FUMIGATION OF VESSELS FROM PLAGUE-INFECTED PORTS. OBSERVATIONS WITH ESPECIAL REFERENCE TO THE NECESSITY FOR FUMIGATING CRATES AND SIMILAR CARGO.

By S. B. GRUBBS, Surgeon, United States Public Health Service.

Fumigation is the chief defense of this country against bubonic plague. It is efficacious in proportion to the thoroughness with which it is done, as good results require not only a knowledge of proper methods but a conscientious and painstaking insistence upon details. Rats hide in the small inclosed spaces of a vessel, such as double walls, pipe casings, and limbers, and the gas will not penetrate into these places if, on account of cargo, they can not be opened to allow the gas to enter. The presence of cargo does not affect the fumigation of storerooms and living quarters, which frequently harbor rats in relatively greater numbers than the holds.

In allowing freight to be discharged before fumigation, a certain risk is taken, which is increased if there are crates or other articles. into which rats can enter and thus be carried ashore. Consequently, when the vessel is from a port with a definite infection, this dangerous freight should be fumigated. This may be done either on shipboard or upon lighters, according to circumstances.

In the plague campaign in Porto Rico in 1912, one of the first steps taken to prevent spread inland was to open and repack all crates bound from San Juan to the interior of the island. The discovery of a number of rats in these crates caused us to begin the fumigation of all such freight arriving from the Canary Islands, which were believed to be the original source of infection.

Various methods were used at different times. Sulphur dioxide, in a warehouse or on lighters under a tarpaulin, was efficient, but required long exposure and did some injury. Cyanide gas was a great improvement and was used either on lighters or in a galvanized iron shed erected especially for this purpose. This practice was continued for several years, and the reinfection of Porto Rico in 1921, believed also to have come from the Canary Islands, followed shortly after its discontinuance. At present, dangerous cargo is fumigated on arrival at San Juan, and it is described by Surg. C. M. Fauntleroy, as follows:

"The routine practice of fumigating all crated cargo, and especially crated packages of foods such as onions, garlic, and potatoes, brought to Porto Rico in Spanish vessels from ports in Spain and the Canary Islands, was instituted at San Juan about 18 months ago, for the reason that the epidemiological data secured as the result of a study made to determine the source of plague infection in Porto Rico at that time, and also again in 1921, pointed very conclusively to this cargo originating either in the ports of Spain

or the Canary Islands; for example: In both of the plague outbreaks in Porto Rico, mentioned above, plague rats were destroyed in certain warehouses in San Juan where the cargo referred to was being stored in large quantities.

"In the outbreak of 1921, the original focus of plague infection. was located in and about a wholesale provision store at No. 43 Tetuan Street, where large amounts of crated foods were regularly received and stored and which originated either in Spain or the Canary Islands. Therefore, in view of the facts above stated, it was deemed a matter of great importance that all cargo brought to Porto Rico in Spanish vessels should be carefully fumigated for the destruction of rodents prior to allowing such cargo to be landed, and my experience in the fumigation of several hundred lighters loaded with the cargo in question, has convinced me that this cargo landed from Spanish vessels may, and does, furnish harborage for rodents, and, hence, it provides a means of conveying plague infection."

In 1920, freight arriving at Cristobal, Canal Zone, from Paita, Peru, was fumigated on lighters. Paita was then badly infected; but as there were no large docks, rats could reach the ships only by lighters or in freight. On arrival at Cristobal, such vessels discharged safe freight upon the dock, and unsafe freight into lighters lying on the free side of the ship. The freight in the lighters was fumigated before being transferred to the dock, and the vessel was fumigated when entirely empty. This arrangement was discontinued only when the periodic fumigation of all lighters at Paita was instituted, together with the examination or fumigation of all outgoing freight. As usually only a small part of a mixed cargo may harbor rats, it is frequently more convenient to leave the dangerous cargo on board to be fumigated in the holds after all or part of the safe cargo has been discharged. If much freight is left on board, several fumigations will be necessary.

Fumigation of cargo in lighters is not a difficult procedure. If closed lighters are available, they should be sealed up and fumigated in the ordinary way. If open lighters must be used, the cargo should be covered with large tarpaulins to make a tent, and cyanide generated underneath. To insure good results, the freight must be piled so as to leave air spaces and passageways for the circulation of the gas; but this must be carefully confined by sealing all cracks in the covered lighters, or by fastening the tarpaulins carefully, especially to the deck, battening them down with reasonably heavy timbers or with boards with weights upon them.

• On account of the recent outbreak of plague at Barcelona, Spain, it has been necessary to take special precautions at New York with vessels arriving from that port. Measures begun in October, 1922, which include the fumigation of dangerous cargo, have been changed

but slightly, and these fumigations have resulted in no serious delays, such as are usually considered justified under similar circumstances. Our procedure for such ships is as follows:

1. On arrival, the boarding officer obtains a cargo stowage plan and notifies the chief of the fumigation division, who personally boards the vessel and examines the manifest and holds to see if the vessel can be fumigated without removing any cargo.

2. Immigration and custom officials are permitted to board the vessel to complete their work.

3. Ship is held in stream on day of arrival and not permitted to dock until early next morning.

4. If not prepared to fumigate at this time, on account of deck cargo or holds that are filled to hatch coaming, the ship may discharge the deck cargo and barreled or case goods from the holds until the square of the hatch is clear, during daylight hours under the supervision of a guard.

5. Ship to pull out in stream at 4 p. m. if not fumigated the same day.

6. Fumigation of whole ship to be started promptly at 9 a. m., when the ship is prepared, four hours' exposure, and prolonged blowing out with aerothrust. When possible, the generating machine on the fumigating tug Von Ezdorf is to be used in conjunction with the usual method; the hose from the generator to be inserted into a ventilator opening to get gas beneath cargo at the same time it is generating in the square of the hatches.

7. The day following fumigation, two fumigators are to stand by with gas masks to recover additional rats or to run aerothrust if stevedores complain of gas while working cargo.

8. In event of live rats being seen by guards on watch, during discharge of cargo, the discharge is to be stopped and the vessel refumigated. This fractional fumigation is to be repeated at any time when, in the opinion of the fumigating officer, the cargo is such that the gas will not penetrate thoroughly.

9. When holds are completely filled with cargo that may harbor rats, such as bags of almonds or crates of vegetables, enough cargo must be discharged into lighters to permit the fumigation of the ship, the lighters to be fumigated when loaded.

10. When the ship in question carries cargo and passengers in transit, it will be treated as follows:

a. Either ship will remain in stream where New York cargo will be discharged into lighters and fumigated; or

b. The ship may go to the dock, if holds are not completely filled with cargo, and be fumigated there after crew and passengers have been removed.

11. Ship, in all cases, to be fumigated throughout after complete discharge of cargo.

Referring to paragraph 6 of these instructions, it should be noted. that this first fumigation is complete in regard to superstructure, no space being omitted, unless the presence of rat harbors can be absolutely excluded by inspection. In preparing for this fumigation, all

inclosed space, such as double walls, must be opened to allow the gas to enter. In addition, while fumigation is in process, a careful search for rats is made in all parts of the deck, especially in boxes, vegetable bins, and life boats. The above is required in all our fumigations, but is stressed in vessels from badly infected ports.

With the superstructure and deck free from rats, it is considered safe to allow the vessel to discharge at the dock as usual, provided any cargo that may harbor rats is fumigated, as previously described, and the vessel itself again fumigated when entirely empty.

Report on two of the vessels treated by this procedure may be selected as examples. They are as follows:

American S. S. City of Eureka:

October 29, 1922: Inspected and held in quarantine.

October 30, 1922: Docked. Complete cyanide fumigation, 5 ounces per 1,000 cubic feet. Result, 25 rats.

October 31, 1922: 16 rats discovered while discharging.

November 8, 1922: Fumigated at Baltimore after complete discharge of cargo.

Result, 4 rats.

One fumigator on guard before fumigation: two fumigators with gas masks on guard for 24 hours after fumigation.

Norwegian S. S. Bessegen:

December
December

8, 1922: Inspected and held in quarantine.

9, 1922: Docked. Complete cyanide fumigation before discharge of cargo. Four hours' exposure. Barrel generators in holds. Hose from fumigating tug's generator put down ventilator pipes. Total dosage for holds, 15 ounces per 1,000 cubic feet. Superstructure, complete fumigation, 5 ounces per 1,000 cubic feet. Two hours' exposure. Result, 4 rats.

December 10, 1922: Sunday. Cargo not worked. One guard on boat. Hatches

open.

December 11-15, 1922: Discharging. No rats recovered.

December 16, 1922: Complete fumigation empty. Result, 5 rats.

In comparing the results of fractional fumigations of several vessels with the results obtained when the same ships were previously fumigated at New York after discharge of cargo, it has been observed that, as a rule, fractional fumigations yield more rats. Of the vessels treated, we have records of previous fumigations of but six. If these are typical we must ask ourselves if too many rats do not escape either in the freight or by other means before "fumigation after discharge."

This article has been prepared to emphasize the necessity, under certain conditions, of fumigating cargo and to submit a procedure for handling vessels from plague-infected ports which gives a large amount of protection without excessive delay or expense.

It is also hoped that observations upon the efficiency of fumigation may be stimulated and the results reported.

NOTE. All records and tables given in this paper were prepared by Acting Asst. Surg. S. B. Doyle, in charge of the fumigating division, New York Quarantine Station.

INFLUENZA IN THE UNITED STATES.

The accompanying table shows the numbers of cases of influenza reported by telegraph by State health officers for the three weeks ended January 6, 1923, compared with the reports for the corresponding period of the two preceding winters.

A similar table covering the period from October 1 to December 23, 1922, appeared in the Public Health Reports December 29, 1922, pages 3204-3205.