Purity, impurity, infectious diseases

The cover story of the December issue of the International Journal of Environmental Research and Public Health is devoted to a girl, Jennifer Worrall, and Jasmin, her beloved rat.  “In 2012 in the United Kingdom, a number of people caught Seoul hantavirus from their pet rats –  explains the editor - Pet rat owners were warned about the potential risk their pets posed; however, they did not want to change the way they interacted with them. To understand why, we interviewed pet rat owners to explore how they made sense of the disease and the risk it posed.”

The paper - authored by a multidisciplinary team, including veterinary and public health doctors, and psychologists, at Liverpool University – reports a study based on seven in-depth interviews with pet rat owners and breeders in England. The goal was “to elicit an understanding of disease and risk in human populations in contact with pet and wild rats.”   Researchers identified four themes “relevant to the design of public health messages.” They called the first theme “A Tale of Two Rats,” according to this theme pet and wild rats are no longer perceived as the same species by rat owners. Of course, rat owners do not context biological classifications, and they are rationally aware that pet and wild rats are the same animal, yet, emotionally and practically speaking, they consider pet rats as though they were an autonomous species.  The second theme is the “hierarchy of purity”. Researcher discovered that pet rat owners create their own hierarchy of purity among rats, being wild rats at one extreme (impurity) and their own pet at the other extreme (purity), in between all other rats, ranging from rescued rats (e.g., saved from labs) to pet shop rats. The most a rat is perceived “pure,” the less the animal is object of hygienic and preventative measure, irrespective of any public health authority recommendation. The third theme is “bounded purity.” Purity and impurity appear to be strictly bounded to home borders. Events affecting pet rats, originated in, and happening inside of, the home do not threaten their purity, while purity is threatened by any event occurring outside of the home, and affecting pets. Impurity is associated to out-of-place situations.  The fourth theme is “The Divergent Worlds of Pet Rat Owners and Health Officials.” It concerns the two different models of diseases shared respectively by pet rat owners and health officials. While the latter see the world through the lens of the standard medico-scientific model of infectious disease, the former perceive their own world as a separate space, where standard rules do not apply.  Each pet rat owner believes his own case to be an exception, that cannot be captured by the standard medical model. 

Why – researchers ask themselves and the reader – were these four themes so successful in preventing an effective response to the actual threat to human health posed by Seoul virus? Because – they answer – the biomedical model of disease was problematic for this virus, which can infect rats and human without causing any symptom of infection and disease, e.g. according to Public Health England “one third of pet rat owners tested were seropositive to the virus; however, not these individuals actually experienced the disease by becoming ill.”   Authors conclude “Seoul virus (…) is ambiguous, composite, in-between (…) it is an anomaly. Rather than responding negatively to this anomaly, by ignoring the risk it poses, owners have responded more positively by creating a new reality in which Seoul virus has a place: a ‘hierarchy of purity’”. There are several reasons of interest in this paper. Two of them are worth mentioning, they both regard “purity.”  

The first reason of interest concerns the lesson for public health communication. The couple purity /impurity is in the limelight of contemporary scholarly studies on public perception  of infectious diseases and the origin of  vaccination hesitancy.  Scholarly speaking, considerations on purity and impurity should play a pivotal role in health communication. Unfortunately, professional communicators often lack the necessary scholarship, historical depth, and perspective. So, they fail to grasp crucial cultural nuances. The very notion of contagion – that today we take for granted belonging to the medico-scientific register –  originates from the couple purity /impurity and it is as ancient as human civilization itself. Assuming that less than two centuries of germ theory have modified the collective mindset, is naïve and misleading. Conceptions about purity and impurity return repeatedly, only a bit masked by pseudoscientific languages, and they still rule public perception of communicable diseases.   

The second reason of interest concerns a common misunderstanding. Most scholars, who have recently discussed the issue purity/impurity in relation to infectious diseases and vaccination, have labelled it as a “moral” issue. This is a methodological mistake, which prevents understanding many nuances of the couple purity/impurity, which originates from deep, collective, fantasies, much wider than ethics.  Actually the opposition between purity and impurity provides a valuable interpretative framework for a range of social phenomena, including  attitudes towards GMO foods, xenophobia, and policy preferences.  The Liverpool team deserves the full credit for avoiding such a mistake as well as the easy solution to turn “everything into ethics.”  

When research is aware of complexity and properly done, one could learn a lot even from a young lady and her pet rat, which is, maybe, the most important lesson taught by this paper.