continually reverted to its former marshy state, drawing repeated calls from the town assembly for landowners to keep their ditches “well scowred.”104 English landowners in the valley learned time and again that water had to go somewhere, and, especially during the spring freshets, it could not always be contained. The persistence of waters to find their own way to the waiting banks of the Connecticut and its tributaries, and then downriver to Long Island Sound, would continue to frustrate its human inhabitants throughout the colonial period and, indeed, can still cause problems today.
Even as the valley’s eighteenth-century inhabitants continued to wrestle with the increased hazards of periodic flooding, they benefitted from the absence of an even greater scourge to their health and well-being. The disappearance of large areas of standing water reduced the breeding habitat for, and thus the numbers of, mosquitoes in the region.105 This in turn spared the valley’s human residents both the annoyance of being bitten and the very real dangers associated with mosquito-borne illnesses. Malaria, for example, was a common affliction throughout the early modern Atlantic World. The disease’s near-complete absence in the eighteenth-century valley suggests the wide-ranging ecological impacts of beaver extermination in the Connecticut Valley, and New England more generally.
Plasmodium vivax, the species of malarial microbe that made up the vast majority of cases in New England, seldom proved fatal in itself. This species is less deadly than Plasmodium falciparum, which can lead to organ failure and which came to predominate in the American south. But the symptoms of P. vivax could still be quite debilitating for sufferers, and could expose their hard-pressed immune systems to other diseases that might result in death. Malaria afflicts sufferers with recurring fevers interspersed with severe cases of the chills. Seventeenth- and eighteenth-century writers commonly referred to malaria as the “ague” (a general term for fevers, although it was especially associated with malarial symptoms), “remittent” or “intermittent fever” (a reference to the chills that interspersed spiking malarial fevers), or as “tertian” or “quatrain fever” (depending on whether the periods between fevers averaged three or four days). Although early modern theorists commonly blamed malarial outbreaks on the presence of “miasmas” (“bad airs” usually associated with marshes and other areas of stagnant water) the exact nature of the disease and its transmission remained a mystery. This was at least partially because malaria is a recrudescent disease—one in which the invading microbes can lay dormant for a period of years between the outbreak of symptoms. Malaria sufferers who seemed to have been cured of their fevers could quite suddenly fall ill again many miles, or even an entire ocean, away from the areas of “bad air” where they first contracted the disease.106
Three factors are required for malaria to persist as an endemic disease within a region: the presence of the protozoa which causes the disease, a sufficiently large human host population to maintain the microbe and allow it to multiply, and a sufficiently large Anopheles mosquito population to transmit the microbes to new hosts. Prior to 1600, the lands that would become New England housed a large number of populous human communities as well as a substantial Anopheles mosquito population—the latter a source of considerable complaint for early European explorers in the region. However, like so many of the deadliest and most debilitating diseases to afflict humanity, malaria had evolved in the eastern hemisphere. To gain a foothold in New England, malaria plasmodium first needed to hitch a ride across the Atlantic. Beginning in the 1620s, thousands of English emigrants unwittingly volunteered as carriers.
Malaria was endemic to many areas of southeastern England in the seventeenth century. The very counties which contributed the majority of emigrants to the first wave of Puritan settlement in New England also experienced some of the highest rates of malarial fever.107 Malaria was also widespread in the Netherlands, where many leaders of the Pilgrim and Puritan migrations lived in exile prior to their departure for America. For example, Thomas Hooker, Hartford’s first minister, contracted the “ague” in 1633 (or earlier) while living in Rotterdam.108 After recovering from his initial illness, Hooker, along with many of his coreligionists, carried dormant Plasmodium protozoa in their bloodstreams when they crossed the Atlantic. Any recurrence of symptoms turned infected migrants into transmitters of the disease, as native mosquitoes spread malaria from the initial host to his or her neighbors.
Malarial fevers plagued New Englanders from at least the 1640s forward, and recurred region-wide throughout the remaining decades of the seventeenth century.109 One scholar has suggested that an outbreak of malaria helps explain symptoms ascribed to some of the supposed victims of the Connecticut witchcraft craze of 1647–1653.110 John Winthrop Jr., Royal Society member and governor of Connecticut, recorded numerous new cases in the colony from 1657 forward—including one especially virulent outbreak he witnessed firsthand during a visit to Hartford in the summer of 1672.111 Indeed, in the 1680s and early 1690s, the towns of the Connecticut Valley gained a reputation as particularly bedeviled by the scourge of malaria.112
Then, after approximately 1700, malaria almost completely disappeared from both the Connecticut Valley and New England more generally.113 New England’s climate is usually credited for malaria’s eighteenth-century disappearance.114 Unlike the warmer southern colonies, the greater length of northern winters limited the annual number of days during which mosquitoes were active at the same time that greater severity of cold reduced the survival rate of adults and larvae. However, a climactic explanation fails to account for malaria’s persistence in the first decades after English settlement or for the disease’s decline just as average temperatures began to rise from the seventeenth-century low point reached during the depths of the Little Ice Age. Nor can it explain the persistence of malaria in areas like New York City, which shares, roughly, the wintery conditions of southern New England. Even more puzzling is the case of Deerfield, the one exception to the general disappearance of malaria from the eighteenth-century Connecticut Valley. In the neighborhood immediately around Deerfield, new cases of malaria continued to appear throughout the 1700s. Locals blamed these persistent outbreaks, so exceptional in New England as a whole, on a group of undrained marshes and stagnant pools that persisted on the unimproved lands east of Deerfield, on the far side of the Connecticut River.115
In this, the inhabitants of Deerfield offer a clue both to the persistence of malaria as a health concern in their own locality and the disease’s disappearance from the larger region after 1700. Since the pool of human hosts continued to increase as the population of the valley grew during the eighteenth century, and the Plasmodium microbe remained in the region, at least, in Deerfield, then a decline in the number of available disease vectors, of Anopheles mosquitoes, must explain malaria’s disappearance. As water tables throughout the valley slowly fell, no longer maintained by the presence of beaver dams, related ponds and wetlands dried up and mosquito-breeding habitat disappeared. Euro-American settlers, intent on draining lands and improving them for agriculture, contributed to the process. Only in the lands east of Deerfield—in an area that had, at the time of first settlement, been a lake bed—did sufficient standing waters persist to provide adequate breeding grounds for a mosquito population capable of maintaining malaria as a local health threat. Deerfield’s own population, likely supplemented by migrants passing through town, some of whom likely had experience in the West Indies trade, provided a reservoir from which the Plasmodium could spread, via mosquito intermediaries, to new hosts.
That the drainage of lands following the decimation of beaver ponds lay behind malaria’s post-1700 retreat from New England is further evidenced by the conditions that eventuated the disease’s return at the end of the eighteenth century. The millponds associated with the saw- and gristmills of the colonial era provided insufficient breeding habitat to reestablish mosquito populations capable of maintaining malaria outbreaks. The much grander engineering projects of the last decade of the eighteenth century, and of the nineteenth century, were another matter. Malaria returned to the valley (outside of Deerfield) in 1792, striking at the towns of Northampton and nearby Hadley. Local residents had little doubt as to the cause of the new outbreak. They pointed to the waters backed up behind a recently constructed dam—a
