The induction of acquired resistance to H. polygyrus, following treatment of mice by a 6 day immunizing infection abbreviated with the anthelmintic drug ivermectin (6d I-AI), was investigated. Four worms were sufficient to elicit >80% protection against challenge and immunizing infections >50 worms generated >95% protection in female NIH mice. A few worms were recovered during the second week from immunized challenged mice but these were rapidly expelled from the gut lumen. Treatment with hydrocortisone from day 10 postinfection, permitted worm burdens to accumulate over the following 2 weeks. The 6d I-AI protocol enabled females of strains previously designated as weak responders to develop potent acquired resistance to challenge (CBA mice showed >90% protection), although weak responder strain male mice were not significantly protected. Delaying treatment with ivermectin by as little as 24 h resulted in poorer expression of acquired resistance. A positive correlation between the increasing interval from infection to treatment with ivermectin and worm burdens after challenge, and the negative correlation with IgGl antibody responses after challenge indicated that the immunodepressive activities of 7 day and older worms down-regulated local intestinal immune responses. Mice characterized by weak responder phenotype were significantly more sensitive to downregulation than mouse strains showing strong responder phenotype. In consequence, optimal timing of treatment with anthelmintics during exposure to the immunizing infection, intending to minimize exposure to the immunodepressive stages of the parasite, is sufficient to overcome reported genetic constraints on the development of resistance in this system.

Live adult and cercarial stages of Sanguinicola inermis Plehn, 1905 (Trematoda: Sanguinicolidae) were maintained in vitro in the presence of carp (Cyprinus carpio L.) leucocytes. Cells and parasites were fixed at intervals from 0.25 to 48 h and examined using light microscopy, SEM and TEM. Within 12 h of exposure, leucocytes were found attached to cercariae although, by 24 h, fewer cells were found attached to postcercarial, juvenile adult stages that had shed their tails. Neutrophils and macrophages were found attached to the damaged tegument of cercariae that had not transformed by 48 h. Few cells were attached to the tegument of adult flukes that were alive when fixed. However, there was extensive tegumental damage and numerous cells were attached to adult flukes that had died before fixation. The results are discussed with reference to parasite survival within the vascular system of the host.

Human dirofilariasis is a rare infection in Malaysia. Thus far, only two human cases have been reported viz. Dirofilaria immitis and D. (Nochtiella) repens and in both instances, adult worms were recovered from infected patients. The two cases reported in the present study, one from Melaka and the other from Penang, were diagnosed histologically. Based on the diagnostic criteria for identifying Dirofilaria in tissue sections, the parasites were identified as D. (Nochtiella) repens.

The effects of high fat diets (HFDs) on the host–parasite relationship of Echinostoma caproni in ICR mice were studied. Two HFDs were used, one consisting of a customized high fat diet (CHFD) with 45% lipid in the form of cottonseed oil, and the second consisting of an egg yolk diet (EYD) from domestic hens' eggs, with 31% lipid. Controls for both diets consisted of mice fed a standard laboratory diet with 5% lipid. Mice were each fed 25 cysts of E. caproni by stomach tube and necropsied 2, 3 and 4 weeks postinfection (PI). The weight of mice on the CHFD declined significantly compared to mice on the control diet, but there was no significant decline in weight of mice fed EYD compared to the controls. Worm recoveries from mice on both HFDs were significantly less than those from control hosts. There was a significant decline in worm dry weight, body area and uterine egg counts in worms on HFD compared to those on the control diet. Worms from hosts on HFD were located more anteriad in the gut than those recovered from mice on the control diet.

Two Norway rats, Rattus norvegicus, were found to be naturally infected with Echinococcus multilocularis in Japan. One of them was simultaneously infected with at least three different sized metacestodes of Taenia taeniaeformis. These two R. norvegicus rats and another R. norvegicus naturally infected with T. taeniaeformis and Capillaria hepatica were examined to see if they showed any antibody responses against these two cestode parasites with the view to obtaining more information on the importance of rats as the intermediate host for E. multilocularis. These R. norvegicus showed very poor antibody responses against the two cestode species, although the Wistar rats, R. rattus, experimentally infected with a single smaller sized metacestode of T. taeniaeformis showed stronger responses not only against T. taeniaeformis but also against E. multilocularis. Therefore the three R. norvegicus naturally infected with E. multilocularis and/or T. taeniaeformis demonstrated virtually no immune response, at least against these cestodes.

A sandwich antibody ELISA was employed for the detection of circulating filarial antigen in patients with bancroftian filariasis. Wuchereria bancrofti recombinant antigen-derived polyclonal and monoclonal antibodies were successfully used as the revealing antibodies and their efficiency was compared. All the microfilariae (mf) positive (by finger prick and examination of 20 μl of blood under the microscope) individuals tested showed the presence of circulating antigen(s). Among the antigen positive endemic normals (mf negative by the finger prick method), 43% showed microfilariae by a sensitive parasitological method viz. membrane filtration of the night blood samples. A significant correlation was observed between the parasite antigen levels and the blood microfilaria counts among the mf carriers. This information on the parasite antigen levels could be an ideal monitor to indicate the degree of active infection and in the follow up of chemotherapy.

A comparison was made, by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), of excretory/secretory (ES) – crude and immunopurified (with the corresponding anti-host serum) hydatid fluids – and somatic (S) – protoscoleces – proteins, from several ovine, equine, swine, bovine and human Echinococcus granulosus Spanish isolates. Likewise, the host influence on parasitic ES protein expression was studied, comparing purified hydatid fluids from ovine and equine cysts obtained from natural hosts and in RNMI mice. Purified hydatid fluids patterns, under reducing conditions, yielded the most precise differentiation of Spanish strains of E. granulosus into three groups (ovine—bovine-human, equine and swine), the finding of a characteristic 82 kDa band in equine isolates, and an unusual arrangement of bands between 50 and 6 kDa in swine samples. In addition, differences were found amongst crude and purified hydatid fluids, especially in bovine and swine isolates. The total protein patterns of protoscoleces were most complex, and therefore could not be used for strain differentiation. Finally, the purified hydatid fluids from cysts developed in natural and experimental hosts showed similar protein patterns, suggesting the lack of host influence, under our experimental conditions, on the expression of parasitic ES proteins.

The tail chamber's role in the survival and infectivity of Proterometra macrostoma (Digenea: Azygiidae) was investigated. Intact cercariae and cercarial bodies dissected from tails were incubated for 14 h in artificial pond water (APW) and cercarial infectivity was assessed in laboratory infections of the bluegill sunfish, Lepomis macrochirus. Although most cercariae stopped swimming and settled to the bottom after 14 h, survival and infectivity of bodies from intact cercariae did not decrease significantly during this period. All isolated bodies survived in APW, but they were 54% less infective. By contrast, infectivity of isolated bodies did not decrease significantly in an artificial snail saline. The results indicate that maximum infectivity in P. macrostoma is sustained throughout the swimming phase because of the tail chamber which protects the body from the effects of osmotic stress.

The cestocidal activity of Acacia auriculiformis was evaluated using rats each harbouring a single adult worm of Hymenolepis diminuta. The ethanol extract (300 mg/kg/day) and the saponins (200 mg/kg/day) obtained from the funicles of A. auriculiformis, were administered orally to two groups each of 10 rats, respectively, on day 20 after oral inoculation with a single cysticercoid of H. diminuta. Adult worms were expelled within 5 days from rats treated with the ethanol extract and within 3 days from those treated with saponins. No appreciable side effects were observed in the treated rats.

Fresh stool samples from 300 subjects presenting at out-patient clinics in two major hospitals in Port Harcourt were analysed for the prevalence and intensity of gastrointestinal (GI) nematode infections and 85.3% were found to carry at least one of the four species of GI nematodes recognized during the study. The most common species was Ascaris lumbricoides (54%), followed by Trichuris trichiura (43.7%) and Necator americanus (42.7%) and lastly Strongyloides stercoralis (33%). Peak prevalence for A. lumbricoides was among the ≤9 years age cohorts, whilst those for the remaining species all coincided among the 15–19 years age cohort. The frequencies of single, double and triple-species infection categories, across the species and within most of the specific combinations were lower than the expected frequencies calculated from overall prevalence data for each species. Observed cases of non-infected individuals and those carrying all four species were higher than expected, suggesting that a greater than expected subset of the population was free from infection, particularly among subjects ≥30 years old and another subset more prone to infection by all four species, predominantly among the age cohorts ≤29 years. N. americanus and T. trichiura were more commonly encountered among multiple species infection combinations than expected, but the intensity of the former declined as the number of other concurrently infecting species increased. In contrast, the intensity of infection with S. stercoralis increased as the number of other species increased. Positive associations between A. lumbricoides and T. trichiura, N. americanus and S. stercoralis, and T. trichiura and N. americanus were identified in respect of greater than expected co-occurrence of these combinations and significant positive correlations between their respective intensities of infection. These were related to specific age cohorts which were identified as particularly prone to multiple infections.

Sixty-eight red foxes were collected from the metropolitan area of Copenhagen and examined for helminth infections. Standard faecal flotations for intestinal parasites gave the following results: Strongyle eggs (75.0%), Capillaria eggs (36.8%), Toxocara eggs (23.5%), Taenia eggs (1.5%), and coccidia oocysts (2.9%). Gastrointestinal helminths were collected from 21 of the 68 foxes with the following specimens found: Uncinaria stenocephala (85.7%), Toxocara canis (81.0%), Taenia spp. (38.1%), Mesocestoides lineatus (23.8%) and Polymorphus spp. (9.5%). Faeces of 39 foxes were examined by the Baermann method for larvae of cardiopulmonary worms with 20 foxes (51.3%) being infected. Fourteen foxes (35.9%) were infected with Angiostrongylus vasorum, 11 (28.2%) were infected with Crenosoma vulpis, and 5 foxes (12.8%) were infected with both species. Muscle digestion of diaphragms from the 68 foxes indicated that none harboured larvae of Trichinella spiralis.

Freeze fixation-dehydration was used for the first time in the preparation of attached Gyrodactylus for SEM viewing. The technique provided instant immobilization of specimens before death and negligible shrinkage throughout the fixation-dehydration process. Comparisons of sample means of two linear measurements of attached opisthaptors showed 20% more shrinkage of Gyrodactylus fixed using 10% neutral buffered formalin than those which were freeze fixed. Freeze fixation-dehydration was excellent for the study of gross external morphology of attached Gyrodactylus. However, the freeze fixation-dehydration process may cause disruption of intracellular structural components making delicate tissues brittle and more prone to damage during subsequent manipulation.

Comparison of the numbers of Schistosoma mattheei eggs and miracidia per gram faeces in groups of naturally infected calves, heifers and adult cows showed that the reduction in faecal egg excretion recorded as infection progresses is associated with a decline in the ability of eggs to hatch. While 50% of the eggs from calves produced a miracidium, only 15% of those excreted from adult cows did the same. The decline in egg viability is at least partly associated with morphological changes of the eggs. About twice as many smaller and vacuolated eggs were found in the faeces of heifers and adult cows (33.8%) as compared to animals in early infection (16.1%).

Third-stage larvae of Angiostrongylus costaricensis were cultured to young adult stages in Waymouth's chemically defined medium MB 752/l, which comprises higher concentrations of the essential components histidine, lysine, methionine, tryptophan, choline chloride and glucose than various other chemically defined media. The present study has shown that choline chloride and tryptophan are required at relatively higher concentrations for worm development than those of the other essential components.

In order to detect intraspecies differences among isolates of Schistosoma mansoni from different geographical regions, soluble egg antigens (SEAs) of three isolates were characterized using SDS-PAGE. SEAs were prepared from eggs of a South African (SA), Eastern Caprivian (EC) and Puerto Rican (PR) isolate, separated by SDS-PAGE, stained and the molecular masses of constituent polypeptides determined. Protein profiles differed for all three isolates with the number of polypeptides varying from 25 for the PR isolate to 27 for the EC and SA isolates. Molecular masses of the polypeptides fall within the range of 12.0 kDa to 97.9 kDa. The EC and SA isolates shared ten common polypeptides, the PR and SA isolates five and the PR and EC isolates two. Only a 30.8 kDa and a 12.0 kDa polypeptide were common to all three isolates. These differences may, to some extent, account for regional variations in the morbidity of intestinal schistosomiasis reported for different geographical isolates of S. mansoni.

Two chitin synthesis inhibitors (CSIs) viz., triflumuron and hexaflumuron interfere with the development of Brugia malayi in Aedes aegypti (a black-eyed Liverpool strain). The development of B. malayi was slow in both the treated populations and the infection rate, infectivity rate and L3 load per mosquito decreased significantly (P< 0.001) in comparison with untreated controls. Hexaflumuron was found to be more inhibiting than triflumuron.