A low molecular weight fraction (30 KDa) of the cattle filarial parasite Setaria digitata that was earlier demonstrated to have allergenic activity was characterized to be a zinc-dependent cysteine proteinase. Immediate type hypersensitivity (ITH) reaction to the proteinase was evaluated in lymphatic filariasis patients and in endemic controls from Orissa, India. The extent of ITH positivity to the proteinase in infected individuals ranged from 20% in chronic filariasis (CP) patients group to 56% in asymptomatic microfilaraemic carriers (AS). About 62% of endemic normals (EN) were also ITH positive. The serum levels of IgG subclasses were compared in ITH positive and ITH negative filarial patients (AS and CP) as well as in endemic normals (EN) respectively. IgG4 levels were found to be inversely dependent on ITH reaction only in AS groups. Asymptomatic patients (AS) with positive ITH reactivity had lower IgG4 than ITH negative individuals from the same group. The serum levels of other IgG subclasses except IgG2 did not correlate with ITH reactivity. IgG2 levels were higher in ITH negative EN and CP patients but not in the AS group.

The efficacy of the salt flotation technique using saturated solutions of sodium nitrate (specific gravity 1.30) and zinc sulphate (specific gravity 1.16) for separating Ascaris lumbricoides eggs from clay, loamy and sandy soils has been investigated. Ten samples of each of the egg concentrations of 100, 500, 2500, 5000 and 10,000 eggs/25 g of soil were used for each soil type. Using T-test and ANOVA, the number of eggs recovered from sand was significantly higher than from loam and the number from loam significantly higher than from clay. With sodium nitrate, the maximum egg recovery rate was 25.04% from sandy soil at a concentration of 500 eggs/25 g soil while with zinc sulphate it was 13.88% also from sandy soil and concentration of 500 eggs/25 g soil. While the number of eggs recovered increased with soil egg concentration, the percentage of eggs recovered is inversely proportional to egg concentration. The number of eggs recovered with sodium nitrate was significantly higher than with zinc sulphate solution in the three soil types.

Faeces containing a mixture of Hyostrongylus rubidus and Oesophagostomum spp. eggs were mixed with vermiculite and water and set up at combinations of different relative humidities (65.5%, 79.5%, 90.0% and 100%) and temperatures (5°C, 10°C, 15°C, 20°C, and 25°C) in order to study the rate of egg hatching and larval development. The study established that the development from egg to infective larva showed similar patterns for the two parasites. Optimum development and survival was in the temperature range from 15°C to 20°C and ata humidities from 79.5 to 95.5%.

A study was carried out in four vifiages of Makenene Sub-Division some 85 km north-west of Yaounde, between November 1993 and March 1994 to assess the prevalence and intensity of schistosomes and other helminth infections among senior primary school pupils aged 9–16. An extensive questionnaire was used to collect sociodemographic information and information on water-related activities.

The overall prevalence of S. mansoni infection was 228 (23.6%) while S. haematobium infection was practically non-existent 03 (<1%). Infection rates with intestinal nematodes were very high, up to 98% in some villages. Prevalence rates of schistosomiasis varied significantly (P<0.05) between vifiages with the highest (36.2%) recorded in Makenene. Infections with other parasite species encountered were significantly different (P<0.01) while a marked association was observed between water contact activities and the distribution of S. mansoni infections. However, S. mansoni infection intensities were not significantly different (P>0.05) between those with a history of previous infection and treatment and those without.

This study was carried out to compare potential methods of transplanting adult Oesophagostomum dentatum from experimentally infected donor pigs to helminth naive recipient pigs. The following methods were each tested in five pigs: A. Transfer of worms by stomach tube to the gastric ventricle of pigs per os pretreated with 0.5 mg/kg cisapride to increase gastrointestinal peristalsis; B. Transfer by stomach tube to the gastric ventricle of pigs per os pre-treated with cisapride (0.5 mg/kg) and omeprazol 20 mg which blocks hydrochloric acid secretion; C. Surgical transfer of worms to caecum of pigs. Worms for transplantation to pigs were obtained after slaughter of experimentally infected donor pigs and following isolation from the contents of the large intestine, using an agar gel migration technique. A mean of 1054 nematodes were transferred into each recipient pig within 2 hours. Procedures A and B resulted in establishment rates corresponding to only 0.5% and 7.6% of the transferred worms. In contrast, surgical transfer allowed 74.2% of the transplanted worms to be established. In all groups the transplanted worms migrated to the normal predilection site, i.e. the middle part` of the large intestine. More female than male worms established in all groups. It was concluded from this study that surgical transfer was the most reliable of the methods tested for experimental establishment of adult O. dentatum in helminth naive pigs.

The subchronic effect of mercury on selected immunological parameters was studied in guinea pigs with experimental Ascaris suum infection. HgCl2 given for 28 days reduced significantly T- and B-cell populations in the lymphoid organs and the phagocytic ability of peritoneal macrophages. The subsequent infection of HgCl2-intoxicated animals elevated the studied immunological parameters, but in comparison with infected non-intoxicated guinea pigs they remained significantly suppressed. The mercury compound in infection stressed animals caused a slight alteration of the complement CH50 and AH50 activity. The specific circulating antibody level in infected and HgCl2 treated animals rose a little by day 12 p.i. and then again decreased significantly, compared with untreated guinea pigs. The mean intensity of infection with migrating Ascaris larvae in HgC12 -treated animals increased by 15%, compared with controls.

A mitochondria-rich fraction isolated from the cuticle-hypodermis-muscie system of Setaria cervi, a bovine filarial parasite, possessed substrate-coupled cytochrome c reductases and cytochrome c oxidase in appreciable activities. All these activities were located predominantly in the membranes. NADH-coupled cytochrome c reductase was more prominent than NADPH- and succinate-coupled reductases. All the three reductases exhibited marked sensitivity to rotenone and antimycin A. Salicylhydroxamic acid strongly inhibited succinate requiring reductase and cytochrome c oxidase, but the other two reductases only mildly. Sodium azide activated the reductases but substantially inhibited the oxidase activity. Potassium cyanide activated the succinate requiring reductase but did not cause any noticeable change in the activities of pyridine nucleotide linked reductases. Anthelmintics also influenced these activities but no definite correlation could be drawn regarding their mode of action.

The karyotypes of the two amphistomes Calicophoron microbothrium Fischoeder, 1901 and Carmyerius gregarius (Looss, 1896), Stiles & Goldberger, 1910 from Egyptian ruminants were studied using the air drying technique. The two species have similar number of chromosomes (n = 9), but differ in chromosome morphology. All the chromosomes of C. microbothrium are subtelocentric, except the first and the fifth are metacentric, whereas the chromosomes of C. gregarius are submetacentric, subtelocentric and acrocentric. Some cells in the two species showed tetraploidy. The results are discussed in terms of the phylogenetic relationship of different amphistomes.

Cytochrome c oxidase in the mitochondria of the tegument and tegumental and parenchymal cells was examined cytochemically in Echinostoma trivolvis, Zygocotyle lunata, Schistosoma mansoni, Fasciola gigantica and Paragonimus ohirai, trematodes that inhabit different sites in their vertebrate hosts. Clear differences in enzyme activity occurred in the mitochondria of these species, probably reflecting the different energy metabolisms of these worms. Marked aerobic metabolism occurred in S. mansoni and P. ohirai adults that inhabit the host mesenteric veins and the lungs, respectively. The tegument and parenchymal cells of S. mansoni possess relatively few, small mitochondria with tubular cristae which are heavily reactive for cytochrome c oxidase. In P. ohirai, the activity for cytochrome c oxidase in tegumental mitochondria increased gradually from juveniles to adults, reflecting that the respiratory activity increased with growth and the aerobic metabolism is activated when the worms reach the lung. P. ohirai juveniles and adults had two types of mitochondria with different shapes and enzyme activities that were located in two different types of parenchymal cells. The intestinal species, E. trivolvis had mitochondria in the basal aspect of the tegument, and some variations in enzyme activity of their mitochondria in the tegumental and parenchymal cells were observed, suggesting that they possess both aerobic and anaerobic metabolic systems. Z. lunata that live in rodent caeca are devoid of mitochondria in the tegument and have many characteristic mitochondria with undeveloped cristae in the parenchymal cells. Mitochondria of F. gigantica showed weak or no activity for cytochrome c oxidase, suggesting that the worm is well-adapted to an anaerobic environment in the host bile duct.

The metacercaria of the heterophyid digenean Cryptocotyle concavum (Creplin, 1825) Lühe 1899, as seen by light and transmission electron microscopy, from the common goby (Pomatoschistus microps) is enclosed within a rigid cyst wall composed of four layers of parasite origin surrounded by a host-derived capsule. The encysted parasite contains anterior glands with secretion-filled ducts opening at the anterior extremity of the ‘head’. Excystment in vitro occurred most readily at 40–42°C on treatment with alkaline bile salts following pretreatment with acid pepsin. After 1 min in pepsin, the metacercaria became intermittently active, periods of rotation lasting 1–3 sec alternating with quiescent periods of 20–40 sec. Metacercariae excysted, some in less than 1 min, after transfer to bile salts. The metacercaria emerged through a hole, which appeared in the cyst wall at the site of application of the ‘head’ of the parasite. Some of the anterior gland ducts of excysted metacercariae were empty, indicating that their secretions are involved in penetrating the cyst wall. Following pretreatment in acid pepsin, no excystment occurred in EBSS (Earle's balanced salt solution) ranging in pH from 2.0 to 4.0, but above pH 4.0, excystment increased, reaching a maximum between pH 7.5 and 8.5. Pepsin and bile salts were not essential for excystment and metacercariae emerged, although less readily, in alkaline EBSS with or without acid EBSS pretreatment. Some emerged in distilled water with no pretreatment. Although no excystment occurred in acid pepsin or in EBSS at pH 2.0 and already-excysted metacercariae were rapidly killed by acid (pH 2.0), acid pepsin pretreatment enhanced excystment in alkaline bile salts.

For the first time the development of the excretory system Levinseniella brachysoma metacercariae (Trematoda: Microphallidae) obtained experimentally from Gammarus oceanicus has been described. The bladder wall of 8-day post-infection (P.I.) larvae consists of a syncytium covered with microvilli. Its cytoplasm contains well-developed rough endoplasmic reticulum (RER), free ribosomes, small oval dense mitochondria and numerous large membrane-bounded (about 5 μm in diameter) spherical granules. Later the size of the excretory bladder and the number of nuclei and RER cisternae increases. The large spherical granules disappear completely but spherical dense bodies (up to 4 μm in diameter) devoid of limiting membranes appear. The bladder lining forms thick columnar projections directed towards its lumen. Accumulations of microlamelli occur only on the lumen surface between adjacent projections. By the 42nd day P.I. the bladder wall has two separate components: the columnar projections and the syncytium between them.

Mice were infected percutaneously with cercariae of Schistosoma japonicum or S. mansoni and parasites recovered by tissue-mincing from the skin or lungs or by perfusion of the mesenteric veins. S. japonicum had a narrow peak of recovery (up to 30%) from the lungs 3 days after infection, whereas lung recovery of S. mansoni peaked only on day 6 and levelled off during the following week. Infection with S. japonicum induced lung petechiae, but only after most of the parasites had left the lungs. The axillary lymph nodes draining the infection site increased in weight after infection and this effect was much greater and longer with S. mansoni than with S. japonicum. S. japonicum was perfusable from the mesenteric veins earlier (from day 3 onwards) and in higher number (40–60% from days 6 to 10) than S. mansoni (20% on day 20). The percentage of cercariae developing to adult worms was 57% for S. japonicum and 33% for S. mansoni. The data demonstrate that S. japonicum might escape from local tissue reactions in the skin and lungs and, due to its rapid migration, might induce only poor lymphocyte proliferation. As a possible consequence, S. japonicum may establish more efficiently in mice than S. mansoni.

In order to clarify the taxonomic status of the Taenia saginata-like tapeworm in East Asia, the morphological characteristics of the adult and cysticercus of classical T. saginata (American, Swiss and Poland strains) and the Taiwan Taenia were compared in the present study. The morphologic characteristics of these two parasites are very similar. The protoscolex of cysticercus of the Taiwan Taenia has a sunken rostellum while that of classical T. saginata has only an apical pit. In addition, the rostellum of the Taiwan Taenia cysticercus is usually surrounded by two rows of rudimentary hooklets. However, this structure is rarely found in classical T. saginata. Based on the results of molecular studies and morphological characteristics, the T. saginata-like tapeworm in East Asia represents a subspecies of T. saginata, named T. saginata asiatica

Eighty three carcasses of pigs were examined at three abattoirs in Moshi, Arusha and Mbulu in northern Tanzania. Taenia solium metacestodes were found in all the three abattoirs with an overall prevalence of 13.3%. During routine meat inspection in Kiboroloni, Moshi 6.2–6.9% of the pigs were found to harbour T. solium metacestodes. The mean number of hooks on the protoscolices was 27 and the length of the small hooks varied from 105 mm to 130 μm while that of the larger hooks varied from 168 mm to 174 mm confirming that the cysts were metacestodes of T. solium. Although cystlike lesions were recovered from livers of both pigs and cattle, no booklets of sizes in the range of 5–37mm were found indicating that no Taiwan Taenia metacestodes were recovered during carcass examination.

Entomopathogenic nematodes were isolated from soil samples collected during three separate surveys, two in the United Kingdom and one in the Netherlands. The nematodes were identified by their restriction fragment length polymorphisms on hybridization of Southern blots with a ribosomal DNA repeat unit clone. A total of eight steinernematid species/RFLP types and two heterorhabditids were isolated. The distributions of the majority of these species/RFLP types were significantly different between the three surveys and some of the species displayed a close association with certain habitat types.

Nematodes identified as Spirura rytipleurites seurati are described and illustrated by light and scanning electron microscopy from specimens collected from the stomach of hedgehogs (Erinaceus europaeus) in Sicily. They differ from S. auriti, a stomach parasite of Hemiechinus auritus, in the length of body, the position of the second pair of post-cloacal papillae in the male and the structure of the spicules. The nematodes are classified as S. rytipleurites seurati, a stomach parasite of Erinaceus algirus, but they differ slightly from it in the dimensions of the eggs, that we measured in the uterus, and in the shape of the amphids. This appears to be the first report of S. rytipleurites seurati from Italy and from E. europaeus.

The parasite burden in the liver and peritoneal cavity and antibody levels directed to whole worm extract, have been monitored in serum from ICR-strain mice, infected orally with 55 tetrathyridia of Mesocestoides corti (Cestoda, Cyclophyllidea). The subcurative doses (3x or 6x) of praziquantel (PZQ) (10 mg.kg−1 body weight) were administered to mice from day 14 post infection (p.i.) in two drug formulations: as PZQ suspended in Dorfman vehicle, or as PZQ incorporated in liposomes (lip.PZQ). The appearance of antibodies was time-dependent and correlated with the rate of reduction in numbers of tetrathyridia. PZQ in three and six doses caused the highest fall of parasite numbers in the liver on day 1 post therapy (p.t.). In the peritoneal cavity, a similar reduction in worm burden occurred but only after six doses of the drug. The worm count in the peritoneal cavity from groups of mice injected with lip.PZQ decreased most markedly on day 7 p.t., in the group treated with six doses of the drug. In the liver, the highest larvicidal effect, compared with the controls, was observed 6 days later (i.e. day 13 p.t.), following three doses of lip.PZQ. In all treated groups, two peak values of antitetrathyridial antibody levels were detected between days 1 and 13 p.t. (i.e. days 17 to 29 p.i.), after which there was a gradual but continuous increase in antibody titre. After treatment with six doses of both drug formulations (PZQ and lip.PZQ), the occurrence of the first maximum and minimum of antibody serum levels was delayed 6 days, compared to those groups treated with three doses of the drugs. Empty liposomes had some immunomodulatory effect on the antibody response, with significant decrease in antibody titres after three doses over the experimental period, but not after six doses.

Cross-resistance between Strongyloides venezuelensis and S. ratti was tested in mice. The mice were immunized with S. ratti and challenged with infective filariform larvae or larvae recovered from the lungs of mice, of a heterologous species, S. venezuelensis. In this system, cross-resistance was expressed to the intestinal stage but not to the migrating stage of the parasite. Anti-interleukin (IL)-5 monoclonal antibody (mAb) treatment showed that peripheral blood eosinophilia after infection with both species of the genus Strongyloides was dependent on IL-5. Cross-resistance expressed to the intestinal stages was inhibited partially by injection of anti-IL-5 mAb.