Primary care difficulties
To prevent and control the disease, the European health authorities recommend serologic screening of at-risk population groups. Because primary care is usually the first point of contact with the health care system for these infected patients, primary care physicians must know the main characteristics of schistosomiasis and be provided with the necessary means for its diagnosis and treatment. Yet physicians in health care centers face significant limitations when it comes to identifying and treating these patients.
Joaquín Salas, MD, director of the Tropical Medicine Unit at Poniente Hospital in El Ejido (Almería) and the document’s first author, explained these difficulties. “In Spain, we currently have the problem where the care of migrant patients varies greatly between the different autonomous communities – and even within an autonomous community, depending on geographical areas. This variability is caused, in large part, by the number of migrants that they serve. In places that have a large sub-Saharan migrant population, there are health centers that have gotten to a point where they’re able to request serologic testing for schistosomiasis. Unfortunately, in many instances, this testing is still only available to specialists. The objective of documents like ours is to make not only physicians but also managers aware of the importance of diagnosing and treating this disease as early as possible. Raising awareness is complicated, to a large extent, by the lack of knowledge about this disease – something that’s seen with many other ‘neglected diseases’ which primarily affect the poorest people in poor countries.”
Dr. Llanes explained that an autonomous community can individually approve serologic screenings and incorporate them into its primary care programs, regardless of whether they can be approved at the state level. He pointed out that this is what happened with Chagas disease. “To prevent vertical transmission, a protocol for pregnant women was implemented by several communities; it’s about to be approved on a national level.”
But there’s another obstacle to treating schistosomiasis. At the moment, the recommended antiparasitic treatments (e.g., praziquantel) are considered foreign medications. This makes it difficult for primary care physicians and specialists to have access to them. Even so, Dr. Salas believes “that in some places, pharmacy units facilitate things in such a way that physicians who prescribe those treatments are able to obtain them quite quickly and with less red tape. Be that as it may, ideally, the medication would be available in our country’s pharmacies, and it could be prescribed without these kinds of bureaucratic obstacles. The same thing happened with ivermectin, which is used, among other things, to treat strongyloidiasis, and which, for a few months now, has been on the market without restrictions. We hope the same will happen soon with praziquantel.”
Increasing risk
Although schistosomiasis is not endemic to Spain, various factors are contributing to an increase in the number of cases within its borders. Dr. Salas said that “without a doubt, climate change and global warming are influencing the expansion of vectors – mosquitoes, ticks, snails – that can transmit, to places like Europe, diseases referred to as ‘tropical.’ In the case of schistosomiasis, it’s been shown that Bulinus snails, intermediate hosts for Schistosoma, have adapted perfectly to Almería here in Spain and to the French island of Corsica, where winters are more and more temperate. But not only is this adaptation due to climate change, those same snails have acquired specific capabilities that allow them to better tolerate temperatures lower than those they initially had in the areas where they’re from in sub-Saharan Africa. To sum up, the colonization of new territories is due as much to a change in the climate – temperatures gradually rising – as to adaptations of the vectors themselves.”
Dr. Llanes noted that “the case involving the farmers in Almería shows that the vectors in Europe can, in fact, transmit the disease, basically because Schistosoma haematobium, human, can develop hybrids with schistosomes of cattle origin, Schistosoma bovis – hybrids that can be transmitted through European snails. This is what happened with the outbreak in Corsica, its vector being the freshwater snail Planorbarius metidjensis – as I said, shown to be implicated in Corsica’s significant outbreak, to which subsequent cases are still being traced. Obviously, the effects of climate change – temperatures rising and extreme meteorological phenomena increasing – on the infections transmitted by vectors are of the utmost importance and, together with the process of globalization, are what makes us consider these types of conditions to be emerging diseases or emerging infections.”
This article was translated from Univadis Spain. A version appeared on Medscape.com.