War Surgery and Medicine
Valuable information was supplied by Lieutenant-Colonel Sayers, who had practised at Munda and Vella Lavella from 1927 to 1934, and this was published in 1943 in a booklet, Malaria in the South Pacific. The Solomon Islands could be classed as a hyperendemic area. Generally speaking spleen rates varied from 51 to 94 per cent on different islands. The only group with a relatively low splenic index was the Treasury Islands. Rates for the three islands on page 532 which the New Zealand Division served were: Guadalcanal 77.7, Vella Lavella 67, and Treasury (Mono Island) 14.3.
Studies on the native population had shown that the malaria incidence started to rise during January, reached its peak in June, and fell rapidly during July. The period from August to January was the ‘healthy’ season from the malaria point of view. The big increase in the number of cases during the first half of the year was due mainly to the large number of Falciparum cases occurring at that time.
The malaria season could be correlated with the wet season although there was a lag of one to two months—the wet season was roughly from December to April, and the malaria season from February to June. Annual rainfall in the Islands varied from 75 to 175 inches. In most cases the distinction between the wet and the dry seasons was well marked, but in certain situations on the larger islands there was not a great deal of variation from month to month. The prevailing winds during the wet season were north-west (November-April), and in the dry season (May–October) south-east, the so-called south-east trade wind. The wet north-west season was also the warmer season. There were no big diurnal variations in temperature, which ranged from a maximum of about 95 degrees F. to a minimum of about 73 degrees F.
Topography had an important bearing on the malaria problem. Practically all the islands, except the atolls and a few volcanic islands, consisted of an elevated centre of igneous or sedimentary rock with terraces of old coral platforms fringing the base. These coral terraces on the coast were frequently the site of coconut plantations. On most islands, with the notable exception of Guadalcanal, there was no great development of alluvial plains. The lowlands, with the exception of coconut plantations, native gardens, and (on Guadalcanal) natural grassland, were under heavy jungle. As a rule the whole of the interior was under heavy jungle.
In general the soils, when undisturbed by working or heavy traffic, were fairly free-draining, and temporary pools did not remain many days unless there was continuous rain. The coastal strips of coral sand were particularly well drained. On the smaller islands large streams were not numerous, but there were frequent springs and seepages and short spring-fed streams. On low atolls such as Nissan streams were absent, though there could be occasional fresh-water ponds.
Under undisturbed conditions on most of the small islands and on many areas of the larger ones, malaria was surprisingly easy page 533 to control with relatively small resources of labour and materials. A small number of permanent breeding places near native villages was often sufficient to maintain a high splenic rate. Splenic indices gave no indication of the magnitude of the control problem, which was largely determined by topographical factors. (When military occupation takes place the position alters since the forces largely create their own problem.)
The vector was known to be Anopheles Farauti. There was some obscurity as to which variety was most prevalent. Little was known about the characteristic habits of the species and little had been attempted in the way of systematic malaria control.
The types of parasite found in the New Georgia-Vella Lavella area were: P. falciparum, 43.9 per cent; P. vivax, 32 per cent; P. malariae, 18.3 per cent; and species unidentified, 5.8 per cent. These figures related to the general population, including women and many children.
CONTROL OF MALARIA
Preparations for the control of malaria in our troops can be described under the following headings:
Organisation and training of Malaria Control Unit.
Training of medical personnel in diagnosis and treatment of malaria.
Training of combat officers and other ranks in anti-malaria measures.