However, as those of us who are interested in the history of magia posthuma of the 18th Century know, van Swieten played an important role in trying to stop the belief in magia posthuma. In a recent book on vampire slayers, Slayers and their Vampires: A Cultural History of Killing the Dead by Bruce McClelland (University of Michigan Press, 2006), he is even called "the Lowlands slayer", and it is claimed that "in 1755, Maria Theresa dispatched Van Swieten to Hermersdorf, Moravia, to investigate the postmortem treatment of a certain 'Rosina Polackin'".
However, I can find no evidence of Van Swieten playing this active role in the investigation himself.
In his written remarks on the affair and on vampirism in general, Van Swieten only mentions that the Empress sent two other physicians to investigate this case of magia posthuma: the Professor of Anatomy, Johannes Gasser, and the court physician, Christian Wabst. As has been noted by vampire historians, this was the first time physicians of this calibre were sent to investigate a vampire case, which in itself is a testament to the progress of medicine during the few decades that had passed since the famous Serbian vampire cases. It was the report of Gasser and Wabst to Empress Maria Theresa that prompted Van Swieten to write about vampires and to recommend to the Empress that she should pass a law against digging up corpses and burning them because of beliefs in magia posthuma.
The role of Van Swieten and Maria Theresa in the history of the magia posthuma has only recently been recognized in vampire books in English, no doubt aided by Gábor Klaniczay's paper on The Decline of Witches and the Rise of Vampires under the Eighteenth-Century Habsburg Monarchy which has become a standard text in the historical study of witchcraft.