Infective larvae of Brugia malayi subperiodic obtained by dissection of infected Aedes togoi were injected subcutaneously into the scrotal region of Mastomys natalensis. From altogether 58 infected male M. natalensis 81% showed consistently or intermittently detectable microfilaraemia, whereas in 19% of the animals no microfilaraemia could be detected at any stage. The mean prepatent period was 136 days; the microfilarial density varied from 1 to 535 per 20 c. mm blood. In those animlas with consistently detectable and in general higher microfilaraemia an average of 13.1 live adult worms were found, against an average of 6.4 adult worms in animals with intermittent detectable and in general lower microfilaraemia. An average of 1.5 worms was found in animals which at no stage showed detectable microfilaraemia. A correlation between worm burden and prepatent period could be observed in the individual groups. From the total of 520 live adult worms recovered at necropsy, 37% were found in the lungs, 29% in the parenchyma of the testes and 34% in the lymphatic system. 47% of live fertile female worms were found in the lymphatic system, whereas the majority, i.e; 52% of infertile female worms were detected in the lungs. In addition, 380 encapsulated dead worms were found, most of them (98%) in the lymphatic system. 61% of a total of 900 live and dead worms were found in the region of the lymphatic system.
Angiostrongylus cantonensis Chen, was recovered from a field rat, Rattus tiomanicus from the East Coast of Peninsular Malaysia. The parasite constitutes the first reported record occurring in this country. Morphological character of the parasite are compared with the original description of A. cantonensis by Chen (1935), A. cantonensis from Formosa and A. malaysiensis from Malaysia.
Neodiplostomum (Conodiplostomum) Brachylaima, Ectosiphonus and Euparadistomum are reported for the first time from small mammals in Malaysia. New host and locality records are given for Echinostoma, Achillurbainia, Beaveria, Odeningotrema, Leipertrema, Athesmia, Skrjabinus and Zonorchis. Possible-life-cycles of the parasites are discussed in relation to the ecology and feeding habits of the hosts.
A light and electron microscopic study of Sarcocystis orientalis sp. n. was made. The life cycle of this parasite is in two hosts. Gametogony is in the intestinal epithelial cells of a predator, Python reticulatus. Isospora-like oocysts developed. Sporocysts average 9.1 by 7.7 mum. Rats (Rattus norvegicus) were infected with sporocysts and asexual stages developed. Ten days after infection large zoites (average 7.85 by 2.48 mum) were observed free in peripheral blood and within white blood cells. Small schizonts producing merozoites 2-3 mum long were seen in lung tissue. Tissue cysts developed in skeletal muscle and produced numerous cystozoites (average 5.53 by 1.38 mum). Fine structure was similar to previously described Sarcocystis spp.
Breinlia booliati exhibited nocturnal subperiodicity in its natural host, Rattus sabanus in contrast to experimentally infected laboratory-reared albine rats which showed irregular fluctuations of microfilariae throughout the 24 hour cycle. All the infected albino rats showed a prepatent period between 11-14 weeks postinoculation. Three patterns of microfilaraemia were discerned during the course of infection 38/49 rats displayed a single peak, 4/49 displayed 2 peaks about 12-15 weeks apart and 7/49 showed a sustained high plateau-like pattern of microfilaraemia. Cortisone had no effect on microfilarial levels when administered to rats near postpatency and some at postpatency.
All subspecies of black rats (Rattus rattus) used in the present study are characterized by having large and clear C-bands at the centromeric region. The appearance of the bands, however, is different in the subspecies. Chromosome pair No. 1 in Asian type black rats (2n=42), which are characterized by an acrocentric and subtelocentric polymorphism, showed C-band polymorphism. In Phillipine rats (R. rattus mindanensis) the pair was subtelocentric with C-bands, but in Malayan black rats (R. rattus diardii) it was usually acrocentric with C-bands. In Hong-Kong (R. rattus flavipectus) and Japanese black rats (R. rattus tanezumi) it was polymorphic with respect to the presence of acrocentrics with C-bands or subtelocentrics without C-bands. The other chromosomes pairs showed clear C-bands, but in Hong-Kong black rats the pairs No. 2 and 5 were polymorphic with and without C-bands. In Japanese black rats, 6 chromosome pairs (No. 3, 4, 7, 9, 11 and 13) were polymorphic in regard to presence and absence of C-bands, but the other 5 chromosome pairs (No. 2, 5, 6, 8 and 10) showed always absence of C-bands. Only pair No. 12 usually showed C-bands. C-bands in small metacentric pairs (No. 14 to 20) in Asian type black rats generally large in size, but those in the Oceanian (2n=38) and Ceylon type black rats (2n=40) were small. In the hybrids between Asian and Oceanian type rats, heteromorphic C-bands, one large and the other small, were observed. Based on the consideration of karyotype evolution in the black rats, the C-band is suggested to have a tendency toward the diminution as far as the related species are concerned.
The development of Breinlia booliati is described in its natural host, Rattus sabanus and in an inbred strain of laboratory albino rat. The growth of the parasite is similar in both the rat hosts. The third moult occurs between six-eight days and the final moult between 24-28 days. Larvae were recovered initially from the skin and carcass. After five weeks, developing stages were seen only in the thoracic and abdominal cavities, the site of development of the adult worms. Worms became sexually mature by 11-12 weeks and there was considerable growth in length of the female worms after this stage.
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.
Neodiplostomum (Conodiplostomum) ramachandrani sp. n. is described from Rattus muelleri in Kepong, Selangor, Malaysia. It is characterised by having symmetrical dumbell-shaped testes, and vitellaria as a single ventral band in the hindbody. The taxonomic relations of Neodiplostomum, Conodiplostomum and Fibricola are discussed and possible significance of the fluke as an ecological indicator noted.
A high prevalence of murine typhus was found in the human and rodent populations of Senaling, West Malaysia. In addition to 2 index cases which prompted the investigation, 45% of the humans and 35% of the rodents had IFA titers of 1/50 or greater. Serological studies provided evidence of recent infections in 3 human subjects. In a control group of Malaysian soldiers IFA titers of 1/50 or greater were found in only 13 (5%) of 265 sera tested.
Albino Wistar rats of both sexes were given a conditioned taste aversion training (CTA). Saccharin was used as the conditional stimulus (CS) and apomorphine-induced illness as the unconditional stimulus (US) on day 4. Amnestic treatment with electroconvulsive shock (ECS) or nitrogen anoxia were given to the rats at various points within the 180-min long CS-US interval as well as after the US. They were reexposed to the CS on days 5 and 6 in order to evaluate CTA and its extinction respectively. Apomorphine injection alone produced significant CTA as long as the CS-US interval was less than 120 min but not beyond it. Saline injections, with or without amnestic treatments, produced only an adaptation to and preference for saccharin. ECS could prevent CTA when delivered within 85 min before or 110 min after the US. Anoxia was effective at a much shorter range of time than ECS. The results are discussed in the perspectives of neophobia, saccharin aversion, amnestic agents and the character as well as gradients of amnesia produced.
Clinacanthus nutans Burm, a herb reputed in Thailand and Malaysia to be "snakebite antidote" has been tested in vitro and in vivo for antivenin activity. The aqueous extract of C. nutans leaves has been found to have no effect on the inhibition of neuromuscular transmission produced by purified Naja naja siamensis neurotoxin in isolated rat phrenic-nerve diaphragm preparations. The extract of C. nutans, when given orally or intraperitoneally, are ineffective in prolonging the survival time of experimental mice receiving lethal doses of N.n. siamensis crude venom. Oral administrations of the herb extracts pretreated with alpha-amylase or beta-amylase also fail to protect the animal. It is concluded that the extract of C. nutans can not antagonize the action of cobra venom.
Numbers of L. (L.) deliense larvae were determined in adjacent habitats over a 16 month period. Both R. argentiventer and R. tiomanicus were highly efficient hosts for L. (L.) deliense. R. argentiventer was host to significantly greater numbers of chiggers per rat than was R. tiomanicus. The 2 habitats were similar in numbers of chiggers collected. No consistent correlation was apparent between numbers of chiggers and any single weather factor, but the chigger population seemed to be adversely affected by a 2 month period during which total evaporation greatly exceeded total rainfall. Direct fluorescent antibody examination of tissues from unfed L. (L.) deliense showed that 2 of 420 larvae (0.5%) contained organisms morphologically resembling R. tsutsugamushi. Considering the vector load and numbers of chiggers being returned to the ground by a given host, a rate of 0.5% appeared adequate to account for the prevalence rate of R. tsutsugamushi observed in the 2 host species.
The ultrastructure of Sarcocystis sp. from the Malaysian house rat, Rattus rattus diardii, was studied with the electron microscope. The thin, uniformly-dense primary cyst wall had a row of vesicular invaginations which were also seen along the wall of the villi-like projections or cytophaneres. Within the villi were spherical bodies and hollow, curled structures. The ground substance beneath the primary cyst wall extended into the cyst as thin septa or trabeculae separating the tightly-packed zoites into compartments. Merozoites had a double-layered membrane, a conoid, 2 conoidal rings, 22 subpellicular microtubules, 6 rhoptries, 80-100 micronemes, scattered lipid droplets, and sac-like mitochrondrion, beside which was a Golgi apparatus. A micropore was occasionally seen at the anterior third of the zoite whereas the nucleus occupied the posterior third. Metrocytes were few in number and peripheral in location.