1 REPORT RESUMES

ED 012205 RC 001 108 MAN, MOSQUITOES AND MICROBES. BY- SCHC.:INOVER, ROBERTA. FLORIDA ST. BOARD OFHEALTH, JACKSONVILLE PVC DATE MAY 67 EMS PRICEMF-$0.09 HC-V.20 30P.

DESCRIPTORS- *DISEASES, *DISEASECONTROL, *ECONOMICS, *HEALTH, *RESEARCH, ENTOMOLOGICALRESEARCH CENTER, BUREAU OF PREVENTABLE DISEASES, BUREAUOF ENTOMOLOGY, BUREAU OF LACORATO:ZIES, JACKSONVILLE,MIDGE CONTROL LABORATORY

THE CONTROL OF MOSQUITOESIS A MATTER OF INCREASING CONCERN IN THE STATE 07 FLORIDA.A BRIEF DESCRIPTION OF THE LIFE CYCLE, VARIOUS SPECIES,CONTROL, AND DESCRIPTION OF DISEASES TRANSMITTED BY THEMOSQUITO WAS PRESENTED. THE ARTICLE CONCLUDED THAT MOSQUITOCONTROL IS NOT ONLY A HEALTH PROBLEM, BUT ALSO A MATTEROF IMPROVED ECONOMICS INRELATION TO POPULATION GROWTH. THISDOCUMENT IS AN ISSUE OF "FLORIDA HEALTH NOTES," VOLUME 59,NUMBER 5, MAY 1967. (JS) FLORIDA HEALTH NOTES

U.S. DEPARTMENT Of HEALTH, EDUCATION& WELFARE OFFICE OF EDUCATION

THIS DOCUMENT HAS BEEN REPRODUCEDEXACTLY AS RECEIVED FROM THE

PERSON OR ORGANIZATION ORIGINATINGIT.POINTS OF VIEW OR OPINIONS

STATED DO NOT NECESSARILY REPRESENTOFFICIAL OFFICE Of EDUCATION POSITION OR POLICY.

VOLUME 59- NO. 5 lin, Mospitses aid Microbes MAY 1967

co/ /eg (Cover photo) A salt marsh mos- quito, SOLLIC;TANS, takes a meet of blood from a human finger. If the has a virus, it would pass it on to the human through a salivary fluid which the mosquito in- jectsinto the human during the meal.

Arthropod-borne diseases are norm- ally carried by mosquitoes from one bird to another or to a rodent. These serve as reservoirs for the diseases. When horses or men are bitten by a virus-carryingmosquito,theybe- come ill and sometimes die. II lall, Mosquitoes andMicrobes

It's summertime in Florida!

At one time summer meant "mosquito-',:me" andlife was con- sidered unbearable; pestilences raged; a member of Congress said that the state couldnever be developed, was not a fit place to live, and described it as a land ofswamps, alligators, frogs and mos- quitoes. Today, onlya few decades later, mosquito control has made Florida a year-around tourist's paradise,a retirement place and a desirable spot for enjoyable living.

Ever since the Spaniards, and recorded history, touchedthese shores, man and the mosquito have been bitter enemies.This in- sect has been known as a biting pest for centuries,but only since the beginning of the 20th Century hasman known that , malaria, dengue fever andsome viral encephalitides were -borne diseases.

Mosqui :oes have always been consideredone of the unpleasant things in life. The knowledge of how to eradicatethese pests and the diseases they carry is being acquired throughresearch carried on by the State Board of Health, the U. S. Public Health Service, the U. S. Department of Agriculture, mosquitocontrol districts, private philanthropic foundations and other governmentalagencies.

This issue of Florida Health Notes will tellyou about

the dangers engendered by the mosquito;

the fight to make the state pleasantly livable foryou, for the six million other residents of the state and for17 million annual visitors ; and

the research being conducted to find the intimatesecrets of a mosquito's life and to control arthropod-bornediseases.

FLORIDA HEALTH NOTES 231 Man-The Victim

From the earliest daysmosquitoes have beena nuisance in Flor- ida. They have playeda prominent part in the slow development of this subtropicalgem called Florida, even though thestate other- wise had much to offer itsresidents and visitors. Thebeauty of the Sunshine State has beenmarred by 67 species ofmosquitoes, several of them carrying diseaseand/or otl- erwise making lifein- tolerable.

The mosquitowas such a plague when the Spaniards arrivedthat they named what today isPonce de Leon Inlet,or Mosquito Inlet, "Barro de ." Sincethe time of the earliestmaps, one of which dates from 1615,some of Florida's inlets, lagoons andsec- tions have borne thename Mosquito. In the 18th Century,the part of Florida lying betweenthe St. Johns River and thecoastal lagoons north of Cape Canaveralwas called "The Mosquito Country,"or "The Mosquitoes."

Two lagoons in thearea were named North and South Mosquito Lagoons. When the British ownedFlorida, they tried to improve the nomenclature by namingthe north lagoon after theEarl of Halifax and the south lagoonafter the Earl of Hillsboro.Later in the 19th Century, thesenames became official but the Hillsboro River was changed about40 years ago to NorthIndian Lagoon to avoid confusion witha stream near Tampa.

FLORIDA HEALTH NOTES Published monthly by the FloridaState Board of Health, Wilson T. State Health OfficerPublication office, Box 210, Sowdcr, M D, M.P.H , postage paid at Jacksonville, Florida Jacksonville,Florida 32201Second class an interest in the state's health This publicat on isfor individuals and institutions with credit programsPermissionisgiven to quote any story providing is given to the Florida State Board ofHealth Ed.tor Division of Health Education. Robert ASchoonover, M A, VOLUME 59NO. 5 MAY 1967

232 FLORIDA HEALTHNOTES 4 S

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Hundreds of thousands of mosquito pupae clog a ditch.Unless they are destroyed, adult mosquitoes will emerge within a few hours and take flight at twilight.

In 1824 when Mosquito Country was made into a county which included a large portion of peninsular Florida, governmental offi- cials could think of no more appropriate name than "Mosquito Conty." The Florida Legizlature changed the disagreeable name to Orange County in 1845. The was feared by armies that fought across Florida. Soldiers were so beset by mosquitoes during skirmishes that the men were unable to fight.

For many years settlements were restricted to the northern sec- tion of the state. The southern portion was a series of swamps, lakes, rivers and hammocks populated mostly by hoards ofmos- quitoes and other biting . Even though northern Florida was settled, it suffered from disease, hardship and poverty. With the exception of Key West, the major citiesTallahassee, Jacksonville,

FLORIDA HEALTH NOTES 233 St. Augustine and Pensacolawere in this area, which was known as the "malaria belt." Every year deadly fevers spread consternation throughout the region. Shops were closed ; fear of the epidemic and the stifling heat caused those who could afford the expense to migrate North to more healthful climates for the months of August, September, October and November. Those who were forced to stay behind suffered through the pestilent seasons or were buried in the large cemeteries which marred the beauty of the region.

When the statehood of Florida was being debated in Congress, John Randolph of Virginia stated that Florida could never be de- veloped, nor would it ever be a fit place to live. He described the region as "a landof swamps, of quagmires, of frogs and alligators and mosquitoes."

( The Story of Yellow Fever For years yellow fever brought fear and panic to many Florida cities which were visited by ships from the Caribbean and Central and South America. Commerce and passengers arriving in Florida ports seemed to be accompanied by wave after wave of yellow fever. Many strange remedies were recommended. Mail and cargo were

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7 fumigated ; cannons were fired; lime was spread in thestreets, houses and shops; bonfires were lit at night.

The 1877yellow fever epidemicin Fernandina and was described by Jacksonville historiansas the state's greatestholocaust. Fernandina, witha population of 1632, had fever. Twenty-four 1146 persons ill withthe died. In 1887, yellowfever epidemics raged Key West, Tampa, in Plant City and Manatee.The panicwas so wide- spread in Tampathat lighted lampswere left and stoves burning when people were still fled the city inhaste. The 1888epidemic in Jacksonvillesaw some 10,000persons (out of a population 26,800 in Duval of County) flee the cityin carriages, drays,wagons, trains and shipsladen to capacity. The yellow fever epidemicsbrought about thecreation of the State Board ofHealth. Althoughnobody knew it at public health the time, the programs of Florida had theirbeginning in themos- quito. By 1901 thisinsect was discoveredto be the transmitter yellow fever. of Followingan epidemic in Pensacolain 1905, the quarantining of shipswhich were thoughtto be bringing the from foreign vector ports, the screeningand spraying ofhomes, the destruction of adultmosquitoes and theprevention of mosquito breeding broughtabout an end to thefearsome epidemics. The mosquito was also incriminated in thetransmission of dengue fever and malaria.Although obervations State Health were made by the first Officer, Dr. JosephY. Porter, thatattacks of malaria were more deadly along the river bottoms,marshlands and in the flatwoods,no concerted efforts were made to control malariauntil World War Iwhen drainage andlarviciding were carried Camp Johnson by out at the joint efforts ofthe U. S. Army, theU. S. Public Health Serviceand the State Boardof Health.

Mosquito Control'sBeginning . The first malaria control programwas undertaken by the State Board of Healthin Perry in 1920.At the time it project of its kind in was the largest the country. A totalof $28,000was spent and 47,000 cubic yardsof dirt moved tomake drainage ditches canals. The cost of and the projectwas borne by the City ofPerry,

FLORIDA HEALTHNOTES 235 Taylor County and the Burton Swartz Cypress Company withthe State Board of Health supplying technical supervision. The result- ing better health of the people of Lhearea proved the benefits of the project.

Further progress in controlling malaria, and subsequentlymos- quitoes, was made when the Rockefeller Foundation establisheda malaria control research station at Tallahassee in 1931. This sta- tion. working in conjuneon with the State Hospital at Chatta- hoochee and the State E. _.rd of Health, gave inestimable value to work in the malaria field. A mosquito control research stationwas also established in Orlando in 1932 by the U. S. Department of Agriculture and later moved to Gainesville.

The State Board of Health created the Bureau of Malaria Control in 1941 to study and make recommendations for controlling malaria in the state. This became the Bureau of Entomology in 1946 and the scope of activity was made to cover all work pertaining to all transmitting hum diseases or ai.noying man by their bites.

The State Board of Health's Entomological Research Center at Vero Beach was established in 1955 to study Florida's bitingin- sects, particularly mosquitoes, sand and yellow flies. The aim was to eliminate these nuisances from the Florida scene.The Encephalitis Research Center was established at Tampa in 1962 following an epidemic of St. Louis encephalitis to investigatethe viruses carried by arthropods and, if possible, bring aboutsome kind of control. The work of ihese centers will be discussed later in this issue of Health Notes.

Mosquito-The Villain

The mosquito is a long-time, undesirable resident of Florida. Humans living in the state have been swatting mosquitoes forgen- erations but eradication is most difficult. Thereare 67 species in the state and each has its own particular mating and breeding habits, living and resting areas, and itsown preference for food-

236 FLORIDA HEALTH NOTES a 6.

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This motorized vacuum machine has been developed by staffmembers of the State Board of Healthto collect blood-engorged femalemosquitoes from their resting placesamong woodland debris.

which may be humanblood. Seven of the 67 specieshave been im- plicated in the carryingof arthropod-borne diseaseswhich are seriously affecting humansand .

The Female is Deadly

As everyone knows, thefemale mosquito is theone that causes the problems because sheis the one that bites andcarries dise=ase. The male mosquito spendshis short lifeon the edge of breeding areas, mating with any female thatcomes near, sipping nectar from flowers and performinghis "twilight, dances."

Life for mosquitoes beginsas an egg laid on water or moist soil, or inside a can, tire, air plant, tree holeor most anything that holds water. The larvae, curledup inside the eggs, hatch atonce if in water or may stay thatway for weeks or months until rainor tidewater covers them. Thefree-swimming larvae,or wigglers, grow through several changes of skinin about five toseven days and change intopupae which look like animatedcommas. In a couple of days, the pupa's skinsplits up the back and outemerges the winged and "lance-equipped"adult mosquito.

FLORIDA HEALTH NOTES 237 a. ...,b.& 40'w

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a Ir ...--=1...... Mosquitoes are iden- tified and counted in several laboratories of the StateBoardof Health.

The newly-emergedmosquito must wait sixto eight hours before it can flyaway from the place of its birth.Then, if it is dark, it may migrate from twoto 10 miles. Entomologists,using radio- active means ofmarking mosquitoes,have found that will migrate some species up to 25 miles. The migrationsappear to be mechanical an urge to go somewhere.Following the migration, the female mosquitosettles down toa life of obtaining food, waiting for her eggs to mature and thenlaying them. Shegoes through several cycles of thisand then expiresat the ripe oldage of two or three weeks. Frequently the female needsa blood meal for hereggs to mature but this isnot true of all species. 238 FLORIDA HEALTHNOTES The elimination of themosquito from the Florida sceneis being researched and carried out in allstages of its life the egg, larvae, pupae and adult.The first three stages canbe accomplished by natural enemies of themosquito, such as fish, orwith larvicides ; removal of breedingplaces, such as ditchingand draining of swamps ; or removalof water-holdingcontl:zers left by humans.

The eradication of theadult is necessary becauseof the biting habits of the female orbecause of a suddenepidemic of encephalitis that does not allow timefor the reduction ofmosquitoes in their breeding places. Fogging andspraying therefore become necessary.

All techniques to controlmosquitoes must be safefor man and be harmless to valuable formsof life in the mosquito'senvironment. For example, whencontrolling pasture-breedingmosquitoes, other forms of wildlife must heconsidered at the sametime that mos- quito pro' action ishalted. When draining,filling or flooding marshes, other life in the swampsmust be considered.While useful forms of life must bepreserved, the applicationof insecticides, have a bene- such as the spraying ofhomes in malaria control, may ficial side effect by destroyingother domestic pests flies, roaches and ants.

Where Do MosquitoesBreed? As previously stated,each mosquito speciesprefers its ow n breeding place. Some aredomesticated and breed inand around the dwelling placesof humans or on landsconverted to human use, such as pastures, groves,ditches, drains or even inpolluted waters. Other mosquitoes preferwild lands, such as swamps,ponds and woodland poolsfar awayfrom man and his habitats.Some species are not particularand will breed in bothplaces. The Domestic Mosquito Aedes aegypti, the mosquitothat carries yellow feverand dengue fever, is the most domesticated.It breeds aroundman's home in cans, old tires,bird baths, drains, vases,tree holes, air plants anywhere water can collect.The eggs are laid on theside of the container, just above the waterline. The adult seldomflies from its breeding place. At the )1-,.-zt.t time there is anintensive federally-

FLORIDA HEALTH NOTES 239 supported program in Florida toeradicate A. aegypti. This cam- paign is part of a nationwide programbeing carried out to fulfill a commitmentunder interr ational treaty withSouth and Central American nations to eradicate theyellow fever carrying mos- quito from the Americas.

Culex nigripalpus, the mosquito implicated asthe carrier of St. Louis encephalitis in Florida, is a widebreeder. It likes all kinds of man-made places agricultural fields, irrigated pasturesand groves, fallow fields, grassyand drainage ditches, floatingexotic plants, home premises and polluted waters.

Culex quinquefasciatus, which transmitsbird malaria, fowl-pox and other diseases, breeds in temporaryreceptacles, drainage ditches and polluted water. It is also acarrier of St. Louis encepha- litis throughout the United States,but it has not yet been in- criminated in Florida.

The Salt Marsh Mosquito

Two of the greatest pest mosquitoes, Aedessollicitans and Aedes taeniorhynchus, usually breed in areas alongthe coast, marshes, swales and mangrove swamps, which may beflooded by rain or high tides (not normal tides) for a week orlonger. The most plentiful of any species, these two can up to25 miles.

The Freshwater Swamp Mosquito Aedes infirmatus and Aedes atlanticus,which are capable of carrying California encephalitis, and Aedes vexans,which trans- mits heart worms in dogs, are found intemporary freshwater pools and on river plains flooded by heavyrains. Some Psorophora species are also found in flooded fields,irrigated ditches and groves, and rain pools.

The malaria mosquito, Anophelesquadrimaculatus. is found in maple and gum swamps, freshwater marshesand ponds, lime sinks, flooded fallow fields, drainage ditches andfloating exotic plants. Anopheles crucians is found only in cypressand maple-bay swamps, fresh marshes and ponds, grassy ditchesand borrow pits.

240 FLORIDA HEALTH NOTES The Tree-Hole and Air-Plant Mosquito Where trees and air plants are found in great numbers, Aedes triseriatus and two Wyemoyia species, mitchellii and vanduzeei, breed and are found in vexing abundance.

The Intimate Life of the Mosquito

The control of the mosquito can be carried out in many ways but research can tell what is the best and most economical way to do it. Improvement in mosquito control has been the direct result ofre- search. The Entomological Research Center was set up by the State Board of Health 12 years ago to further research and control.

Much needs to be known about the insect to be controlled. Un- fortunately, because of her widespread movement, only a small fraction of the female mosquito's life has been known in the past mostly about her birth and the moment she bites you. How much knowledge of the intimate life of the mosquito where she goes, where she fee's, mates and lays her eggs has been acquired, but more needs toe known to bring her under man's control.

Mosquitoes are first studied in their natural habitat. These field studies bring out what needs to be clarified and verified in the laboratory. Through the raising of captive mosquito colonies, the process is refined. Problems are then brought back to the field for experiment and study in nature.

Out of this interplay between field and laboratory comes an im- proved understanding of the mosquito's total natural history. The mosquito is as complicated a creature as man and studies of the whole insect need the inclusion of such areas as endocrinology and metabolism before a complete understanding is reached.

This research is carried on in four sections at the famous En- tomological Research Center in Vero Beach.

The Ethology Section studies the life histories and habits of the mosquito. Among the special projects undertaken isa study of salt-marsh mosquito migration. The breeding, emerging and exodus

FLORIDA HEALTH NOTES 241 Mosquitoes are marked prior to being released from the rearingpens ofthe Entomological Research Center.

of the mosquito from themarsh is well understood, but theactual migratory flight occurs only at nightwhich makes its study dif- ficult. The final distribution ofmarked salt marsh mosquitoeshas been determined but the scientists areattempting to learn the whys and wherefores of long andshort migrations.

You may think that mosquitoeswill bite anything in sight. Studies are being made to find outwhether certain kinds of animals attract certain mosquitoes. Bloodspecimens from engorged mos- quitoes caught in the wild arematched with blood samples from birds and animals captured inthe same area to see if any real preferences exist. It is also important toknow the flight habits of the female once she has had a bloodmeal, and the type of shelter she seeks in which to rest.

242 FLORIDA HEALTH NOTES The EcologySection is concernedwith the mosquito's ment and the environ- effects of weather,tides, vegetation, soilsand anything else thatinfluences the mosquito's abundance. distribution and

The Physiology Section studies thebiological functionsfor a better understandingof the mosquito'sbehavior. being made into Inquiries are why some mosquitoesneed blood to makeeggs while others donot. This is tiedup with nutrition and hormones which are also under study. Thenutrition studies call forthe rear- ing of larvaewith precisionmethods in controlling light and diet. temperature,

The Biochemistry Section looks into themetabolic functioning of the female mosquito such as what doesshe do with nectar and blood meals. meals Answes to suchquestions as to howlong can a newly-emerged adult fly before needingfood, how longcan a mos- quito live withoutnectar to feedon, and how long live on its fat can a mosquito reserve have been found inthe laboratory.Now the Fntomo logicalResearch Center needs in the field. to establish theanswers

All of this researchis related to control search takes time. measures. Basic re- The practical,temporary controlmeasures of applied researchare sought at the WestFlorida Arthropod search Laboratory Re- near Panama City. At thislaboratory, the work is divided into two sections: mosquitocontrol and control ofbiting flies. The scientistslook for temporarymeasures, such as insecti- cides and landand water management,to control the biting The application insects. of insecticides indifferent concentrationsand by different methodsis studied to findthe effect chemicals the larval stage in have on swamps and on adults in theirresting places.

Temporarymeasures include:

The use of larvicidesto kill mosquitoes inthe early stages. are applied by air and These ground equipment.Applications must be thorough but heavyvegetation, winds andheat currents place Emit, tonson this type of, ,ntrol.

FLORIDA HEALTHNOTES 243 The use of adulticides applied as diluted mixtures of chemicals and oil by aircraft, ground blowers or fogging machines to kill adult mosquitoes in a specific area.Limitations, such as heavy canopy of trees, hot ground or wind, can restrict the effectiveness of these pesticides.

The methods of killing the villainous mosquito are not 100 per cent effective and there are always some mosquitoes left to assure more large broods which also periodically must be destroyed.

Research on the control of chironomid midges, sometimes called "blind mosquitoes" is carried on at the Midge Control Laboratory in Winter Haven.

Microbe-The Killer

If mosquitoeswere merely biting pests, they would be bad enough. But the fact that they carry disease is far more important. There are several arthropod-borne diseases which have proved fatal to man and animals in Florida, in addition to previously mentioned yellow fever, dengue fever and malaria but which, in contrast to these historic three, are still with us. These are the "arbovirus" encephalitides (sleeping sickness), St. Louis, California, Eastern, Venezuelan and Western. Another virus, Tensaw, has also been marked by epidemiologists as a potentially dangerous mosquito- borne disease.

These viruses are threats to man because the human popu'ation is rapidly spreading into areas which were until recent decades un- inhabited. Now abounding in drainage ditches, catch basins, arti- ficial water receptacles and impounded lakes and streams in addition to natural breeding places of mosquitoes, these areas add to the mosquito populations where men live.

244 FLORIDA HEALTH NOTES I IP

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Suckling m iceare raised in the virology -40 ;*-:- - laboratoryf o rthe testing for arboviruses.

Florida is also strategically located on the easternflyway of migratory birds traveling from the Northern and Southern con- tinents. Some of these birds are thought to bereservoirs of certain arthropod-borne viruses.

The epidemics of St. Louis encephalitis in theTampa Bay area resulted in the establishment of the EncephalitisResearch Center in Tampa which carries out and coordinates studiesof arthropod vectors, vertebrate reservoirs and human andanimal hosts of encephalitis viruses.

FLORIDA HEALTH NOTES 245 A ,colony of mosqui- toes, which have been raised in captivity, can be seen in the small cage. (Onopposite page) A worker places a pan of pupae in a large cage where adult mosquitoes will em- erge. The clock on the tableregulatest h e amount oflight the mosquitoes receive.

Statewide surveillances by the State Board of Health in Florida include work by

the Division of Veterinary Public Health, in the Bureau of Preventable Diseases, which maintains ch:cken sentinel flocks around the state to detect any activity of encephalitis viruses and collects reports from veterinarians of equine encephalomyelitis and possible encephalitis in game birds ;

the Division of Epidemiology, also in the Bureau of Preventable Diseases, which collects reports of suspectedcases of arthropod- borne viruses in humans from physicians, hospitals and County Health Departments ;

the Bureau of Entomology, which througha group of co- operators, collects, identifies and measures the density of adult female mosquitoes, and prepares pools of mosquitoes for viral studies ; and

the Bureau of Laboratories, which examines human and ani- mal (..,agnostic specimens and mosquito pools for arthropod-borne diseases.

246 FLORIDA HEALTH NOTES The Viruses

The St. Louis encephalitis virus, whichwas responsible for three epidemics in the TampaBay area in 1959, 1961and 1962, involving some 300 persons and 50deaths, is stilla major threat despite the fact that it has not been detected inFlorida in thy past fouryears. The reason for thisconstant threat is thatthe mosquito C. nigripal- pus, which has been declaredthe vector, is prevalent and urban in both rural areas of Florida. Migratorybirds, or birds fromthe Everglades,are presumed to be the reservoirsfor this virus. Older people, who have retiredto Florida, havea marked susceptibility to the disease. Mortalityaverages one in threecases and survivors have neurologicalor emotional defects for two lowing the illness. to three years fol- St. Louis encephalitisis a milder diseasein younger people. The control of this disease isimportant toour tourist-orientedeconomy.

i

FLORIDA HEALTHNOTES 247 0

A battery of tests is performed in order to isolate andidentify arboviruses in the Encephalitis Research Center's virology laboratory.

248 FLORIDA HEALTH NOTES Eastern encephalitis is with us all ofthe time andappears to circulate in a certain type ofswamp mosquito, Culisetamelanura. This insect rarelybites manor mammals unless they wander close to the too swamps. Seven persons havebeen stricken in thelast two years with this disease whichhas a 50 to 70per cent mortality rate in nationalstatistics. Althougha vaccination for horses has been developed, there are an average of 100 equinecases caused by Eastern encephalitis each year. The virusalso damages flocksof game birds, particularlypheasants and chukars a type of partridge. The virusapparently stays localizedin swamps but with housing projects being built closerto these areas, thedanger to man is increasing.

California encephalitisis a newcomer toFlorida andwas not recognized prior to1963. Four Floridapersons (three of whom came from North Carolinaafter exposure there)have been at- tacked by the virus. Epidemics have occurredin Wisconsin, Ohio and Indiana during the last fiveyears. Surveys show that fiveto six per cent of Florida's population have antibodieswhich indicate that they have beeninfected sometime inthe past. The mystery Why are not is: more people ill with the disease?The answer is possi- bly because laboratorytests sensitive enoughto detect the virus have not been found.Mammals, suchas small ground squirrels and wild rabbits, have been reportedas reservoirs for the virus inother parts of the UnitedStates but it is notknown what the is in Florida. The reservoir vector mosquitoesare freshwater Aedes, and California virus hasbeen found in themthroughout the state.

The Venezuelanencephalitis is foundrepeatedly in the Ever- glades by teams fromthe U. S. Public HealthService. The virus appears to circulate constantly between mosquitoes andsmall rodents. About 27per cent of the Seminole Indians,and a small number of rangers from the EvergladesNational Park, haveanti- bodies which indicate they have been infected.Carried by the pest mosquito, A. taeniorhynchds, the virusproduces widespread epidemics in Centraland South America.Symptoms are similar influenza. If the to virus ever got intoFlorida's plentiful saltmarsh

FLORIDA HEALTHNOTES 249 ....1111..1111D.HMOIHNINEN+4=0.4Uoo4M4044111.4111P.1110411MHNIM.oMH,.:. 1 I The best method of preventingmosquito biting and possible infectionI 1 is to: I I use repellents, i 1 wear protective clothing, 1 I avoid areas and times of mosquitoactivity (mostly at duskor 1 dawn) and I i get rid of standing water (breeding places) moundyour home. j j c. $

mosquito, public health authcrities,would have a major problem on their hands.

Westerr_ encephalitis has beenfound consistently in Florida since 1960. Antibodies in birdsshow that it is present in the biological environment but to date the onlymammals involved have been horses. in the Great Plains andthe West, the virus has causeda great deal of sickness in humansand horses.

Lesser Microbes

The Tensaw virus, found inAnophelesmosquitoes, is presumed to have a mammal-mosquito cycle.Only one humancase has been found in Florida despite the factthat it is abundant throughout the state and antibodiesare found in three to five per cent of the population. The viruswas also found in a dead fox submitted for rabies studies. It does notappear to present a human or health problem at thepresent time.

Yellow fever and dengue feverhave ceased to bea threat to Florida although theyare found in the Caribbean Islands. Yellow fever was lastseen in Pensacola in 1905 and dengue made its last appearance in Miami and the Tampa Bayarea in 1934. However, in 1964, two Florida residentscame down with dengue fever after returning from Puerto Rico andJamaica where epidemicswere raging. The last case of mitlariawas contracted in southwest Flor- ida in 1948.

250 FLORIDA HEALTH NOTES Surveillance for Viruses

Utilizing reports from physicians, hospitals and County Health Departments in the Tampa Bay area, the Encephalitis Research Center keeps a watch over people and animals in the West Central area of the peninsula.Approximately 1600 persons have been so eened for arthropod-borne diseases in the last four years. Be- cause the viruses do not always produce illnesses in people, speci- mens al e taken from approximately 400 healthy persons in the Tampa Bay area once a year to see if they have developed silent infections or antibodies. I i Mosquitoes are collected at regular intervals from various kinds I oftraps geographicallyscattered throughout Pinellas,Hills- , borough, :Manatee and Sarasota Counties. Over one million mos-

1 quitoes have been trapped in the past four years and all species have i been examined for viruses. The mosquitoes are separated into species and then separated by sexes. The females are put into pools of 50 and 160 mosquitoes, which are mixed together and inoculated into baby mice. If the mice become sick and die, the virus is be- lieved to be present. If subsequent tests are positive, the viruses ale isolated and identified. Seven viruses can be identified in the Encephalitis Research Center's virology laboratory; other types are sent to the U. S. Public Health Service, Communicable Dis- ease Center laboratories, Atlanta, a national laboratory at the University of Pittsburgh, or the international laboratory at Yale University.In the past four years, three previously unknown viruses have been discovered in Florida in ticks, mosquitoes and cotton rats through the efforts of the Encephalitis Research Cen- ter.

Biologists at the Center in Tampa attempt to detect current and 1 past virus infections in mammals, birds and amphibians. Chickens, rabbits and pigeons have been placed in cages in wild areas to detect arboviruses in wild mosquitoes. Wild anim=als and both resident and migratory bird: are col:ecied, Lied, tz,gged and released. No halm is done to the buds and someties the same bfrd is caught 1 i epeatedly. Over a period of three years one small bird was caught and bled 18 times without harm by the iiologists. The blood

FLORIDA HEALTH NOTES 251 si mules from these animals and birds are examined for the presence of virus or antibodies to viral infections.

The State Board of Health, through its variousbureaus and divisions, continues to look forways of interrupting the trans- mission of viruses in the mosquito-bird-man cycle. Thisseems to be the most practical way of protecting the citizens of Floridafrom encephalitis.

What Mosquito Control Meansto Florida

One of the most important key factors to theexpansion of the Florida economy is mosquito control. Suchmen as Henry Flagler and H. B. Plant, whocame to Florida with money to invest, looked to the State Board of Health forproper sanitary regulations that assisted in the building of hotels and thevast railroad systems. Today's tourist industry takes it forgranted that the State Board of Health and the local mosquito controldistricts will not let it clown by permitting either mosquitoesor the diseases they carry to take the state over again and keep it in chainsas they once did.

There is no question that control of the mosquitohelped open up the state to the planting of citrus, mining ofphosphate, cutting of virgin pine and cypress and the startingof the cattle industry. Most of all, the control of arthropods andarthropod-borne diseases opened subtropical Florida to people from allover the United States and the world who come to enjoy the climate,good fishing, excel- lent beaches and unsurpassed beauty. I

The State Board of Health, mosquitocontrol districts and the Boards of County Commissionersare spending approximately $8 million annually for control ofmosquitoes and other forms of arthropods. Fifty-seven mosquito controldistricts, operating in 54 of the 67 counties, applied inone year over three million gallons of insecticide formula by air and groundfogging and spraying to

252 FLORIDA HEALTH NOTES A rabbit (1), which has been used itii-I-rh6. as bait to attract mosquitoes, is s 4 removed from a trap ina swampy ;,:. .. area.(2) Mosquitoes, whichcare sucked by a vaccum intoa bag I-, before they can attack therabbit, are removed from the trap.(3) F The entomologistchecks the operations of a tent trap.

kill adults andover 723,000 pounds of Parisgreen pellets to kill larvae. Over threemillion acreswere treated by airplanes andover 389,000 mileswere traveled by ground foggingmachinery. By

FLORIDA HEALTH NOTES 253 contrast, 15 yearsago, the State Board of Health andother agencies spent about one milliondollars for arthropod control.

It is apparent thattime, effort andmoney expended in con- trolling the mosquitoand the diseases it carrieshave brought results. But furtherresearch and controlare necessary. The State Board of Health mustmaintain protection againstmosquitoes and increase its strides inresearch in order toprotect the health and comfort of Florida residentsand tourists.

Definitions fur Some TermsWe Used

IAdulticidean insecticideor pesticide which kills adult insects. 1 Antibodya factor (globulin)in the body which is produced I by a past infection or the administrationof an antigen, suchas a vaccine. IArbovirus--an infectious I agent carried by arthropods. Arthropoda member ofa group of invertebrated crmtures with I jointed legs and segmentedbodies; insects, ticks, etc. Arthropod-borne diseasesdiseasescarried by anyone member of the 1 arthropod family. 1 Encephalitisan inflammationof the brain often causedby the / presence of a virus, whichmay be arthropod-borne, sometimes I called sleeping sickness. I Endocrinologythe study ofhormones and their effecton the body. fLarvicidea chemical which I kills insect larvae. IMetabolismthe chemicalprocess by which food is burned in the body to release energy. 1 $ Microbesa microorganism(for example, virus, bacteria,rickettsia) i which maycause disease. IReservoira creatureor animal in which a virus lives and multiplies 1 without doing damageto the host. I Vectoran agent, suchas a mosquito, capable of transmittinga 1 disease fromone host to another. Virusa submicroscopic infectiousagent which can cause disease.

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254 FLORIDA HEALTH NOTES FLORIDA STATE BOARD OFHEALTH HON. CLAUDE R. KIRK, JR. Governor of Florida

BOARD MEMBERS Eugene G. Peek., Jr., M.D., President Ocala T. M. Cumbie, Ph.G., Vice-PresidentWilliam 0. Shumpert, D.D.S., Member Quincy Ft. Lauderdale Leo M. Wachtel, M.D., Member W. S. Horn, D.O., Member Jacksonville Palmetto STATE HEALTH OFFICER Wilson T. Sowder, M.D., M.P.P. DEPUTY STATE HEALTH OFFICER Malcolm J. Ford, ILIA., M.P.H.

OPERATING UNIT DIRECTOR ADMINISTRATION G. Foard McGinnes, M.D., Dr.P.H. Progi am and Planning Assistant State Health Officer Office of Operations Division of Health Education G. Floyd Baker, M.P.H. Division of Personnel . MilesT. Dean, M.A. Division of Public Health Nursing Enid Mathison, R.N., M.P.H. BUREAU OF LOCAL HEALTH SERVICES Malcolm J. Ford, M.D., M.P.H., Deputy State HealthOfficer and Director Division of Nutrition . Mildred Kaufman, M.S. Division of Sanitation . A. W. Morrison, Jr., R.S. BUREAU OF ADULT HEALTH AND CHRONICDISEASES J. E. Fulghum, M.D. BUREAU OF DENTAL HEALTH Floyd H. De Camp, D.D.S. Delmar R. Miller, D.D.S., M.P.H., Assistant ENCEPHALITIS RESEARCH CENTER James 0. Bond, M.D., M.P.H. Assistant State Health Officer BUREAU OF ENTOMOLOGY John A. Mulrennan, B.S.A. BUREAU OF FINANCE AND ACCOUNTS .... Fred B. Ragland, B.S. Paul R. Tidwell, B.B.A., Assistant BUREAU OF HEALTH FACILITIES ANDSERVICES C. L. Nayfield, M.D., M.P.H. BUREAU OF LABORATORIES , . . . Nathan J. Schneider, Ph.D., M.P.H. Warren R. Hoffert, Ph.D., M.P.H., Assistant BUREAU OF MATERNAL AND CHILD HEALTH J. E. Fulghum, M.D., Acting BUREAU OF NARCOTR Frank S. Castor, Ph.G. BUREAU OF I'REVENTA: DISEASES Wilson T. Sowder, M.D., M.P.H.. Acting Division of Epidemiology E. Charlton Prather, M.D., M.P.H. Division of Tuberculosis Control Dwight Wharton, M.D. Division of Radiological Health Edwin G. Division of Veterinary Public Health James B. Nichols, D.V.M. BUREAU OF RESEAPC! Wilson T. Sowder, M.D., M.P.H., Acting BUREAU OF SANITARY ENGINEERING _ . David B. Lee, M.S. Eng. Sidney A. Berkowitz, M.S. Eng., Assistant Division of Industrial Waste Vincent D. Patton, M.S.S.E. Division of Special Services Charles E. Cook, C.E. Division of Water Supply John B. Miller, M.P.H. Division of Waste Water Ralph H. Baker, Jr., M.S.S.E. BUREAU OF VITAL STATISTICS Everett H. Williams, Jr., M.S. Hyg. Division of Data Processing Harold F. Goodwin Division of Public Health Statistics Oliver H. Boorde, M.P.H. Di wision of Vital Records Charles H. Carter Post Office Box210Jacksonville, Florida 322C1