1. The 7,000 British and Australian prisoners of war who formed “F” force, left Changi camp on Singapore Island in April, 1943, and 3,122 returned in December, 1943. They had spent the intervening 8 months in the hilly jungle country of Siam, about 200 miles north-west of Bangkok near the Three Pagodas pass on the Siam-Burma border, constructing a section of a new railway to link Bangkok and Moulmein. 2. Few had had malaria before leaving Changi. Those who returned had a malaria parasite rate of 25·7 per cent. (801/3,122), and a malaria attack rate during 7 weeks of January to February, 1944, of 18·8 per thousand men per day. 3. Field's rapid stain proved of great value. Its independence of alcohol and the pH of the water available, and its extreme economy in use, made it ideal for our purpose. 4. Plasmodium vivax was at all times the commonest species of parasite; in the later months it completely outnumbered P. falciparum, and the picture presented was that of chronic relapsing vivax malaria in a debilitated population. 5. Quinine, when available in sufficient quantity, effectively cured attacks of malaria, but recurrences in a few weeks were commonplace. 6. Malaria was recorded as a cause in 11 per cent. of all deaths (338/3,087), but there is reason to think that it was contributory to many more. 7. Anopheles maculatus and A. minimus were considered to be the principal vectors, though A. leucosphyrus may also have played some part in transmission; these judgements, however, are based on larval surveys only, and lack the definite proof afforded by trapping and dissection of adult mosquitoes. 8. Larvae of Anopheles aitkeni and A. barbumbrosus were found. These species do not appear to have been reported from Siam before. 9. We confirm Anigstein's opinion of the malarious nature of hilly regions in Siam, but differ from him by suggesting that the season of greatest transmission in this particular region is more likely to be the wet season than the dry. He thought that agriculture in the hilly regions, which involved irrigation, usually made the malaria worse. This is in line with our findings that the two camps situated near abandoned rice fields were the most malarious. © 1949 Oxford University Press.
Wilson, T. (1949). Malaria among prisoners of war in siam (“f” force). Transactions of the Royal Society of Tropical Medicine and Hygiene, 43(3), 257–272. https://doi.org/10.1016/0035-9203(49)90003-6