Heat olive oil in a large pot over medium-high heat. Add turkey, onions and garlic. Cook and stir until turkey is no longer pink and onions begin to soften, about 5 minutes, breaking up any large pices of turkey as it's cooking.
Add green peppers, celery, carrots, chili powder, cumin, oregano and cayenne pepper. Cook for one minute. Add chicken broth, tomatoes with their liquid and pumpkin. Mix well. Bring mixture to a boil. Reduce heat to low, cover and simmer for 20 minutes.
Stir in beans and simmer uncovered for 10 more minutes. Season with salt and pepper. Remove from heat and stir in cilantro and lime juice.
Garnish with a dollop of sour cream, a few slices of avacado and a sprinkling of cilantro if desired.