Vol. V. No. 108. 



THE AGR [CULTURAL NEWS. 



187 



THE PREVENTION OF YELLOW FEVER. 



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The following information in relation to the 

 prevention of yellow fever has recently been issued by 

 the Colonial Office : — 



Yellow fever can be absolutely .suppressed by the 

 application of simple, practicable, and non-costly methods. 



In order to carry them out the following facts must be 

 known : — 



L It has been proved that yellow fever can only be 

 transmitted by the bite of a particular mosquito known as 

 the ' Tiger ' or ' Brindled ilosquito ' {Stegomyia fasciata), 

 ■which must have previously bitten a person suffering from 

 yellow fever ; in no other way can it become infected. 

 Yellow fever is not caused by opening up the ground, 

 dredging, canal making, nor by contact with yellow fever 

 patients, their clothes or bedding. 



2. This mosquito is found in abundance in Me.xico, the 

 southernmost portions of the United States, Central and 

 South America, the West Indies, as well as in many other 

 places in tropical and sub-tropical countries. 



It is common in the sea-ports but extends into inland 

 towns following the trade routes. 



3. It is essentially a town dweller and is the common 

 ' Domestic ' or ' House Mosquito.' It is not known to be 

 a marsh or swamp dweller. 



4. It breeds in the clean water receptacles in the yards 

 of houses, and in consequence it is often known as the 

 'Cistern Mosquito.' The actively moving 'wrigglers' or 

 ' wiggle waggles ' which are found in great abundance in 

 cisterns, barrels, and kerosene tins, used for the storage of 

 •water, constitute the larval stage of the mosquito. 



5. It also breeds in old bottles, meat and condensed 

 milk tins, flower pots, conch shells, and discarded receptacles of 

 all kinds capable of holding water for a few days, and which 

 are commonly found in all badly kept yards and rubbish heaps. 

 It also breeds in rain water which may collect in canoes, 

 in the lily tubs, and it may even make its appeai-ance in the 

 ■water vessels in the rooms, if the water is allowed to remain 

 undisturbed in them for a few daj's. 



6. It is not usually found in gutters, pools, or wells, but 

 if debarred access to the common water receptacles it may 

 be driven to seek unusual breeding places. 



7. It must be remembered that if this mosquito is found 

 in a house its breeding place is usually close at hand. 



8. Because of the fact that the Stegomyia is a cistern 

 breeder, yellow fever may occur in the wealthier and more 

 sanitary parts of the town as well as in the poorer insanitary 

 districts. 



9. It is readily distinguished from other mosquitos by 

 its very characteristic appearance. It i^a ' Black and White 

 Mosquito.' There is a lyre-shaped pattern in ■«'hite on the 

 back of the thorax, transverse white Ijands on the abdomen, 

 white spots on the sides of the thorax, and the legs have 

 white bands, with the last hind tarsal joint also white. 



10. The mosquito deposits its eggs on the water in the 

 cistern. The eggs develop in from ten to twenty hours into 

 the active wriggling larvae. The larval or wiggle .stage lasts 

 six and a half to eight days, and is then followed by the pupa 

 stage ; from the pupa in two days' time or even less a complete 

 mosc[uito emerges and flies into the nearest house. 



The eggs are resistant and capable of preserving their 

 vitality although removed from water for some ten to ninety 

 days. They may therefore persist for a long period in an 

 empty damp barrel and develop into wigglers when the 

 barrel is filled. The larvae, however, quickly die if removed 



(1) 



(2) 



(3) 



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from water. The mosquitos may live for many -weeks in the 

 rooms, verandahs, and outhouses. 



11. Water is therefore essential to the existence of the 

 mosquito, and to prevent tlie breeding of the Stegomyia, it is 

 necessary- 



That all water receptacles be rigidly .screened. 

 That the material for screening be brass-wire 

 gauze, 18 meshes to the inch to prevent 

 ingress or egress of the mosquito, no chinks 

 being overlooked, or an overflow pipe left 

 unprotected. 

 That the brass gauze be fixed by wooden fillets 

 or copper nails to wood, no iron nails to be 

 used. 

 That each householder should set an example by 

 screening his o\\ n water cistern. 



(5) That all public WH'er cisterns should be screened, 

 the local authorities, state, municipal, or 

 ecclesiastic and others who control public 

 cisterns, setting the example. 



(6) That in the yards of the poorer people each 

 storage barrel be supplied with a spigot to 

 draw off the water, and that the top be 

 securely screened ; loose covers being of no use. 

 That as soon as possible all barrels be done 

 away with and replaced by properly screened 

 cisterns. 



(7) That odd receptacles such as tins, bottles, etc., 

 be never allowed to litter the yards, but be 

 gathered up and removed by the dust cart or 

 buried in the ground. 



(8) That ■n'ater should not be stored in kerosene tins. 



(9) That in an emergency, screening be done with 

 cheese cloth until the permanent brass-wire 

 screens are available, and at the same time 

 1 pint of kerosene oil be poured on the water 

 in the cisterns and barrels at least once every 

 week, pending the screening. Oiling must 

 not take the place of permanent screening. 

 It must be remembered that the oil is .soon 

 wa.shed away by heavy rains. 



Note. — Oil is used because it forms a film on the 

 .surface of the water and so prevents the 

 wiggle waggles from coming to the surface to 

 breathe ; in consequence they soon die. The 

 oil does not impart a taste to the water. 



(10) That merely emptying the water out of a barrel 

 or other receptacle which contains wrigglers 

 will not neccessarily get rid of them, as they 

 cling to the crevices and reappear when fresh 

 water is poured in. In the same way heavy 

 rains do not wash them out, as erroneously 

 supposed. Careful screening is the only 

 effective remedy. 



(11) That as the Stegomyia may seek refuge for 

 breeding purposes in the shallow street drains 

 and wells in the town, these must on no 

 account be overlooked. The shallow street 

 drains and pools sliould either be filled in or 

 kept well treated with crude petroleum oils. 

 Wells can with difficulty be properly protected 

 and should be filled in or constantly oiled. 

 Lily tubs and ornamental ponds should be 

 stocked with fish. 



[To be concluded.) 



