The need to look for more than just malaria
I was just reading a comment in the new Journal of the American Society of Tropical Medicine and Hygiene “After Malaria is controlled, what next?”
Fortunately for all of our jobs, there is little to worry about. Malaria, as a complex environmental/political/economic public health problem, won’t be controlled anytime soon. As there’s no indication that many sub-Saharan countries will effectively ameliorate their political problems and also no sign that, despite the “Rising Africa” narrative, African countries will develop in such a way that economic rewards will trickle down to the poorest of the poor, malaria transmission will continue unabated. This is a horribly unfortunate outcome for the people, particularly small children, who have to live with malaria in their daily lives.
In all of the places it occurs, malaria is merely a symptom of a greater political and economic failure.
Indeed, we really know less about the causes of suffering and death in the tropics than many believe. Even vital statistics of birth and death are unrecorded in many areas of the world, much less the accurate causes of disease and death. Some diagnoses, such as malaria, dengue fever, and typhoid fever, are often ascribed to patients’ illnesses without laboratory confirmation. Under the shadow of the umbrella of these diagnoses, other diseases are lurking. I have found significant incidences of spotted fever and typhus group rickettsioses and ehrlichiosis among series of diagnostic samples of patients suspected to have malaria, typhoid, and dengue in tropical geographic locations, where these rickettsial and ehrlichial diseases were previously not even considered by physicians to exist.4–8 Control of malaria or dengue would reveal the presence and magnitude of other currently hidden diseases and stimulate studies to identify the etiologic agents.
This is the problem with our public health fascination with malaria. We are missing all of the other pathogens and conditions which case untold suffering in the poorest and most isolated communities. It can’t be the case that malaria acts in a box. In fact, it could be the case, that multiple pathogens coordinate their efforts to extract as many human biological and behavioral resources as possible to obtain maximum opportunities for reproduction and sustenance. A public health system only designed to look for and treat a limited window of diseases misses the opportunity to disrupt what is probably a vast ecological complex.
First, we have a problem of poor diagnostics. Facilities traditionally treat most fevers presumptively as malaria, dispensing drugs appropriate to that condition. However, conditions like dengue fever exhibit similar symptoms. While is it extremely likely that dengue is all over the African continent, particularly in urban areas, there is little ability to identify true dengue cases in the public health sector, and thus, in addition to mistreating patients, the extent of the disease burden is unknown. We cannot tackle large public health issues without proper data.
Second, we have the problem of all of the “known unknowns,” that is, we know for a fact that there’s more out there than we have data for but we also know (or at least I do) that there is a greater disease ecology out there. We know that many pathogens interact with one another for their mutual advantage or to haplessly effect significantly worse outcomes. The awful synergy of HIV and TB is just one example.
OK, I’m going to go and deal with my own pathogenic tenant which I think I’ve identified as an enteric pathogen of the genus Pseudomonas, which might have taken hold opportunistically through an influenza infection. This is complete speculation, however. Data quality issues prevent a reliable diagnosis!
Did pathogens influence the course of human development?
According to the “pathogen stress theory of values,” the evolutionary case that Thornhill and his colleagues have put forward, our behavioral immune systems—our group responses to local disease threats—play a decisive role in shaping our various political systems, religions, and shared moral views.
If they are right, Thornhill and his colleagues may be on their way to unlocking some of the most stubborn mysteries of human behavior. Their theory may help explain why authoritarian governments tend to persist in certain latitudes while democracies rise in others; why some cultures are xenophobic and others are relatively open to strangers; why certain peoples value equality and individuality while others prize hierarchical structures and strict adherence to tradition. What’s more, their work may offer a clear insight into how societies change.
This is a reasonable view, and something I’ve long observed from working on infectious diseases in developing countries. The developmental trajectory of a country is influenced by the deliberate avoidance of illness. An example can be seen in the locations of African cities. Many African administrative capitals are located on isolated, cool hilltops, far away from rivers and lakes. Colonialists would intentionally set up shop in areas where they were unlikely to encounter malaria.
Developmentally, this has had major implications for trade within Africa. European cities are often placed along water ways amenable to domestic European trade. The lack of trade between African countries is one of the reasons the continent has developed so poorly. This is the direct result of not only colonial priorities of resource extraction to Europe, but also the unfortunate placement of economic centers in response to malaria.
Certainly, the nature of cities themselves have much to do with the control of infectious diseases. Public works often involve the management of sewage waste and the delivery of clean water. Thornhill might suggest that the development of democracy, citizen involvement and taxation to pay for urban improvements are in direct response to enteric diseases.
However, while it is interesting to try to apply this view, it can be taken to the extreme:
Fincher (a graduate student of Thornhill) suspected that many behaviors in collectivist cultures might be masks for behavioral immune responses. To take one key example, collectivist cultures tend to be both more xenophobic and more ethnocentric than individualist cultures. Keeping strangers away might be a valuable defense against foreign pathogens, Fincher thought. And a strong preference for in-group mating might help maintain a community’s hereditary immunities to local disease strains. To test his hypothesis, Fincher set out to see whether places with heavier disease loads also tended toward these sorts of collectivist values.
I’m not sure it’s that easy to boil down political differences between Asia and Europe to a need to manage infectious disease. Certainly, Sweden is more collectivist than England, but I wouldn’t say that their infectious disease profiles are all that different.
Worse yet, if taken to the extreme, this “hunt for significance” will provide one with evidence to support any crazy theory at all. Pathogens exist wherever humans do. Moreover, we risk attributing the contribution of pathogens to human development based on current conditions, assuming that the present is deterministically preordained centuries ago. Until very recently, nearly the entire world was at risk for malaria, but despite this, various societies have embarked on different social and political trajectories.
The biggest problem I have with the theory is in its basic in rational theory. It assumes that humans are making rational choices based on pathogen threats, when we know, and particularly those of us who work in the tropics, that humans often have poor conceptions of disease transmission and causes of illness. At times, despite very obvious threate, humans will act in manners which exacerbate that threat. The history of enteric disease is filled with tales of ignorance and folly.
If we are going to subscribe to a rational model of political and social development which includes pathogens, then we have to also address first, the ability of pathogens to hijack human behavior to create new opportunities for replication and survival and second, that social changes can exacerbate the worst effects of infection. For the first point, I would look to the development of international trade systems which allow pathogens such as influenza to move around the world quickly, increasing opportunities for mutation to avoid immune responses. For the second I would point to polio, a disease which becomes a problem on after the introduction of water sanitation practices.
Thornhill’s ideas are interesting, and certainly provide good material for the popular press and BBQ conversation, but they require that the reader suspend too much consideration of the details of the complex history of human social and political development. Taken with restraint, as in the example of the locations of African cities, they can provide interesting insights into how current conditions are impacted by past pathogenic threats.