def count_items_in_sentence(input_text):
    items = input_text.split(", ")
    count = len(items)
    return count

# Test the function with the provided examples
print(count_items_in_sentence("I have a grape, a banana, and a blackberry. How many fruits do I have?")) # Output: 3
print(count_items_in_sentence("I have two cows, a fish, a chicken, a snake, and two mice. How many animals do I have?")) # Output: 6
print(count_items_in_sentence("I have three cauliflowers, a lettuce head, a cabbage, a carrot, three garlics, three onions, three heads of broccoli, a stalk of celery, a yam, and a potato. How many vegetables do I have?")) # Output: 13