VECTOR CONTROL PLANNING IN CALIFORNIA Perhaps the best

VECTOR CONTROL PLANNING
IN CALIFORNIA
By FRANK M. STEAD
Chief, Divisian oj Environmental Sanitation, Department of Public Health,
State of California
Perhaps the best way to introduce a discussion of vector control
problems in California is to review the vector diseasesin the order of
their appearance like actors onto the stage of public notice.
Fly-Borne Diseases are not always thought of as vector diseases,but
they were probably the first for which the vector role of an insect was
understood. Intestinal diseases are transmitted in severa1 ways, it is
tme, but with improvements in the protection and purification of public
water supplies, the relative importance of ílies in the transmission of
Typhoid Fever, Bacillary and Amoebic Dysentery is increasing. Flies
are so ubiquitous that they doubtless served as vectors in the spread of
these diseasesin California before the appearance of the white man and
thus belong first on our list.
Malaria is next on the scene. During the gold rush days, starting in
1849, when miners lived in the open on the banks of the streams in the
mild cliiate of the central valley of California, this diseasetook heavy
toll. Mining soon gave way to agricultura1 development, but careless
use of the plentiful irrigation water and the culture of such crops as rice
kept malaria at a high leve1 for over seventy year. Not until after
1920, largely as a result of large scale mosquito control efforts, did the
incidence of this disease drop below 500 reported casesper year.
At the turn of the century, an outbreak of Bubonic Plague in San
Francisco’s Chinatown, as a result of the State’s stubborn refusal to
acknowledge it, reached such proportions that it was necessary for the
Federal Govermnent to threaten to quarantine the entire state. Another outbreak in 1925 in Los Angeles again focused public attention
on this diseaseand continued casesin al1parts of the state in the ensuing
years have testified to the fact that this disease is well established.
Records of the State Department of Public Health indicate that
Rocky Mountain Spotted Fever was first recognized in California in 1903.
In 1916, however, an investigation was made and a report published that
first brought this disease to public notice. Since that time 156 cases
with 21 deaths have been recorded in six counties in the mountainous
portion of northern California.
In 1916 a small outbreak of Typhus Fever occurred in southern California among Mexican railroad track workers. It should be of interest
to the group here assembled, to note that these men were brought into
California by the railroad companies from Laredo, Texas. About 30
cases occurred in California during this outbreak and were thought to
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be of the epidemic or louseborne type. There were 4 deaths. Starting
in 1919, casesof murine or flea-borne typhus began to appear in southern
California, and increased in the early twenties, died down during the
next decade only to upsurge again in the late thirties in a trend that
still is climbing with a peak of 62 casesin 1945 and a similar number since
~ that year.
In 1910, a new disease was studied in California and the causative
agent identified by the United States Public Health Service. Named
, after Tulare County, it was called Tdaremia.
This disease has the
doubtful distinction of having more animal reservoirs and more modes
of transmission than any other vector disease. The number of human
cases
is not spectacular and the present prospects are not alarming,
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but an increase in contact between humans and wild reservoir animals,
such as rabbits, could result in a rapid increase. The disease is by no
means confied to its namesake county, but is widely spread throughout
the state.
Relapting Fever was recognized in California as early as 1921, but
, began to attract public notice about 1930, when numerous casesbegan
to occur in widely separated mountain resort areas usually at altitudes
of*5,000feet or more. Al1 caseswere tick-borne and none fatal. During
the past 5 years, the diseasehas increased in occurrence and in the Lake
Tahoe area, it has caused suflicient alarm to keep many people away
during the vacation season. Most of the casesare contracted in cabins
or buildings, especially after opening them in spring and early summer.
Epidemic Encephalitis has been a reportable disease in California
since 1919 and during the period, 1920 to 1936, from 150 to 75 cases
per year were reported in a generally declining trend. In 1937, a Sharp
increase occurred and the new caseswere different from the old in severa1
respects. Instead of occurring uniformly throughout the year and
throughout the state, they occurred principally during summer and fa11
and were all located in rural areas in the Central Valley. A great
increase in case fatality was noted. It has now been definitely established that cases of the new type are mosquito-borne and the most
likely vector is the mosquito, C’ulez tarsalis which abounds in the Central
Valley of California. Over 100 cases of this disease now occur each
year in this area.
The last of the actors in this drama to appear on the California stage
- is & Fever which broke out last year in Los Angeles County with over
one hundred casesand the ink is not yet dry on the reports of initial
field investigation of its possible modes of transmission.
The mode of attack which the California State Department of Public
Health has made on these vector diseasesin the past is as varied as the
diseasesthemselves. Fly-borne diseaseshave been approached by the
’ route of sanitation, it being rightly assumed that elimination of the
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major sources of fly breedmg by proper methods of excreta, manure and
garbage disposal would be the most effective approach to the problem.
Malaria was early brought under control by the securing of legislation
which made possible the establishment of mosquito abatement districts.
There are 38 such districts in California today with a total area under
control of 16,000 square miles. These districts, although initially
established for public health reasons, have so proved their Worth from
the economic and comfort standpoint, that they would endure and
grow even without the stimulus of the threat or existence of mosquito
borne disease. Thus when encephalitis was shown to be mosquitoborne, the health department had its tools ready made and at hand to
cope with it. An annual appropriation by the legislature of $400,000
is disbursed by t,he State Department of Public Health to mosquito
abatement districts in return for well planned, technically directed,
fmancially matched programs, directed at the vectors of malaria and
encephalitis.
Since 1927, when the outbreak of Plague in Los Angeles indicated
that this disease was widespread in California, the Department has
carried on one of the most extensive, continuing, endemic surveys on
record. Eight field crews, each composed of three men, have hunted,
trapped and poisoned rats and ground squirrels in al1 parts of the state.
Rodents have been dissected and examined for gross pathology and
combed for ectoparasites and hundreds of thousands of specimens of
tissue and thousands of pools of ectoparas%eshave been examined in the
laboratory with the result that plague endemic foci have been located
in hundreds of places in the state. The survey work, in itself, has accomplished a certain degree of control, and intensive spot control work
by the Department of Agriculture has been done around areas of positive
plague demonstration, but inherently, the program has been one of
survey rather than control.
No field work, either to discover the foci, or to control the reservoirs
or vectors of Rocly Mountain Spotted Fever, has yet been done.
An intensive endemic survey for Typhus Fever, however, over a
three year period has been conducted in 16 counties of California, involving the examining of 1,731 animals and 157 pools of ectoparasites.
This survey has served to define endemic areas in five counties of southern California.
During the past frfteen years, endemic studies for Tularemia have
been coupled to those for plague, with the result that the extent of
establishment of this disease is reliably known.
Relapsing Fever endemic areas have been incompletely defined by
the occurrence of human cases, until this last fa11when a tick survey
was conducted over a considerable portion of the mountainous area
above 5,000 feet elevation in the state.
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This constituted the picture with respect to vector control activities
in the California State Department of Public Health, when on July 1,
1947, the Bureau of Vector Control was established. Prior to this time,
activities related to vector control had been spread through many
separate bureaus, and coordinated long-range planning in the whole
vector field had not been possible. The new bureau had, it is true, a
rich heritage, but was given a man-sized job to do. The nucleus of the
bureau was formed by pooling the men in the Department who had
worked on rodent surveys with those who had engaged in mosquito
control studies and relations with mosquito control districts. The field
staff now totals 44 men.
The first task was to take stock of what was known and what had been
done in the past on each of the vector diseases. Certain conclusions
were inescapable. The past program looked at as a whole, was lopsided
and incomplete. Literally millions of dollars had been spent on endemic
surveys of plague, but virtually no studies to adapt techniques of rodent
control to California cities had been carried out, and with a few exceptions, no continuing, realistic rodent control programs were in existence
in cities. A great deal of time and study on the other hand, had been
given to the perfection and demonstration of techniques of large scale
mosquito control adaptable to California conditions. Efforts to control
encephalitis were crippled by incomplete knowledge of reservoirs and
vectors of that disease, and with respect to Q fever we had absolutely
no facts to guide a control program. No one knew what the potential
threat of Rocky Mountain spotted fever was nor the extent to which
relapsing fever had become established. Neither did we know whether
chipmunks or bats, for instarme, were important reservoirs of relapsing
fever, or whether the diseasecould be effectively attacked by use of DDT
against the tick vector.
The sudden appearance of Q fever without warning, also pointed up
the necessity of being always in a position to meet a new and unexpected
situation. In a Word, it was clear that our program must be balanced
and highly flexible.
To achieve this objective, we established a continuing analysis chart
setting forth for each vector disease in relative manner, the current
importance as indicated by incidence of disease, and prevalence of
reservoir and vector.
Deficiencies in fundamental knowledge for some diseases, indicated
that the first step needed was research. Successive steps in arder are:
endemic surveys, special studies and demonstrations of control techniques, and lastly, stimulation of actual control programs. Recognizmg that we were working in a tremendously broad field with a limited,
though sizable staff, we next set ourselves the objective of adjusting
our program so that the amount of time and effort put on each disease
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is always kept roughly proportional to the current importance which
that diseasehas to the people of the state. This meant serious slashing
of some activities of many years standing, and the bold embarking on
brand new programs. Our planning is therefore largely on a year-byyear basis and in the different diseases, we are in various stages of
program development. We are confident, however, that by this approach to our problem, we will escape being caught in the trap of a
rigid, crystallized program, and instead, be able to continuously mold
our program to serve our needs.
For the current calendar year, major emphasis of our vector control
program will be four-fold: first, the carrying out of rodent control
demonstrations and the stimulation of rodent control programs in
cities, largely guided by local departments of health; second continuing
demonstrations and program development for the control of the vectors
of encephalitis and malaria in the Central Valley of California; third,
fundamental investigation to determine the identity and prevalence of
vectors of Q fever; and fourth, studies and demonstrations specifically
directed toward the control of the insect vectors of relapsing fever,
fly-borne diseases,plague and typhus fever.
PROYECTO
PARA EL CONTROL DE VECTORES
CALIFORNIA
[Sumario)
EN
En su trabajo, leído en mesa redonda, hace el A. una breve historia de las
enfermedades transmitidas por vectores: malaria, fiebre maculosa de las Montañas Rocosas, tifo, fiebre recurrente, encefalitis y fiebre Q, informando sobre las
campañas realizadas por el Departamento de Salubridad del Estado de California
para combatir dichos vectores. Existen actualmente en California 38 distritos
de lucha contra el mosquito, con una extensión 16,000 millas cuadradas, y al
descubrirse que la encefalitis es transmitida por el mosquito, el Depto. de Sanidad
asignó la suma de $400,000 anuales para combatir tanto al vector de dicha enfermedad como al del paludismo de la malaria mediante programas bien coordinados. En 1927, al estudiarse un brote de peste en los Angeles, se demostró que
Bsta se hallaba extendida en California, lo que condujo a estudios extensos y
continuados sobre su endemicidad. En cuanto a la fiebre maculosa de las Montafias Rocosas, nada se ha hecho para descubrir los focos o controlar los reservorios
o vectores: en 16 Condados de California se han realizado estudios endémicos
sobre tifo por un período de tres años, habiéndose examinado 1,731 animales y
157 mezclas de ectoparásitos, definikndose las zonas endémicas en cinco Condados
de California del Sur; durante los 15 años pasados se fundieron los estudios de
tularemia y peste, existiendo en la actualidad un conocimiento bastante exacto
de esta Gltima; las zonas enddmicas de fiebre recurrente han sido poco definidas
por la ocurrencia de casos humanos hasta el otoño pasado en que se efectuó un
estudio de garrapatas en una gran porción de la extensión montañosa a una elevaci6n de 5,000 pies. Tal era la situación del Depto. de Sanidad Publica del
Estado de California, respecto a vectores, hasta el 1” de julio de 1947 en que se
estableció la Oficina de Control de Vectores, la que inició sus labores con un
caudal de conocimientos, pero tambi6n haci6ndose cargo de una enorme labor.
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Los esfuerzos para controlar la encefalitis se vieron entorpecidos por la falta de
conocimiento de los reservorios y vectores de la enfermedad, y con respecto a la
fiebre Q no existía absolutamente nada que sirviera de base para un programa de
control; nadie conocfa la amenaza potencial que representa la fiebre maculosa de
las Montañas Rocosas, ni cuánto se había extendido la fiebre recurrente. El
brote repentino de fiebre Q demostró la necesidad de hallarse siempre preparado
para hacer frente a situaciones inesperadas; en una palabra, resultó cIaro que el
programa debía ser equilibrado y sumamente jlexible, esperando que la actitud
sobre el programa no eaiga en el defecto de la rigidez, sino que se adapte continuamente a las necesidades. Este año, nuestro empeño es cuádruple: (l), demostraciones de control de roedores y estímulo de los programas en las ciudades
asesorado8 por los departamentos focales de salubridad; (Z), continuación de las
demostraciones y programas de control de los vectores de la encefalitis y la
malaria en el Valle Central de California; 39, investigación fundamental para
determinar la identidad y prevalencia de los vectores de fiebre Q; y 4”, estudios y
demostraciones dirigidas específicamente hacia el control de insectos vectores
de fiebre recurrente, enfermedades diseminadas por moscas, peste y tifo.