---------------------------------------------------------------------------
Emerging Infectious Diseases * Volume 2 * Number 4 * October-December 1996
---------------------------------------------------------------------------
Letters

Emerging Infectious Diseases and the Depopulation of French Polynesia in
the 19th Century

---------------------------------------------------------------------------


To the Editor: The same dynamics now considered factors in the emergence of
infectious diseases may have been involved in the dramatic depopulation of
French Polynesia in the 19th century. Temporal and geographic variation in
the frequency and severity of infectious diseases are the result of the
encounter and interaction of a population of parasites and a population of
hosts. J. Musser reviewed the "bacterial side of the equation" (1). On the
host side, there are two historical models that describe the influence of
parasitism on human populations (2-4): 1) the South American model, in
which new pathogens were introduced into native populations by the European
conquistadores, causing the death of 50 million people; and 2) the African
model, in which infectious diseases present in native populations protected
them from the effects of colonization until modern times when the discovery
of quinine and other efficient antipathogenic drugs provided added
protection. The second model is well illustrated by the attempted
colonization of Madagascar, where the French lost five men to war and 5,000
to malaria (2). This letter intends to illustrate the first model. We
suggest that during their first contacts with European navigators in the
very late 18th century and the 19th century, Polynesian islanders, much
like populations in the South American model, were decimated by newly
introduced infectious diseases.

It is difficult to know precisely which infectious diseases were present in
Tahiti and the other French Polynesian islands before the arrival of the
first Europeans. However, a study of Polynesian languages indicates that
Bancroftian filariasis and leprosy were already present, while syphilis and
other venereal diseases, influenza, and tuberculosis (TB) were probably
unknown. Epidemic diarrhea and dysenteriae could have existed, although
first reports mentioned that the oldest Polynesians "never heard of
dysenteriae before" (5). In the Marquesian language, names exist for
leprosy, bronchitis, abscesses, and impetigo.

The number of inhabitants in Tahiti, as well as in the Marquesas and the
Austral Archipelago, was at first only estimated by European explorers.
However, a precise census was performed as soon as missionaries and French
authorities noted the high death rates in most of the islands (5,7,15,16).
Tahiti was annexed by France in 1843; the first census was performed in
1848, and the population size was assessed approximately every 5 years
until 1911.

Four major epidemic diseases (TB, typhoid, influenza, and smallpox)
devastated the Marquesas from 1791 to 1863/64; approximately 80% of the
population died. During that period, exchange of populations between the
Marquesas Islands also increased, as a consequence of colonization. Thus,
leprosy increased dramatically during the second half of the 19th century,
to a prevalence of 4.11% in 1884 (6).

In Rapa, the remote, southern island of the Austral Archipelago, at least
three epidemics were reported, resulting in the loss of more than 90% of
the population. Although the cause of the first epidemic remained unknown,
dysenteriae and smallpox were identified as causes of the second and third
epidemics, respectively.

From Rapa, a missionary went to Mangareva in 1831 or 1832, and his visit
there was followed by an epidemic that the natives attributed "to his god."
He had to flee back to Rapa. The second recorded epidemic disease was
"Chinese scabies" in 1865, which decimated the child population. Then, the
warship "La Zélée" brought an epidemic of influenza in 1908. In 1910, TB
and leprosy were reported "to spread rapidly" (7), and in 1911, the ship
"La Gauloise" brought whooping cough to Mangareva.

In Tahiti and the Society Islands, the number and diversity of
international and interisland exchanges, involving numerous commercial
ships and whalers, make the origin of epidemics more difficult to trace.
                             [end of page 359]

However, at least five were reported successively in the Leeward Islands in
1843, 1848, 1854, and 1864 (7), and at least 11 in Tahiti: influenza (1772
to 1774), pulmonary TB (1775), dysentery following the passage of the ship
of Vancouver (1790), dysentery after the passage of the whaler "Britania"
(1807), disastrous influenza in 1820, whooping cough in 1840, smallpox in
1841, dysentery again in 1843, scarlet fever in 1847, measles in 1852-1854
(800 deaths were recorded) and typhoid fever after the passage of "La
Magicienne" in 1877 (8).

Almost without exception, authors attributed the dramatic depopulation of
French Polynesia during the 19th century to infectious diseases. Other
causes, such as alcohol, opium, local wars, infanticides, and even
orgiastic behavior were also mentioned as possible causes. Depopulation
occurred to a similar extent in other South Pacific countries (9), e.g.,
the Cook Islands, Hawaii, Tonga, Samoa, and particularly Fiji, where 50% of
the population died. Thus, after limited initial contact with persons
exposed to infectious diseases, most of the Polynesian populations died.
Why did it happen? Why were epidemics so intense and so severe? It is
unlikely that clones of bacteria, viruses, fungi, or parasites with
particularly high virulence were introduced into native populations since
the long crossing by sailing boats would have selected clones with lower
virulence. Moreover, epidemics are also intense and severe in animal
populations when new infectious agents are introduced. In Hawaii, the
introduction of Plasmodium from birds had catastrophic consequences for the
local fauna (10).

Host population factors that may influence the spread of an infectious
agent (i.e., the intensity of an epidemic) are diverse: 1) social
disruption was certainly a major cause for the increase of leprosy and TB
in the Marquesas during the 19th century: pacification of the archipelago
by Dupetit-Thouars changed traditional behavior and destroyed tribal
barriers against leprosy by permitting the development of interisland
exchanges, thus contributing to the spread of both leprosy (within the
Marquesas) and TB (from Tahiti to one Marquesas island, then between the
Marquesas) (11); 2) the absence of most infectious diseases in Polynesia
before the 18th century probably slowed the selection of behavioral methods
of prevention and the development of traditional medicine; 3) a small
population without exposure to infectious diseases would not have selected
resistance genes against nonexistent infectious agents; and 4) the lack of
population immunity probably had a major role in the spread of new
infectious agents.

Host population factors that can influence the virulence of parasites
(i.e., the severity of an epidemic) are less frequent. Successive epidemics
of closely related viruses or bacteria can enhance the severity of the
disease, as in dengue fever (12), or can inversely provide
cross-protection, as was suggested between yaws and syphilis (13), whose
causative organisms are almost indistinguishable. Reduced genetic
polymorphism of 19th century Polynesians who had no immunity to infectious
diseases could have contributed to the severity of epidemics in the South
Pacific, as it was speculated for South America (4,14).

Paul M. V. Martin* and Claude Combes†
*Institut Territorial de Recherches Médicales Louis Malardé, Papeete,
French Polynesia; and †Centre de Biologies et d'Ecologie Tropicale et
Méditerranéenne, Université de Perpignan, Perpignan, France

References

  1. Musser JM. Molecular population genetic analysis of emerged bacterial
     pathogens: selected insights. Emerging Infectious Diseases
     1996;2:1-17.
  2. Combes C. Interactions durables: écologie et évolution du parasitisme.
     Paris: Masson, 1995.
  3. Haldane JBS. Disease and evolution. Ricerca Scientifica Supplement
     1949;19:68-76.
  4. Black FL. Why did they die? Science 1992;258:1739-40.
  5. De Bovis E. Etat de la société tahitienne à l'arrivée des européens.
     Papeete: Société des Etudes Océaniennes, 1978.
  6. Clavel CL. Les Marquisiens. Arch Med Nav 1884;42:194-212.
  7. Toullelan PY. Tahiti colonial. Paris: Publication de la Sorbonne,
     1987.
  8. Vigneron E. Hommes et santé en Polynésie Française. Montpellier, 1991.
  9. Mac-Arthur N. Islands population of the Pacific. Canberra: Australian
     National University Press, 1968.
                                [end of page 360]

 10. van Ripper III C, Van Ripper SG, Lee Goff M, Laird M. The
     epizootiology and ecological significance of malaria in Hawaiian land
     birds. Ecological Monographs 1986;56:127-44.
 11. Buisson GPE. Les îles Marquises et les Marquisiens. Annales d'Hygiène
     et de Médecine Coloniales 1903;6:535-59.
 12. Halstead SB. Pathogenesis of Dengue: challenge to molecular biology.
     Science 1988;239:476-81.
 13. Turner TB. Studies on the relationship between yaws and syphilis.
     American Journal of Hygiene 1937;25:477-506.
 14. Garenne M, Aaby P. J Infect Dis 1990;161:1088.
 15. Rollin L. Moeurs et coutumes des anciens Maoris des îles Marquises.
     Papeete: Stepolde, 1974.
 16. Hanson A. Rapa, une île polynésienne hier et aujourd'hui. Paris:
     Publications de la Société des Océanistes, 1973.
 17. Vallaux F. Mangareva et les Gambier. Papeete: Etablissement
     Territorial d'Achats Groupés, 1994.

---------------------------------------------------------------------------