive under such conditions. If you follow superstitions throughout the book from the beginning to the end, you will find the Huck and Jim are two characters that will educate each other and protect each other from these lifestyle choices.
If you read the article attached this should help with deciphering and finding some of the superstitions Huck and Jim talk about and the coinciding chapters. Good luck!