M 118
LABOURERS OTHER THAN NEW ARRIVALS.
Date. Race. No. examined. Parasite rate per cent. Spleen rate per cent. Parasite rate for all races. June-July Cantonese 302 44.70 20.2 46% Shanghai 67 59 1.3 Indians 31 29 0.0 November Cantonese 299 26.42 3.34 26.42% Shanghai 180 13.33 1.11 Indians 21 9.52 0.0585. During the year anophelines caught in the lines were identified and dissected at the Malaria Bureau. The prevalent anophelines were A. minimus, A. jeyporiensis, A. maculatus and A. hyrcanus. All species were found to be natural carriers but the prevalence and infection rate varied according to the species and the season.
586. As little was known of the power of flight of the local anophelines it was deemed wise to commence anti-larval measures at the centre or lines site spreading out concentrically until such a distance had been reached as would be sufficient to prevent access to the lines from the breeding places under normal flight conditions.
587. Experience in Malaya had shown the margin of safety for that country to be half a mile and it was hoped that in Hong Kong this distance or less would prove sufficient. The index of success would be the absence of mosquitoes in the lines.
All privately owned land within a radius of half a mile from the lines was resumed by Government in order that there might be full control over this area.
588. Anti-malaria inspectors from the Malaria Bureau visited frequently for the purposes of collecting mosquitoes and their larvae. Specimens caught were conveyed to the Bureau for identification and dissection.
589. Tents each containing a human bait suitably protected were placed in different positions in an attempt to determine by the catches made the directions from which the anophelines invading the lines were coming.