MALAYSIAN PARASITES XII 
CERCARIAL DERMATITIS CAUSED BY A MEMBER OF THE “ ELVAE ” GROUP 
By 
A. A. SANDOSHAM 
Professor J. J. C. Buckley (1938), showed that the skin infection known as “ sawah itch ” 
among the rice cultivators in Malaya could be caused by the cercariae of Schistosoma spindale 
Montgomery, 1906. He collected Planorbis exustus and Limnaea sp. from the infected area. 
Cercariae were obtained only from the Planorbis , 8 out of 89 passing the typical Schistosome 
form. Using these cercariae he produced experimental dermatitis on himself and, by 
experimental infection of mice, established the identity of the cercariae. 
In 1948, the writer received a letter from Dr. Suleiman, Health Officer, Tampin, stating 
that there were complaints of unusually severe “ sawah itch ” in the Ayer-Luning District, 
Negri Sembilan. He was referred to Professor Buckley’s work and, in order that the 
experiment could be repeated, was requested to collect and forward snails of all types (especially 
those resembling Planorbis) from that area. 
About a hundred snails, later kindly identified by Dr. W. J. Rees of the British Museum 
as Lymnaea crosseana Mabille, were received. Of these 72 were alive and 19 extruded cercariae, 
1 3 of them extruding only a furcocercous variety. 
Description of Experiment 
These furcocercous cercariae were placed on the forearm of the writer in some water and a 
pricking sensation was evident in four minutes, the intensity reaching its maximum in twelve 
minutes. Half-an-hour after the commencement of the experiment, the water had not 
completely dried and it w T as wiped off. There was no obvious change on the skin at first but a 
mild itching sensation persisted for about four hours. About three hours after the 
commencement of the experiment, the skin was slightly raised and somewhat inflamed. The 
following day the inflammation had subsided and in a week’s time no difference could be seen 
from the normal skin. 
Description of Cercariae (fig. 1) 
Behaviour : — The furcocercous cercariae are phototactic and negatively geotactic, tending to collect 
near the surface towards the bright side of the room. They hang head downwards with the tail stem in 
line with the body but the furcae spread apart. They swim actively for the most part with the tail forwards. 
On a microscope slide they crawl about with the aid of suckers in a forward direction. The cercariae 
were dead or moribund in 24 hours. 
Morphology . — The body is narrow and elongated being about twice as broad as the tail except when 
extended. The tail stem is longer than the length of the body. The tips of the tail furcae end in narrow 
papilla-like projections and the tail furcae are shorter than the tail stem but more than half its length. A 
pharynx is absent but the posterior portion of the oral organ is muscular. A pair of pigmented 
“ compound ” eyespots are present slightly in front of the middle of the body. There are two suckers. 
The ventral sucker which is muscular and protrusible is situated iust in front of the commencement of the 
posterior third of the body. The surface of the body and tail is studded with numerous minute spines, 
these being more concentrated at the anterior end. The flame cell pattern could not be definitely 
established partly from lack of material and partly from the writer’s lack of familiarity with this difficult 
structure. However, a pair of flame cells was definitely made out in the tail stem close to the body. 
The excretory canal runs down the centre of the tail stem and the furci to the tip. 
Vital staining with neutral red showed up a mass of large glands in the posterior part of the body but 
the outline of the cells was indistinct and it was not definite if there were five or six pairs of glands. Heavy 
ducts were seen leading from the glandular area towards the anterior end. 
The following measurements based on seven specimens were taken from preserved material (measure- 
ments in mm .) ; this material was stained with lithium carmine and brilliant green as recommended by 
Gordon et al. (1934) but no further details could be observed in the penetration glands beyond the fact 
that the anterior glands took on the stain somewhat differently from the posterior pairs. 
MALAYA , No. 26. 1953 
