Systemic and cerebrospinal fluid immune and complement activation in Ugandan children and adolescents with long‐standing nodding syndrome: A case‐control study by Ogwang, R, Muhanguzi, D, Mwikali, K, Anguzu, R, Kubofcik, J, Nutman, TB, Taylor, M, Newton, CR, Vincent, A, Conroy, AL, Marsh, K, Idro, R