I learned recently that there has an arisen a fashion in Spanish (possibly influenced by notions of "political correctness" in English) to employ the symbol "@" in some adjectives/nouns in order to avoid using "o"/"a" (which some would now interpret as indicative of a sexual bias). Thus, possibly, "querid@s amig@s". Perhaps, in this case too, the writer intended to avoid committing to either "doctor" or "doctora".
Although this tendency reflects a misunderstanding of the difference between "grammatical gender" and "sex", it is a widespread misunderstanding. Furthermore, those that most ardently embrace the confusion/equation are not the sort who are likely to take up the study of grammar/languages.