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malaria proving of a particularly malignant type. It was decided to 

 undertake drainage of the marshes before the summer of 1917. Sup- 

 plies of quinine, netting, oil, paraffin and implements were obtained, 

 but it was soon evident that personal prophylaxis, such as the use of 

 nets, w^as impossible at times, such as during night operations or 

 enemy bombing raids. 



At Thasos, the aerodrome was built between a thickly overgrown 

 marsh, that formed an ideal breeding-place for Anophelines, and a 

 belt of olive trees, among which the tents were pitched. The drainage 

 of this marsh presented considerable difficulty and a permanent 

 channel to the sea was constructed of baulks of timber supported by 

 stones and fitted with a sluice gate. This caused a considerable fall 

 in the marsh water-level and was reinforced when necessary. Olive 

 trees, if near a marsh, have a definite inffiience on malaria, 

 the flowers attracting mosquitos and affording suitable food for 

 them. The marsh was drained near the aerodrome and the area 

 near the camp cleared by burning and cutting away bushes. The 

 channels were sprayed once a week, after clearing the surface of weeds, 

 with heavy Burma oil mixed in equal parts with low-grade paraffin, 

 half a pint of the mixture being used per hundred square feet of surface. 

 Subsoil drainage proved to be the most important of all anti-malarial 

 work and rapidly reclaimed large areas of marsh. The lagoons near 

 the beach were kept open to the sea and made tidal. They soon became 

 stocked with small fish and remained free from larvae. Old, disused 

 wells were located and filled in. Garden ditches were cleaned out and 

 linked up to the main system. 



The species found in Thasos were Anopheles maculipetmis, which, 

 however, lacked the distinctive spotted markings on the wings. 

 A. bifurcatus was present, but in smaller numbers. A large plan of 

 the extensive drainage scheme was made to facilitate routine inspection, 

 and the system was constantly repaired and cleaned. Lectures on 

 personal prophylaxis were given to the men, who were well supplied 

 with nets, cap veils, gloves, etc. Quinine was administered daily in 

 alternate doses of 5 gr. and 10 gr. Mosquito-proof huts were used 

 after sunset. 



The first mosquitos in 1917 appeared in June and no cases of malaria 

 occurred until 17th July ; after this date the aerodrome was heavily 

 bombed and the men were obliged to spend three nights in mosquito- 

 infested dug-outs or among the trees, with the result that there was a 

 sharp outbreak of malaria. The incubation period had been con- 

 siderably delayed by quinine and all cases were of a modified type, 

 mostly tertian. The patients rapidly recovered and no more cases 

 occurred until after the middle of October. 



By April 1918, the marsh was completely dry and could be cleared 

 by burning, and large areas of old swamp land were reclaimed for 

 maize crops by the natives. The results were most gratifying. No 

 malaria occurred among the men left as a maintenance party, the 

 main body of men having been evacuated. 



It was observed at Thasos that, given a belt of olive trees and a 

 steady prevailing night wind, the Anophelines may travel for 1| miles. 

 The author considers that malaria could be eradicated in Thasos 

 in two years of active Government control, unhampered by questions 

 of economy, and such measures would greatly increase the value of 

 the island. 



