Biomedical subjects

D B Copeman

Publications and source records attributed to D B Copeman.

At least 37 records · Page 2Linked to original sources

PubMed2000

Surveys in Papua New Guinea to detect the presence of Trypanosoma evansi infection.

OBJECTIVE: To confirm serological evidence that Trypanosoma evansi is present in Papua New Guinea. DESIGN: Three surveys were undertaken in PNG during 1997/1998. Animals were selected for sampling on the basis of convenience. Samples of blood were examined for the presence of T evansi by the haematocrit centrifugation technique (HCT) and mouse inoculation test (MI). Sera were tested in the field using the card agglutination test for trypanosomiasis/T evansi (CATT). Bovine sera were tested at James Cook University using an antibody-detection ELISA (Ab-ELISA). Results from testing bovine sera with the Ab-ELISA and sera from wallabies with the CATT were analysed using FreeCalc to determine the probability that animals in these populations were infected with T evansi. RESULTS: A total of 545 serum samples were collected, during the three surveys of which 39 cattle, two pig and three agile wallaby samples were positive with the CATT. All bovine sera collected were negative when tested with an Ab-ELISA. T evansi was not isolated using the HCT or the MI from any of these animals. CONCLUSION: Based on the Ab-ELISA results it was concluded that T evansi infection was not present in cattle in villages around Balimo at a minimum expected prevalence of 10% (P < 0.05) and, based on the CATT results, that infection was not present in wallabies on the Bula plain at a minimum expected prevalence of 10% (P < 0.1). These results indicate that it is unlikely that T evansi is endemic in PNG.

Agglutination Tests↗

PubMed1997

A comparison of two antigen-detection ELISA for detecting infection of Dirofilaria immitis in dogs.

A survey on 87 dogs necropsied in the Townsville region revealed 34 (39%) were infected with Dirofilaria immitis. Infected dogs had an average of 6.1 adult worms in the heart and associated blood vessels. The VetRED assay detected 23 of the 34 infected dogs (sensitivity 65%) and the Og4C3 ELISA detected 27 (sensitivity 80%). Sensitivity of the VetRED and Og4C3 ELISA increased to 88 and 94% respectively in dogs with three or more worms. Both tests detected correctly all uninfected dogs. Despite the higher accuracy of the Og4C3 ELISA, compared to the VetRED assay, it is unlikely to be used widely as a field test for heartworm unless it can be modified from its present plate ELISA format which takes 4 hours, into one which is more rapid and convenient. However, as a reference ELISA, it may well be worthwhile in situations which require considerable accuracy for detecting D. immitis infection.

Animals↗

PubMed1996

Do excretory-secretory products of Onchocerca gibsoni contain phosphorylcholine attached to O-type glycans?

Excretory-secretory products (ES) of adult male Onchocerca gibsoni contain phosphorylcholine (PC). PC-ES are detected as a smear of M(r) approximately 60- approximately 200 kDa by western blotting employing a monoclonal antibody (mAb) against PC, suggesting that they are glycoproteins. Exposure of PC-ES to N-glycosidase F results in weak and inconsistent loss of binding of the mAb, indicating that unlike the situation with respect to ES of Acanthocheilonema viteae, PC is highly unlikely to be solely attached to N-type glycans. Conversely, treatment of O. gibsoni PC-ES with mild alkali, a strategy for removing O-type glycans, abolishes mAb binding. These results suggest that PC may be attached to O. gibsoni proteins mainly via O-type glycans, and raise the possibility that filarial parasites may vary with respect to their mode of attachment of PC. The implications of this with respect to the design of inhibitors of PC attachment for use as anti-filarial drugs, are discussed.

Amidohydrolases↗

PubMed1994

Biosynthetic radiolabelling of excretions-secretions of adult male Onchocerca gibsoni.

Maintenance of adult male worms of the bovine filarial parasite Onchocerca gibsoni in vitro, in the presence of radioactive precursors, resulted in the time-dependent excretion-secretion of radiolabelled parasite macromolecules (ES). Molecules labelled with amino acids ([35S] methionine, [3H] leucine) covered a wide range of molecular weights, whereas labelling with [3H] glucosamine produced predominantly molecules of high molecular weight. Many of the products were recognized by antibodies in two serum pools from humans infected with Onchocerca volvulus. O. gibsoni ES may therefore provide a substitute source of material for studies on the ES of the less readily available human parasite.

Animals↗

PubMed1994

Identification and characterisation of a novel repetitive antigen from Onchocerca spp.

A novel repetitive antigen from the cattle parasite Onchocerca gibsoni was shown to be recognised by sera from humans infected with Onchocerca volvulus, Wuchereria bancroftii or Brugia malayi. The O. gibsoni protein was produced in a recombinant form, and antibodies raised to this protein used to screen cDNA libraries for O. volvulus. A series of clones were isolated which encoded repetitive regions very similar to those in O. gibsoni, but interspersed between these were longer repeating units which we have not so far found in O. gibsoni. The repetitive antigen was shown to be of high molecular weight and present only in the insoluble (membrane) fraction of O. gibsoni microfilariae. Immunofluorescence techniques demonstrated that the antigen was associated both with muscle and with specific membrane layers, including a peripheral layer which corresponds to either the outer hypodermis or an inner region of the cuticle in adult female O. gibsoni. In many respects, the proteins encoded by the O. gibsoni and O. volvulus cDNA clones resembled repetitive antigens from several distantly related eukaryotic parasites, and a possible common role in immune evasion is discussed.

Amino Acid Sequence↗

PubMed1993

Molecular variation in Onchocerca spp.

Over the past two decades there has been an upsurge of interest in defining morphological, immunological, biochemical, biological and genetic differences between species of Onchocerca to provide solutions to practical problems associated with finding models and epidemiological tools to assist with control of human onchocerciasis. The information gathered has confirmed the close relationship between species of Onchocerca and provided highly sensitive and specific probes to distinguish species and even strains of the same species. It has also identified pathways, especially using sequences from common DNA repeat units, that may lead to a better understanding of the progression of divergence of species of this genus than has previously been possible.

Animals↗

PubMed1991

Surface antigens of male worms and microfilariae of Onchocerca gibsoni.

Living adult males and microfilariae of the cattle filarial parasite Onchocerca gibsoni were externally labelled with radioactive iodine using the iodogen and Bolton-Hunter procedures. Characterization of labelled surface proteins by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis revealed clear cut differences in the two life cycle stages. In addition, the two radiolabelling procedures yielded some differences in the profiles of radiolabelled surface proteins for both adults and microfilariae. Immunoprecipitation analysis revealed a number of labelled antigens recognized by antibodies in human onchocerciasis serum pools, thereby demonstrating the usefulness of O. gibsoni as a model in Onchocerca volvulus vaccine studies. The reactivity of microfilarial antigens extended to antibodies from other human nematode infections, whereas male surface antigens, particularly those of low molecular weight, were Onchocerca specific. This indicates that O. gibsoni can provide a convenient source of specific diagnostic antigen.

Animals↗

PubMed1991

Comparative pathological study of hepatic changes induced by Fasciola gigantica and Gigantocotyle explanatum in Javanese thin-tailed sheep.

Pathological changes in the liver induced by Fasciola gigantica and Gigantocotyle explanatum were readily distinguishable from each other. Lesions associated with the migration of immature flukes through the parenchyma were a prominent feature of infection with Fasciola gigantica, whereas lesions induced by Gigantocotyle explanatum were confined to the large bile ducts. The size of the hepatic lesions increased during the course of infection with Fasciola gigantica and was associated with the formation of progressively larger areas of scar tissue in the parenchymal migration tracts as the flukes grew. This was also as a result of the progressively increasing cellular infiltration, proliferation of bile ductules and fibrosis which occurred in adjacent portal triads and interlobular septa. The absence of signs of migration through the hepatic parenchyma by Gigantocotyle explanatum, was regarded as evidence that these flukes gain entry to the bile ducts from the intestine via the common bile duct. In bile ducts infected with Fasciola gigantica there was more extensive desquamation of the epithelium, more intense mucosal infiltration with lymphoid cells and fewer eosinophils, less severe glandular hyperplasia, more free blood in the lumen and a thicker duct wall than in bile ducts infected with Gigantocotyle explanatum.

Animals↗

PubMed1991

Antigen detection ELISAs: pretreatment of serum to reduce interference by specific host antibodies.

The pretreatment of serum to reduce interference by specific host antibodies was investigated as a means of improving the sensitivity of antigen detection ELISAs whilst screening serum samples. Four antigen detection assays based on monoclonal antibodies directed against antigens of the bovine filariid Onchocerca gibsoni were used in this study and, of these, three assays suffered a dramatic drop in sensitivity when detecting male O. gibsoni antigen in the presence of bovine serum as compared with antigen in buffer. A number of methods for pretreating serum to eliminate the problem of antibody interference with antigen detection were attempted, including heat and alkali treatments, detergent treatment of heat treated samples and the use of a reducing agent. The pretreatment of serum by boiling for 5 minutes in the presence of an equal volume of 0.1 M Na2EDTA pH 4.0 and recovery of the supernatant fluid following centrifugation at 16000 g was the most effective method of restoring the sensitivity of each of these three assays whilst screening bovine serum. Pretreatment of serum using this method produced up to a 512-fold increase in sensitivity compared with results obtained in assays with non-treated serum.

Animals↗

PubMed1991

The use of monoclonal antibody-based ELISAs to monitor chemotherapeutic effects in the bovine-Onchocerca gibsoni drug screen.

Three monoclonal antibodies directed towards antigens of Onchocerca gibsoni were used in antigen detection ELISAs to detect parasite antigens in sera from 100 cattle infected with O. gibsoni, in trials with the filaricidal compounds CGP 6140, CGP 20309, CGP 20376, CGP 21833, CGP 24589 and CGP 26702. Measurable levels of parasite antigens were highly variable, both within and between treatment and control groups of animals, with no consistent trends which related to time after treatment, micro or macrofilaricidal effects against O. gibsoni, or dose rate for any of the compounds used. It was concluded that these assays were unsuitable as a method of identifying drug-induced damage to O. gibsoni following the administration of these compounds. A detailed protocol for selecting suitable assays is discussed.

Animals↗

PubMed1991

The use of monoclonal antibody-based ELISAs to monitor the efficacy of drugs against male Onchocerca gibsoni in vitro.

Four monoclonal antibodies directed against antigens of Onchocerca gibsoni were used in antigen detection ELISAs to monitor the efficacy of CGP 20309, CGP 20376, CGP 21833, CGP 24589 and CGP 26702 at 5 micrograms/ml against male O. gibsoni in vitro. No significant differences (P less than 0.05) in antigen output between treated and control groups of parasites were recorded. However, consistently higher levels of antigen from treated (CGP 21833) as compared to control parasites were measured with all four assays, with differences being higher in the first 2 to 3 days post treatment than subsequently. The sensitivity of comparisons between groups was reduced by the high variability in output of antigen both between worms and also from the same worm, in part as a result of mechanical damage to worms sustained during collection or manipulation in vitro. This problem was reduced by zero handling once worms were established in vitro and it is recommended that future work should include a 24 to 48 hour period before treatment commences to detect raised antigen levels associated with physically damaged parasites so they can be excluded. It was concluded that this type of assay has no intrinsic technical or logistical advantage over other published methods of assessing drug-related damage in in vitro filarial screens. Nevertheless, further work using antigen detection ELISAs in this context is justified since these assays, unlike all other methods of assessing drug-induced damage in vitro, have direct application for use in identifying chemotherapeutic effects against similar parasites in vivo.

Animals↗

PubMed1990

High resistance to experimental infection with Fasciola gigantica in Javanese thin-tailed sheep.

Innate resistance of Javanese thin-tailed sheep to Fasciola gigantica was investigated in animals infected with single doses of 150 or 500 metacercariae and killed 4, 8, 12 or 16 weeks after infection. Infected and non-infected sheep had similar values for packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin concentration, serum glutamate dehydrogenase, serum gamma glutamyl transferase and serum aspartate transferase throughout the trial, except for one animal infected with 500 metacercariae from which the highest recovery of flukes (55) was made. This animal developed pathologically altered values from 12 weeks post infection, coincident with the period of greatest hepatic haemorrhage and destruction of hepatic tissue by migrating flukes and their entry into bile ducts. However, values were altered much less than those reported in other sheep given as few as 200 metacercaria of F. gigantica. Both susceptibility to infection with F. gigantica, as indicated by percentage take of metacercariae and the severity of pathological changes were low in this study in comparison with reports involving other breeds of sheep infected with this parasite. These findings support the conclusion that Javanese thin-tailed sheep have a high innate resistance to F. gigantica.

Animals↗

PubMed1990

A highly specific and sensitive monoclonal antibody-based ELISA for the detection of circulating antigen in bancroftian filariasis.

A monoclonal antibody, Og4C3, directed against antigens of Onchocerca gibsoni (but not phosphorylcholine) has been used in a sandwich ELISA to detect a circulating antigen of Wuchereria bancrofti in human serum. The interfering effect of host antibody was reduced by first boiling one part of serum for 5 min in the presence of three parts of 0.1 M Na2EDTA, pH 4.0. A total of 119 sera from individuals and 8 pooled sera from clinically and/or parasitologically defined cases of filariasis, plus 8 individual and 1 pooled endemic control sera, all from the filariasis serum bank of the World Health Organisation, as well as 20 non-endemic control sera, were screened with the assay. Circulating antigen was detected in serum from people infected with W. bancrofti but not Brugia malayi. B. timori, O. volvulus or Loa loa, and not in endemic or non-endemic controls. Of the 68 sera from W. bancrofti-infected subjects, 55/55 parasitologically confirmed and 12/13 clinically confirmed but amicrofilaraemic cases reacted in the assay. A weak but significant correlation (r2 = 0.4016) was found between numbers of microfilariae in blood and detectable levels of circulating antigen from patients with bancroftian filariasis.

Animals↗

PubMed1989

Distribution of Onchocerca spp. microfilariae in the dermis of cattle.

A grid was drawn on a lateral half of 10 hides, from cattle infected with both Onchocerca gutturosa and Onchocerca lienalis, which were obtained from an abattoir in central Florida. Paired 7-mm diameter skin cores were taken from 24 grid sites on each hide and microfilariae (mff) extracted to determine their distribution. The only consistent pattern distribution was that mff were recovered from all 10 hides at four sample sites along the ventral midline near the umbilicus. Microfilariae were also frequently found in large numbers along the dorsal cervical midline and in the region of the tarsal and carpal-metacarpal joints.

Abattoirs↗

PubMed1989

Inhibited development of trichostrongylid worms in grazing cattle.

Inhibition of development of gastro-intestinal trichostrongylid worms was studied using successive groups of tracer calves and groups of continuously grazed calves over one year in the Tully area of North Queensland lowland wet tropics. The results, assessed by means of worms from these calves recovered at necropsy 3 weeks after their removal from pastures, showed inhibition in the development of Haemonchus placei and Cooperia punctata at the early fourth stage at the approach to and during the relatively dry period in the area. Inhibition was however minor and inhibited larvae formed but only a small percentage of worm burdens in both categories of calves, indicating that they were not in any way of major epidemiological importance. It was suggested that the minor nature of inhibition was due to the mild climatic conditions which could not produce appropriate conditioning treatment, or caused only mild selection pressure for inhibition in the area.

Animals↗

PubMed1989

Onchocerca gutturosa and Onchocerca lienalis in cattle: variation in length of microfilariae by site of recovery.

Dermal microfilariae recovered from specimens obtained from umbilical and cervical sites of cattle infected with adult Onchocerca gutturosa alone or with adults of O gutturosa and O lienalis were measured and compared with uterine microfilariae obtained directly from gravid female worms of each species. Uterine microfilariae of O gutturosa were longer than dermal microfilariae obtained from cattle harboring only adults of O gutturosa. Dermal microfilariae were recovered from umbilical and cervical sites in these cattle. Those found at the cervical site had lengths equal to or greater than lengths of microfilariae recovered from the umbilical site. There was a significant (P less than 0.0001) shift in length across populations of microfilariae of O gutturosa from various sites in its bovine host, with a progressive decrease in length between microfilariae recovered from the worm's uterus, microfilariae from the cervical dermis, and microfilariae from the umbilical dermis, respectively. A similar direct comparison was not possible for microfilariae of O lienalis, because none of the cattle was infected with only adult worms of this species. In an indirect comparison, microfilariae of O lienalis were identified at the umbilicus, but their presence in the cervical region could not be determined unequivocally because of confounding of microfilariae length by concurrent infection with O gutturosa. Uterine microfilariae from O lienalis were longer than uterine microfilariae of O gutturosa, although a degree of overlap in the range of measurements existed between species.

Algorithms↗

PubMed1988

Abundance and survival of infective larvae of the cattle nematodes Cooperia punctata, Haemonchus placei and Oesophagostomum radiatum from faecal pats in a wet tropical climate.

Observations were made on the abundance and survival of Haemonchus placei, Cooperia punctata and Oesophagostomum radiatum infective larvae from cattle faecal pats exposed at various times of the year in north Queensland wet tropics. Pats exposed in the hot, wet season yielded abundant larvae on herbage. In the dry season, although low numbers of infective larvae were usual, considerable numbers were produced under conditions of heavy dews on dense herbage. Irrespective of season of deposition of pats, the resulting larvae persisted generally for not longer than 10 to 12 weeks, and in large numbers for only 2 to 6 weeks. The findings suggest that prevention of contamination in the wet season, and in the dry season when light rainfalls are accompanied by heavy dews on dense herbage, will result in low levels of larval infestation on herbage. Rotational grazing in the area is suggested as a means of worm control.

Animals↗

PubMed1988

The fine structure of male and female Onchocerca gibsoni.

The fine structures of the midbody regions of male and female Onchocerca gibsoni are described. The epicuticle is wrinkled in the male, and forms long protuberances in the female worm. The lateral chords of the female specimens contain many bacteria and dense bodies. In both sexes the intestinal cells are filled with concentric spherules and the intestinal lumen is extremely reduced. The fine structures of O. gibsoni are very similar to those of O. volvulus.

Animals↗