Malaria Control

-What Might Be Done In Pacific Where Actually No United Effort Has Yet Been Made.

Letter to the Editor.

IN my letter relating to “Planes as Germ Carriers”, precautionary mea sures (other than fumigation) and control measures in the event of yellow fever being introduced are suggested.

Possibly, the medical authorities in each service have plans, in the event of the introduction of yellow fever; but as such plans must depend upon the whole hearted support of the Europeans of the group, I have decided to submit the following.

The precautions could go hand in hand with fumigation, and in some instances might even make fumigation unneces sary.

Each airport would have its special peculiarities in regard to mosquito con trol. The common vector of yellow fever is aedes aegypti, and evidence exists from recent epidemics that a similar type of mosquito could transmit the disease. There may be other kindred mosquitoes capable of transmitting the disease; consequently thorough eradi cation of all types of mosquitoes at air ports should be the objective. Complete eradication would also eliminate malaria and filariasis.

This would rest with the sanitary en gineers; but eradication could commence with attacking the breeding grounds of the known vector of yellow fever, which exist in the vicinity of the airports. The common vector, aedes aegypti, breeds in artificial collections of clean water.

Tanks, water jugs, flower vases, water barrels, holes in trees, coconut husks, old tins and bottles are the principal breeding places. In most homes they breed in tanks, water-jugs, defective guttering, flower vases and water barrels; but, if denied these, they resort to other breeding-places mentioned.

It will be understood, therefore, that eradication of the known yellow fever mosquito would be a comparatively simple matter. Screening of tanks and water barrels, and the remedying of defective guttering, are permanent measures to be instituted. Usually, there are not many trees in the vicinity of airports; but garden plants, espec ially plants of the lily variety, and palms which will retain water in holes, or where the branches or fronds join the trunk, should not be grown.

Water jugs and flower vases can only breed mosquitoes if the water is un changed for such a period as to allow the mosquitoes to develop from eggs, larvae and pupae. Consequently, com plete emptying of jugs and vases should be done every morning before they are refilled. Tins should be well punctured, and bottles placed in such a position that they will not retain water. There are various ways of disposing of coco nut husks.

Usually, the vector of yellow fever is the chief annoying pest. It also carries dengue fever. They are always in the homes, and are the most difficult mos

quitoes to land direct hits on. Environ ment and much practice have made them most elusive. They are striped black and white, something like a tiger.

During daylight is their feeding time, but, if starved, will bite at night. Con sequently, people could visit houses where people are sick with yellow fever, with a fair degree of safety during the night. It usually remains in the house in which it breeds, but will make ex cursions to houses in the immediate vicinity. This is only of importance in villages.

A good rough method of determining whether aedes aegypti are breeding in tanks is: Strike the tank at water level a few times, wait a little while and then turn the tap on. The larvae of this mosquito are deep divers and, if present, some will come through the tap.

They can remain submerged for about one hour. The larvae have many natural enemies, such as fish, etc.

While in Tonga I was impressed by the absence of larvae in many un screened tanks and wells. A few natives told me that a water beetle was re sponsible for this. These water beetles lived chiefly in the mud, on the bottom.

One of these beetles was placed in a pickle bottle and fed on biscuits, and it then devoured 60 larvae in 12 hours. Of course, the larvae and beetle were only in a confined space.

A thorough investigation of natural enemies of the mosquito larvae would be most valuable.

No doubt I have omitted some “artificial collections of clean water” as breeding places. Canoes on the beach,

for instance. But, if any are interested, the house-boys could be shown larvae and then encouraged to report the existence of them. Don’t offer rewards.

The natives have been guided by Nature and environment, and they like a change from housework. This could also be done on plantations.

In the event of yellow fever being in troduced into any of the islands, the first concern of the medical authorities would probably be to prevent the vectors of yellow fever biting persons with the disease within the first three or four days (the infective stage). This may be done with mosquito nets and screen ing of hospitals. To prevent infected mosquitoes from biting others, fumi gation of houses of infected patients would be necessary. Probably fumi gation of whole villages or collection of villages would be better. Unless fumigation was rapid in effect, con siderable difficulty would be experienced in fumigating reed houses. If fumi gation was slow in action, infected mos quitoes would move to other houses.

I am, etc.,

William J. Tully.

16 Bridge Street, Sydney.