Prospective rheumatological study of muscle and joint symptoms during Trichinella nelsoni infection

One hundred and fifty patients were assessed during an outbreak of Trichinella infection in Northern Italy. The aetiological agent was proved to be T. nelsoni. A detailed prospective rheumatological study was carried out. Myalgia was observed in 88 per cent, muscle weakness in 60 per cent, myositis in 62 per cent and arthralgia in 20 per cent of the patients. The arthralgia score was strictly related to myalgias-myositis. The degree of myositis correlated with the degree of hypereosinophilia. Muscle damage in tissue samples was often observed in areas where eosinophils were the major cell population infiltrating the tissue. No relationship was seen between IgG antibody titers against Trichinella or IgE levels and clinical manifestations. Steroids, thiabendazole or mebendazole were not administered. We observed no CNS or heart involvement nor did we see vasculitis. After six months 18 patients, with the highest degree of myositis and hypereosinophilia had all improved. None showed abnormalities in laboratory tests and only four were still complaining of muscle aches. T. nelsoni-related infection appears to induce musculoskeletal symptoms in the majority of patients, but the long term course and prognosis is favourable.