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Ken W. Watson

Note: This article first appeared in the Winter/Spring 2007 edition of Rideau Reflections, the newsletter of the Friends of the Rideau (

As we sit here, pining for summer, thinking fondly of those dog days of August, it’s worth remembering that during construction of the Rideau Canal, August was known as the “sickly season.” The sickness was malaria, a disease not understood during canal construction, and its history in North America not remembered today.

To understand how malaria affected those building the canal, one must first understand what malaria actually is. Malaria is caused by parasites of the genus Plasmodium, of which there are four different species. They all work anopheles-mosquito.gif - 3325 Bytesthe same way; the parasite needs both humans and a particular type of mosquito to complete its life cycle. In Ontario, a species of the female anopheles mosquito (still present) was the carrier. The anopheles mosquito is a dusk to dawn biting mosquito that will bite a human more than once, the latter feature being critical for the spread of malaria.

The basic life cycle of the malaria parasite starts when a malaria-carrying mosquito bites a human. The parasites (as sporozoites) head to the liver and proceed to incubate. The sporozoites multiply and, when sufficient numbers are reached, head out to invade red blood cells and produce merozoites. These merozoites multiply and eventually burst the red blood cells, producing the classic chills and fever symptoms in the victim. It is at this stage that anopheles mosquitoes can pick up the parasites when taking blood from a human with the disease. Once back in the mosquito, the merozoites develop into male and female gametocytes. These gametocytes fuse in the mosquito’s gut (stomach) and produce sporozoites, which head into the mosquito’s salivary glands, ready to be injected into the next human victim, and the cycle starts all over again.

In Ontario, winter would normally break this cycle. But one variety of malaria, a temperate form known as P. vivax, has the ability to hibernate in the liver. Some of the P.vivax sporozoites do the normal malaria cycle (infecting their hosts that year), others “over-winter” in the liver, coming out the next summer when the mosquitoes have returned, to start the cycle again.

Malaria was not unique to the Rideau – it was present in Ontario as early as the 1700s. For example, in 1793, Mrs. Simcoe, wife of the Lieutenant Governor of Upper Canada, was absent from a gala ball – she was sick with malaria. There is some speculation that the great influx of Loyalists from the U.S. in the late 1700s, many of whom would have been carrying malaria, expanded the range of the disease in Ontario. At that time it was called by many names, “fever, ague, lake fever, swamp fever, intermittent fever, and fever of the country.” The most common terms were “ague” or “fever & ague.” Anyone reading period literature will see these terms commonly mentioned.

Lock Construction Camp at Jones Falls
The Lock Construction Camp at Jones Falls
Located at the spot now occupied by the Blacksmith’s shop at Jones Falls, these buildings didn’t prevent malaria carrying mosquitoes from entering at night. Section from “Basin and upper lock at Jones' Falls, from the East Upper end of 3rd lock, works nearly completed” by Thomas Burrowes, October 1831, Archives of Ontario, C 1-0-0-0-55.
By the time the Rideau Canal construction started in 1826-27, malaria was well established throughout much of the range of the anopheles mosquito in Ontario. However, the building of construction camps, putting dozens to hundreds of people in close proximity, in areas populated by the anopheles mosquito (whose highest numbers were in the southern part of the Rideau), meant an explosion of the disease. The summer of 1828 saw the first great outbreak of malaria in the southern construction camps. The period from August 1 to September 15 of each year became known as the “sickly season.” About 60% of the men would annually get sick with malaria. It eventually led to many men abandoning the work sites during that period of the year.

Rideau Canal contractor John Redpath, in a letter written from Jones Falls on December 3, 1831, referenced malaria, stating: “the exceeding unhealthiness of the place from which cause all engaged in it suffered much from lake fever and fever & ague, and it has also retarded the work for about three months each year. I caught the disease both the first [1828] and second year missed the third but this year had a severe attack of Lake Fever – which kept me to bed for two months and nearly two months more before I was fit for active service as nothing can compensate for the worse of health so no inducement whatever would stimulate one to a similar undertaking.” Redpath was noting that his workforce, primarily Scots and French Canadians, were all laid low by malaria. Ironically, in 1834, Redpath brought his family to his sister’s house at Jones Falls, in order to escape the deadly cholera epidemic (which killed his wife), that was raging at that time in Montreal.

In 1829, John MacTaggart, in referencing the first major malaria outbreak in the summer of 1828, wrote that “at the Rideau Canal few could work with fever and ague; at Jones Falls and Kingston Mills, no one was able to carry a draught of water to a friend; doctors and all were laid down together.”

Malaria was not understood at the time, it was believed to be caused by bad air (hence “mal”-“aria” – literally “bad”-“air”). Colonel By had large sections of forest at the construction areas cleared to promote breezes in order to blow away this “bad air.”

The mystery of malaria during construction of the Rideau isn’t that it existed (it was present in Ontario long before the building of the Rideau Canal), but that so many died from it. Today, P. vivax has essentially a 0% mortality rate because P.vivax infects far fewer blood cells than other forms of malaria. People get sick from P.vivax, but they don’t die. However the number of deaths reported from the canal construction period shows a direct death rate of about 1.5% at the lockstations, which might be extrapolated up to 3% to account for deaths off-site. We don’t have exact (or even good rough) numbers for how many people worked on the canal – but an educated guess, using the higher 3% figure, is that 375 to 600 workers may have died from malaria. This doesn’t include women and children who died from malaria in apparently similar numbers. For instance, in 1830, in the area from Newboro to Kingston Mills, out of a total of 1,316 men, 787 got sick and 27 died. At the same time, 13 women and 15 children were also recorded as having died.

To account for the death rate, the most likely explanation is that other diseases and heath issues of the day, such as dysentery, played a role. It may have been that P vivax was fatal to someone already suffering from another disease or health problem. A less likely explanation is that the more virulent tropical malaria, P. falciparum, was also present. Introduced into the U.S. with the African slave trade, it doesn’t have the ability to over-winter in Canada, so, if it was present, it must have been re-introduced each year. John Redpath makes a distinction between “lake fever” and “fever & ague” so perhaps he was referencing different forms of malaria, or perhaps malaria complicated by another disease or health issue.

Although cinchona bark (containing quinine) had been in use for years as a treatment for malaria, it was the invention of quinoline alkaloid (named ‘Quinine’), in 1820, that provided the first highly potent anti-malarial drug. But at the time of the building of the Rideau Canal it was very difficult to obtain and its use was therefore limited.

Malaria was eradicated from Ontario by the end of the 1800s. This was done by reducing the numbers of malaria parasites to a point low enough to break the cycle (the classic case example of how this can be done was the U.S. construction of the Panama Canal).

Extensive use of Quinine by the mid-1800s acted as a prophylactic for the disease (there are stories from that period of children going to school, “buzzed” on their morning dose of Quinine). The addition of glass, and eventually screens, on doors and windows, to prevent the entry of mosquitoes at night, reduced the rate of infection. Swamps were drained, reducing mosquito breeding habitat in areas of human habitation. This all took place, essentially eradicating malaria in Ontario, before it was scientifically recognized, in the late 1800s, that mosquitoes were the carrier of the disease.

A number of myths and misconceptions have grown up around malaria on the Rideau, I’ll try to dispel some of these:

Mythconception #1 – malaria was unique to the construction of the Rideau Canal. No, it was present in Ontario before and after the building of the Rideau and present at similar large construction projects of the period (i.e. the building of the Erie Canal). The Rideau was not unique.

Mythconception #2 – Colonel By stopped recording the number of deaths. No, records were kept for the entire construction period once malaria was recognized as a problem (1828-1831).

Mythconception #3 – malaria affected Irish labourers more than other workers. No, malaria was indiscriminate, it affected everyone. One of the hardest hit places was Jones Falls, which didn’t employ Irish labourers. Direct numbers from the records show that the Royal Sappers and Miners took the hardest hit percentage wise, but the records are fragmented so no conclusions can reliably be drawn.

Mythconception #4 – British soldiers who had served in tropical countries caused the malaria on the Rideau. No, we’ve already seen that malaria was present in the area long before the construction of the canal. The soldiers who worked on the Rideau Canal were Companies raised in Britain (where the temperate form of malaria existed in marshland regions). Yes, a few could have been infected with tropical malaria from previous postings – but their low numbers were not sufficient to start up a malaria cycle.

The bottom line is that malaria was the single largest cause of death during the construction of the canal. The Rideau Canal, similar to other “megaprojects” of the period, is a monument to human sweat, toil, death and perseverance. It’s well worth celebrating since civilizations were built on such projects and the building of the Rideau Canal helped Canada advance into nationhood.

Note: While malaria isn’t a problem in Canada today, it kills over 1 million people worldwide every year, mostly in developing nations. Most of the deaths are caused by the species P. falciparum.

- Ken Watson

For more about malaria on the Rideau - see the malaria section from my book, A History of the Rideau Lockstations.

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©1996- Ken W. Watson