Five new species are described and nine known species and one new combination are reported from new hosts and new localities. The new species are: Prosogonotrema pritchardae, Uroproctinella attenuata, Bivesiculoides scari, Stephanostomum attenuatum and S. adinterruptum. The known species are: Genolopa trifolifer Nicoll, 1915, Anaporrhutum albidum Brandes in Ofenheim, 1900, Hymenocotta mulli Manter, 1961, Pleorchis sciaenae Yamaguti, 1938, Mehratrema dollfusi Srivastava, 1939, Buckleytrema indica Gupta, 1956, Acanthocolpus tenuis Manter, 1963, A. liodorus Lühe, 1906, and A. luhei Srivastava, 1939. The new combination is Alloheterolebes indicus (Gupta, 1968).

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.

1. Individual chemical estimations of the glycogen concentration of the digestive gland and the foot were made on 272 uninfected L. littorea and 395 L. littorea infected with larval Digenea from Scalby Rocks, North Yorkshire, during the period from September 1966 to November 1967.

2. The glycogen concentrations of the digestive gland and the foot of both infected and uninfected L. littorea showed pronounced seasonal changes, being highest during the autumn and lowest in the spring. Infected L. littorea had less glycogen in the digestive gland and foot than had uninfected L. littorea, and the amount of reduction was characteristic for each of the three species studied, namely Cryptocotyle lingua, Renicola roscovita and H. leptosoma. Infection with C. lingua caused greater decrease in the glycogen concentration of the digestive gland, while infection with R. roscovita had a more marked effect on the foot. The effect of infection with H. leptosoma and with concurrent infections with two species are described and considered.

3. The seasonal changes in the amount of glycogen in the digestive gland and the foot of uninfected and infected L. liitorea are considered in relation to seasonal reproductive changes and the ecology of the host at Scalby Rocks.

S. maltheei females could mature and produce eggs in the absence of males in mice and hamsters but only nonviable eggs were produced during the 88 week observation period. S. mansoni, S. rodhaini and S. bovis females were studied under similar conditions for up to 30, 36 and 66 weeks, respectively, but in none of these species were any eggs produced by the female worms. The contrasting behaviour of S. mattheei and S. bovis is further evidence of their specific distinctness.

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 varying susceptibility of local races of bulinid snails to different strains of Schistosoma haematobium has been recorded by many workers including Le Roux, 1954; Cridland, 1955, 1957; McCullough, 1957, 1962; Wright, 1962, 1963; Cowper, 1963; Pitchford, 1965 and Paperna, 1968. The respective species groups of snails referred to are those created by Mandahl-Barth (1958). As a result of his experiments Le Roux (1958) suggested that there are two separate species of parasite, the form transmitted in North Africa by the truncates group of snails being known as S. haematobium and that developing in Africa south of the Sahara in the africanus species group as S. capense (Harley, 1864), a view which has been supported by many workers.

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.

Blood containing microfilariae has been successfully transported from various laboratories to London. This blood was used to infect mosquitoes with filarial parasites by means of a membrane feeding system. Brugia malayi, Wuchereria bancrofti and Dirofilaria immitis have been successfully transported in this way.

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.