Rodents, particularly those belonging to the family Muridae, form the largest group of mammals in Malaysia. They are also a group that has been well studied because of their medical and economic importance. Yet, comparatively little is known, in Malaysia, about the helminths that are associated with them; far less the types of terrain in which these are prevalent. An attempt is now made to survey the nematodes parasitic in these rodents, with a view to assessing the potential risk from those that are harmful to man and domestic animals, and to studying those that are harmless, but nevertheless form an enlightening contribution to the knowledge of Malaysian parasitic fauna.

1. The susceptibility of two strains of rats, namely London-hooded and Wistar, to infection with S. mansoni has been investigated

2. Although equal numbers of cercariae penetrated the skin in both strains, recovery of worms was always higher from the London-hooded strain irrespective of the dosage level.

3. In both strains there was a significant relationship between body weight at time of infection and number of worms recovered. The correlation was a negative one, indicating that lighter (younger) rats were more susceptible than heavier (older) rats.

4. A rapid rate of elimination of infection was demonstrated in London-hooded rats between the 4th and 8th week after infection.

1. The influence of diets having different protein values on the schistosomicidal effect of Ambilhar has been investigated in mice.

2. Mice placed on these diets throughout the period of infection and then treated, reached differently. Low protein diets produced fewer and smaller worms which were more susceptible to the drug.

3. Mice maintained on an adequate diet were shifted to diets of varying protein values a few days before treatment. In these, drug treatment was more satisfactory in animals fed the high protein regimen.

4. Female worms were more affected by drug treatment than the males.

1. Infective larvae of S. lupi were collected in Madras from scarabaeid beetles, (the usual intermediate host), from garden lizards and shrews.

2. The structure and relative sizes of the larvae in the 3 kinds of hosts are compared.

3. Infective larvae were given orally to 30 dogs which were autopsied at intervals and the developing worms were recovered. Their growth was measured and some observations were made on their development during the prepatent period which was found to be 121 and 124 days.

Third stage infective juveniles of the genera Oesophagostomum and Ostertagia were found clinging to the abdomens of species of psychodid flies that breed in faeces. It is suggested that these dipterans may be able to carry parasitic nematode larvae from farm to farm.

0·15% of Oesophagostomum larvae fed to laboratory rats became encapsulated in the intestinal mucosa. The juvenile nematodes were able to continue their development when the infected rat tissue was eaten by pigs.

1. 5250 specimens of the common periwinkle, Littorina littorea (L.), from Scalby Rocks on the North Yorkshire coast were examined from October 1966 to November 1967 and data obtained on the size, sex and reproductive condition of the periwinkles and their infections with four species of Digenea, namely Cryptocotyle lingua (Creplin, 1825), Renicola roscovita (Stunkard, 1932), Himasthla leptosoma (Creplin, 1829) and Cercaria lebouri Stunkard, 1932.

2. The normal breeding cycle of uninfected L. littorea and the breeding cycles found in periwinkles infected with larval Digenea are described and discussed. Initial infection takes place mainly when periwinkles are spent after their first breeding season and though later damage to the gonad may prevent reproduction, the breeding potential of the periwinkle population at Scalby Rocks is unlikely to be affected seriously. There was no evidence of sex reversal in uninfected or infected L. littorea and the normal sex ratio is 1:1. The phenomenon of gigantism as a result of digenean infection is discussed with respect to L. littorea.

The helminth fauna of the chromosomal forms of Spalax ehrenbergi occurring in Israel was studied. In the examination of 153 hosts, five species of adult helminth and one larval nematode were recovered, namely: Heligmonella sp.; Trichuris muris (Schrank, 1788); Ganguleterakis spalaxi Kozlov and Yangolenko, 1962/63; Gongylonema longispiculum Schultz, 1927 and Paranoplocephala sp.

No correlation could be observed between the chromosomal forms and the helminth fauna.

Heligmonella sp. the most prevalent, was recovered from all chromosomal forms, other species occurred in two or three forms only.

A correlation could be established between climatic conditions and the distribution of the helminths. Heligmonella sp. was found in mole-rats from all climatic regions whereas the other helminths occurred only in those from northern and central areas.

The geographic and bionomic aspects of this distribution are discussed.

Twenty-three (9%) of 255 domesticated dogs surveyed in Lahore, West Pakistan, were blood positive for microfilariae. Twenty-one (8·2%) had either pure or mixed infections with Acanthocheilonema dracunculoides. Dirofilaria repens microfilariae were present in 4 dogs and one had Dirofilaria immitis microfilariae. A single adult A. dracunculoides was found from the hind leg of an autopsied dog with A. dracunculoides microfilariae. Microfilariae had a diurnal periodicity in this animal. There is only one previous documented report of A. dracunculoides adult worms from a dog in the Indian subcontinent, but it is possible that microfilariae earlier described from India under other names may also have represented this species.

The resistance to infection by Ostertagia spp. of three groups of lactating ewes was compared with an unbred control group. Group 1 was fed a full diet of hay and a concentrate ration ad lib. Groups 2 and 3 were fed the same quantitatively inadequate diet and in addition group 3 received daily injections of thyroxine sodium. All the animals were infected regularly with Ostertagia larvae and killed 6 weeks after lambing.

While the unbred sheep were highly resistant, all three groups of lactating ewes carried significant numbers of worms. Group 2 and 3 had significantly more than group 1, the additional worms being present as adults. The effect of hyperthyroidism in group 3 was not significant.

It is concluded that the immuno-suppressant effect of lactation is probably not due to protein depletion although the latter may be an important secondary factor.

1. With the aid of field growth curves, age-prevalence curves can be derived from field collections of snails, using cercarial shedding as proof of infection by schistosomes.

2. Such curves were obtained from eight collections of field snails: one sample each of Bulinus (Physopsis) nasutus productus and Biomphalaria pfeifferi, intermediate hosts respectively of Schistosoma haematobium and S. mansoni in Tanzania, and six samples of Biomphalaria glabrata, intermediate host of S. mansoni on St. Lucia, West Indies.

3. Catalytic curves were fitted to the data and in each case the two-stage curve gave the most satisfactory fit.

4. This curve is the resultant of two opposing forces: one force being the rate of infection and the other the rate of loss of infection in a snail population.

5. The rate of infection may be defined as the number of successful snail-miracidium contacts per 1,000 snails per week, while the rate of loss of infection is taken to represent the number of deaths per 1,000 infected snails per week.

6. The underlying assumptions of this form of analysis are discussed and, in view of the independent verification of some of the calculated rates, the values are considered realistic.

7. Besides providing quantitative data for inclusion in mathematical models of schistosome transmission, the technique offers an additional means of assessing the efficacy of certain methods of controlling transmission.

1. A distortion of the shell aperture of Biomphalaria glabrata infected with Schistosoma mansoni reported in earlier work was found to be due to a reversal from ventral to dorsal of the deflection found in uninfected snails.

2. The most sensitive way of measuring this distortion was to record the height of the dorsal deflection. The difference in this figure from uninfected and infected snails of the same diameter is termed the relative distortion.

3. A longitudinal study showed that the relative distortion first appeared at about the time when cercarial shedding started, and that it increased in size linearly as the infection progressed.

4. Temperatures between 20 and 30°C. controlled the length of the prepatent period and thus the first appearance of the relative distortion, but they did not significantly alter its subsequent rate of development.

5. Histological changes were observed in the mantle collar in the region where the relative distortion was most pronounced.

6. Possible mechanisms causing the development of the distortion are discussed.

7. Relative distortions were observed in some naturally infected field snails and the laboratory results were used to estimate how long these snails had been shedding cercariae.

8. Naturally infected St. Lucian snails appeared to have shed cercariae for an average of less than three weeks in the field.

9. A survival curve was drawn up for one collection of field snails, based on the frequency among them of relative distortions of different sizes. Another curve was obtained from an independent technique. The similarity of the two curves gives confidence in both methods.

10. The findings in St. Lucia are discussed in relation to similar studies elsewhere in the world.

The difference in the final shape of the cyst of H. rostochiensis and H. schachtii is shown to be due to patterns of growth during cyst development. The greatest change of form takes place during the first 6 days for H. rostochiensis and the first 12 days for H. schachtii. The principal difference between the cyst shape in the two species is due to the greater increase in length in relation to breadth of the growing H. schachtii cyst. Premature tanning, due to environmental factors, is shown to affect final cyst form.

An attempt was made to demonstrate passive transfer of immunity using neonatal mice born to mothers resistant to schistosome infection. No immunity was demonstrated in the baby mice, suggesting that the classes of antibody which are active in this immune system are not transferrable neonatally.

An interesting incidental finding was the apparent enhanced resistance of lactating mice compared to normal females or males and this was confirmed in another experiment. There was no significant difference between the susceptibility of normal females and male mice. More male worms were recovered from male mice than from virgin female mice.

Preliminary electron microscope observations have shown that in the miracidium of Schistosoma mattheei the surface of the apical epidermal plate consists of branching and anastomosing microvilli. It is suggested that this arboreal arrangement serves to attach the miracidium to the body surface of snail hosts during attempts to penetrate; the apical papilla can therefore be regarded as an attachment organ, functionally analogous to the suckers of the adult schistosome. It is also suggested that the degree of ‘fit’ between the attachment organ and the snail body surface may be an important factor determining the success of attempts by the miracidium to penetrate.

Electron microscopy has also shown that the so-called penetration and apical glands are single flask-shaped cells. No endoplasmic reticulum and very few ribosomes were seen in these cells and it is therefore suggested that, in the mature (free-swimming) miracidium, the “glands” are not functional as such; they are simply sacs full of fluid. If they contain histolytic substances they must either have been synthesized at an earlier stage in the life history of the organism or they are synthesized elsewhere and passed into the “glands”.

Histochemical attempts to identify leucine aminopeptidase and mucin in the contents of the “glands” of S. mansoni miracidia were unsuccessful. It is concluded that these substances probably do not play any role in the penetration into or attachment on snail intermediate hosts by S. mansoni miracidia.

Electron-microscopical, histological and histochemical observations were carried out on the body wall of the daughter sporocyst stage of Schistosoma mattheei and S. bovis. Electron microscopy revealed that the body wall consists of a continuous outer layer of cytoplasm, collagen fibres, fibroblasts and a layer of somatic cells which are apparently continuous with the cytoplasmic layer. This layer forms numerous microvilli at the surface.

Pronounced alkaline phosphatase activity was found in the sporocyst body wall, but no evidence of esterases was found in the parasite although esterase activity was readily demonstrated in the snail tissue that the schistosome parasitized.

It is concluded that the passage of substances such as glucose across the surface of the sporocyst is an active process probably mediated by enzymes and that little, if any, lipid metabolism occurs in the sporocyst stage.

1. O. gutturosa infections are of widespread occurrence in South-East England. 58% of 1583 cervical ligaments from milk cattle slaughtered in an abattoir at Reading, Berkshire, showed the presence of adult worms. A more detailed study of 50 cattle from a small abattoir near St. Albans in Hertfordshire showed 42 (84%) infected.

2. The adult worms were found either in the connective tissue adjoining the nuchal ligament or between the spleen and rumen. There was no evidence of an increase in the parasite density with age of the cattle suggesting a strong immunity to superinfection.

3. Irrespective of the situation of the adult worms the microfilariae of O. gutturosa appear to have a directional mechanism and were always concentrated in the skin around the umbilicus. This is an adaptation to transmission by Simulium ornatum which bites preferentially in the umbilical region.

4. There were no marked pathological changes associated with the parasites and no evidence of clinical disease attributable to infection with O. gutturosa.

1. Observations have been made on the behaviour of S. ornatum in relation to its role as a vector of O. gutturosa, a common parasite of cattle in Britain.

2. Most of the S. ornatum biting cattle alight on the ventral surface of the animal and it has been shown that this behaviour is affected by the degree of illumination.

3. The umbilicus is the preferred site for a blood meal by S. ornatum and it is this region where the microfilarial density is the highest.

4. The biting behaviour of S. ornatum is affected by the arrangement of the hair in relation to the skin surface. The umbilicus is preferred because here the hairs are so arranged that the flies readily gain access to the skin. The teats are bitten usually when fly activity is very heavy and then the umbilicus is covered with feeding S. ornatum.

5. The mean number of O. gutturosa microfilariae ingested by S. ornatum, but not the quantity of blood, increases with increased time spent feeding on an infected animal.

6. There is no causal relationship between the loss of blood per anum during and after feeding and the number of microfilariae ingested by S. ornatum.

7. Few microfilariae of O. gutturosa are lost per anum by S. ornatum during feeding despite the loss of blood by this route from the majority of flies.

8. The infective larvae of O. gutturosa are deposited by S. ornatum in the skin of the umbilicus of the cow from where they migrate to the neck or gastro-splenic region. This suggests that the worms possess an inherent directional mechanism determining their final site of development and that the point of inoculation of the infective larvae may have less importance in determining the sites of final maturation of Onchocerca species than has hitherto been believed.

A comparison of the characteristics of two strains of S. haematobium in experimental infections in hamsters is made. A limited study of these strains is also made in Mastomys.

Growth changes in male and female adult worms are compared, as are changes in the uterine egg counts.

The quantitative distribution of eggs in the tissues of the hamster is recorded. The approximate mean daily egg output per female worm for each strain is calculated at specified time intervals, and for the entire period of observations.

The recorded characteristics of the two strains of parasite are compared with those described for other strains of S. haematobium.

It is considered that the hamster provides a useful model for such studies provided that standardised infection procedures are employed.

It is considered that differences in host characteristics and susceptibility of individual animals account for the apparent variability recorded with regard to growth of parasites and egg depositions.

Infective third-stage larvae of Dracunculus medinensis in cyclops have been maintained at 37°C in normal saline containing from 0·05 to 1·0% of hydrochloric acid. At acid levels normally met with in the human stomach 50% mortality of emerging larvae occurred in 150 minutes, suggesting that the time taken for larvae to pass through the stomach may be of importance in determining whether an infection is successful or not.