Human plague in Cambodia v2 · 2016. 9. 20. · East during the Crusades and the ensuing Second...

Unité d’Epidémiologie et de Santé Publique Institut Pasteur du Cambodge

5, Bvd. Monivong, BP 983 - Phnom Penh, Royaume du Cambodge

Human plague in Cambodia A critical review of historical data found in the literature

Critical review of historical data on plague in Cambodia Institut Pasteur du Cambodge, April 2011

/ 21

Foreword

At a meeting of the national technical working group on zoonoses in February 2011, Cambodian animal and human health authorities discussed plague as a priority for future research and surveillance in Cambodia. To our knowledge, there was no data on plague available in Cambodia at that time.

In collaboration with the Bacteriology Unit, the Epidemiology and Public Health Unit of the Institut Pasteur in Cambodia has compiled published data to document the characteristics of historic epidemics and possible foci in Cambodia.

The data and sources presented here originate from the collection of notes and publications, in the literature and elsewhere, collected throughout the years at the Yersinia Laboratory of the Institut Pasteur in Paris, France.

Source material compilation, analysis and this synthesis were performed by Dr. A. Tarantola at the Epidemiology and Public Health Unit at the Institut Pasteur of Cambodia in April, 2011.

We wish to gratefully acknowledge Dr .Elisabeth Carniel of the Yersinia Research Unit, National Reference Laboratory and WHO Collaborating Center for Yersinia, Institut Pasteur in Paris, France for her permission to access and use archives available in her laboratory.

Phnom Penh, April 2011

Arnaud Tarantola, MD, Msc Head, Epidemiology and Public Heath Unit Institut Pasteur du Cambodge Mobile: +855 (0) 12 333 650 Tel: +855 (0) 23 426 009 Fax: +855 (0) 23 725 606 Email: [email protected]


/ 21

Table of contents

FOREWORD ...................................................................................................................................................................................................... 2 TABLE OF CONTENTS ........................................................................................................................................................................................ 3

INTRODUCTION ................................................................................................................................................................................................ 4

CAUSATIVE PATHOGEN AND TRANSMISSION ...................................................................................................................................................... 4 CLINICAL PRESENTATION IN HUMANS ................................................................................................................................................................ 4 HISTORICAL ASPECTS OF PLAGUE EPIDEMICS AND PANDEMICS ......................................................................................................................... 4 IDENTIFIED PLAGUE FOCI IN SOUTH-EAST ASIA ................................................................................................................................................. 5 SEASONALITY DESCRIBED IN ESTABLISHED SOUTH-EAST ASIAN FOCI ............................................................................................................... 5

AVAILABLE DATA ON PLAGUE OUTBREAKS IN CAMBODIA ................................................................................................................ 5

THE FIRST EPIDEMIC, 1907-1908 ..................................................................................................................................................................... 5 Available epidemiological data ................................................................................................................................................................. 5 Social disruption ........................................................................................................................................................................................ 6

AFTER THE FIRST EPIDEMIC: 1909 – 1921 ........................................................................................................................................................ 7 Urbanization, hygiene and rodent control efforts ..................................................................................................................................... 7 Epidemiological data ................................................................................................................................................................................. 8

THE PLAGUE EPIDEMIC IN PHNOM PENH AND ENSUING PERIOD, 1922-1929 ..................................................................................................... 9 Detecting plague cases............................................................................................................................................................................. 9 Confirming plague cases by liver biopsies ............................................................................................................................................. 10

Rationale ......................................................................................................................................................................................................................... 10 Limitations of liver biopsies analysis ............................................................................................................................................................................. 10

POST-EPIDEMIC PERIOD 1930-1945 ............................................................................................................................................................... 11 Caseload .................................................................................................................................................................................................. 11 Other diagnostic approaches.................................................................................................................................................................. 11

FROM 1946 TO PRESENT ................................................................................................................................................................................ 11 OVERALL CHARACTERISTICS OF PLAGUE TRANSMISSION IN CAMBODIA ........................................................................................................... 13

Monthly distribution ................................................................................................................................................................................. 13 Ethnicity of cases..................................................................................................................................................................................... 13 Location of described outbreaks ............................................................................................................................................................ 14

DISCUSSION .................................................................................................................................................................................................... 14

BIBLIOGRAPHICAL REFERENCES ............................................................................................................................................................ 16

ANNEX : AVAILABLE DATA ON HUMAN PLAGUE IN CAMBODIA, 1907 - PRESENT ....................................................................... 17

ANNEX : MAP OF PHNOM PENH AT THE TURN OF THE XXTH CENTURY ......................................................................................... 18

ANNEX : ICONOGRAPHY OF PHNOM PENH AT THE TURN OF THE XXTH CENTURY .................................................................... 18

Please cite as:

Tarantola A. Human plague in Cambodia: A critical review of historical data found in the literature. Institut Pasteur du Cambodge; Phnom Penh, April 2011.


/ 21

Introduction

Causative pathogen and transmission

Plague is a bacterial zoonosis transmissible to humans. The causative pathogen is an enterobacteria named after its discoverer, Dr. Alexandre Yersin of the Institut Pasteur in Nha Trang, who identified it in 1894 during an outbreak in Hong Kong1-3 which threatened the French colonies in Indochina.

As shown in 1898 by Paul-Louis Simond of the Institut Pasteur 4, Yersinia pestis is spread by fleas5 and causes a disease of small animals. Transmission to humans is rare and usually limited in or around plague foci. In modern times, larger epidemics have been due to flea-infested rats and humans living in high density and close proximity, sometimes with secondary human-to-human transmission through infected droplets, which remains rare6-9.

Clinical presentation in humans

Humans may become infected through the bite of a flea5, through inhalation of infectious droplets or through contact with contaminated blood or body fluids. Prognosis is usually favorable if diagnosis is prompt and if adapted antibiotic treatment is administered in timely fashion.

Table 1: Summary of clinical characteristics of various forms of symptomatic infection by Y. pestis in humans

(adapted from Dit-InVS10)

Clinical forms Bubonic Septicemic Pulmonary Incubation 3- days A few hours to 3 days % of forms 93% of cases in Madagascar

81% in USA 15% of cases in USA 3% of cases in USA

Case fatality rate without adapted and timely treatment

50% - 90% ~100% ~100%

Direct human to human transmission

No No Yes (infrequent)

Remarks Lymphadenopathy in the affected body part, secondary to flea bite or infected cut. May ulcerate and heal but usually progresses to septicemia and pulmonary form.

Following flea bite but often infected cut or animal bite

Usually secondary to bubonic/septicemic form. Primary if transmission through inhalation of bacteria or infected respiratory droplets.

Historical aspects of plague epidemics and pandemics

Plague foci are usually geographically delimited, giving rise to sporadic cases or epidemics which can spread secondarily, even causing pandemics in humans11.

Yersinia pestis is thought to have emerged over 10,000 years ago5 12. The first historical traces mentioning “plague” outbreaks originate in the eastern Mediterranean. They date to the Plague Prayers attributed to Mursili II (ca. 1327-1295 B.C.E.), a Hittite ruler of a kingdom in present-day Turkey/Syria, or the first description of a mentioning rodents and referring to a “plague” which is reported to have affected the Philistines around 1320 BC (Samuel, 6:4-5)13. Biological confirmation is lacking, however, to definitively point to Yersinia pestis as the causative agent.


/ 21

Plague pandemics have occurred and caused massive mortality, usually during periods of opening routes and contacts between endemic and non-endemic areas11 : opening of the Eastern Roman Empire and the First Pandemic (the Justinian plague dated 541) 14; opening of contacts between Western Europe and the Middle-East during the Crusades and the ensuing Second Pandemic (the Black Plague dated 1347)11. The third pandemic12 is considered to have begun in Yunnan in the mid-1850s and spread through Hong Kong3 to the rest of the world, facilitated by trade routes operated by colonial powers.

Identified plague foci in South-East Asia

Since the 1950s, nearly 60% of plague cases reported to the World Health Organization (WHO) occurred in Asia, mainly in 10 Asian countries. Plague foci have historically been identified in South-East Asian countries, including Laos, Myanmar, Thailand and Vietnam13.

Periods of high plague activity has been described in South-East Asia in the mid-1960s, between 1973 and 1978, and the mid-1980s13. These data show that plague can remain quiescent for years or decades before reappearing and causing sporadic cases or more sizeable outbreaks, usually in or around established plague foci, as has been described in other countries15 16.

A period of high incidence was described between 1967 and 1971, principally in Vietnam which at the time accounted for 97% of Asian cases and 90% of the reported world total. This increase of outbreaks and cases in Vietnam during that period has been attributed to disruption caused by armed conflict, perhaps specifically by defoliation13.

Since the early 1980s, plague cases and deaths have been reported from Myanmar13 17 18, principally from Magway, Mandalay and Sagaing Divisions. In Vietnam13 18-20, human plague cases are reported from Central provinces and the Tay–Nguyen Plateau. In 1985 the disease was notified in Ho Chi Minh City.

Seasonality described in established South-East Asian foci

In Vietnam, human plague cases usually occur during the dry season with a peak in April–June, while in Myanmar the highest incidence is during the cold season (November to March) with a peak in January or February13.

There are no ancient sources evocative of plague in Cambodia, and there does not seem to be a traditional Khmer term to designate bubonic or pulmonary plague21.

Available data on Plague outbreaks in Cambodia

The first epidemic, 1907-1908

Available epidemiological data

The first identified case of human plague in Cambodia was documented by Dr. Lannelongue, on June 2, 1907. The case was a worker on Phnom Penh river harbor22 , a longtime resident of the Chinese area, near the old market, located next to the Ounalom pagoda21. According to other sources, the first case occurred in a Vietnamese-born non-commissioned officer of the French militia23. A map of Phnom Penh dated ca. 1910 is presented in annex.


/ 21

During the five months elapsed from the start of the epidemic in June 1907 to October 1907, a conservative estimate of 87 cases, including 83 deaths (CFR 96%), were registered, mostly in Phnom Penh’s Chinese district, while other limited outbreaks were also notified in the Khmer and Vietnamese (“Annamite”) areas23 24. At the time, the population of the entire city of Phnom Penh was estimated at nearly 50 000 inhabitants23. The number of cases and estimated population and attack rates are shown below.

Table 2: Estimated number of 86 notified plague cases and attack rates, by ethnic group, Phnom Penh, 190723.

*The number of Khmer deaths is certainly underestimated

The epidemic then suddenly abated, the last notified death being confirmed on September 30, 1907 21 23.

It reappeared on January 6, 1908 when it caused the death of a young monk in the royal palace area. Other constantly fatal cases occurred in other city districts (seven in January, seven in February, 18 in March, 11 in April, 30 in May including three in the palace of the Prime Minister, who did not notify health authorities), reaching its acme in September before slowing down and ending in December of the same year21. In all, 253 cases were notified and recorded in 1908 in Phnom Penh, including 242 deaths (CFR 96%) 23 24.

Social disruption

The intensity of the 1907-1908 epidemic led King Sisowath to initially consider French colonial authorities suggestion of (overly?) strict control measures. However, the king then turned about and strongly opposed compulsory notification of all suspect cases22. A thorough description and discussion of the historical context and event can be found in the literature23.

Control efforts were faced by the hostility of the population and of the aristocracy. Pigs around affected homes were initially culled, threatening the population’s livelihood23. The population also feared that corpses would be desecrated by autopsies and postmortem samples, that houses and belongings of the deceased would be burned down and funeral rites would not be observed22. Corpses suspected of plague could, however, only be accessed and deaths notified by French physicians if they were accompanied by a delegate of the ministry of the interior. Houses could only be destroyed and burned after authorization from the Mandarin22. French authors of the time accuse the royal heirs to have stoked discontent as they were strongly opposed to the colonial authorities of the French “protectorate”. Modern authors view the reaction as an understandable one considering the stringent control measures, their limited effects and the political and social struggle of the time23.

In April 1908, plague emerged within the compound of the royal palace itself, which was to become a focus of plague infection and a source of dissent vis à vis the colonial powers23. Lady Preng, one of the concubines of the king's son, Prince Duong Mathura, fell ill with plague and died. The Prince and his sister, Princess Sopha Dy, formally forbade the French physician to examine the body which was promptly cremated. Despite condoning

Ethnicity N cases Estimated pop. Cases p. 10 000

Chinese 78 16,000 48.7

Khmer* 3 22,000 1.4

"Annamite" 5 11,000 4.5

Europeans 0 1,000 0.0

Total 86 50,000 17.2


/ 21

this attitude and against French demands, King Sisowath nevertheless ordered that the house of the Prince be demolished and burned publicly.

Angered by this act and the refusal of French authorities for financial compensation, Prince Duong Mathura gathered 1500 to 2000 protesters in front of the royal palace on April 18, 1908, to demand that mandatory notification of deaths instituted by French colonial authorities be abolished22 23. King Sisowath asked for a reprieve and for the French resident to attend a meeting three days later during which the same protests occurred, taking a violent turn23.

Angered by these manifestations, the highest French colonial representative declared that from now on the French health authorities would no longer be concerned with the Cambodian population. Although this was welcomed with enthusiasm by the crowd, it severely hindered control efforts during at least one month22 23. The partisans of Prince Duong Mathura are said to have offered a bounty of 200 piastres on the heads of the French physicians who tried to control plague22.

The number of plague cases rose, this time visibly among the Khmer aristocracy. Prince Duong Mathura himself died of plague some weeks later25. Deeply aggrieved by the death of his favorite son and heir apparent, King Sisowath decided that he and the rest of the court would be vaccinated against plague in August of 1908.

Figure 1: A view of the Royal palace in Phnom Penh in the 1920s.

After the first epidemic: 1909 – 1921

Urbanization, hygiene and rodent control efforts

In 1915, Yersinia pestis bacillus was identified in a shrew (Crocidura murina) found dead in the home of a deceased plague case in the Chinese quarter of the city of Phnom Penh26. This shrew was highly infested by oriental rat fleas (Xenopsylla cheopsis).

Rat infestation was intense in the Chinese-style shophouses of what was then the Chinese quarter of Phnom Penh. This densely populated area composed of Chinese shophouses with a high population density and lack of sanitation, especially at the back of the shophouses, was considered the epicenter of each outbreak in the city.

After the first cases were diagnosed, sanitation and vector control was intensified. The number of workers at the rodent control department increased to 16 workers, equipped with rat-hunting dogs, who were paid a bonus with


/ 21

each rat the killed23. In 1913, French authors report that 97 rodents had been caught, while there were 66,000, 81,000, and 19 9000 captures in 1919, 1920 and 1921, respectively27.

In July 1922, health and sanitation officers recommended that27:

1. The sanitation and water evacuation system be completed 2. Houses, especially in the Chinese quarter, be connected to the waste elimination system and toilets,

and that domestic waste be incinerated and the garbage dump be relocated outside the city 3. The Ounalom pagoda be considered to be a focus of infection at the heart of the city and cleaned out

thoroughly 4. Docks and warehouses be built at a distance from the city center, in which traders would be made to

stock their rice, hides, cotton, smoked fish etc. The cement walls and floors of the construction aimed at preventing rat infestation.

5. The Verneville canal be filled in 6. Building new houses on remaining free space of the Chinese quarter be forbidden 7. The central market be moved in order to decongest the Chinese area 8. (So-called) parasite constructions be demolished. 9. Some streets and alleys be enlarged and new ones be created.

Figure 2: A view of Phnom Penh in the early 1900s (Source: Postcardman.net).

Epidemiological data

The municipal health authorities of the city of Phnom Penh continued active surveillance and control efforts. Sporadic cases nevertheless continued to occur each year in the capital city and secondary outbreaks were caused in several other cities in the country due to the exportation of cases.

In January 1909, plague cases appeared in Battambang and the epidemic lasted until April. There were another 184 suspect or confirmed plague cases reported in Cambodia during 1910.

In 1911, small outbreaks were described in Kompong Speu, Pursat, Kompong Thom and Svay Rieng30. These outbreaks were linked with secondary transmission around cases exported from Phnom Penh. A more sizable epidemic occurred in Kompong Cham, with 44 deaths. In that city, a plague case which had fled Phnom Penh was left dying at the steps of Man Dap pagoda. Plague killed all the monks in that pagoda and all the inhabitants of nearby houses who in turn provided care to the monks themselves22.


/ 21

At that time, at least two cases of bubonic plague also caused limited outbreaks of pneumonic plague in Prey Veng and in Bassac22.

In 1913, the Phnom Penh royal palace was once again struck by plague, killing one Prince and two princesses, and approximately 10 musicians and singers22.

In 1915, in the small island city of Koh Sotin, 15 of 21 inhabitants living in five houses came down with pneumonic plague and died22. Other pneumonic plague outbreaks were identified in Por Nang Chey and Koh Pen villages due to secondary transmission around a woman who had traveled and stayed in Phnom Penh for eight days. After her return, she felt ill and died the next day with signs of pneumonia. In total around 10 cases occurred, all fatal, in this small village which lost three fourths of its inhabitants22.

In 1919, with the exception of a single case which was notified in Kampot, all cases occurred in Phnom Penh. In succeeding years, all outbreaks outside of Phnom Penh were found to be linked with an imported case from the capital22.

The plague epidemic in Phnom Penh and ensuing period, 1922-1929

An intense epidemic occurred in Phnom Penh in 1922-1923 (Figure 3). Around that time, the estimated population of the city of Phnom Penh was 80,000 inhabitants31.

At the request of the governor general, Mr. Bernard (Director of the Pasteur Institute in Saigon), Mr. Pons (Head of the Laboratory) and Mr. Bartemellier (Entomologist at the University) conducted a one-month mission to Phnom Penh between July 5 two August 4, 192332. Available epidemiological data discussed in the literature are based on biological diagnoses which are discussed below.

In all, a total of 855 confirmed or suspected cases of human plague were reported for the year 1923 in Cambodia30, including 647 in Phnom Penh32. But these data are based to a large extent on liver biopsies analysis and are severely biased (see below).

Figure 3 : Available data on "plague cases" notified by health authorities of the French Protectorate, Cambodia, 1907-1929 32 21 24.

Detecting plague cases

At the time, any death that occurred in Phnom Penh was subjected to mandatory notification to the municipal health officer’s Bureau. An agent of the sanitary corps went to the home of the deceased and quickly

0

100

200

300

400

500

600

700

1907

1908

1909

1910

1911

1912

1913

1914

1915

1916

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929

Year

N s

uspe

cted

or c

onfir

med

pla

gue

case

s


/ 21

investigated on the presumed cause of death, the duration or symptoms of the disease. Based on these elements, the (French) health officer would then go to the house, examine the corpse and interview relatives before formally registering the death27.

Figure 4: Number of deaths attributed to plague documented for age in Phnom Penh, by age group, 1916-1923* (*of note, data for 1923 pertain only to the first 6 months)32.

Confirming plague cases by liver biopsies

Rationale

The population in Phnom Penh was extremely hostile to postmortem examinations carried out to isolate deep-seated axillary or inguinal buboes. French health officers during the protectorate therefore resorted to postmortem and limited sampling of liver tissue through a small abdominal incisions31 32. Liver samples were then forwarded by sanitary authorities to the microbiological laboratory in Phnom Penh for microbiological identification of Yersinia pestis.

Careful examination of the health registers compiled by the sanitary authorities in Phnom Penh found for instance that in 1921, 397 liver samples were taken from 2185 corpses 32.

Limitations of liver biopsies analysis

Unfortunately, this technique was flawed. Due to tissue conservation techniques at the time and ambient temperatures, liver tissue degraded and decomposed swiftly, leading to the proliferation of various bacteria which were morphologically comparable to Yersinia pestis31 32. Data were therefore highly biased: diagnosis was performed in a minority of fatal cases (as not every corpse was sampled, in part because the family hid deaths for fear of desecration), but certainly in excess (as the technique was not specific and gave false positive results).

During the scientific mission conducted in 1923 by Drs. Noël-Bernard and Pons33, 105 liver samples were examined after being taken in a total of 130 corpses. There is no data available to help determine the criteria used. During that mission, a certain number of confirmation tests were performed. Liver samples were examined

0

50

100

150

200

Age group (in years)

N d

eath

s attribute

d to

pla

gue 1916 1917 1918 1919

1920 1921 1922 1923

1916 7 9 7 38 63 17 3 0

1917 22 22 29 62 57 26 10 0

1918 32 35 32 111 118 57 13 1

1919 14 7 2 21 32 6 3 0

1920 47 32 23 48 55 23 1 0

1921 65 60 43 74 93 40 20 2

1922 161 136 49 76 104 73 31 10

1923 149 57 45 97 121 68 38 5

0-1 2-5 6-10 11-20 21-40 41-60 61-80 80+


/ 21

directly after Gram and Ziehl colorations. The samples had in most cases been taken 12 to 24 hours earlier. A second confirmation test was performed within 24 hours. Approximately 70% of liver samples were inoculated to guinea pigs and laboratory rats. Inoculation was carried out each time one of the following conditions was present:

1. initial test results were positive 2. initial test results were suspect 3. the liver had given rise to a positive coccobacillus culture within 24 hours 4. the corpse was considered suspect based on the declaration, the isolation, the behavior of the relatives

or of signs observed on the corpse 5. the death occurred in a contaminated house or area 6. outside of any suspicion, if the hygiene and sanitation services required it

In total, only nine of these 105 samples were finally confirmed for Yersinia pestis infection by the members of the investigating team. Among these nine, five had been taken from patients who had presented bubonic plague, and four from patients with no observable bubo32. Of note: according to the author, there was no case in children aged less than one32, contrary to what liver biopsy testing had initially suggested (Figure 4).

Post-epidemic period 1930-1945

Caseload

There are no available data on yearly case counts for Cambodia between 1930 and 1945, partly due to improved sanitation in Phnom Penh and a reduction in cases, partly also due to the disruption caused in the country and specifically the surveillance system by conflicts between the French “protectorate”, neighboring Thailand and later with Japanese invading forces.

Other diagnostic approaches

After the mission by Noël-Bernard and Pons in 1923, diagnoses were later confirmed in Phnom Penh by other methods. Through 1927, suspect liver samples which were positive or negative for direct microbial observation were applied to shaven skin of guinea pigs24. If the guinea pig died, a sample of blood taken from the heart was cultured. This new method was considered more specific to confirm plague. Through the year 1927, direct liver sample analysis diagnosed 83 cases of plague. The "guinea pig" method confirmed 50 among 82 cases in Phnom Penh.

From 1946 to present

After 1946, surveillance in Cambodia again identified plague cases in Cambodia in 1948 (Figure 5). Sporadic outbreaks continued to occur each year through 1957 (with no documented case in 1953) before declining progressively and ending in 1958. Between 1948 and 1957, a total of 113 plague cases including 34 deaths were notified in Cambodia30. Phnom Penh was affected each year but an increasing number of cases were documented in the Provinces of K. Speu, Kampot, Kandal, Prey Veng, Svay Rieng and Takeo.

Between March and May, 1955, 10 confirmed plague cases were identified in various localities of Svey Rieng province (Prasauth, Svey Rieng town, Svay-Yea, Kompong Chak)34 35. One suspected, unconfirmed case of human plague - as well as rat die off - were reported at the time from nearby Prey Veng province34.

Plague reappeared in 1971, during the conflict that destabilized the entire region. The following paragraphs are based principally on work published by B. Velimirovic of the World Health Organization30 36. In the last months of 1971 unofficial sources reported that some Cambodian nationals had sought treatment for plague on the other side of the border in South Vietnamese health structures. In September, 1971, two suspected cases of bubonic plague were reported in Svay Rieng province but were not investigated.


/ 21

On February 19, 1972 seven patients were hospitalized in Prey Veng provincial hospital with fever and lymphadenopathy. Four underwent blood samples, one of which returned positive for Yersinia pestis. One month later nine other clinically suspect cases were reported from Svay Rieng and six other deaths suspected of plague had been identified in Chipou, a village in Srok Svey near the Vietnamese border.

In early May 1972, an epidemic occurred in Svay Rieng town with about 15 to 20 cases per week and a total of 109 cases were documented and treated. Four cases died, all presenting bubonic plague. Three other suspect patients were sampled and were all culture-positive. At the time, the population of Svay Rieng which had been estimated at 20,000 had increased to about 70,000 inhabitants, reaching 100,000 inhabitants by the end of August 1972. Control and case management were a major challenge amid the intense fighting and in an encircled town. The epidemic nevertheless ended soon after that and no cases were seen after July 15, but plague cases were again documented in June of 1973.

In Phnom Penh, a town whose population had grown from 300,000 to about 1 million with an influx of refugees, two brothers living in the Vth quarter were admitted in early July 1972 with pneumonic, biologically confirmed plague (mice inoculation test and culture). There are no further data regarding transmission in Phnom Penh.

Since 1973 there is no data pertaining to human plague in Cambodia.

Figure 5: Reported human plague cases in Cambodia, 1946-1972.

0

20

40

60

80

100

120

140

1946

1947

1948

1949

1950

1951

1952

1953

1954

1955

1956

1957

1958

1959

1960

1961

1962

1963

1964

1965

1966

1967

1968

1969

1970

1971

1972

Year

N s

uspe

cted

or c

onfir

med

pla

gue

case

s


/ 21

Overall characteristics of plague transmission in Cambodia

Monthly distribution

One of the authors mentions that the epidemic does not occur systematically at the same time of the year, but usually occurs around December22, taking two to three months to reach its acme and ends within a few days after that. Perhaps the author had access to surveillance reports but this conclusion cannot be substantiated by published data.

The epidemiological data available on the seasonal trends of plague epidemics in Cambodia seems inconclusive, in part because yearly data are dwarfed by that of the intense 1907-1908 and 1922-1923 epidemics in Phnom Penh. Sparse data from confirmation testing on guinea pigs in 1927 in Phnom Penh show that most of the transmission occurred between May and September of that year24.

Figure 6: Confirmed plague cases, by month, Phnom Penh, 1927 24.

Ethnicity of cases

The (sparse) 1927 data is also available by ethnic group.

Table 3: Confirmed plague cases, by ethnic group and with ethnic denominators, Phnom Penh, 192724.

There are no other historical data to corroborate this distribution by ethnic group.

0

2

4

6

8

10

12

Jan

.

Fe

b

Ma

r

Ap

r

Ma

y

Jun

Jul

Au

g

Se

p

Oct

No

v

De

c

Month of year 1927

N c

on

firm

ed

ca

se

s

Ethnicity N cases Estimated pop. Cases p. 10 000

Chinese 34 26,000 13.08

Khmer 10 34,000 2.94

"Annamite" 6 20,000 3.00

Total 50 80,000 6.25


/ 21

Location of described outbreaks

Figure 7: Location and year of documented plague outbreaks in Cambodia, 1907-197330.

In April, 2010, around Khmer New Year, a case of plague was suspected in Siem Reap. Samples were sent to the Institut Pasteur in Paris with assistance from Institut Pasteur in Cambodia. Tests were also sent from Institut Pasteur in Madagascar for field testing around the suspect case in Cambodia. All tests returned negative and the patient is not considered a plague case.

Discussion

Plague seems to have been introduced for the first time at an early stage following the onset of the Third Pandemic. This was probably facilitated by colonial trade routes during the French Protectorate.

Following its emergence and probable introduction, plague caused outbreaks in densely populated areas of Cambodia, first in Phnom Penh then in other cities and villages around exported cases. The focus of plague during these early years was the so-called “Chinese quarter” - in an area located around Ounalom pagoda – and later in the Royal Palace in Phnom Penh. Transmission was endemic and cases were documented yearly.

Available historical data point to outbreaks outside Phnom Penh being secondary to exported cases from Phnom Penh until the 1960s. The cases which occurred in Svay Rieng and Preyveng in the mid-1950s and


/ 21

again in 1971-73, however, may have occurred in connection with established foci in nearby Vietnam, especially during the Vietnamese conflict.

A surveillance bias may lead to detection of cases only in cities, and there is no veterinary data regarding rat die-off. However, significant outbreaks occurring in Cambodia would probably have been detected, as they were in 1955 and again in difficult circumstances in 1971.

The vast majority of cases were bubonic in form, but limited outbreaks of pneumonic plague caused high case-fatality rates. Available data show that the CFR became lower in the 1960s and 1970s, as antibiotics became available. Even some severe cases managed in a hospital setting survived, as described in other resource-poor settings37.

Plague surveillance based on liver samples analysis in Phnom Penh is deeply biased and provides unreliable historical data which is difficult to interpret. Initially, biological tests and the technique used for case confirmation were both incomplete, as all corpses were not sampled, and estimate cases in excess due to misinterpretation of bacteriological results. Although “lab confirmed” data of the time cannot ascertain the exact caseload during that epidemic in Phnom Penh, however, it may help identify trends and especially seasonality. Syndromic surveillance data on suspected plague cases with documented buboes in areas in and especially outside of Phnom Penh may be more reliable to identify outbreak onsets and durations.

Enzootic and local transmission of plague in Phnom Penh seems to have progressively disappeared through the improvement in sanitation, hygiene and urbanization undertaken after the 1908 epidemic and continued after the 1923 epidemic. The situation in 1971, however, seems quite different in that outbreaks occurred in very particular situations in refugee populations and in provinces forming an ecological continuum with identified plague foci in South Vietnam.

The few cases described between 1948 and 1957 are quizzical. These occurred after a period of about 20 years with no cases in or around Phnom Penh according to available data. In spite of World War II and the profound changes in the stability of the Colonial authorities, sanitation had improved in Phnom Penh and the public health system remained rather stable. The question remains whether the prolonged epidemiological silence which preceded and followed that 9-year period of enhanced plague circulation was due to lack of cases or lack of surveillance.

In conclusion, Cambodia is set in a region with established foci in at least two countries with which it shares borders and ecosystems. Although there is little data and no evidence to support the hypothesis of an established plague focus in Cambodia, health care workers working in areas bordering Vietnam should be trained to suspect plague in acute febrile cases, especially if they present lymphadenopathy.

As with other activities to support the Cambodian health authorities, the Pasteur Institute of Cambodia will maintain surveillance activities, remain attentive to the occurrence of suspected plague cases and maintain first-line confirmation capacity and links to reference centers.


/ 21

Bibliographical references

1. Yersin A. La peste bubonique à Hong Kong. Ann Inst Pasteur Paris 1894;8:662-7. 2. Bibel DJ, Chen TH. Diagnosis of Plague: an Analysis of the Yersin-Kitasato Controversy. Bacteriol Rev. 1976;40(3):633-451. 3. Pryor EG. The great plague of Hong Kong. J Hong Kong Branch R Asiat Soc 1975;15:61-70. 4. Simond M, Godley ML, Mouriquand PDE. Paul-Louis SImond and his discovery of plague transmission by rat fleas: a centenary. J R Soc Med

1998;91:101-104. 5. Hinnebusch BJ. The evolution of flea-borne transmission in Yersinia pestis. Curr Issues Mol Biol 2005;7(2):197-212. 6. Nishiura H. Epidemiology of a primary pneumonic plague in Kantoshu, Manchuria, from 1910 to 1911: statistical analysis of individual records

collected by the Japanese Empire. Int J Epidemiol 2006;35(4):1059-65. 7. Kool JL. Risk of person-to-person transmission of pneumonic plague. Clin Infect Dis 2005;40(8):1166-72. 8. Gani R, Leach S. Epidemiologic determinants for modeling pneumonic plague outbreaks. Emerg Infect Dis 2004;10(4):608-14. 9. Begier EM, Asiki G, Anywaine Z, Yockey B, Schriefer ME, Aleti P, et al. Pneumonic plague cluster, Uganda, 2004. Emerg Infect Dis

2006;12(3):460-7. 10. Dit-InVS. Peste: Situation mondiale, 8 janvier 2008. In: InVS, editor. Note de Veille Internationale. Saint-Maurice, 2008. 11. Khan IA. Plague: the dreadful visitation occupying the human mind for centuries. Trans R Soc Trop Med Hyg 2004;98(5):270-7. 12. Achtman M, Morelli G, Zhu P, Wirth T, Diehl I, Kusecek B, et al. Microevolution and history of the plague bacillus, Yersinia pestis. Proc Natl

Acad Sci U S A 2004;101(51):17837-42. 13. WHO. Plague manual: epidemiology, distribution, surveillance and control, 1999. 14. Dattwyler RJ. Book review: Justinian's Flea: Plague, Empire, and the Birth of Europe / Plague and the End of Antiquity: The Pandemic of 541–

750. N Engl J Med 2007;357::1354-1355. 15. Bertherat E, Bekhoucha S, Chougrani S, Razik F, Duchemin JB, Houti L, et al. Plague reappearance in Algeria after 50 years, 2003. Emerg

Infect Dis 2007;13(10):1459-62. 16. Tarantola A, Mollet T, Gueguen J, Barboza P, Bertherat E. Plague outbreak in the Libyan Arab Jamahiriya. Euro Surveill 2009;14(26). 17. Thaung U, Kyi KM, Maung Sein M, San Myint D, Sein Win U, Hein R, et al. An outbreak of plague in Hlegu, Burma in 1977. Southeast Asian J

Trop Med Public Health 1978;9(3):390-7. 18. Human plague in 1992. Wkly Epidemiol Rec 1994;69(2):8-10. 19. Olson WP. Rat-flea indices, rainfall, and plague outbreaks in Vietnam, with emphasis on the Pleiku area. Am J Trop Med Hyg 1969;18(4):621-

8. 20. Suntsov VV, Huong LT, Suntsova NI, Gratz NG. Plague foci in Viet Nam: zoological and parasitological aspects. Bull World Health Organ

1997;75(2):117-23. 21. Chum C. Histoire de la peste au Cambodge. Séminaire sur les maladies transmissibles choléra - peste. Phnom Penh: OMS, 1972. 22. Gaide L, Bodet. La peste en Indochine. Hanoi: Imprimerie d'Extrême-Orient, 1930. 23. Au S. Indigenous politics, public health and the Cambodian colonial state. South East Asia Res 2006;14(1):33-86. 24. Gambier A. La peste au Cambodge. Bul Soc Path Exot 1928;21(7):497-503. 25. Vaccinate a King. The New York Times 1908 23/08/1908. 26. Kerandel J. Insectivore réservoir de la peste au Cambodge. Bul Soc Path Exot 1915;8(2):54-57. 27. Mathis C. La lutte contre la peste à Phnom Penh (Cambodge). Bul Soc Path Exot 1923;16(9):668-675. 28. Too A. The Chinese shophouse. Encyclopedia of Malaysia Editions Didier Millet 1998. 29. Lee HY. Pre-war Tong Lau: A Hong Kong Shophouse Typology. Hong Kong: Architectural Conservation Programme (ACP), Faculty of

Architecture, The University of Hong Kong, 2010. 30. Velimirovic B. Reappearance of plague in Khmer Republic (formerly Cambodia). Z Tropenmed Parasitol 1973;24(3):265-70. 31. LeCousse E. Recherches sur la Peste au Cambodge en 1924 poursuivies au laboratoire de Pnôm-Pênh. Bul Soc Path Exot 1925;18:630-632. 32. Noël-Bernard P, Pons R. Recherches sur les formes anormales de la peste au Cambodge et en Cochinchine. Bul Soc Path Exot

1924;17(1):39-67. 33. P.Noël-Bernard, Pons R. Recherches sur les formes anormales de la peste au Cambodge et en Cochinchine. Bul Soc Path Exot

1924;17(1):39-67. 34. Pull JH. Lutte contre la peste: compte-rendu sur la tournée effectuée le 1er Juin 1955 dans la région de Svay Rieng. Phnom Penh: WHO,

1955:3. 35. Compte-rendu sur la lutte contre la peste déclarée à Svay Rieng: Le Médecin-Chef de la Circonscription Médicale, 1955:2. 36. Velimirovic B. Plague in South-East Asia. A brief historical summary and present geographical distribution. Trans R Soc Trop Med Hyg

1972;66(3):479-504. 37. Boisier P, Rahalison L, Rasolomaharo M, Ratsitorahina M, Mahafaly M, Razafimahefa M, et al. Epidemiologic features of four successive

annual outbreaks of bubonic plague in Mahajanga, Madagascar. Emerg Infect Dis 2002;8(3):311-6.


/ 21

Annex : Available data on human plague in Cambodia, 1907 - present


/ 21

Annex : map of Phnom Penh at the turn of the XXth Century

Source: Au, S. Indigenous politics, public health and the Cambodian colonial state South East Asia Research, Volume 14, Number 1, March 2006 , pp. 33-86

Annex : iconography of Phnom Penh at the turn of the XXth Century

Source: http://www.postcardman.net/cambodia.html


/ 21

Human plague in Cambodia v2 · 2016. 9. 20. · East during the Crusades and the ensuing Second...

Documents

Transcript of Human plague in Cambodia v2 · 2016. 9. 20. · East during the Crusades and the ensuing Second...