Cunningham, A., & Williams, P. (1992). The laboratory revolution in med-icine. Cambridge, UK: Cambridge University Press.Ewald, P. W. (1994). The evolution of infectious disease. New York😮xford University Press.Grmek, M. (1989). Diseases in the ancient Greek world (L. Muellner &M. Muellner,Trans.). Baltimore: Johns Hopkins University Press.Kiple, K. (1993). The Cambridge world history of human disease. Cam-bridge, UK: Cambridge University Press.McNeill,W. H. (1998). Plagues and peoples (2nd ed). New York: AnchorBooks.Diseases, AnimalEvery disease that has caused epidemics and changedthe philosophical traditions of societies throughouthuman history has originated in nonhuman animals and“jumped the species barrier” into humans. There is nomeaningful separation between animal and human dis-eases when discussing the impact of disease on humanhistory.It is important to emphasize that because humans aremammals, diseases found in other nonhuman animals,especially other mammals, often cross readily intohumans.The most important diseases are infectious andhighly contagious. Noncontagious diseases have had lit-tle or no impact on history. By deﬁnition, infectious dis-eases are capable of being spread rapidly from infected tohealthy individuals. Infected individuals either die orrecover fully within a short period of time; those indi-viduals who recover typically acquire immunity againstfurther infection by the same illness.The numerically greatest single documented epidemicin human history was an inﬂuenza outbreak that killed anestimated 40 million people at the end of World War I.The epidemic having the greatest recorded impact wasthe bubonic plague that killed over 25 percent of the peo-ple in western Europe in the mid-fourteenth century.Despite a lack of documentation, however, the epidemicswith the greatest overall impact both on human popula-tions and history were the series of epidemics that spreadthrough the Americas shortly after contact with Euro-peans and their domestic animals. These epidemicsspread through populations previously unexposed toepidemics, typically causing 90–95 percent mortality.Overall, these diseases may have killed as many as 100million people in the Americas.Prominent examples of infectious diseases that havecrossed from other animals into humans include small-pox, cholera, tuberculosis, bubonic plague, and inﬂuenza.Although AIDS represents a major potential health prob-lem in the modern world, it is contagious, but neitherinfectious nor acute. In recent years there have been pan-ics over other animal diseases such as hoof and mouthdisease, Hanta virus, and so-called mad-cow disease,which may not be a disease in the usual sense at all.Thesepathological conditions are trivial compared with theimpact of the other diseases listed, yet they have receivedmore publicity, perhaps because of media-inspired fearand ignorance, combined with the fact that most peopledo not understand how various diseases are transmitted.Most infectious animal diseases that jump to humansare caused by bacteria and viruses whose small size ren-ders them highly volatile and transmissible as aerosols,hence more likely to be transmitted from one individualto another, which is the basis of contagion. A few dis-eases, such as malaria and sleeping sickness, are causedby protistans, single-celled eukaryotic organisms that aremuch larger than bacteria or viruses. The larger size ofprotistans means they cannot be transmitted as aerosolsand hence are transmitted primarily by injection, forexample, through insect bites, rendering them much lessinfectious.Most infectious disease organisms co-evolve in inter-actions with other nonhuman species.These nonhumanspecies have evolved an immune response to the disease-causing organisms, so they are not serious threats eitherto health or population numbers in their original hostspecies.What renders most of infectious diseases so viru-lent in human populations is that when ﬁrst exposed, hu-mans have no evolved immune response to these patho-gens; for example, smallpox is related to bovine pox,which causes minor problems in cattle but is often fatal inits mutated form in humans. Similarly, the AIDS virus isclosely related to a viral infection that occurs in Africandiseases, animal 551
primates, where it only causes mild inﬂuenza-like symp-toms. Other examples include measles, which is closelyrelated to the ungulate disease rinderpest; tuberculosis,which is closely related to a similar disease in cattle; andinﬂuenza, which is actually a complex of viral diseasesderived repeatedly from similar pathogens occurring inpigs (swine ﬂu) and birds such as ducks and chickens.Contagious diseases that manage to cross the speciesbarrier from nonhumans into humans have been a majorfactor shaping the history of Europe and Asia. A majordifference between Europe and Asia as contrasted withthe Americas and Africa is that Eurasian cultures domes-ticated and lived in close association with the animalspecies that served as the original hosts of these diseases.Domestication of ungulates, especially cattle and swine,set up scenarios whereby humans living on intimateterms with these animals were continually exposed to awide range of epidemic diseases, which already afﬂicted552 berkshire encyclopedia of world historythe ungulate populations as minor problems. These dis-eases thrived particularly well in the high densities atwhich human societies kept cattle and pigs. Farmers aresedentary, living among their own sewage and that of thedomestic animals with whom they live in an intimate andsymbiotic fashion. In many agrarian societies, farmers tra-ditionally took cattle and pigs into their homes at night,both for warmth and to protect their livestock from pred-ators. These conditions both prolong exposure and in-crease the likelihood of transmission of bacterial and viralpathogens.Agriculture sustains much higher human densitiesthan the hunting-gathering lifestyles that agriculturereplaced. The large concentrations of humans resultingfrom increased urbanization provided fertile ground forthe rapid spread of infectious diseases that originated inother species. Only within the last century did Europeancities achieve self-sustaining populations, because soAnimal Diseases and NationalismAnimal diseases can have enormous economic conse-quences. For this reason, modern nation-states arereluctant to accept blame for the disease originating intheir territory.This text extract concerns a cattle plagueor Rinderpest that spread across Britain in the 1860sand shows the reluctance of the investigators to traceit to British soil.If, for example, the Cattle Plague has spontaneouslyoriginated in this country from the way in which ourcattle have been housed or fed, we might hope toshow how such conditions act; and how they can beremoved. If it originates in some wave of poisonousair which spreads over the country, and, after havinga regular period of ﬂow has a succeeding period ofebb and disappearance, we must be content withbearing what no care can foresee and no art control.If, however, Cattle Plague has been introduced amongour herds by the arrival from infected places of cattlealready diseased, and if it spreads entirely by conta-gion, it is obvious that means may lie used, which, ifapplied strictly and carefully, will be effectual, to pre-vent its return.. . .We have been able to ﬁnd no evidence of aspontaneous origin in England. The ﬁrst knowncases were all in animals collected from differentparts of England and Holland, brought to the Met-ropolitan Market on one particular day, the 19th ofJune; they were purchased by different dairymen,and then taken to ﬁve sheds in different parts of Lon-don, namely, in Islington, Hackney, Lambeth, andPaddington. As there was no Cattle Plague in theparts of England whence these cattle came, andnone in the sheds to which they were taken, and asthe length of the incubation period, as well as theabsence of any probable cause, negatives the idea ofa spontaneous origination simultaneously in theseﬁve sheds, the conclusion becomes almost irre-sistible that the cattle must have caught the diseasewhilst standing for sale in the Metropolitan Market.Now this market is certainly the most likely place inEngland for Cattle Plague to be brought to fromabroad, and if not the most unlikely, at any rate anunlikely place for it to spring up in.Source: Third report of the commissioners appointed to inquire into the origin and nature&C., of the cattle plague; with an appendix. Presented to both Houses of Parliament bycommand of Her Majesty. (1866). Retrieved from medhist.ac.uk/text/browse/mesh/C0003047L0003047.html
many city dwellers died from disease that a constant im-migration from rural areas was required to sustain urbanareas.The Black Death and Its EffectsDevelopment of world trade routes rapidly increased thedispersal rate of epidemic diseases. By Roman times thepopulations of Europe, Asia and North Africa hadbecome a giant breeding ground for disease organismsthat originated in domestic livestock. Smallpox reachedRome in the second century CE, killing millions ofRoman citizens as the Plague of Antoninus.The animal-borne disease with the most profound impact on thecourse of history in Europe and Asia was bubonic plague.Spread by ﬂeas that pick up the plague bacillus from thefur-bearing mammals that are their normal hosts, plagueﬁrst appeared in Europe as the Plague of Justinian in542–543 CE.The most devastating impact of the plague(the Black Death), however, occurred in fourteenth-century continental Europe where it killed as many as 25million people. In the British Isles alone, plague killednearly 1.5 million people (25–40 percent of the totalpopulation).The major vector for the major outbreak ofplague appears to have been furs brought from low-population-density areas in central Asia with the intensi-ﬁed trafﬁc on trade routes to China in the mid-fourteenthcentury.One important, often unappreciated, consequence ofthe fourteenth-century plague was its profound impact onEuropean philosophy and science.The prevailing world-view in Europe prior to the mid-fourteenth century wasmythic and symbolic, rooted in an idea of cyclical time,placing far more emphasis on links between human andnonhuman aspects of the world than did the worldviewsthat arose after the Black Death.When plague arrived and began to have devastatingimpact on local populations, the knowledge base andtechniques of this older philosophical tradition werepressed into service, including prayer, medicine based onsympathetic magic, and scapegoating (e.g., witch burn-ing). None of these methods proved effective, and the lackof ability to deal with the resulting death and devastationcreated both widespread panic and subsequent culture-wide depression.The impact of massive, inexplicable lossof life on a society cannot be overestimated. Belief in spir-itual traditions and ways of understanding how theworld works are crushed, leading to a sense of spiritualdesolation.The experience of the plague, described by some his-torians as the “greatest biological-environmental event inhistory” and the “equivalent of nuclear holocaust” by oth-ers, forced western Europe to develop a new way oforganizing its perception of reality. Within Christianitythe plague led to loss of faith in a benevolent, heedfulCreator, leading to persecution and scapegoating of“heretics,” eventually leading to the beginnings of Protes-tantism and its images of a vengeful, wrathful God.From a more scholarly perspective, response to theplague experience may well have led to the developmentof an intellectual tradition that separated mind frombody, objective from subjective, and human from nature.In turn, this intellectual tradition can be linked to thebeginnings of the Renaissance and development of thewestern European “rationalist” scientiﬁc tradition, ulti-mately generating Cartesian Dualism, the machinemodel/metaphor as a way of understanding nonhumanlife, and the Baconian-Newtonian worldview. Thus, thephilosophical and spiritual impact of plague led directlyto the “modern” rationalist approach in which experi-mentation and measurement substituted for observationand experience.This new way of dealing with reality had numerouspositive effects. For example, it led to increased sanita-tion, which reduced background levels of many conta-gious diseases. This division of reality into separatespheres of mind and matter provided a powerful method-ology for the study and understanding of the “outside”world. It was largely inadequate, however, for under-standing inner experience, the human mind, and our rela-tionship with the world of our fellow life forms. Thus,although this dualistic view led to improved sanitation,there was no increased understanding of the naturalcycle of disease or the evolution of immune responses.diseases, animal 553
The Old and the New WorldsThe importance of animal diseases in shaping bothhuman history and cultural attitudes toward the envi-ronment can be illustrated by comparing the Old World(Eurasia and North Africa) with the New World (Northand South America). Many cultures in the Americasdeveloped agriculture, but New World agriculture wasbased almost exclusively around agronomy, for example,corn, potatoes, squash, and beans, rather than on pas-toralism, the herding and domestication of ungulates.Theonly domestic animals in the Americas were dogs, guineapigs, guanacos (llama and alpaca), and turkeys. Unlikethe domesticated ungulates of the Old World, these NewWorld domesticates were never maintained at high den-sities, humans did not drink their milk, nor were any ofthese animals except dogs kept in close proximity tohumans, as were livestock in the Old World.Many New World cultures existed at densities compa-rable to those found in Europe. The Aztec capital ofTenochtitlán may have been one of the largest cities in theworld during its heyday, and there is evidence that in cen-tral Mexico human populations surpassed the long-termcarrying capacity of the land. Similarly, many other NewWorld communities, such as cities of the Mayans, Incas,and the Mound Builder cultures along the Mississippiand Ohio River valleys, lived at densities comparable tothose found in European and Asian cultures. Despitehigh population densities, epidemic (crowd) diseasesappear to be virtually nonexistent in these indigenousNew World cultures, which is almost certainly attributa-ble to the absence of domestic ungulates that have beenthe source of most epidemic diseases (other than bubonicplague) in Europe, Asia, and Northern Africa.Impact of Animal Diseaseson the New WorldOne of the greatest ironies of the history of animal dis-eases is that the absence of nonhuman-derived conta-gious diseases and associated immune responses in NewWorld humans was almost certainly the major factor inthe successful invasion of the New World by Europeansand their worldview, which had been dramaticallyreshaped by their own experience with contagious dis-ease only a few centuries earlier. Europeans sometimesoccupied large parts of Africa and Asia, but without thedecimating impact of introduced contagious diseases,they did not signiﬁcantly reduce the indigenous humanpopulations of these areas. As a consequence, as the ageof colonialism draws to a close, the indigenous peoplesof Africa and Asia have been able to regain social andpolitical control of their own lands because they haveremained numerically dominant in their homelands.In contrast, in the Americas the introduction of animaldiseases into susceptible human populations was muchmore devastating to indigenous human populations thanduring the plague in Europe, leading to what has beenreferred to as the ﬁrst, or microbial, phase of the Euro-pean conquest of the Americas. It is estimated that 90–95 percent of the indigenous human population of theAmericas perished from introduced diseases.Contrary to popular mythology, this holocaust did notbegin with the “discovery of the Americas” by Columbusin 1492 but was initiated some time earlier by Basquewhalers,Viking settlers, and English ﬁshermen who beganlanding along the Atlantic coast of the Americas hundredsof years before Columbus arrived in the Caribbean andother Spanish explorers (conquistadors) arrived in theNew World.There is evidence that some tribes originallyliving along the Atlantic Ocean retreated inland in aneffort to escape epidemics that devastated their popula-tions well before the arrival of Cristóbal Colón at the endof the ﬁfteenth century.Despite the success of supposed conquistadors likeCortez and Pizarro, it was smallpox that really led to thecollapse of the Aztec and Inca empires. Cortez’s initial1519 foray into the Aztec civilization was much less suc-cessful than his subsequent 1520 effort after smallpoxarrived in Tenochtitlán. By the early seventeenth century,the indigenous population of Mexico had experienceddevastation exceeding 90 percent, falling from an esti-mated 20 million to less than 2 million.The impact of thedisease was demoralizing and crushed the ability of theAztecs to resist Cortez. Similarly, smallpox arrived in Inca554 berkshire encyclopedia of world history
territory in 1526, setting up the opportunity for Pizarro’ssuccessful “invasion” in 1531.There are well-documented cases of 90 percent ormore of indigenous populations being wiped out bythese new contagious diseases that arrived with bothEuropeans and their symbiotic nonhumans. In one well-documented example, the Mandans, one of the mostelaborate of the Great Plains cultures, suffered mortalityof more than 95 percent of their population after arrivalof smallpox on a Missouri riverboat in 1837.The introduction of alien diseases had a devastatingimpact on the indigenous peoples of the Americas. If thedeaths of 20 to 40 percent of local populations in Europeas a result of plague caused restructuring and rethinkingof the philosophical role of humans in the world, it is dif-ﬁcult to imagine the spiritual, social, and philosophicalimpact of loss of 90 to 95 percent of a population, asoccurred in many indigenous peoples of the Americas.Disease is a major factor in limiting rates of populationgrowth, in fact, populations free of the impact of diseasestypically outstrip those subject to disease. IndigenousAmericans appeared relatively free of epidemic diseaseprior to the arrival of Europeans. As a consequenceindigenous populations had not evolved any immunity tocontagious diseases.They did not lack the ability to pro-duce immune responses, however, the devastation ap-peared to result from the way in which indigenouspopulations were exposed to contagion.The major killersof indigenous Americans, smallpox and inﬂuenza, werelethal primarily to persons in the age range of 15 to 40years, hence the most valuable and productive membersof a population, both culturally and demographically.These diseases typically arrived in clusters, punctuated bybrief interludes of respite. Thus communities might beravaged by a series of three or four diseases, followed bya period of remission.Then such communities might behit by another bout with a new disease or set of diseases.This combination of periodicity of events with the plu-rality of the diseases prevented the ability to evolveimmune responses.This pattern generated extreme psychological and spir-itual stress. Unable to prevent disease or care for them-selves or loved ones, abandoned by kin and other tribalmembers ﬂeeing the epidemic, and in the process oftencarrying the disease to other peoples and communities,many individuals and communities simply gave up hope.Many engaged in activities that only hastened theirdeaths, such as sweats followed by immersion in coldwater. The inability of their traditional holistic methodsof treating diseases to contain these contagions causedthem to lose faith in their healers and medicine peopleand also to abandon traditional spiritual practices andceremonies. Because the European invaders had devel-oped some immunity to these diseases, many indigenouspeoples assumed that European spiritual and philo-sophical traditions were superior to their own, leading toacceptance and adoption of Christianity and its tenets.The failure of indigenous spiritual traditions, com-bined with the introduction of new goods and materials,led indigenous peoples to abandon centuries-old tradi-tions of dealing with the natural world, based on respect,connection, and conservation. Some peoples may evenhave blamed the wildlife and the natural world for theepidemics, because it appears that many indigenous peo-ples associated disease with wildlife and developed cul-tural traditions that were assumed to minimize thediseases, animal 555St. Vitus’ DanceAt the height of the Black Death (1348-1350), amedical condition known as “St. Vitus’ Dance”began to emerge in the Rhineland (Germany).Thecondition purportedly was an offshoot of thedances people did to protect themselves from theplague. The principal symptoms were ceaselessdancing, hysteria and foaming at the mouth; therewas no cure.Amidst our people here is come,The madness of the dance.In every town there now are someWho fall upon a trance.It drives them ever night and day,They scarcely stop for breath,Till some have dropped along the wayAnd some are met by death.Source: Sachs, C. (1937). World history of the dance (p. 253). New York: W.W.Norton.
likelihood and impact of disease. For example, the Chero-kee assumed that disrespectful treatment of killed deercould lead to crippling illness. Similarly, the Anishnabe(Chippewa, Ojibway) peoples apparently developed theMediwiwin healing society and related ceremonies inresponse to diseases they associated with wildlife, but thediseases were more likely the results of pre-Columbiancontact with Europeans.Not only humans suffered as a result of the introduc-tion of these diseases. Many natural populations of ani-mals, including deer, caribou, moose, bison, and beaver,on which indigenous peoples depended as sources offood and clothing, also experienced massive die-offsfrom west of Hudson’s Bay to the Rocky Mountains dur-ing the latter part of the eighteenth century.These deathsprobably resulted from disease introduced by Europeansthrough their domestic animals. It is worth noting thatthese die-offs were primarily among ungulate popula-tions, which would have been most susceptible to theungulate-borne contagious diseases characteristic ofEurope and Asia. New World carnivores, such as wolvesand bears, appeared relatively unaffected by these ill-nesses but suffered as a result of loss of their ungulatefood supplies.In addition to the impact of disease, additional damagewas inﬂicted upon natural populations of animals whenindigenous people began to destroy animal populationsbecause of apparent antipathy toward animals, who wereassumed to have broken their covenants with humans byinfecting them with disease.Thus, one ironic consequenceof the introduction of nonhuman-derived diseases was thedestruction of cultural traditions based on respect for non-humans. Most, if not all, indigenous cultures of NorthAmerica had philosophical traditions as a part of whichnonhumans were regarded as creator spirits, and theconcept of relatedness was based upon ecological rela-tionships. It has been argued that the devastating impactof introduced disease on these cultures caused them toturn on their nonhuman relatives, leading some tribes tobe willing to wipe out local populations of beaver, deer,bison, and wolves in order to trade furs for Europeantrade goods and metal.The European Traditionand the Natural WorldThe invading European tradition, derived primarily fromEnglish and Scots cultures, had a very different relation-ship with the natural world, especially as a result of theRenaissance and the “rationalist” tradition, which workedto separate itself from any association with the naturalworld, except as a source of resources for exploitation.Protestant Christian sects that appeared in westernEurope toward the end of the Renaissance (during theReformation) developed philosophical traditions thatoffered no encouragement for investigation into the waysof God’s creatures. God had given humans “dominion”over nonhumans, providing sufﬁcient justiﬁcation forany action regarding the natural world.Europeans regarded mountainous country as unpleas-ant and dangerous, and forests were considered to beeven worse.That these places were wild, hence untamed,was sufﬁcient to trigger terror and hostility in WesternEuropeans. The “wild” (natural world) was so unreason-ably fearsome that encroachment of wild creatures intothe human domain was highly alarming. A bee ﬂying intoa cottage or a bird rapping at the window was enough tofrighten people.The English House of Commons rejecteda bill in 1604 because a jackdaw ﬂew through the cham-ber during the speech of its sponsor.This difference in response to the nonhuman (natural)world continues to manifest itself in contemporaryresponses to animal-borne disease in the present day.These responses are often extreme in comparison withthe actual threat posed. The most egregious response inrecent years has been the slaughter of hundreds of thou-sands of farm animals, particularly in the British Isles, inresponse to minor outbreaks of hoof and mouth diseaseand the sporadic and highly unusual occurrence of so-called mad cow disease.In the case of hoof and mouth disease, the threat isalmost exclusively economic.There is little evidence thathoof and mouth disease represents any serious threat tohuman health. Still the economic threat is deemed sufﬁ-cient to destroy hundreds of thousands of animals,mostly because the possibility exists that they may have556 berkshire encyclopedia of world history
been exposed to the disease. Can any moral being imag-ine such a draconian solution if the animals exposed toa potential contagion were Homo sapiens, rather thanungulates? Similarly, wild bison that stray beyond theborders of America’s Yellowstone National Park are sum-marily slaughtered by agents of the state of Montana onthe grounds that these animals might act as reservoirs forthe cattle disease brucellosis.The irony in this case is thatbrucellosis is a disease that evolved in Old World bovidsand was introduced into America along with cattle. Nobison has ever been demonstrated to show the symptomsof brucellosis, yet the fact that a low percentage of bisontest positive for exposure to the pathogen is deemed suf-ﬁcient reason to kill them.The response to so-called mad cow disease, moreproperly called bovine spongiform encephalopathy(BSE), is even more absurd. BSE appears to be one of agroup of related pathological conditions that may becaused by prions, which appear to be protein moleculescapable of self-replication. Other diseases in this categoryare scrapie in sheep, and kuru and Creutzfeldt-Jakobsyndrome in humans. Such pathological conditionsimpact the central nervous system (CNS) and graduallydestroy the brain. The damage to the CNS is what pro-duces the symptoms that have disrespectfully led to thiscondition being designated as mad cow. A far better andmore accurate term would be acutely distressed cow.These apparently prion-based conditions are not directlycommunicable and can only be passed through con-sumption of CNS tissue including brain and spinal cord.The only reason these conditions appeared to spread inthe United States and England is because slaughter-houses in those countries use “wastes” remaining afterbutchering to be ground up and added to cattle feed asa protein supplement.In humans it is obvious that only through consumingCNS material can humans become infected. Outbreaks ofkuru in New Guinea are clearly related to the cultural tra-dition of consuming the brains of other humans as partof a cannibalistic tradition. In England, BSE-type syn-dromes have shown up in humans who consumed low-grade commercial hamburgers. It seems obvious thatbanning use of the waste products of slaughterhouses inboth hamburger for human consumption and in cattlefeed could stop any possible outbreak, yet commercialpressures have slowed or prevented such moves. Still, thetotal number of BSE human victims numbers less thantwenty, and there is little likelihood of an outbreak or ofa human contracting BSE through eating regular beef inthe form of roasts or steaks.Hanta virus is a rodent-borne viral pathogen.There isactually an entire class of Hanta-like viruses in a varietyof murid rodents. The one described as Hanta virusappears to have only one species, deer mice, Peromyscusmaniculatus, as its primary host, where it does not appearto cause signiﬁcant health problems. In humans, how-ever, this virus causes pneumonia-like symptoms thatresult in death about 50 percent of the time.This diseaseis well known to indigenous peoples of the AmericanSouthwest and may be one of the reasons that traditionalDine (Navajo) people destroy a Hogan after a person hasdied in it. In recent years this disease has caused a minorpanic in the United States because deer mice are a wide-spread common rodent. Hanta does not appear to betransmissible among humans so it is unlikely to everbecome a true epidemic. The number of recorded casesin the United States is less than 200 since the Center forDisease Control (CDC) has been keeping records.To summarize, the major environmental and health-related problems in humans result primarily from closeassociation with domestic animals.This continued prox-imity has allowed several diseases to jump from theirungulate or avian hosts and cross the species barrier intohumans.Raymond PierottiFurther ReadingAlchon, S. A. (2003). A pest in the land: New World epidemics in a globalperspective. Albuquerque: University of New Mexico Press.Cockburn, A. (1967). Infectious diseases:Their evolution and eradication.Springﬁeld, IL: Thomas Press.Crosby, A. (1972). The Columbian exchange: Biological and cultural con-sequences of 1492. Westport, CT: Greenwood Press.Diamond, J. (1997). Guns, germs, and steel. New York: W. W. Norton and Co.diseases, animal 557
Dobyns, H. (1983). Their numbers become thinned. Knoxville: Universityof Tennessee Press.Gottfried, R. (1983). The Black Death: Natural and human disaster inmedieval Europe. London: Robert Hale.Martin, C. (1978). Keepers of the game: Indian-animal relationships andthe fur trade. Berkeley: University of California Press.Sale, K. (1992). The conquest of paradise. New York: Alfred Knopf.Diseases, PlantPreliterate peoples as well as some literate peoplesbelieved that spirits cause disease. Greek physiciansdismissed this notion and instead insisted that diseasehad physical rather than supernatural causes. In the ﬁfthcentury BCE, the Greek physician Hippocrates taughtthat an imbalance of ﬂuids causes disease in humans, aclaim that left inscrutable the cause of disease in plants.In the nineteenth century, the German botanist Anton deBary, the German bacteriologist Robert Koch, and theFrench chemist Louis Pasteur swept aside the ideas ofHippocrates De Bary, working with the potato, and Pas-teur and Koch, working with cattle, demonstrated thatpathogens (parasitic microbes) cause disease. The germtheory of disease is the foundation of modern medicine.The focus on human diseases should not deﬂect atten-tion from plant diseases. Despite a perception to the con-trary, plants suffer from more diseases than humans doand for an obvious reason. Plants colonized the land 410million years ago, whereas modern humans made theirappearance only 130,000 years ago.The pathogens thatattack plants have had some 400 million more years toevolve new types by mutation than those that attackhumans.Plant diseases have shaped history. Even as nomadicforagers, humans depended on plants for sustenance.Therise of agriculture in western Asia some 10,000 years agoand its spread throughout the world have wedded thedestiny of humans to that of crops (domesticated plants).Whatever has threatened crops has threatened the healthand survival of humans.Diseases of the Staple GrassesWheat RustWheat rust is among the oldest plant diseases. Somescholars believe that a 3,800-year-old passage in Genesisrecords an outbreak of rust in the Levant that causedfamine so severe it forced the Hebrews to migrate toEgypt, the granary of the ancient Mediterranean world. Ifthese scholars are right, this text is the earliest writtenaccount of a plant disease.Only in the fourth century BCEdid Theophrastus, aGreek botanist and pupil of Aristotle, coin the term rustfor this disease because of its reddish hue on the leavesand stem of wheat plants.Theophrastus wrote that wheatplanted in valleys and other low ground suffered fromrust more often and more acutely than wheat planted onhigh ground though he could not explain this fact.That insight came to the Romans.As early as 700 BCE,they identiﬁed the reddish hue on wheat plants as themark of rust. At that time they began to worship Robigus.Historians identify Robigus as the god of rust, a fair state-ment so long as one remembers the Greek rather thanRoman origin of the term rust. The idea that a godunleashed rust on the Romans underscores their beliefthat rust had a supernatural cause.Trade with the Greekcity-states led the Romans to abandon a supernaturalexplanation of plant diseases. In the ﬁrst century BCE, thenaturalist Pliny the Elder made the crucial link betweenmoisture and the onset and spread of rust, writing thatrust afﬂicted wheat grown in areas where fog and dewwere common in morning and evening. Pliny’s insightinto the role of water in spreading rust was prescientbecause rust, like all fungal diseases, spreads in wet envi-ronments. The rust fungus needs water to produce themillions of spores that are the next generation of fungi.Two centuries later, the agricultural writer Columellawarned farmers against staking their livelihood on wheat.The only protection against rust was to grow a diversityof crops. Columella recommended cultivation of thechickpeas and lentils because of their immunity to rust.Columella had reason to worry: The ﬁrst three cen-558 berkshire encyclopedia of world history
turies of the Common Era were unusually wet in thelands along the Mediterranean Sea, bringing rust towheat ﬁelds throughout the Roman Empire. Some his-torians ﬁnger rust as a culprit in Rome’s economicdecline after 200 CEand in the dissolution of the empirein the ﬁfth century.In the seventh and eighth centuries,Arabs brought thebarberry bush with them as they swept across NorthAfrica and into Spain. Neither Arabs nor Europeansunderstood that the bush harbors rust fungi because thefungi inhabit the bush without harming it, much as thepathogens that cause malaria and yellow fever live in the gut of the female mosquito without harming her. Abarberry bush that harbors rust fungi has no symptomsof disease. Only in the seventeenth century did Europeansbegin to suspect the bush to be a Trojan horse. In 1660France enacted the ﬁrst law to eradicate the bush. OtherEuropean nations passed similar laws, as did the Ameri-can colonies in the eighteenth century.These measures were not enough to stop the spread ofrust. Plant breeders in the nineteenth century began tosearch for rust resistant wheat to cross with high-yieldingbut susceptible varieties, a program that accelerated thatcentury as England, France, the German states, and theUnited States poured money into agricultural science.Around 1900 agronomists at the U.S. Department ofAgriculture identiﬁed an Italian durum wheat suitable forpasta and a Russian emmer wheat suitable for bread.These were the ﬁrst of innumerable resistant wheat vari-eties that give humans the best, if incomplete, protectionagainst failure of the wheat crop from rust.Rice Stunt DiseaseChinese records ﬁrst mention the cultivation of rice4,000 years ago, though its cultivation may have begunin southeastern Asia. By 1000 BCE, farmers grew rice inChina, the Korean peninsula, and the swath of landbetween modern Vietnam and India. By the ﬁrst centuryCE, farmers were growing rice in Japan, Indonesia, andthe Philippines. The people of these regions were nearlyas dependent on rice as the Irish would be on potato indiseases, plant 559the nineteenth century.True, farmers also grew soybeansthroughout Korea and China, and wheat grown alongthe Indus River reached the people of central and south-ern India by trade, but soybeans and wheat were minorsupplements to a diet of rice.Roughly forty diseases afﬂict rice making difﬁcult thetask of sorting among them, as well as among climaticfactors, to explain the 1,800 famines that Chinese docu-ments have recorded since 100 BCEand the 70 in Indiasince 33 CE. Because rice needs more water than anyother grain to thrive, Chinese and Indian texts oftenattributed crop failures to inadequate or impure water.In the sixth century CE, a Japanese text mentionsstunted (short or dwarf ) rice plants that bore little or norice. The condition bafﬂed farmers for 1,200 years. In1733, 12,000 Japanese died of famine when stuntdestroyed their rice crop, yet no one was any closer tounderstanding what stunted rice plants. Unlike Europe,Asia never developed science in its modern form but onlygradually assimilated it from Europeans during the eigh-teenth and nineteenth centuries.The people of Japan andcontinental Asia did, however, have a tradition of carefulobservation. This tradition led one Japanese farmer in1874 to study the feeding habits of leafhoppers on riceplants. He doubted that insect bites alone could arrestplant growth and instead proposed that leafhoppers car-ried a pathogen that they transmitted to rice plants bybite. The pathogen, not leafhoppers, stunted rice plants.The idea was as novel as it was correct. Leafhopperscarry within their gut Rice Dwarf Virus just as, one mayrecall, various species of mosquitoes carry the pathogensfor malaria and yellow fever. Rice Dwarf Virus remainsvirulent throughout a leafhopper’s life, and femaleleafhoppers pass the virus to their offspring, multiplyingit with each generation.When the leafhopper populationis large, as it must have been in Japan in 1733, the virusbecomes widespread enough to cause failure of the ricecrop even though the leafhopper is an inefﬁcient ﬂier.The discovery of insect transmission of a pathogenopened a new ﬁeld in the study of plant diseases by unit-ing entomology, the study of insects, with plant pathology.
Scientists came quickly to understand that control ofinsect populations is essential if one hopes to minimizecrop damage from an insect-borne pathogen. It was nolonger enough for the plant pathologist to understanddiseases. He now had to understand the feeding andmating habits of insects and their distribution in areas ofdisease. The need to combat insects accelerated thestudy and development of insecticides as a branch ofapplied chemistry in the twentieth century.The study ofinsect-borne viruses and the development and use ofinsecticides would later be crucial in ﬁghting corn dis-eases in the United States.Rye ErgotismThe importance of wheat and rice to the sustenance ofEuropeans and Asians has deﬂected attention from ryeand its diseases. The Germanic tribes that settled thelands that are today France and Germany began growingrye in the second century CE.Wheat always commandeda higher price than rye, making rye bread the staple of thepoor until the even cheaper potato spread throughEurope between the sixteenth and nineteenth centuries.The diseases of rye thus afﬂicted the poor rather thanthe rich. Particularly serious was ergotism, a fungal dis-ease that ﬁlls rye grains with a toxin that in sufﬁcientquantities causes convulsions and death in humans.Unlike most plant diseases, ergot of rye threatens humansby poisoning them rather than by causing famine. Theagony of death from ergot toxicity led medieval Euro-peans to attribute the disease to God’s wrath, hence thename “Holy Fire.” Medieval chronicles cite the ﬁrst out-break of Holy Fire in the eighth century. In 857 CE, thou-sands died in the Rhine Valley, with smaller outbreaksthroughout France and Germany.One may recall that fungi spread in wet environments.Evidence from dendrology and medieval chronicles sug-gests that after 1000 CE, Europe’s climate turned wet andcool, hastening the spread and severity of ergotism innorthern and western Europe. An outbreak in 1039 wasthe ﬁrst in a series of virulent outbreaks between theeleventh and eighteenth centuries. Ergotism along withfamine in the early fourteenth century may explain thehigh mortality of the Black Death. Plague, if the cause ofthe Black Death, should not have killed between a thirdand half of Europe’s people between 1347 and 1351, forplague is a disease of rodents and other small mammals.Yet ergotism and famine may have left Europe’s peasantsand urban poor too weak to ward off plague. The resultwas the worst pandemic of the Middle Ages.Diseases of the Staple CropsIndigenous to the AmericasLate Blight of PotatoThe fungus that causes late blight of potato is at the cen-ter of a tragedy, the Irish Potato Famine.The tragedy hasits roots not in Europe but in the Andes Mountains,where the natives of Peru domesticated the potato. TheSpanish conquered Peru in the sixteenth century. Insearch of gold, they found a more valuable commodity,the potato. From Peru the potato reached Spain by shiparound 1570, then spread west through continentalEurope and north across the English Channel, reachingIreland before 1800. On the continent, the potato viedwith rye bread as the staple of the poor. In Ireland poli-tics and economic exploitation made it the only staple.For many years the Irish sought independence fromEngland, a goal England’s Lord Protector Oliver Crom-well crushed. In the 1650s his army ravaged Ireland andCromwell divided the land among his supporters.Thesemen charged rents so high that the Irish peasant could setaside only a small plot of land for his family. The rest ofthe land went to raise the grain and livestock peasantsneeded to pay rent.By 1800 the Irish, squeezed by their lack of land andhigh rent, had no choice but to embrace the potato forsustenance because it yielded more food per unit of landthan any grain. Reliance on a single crop is always risky,as Columella had emphasized in the ﬁrst century. Thepotato posed risks far greater than the Irish could haveimagined.The Spanish had brought little more than a fewhandfuls of potatoes with them. These potatoes were ofthe same stock and thus genetically uniform. Because the560 berkshire encyclopedia of world history
potato propagates by shoots, new potatoes, barringmutation, are genetic equivalents of the parent potato.With all potatoes near carbon copies of one another, anydisease that threatens one potato threatens all.With the potato vulnerable, catastrophe struck in1845. Six weeks of rain hastened the spread of the blightfungus across Ireland.The plants died and potatoes rot-ted in the ground. Blight struck again in 1846.Their sta-ple gone, the Irish scrounged for nuts and roots whileEnglish landlords took their wheat and livestock. Onemillion starved and 1.5 million ﬂed Ireland.The tragedy galvanized scientists throughout Europeinto action. In 1861 Anton de Bary isolated the culprit, afungus he named Phytophthora infestans, and by spread-ing it on healthy potato plants demonstrated that itcaused blight.The Potato Famine had spurred de Bary’sdiscovery, which marked the beginning of plant pathologyas a science.More than that, potato blight made conspicuous theevils of economic oppression. On the heels of the fam-ine, the German socialist Karl Marx and his Englishcounterpart Friedrich Engels in 1848 denounced theexploitation of the poor in the Communist Manifesto.Revolution swept across Europe that year as intellectualsand the poor demanded an end to oppression. Thepotato blight was more than a disease; it was a call toarms, a call for political and economic reforms. The po-tato blight thus left its imprint on agriculture, science,politics, and economics.Corn DiseasesAs with potato diseases, scientists know little about corndiseases during the pre-Columbian period.What is clear,however, is that corn, unlike potato, is a cross-pollinatingplant that produces plants with genetic diversity. Cross-breeding achieves diversity by reshufﬂing chromosomesin any plant or animal, including humans. This diversityshould minimize the occurrence of epidemics, for withina heterogeneous population some individuals, in this casecorn plants, should be resistant to disease.diseases, plant 561The Irish Potato FamineThe following account of the Irish potato famine wasprovided by Alexander Somerville (1811-1885), theBritish journalist whose Letters from Ireland duringthe Famine of 1847 were published in the Manches-ter Examiner.I saw the poor man and his poor family, and trulymight he say, “God have mercy!” They were skeletonsall of them, with skin on the bones and life within theskin. A mother skeleton and baby skeleton; a tall boyskeleton, who had no work to do; who could donothing but eat, and had nothing to eat. Four femalechildren skeletons, and the tall father skeleton, notable to work to get food for them, and not able to getenough of food when he did work for them. Theironly food was what his wages of 10 d. per daywould procure of “yellow meal”—the meal of theIndian corn.The price of that was 3s. per stone of 16lb. This gave for the eight persons 26 lb. 10 oz. ofmeal for seven days; being about seven ounces and ahalf per day for each person. No self-control couldmake such persons distribute such a starvation offood over seven days equally. Their natural cravingsmade them eat it up at once, or in one, or three daysat most, leaving the other days blank, making thepangs of hunger still worse.But in the calculation I am supposing all the wagesgo for meal. I believe none of it was expended on any-thing else, not even salt, save fuel: fuel in this villagemust all be purchased by such people; they are notallowed to go to the bogs to cut it for themselves. Noris this the season to go to the bogs, if they wereallowed. The fuel required to keep the household ﬁremerely burning, hardly sufﬁcient to give warmth toeight persons around it, to say nothing of half-nakedpersons, would cost at least sixpence a day. Where-fore, no fuel was used by this family, nor by otherworking families, but what was required to boil themeal into a stirabout .. .Source: Somerville, A. (1994). Letters from Ireland during the famine of 1847. Dublin:Irish Academic Press.
The Corn VirusesSince the 1920s, corn breeders have reduced the geneticdiversity by breeding a small number of high-yieldingcorn plants of roughly uniform genotypes, making cornvulnerable to epidemics. An outbreak of corn stunt dis-ease along the lower Mississippi valley in 1945, reminis-cent of the stunt disease that ravaged rice in Asia,presaged corn’s vulnerability to an epidemic. As is true ofrice stunt, a virus causes corn stunt disease and is spreadby an insect, in this case a species of aphid.Worse was to follow. A few stunted corn plants inPortsmouth, Ohio, erupted in an epidemic that engulfedthe Ohio and Mississippi valleys in 1963 and 1964, cost-ing farmers who had planted on some lands along theserivers their entire corn crop.The culprit was not the corn-stunt virus as scientists ﬁrst thought but two viruses:Maize Dwarf Mosaic Virus (MDMV) and Maize ChloroticDwarf Virus (MCDV). The initial confusion among sci-entists slowed their response, opening the entire Midwestand South to the danger of an epidemic.The method of virus transmission saved corn growers.A species each of aphid and leafhopper transmits MDMVand MCDV respectively by bite. Both feed primarily onJohnsongrass that grows along the Ohio and Mississippirivers. Both viruses inhabit Johnsongrass, as the ergot fun-gus inhabits the barberry bush, without signs of disease.But neither insect is a strong ﬂier, and, unlike the leafhop-per that carries Rice DwarfVirus, neither aphid nor leaf-hopper retains MDMV and MCDV in virulent form morethan forty-ﬁve minutes, limiting the range of both viruses.Once scientists had ﬁngered the aphid, leafhopper, andJohnsongrass as culprits, the U.S. Department of Agri-culture in fall 1964 launched a campaign to kill aphidsand leafhoppers by insecticide and Johnsongrass by her-bicide (chemicals unavailable to save the Japanese fromfamine in 1733). The expenditure of chemicals andmoney ended the threat of these viruses and led scientiststo believe they held the upper hand against corn diseases.Success prevented all but a few scientists from question-ing the wisdom of growing genetically uniform cornthroughout the Midwest and South.Southern Corn Leaf BlightCatastrophe struck in 1970 as Southern Corn LeafBlight, a fungal disease, swept the United States, destroy-ing 710 million bushels of corn, 15 percent of the corncrop that year. From Texas to Georgia and Florida, farm-ers lost half their corn crop.These losses cost farmers $1billion and the collapse of farm commodity prices costinvestors billions more. In a single summer, one corn fun-gus threatened ﬁnancial ruin.Plant pathologists identiﬁed a single female parent ofcorn (a type of corn that produced no pollen and so wasmale sterile) as susceptible to Southern Corn Leaf Blight.By dropping it from the corn pedigree, agronomists brednew varieties of corn resistant to South Corn Leaf Blight,but corn remains as genetically uniform today as it wasin 1970.562 berkshire encyclopedia of world historyAnts and Black PodDisease in AfricaBlack pod disease (Phytophthora pod rot) is aserious disease in Africa where it damages the eco-nomically valuable cocoa plant.The role of ants inspreading the disease was ﬁrst noted in 1927 anddescribed in detail in 1970.A small black ant also has been implicated as anagent in bringing Phytophthora from the soil topods on which it attends to scale insects. Twotrees with no black pod, at the margins of acocoa plot had pods above the ground withscales on the pod stalk being cared for by theants.Two sporulating diseased pods were placedat the base of each tree and covered with litter.Two weeks later all seven pods (three on one tree,four on the other tree) had the black-pod diseasestarting at the petiole side where the ants hadbuilt tents made of soil and debris to protect thescales from the rain. Pods at the same height butwithout the ant on three adjacent trees remainedhealthy and free of the disease.Source: Gorenz,A. M. (1969). Spread of disease from the tree base to pods in thecanopy. Annual Report of the Cocoa Research Institute of Nigeria (p. 53).
Future ProspectsThe imperative to minimize crop losses from diseases willonly intensify in the future as the human populationgrows exponentially. At their origin 130,000 years ago,modern humans cannot have numbered more than a fewthousand. Only around 1800 did the human populationnumber 1 billion.The population doubled by 1940 andagain by 1975. Today, more than 6 billion humanscrowd the earth, and demographers fear our numbersmay swell to upwards of 9 billion by 2045.To avert famine on an unprecedented scale, farmersmust triple food production by then. To fall even 2 per-cent short of the goal, demographers believe, will con-demn some 270 million people to starvation. Only withthe highest yielding varieties of potatoes, corn, soybeans,wheat, and rice, the sustenance of humanity, can humanshope to avert widespread starvation. But only a smallnumber of varieties of any crop can yield enough food fora hungry world.The future will only exacerbate the prob-lem of genetic homogeneity. Crops may become morerather than less vulnerable to epidemics.The future may bring new solutions but at the momentonly two seem viable. First, scientists might use theemerging technology of genetic engineering to combinedisease resistance and maximum yield in a crop, anachievement that has eluded the traditional plant breeder.But there are obstacles to this goal. In the 1990s, fright-ened Americans branded as “Frankenfood” the ﬁrst vari-ety of corn genetically engineered to be resistant to aninsect. As in the past, public fears may slow the advanceof science. Even with public support, the engineering ofdisease-resistant plants is an arms race. Mutation willforce scientists to engineer plants resistant to newpathogens ad inﬁnitum. One cannot foresee the outcomeof this struggle between pathogen and plant.Second, humans might limit their numbers. Contra-ceptive devices make this approach possible.The UnitedNations has for decades advocated population control,but with the notable exception of China, most nationsare far from committed to holding their population incheck.Will the rest of the world comply? At present theUnited States will not, and as was true during the ColdWar, the United States and China are again at logger-heads, with Europe, Africa, and the rest of Asia unsurewhich to follow. If humans do not limit their numbers,plant diseases, if unchecked by science, will limit popu-lation by famine. Ireland in 1845 and 1846 may be theearth writ small.Christopher M. CumoFurther ReadingAgrios, G. N. (1997). Plant pathology (4th ed). San Diego, CA: Acade-mic Press.Carefoot, G. L., & Sprott, E. R. (1967). Famine on the wind: Plant dis-eases & human history. London: Angus & Robertson.Francki, R. I. B., Milne, R. G., & Hatta, T. (1985). Atlas of plant viruses.Boca Raton, FL: CRC Press.Harris, K. F., & Maramorosch, K. (Eds.). (1980). Vectors of plantpathogens. New York: Academic Press.Klinkowski, M. (1970). Catastrophic plant diseases. Annual Review ofPhytopathology, 8, 37–60.Littleﬁeld, L. J. (1981). Biology of the plant rusts: An introduction. Ames:Iowa State University Press.Matthews, R. E. F. (1991). Plant virology (3rd ed.). New York: AcademicPress.Schumann, G. L. (1991). Plant diseases:Their biology & social impact. St.Paul, MN: American Phytopathological Society.Shurtlett, M. C. (Ed.). (1980). A compendium of corn diseases (2nd ed.).St. Paul, MN: American Phytopathological Society.Smith, K. M. (1972). A textbook of plant virus diseases. New York: Aca-demic Press.Stefferud, A. (Ed.). (1953). Plant diseases: The yearbook of agriculture.Washington, DC: Government Printing Ofﬁce.Tatum, L.A. (1971).The southern corn leaf blight epidemic. Science, 171,1113–1116.Thurston, H. D. (1973). Threatening plant diseases. Annual Review ofPhytopathology, 11, 27–52.Ullstrup, A. J. (1972). The impacts of the southern corn leaf blightsepidemics of 1971–1972. Annual Review of Phytopathology, 10,37–50.Van Regenmortel, M. H. V., & Fraenkel-Conrat, H. (Eds.). (1986). Theplant viruses. New York: Plenum.Vanderplank, J. E. (1963). Plant diseases: Epidemics & control. New York:Academic Press.Webster, R. K., & Gunnell, P. S. (Eds.). (1992). Compendium of rice dis-eases. St. Paul, MN: American Phytopathological Society.Western, J. H. (Ed.). (1971). Diseases of crop plants. New York:Macmillan.Wiese, M.V. (1987). Compendium of wheat diseases. St. Paul, MN: Amer-ican Phytopathological Society.Woodham-Smith, C. (1962). The great hunger, Ireland, 1845–1849.New York: Harper & Row.diseases, plant 563