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Towards the end of 1853, Pierre van Beneden (1809-1894) showed that after oral administration of T. solium proglottids to the pig, Cysticercus cellulosae developed.
From a public health viewpoint, J. L. W. Thudicum (1829-1901), appointed by the Privy Council in 1864, carried out extensive inspections for ‘measly’ meat at London’s meat markets. Tapeworm infection was a major problem in British troops in nineteenth-century India, up to one-third of whom harboured T. saginata.
Recorded deaths from hydatid disease in England and Wales between 1837 and 1880 were always < 60 annually; sheep were, however, commonly affected. In the mid- and late nineteenth century, hydatid disease was common in Iceland and Australia (especially Victoria).
Diphyllobothrium latum was originally described by two Swiss physicians, Thadeus Dunus (Foster, 1965) and Felix Plater (15361614) of Basle, Switzerland.
The Liver Fluke (Fasciola Hepatica)
This trematode has been known to infect sheep from medieval times; it was in fact mentioned in a fourteenth century French text (Foster, 1965). The first illustration was by Redi (see above) in 1668. Van Leeuwenhoek (see below) was of the opinion that sheep swallowed the flukes in water, and that they then migrated into the biliary tract. Carl Linnaeus (1707-1778) named the parasite Fasciola hepatica but regarded it as a fresh-water leech that had been swallowed accidentally; not until 1808 did Rudolphi (see above) separate the flukes from the leeches, thus creating the class of trematodes (flat worms with ventral suckers), classification of which was based on the number of suckers—monostomes, distomes, etc. In the late eighteenth century, cercariae were clearly recognised, and in 1831, Karl Mehlis (Foster, 1965) visualised the hatching of a trematode with liberation of the ciliated miracidium; shortly afterwards (in 1837) Friedrich Creplin (Foster, 1965) visualised the ciliated miracidium of
F. hepatica. Following Steenstrup’s text of 1842 (see above) it seemed probable that a mollusc formed the intermediate host of this fluke; this was shown to be Limnea truncatula by David
Weinland (Foster, 1965) in 1874; although correct, this view was not immediately accepted. A. P. Thomas (Foster, 1965) at Oxford finally confirmed this fact, and published his results in the Journal of the Royal Agricultural Society for 1881. Simultaneously, Leuckart (see above), also in 1881, published observations that also showed this to be the case; in fact, his publication appeared 10 days before that of Thomas. Thus, the entire life-cycle of F. hepatica outside its definitive host had been worked out. In 1892, Adolpho Lutz (1855-1940), a pupil of Leuckart, demonstrated that herbivorous animals become infected by eating encysted worms and, to complete the story, in 1914 the Russian parasitologist Dimtry Sinitsin (1871-1937) demonstrated the path taken by the larval fluke from gut to liver—invading the peritoneal cavity in so doing (Foster, 1965).
In Egypt, disease caused by Schistosoma spp. was known from ancient times (see above, Cook, 1993a; Nunn, 1996). Endemic haematuria is mentioned several times in the medical papyri, and calcified eggs have been identified in Egyptian mummies dating from 1200 BC. The first Europeans known to be affected (suffering from haematuria) were soldiers of Napoleon’s stranded army in 1799-1801.
Theodore Bilharz (1825-1862), a German parasitologist, discovered the parasite, Distomum spp. responsible for Egyptian haematuria on 1 May 1851; some 30-40% of the local population was infected, more commonly men than women. Meanwhile, Cobbold (see above) had described an identical worm (subsequently named Schistosoma haematobium) in an ape dying in the gardens of the Zoological Society, London. John Harley (who lacked tropical experience) gave an account of his findings of a supposed new parasite, Distomum capensis, in a patient from South Africa, to the Royal Medical and Chirurgical Society, London, in January 1864.
In 1870, Cobbold obtained a supply of Schistosoma spp. eggs from a girl in Natal; he observed the hatching of the eggs (by no means the first person to do so), subsequently shown to
be S. haematobium (see below), and noted that they preferred fresh, brackish or salt water, and not urine, for this transformation. He was, however, unable to determine the intermediate host.
Prospero Sonsini (1835-1901), an Italian graduate of the University of Pisa working in Egypt during 1884-1885, again attempted to elucidate the life-cycle of S. haematobium; although he did not find a mollusc to support his observations, he claimed to have achieved success in Tunis in 1892; these results (in which he considered that human infection took place orally) were published in 1893. In 1894, G. S. Brock (Foster, 1965), working in the Transvaal and citing circumstantial evidence, suggested that human infection probably occurred not orally, but via intact skin whilst exposed to infected water. Meanwhile, Looss, working in Egypt, concluded that, in the absence of convincing evidence of an intermediate host, transmission must take place from man to man.