Genomic DNA extracted from laboratory and wild subspecies of the trichostrongyle nematode Heligmosomoides polygyrus were compared using RFLP and DNA/DNA hybridization techniques. Eight restriction endonuclease digests of the genomic DNA of the two subspecies were hybridized with heterologous ribosomal DNA probes and the total radio-isotope labelled DNA of the laboratory subspecies. DNA hybridization of the two subspecies of H. polygyrus yielded different banding patterns when probed with the rDNA clones in Pvu II digests and when total genomic DNA was used as the probe in Hind III and Pvu II digests. The remaining hybridization profiles of both subspecies were identical.

An analysis of Hymenolepis diminuta specific antigens in infected rat faeces was carried out. Using a capture type antibody sandwich ELISA assay based on a hyperimmune rabbit anti-worm somatic antisera it was demonstrated that, although antigen was present in faeces before patency, the onset of egg production led to a sharp increase in the levels of parasite antigen in the faeces. Levels of antigen in host faeces were independent of worm burden. Parasite eggs did not contribute significantly to faecal antigen levels. Western blot analysis indicated a number of highly specific antigens at around Mr 69,000, Mr 37,000, Mr 50,000 and Mr 27,000 with a low molecular weight smear at between Mr 30,000 and Mr 34,000 present in the faeces of H. diminuta infected rats. Some cross reaction occurred with an antigen of around Mr 66,000 in the faeces of non H. diminuta infected rodents. Antibody activity against this antigen was removed by affinity adsorption of the antibody solution against normal rat faeces.

The rhythmicity of egg production by Heligmosomoides polygyrus (Nematoda) in wild caught wood mice (Apodemus sylvaticus) was studied. Faecal production followed a 24 h cycle, with peaks at 0400 h and troughs at 1300–1900 h. The patterns in eggs per gram of faeces (EPG) and total eggs were similar to each other, though the former was more accentuated. Both of these followed a 24 h cycle, with peaks coinciding with troughs in faecal production and vice versa. Faecal weight was inversely correlated with EPG, but was not significantly correlated with total eggs. The pattern in EPG presumably reflected the effect of faecal production on the total eggs excreted in each 3 h period. The observed cycle in total eggs probably describes the pattern of egg production by the worm, although other factors, such as the host's intestinal rhythms, may contribute to this cycle.

DNA from species and races of plant parasitic nematodes (Meloidogyne, Globodera and Heterodera) and a human parasitic nematode (Trichinella) were subjected to polymerase chain reaction amplification using one arbitrary primer (M-10). This technique results in relatively simple DNA profiles that include polymorphic markers known as random amplified polymorphic DNA (RAPDs). The RAPD profiles of the plant nematode species of Meloidogyne made possible the identification of M. incognita and M. hapla, but no differences were found between the patterns of M. javanica, M. arenaria and M. graminicola. Moreover, the four races of M. incognita were indistinguishable by this primer. In contrast, when races of the plant nematode Globodera rostochiensis (Ro1 and Ro2/3) were studied under the same RAPDs conditions, a race specific profile allows these two most devastating races to be differentiated. When DNAs of eight Trichinella isolates were subjected to RAPD studies, four different patterns were identified, corresponding to the four Trichinella clusters previously defined by isozyme polymorphism.

Fasciola hepatica miracidia were experimentally introduced into five sites colonized by Lymnaea palustris over a period of 4 or 6 years. In the first four ponds, a progressive increase in the prevalence of the spring-generation juvenile snails was observed (from 0.4 to 18.1%), with a corresponding increase in the shell height of infected snails (from 3.6 to 7.8 mm). In the fifth habitat, the pond dried in 1990 causing the prevalence to drop as compared with the initial values and to subsequently increase in 1991–1992.

In epidemiological surveys for urinary schistosomiasis caused by Schistosoma haematobium in communities around Agulu Lake, Anambra State, Nigeria, between 1990 and 1992, the infection was found to be endemic in the area, especially in three towns: Nri, Agulu, and Adazi Nnukwu. The prevalence rates varied between these communities and with the year. Inter-town prevalence rates ranged from 5.96% to 54.00%. Intravillage prevalence rates ranged between 5.50% to 96.43%. Prevalence rates were highest in villages very close to Agulu lake. There was no significant difference in prevalence between the schools. Host age, but not sex, was found to play a significant role in prevalence and intensity of infection. There was also a strong correlation between visible haematuria and egg count per 10 ml urine, but eggs could be isolated in urine samples of different shades of coloration. Analysis of incidence of infection in these communities shows that Schistosoma haematobium incidence is high in Nri (55.17%) and low at Adazi Nnukwu (5.26%). Both Bulinus globosus and B. truncatus were found in the lake and both shed mammalian bifid schistosome cercariae.

Thirty-four albino mice were each exposed to 20 cercariae of Schistosoma japonicum by the intraperitoneal or percutaneous route and killed after 60–127 days. The peritoneal cavity of each mouse was flushed and worms in the portal vein system were perfused with citrated saline. After sedimentation, washings were examined microscopically. Mature worms were only found in the portal vein system. The worm recovery rate was much higher by percutaneous infection (61.2%) than by intraperitoneal (37.1%). The encapsulated egg granulomas were observed either in the peritoneal cavity or on the intestinal wall; the mean number of encapsulated egg granulomas was also higher in the former (1.6) than in the latter (0.6). The average number of eggs per granuloma was very similar by both routes (10.7 and 11.4). The mean size of encapsulated egg granulomas (529 μm) was increased correspondingly with the number of eggs (range 181–985 μm). The percentage of viable eggs within the granulomas in the peritoneal cavity (77%) was much higher than those on the intestinal wall (18%). Encapsulated egg granulomas were usually ovoid although some had an irregular shape.

Female ICR mice, 6–8 weeks old, were exposed to 100 metacercarial cysts/host of Echinostoma trivolvis to determine the effects of this cyst dosage on worm infectivity, distribution, growth and acetabular attachment in the host small intestine, Of 42 exposed mice, 22 were infected 4 to 17 days postinfection (PI) with a mean worm recovery of 11 to 41%. Mean body area of worms increased from about 0.4 mm2 on day 4 PI to about 2.0 mm2 by day 9 PI. No consistent pattern of worm growth was seen beyond day 9. Distribution data showed that worms were found mainly in the anterior part of the small intestines on day 4 PI and then more posteriorly up to day 8 PI. Worm distribution patterns were quite variable beyond day 11 PI. Scanning electron microscopy showed that the acetabulum left a distinct ‘fingerprint’ or acetabular plug on the intestinal mucosa of the host. The ‘fingerprint’ was temporary and disappeared within 1 min after worms were removed from the intestines.

To study the distribution of Lymnaea truncatula in the Porma river basin (León, NW Spain) and its helminth fauna, malacological samplings were carried out at 66 points in the basin and the presence of these molluscs was detected in 31. To trace the dynamics of this mollusc population and the prevalence and intensity of its infection by trematodes, malacological samplings were made at fortnightly intervals over two years at five locations, situated in the upper and middle regions of the river Porma basin. To confirm the identity of the larval stages found in the molluscs, second intermediate and/or definitive hosts, depending on the trematode species, were experimentally infected to complete the life cycles. Two different species of Plagiorchiidae and one of Notocotylidae were identified. The infection prevalence of Plagiorchis elegans for the 6291 specimens of L. truncatula examined was 2.8% and infection was observed in snails collected in 7 of the 31 sample localities. This parasite was found in all months of the year, with the highest prevalence observed in July and October. When the corrected frequency values were considered, a slightly positive relationship was observed between the infection prevalence and the latter months. The highest percentages of snails harbouring immature sporocysts were detected in March and June–July, while the highest percentages with sporocysts containing mature cercariae were observed in spring and at the end of summer–autumn, and cercarial shedding in the latter. Of the 6291 L. truncatula examined 0.3% were infected by sporocysts of Opisthioglyphe ranae. The infection was detected in only one locality, in four months of the year, with the highest prevalence in May. Notocotylus neyrai was found in 2.6% of the 6291 mollusc specimens checked and was collected from 12 of the 31 localities. The highest prevalence was observed in October, April and July and the corrected frequency values reveal a positive relationship between the infection prevalence and those three months. The highest percentage of molluscs harbouring rediae of N. neyrai with germinal mass was found in April and September–October. On the other hand, rediae with mature cercariae were present in almost every month, but we only observed cercarial shedding in October and March. The L. truncatula infection prevalence by P. elegans, O. ranae and N. neyrai increased with the size of the molluscs. Double infection was only observed in four snails: one harboured O. ranae and N. neyrai and three F. hepatica and P. elegans.

Compressed organ autoradiography has been utilized to study the migration of the homogonic strain of Strongyloides ratti from the site of skin penetration to the gut. This transit is characterized by rapid disappearance of parasites from the cutaneous site of infection, followed by vascular dispersal throughout all organs investigated. For the first time, parasite migration in both naive and previously sensitized hosts is compared; the principal stations of migration are the same in the two groups although there is a quantitative difference in accumulation of parasites with time in these stations. Parasite attrition occurs in both groups of animals; however, in naive rats it is not manifest until day 20–25 post challenge, whereas in sensitized rats immune elimination occurs as early as 48 h post challenge.

The alimentary tract of adult Sanguinicola inermis Plehn, 1905 (Digenea: Sanguinicolidae) was studied by transmission electron microscopy. A highly developed muscular region, likely to be a modified sucker, is present anteriorly to the oesophagus. The tegumental oesophagus, on the basis of the characteristics of the surface cytoplasm, is differentiated into anterior, median and posterior regions with the apical cytoplasm of the median oesophagus drawn into extracellular vesicles from which arise surface knobs. The oesophagus leads to a cellular intestine composed of a single layer of epithelial cells. The apical surface of the intestine is drawn into short luminal projections and the intestinal cells contain numerous organelles and secretory granules. No host cells or cell debris were evident within the alimentary tract, although the intestinal lumen was filled with electron-dense material.

The prevalence of onchocercosis was determined in three Local Government Areas (Ezeagu, Oji-River and Uzo-Uwani) in Enugu State, Eastern Nigeria between March 1989 and June 1990. Enugu State was shown to be mesoendemic for onchocercosis. A total of 7472 (26.9%) persons out of 27,831 examined were positive for skin microfilariae. There was no significant difference in infection rates between males (27.6%) and females (26.2%). Of the 118 villages surveyed only five had no inhabitant with skin microfilariae. There was a progressive increase of prevalence to the second decade of life, although 96.6% of cases with skin microfilariae had only a light infection. Onchocercomata prevalence was recorded as 27.3% which tallies with the prevalence of skin microfilariae at 26.9% hence onchocercomata prevalence may be used as a yardstick for predicting skin microfilariae prevalence.

Dictyocaulus viviparus were harvested from calves treated daily with albendazole at dose-rates sub-lethal to this parasite and from matched untreated calves. Male and female reproductive tracts from the worms were examined by light and transmission electron microscopy. A first description of the testis of this nematode is provided. Cell division in the germinal zone of both male and female worms was arrested by in vivo exposure to albendazole metabolites and the cytoplasmic threads connecting the germinal cells to the rachis disappeared. In male worms from treated calves, the rachis was absent from the growth zone and severe ultrastructural damage of spermatogonia, spermatocytes and spermatozoa was apparent. In female worms, the rachis remained intact in the growth zone, obvious abnormalities being confined to the germinal zone, where the cytoplasm of the oogonia was disrupted and few nuclei seen, and to the uteri and ovijector which contained only undifferentiated ova. The detrimental effects of albendazole metabolites on male and female worms were quickly reversed after withdrawal of medication.

Experimental studies of mating behaviour of Schistosoma intercalatum and Schistosoma mansoni in mixed infections in mice showed that in simultaneous infections, without the possibility of choice of mate, heterologous pairing occurs readily. The paired females reach sexual maturity, are inseminated and lay parthenogenetic eggs. Miracidia originating from the S. mansoni male × S. intercalatum female are non infective to either Biomphalaria glabrata or Bulinus forskalii, whereas those from the reverse cross show a very low infectivity to only B. glabrata. The resulting haploid male cercariae also show a very low infectivity to mice (1.1%) and consequently only a very small number of adult worms develop. It appears from this study, on chromosomal and electrophoretic evidence, that generative (haploid) parthenogenesis occurs in S. mansoni females paired with S. intercalatum males.

An attempt was made to control Ostertagia ostertagi by feeding the nematode-trapping fungus Duddingtonia flagrans (DSM 6703) to grazing calves. One group of calves (group E) was fed the fungal material in the first two months of the grazing season while another group was a non-treated control group (group C). Group E showed significantly lower faecal egg count in August and September. On four occasions in July and September, the herbage larval counts were significantly lower on the plot with the fungal-treated group than those recorded on the control plot. The average abomasal larval and adult worm counts were significantly reduced in August in group E and the average total worm count in the abomasum of group E was reduced by 87% in August compared to the non-treated group C. In October, the difference in average abomasal worm counts between group E and C was insignificant. Due to weight loss at the end of the grazing season, the control group showed a significantly lower average weight increase.