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THE HONGKONG WEEKLY PRESS AND
mountain torrent on the rare occasions when this is necessary, form during most of the year a series of shallows! in which the larva of ano- pheles abounds. It is urgently desirable that these terraces should be levelled out, and a smooth channel made for the stream, extending at least as high as the Pokfulam Road.
I shall be glad to examine and report on other particular localities, if desired by His Excellency to do so.
tion has been confirmed or amended by an ex- pert entomologist. To secure this, I have sent to the London School of Tropical Medicine fifty-four mounted specimens, consisting of fourteen different species of mosquitoes, two species being anopheles, eight species at least being culex, and the remaining four species probably belonging to other genera of the mosquito family, though one or two of them All may prove to be species of culex. the above have unspotted wings, excepting the anopheles and a single species of culex, of which I have obtained only a single specimen. This I believe to be culex mi- meticus, and it is manifestly very rare.
A good general rule, therefore, in Hongkong, in addition to the differences of the head appen- dages and the characteristic attitude when at rest that distinguish anopheles from culox, is that a mosquito with spotted wings is pro- bably one of the dangerous anopheles, and one whose wings are unspotted is a culez. I have privately submitted a few of the more prevalent types of both genera for his Excellency the Governor's inspection.
From my own observations, supplemented by those of Dr. T. M. Young, Civil Surgeon, R.A.M.C., with whom I have been working in co-operation since his arrival in the colony in August, and who has given his attention more especially to the question of breeding-grounds of the anopheles mosquito in the colony, I am of opinion that anopheles breeds, or may breed, in the more stagnant shallows, and in the rocky corners and crevices, of any or all of the ravines in the colony, and is practically confined to these during the greater part of the year. I wish it to be explicitly understood that my re- marks on the subject apply to the city of Vie- toria itself, and not to flat grounds in outlying districts where all the conditions are different. The usual habitat of the larvae of the anopheles mosquito is the natural watercourses, and their favourite locations little breaks in the rocky surface by the side of the stream, where the merest trickle from the stream itself prevents entire stagnation, and where there is no through-wash of water.*
So far as the city of Victoria is concerned, therefore, the configuration of the ground greatly simplifies the question of dealing with the snopheles pools. It reduces itself to the training of all the nullahs that are as yet un. trained. The clearing away of undergrowth is an important adjunct to more radical measures, inasmuch as it removes cover where mosquitoes may rest, but it is to be regarded as entirely subsidiary to the destruction of the breeding pools; and this can only be effected by the con- version of the uneven ravines into well-paved nullahs. In the latter no snopheles can broed, since in the running water there is no rosting place for the evolution of the egg and the deve lopment of the larva. This has fortunately already been done in the central part of the city.
The first untrained nullah as one proceeds westward is that to the west of the Nethersole Hospital, just above Ripon Terrace on Bonham Road. I have repeatedly satisfied myself by personal
of observation of the presence apopholes larvae in this ravine, and the marked prevalence of malarial fever in houses in this neighbourhood is sufficiently accounted for.
The extirpation of malaria in the western part of the city, which has in the past had such an evil repute as regards this disease, consists in the levelling or covering in of all the water- courses, beginning with the one I have named, and dealing with all between that and Kennedy Town. If this were done, malaria would hitherto avoided would probably ere long be largely disappear from the district, many sites made use of for the erection of European houses, and the fuller opening of this large area to building operations would be not unwelcome in the present congested state of the city.
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And here I would point out that the one water-course in the west that has been to some extent trained in the pre-mosquito. malaria-theory days has been trained that it is a perfect hotbed of malaria. I refer to the nullah passing down in front of the Public Mortuary. It has been trained in a series of dams and terraces, which while excellent for breaking the force of a
Vide Addendum.
Concurrently with my enquiry into the pre- valence of anopheles, I have been investigating the prevalence of the malaria parasite in the colony. Its connection with anopheles is now an accepted fact. The general mosquito-malaria theory has been proved to the hilt, and has recently been brilliantly demonstrated to the public by Manson's double experiment; but the connection of malaria with disturbance of soil, an important point in Hongkong, is by no means clear as yet. Grassi disposes of the subject by stating that it depends on the crea tion during digging operations of puddles of water in which anopheles breeds. This certain ly does not hold for Hongkong. The whole of the broken earth surface may show no single puddle, the sun drying the superficial layers as they are turned up; and yet it is a fact of ex- perience that in certain parts of the colony earth-cutting is invariably attended by an out- break of fever. On the other hand there is un- doubtedly some connection with the presence of meisture in the soil-in certain localities, e.g. arouud MacDonell Road, where earth-cutting may go on to an unlimited extent with impunity, I find that the soil is comparatively dry; while in others, e.g. the west point already referred to, where the slightest excavation inevitably pro- duces fever in the neighbourhood, I find that the soil is more or less water-logged. I propose to give attention to this question, which is one very seriously affecting this colony.
i
[December. 1; 1900. 1
means to be adopted for its oxtermination, my attention has been directed most forcibly to the enormous prevalence of mosquitoes of the genus As has been mentioned, I have culex. differentiated at least eight species of this genus. The culex mosquito does not, so far as is yet ascertained, act as a host to the malaria parasite; but it as well as anopheles is certainly the intermediate host of the minute parastic bloodworm, the Filaria Nocturna or Filaria Sanguinis Hominis, whose adult form lies in the lymph vessels, and is the cause of the great group of Elephantoid diseases. Elephantiasis is quite common among the Chin- ese in this region, though, for some reason not yet sufficiently explained, Europeans are as a rule exempt from it, an exemption, however, by no means complete; but most Europeans are affected by the immediate disagreeable effects of the bite of the mosquito, and few are aware that the daily supply of these vicious little insects is being produced in their own houses. “
I think public attention should be drawn to this fact. would like to write it in large capitals, that I HAVE FOUND THE LARVAE OF cULEX PROCESS OF DEVELOPMENT IN
IN
OR ABUNDANCE IN
ABOUT EVERY. HOUSE WITHOUT AN EXCEPTION IN WHICH I HAVE LOOKED FOR THEM. A few instances will illustrate the great variety, and also the common general character, of their breeding places :-at the Alice Memorial Hospital I found them in an old teapot on the roof-balcony; at the Tung Wah Hospital, in the ornamental flower-stands; at the gaol, in an empty pot in the coal store; at Kennedy Town Hospital, in the fire buckets; behind a house at the Peak, in a disused hand- basin; in another house at the peak, in a dish placed to catch the water-drippings from the ice-chest, &o. In all these cases they were in abundance, and were daily giving off large numbers of full-grown mosquitoes for the supply of their respective localities.
My chief field of observation as to the pre- valence of the malaria parasite in the colony has
The crusade against the mosquito should in- been the Tung Wah Hospital, where Dr. Chungclude the culex as well as the anopheles. Ano-
examining has at my request been recently microscopically the blood of all cases of fever, pheles must be dealt with by the Government and daily submitting specimens for my personal chiefly, though owners of property may pro- bably find it to their advantage to move private- examination at my visit of inspection.
ly in this matter as well; but eulex can be ex- terminated, or at least greatly diminished in numbers, by individual action alone. It may be impracticable to secure individual action of a sufficiently wide-spread character to make much impression on the sum total of the culex mosquitoes in South China, but every house- holder in Hongkong has it in his power by due attention to his verandahs, back yard, and coolie quarters to secure that in his own house at least there shall be fewer mosquitoes in the future than there have been in the past. Many are aware that what they have often seen in such receptacles as I have described are the larvae of mosquitoes; but few realize that these same wriggling creatures will a few days later rise from the surface of the water as adult insects, and will probably find their first meal of blood
larval stage. within the house that harboured them in the
There are three main types of malarial fever, associated with different and corresponding parasitic organisms, and all the three types of the parasite I have found prevalent in Hong. kong :-the benign tertian parasite, easily yield ing to the action of quinine; the quartan para site, readily brought under control by the same drug, but difficult to eradicate; and the malig. nant parasite, variously described as aestivo. autumnal by Italian observers, tropical by Koch, pernicious, &c., less amenable to quinine, more severe in the resulting symptoms, and more apt to produce a fatal result or prolonged ill-health.
Of 50 cases in which, up to 31st October, parasites were found, and their form and type recorded, 3 came from Kennedy Town, 18 from the west part of the city, 13 from the central parts of the city, 6 from the east part of the city, 2 from Happy Valley, and 8 from outlying villages.
The most common type of the parasite in the cases which I have examined has been the malig- nant parasite, with abundant crescentic forms; but I do not consider that this gives the true pro- portion of the prevalence of the different para- sites in the colony, since probably only the more serious cases of fever find their way into the hospital wards.
There has recently been a small epidemic of fever in the neighbourhood of the Naval Hos- pital and Morrison Hill Road. My first oppor: occurred on 27th October, when I was requested tunity of personal observation in reference to it to see the family of a European government officer whose four children had all suddenly be come ill with high fever. I took a microscope to the house, and found the benign tertian parasite in the fresh blood of three out of the four cases. All readily yielded to quinine, and by 1st November, they were back at school. I requested the father of the patients to catch for me some of the mosquitoes frequenting the house, and the first he submitted was a specimen of anopheles costalis.
While pursuing this investigation into the prevalence of mosquitoes in the colony and its dependencies chiefly with reference to the ques tion of the presence, of anopheles, and the
I intend to continue my investigations along the lines indicated above, and shall make further reports in due course.
Since much interest in the subject of the connection between malaris and the mosquito exists in the colony, a good deal regarding it having been reprinted in the public press; and since papers referring to it in other parts of the world have been placed by the Governinent be- fore the Sanitary Board; I would suggest that this preliminary report on the subject as it is affected by local conditions in Hongkong should be made public for general information, Governor may see fit; and I shall be glad if a through such channel as His Excellency the copy of it might also be transmitted to England
the Colonial Office. for the use of Dr. Manson, Medical Adviser to
ADDENDUM.
Since the foregoing was written, a fact of very great practical importance has been brought to my notice by Mr W. J. Tatcher. The anopheles occasionally departs from its usual habits, and may breed in artificial col- lections of water. With Mr. Tutcher I yes terday examined one of the Chinese flower- nurseries at West Point, that to the east of the house called "Nullah Bide" from its location, and found in many flower-pots ¦ con
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