Susceptibility to DDT, malathion, fenitrothion and dieldrin of three flea species in the boyolali plague endemic area, Central Java, Indonesia.

Insecticide susceptibility tests with 4% DDT, 0.5% and 5.0% malathion, 1% fenitrothion, and 0.2% dieldrin impregnated papers were carried out with fleas spp. from the Boyolali plague zone. The field flea (Stivalius cognatus) which was highly susceptible to malathion before, has now been found to be resistant to the insecticide, but was found susceptible to the other three insecticides. The oriental rat flea (X. cheopis) which found previously highly resistant to DDT, was now found to be less resistant, and susceptible to other insecticides tested. From preliminary tests with DDT to another field flea (Neopsylla sondiacus), it was found to be susceptible to the insecticide.

A study of small mammals in the Ciloto field station area, West Java, Indonesia, with special reference to vectors of plague and scrub typhus.

From June 1977 to June 1978 a study of smal mammals was carried out in the Ciloto field station area, West Java, Indonesia by the WHO Vector Biology and Control Research Unit-II. The objectives of the investigations were to determine the diversity and density of rodent species, to find potential plague and scrub typhus vectors and to study their host-parasite relationships. In the 13 month period a total of 6 species of murids were identified; two species of campestral rats (R. tiomanicus and R. argentiventer), one species of peri-domestic (R. exulans), one species of domestic (R.r. diardii), and two species of forest rats (R. bartelsii and R. bukit). In addition, three species of insectivores (Suncus murinus, Hylomys suillus and Crocidura monticola), and one species of carnivore were found. Of the three habitats studies (mixed, ricefield and lalang), 10 species of small mammals were found in the mixed while four species of commensal murids were found in both the ricefield and the lalang. Of the four commensal murid species R. exulans had the highest density. R. tiomanicus was common but not abundant, and least common was R. argentiventer. R.r. diardii was occasionally found in the field. The mean litter size of gravid R. tiomanicus was 7.1, R. exulans 4.3, R. argentiventer 7.5 and R.r. diardii 9. Male R. tiomanicus, R. argentiventer and R.r. diardii with spermatozoa present in animals over 55 gm. Animals of less than 50 gm had no sperm. In R. exulans spermatozoa were present in specimens weighing 24-66 gm. No sperm were detected in those below 20 gm. The flea index of Xenopsylla cheopis and Stivalius cognatus as determined for R. tiomanicus was 0.3 and 2.3;l for R.r. diardii 2.2 and 1.7; for R. exulans 0.3 and 0.5; and for R. argentiventer 0.4 and 1.7 respectively. S. cognatus had a significantly higher density than X. cheopis among the campestral and peridomestic rats, but the density of X. cheopis was significantly in the domestic rat. Overall infestation rates were equally high in both mixed and lalang habitats, but low in the ricefield. Flea indices were highest in the mixed habitat, lower in lalang, and lowest in ricefield. The putative vector of scrub typhus (Leptotrombidium (L.) deliense) was quite prevalent on campestral rats, less so on domestic ones and least on peridomestic. Overall infestation rates were equally high in both mixed and lalang habitats and low in the ricefield. Chiggers load per animal was significantly higher in the mixed habitat, lower in lalang and lowest in the ricefield.

New hosts of Breinlia booliati with observations on its distribution in Southeast Asia.

Breinlia booliati Singh & Ho, 1973 first described from Peninsular Malaysia has been shown to infect a large range of murids ranging in distribution from southern Thailand, Peninsular Malaysia, Sarawak to Ciloto, Indonesia. Probably further work will reveal a greater host range as well as its geographical distribution. The vectors involved in its transmission need to be elucidated.

Capillaria hepatica infection of wild rodents in Peninsular Malaysia.

Capillaria hepatica infection in wild rodents collected from the States of Kelantan, Selangor and Johore in Peninsular Malaysia since 1973 is reported. A total of 1,258 rodents consisting of 20 species of house, field and forest rats, and 7 species of squirrels were examined for the parasite and 17 species consisting of 111 murids and 1 flying squirrel were found infected. The house rat, Rattus norvegicus had the highest prevalence rate, followed by 3 species of field rats, R. tiomanicus, R. argentiventer and Bandicota indica. The prevalence of infection was low among forest rats with the exception of Lenothrix canus. Only 1 flying squirrel, Hylopetes spadiceus was found with the parasite. The prevalence of infection in relation to the host behaviour and habitats was discussed. C. hepatica appears to be widespread throughout Malaysia with a wide range of hosts among rodent species. Some new host records are presented herein.

Angiostrongylus malaysiensis from Tuaran, Sabah, with reference to the distribution of the parasite in Malaysia.

A survey of Angiostrongylus malaysiensis among wild rodent and molluscan hosts was made in the Tuaran Central Agricultural Research Station and within the vicinity of Tuaran, Sabah. Three of 19 Rattus rattus diardii, one of 2 R. exulans and one R. argentiventer were found naturally infected with the parasite. In this survey 56 of 382 molluscs comprising of Pila scutata, Achatina fulica and two species of land slugs, Laevicaulis alte and Microparmarion malayanus, were found naturally infected with the parasite. Samples of larvae from each of these molluscs were experimentally transferred to laboratory albino rats and adult worms consistent with A. malaysiensis were recovered. Comparison of the rat hosts and the molluscan intermediate hosts of the parasite in Peninsular Malaysia, Sarawak and Sabah was made, and the finding of A. malaysiensis in Tuaran is the first report of the parasite from Sabah. The distribution of the parasite throughout Malaysia is discussed. Observation on the human consumption of the freshwater snail, P. scutata, was made. Although the infection rate of this snail is low compared with other molluscan hosts examined. The importance of this mollusc as a potential source of human infection should not be overlooked. Hospital records for 1974 and 1975 were examined and clinical human angiostrongyliasis was rarely recorded in Sabah.

Distribution and ecological consideration of Breinlia booliati infecting wild rodents in Malaysia.

Seven of the 18 species of lowland forest terrestrial and semi-arboreal murids were found naturally infected with Breinlia booliati. Of these, two species, Rattus sabanus and R. cremoriventer, were found to be the most preferred hosts. None of the murids from the highland, field or human-inhabited areas was infected. This could have been due more to the greater scarcity of the vectors in these habitats than to the susceptibility of the hosts. The absence of this parasite in the squirrels examined may be attributed either to host specificity or to the normal activity cycles or vertical stratification of the vectors, separating them in space and/or time from the squirrels. The pattern of dispersion of the parasite is influenced by the wide distribution of suitable hosts, and the hypothesis that the parasite is of forest origin is discussed.