Lack of evidence for an antischistosomal activity of myrrh in experimental animals.

In a multicenter investigation of the potential antischistosomal activity of myrrh, a resin obtained from an African plant, different derivatives of the resin, including the commercial preparation Mirazid, were tested at different doses in mice and hamsters infected with Schistosoma mansoni. In mice infected with the Egyptian (CD) strain of S. mansoni, four of six groups treated with Mirazid did not show significant worm reduction, while the remaining groups showed significant but trivial reductions. In mice infected with the Puerto Rican (Mill Hill) strain of S. mansoni, a Mirazid solution was toxic for mice at high doses and produced modest or no worm reduction at lower doses. In hamsters and mice infected with Puerto Rican (NMRI) and Brazilian (LE) strains of S. mansoni and treated with the crude extract of myrrh in doses ranging from 180 to 10,000 mg/kg, no signs of antibilharzial activity were observed. Total tissue egg load and egg developmental stages were not affected by any of the treatment regimens. These results were in contrast to those obtained in praziquantel-treated animals in which 94% worm reduction and 100% egg reduction was observed. Based on the findings of this work, we cannot recommend the use of Mirazid in human cases of schistosomiasis.