Haemonchus contortus originally derived from an Ontario field strain was used to infect laboratory rabbits. Both ensheathed and artificially exsheathed larvae were given at doses of up to 10 million larvae per rabbit. Only artifically exsheathed larvae were infective and a dose of at least 50,000 was required to produce a significant level of infection.

H. contortus completed its development in the rabbit, but at a slower rate than in the sheep. Although a few fecund females were found 35 days after infection no eggs were observed on faecal examination. A high proportion of early fourth stage larvae were recovered from numerous rabbits including some which were examined well beyond a postinfection period when all worms should have been in the adult stage. This phenomenon occurred when freshly harvested and exsheathed larvae were used. Post-exsheathed cold conditioning of larvae at 5°C further increased the proportion of early fourth stage larvae (maximum proportions were found after 21 and again after 79 days of cold conditioning and thereafter declined). Whether such larvae were inhibited cannot be stated definitely. However, several of these larvae contained crystalline rods within their soma, and the structure of the crystals was similar to those previously described from inhibited H. contortus larvae recovered from sheep.

It was concluded that the laboratory rabbit could be a useful host for further studies on some aspects of the biology and pathogenicity of H. contortus.

Scheloribates laevigatus (Koch, 1836) and Scliehribates fimbriatiis (Thor, 1930), predominant species of oribatids in soil of Bombay region, were experimentally exposed to infection by uniform suspensions of eggs of Moniezia expansa and M. benedeni. The percentages of mites infected and the average number of cysticercoids developing were observed in 12 sets of experiments. The mites were more readily infected with eggs of M. expansa than with those of M. benedeni. S. laevigatus were infected with M. expansa and Jess with M. benedeni than S.fimbriatus.

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 ofNeodiplostomum, Conodiplostomum and Fibricola are discussed and possible significance of the fluke as an ecological indicator noted.

Analyses of primary infections of Nematospiroides dubius in male and female laboratory mice show that on days 4–6 post-infection worms occupy up to 50% of the small intestine but as the age of the infection increases worm populations are highly aggregated in relation to the anterior sections of the small intestine. Individual worms are also shown to be aggregated with respect to each other. Between days 42 and 60 postinfection, although the pattern of distribution of N. dubius along the small intestine does not significantly change, survival of worms is influenced by both age and sex of ASH/CSI S.P.F. mice, reasons for which are discussed in the light of previous work on primary infections of N. dubius in other strains of laboratory mice

Schistosoma rodhaini is a parasite of rodents and dogs in some parts of Africa, south of the Sahara (Schwetz, 1952; Deramée et aly 1953; Berrie & Goodman, 1962; Nelson et al.f 1962). Occasional human infections have also been reported (Haenens & Santele, 1955).

The only comprehensive study reported in the literature on the histopathology of S. rodhaini is that of Thienpont et al. (1953) in naturally infected dogs. Saoud et ah (1966) briefly described the tissue reactions in chronic heavy infections of the Kenya strain in hamsters. It has been found that the pancreas is one of the visceral organs seriously involved in schistosomiasis rodhaini of hamsters.

Attention has been drawn to the fact that the occurrence of the cystic stage of Echinococcus granulosus in 60% of slaughtered horses represents a potential public health hazard (Thompson and Smyth, 1974). Williams and Sweatman (1963) regard this organism as a separate sub-species, E. granulosus equinus distinct from E. granulosus granulosus, but we prefer at this stage to refer to it as the horse “strain” which exhibits some small morphological differences from organisms of sheep origin.

According to Miyazaki (1974), 25 species belonging to the genus Paragonimus have been found in the world. In Japan, five species of the lung flukes, viz., P. westermani, P. ohirai, P. iloktsuenensis, P. miyazakii and P. sadoensis have been known up to date. P. ohirai metacercariae are found in the liver, and in the body and leg muscles of the brackish water crabs, Sesarma (Holometopus) dehaani, S. (H.) haematocheir, S. (Sesarma) intermedium, Helice tridens tridens and Chasmagnathus convexus.

Two metacercariae of Haplorchoides, recorded in the fingerlings of over a dozen species of freshwater fishes, are described and illustrated. Oyigerous flukes were recovered from older specimens of two species of fishes procured from the same locality. Comparison of taxonomic characters of the juveniles and adults suggests that they are conspecific. The metacercariae and adults are assigned to two new species, Haplorchoides pearsoni and H. mehrai. The observations, presented herein, necessitated a review of the species named under this genus and a revision of the generic diagnosis. The reports on fish intermediaries of H. attenuatus have been enlarged.

It was shown that maintenance of cercariae of S. mansoni and S. haematobium at low (10°C) and high temperatures (40°C) markedly increased their mortality during penetration of mammalian host skin. These increased losses in the skin accounted for the known decrease in infectivity, as measured by adult worm recovery, of cercariae kept at low or high temperatures.

Wild house mice, naturally infected with Aspiculuris tetraptera were segregated according to their weight into six age groups. The prevalence of infection and the mean worm burden of these mice were studied in the different age groups. The overall prevalence of infection was high (57% or more) in all the groups except the youngest. Mice acquired larvae soon after weaning; the highest larval burdens were reached in juvenile mice and the highest mature worm burdens, a group later, in mature mice. Older mice had fewer larvae and fewer mature worms. The mature worm burdens decreased but relatively slower than the larval burdens. It is suggested that either innate or acquired resistance could account for these observations.

A total of 21 species of Cyathostominae was found in the lumen of the large intestine of 86 mature horses of various ages and breeds killed in south-west England during 1972–1974. Cylicostephanus longibursatus, C. goldi, C. calicatus, Cyathostomum catinatum, C. coronatum and Cylicocylus nassatus were found in over 80% of the horses, while 12 of the remaining species were detected in less than 30%. Quantitative studies on 55 horses showed the adult cyathostome burdens to rise to a sharp peak (average over 400,000/horse) in April-June and a lower one in November-December. Parallel fluctuations occurred in the lumen populations of 4thstage larvae. The most numerous cyathostomes were generally those species with the highest prevalence. The five most plentiful (C. nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, C. minutus and C. goldi) comprised over 90% of the total number of adult cyathostomes recovered. The three regions of the large intestine had adult cyathostome faunas of different composition. That of the dorsal colon was dominated by C. longibursatus and C. goldi, the ventral colon by Cylicocyxlus nassatus and Cyathostomum catinatum, while the sparsely inhabited caecum accommodated several equally numerous species. Each species showed a characteristic site distribution, 11 occurring predominantly in the ventral colon, eight in the dorsal colon and two in the caecum. Seasonal changes in the site distributions of C. catinatum and Cylicocyclus nassatus and in the size of the cyathostome burdens are discussed in relation to the epidemiology of cyathostome infections.

In an attempt to develop a non-pathogenic procedure for immunising baboons against S. mansoni, groups of five baboons were exposed to three doses of 5000 6 Kr-irradiated S. mansoni cercariae or to similar numbers of normal S. rodhaini cercariae and challenged at week 15 with 500 normal S. mansoni cercariae. Faecal egg counts, worm and tissue egg counts, and histopathological examination, showed that neither of the immunising schedules had produced significant protection. In the second experiment baboons were injected by the intramuscular route with 31000 schistosomula of S. mansoni in three doses and the irradiation dose was reduced to near the minimum required for worm sterilisation (2·1–2·4 Kr). Challenge with 3500 normal cercariae of S. mansoni 21 weeks after the first immunising dose again showed no significant protection, although reductions of 20–30% were found, in egg and worm counts resulting from the challenge. These results indicate that it may be difficult to develop an effective live vaccine for S. mansoni unless the antigenicity of the immunising larvae can be greatly increased.