Surface iodination, extraction and SDS-PAGE analysis techniques were employed to characterize and compare the surface polypeptides of two strains of Strongyloides ratti. Third stage infective larvae and parasitic adults of homogonic and heterogonic strains were studied using a variety of surface labelling procedures and detergents for the extraction of labelled molecules. Profiles obtained from SDS-PAGE analysis demonstrated that homogonic and heterogonic strains of S. ratti have identical surface antigens.

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.

One hundred and six of 109 common shrews (Sorex araneus) and 62 of 72 pygmy shrews (S. minutus), obtained by Longworth trapping in Southeast England, were infected with cestodes. Ten species were recovered: Choanotaenia hepatica and Hymenolepis prolifer (found in S. araneus); Choanotaenia crassiscolex, Hymenolepis furcata, H. jacutensis, H. schaldybini, H. scutigera, H. singularis, H. diaphana and H. infirma (in both hosts). The morphology, taxonomy and ecology of these species are discussed and the findings of the present study are discussed with reference to previous studies of the helminth fauna of British shrews. Cysticercoids of C. crassiscolex were found in the snail, Vitrina pellucida, and cysticercoids of H. schaldybini in the staphylinid beetle, Anthobium unicolor.

Zygocotyle lunata adults grown in mice were treated in vitro with 3-H-adenosine to label sperm and then transplanted to the caecum of mice singly or with 6 to 8 unlabelled adults. After 6 to 10 days, worms were recovered, processed for autoradiography, and observed for radioactive sperm in their seminal receptacles. Adults would not incorporate radioactive thymidine into dividing cells. Tyrosine was utilized only by juvenile worms and then not enough to label germinal cells for mating studies. Four of 13 (31%) worms transplanted singly self-inseminated, whereas 9 of 10 (90%) labelled worms in multiple infections self-inseminated. When in groups, the labelled worms cross-inseminated with 14 of 43 (33%) unlabelled worms. This mating pattern was unrestricted in that both self- and cross-insemination took place in multiple infections, much like the mating pattern in another paramphistomatid, Megalodiscus temperatus, but unlike the restrictive pattern shown by three species of eyeflukes.

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.

Adult Lymnaea truncatula were subjected to 10 days of experimental desiccation and then remained in water for 1 or 8 days before each was exposed to a single miracidium. The infection rate was lower in these snails than in infected controls that were not exposed to stress (52–54% vs 73%). The redial burden clearly decreased in stressed snails (18–25 rediae per snail) than in controls (43 rediae). This numerical decrease concerned essentially: i) live independent rediae of the first generation and the first cohort of the second generation, and ii) dependent rediae of subsequent generations. Mature rediae were more numerous in the first cohort of the second generation than in the other generations. Desiccation before exposure limited the size of the redial burden but placement in water for 8 days just after the stress attenuated the effects of this factor.

A survey was undertaken to study the epidemiology of Toxocara spp. in 350 dogs and 181 cats. A prevalence of 82.6% was recorded for Toxocara canis and 42% for T. cati. The distribution of parasite burdens in both dogs and cats was overdispersed. The highest parasite prevalence rates and burdens were found in hosts of 12 to 24 weeks of age. No Toxocara parasites were found in cats between 0 to 4 weeks old. There was no significant difference in parasite prevalence between male and female dogs or between male and female cats. The relationships between host age and sex with parasite prevalence, burden and length are discussed. Female T. canis worms with mature ova and those with immature ova differed significantly with regard to their length. The relationship between the length of mature T. canis female worms and the proportion of body length occupied by the uterus was highly significant.

The ultrastructure of various regions of the male reproductive tract and the prostate gland of Cotylophoron cotylophorum (Trematoda: Digenea) is described. The internal lining of the entire male duct system is syncytial in nature, and regional variation is quite evident. The syncytial epithelium of the vas deferens and seminal vesicle is very thin, flat and lamellate and the lumen is packed with spermatozoa. In the pars musculosa (PM) the syncytium is also flat but lamellae are sparsely distributed and anastomosed at places to form loops. The syncytium of the PM is invested by several layers of circular and longitudinal muscle. The pars prostatica (PP) is lined by an uneven but moderately thick syncytial epithelium with nuclei projecting into the lumen. The syncytium bears numerous very long lamellae. The ejaculatory duct epithelium is devoid of lamellae. It is even and moderately thick throughout. The prostate gland cells are uneven in outline and bear long ducts which open into the lumen of the PP. They show an ultrastructural organization suggestive of protein secretion.

The cytological study of males and females of Trichuris muris (Schrank, 1788) revealed the diploid number of chromosomes to be 2n=6. The sex determining mechanism was XX♀/XY♂. All the chromosomes were subtelocentric. Sex chromosomes formed the smallest pair, but X and Y were difficult to distinguish morphologically. Chromosome changes during gametogenesis in both sexes followed a classical pattern except in the male prophase and metaphase I. Four male autosomes formed two bivalents, each with one proximal chiasma with strict localization, while sex chromosomes X and Y formed two univalents. Female chromosomes formed three rod bivalents type, which possessed three, two and two chiasmata.

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.

The activities of some key enzymes of the glycolytic and pentose phosphate pathways were investigated histochemically in adult female Onchocerca fasciata (Nematoda: Filarioidea). The distribution patterns of phosphofructokinase (PFK), aldolase (ALD), glyceraldehyde 3-phosphate dehydrogenase (G3PDH) and glucose 6-phosphate dehydrogenase (G6PDH) in different tissues of the worm were determined by employing NitroBlue Tetrazolium (NBT). The glycolytic enzymes PFK, ALD, and G3PDH were distributed throughout the hypodermal tissue, somatic muscles and reproductive organs. These enzyme activities were predominantly expressed in the hypodermal and reproductive tissues, both of which appeared to be metabolically more active than adjacent tissues. The high activities of the enzymes studied in the hypodermal tissue when compared with the minimal or low activity in the intestinal epithelium support the assumption that the worm's intestine, in contrast to the body wall, plays no significant role in the nutrient acquisition process. The results emphasize that both the glycolytic and hexose monophosphate pathways of carbohydrate metabolism are active components in energy production and biosynthetic processes in the various tissues of the worm. The functional significance of these glucose-metabolizing enzymes has been discussed with regard to their location in the tissues concerned.

The complete gene encoding an immunodominant antigen of Dirofilaria immitis was isolated from a Charomid 9–36 genomic DNA library. This genomic DNA clone termed ‘Dg2’ was characterized by restriction mapping, DNA sequencing of the 5′ flanking region, the exon/intron boundaries and the polyadenylation addition site. The Dg2 with 4872 bp in length consisted of five exons interspersed with four introns. These exons reveal a single open reading frame followed by a long 3′ non-coding region of 1383 bp. The open reading frame of 969 bp encodes a polypeptide of 322 amino acids with a molecular weight of 34,400. The ATG translation initiation codon starts 22 nucleotides downstream from the 5′ end of the first exon. The polyadenylation signal sequence, AATAAA, is located at the 3′ end of the last exon. The transcription initiation site was determined by primer extension technique. S1 nuclease mapping analysis demonstrated that the primary transcript derived from Dg2 is synthesized in microfilariae but not in male or female adult worms. The result suggests that the stage-specific expression of Dg2 is regulated at the level of primary transcript.

An experiment was carried out to investigate the anthelmintic activity of papaya latex (Carica papaya) against natural infection of Ascaris suum in pigs. Sixteen naturally infected pigs were, on the basis of faecal egg counts and body weight, allocated into four groups, each of four pigs. Three groups (groups B, C, and D) were given papaya latex per os at dose levels of 2, 4, and 8 g of papaya latex per kg body weight, respectively. The fourth group (group A) served as a non-treated control. Results of post mortem counts on day 7 post treatment revealed worm count reductions of 39.5, 80.1 and 100% in groups B, C, and D, respectively. Some of the pigs receiving the highest dose of the latex showed mild diarrhoea on the day following treatment. Otherwise, no clinical or pathological changes were observed in the treated animals. The possible future use of this traditional herbal medicine for livestock and humans is discussed.

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.

The present study was designed to determine the susceptibility of domestic animals to an isolate of Taenia solium from Hainan Province, People's Republic of China. A total of 162 cysticerci were recovered from two pigs and 21 from two dogs after experimental inoculation. Cats, goats and a calf were not susceptible to T. solium. Cysticerci were recovered mainly from muscles of the pigs and all were alive. The remainder were in the liver and only one was alive. In the dog, all cysticerci were recovered from the muscles and all were alive.

The effects in vivo of 5, 10, and 20 mg/kg of luxabendazole (LBZ) on the tegument of Fasciola hepatica have been examined 48 h, 7 days and 14 days post-treatment of experimentally-infected rats. As early as 48 h post-treatment, the drug is shown to provoke significant damage to the tegument. The pathological phenomena characterizing LBZ damage are blebbing of the apical plasmalemma, formation of microvillus-like projections over the free surface, swelling of the basal infolds and stimulation of autophagy. The spines are often fractured; the tegument in the vicinity of spines seems more strongly altered than that in other foci. The basal layer is often changed, from increase of electron density to lack of integrity with the apical cytoplasm. The progress of the ultrastructural damage with time is not expressed. However, cytochemical data show that at longer post-treatment intervals the surface-coat structure becomes irregular and patches of ruthenium red positive material of variable thickness are focally accumulated. Only a slight dose-effect is noted 48 h after LBZ application when the alterations provoked by 5 mg/kg are less evident than those by 10 and 20 mg/kg.

Antibody responses against crude antigens and the two (Em18 and Em16) epitopes of Echinococcus mulfilocularis were analysed by Western blotting using sera from the wild vole, Clethrionomys rufocanus bedfordiae (Crb), which were captured in Hokkaido, Japan and found to have been naturally infected with eggs, and compared with those in patients of AHD and mice experimentally infected with protoscoleces of this parasite. Antibody responses in the wild vole were demonstrated most clearly with anti-Crb-IgG antiserum but more faintly with anti-rat-IgG antiserum and poorly with anti-mouse-IgG or anti-human-IgG antisera or Protein G. Although only two serum samples of the wild vole found naturally infected were analysed, antibody responses against Em18 and Em16 in these voles appeared to be similar to those in AHD patients but differed from those in mice.

A further modification of a lung perfusion technique was evaluated by examining the recovery rate of 14-day-old Dictyocaulus viviparus worms from the excised lungs of 15 dead bovine calves. Up to 89% of the total number of worms found in 12 l of perfused fluid was recovered in the first 4 l collected. The application of this observation will increase the efficiency of the routine laboratory diagnosis of D. viviparus infection.

Chamois (Rupicapra rupicapra tatrica) in the Low Tatra National Park are largely infected with the lungworms Mullerius capillaris and M. tenuispiculatus and sporadically with Dictyocaulus viviparus. The mean number of first stage larvae (Ll) per gram of faeces collected at chamois stands over the years 1981–1988 varied between 28.2 ( ± 11.9) and 61.6 ( ± 35.9). The degree of infection in chamois herds was significantly higher in the spring and autumn months, except for the spring of 1981, than in the summer season. The mean number of Ll per gram found in the dissected chamois (lung and intestinal content) varied between 64.53 ( ± 32.7) and 97.5 ( ± 36.4).

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.