Volume 29, Issue 1
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



A wealth of epidemiological information available on bilharziasis in Puerto Rico made it possible to trace historical trends in the distribution of the disease. From a few scattered foci present in the early 20th century, the extent and intensity of the disease increased on the south coast after construction of sugar irrigation systems in 1914. After 1953 this major endemic area was brought under control while a new endemic area was developing in the eastern portion of the island, due to creation of rural communities known as “parcelas.” The increased transmission caused by the parcelas had been counteracted in other parts of the island after the Second World War by the widespread contruction of water supply systems and by filling of wetlands and channelization of streams on the growing suburban fringes of the major cities. Finally, an expanded snail control program of the 1970s covered most of the newer foci created by the parcelas, except for a small area on the north coast, east of San Juan. By 1976 only about 100,000 persons carried the parasite, mostly children with asymptomatic infections. They lived primarily in the northeastern municipalities, as well as scattered remnants throughout the classical endemic areas. Complete control of the disease could be accomplished in a few years, finally breaking the connection between sugar and snails in Puerto Rico.


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