Ocular sparganosis in Thailand.

Human sparganosis which was first reported by Patrick Manson in 1882 (Beaver, 1984) is a rare parasitic infection caused by the migrating plero­ cercoid larva or sparganum of a certain group of pseudophyllidean cestodes, namely in the genus Spirometra Mueller, 1937. The adults of these tapeworms are generally found in the intestinal lumen of domestic, feral, or wild canids and felids (Daly, 1982). Spargana, a term originally used to describe any unknown pseudophyllidean larvae, do not have adequate morphological charac­ teristics for differentiation. Therefore, they must be fed to a definitive host (dog or cat) to grow to adult worms which have morphological differen­ ces that can be used for taxonomic separation. This, however, has not been accomplished for spargana from most of human sparganoses. Thus, an opinion as to species of the sparganum was usually based on the general nature of the larva, knowledge of adult forms in hosts from that area, or previously reported sparganosis cases from that area. This leads to invalidity of species in many cases because certain forms are sometimes found in the same geographical regions, such as S. mansoni and S. mansonoides in North and South America (Mueller et ai, 1975) and/or knowledge of adult forms in those areas is inadequate. Fur­ thermore, the variability in adult worm morpho­ logy as well as lack of communication and agree­ ment among the ivestigators, has led to confusion about the classification of this group of tapeworms.