Mosquito control in Panama; the eradication of malaria and yellow fever in Cuba and Panama

Front matter

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V •? V A *

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Introduction

DRESIDENT^ ROOSEVELT early appreciated the fact that great as were the engineering difficulties to be surmounted in the making of the Panama Canal, the difficulties of sanitation would be fully as great, if not greater, and, before the first Canal Commission was appointed, he told a committee of the American Medical Association, the American Association for the Advancement of Science, and the New York Academy of Medicine, consisting of Doctor Welch and Doctor Osier of Baltimore, Doctor Musser of Philadelphia, Doctor Bryant of New York, and the writer, that it was his intention to seek for the best man in the world for the task, to pay him whatever would be necessary, and to give him full power. Fortunately, the man needed was found in the person of Colonel (now General) Gorgas, fresh from his triumphant cleaning up of Havana with the consequent elimination of yellow fever and malaria. General Gorgas took with him from Cuba to Panama a man who

iii iv Introduction

had been his right hand in the cleaning up of Havana, J. Al Le Prince, the author of this book.

The writer well remembers one morning when, before starting for Panama, General Gorgas and Mr. Le Prince called on him at his office in Washington to talk about mosquitoes, and the confidence which they felt of accomplishing their gigantic task was inspiring. He asked General Gorgas to have specimens of all the Panama mosquitoes sent to him for naming, and the General said, ' ' I will assign Mr. Le Prince to see that it is done." Upon which Mr. Le Prince remarked, "I will have to do it soon, Doctor, for in a year or so there will be no mosquitoes there ! ' '

The brilliant results of the work of General Gorgas and his assistants are now known over the whole civilized globe. It has been an objectlesson for the sanitarians of the world and has demonstrated the vitally important fact that it is possible for the white race to live healthfully in the tropics.

And now, the whole world wants to know how they did it. Every detail becomes of the greatest interest, and, in consequence, what Mr. Le Prince has written here will be not only of great practical importance as a guide to

Introduction v

future work of the same character, especially in the tropics, but also of permanent historic value.

L. 0. Howard.

Bureau of Entomology, U. S. Department of Agriculture.

CONTENTS PART I. ANTI-MALARIA CAMPAIGN

CHAPTER PAGE

I. — The Status of Knowledge of Anti- Malaria Work in 1904 and the Previous Campaign in Havana . 3

II. — The Situation on the Isthmus in 1904,

before American Occupation . 1 6

III. — Meteorological and Topographical Conditions. Topographical Changes and their Bearing on Isthmian Anopheles . . . 27

IV. — The Species of Anopheles on the

Isthmus ..... 43

V. — Anopheles Propagation Areas . . 55

VI. — Harboring Places and Food of

Anopheles .... 83

VII. — Flight and Attraction of Mosquitoes ...... 94

vii viii Contents

CHAPTER PAGE

VIII. — Attack on Propagation Areas by

Filling 115

IX. — Attack on Propagation Areas by *-" Drainage 122

X. — Attack on Propagation Areas by

Oiling 151

XI. — Attack on Propagation Areas by

Larvacides . . . .173

XII. — Attack on Propagation Areas and Adult Mosquitoes by Natural Enemies . . . . .180

XIII. — Attack on Propagation Areas by

Clearing Bodies of Water . 190

XIV. — Attack on Propagation Areas by ' — Removal of Jungle . . .195 c.

XV. — Screening and Practical Destruction of Adult Anopheles in Houses ..... 198

XVI. — The Results Accomplished by the

Anti-Malaria Campaign . .218

PART II. THE YELLOW FEVER CAMPAIGN I. — The Campaign in Havana . . .231

II. — The Situation on the Isthmus before

Sanitary Work was Started . 261

Contents ix

CHAPTER PAGE

III. — Geography, Meteorology, etc., and their Bearing on the Presence of Aedes Calopus .... 268

IV. — The First Sanitary Work Done in

Panama — Its Purpose . . .271

V. — The Anti-Yellow Fever Campaign

and its Results .... 293

VI. — Measures Taken to Keep the Isthmus Free from Yellow Fever . 306

VII. — The Value of Yellow Fever Eradication in the Construction of the Panama Canal . . .314

Index 325

NOTE — The word mosquito refers to the Anopheles in Part L, and to Aedes calopus in Part II., unless otherwise stated.

ILLUSTRATIONS

Jungle Covering a Stream .

Map of the Canal Zone Meteorological Tables i to 9 .

Rainfall: Curves for 1909, 1912, 1913 A Topographic Change : Near Empire Constantly Changing Topography: Near

MlRAFLORES ...... 38

PAGE

Chart Showing Malaria Death-Rate at

Ant-Guards: Old Hospital at Ancon . . 18 */

A Ditch at Ancon: Weeds Retarding

Water Flow 20^

37'

Daily Change of Topography ... 40

Blocked Water-Course Changed into an

Anopheles Breeding Place . . 42 '

Aquatic Vegetation Sheltering Larvae . 48 '

Swamp near Balboa, Caused by Building of

Dikes 52 1/

xi xii Illustrations

PAGE

The Rising Waters of Gatun Lake . 54 ^

Cattle on Low Pasture Lands : Panama . 56 «/

The Effect of Floods : Empire . . 58 •/

Alce United with Oil in Mat-like Masses :

Empire 58^

Railroad Tie Left in a Tree by a Subsiding

Flood 62 *

Oiling of Breeding Places along a River- Bank

Vegetation Protecting Mosquito Larvae .

A Seepage Outcrop, Controlled by an Intercepting Tile Ditch: Ancon

Vegetation Removed from the Edge of a Pond at Bohio .....

Result of Blocking the Rio Cardenas

Propagation Area of Gatun Mosquito Influx where Mosquito Flight was Discovered

Detail of Anopheles Breeding Ground where Flight Observations were Made

Grass and Plants almost Covering the Water Surface and Protecting Mosquito Larvae .......

Diagrams Showing best Locations for Screened Doors

•

•

Illustrations xiii

PAGE

A nopheles Collected in the Ground Cracks under the houses

The Relative Positions of Panama, Ancon, corozal, and mlraflores

Mosquito Trap Attached to a Window Screen .......

Mosquito Trap (Seen from Inside the House) .......

Experiment Station : Corozal

The Shore of Gatun Lake

Map of Gatun: Showing Anopheles Propagation Area and Houses where Stained Specimens were Recaptured .

Floating Islands Blown toward Gatun Lake ....

Masses of Aquatic Plants and Floating

Islands in Gatun Lake . . . . 102 V

The Anopheles Breeding Ground near

A Device for Determining the Flight

Direction of A nopheles . . . 108 !

Table Showing Number of Anopheles

Caught in Houses at Gatun . . .110

Staining A nopheles with Aniline Dye to

Determine Length of Flight . . 112^

96^

96^

98^ ioo^ x

101 •*

102 \/

XIV

Illustrations

Anopheles in a Mosquito-Bar Exposed to Air Currents at Night ....

Cracks in a Hydraulic Fill

Longitudinal Section and Cross-Section of an Intercepting Tile Drain .

Detail of Outlet of a Tile Drain

Plan and Side View of a Junction of Tile Lines .......

Concrete Lining of a Ditch of Small Cross- Section

Reinforced Thin Concrete Lining of a

Roadside Ditch, and Support of the

Sliding Toe of a Hill with Condemned

Cross-Ties ......

Plan and Cross-Section of a Key- Wall and Position of Weep-Holes

Concrete Ditch Lining .

Concrete Lined Ditch at Balboa

Key-Walls to Prevent Water Leaving Lined Ditches .....

Branch Ditches ......

Junction of Concrete Ditches, Showing Splash-Wall ......

Concrete Lining for the Bottom of a Small

PAGE

II4V

120 1

131/

135 ,

136 \/

138 1/

140 141

Illustrations xv

PAGE

Junction of a Branch Ditch with a Lined

Ditch 143 ^

Burning Grass from the Side of a Ditch;

Crude Oil Used as Fuel . . . 144

Condition of the Ditch Two Months after

Ditch Cleared by Hand Labor, Showing Condition Two Months after Removing Grass 148

A Gate to Impound Water for Flushing a

Ditch: Empire ..... 150'

Removal and Destruction of Larvae and Matted Alg.e in a Ditch by Flushing: Empire ....... 150K

A Simple Form of Oil Drip . . . 158 ^

The Flat Lampwick Drip for Heavy Oils . 160 «/

Oil Drip Applied to a Hillside Stream . 162

Oiling Obstructed Streams on Cut-Over

Lands 164 1/

Brush in Valley of Pedro Miguel River . 164 /

Application of Larvacide or Oil by Knapsack Sprayer: Miraflores . . 166 ^

Spray Nozzles 167 v

Field Supply Tank 168 ^

Oil-Cart for Applying Oil to Roadside

Ditches 168/

XVI

Illustrations

Pack-Mules, for Oil Transportation in Jungle Trails

The Larvacide Plant at Ancon .

Removing Vegetation from Overgrown Streams ......

Screened Verandas : Ancon

A Good Device to Prevent the Sagging of Screened Doors .

Types of Screened Houses : Colon Hospital Grounds ......

Types of Screened Houses: Culebra

Screened Cars in Railroad Construction Camps .......

Table of Malaria Incidence at Construction Camps ......

Slapper, Chloroform Tube, Acetylene Lamp, and Pill-Box; Used in Catching Anopheles in Houses ....

Mosquito Trap, with Details of Construction ......

Interior of Laborers' Barracks; where a nopheles were caught daily

Chart Showing Percentage of Employees Sick with Malaria in the Wet Seasons

PAGE l/

206 209

214/

Illustrations xvii

PAGE

Diagram Showing the Yearly Reduction

of Malaria among Canal Employees . 226 ^

Chart Showing the Monthly Malaria

Map of Havana; Showing the Yellow

Fever District ..... 236X

Chart Showing the Prevalence of Yellow

Fever in Havana, Cuba .... 244 f

Chart Showing Yellow Fever Cases on the

Part of the Panama Fumigation Brigade . 284^"

Screened Vestibule Door .... 286 S

A Poorly Constructed Eave-Trough . . 288 V

A Clogged Eave-Trough .... 288

Diagram of a Firmly Supported Eave- Trough 289 /*

A Firmly Supported Eave-Trough with a Good Slope ...... 290

Mosquito-Proof Water Barrel .

A Short Length of Eave-Trough Used over a Doorway ......

S

PART I

Anti-Malaria Campaign

Chapter I

THE STATUS OF KNOWLEDGE OF ANTI-MALARIA WORK IN I904 AND THE CAMPAIGN AT HAVANA

r ~PHE anti-malaria work of importance accom- * plished previous to 1904 was that done by Colonel Gorgas in Cuba and Sir Ronald Ross in the British Colonies in the East.

The necessity for mosquito control has been appreciated since it was first demonstrated that some mosquitoes may transmit disease. Since 1900 great progress has been made in the study of the life history and habits of mosquitoes. As a result, we find remarkable differences in habits, even among species of the same genus. The determination of such facts is of great importance in the economic control or eradication of the disease-conveying species, and also in that of other genera that affect personal comfort or real estate values.

It is realized that conditions pertaining to Anopheles control on the Isthmus and the habits of the species encountered may differ from those which will be found elsewhere, and that methods of procedure for malaria control must be modified accordingly ; but if in a large territory like Panama, where conditions are most favorable for the multiplication of mosquitoes every day in the year, malaria has been controlled at a reasonable cost, the methods which accomplished the change are worth consideration.

Health officials from foreign countries have visited the Isthmus to obtain practical information in order to apply this later in malaria and yellow fever eradication abroad.

Much interest was shown by the thousands of Americans who visited the canal, and many of them asked why the same class of work could not be attempted in malarial districts in the United States, and also sought information about the work accomplished and methods of procedure.

The canal will be used by the commerce of all nations, and the progress made in sanitation in Cuba and Panama will have far-reaching effects.

The character of the work at Havana was quite different from that required on the Isthmus. The general situation resembled more closely the conditions and drainage problems occurring in the southern part of the United States, and subtropical

The Campaign at Havana 5

countries not having an excessive annual rainfall. This work was started in 1901 when the yellow fever campaign was well advanced. No anti-malaria work had been attempted elsewhere previous to the Cuban anti-malaria campaign. Ross started his practical field work in the East at the same time that work was begun in Havana. There was no previously acquired information available on the subject nor any known practical methods that could be followed, or that could assist those in charge of operations. At that time, very little was known regarding the habits and life history of Anopheles. It was practically all pioneer work, and improvements and methods of procedure were devised as the work progressed. Years of subsequent experience have shown that for pioneer work the scheme was excellent.

A survey was first made to determine the principal sources of Anopheles affecting Havana and its outlying suburbs. The most important propagation areas received first attention. Treatment of pools with oil having a paraffin base was tested. As the wet places harboring Anopheles were widely scattered over a large area, a covered wagon was used for transporting laborers, tools, and oil to control as much territory as possible with the small force employed. The plan of oiling was arranged so that areas were not treated at regular intervals, but when Anopheles and other mosquito larvae were present.

The system of inspection was well carried out, and inspections were independently checked at proper intervals. The result of Anopheles eradication by use of oil was fairly good, and better results were obtained than expected under the climatic and topographical conditions on the Isthmus. Very few topographical changes were being made in the vicinity of Havana. The class of labor available was very good, and fairly intelligent. The wages paid to the men in the Anopheles brigade were a little above average laborer's wages; this enabled the sanitary department to obtain the best class of labor and to retain it. The men used their heads as well as their hands, and worked with interest. The unit cost of ditching and of oil application was very low, and much was saved by the proper selection and payment of labor. Poor labor on anti-malaria work is most unsatisfactory, and no saving has ever been made by its employment.

It was soon found that there were disadvantages in using oil, as well as much repetition of work that could be eliminated. As rapidly as the limited appropriation would allow, the pools costing most

The Campaign at Havana 7

to control were drained or filled in, and the area under control thus increased. Each place drained or filled became one less to inspect and treat.

As time went on, the anti-Anopheles work consisted chiefly of draining and filling depressions in fields where water collected. The use of what is known as the "herring bone" system of ditching, the training of streams to more direct courses, and the reducing of the average wetted section of ditches, rapidly decreased the necessity for regular application of oil and for frequent inspection.

The geological formation and topographical conditions were favorable. The watercourses and areas to be treated were often distant from one another, yet the streams were of fair grade, and most of the areas needing treatment were located so that they could be drained. In some cases the impervious surface clay rested upon a coral formation. The latter was of a porous nature, and absorbed a large quantity of water in a relatively short time. In some places where there were ponds, and surface drainage was out of the question, they were connected by one or more ditches, and led to shallow wells in the coral formation, where the water was absorbed. When one well was not sufficient, two or more were mad 2 and connected, to increase the absorbent surface.

It was found that the bottom of these wells became clogged with clay and silt, but that the sides supplied sufficient absorbent surface to give satisfactory results. Fish were used to keep some of the wells free from mosquito life ; in others, that frequently became dry, oil was used. Sometimes it was necessary to scrape well walls several times during the wet season to increase absorption.

The limited funds available did not permit the permanent lining of ditches, although in many cases it would have been more economical than treating and maintaining them for an indefinite length of time.

Anopheles production in wet areas caused by seepage occurs in Cuba, and one case near Havana was especially interesting. In 1900, a few houses were located near the top of the hill known as Jesus del Monte. Malaria prevailed among the tenants, and several deaths from pernicious malaria occurred there immediately before the undertaking of anti-malaria work. The hill appeared to be dry, and was well above the elevation of the surrounding ground. Many inspections were made to locate the source of Anopheles with negative results. It was supposed that they came from a distance, but an extended inspection of the surrounding country disproved this conclusion.

The Campaign at Havana 9

Finally, it was decided that the breeding place must be local, and the labor force was put in line, men eight feet apart so that every square yard of the hill would be seen, and no wet place, however small, could be missed. They marched along for some time before a piece of partially soft ground was found. There were no surface indications, such as a change in the vegetation or its color, to mark the outline of the wet area. A thin film of water was found to outcrop along a contour line, to run along the surface for a distance of about twenty feet, and then disappear into the ground. The mosquito larvae were very plentiful. A ditch was made above the seepage outcrop line, but failed to intercept the water. Two short and deep parallel intercepting ditches were made about nine feet apart, but failed to prevent the water coming up between the two ditches. It became evident that the local porous water-bearing strata were inclined and pointed upwards, and that a distant pressure was forcing the water uphill. Ditching was out of the question. At a small cost the ground affected by the surface flow was covered with gravel and cinders to a depth of about six inches, so that the mosquitoes could not reach the water which continued in its original path.

Since that time the importance of hidden mosio The Control of Mosquitoes

quito-producing areas, and their relation to the malaria situation, has been fully appreciated by those engaged in anti-malaria work. Beginners usually learn facts by temporary failure. Soon after the completion of this work the adult Anopheles disappeared from the vicinity. No new cases of malaria occurred. The houses that had been so long vacant because of the prevalence of malaria were again occupied. When it became known that malaria no longer existed in that locality, it was plotted into lots, and has become one of the popular residential sections of the town. Real estate values have advanced accordingly.

On low flat lands where cattle were pastured, it was found difficult to prevent Anopheles propagation in the water retained by hoof -prints. It became essential to prevent certain portions of fields from being used for grazing purposes during the wet season.

It was also found that plants along the shore line, as well as aquatic plants, reduced the surface velocity of water in streams and rivers to such an extent as to afford protection and harboring places for mosquito larvae. The vegetation at the edges of ponds and streams was kept cut short. Aquatic vegetation was pulled up by the roots and removed. Small fish were very efficient larvae

The Campaign at Havana n

exterminators after the clearing and training of natural watercourses was accomplished. Conditions affecting growth of vegetation and algae were less favorable in Cuba, and, in consequence, fish are of more use there as destroyers of mosquito larvae than on the Isthmus.

Beds of watercress in the Chinese truck gardens were a prolific source of Anopheles in Havana. The cress beds were made by erecting small dikes on flat land, and bringing water to them by ditches from nearby streams. When the enclosure was filled, the water was left standing for long periods. In order to control the situation, small wooden sliding gates were installed at each end of the watercress beds, which were flooded at frequent intervals for short periods, and the water then allowed to escape back to the stream. This scheme, when properly carried out, practically stopped Anopheles development. The gardeners who refused to adopt the new method were not allowed to grow watercress. The crops grown in this manner were as vigorous as those raised in the continuously flooded patches.

Between the heavy showers that occur near Havana there are dry periods, accompanied by strong winds. When the ditches and watercourses are kept fairly free from vegetation, the heavy i2 The Control of Mosquitoes

showers are often beneficial, as they remove any Anopheles larvae clinging to banks of ditches or cleared streams. The trade winds assist evaporation to a considerable extent, and help to dry the depressions in flat areas that hold water. The soil is of such a character that the trained streams and ditches can be kept to a proper section with less work than is necessary to attain this result at Panama. Washouts and caving of ditch banks did not happen as frequently.

In many places apparently well fitted for the support of Anopheles larvae, they were absent; yet lived and developed when placed therein as an experiment. The reason why Anopheles eggs are not laid in certain areas apparently in every way similar to those in which larvae are found is yet unexplained. The season of Anopheles production in Cuba is much shorter and less continuous than on the Isthmus. It was largely due to these causes that oiling at irregular intervals gave satisfactory results. Conditions of soil, topography, and climate there do not favor the rapid and continuous production of mosquitoes as much as in the Canal Zone.

The drainage connected with the Havana campaign was completed within a year of the time anti-malaria work began, and its maintenance

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| Deaths caused by Malaria in Havana 1871-1914 •

Anti Malaria Campaign was Started in 1901 -Note the Curve from 1901 to 1914

In 44 years )

Chart showing malaria death-rate at Havana 1871 to 1914.

since then has been mostly a question of economy. The sanitary department of the Republic of Cuba has continued the work started by Colonel Gorgas and deserves great praise for the excellent record it has maintained.

To review the results of the Havana campaign, the records show :

Population of Havana, 350,000.

From 1890 to 1900, — 5643 deaths from malaria.

From 1900 to 1910, — 444 deaths from malaria, with a largely increased population.

It is interesting to note the rapidity with which malaria control was accomplished, as shown by the following table:

TABLE OF DEATHS FROM MALARIA IN HAVANA, CUBA,

Year

No. of Deaths

Year

No. of Deaths

Year

No. of Deaths

1901 1902 1903 1904

1905 1906 1907 1908

32 26

1909 1910 1911 1912

15 12

Malarial fever is almost eliminated from Havana and its suburbs.

The cost of maintaining this condition is very

The Campaign at Havana 15

low, and might be further reduced by lining the bottoms of the small streams and ditches with reinforced concrete, in order to lower the cost of cleaning and ditch maintenance.

Chapter II The Situation On The Isthmus In I904, Before American Occupation

PRESIDENT ROOSEVELT appointed Colonel * W. C. Gorgas as Chief Sanitary Officer of the Isthmian Canal Commission, and it was under his leadership that the first sanitary survey was made. He established temporary headquarters for his first assistants at Ancon, where the French had terraced the hillsides and had established a hospital of about twenty wards. The situation selected by the French was excellent, but to-day, from our more advanced knowledge, we can readily understand why their sick-rate was so high, and can also realize that it would have been equally so under an American administration working with the limited knowledge pertaining to malaria previous to the year 1900.

At the time the American government assumed control of the Canal Zone, there was a succession

of villages strung along the line of the canal ; most of them close to the camps occupied by the laborers during the days of the French Canal Company. They were located apparently with reference to proximity to work and many were near a convenient source of water supply. At the time these camps were established, nothing was known regarding the transmission of malaria. Better locations were available, but they were in nearly all cases far distant from the canal. Some of the camps had been abandoned altogether and could not be reached without cutting pathways through the jungle.

In some cases, where the rafters had decayed and the roofs had collapsed, trees with a diameter of ten inches were growing inside the buildings. The natural watercourses were overgrown by dense jungle, and nearly all of the villages were practically in the jungle itself. The French engineers had, for drainage purposes, placed masonry lined ditches near some settlements, and the work was excellent; it is in as good condition to-day as at the date of completion, and will probably remain so for many years to come.

In June, 1904, about 11 00 laborers were employed in canal work at Culebra; they lived in the adjacent villages, and very few isolated houses existed in the bush. Many of the old French buildings were occupied by laborers who had remained after the financial failure of the French company.

Malarial fever was prevalent among these people, and they had neither the knowledge nor the means to combat it. At Paraiso, in September, 1904, there was a population of 350 of which 42 were sick in bed. At Bohio, a village fifteen miles south of Colon, blood samples were taken from natives, and eighty per cent, showed malaria infection. But even this poor and ignorant class of people took steps to do the best they knew how; they prayed for deliverance from fever and shunned certain localities in which the sick-rate was abnormally high as compared with the prevailing high fever rate.

At Corozal, the nearest village to Panama, only one house was occupied, and many colored people told us that "to live there is to be sick and die."

The situation at Ancon Hospital was extremely interesting. The grounds were magnificent ; there were palms, beautiful crotons, and other decorative plants near the wards and on the terrace, but the insects, and especially the ants, destroyed them repeatedly. The gardeners partially overcame this difficulty by placing hollow earthenware t *

Ant-guards : Old hospital at Ancon rings of a semi-spherical section around each plant. They were kept filled with water and of course contained many larvae of both Aedes calopus and Anopheles as well as algae, vegetable debris, etc.

The ditches near the wards were lined with field stone; the spaces between the stones were rilled with earth and grass which retarded the current of water. These ditches discharged onto the grasscovered, clayey soils, and pools remained there, distributed over a large area.

The natural topography of the hill gave a fairly steep slope with a more gently sloping bench below it. The highest part of the hill is about six hundred feet above sea level. The water absorbed by the upper part of the hill came to the surface at a lower level on a clay-like formation covered with grass, making the hillside resemble a bog in many places. The outcrop of water, which oozed slowly from the ground, often followed the contour of the hill for a considerable distance. Consequently the area immediately below that contour was wet almost continually.

There was a cow pasture on the top of the hill, and throughout the rainy season the hoof -prints remained wet or full of water. Ditches of varying widths ran down the slope, and the water spread over the ground and sometimes did not return to the lower part of the ditch. In addition, the foot of the hill formed the shore line of an extensive swamp. These adverse conditions, and wet areas covered with vegetation, encouraged Anopheles. A more prolific source would be hard to imagine.

The number of adult Anopheles present in the hospital wards and buildings corresponded with the numerous favorable propagation areas on and near the hillside. At night, comfort was impossible and mosquito bars indispensable. Not a single building was screened. The malaria and yellow fever patients had been accessible to Anopheles and Aedes calopus, and the other patients were near them. The patients in wards were located according to nationality instead of according to the nature of their illness. Had it been intended to spread yellow fever and malaria with the greatest rapidity among the patients as soon as they arrived, no better plan could have been adopted. Similar conditions have existed in other tropical countries; in fact, were customary in past years.