A 9-year-old girl from a rural area presents with migratory polyarthritis, fever, and a new-onset systolic murmur. Her antistreptolysin O titer is elevated at 640 Todd units, and echocardiography reveals mitral regurgitation. A diagnosis of Acute Rheumatic Fever is confirmed. After completing anti-inflammatory therapy for the acute episode, what is the most appropriate long-term management strategy to prevent recurrent attacks?