The species of the genera Longistrongylus, Kobusinema and Bigalkenema are redescribed. Kobusinema and Bigalkenema are considered synonyms of Longistrongylus and their species are transferred as new combinations. Bigalkenema neveulemairei (Gutteres, 1947) Jansen, 1958 and Longistrongylus muraschkinzevi (Shulz and Kadenatsii, 1950), Jansen, 1958 are considered species inquirendae. A key to the species of the genus Longistrongylus is given and their hosts and geographical localities are listed.

Monanema nilotica n.sp. (Nematoda: Onchocercidae) is described from the right auricle and pulmonary artery of the Nile rat, Arvicanthis niloticus testicularis (Sundevall, 1842), trapped in Khartoum-North, Sudan. It differs from other species principally in length of adults and microfilariae, in the shape of the buccal capsule and in the structure of the spicules of the males.

Dietary feeding of drugs for 5 days to mice infected with Nematospiroides dubius and Hymenolepis nana detected all modern anthelmintics examined except stilbazium. A simple test using eggs of Nematodirus spathiger and adult Nippostrongylus brasiliensis to detect anthelmintics in vitro is reported.

Schizorchis arfaai sp. n. is described from the wood-mouse in the Caspian area of Iran and its morphological characteristics compared with those of the five previously known species of Schizorchis Hansen, 1948.

A further survey in East Caprivi, Chobe National Park, Okavango swamps and Kavango was undertaken in June 1976. No evidence of lechwe schistosomes was found in droppings of African buffalo (Syncerus caffer) nor baboons (Papio ursinus) living in lechwe habitats. It was thought that they were not capable of spreading or maintaining these parasites outside the confines of the known distribution of Kobus sp. The role of goats was equivocal but probably they too are poor hosts.

Kavango, an endemic area of S. haematobium and S. mansoni, was thought to be free of all animal schistosomes, thus confirming the hypotheses that (1) cattle and goats are poor hosts of the lechwe schistosomes and (2)S. mattheei was blocked from entering the territory by the presence of lechwe schistosomes in the surrounding areas. Evidence of schistosomes was not found in cattle and goats at Maun for the same reasons. The prevalence of S. mansoni at Maun has increased alarmingly over the past 20 years with a simultaneous disappearance of lechwe from the area. S. margrebowiei and S. leiperi eggs were found in lechwe and tsessebe droppings some 80 km north of Maun.

A high proportion of children with negative excreta from “non-endemic” areas in East Caprivi had positive CFT and/or skin tests, suggestive of exposure to lechwe schistosomes resulting in a possible immunity to S. mansoni and S. haematobium.

Over 90% of Schistosoma haematobium and S. mansoni infections show a dominance of male worms in experimental animals. Male: female ratios as high as 5: 1 are common in S. haematobium (Ghana) infections and 1·5: 1 is a typical ratio in S. mansoni infections. The male parasite seems to be more successful than the female in reaching maturity. To test this theory experiments were set up to compare the infectivity of male and female cercariae.

Border Leicester X Suffolk sheep infected with a strain of S. mattheei maintained in hamsters do not develop the same pathological changes as Romney Marsh sheep infected with the same strain of parasite before hamster passage. To determine the cause of this reduced pathogenicity, five Romney Marsh sheep were each infected with 10 000 cercariae of the hamster-passaged parasite and five with 10 000 cercariae of a S. mattheei strain from Onderstepoort, South Africa, passaged exclusively through sheep.

Striking pathological and parasitological differences were found between the two strains. Infection with the “sheep” strain was lethal, whereas infection with the “hamster” strain produced little evidence of clinical disease. By 13 weeks post-infection the mean body weight of the sheep infected with the sheep strain had declined by 15% compared with both the uninfected controls and the sheep infected with the hamster strain, and the mean PCV was lowered to 20% in the sheep strain infected animals. Egg production began at seven weeks with the sheep strain, faecal counts rising to more than 300 e.p.g., whereas only two of the sheep infected with the hamster strain passed eggs in the faeces (at nine weeks) and the maximum egg count was 50 e.p.g. Twice as many adult worms of the sheep strain were recovered, and, although the number of eggs found in the tissues “per worm pair” was not significantly different, overall egg production was higher for the sheep strain; also more of the sheep strain eggs were deposited in the intestines. Similar parasite differences were seen in a supplementary study in mice and it seemed that “attenuation” of the parasite had occurred, presumably due to its maintenance in hamsters. Histopathological observations and faecal egg counts both indicated an inability of hamster strain eggs to penetrate the intestinal lumen; this was probably important in reducing the pathogenicity of the hamster strain.

Two strains of laboratory white mice, CFLP and LACA, were infected with the metacestodes of Taenia crassiceps. The serum from each infected mouse was tested for antibodies on double-diffusion gel plates and the number of antigen-antibody precipitin lines formed related (a) to the duration of the infection and (b) to the volume of metacestodes. There was a significant increase in the number of antigen-antibody precipitins with regard to the time infected but not to the volume of metacestodes. The pattern of development of the antigen-antibody precipitation system was also examined.

In the article by P. Stevenson and D. E. Jacobs entitled: “Toxocara infection in pigs. The use of indirect fluorescent antibody tests and an in vitro larval precipitate test for detecting specific antibodies” which appeared in Volume 51, No. 2, June 1977 issue of the Journal of Helminthology, pages 150 and 151 were inadvertently transposed.

Several methods are being applied for solubilizing adult Schistosoma mansoni antigens which may allow their immunochemical characterization and purification. Studies on antigens and immunoprecipitins in schistosome infections have been carried out with homogenized extracts of adult worms and/or larval forms of Schistosoma mansoni in saline (Biguet et al., 1962; Kagan and Norman, 1963; Silva and Ferri, 1965), or water (Kent, 1963). Kusel (1972) studied surface proteins in S. mansoni membrane, treating the worms with 0·5% saponin in 3% calcium chloride. Murrel et al. (1974) compared by immunodiffusion a crude culture antigen with extracts obtained by freeze-thawing of adult worms and by treatment in 3M KCl.

The humoral response of guinea pigs infected with doses of 500, 1000, and 1500 infective Toxocara canis ova were measured by counterimmunoelectrophoresis and indirect haemmagglutination tests one to five weeks after infection. The antigens used in these measurements were prepared from adult T. canis. Counterimmunoelectrophoresis showed lower titres than haemagglutination method, but it was performed rapidly and with case. The possible use of these techniques for immunodiagnosis of human visceral larval migrans is discussed.

The influence of temperature and ultra-violet radiation on the degree of activity, survival and infectivity of schistosome miracidia is profound. Miracidia of Schistosoma mansoni and S. haematobium were affected equally. Only miracidia classified as “active” or “slow” were capable of penetration, a capacity they retained for about 17 hours at 19°C. Miracidia that were “lethargic” as a result of low temperature, old age or ultra-violet radiation lost their infective capacity. The conclusion, however, is that neither the temperatures encountered in the field nor the solar ultra-violet radiation penetrating turbid waters are likely to be harmful to miracidia and thus have no effect on the level of transmission.

Laboratory rats were infected by intra-peritoneal injection with the metacestodes of Taenia crassiceps. A soluble extract was prepared from the metacestodes removed from the peritoneal cavity of the rats. Doublediffusion, immuno-electrophoresis and fluorescent labelled antibody staining techniques were used. The extract tested against rabbit anti-normal rat serum was found to contain an antigen common to both the host and the parasite.

We have previously described the characteristics of a relatively non-pathogenic laboratory strain of S. mattheei, attenuation of which was apparently caused by passage in hamsters. We now show that chronic infection with this avirulent strain largely protects sheep from the manifestations of acute schistosomiasis when challenged with a virulent strain of S. mattheei.

Four sheep were each infected with 10 000 cercariae of the avirulent strain and, together with four worm-free sheep, challenged 63 weeks later with 10 000 S. mattheei cercariae of a pathogenic strain. Four more sheep acted as uninfected controls. Following challenge, the animals were weighed and bled weekly for PCV and serum protein determinations, and egg counts were carried out fortnightly on faeces taken from the rectum. Red cell and albumin turnover were monitored for two weeks immediately before challenge and for a similar period before necropsy, when the adult worms were recovered by perfusion and tissues sampled for histopathology and egg counting.

The unvaccinated sheep developed severe disease 6—12 weeks after exposure characterised by marked anaemia, hypoalbuminaemia and hyper-gamma globulinaemia coinciding with the passage of blood-stained faeces and progressive inappetence. In the vaccinated sheep, there was and even earlier rise in gamma globulins, but the other clinico-pathological changes were generally slower to develop and much milder in severity. The parasitological data showed that although this was partly due to a reduction in the establishment of the challenge worm population the main factor was probably a reduction in the fecundity of these worms.