MALARIA.

The investigations of malaria during the past fiscal year have been conducted from the headquarters at New Orleans, La. As in previous years, they have been carried out in cooperation with the health authorities of the States and localities concerned.

Surg. R. H. von Ezdorf has been in general charge of the malaria investigations. Asst. Surg. Gen H. R. Carter has from time to time continued studies on the relation of impounding reservoirs to the prevalence of malaria, having the assistance of members of the general force. This force is now composed of the following persons: Asst. Surg. R. C. Derivaux, Sanitary Engineer J. A. A. LePrince, Technical Assistant M. B. Mitzmain, and Assistant Epidemiologist T. H. D. Griffitts.

In order to facilitate the compiling of observations an outline suggesting lines of research was prepared and furnished to each member of the force engaged in field and laboratory work. In this outline the subject is considered under three general heads, namely: Epidemiology, methods of control, and laboratory investigations.

The epidemiological investigations include observations to be made of the several species of anopheles mosquitoes prevailing in relation to disease propagation; their selection of breeding places; flight; hiding and resting places; habits in relation to man and his environment; attraction and repulsion; hibernation; food; geographical distribution; seasonal prevalence—all as influenced by meteorological and topographical conditions.

The control investigations include studies of the relative value of protective measures, such as screening methods and material; traps; oiling; larvacides; use of natural enemies of mosquitoes; general measures of drainage and filling; light and odors; hand destruction; and fumigants.

Laboratory investigations include the study of the life of infected anophelines and all conditions influencing them.

In the hospital cases of malaria are being studied with reference to immunity, effects of remedies, and their methods of administration. Economic studies in connection with field surveys are also being made, and data from all available sources, including insurance companies, are being collected.

SURVEYS.

A number of requests were received from State and local health authorities for anopheline mosquito surveys in relation to malaria and for advice as to the best measures for the control of the disease. Preference was given to places where officials gave promise of undertaking antimalaria measures on lines recommended. Thirty such surveys were made in 12 States, as follows:

Alabama: Mobile, Fulton, Lanett, Tuscaloosa, Kaulton, Holt, camp at Lock 12, Coosa River.

Arkansas: Newport (relief committee), State penitentiary at Cummins. Georgia: Waycross, Brunswick.

Maryland: Baltimore, Anne Arundel County.

Mississippi: Cedars, Electric Mills, Lucedale, Deer Island near Biloxi, Columbus.

North Carolina: Roanoke Rapids.

Ohio Toledo.

South Carolina: St. Helena Island.

Virginia: Emporia, Wilson, Toshes, Nathalie.

Louisiana: Bastrop, Mandeville.

Missouri: Crystal City.

Texas: Dallas, Sherman.

In most of the places where surveys were made a report of conditions, together with recommendations for the abatement of mosquitobreeding places, was submitted to the mayor and the local health officer.

Antimosquito measures.-The measures generally recommended are, briefly, the following:

(a) Regrading and training of streams, creeks, or similar natural watercourses so as to favor a free current.

(b) Drainage for the removal of standing water or to produce a movement of water unfavorable to mosquito breeding.

(c) Filling in of low places that are too low to drain or which can not be drained economically.

(d) Oiling and larvacides.

(e) Natural enemies: Stocking with top-feeding minnows is a measure applicable in certain ditches, ponds, pools, swamps, streams, and many other bodies of water.

DEMONSTRATION WORK.

Roanoke Rapids, N. C., and Electric Mills, Miss.-The work of controlling malaria by the application of measures directed against anopheline mosquitoes at Roanoke Rapids, N. C., and Electric Mills, Miss., mentioned in the last annual report,1 was continued by the local authorities.

At Roanoke Rapids, N. C., a further decrease in the incidence of malaria was shown. The malaria index at this place, as shown by blood examinations in 1913, was 13.75 per cent; in 1914, 4.4 per cent; and in 1915, 3.5 per cent-a decrease in incidence of 74.5 per cent.

At Electric Mills, Miss., the malaria index for 1914 was 11.76 per cent and for 1915, 3.97 per cent—a reduction of 67.7 per cent in the incidence of carriers.

In both places an increase and permanency of population and an increase in the efficiency of labor were noted.

Crystal City, Mo.-On request of the Pittsburg Plate Glass Co., operating a plant at Crystal City, Mo., a malaria survey was made in that city in December, 1915, and plans, recommendations, and estimates of cost submitted. An index secured showed 36 persons, or 5.62 per cent of the 640 persons examined, to harbor the parasite of malaria.

Active ditching work was begun by the company early in the spring under the supervision of officers of the service. The company will probably expend about $10,000 for its first year's work, including the cost of some ditching for purely agricultural purposes.

Dallas, Tex.-In order to carry out measures recommended following a survey made by the service at Dallas, Tex., the city commissioners appropriated on May 1, 1916, $4,500 for antimalarial work.

1 See also Reprint No. 328 from the Public Health Reports.

Bastrop, La-Some antimalaria work has also been undertaken at Bastrop, La.

Cedars, Miss.-Experiencing difficulty in operating their plant on account of malaria among the employees, the Mississippi Veneer & Lumber Co., operating a mill at Cedars, Miss., made request for a survey and advice as to remedial measures.

A malaria index was made by the service, in which the blood of 119 persons connected with the mill was examined microscopically. Forty were found to be carriers, equal to 33.6 per cent.

In accordance with suggestions given, screening of houses, including porches, of white residents was begun in March, 1916. Persons found by blood examination to be carriers were given 5 grains of quinine each daily for two months, during March and April, after which they and all others were given 10 grains a day on two consecutive days each week. No employee is retained by the company unless he consents to take quinine as advised; three persons refused and severed their connection with the company. The company collected 50 cents per month for the curative treatment of carriers and 25 cents per month for quinine furnished for prophylactic (immunization) use.

It has been noted that the health of employees is greatly improved. No malaria had occurred among them up to July 1. Further data will be available at the end of the season.

COOPERATION WITH INTERNATIONAL HEALTH COMMISSION.

The International Health Commission, through Dr. Wickliffe Rose, requested the advice and cooperation of the United States Public Health Service in demonstrations financed by the commission, showing the relative value of various measures used in the control of malaria.

Accordingly, two places for conducting the work were selected, one at Crossett, Ark., representing a town unit, where drainage and oiling are the chief measures; and the second, a number of small plantations near Lake Village, Ark., representing strictly rural conditions, where each family in a house is considered individually and where screening and quinine are the main measures.

One field director has been appointed for each place, and the work is being directly supervised by Asst. Surg. R. C. Derivaux. The work was begun March 20, 1916. Inspections are made each month to follow the progress of the work.

EDUCATIONAL MEASURES.

In connection with the other duties, illustrated lectures dealing with the subject of cause and prevention of malaria were given in a number of places visited during the year. Among thein may be mentioned Guyton, Sylvania, Waynesboro, Millen, Statesboro, Metter, Claxton, Pembroke, Reidsville, Ludowici, and Darien, Ga. Lectures were also given in two towns in Leon County, Tex., where some malaria-control work is being undertaken locally.

Addresses have also been made before business men's leagues, chambers of commerce, women's clubs, and like organizations, dealing with the economic and business aspects of malaria.

It has been found that towns having few different industries, such as cotton mill, lumber mill, or glass factory towns, are much more active and desirous of undertaking antimalaria work than the ordinary towns. There is apparently a marked apathy among officials of ordinary towns as compared with towns controlled by manufacturing interests, where the commercial viewpoint in the value of disease prevention is appreciated.

In rural districts, where malaria is a real problem, cooperation is oftentimes difficult to obtain because of the expense required in improving housing conditions and the intangibility of the returns.

RESULTS OF RESEARCH WORK.

Numerous problems of importance and interest relating to malaria have been determined during the year, and in some cases reports of the results published. A summary of results follows:

Determination of infectibility of Anopheles punctipennis.—The determination of the infectibility of Anopheles punctipennis was begun early in the year and completed in January, 1916. Technical Assistant M. B. Mitzmain found Anopheles punctipennis to be infectible to the Plasmodium vivax (tertian malaria) parasite and not to the Plasmodium falciparum (subtertian malaria) parasite. Mr. W. V. King, United States Agricultural Department, reported a month before (December, 1915) that he had succeeded in infecting Anopheles punctipennis with both species of parasites.

Infectibility of Anopheles crucians. In the course of his investigation Mr. Mitzmain found that Anopheles crucians was infectible to the Plasmodium vivax (tertian) and Plasmodium falciparum (subtertian) parasites.

Transmission experiments with Anopheles punctipennis.-Transmission experiments with Anopheles punctipennis were also carried out. It was determined that:

(a) An Anopheline (A. punctipennis), once infected, probably remains so and can transmit the (sporozoite form) parasite repeatedly, as instanced in the successful inoculations of 13 persons through the bites of 1 or 2 infected mosquitoes.

(b) An infected Anopheline can transmit the infection after a very short bite, before obtaining a feed of blood. Eleven persons were infected following interrupted bites of 1 or 2 mosquitoes within 30 seconds to 1 minute and 20 seconds; 4 persons were infected by the successive interrupted bites of 2 mosquitoes applied in the course of 2 hours and 30 minutes; and 2 persons were infected by the interrupted biting of 1 mosquito within 5 minutes.

(c) The incubation period was nearly the same for all 14 persons, between 13 and 19 days, averaging 14 days.

Hibernation studies.-Hibernation studies, involving the dissection of 1,582 specimens of hibernating anophelines and the examination of the blood of 1,184 persons, indicated the following:

(a) Malaria parasites are not carried over from fall to spring in the body of the mosquito.

(b) The Plasmodium remains latent during the winter in the blood of man, as proven in this investigation, wherein 492 persons were found to be infected.

Further laboratory studies of Anophelines.-Other results of laboratory studies of anophelines showed that:

(a) Gravid anophelines subjected to temperatures of 4.5° C. to 12.5° C. did not lay eggs; but with a rise of temperature between 16° C. and 21° C. egg laying was increasingly favored. This confirmed field observations, where it was found (in Scott, Miss.) that anopheline breeding commenced when the mean atmospheric temperature reached 16° C. (after Apr. 15).

(b) Anopheles punctipennis females were kept alive on a blood diet, 1 for 82 days and 1 for 111 days; an Anopheles quadrimaculatus was kept alive on dates and water 68 days; 1 male Anopheles quadrimaculatus survived 62 days and 1 male Anopheles punctipennis 64 days.

Flight of Anopheles quadrimaculatus.-Some interesting observations of practical importance regarding anophelines as carriers of malaria were also made during field investigations. In one instance it was seen that Anopheles quadrimaculatus, both males and females, are capable of flying a direct distance of 3,000 feet.

Breeding places of Anopheles punctipennis.-Asst. Surg. Gen. H. R. Carter, in charge of the studies of impounded waters and their relation to malaria during the year, called attention to the preference of Anopheles punctipennis for breeding along rapidly moving watercourses, such as creeks, while Anopheles quadrimaculatus rarely did

SO.

He also collected definite data showing that Anopheles punctipennis is infrequently found in human habitations, whereas Anopheles quadrimaculatus is commonly, if not almost exclusively, found there. These observations applied to districts where both species were present.

This was confirmed in surveys by other members. Further observations will be made on this point, as it will be of great sanitary importance in considering control measures. The determination that Anopheles punctipennis can be infected with the Plasmodium of malaria may then have only a scientific interest, and may not prove of epidemiological importance.

Importance of these field observations.—It can be seen that, if the two field observations regarding Anopheles punctipennis are confirmed, much money will be saved to communities undertaking antimalaria work.

Similar observations regarding habits of Anopheles crucians are being followed which indicate that this species is, in a degree, of negligible importance in the spread of malaria.

There appears to be no doubt that Anopheles quadrimaculatus is the chief species in the southern States concerned in the transmission of malaria.

Types of infection. In response to a request by circular letter, mailed to physicians representing every parish in the State of Louisiana, requesting them to furnish blood smears from their active and chronic cases of malaria-slides, slide boxes, history blanks, and franks for mailing being furnished-300 blood smears were received, of which 84 from 18 parishes were found to be tertian; 43 from 13 parishes, estivo-autumnal.1

1 There is a total of 64 parishes in the State.