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Biomedical subjects

D L Obendorf

Publications and source records attributed to D L Obendorf.

At least 37 records · Page 2Linked to original sources
PubMed1988

Evaluation of a serological test system for the diagnosis of natural Echinococcus granulosus infection in dogs using E. granulosus protoscolex and oncosphere antigens.

Serum antibody responses in feral or domesticated dogs naturally infected with Echinococcus granulosus or/and other common helminths were examined in an enzyme-linked immunosorbent assay (ELISA) using antigens prepared from E. granulosus protoscoleces or oncospheres. The ELISA using the protoscolex antigen was optimised with serums from experimental dogs monospecifically infected with E. granulosus or other helminth parasites, and helminth-free dogs. Anti-protoscolex antibody was detected in 16 of 22 (72.7%) serums from feral dogs with E. granulosus burdens ranging from 300 to 302,600 worms per dog. Seven serums from feral dogs which did not harbour E. granulosus at autopsy but which originated from an endemic hydatid region were tested using protoscolex antigen, and 1 serum gave a positive reaction. One hundred and two serums from dogs known never to have been infected with E. granulosus all gave negative reactions to protoscolex antigen. The sensitivity of the ELISA test proved to be superior to that which has been achieved by arecoline purging as a method of diagnosis for E. granulosus infection in dogs. For use of the assay in hydatid control or eradication campaigns, its sensitivity can be increased by choosing a lower absorbance discrimination value above which serums are regarded as having positive reactions. However, this does introduce positive reactions of some serums from dogs infected with helminths other than E. granulosus. In further development of the assay, use of defined recombinant antigens may improve both sensitivity and specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1987

Sarcocystis mucosa (Blanchard 1885) Labbé 1889 in unadorned rock wallabies (Petrogale assimilis) and Bennett's wallabies (Macropus rufogriseus).

Macroscopic cysts of a protozoan parasite were detected in the gastro-intestinal walls of two unadorned rock wallabies (Petrogale assimilis) and 20 Bennett's wallabies (Macropus rufogriseus). The cysts were located predominantly in the muscularis externa and the submucosa of the forestomach, small intestine and colon and sometimes in the muscularis externa of the oesophagus and caecum. All cysts exhibited similar morphological and ultrastructural characteristics. They were bounded by thick primary cyst walls (containing distinctive bulbous-like protrusions) and were surrounded by collagen fibres and host connective tissue cells (mainly fibrocytes). The cysts were divided by septae into internal compartments containing metrocytes and cystozoites. The cystozoites contained numerous organelles typical of apicomplexan protozoan parasites (including an apical complex, a micropore, rhoptries, micronemes, polysaccharide granules and 22 subpellicular microtubules) and they were observed to divide by the process of endodyogeny. Despite the unusual location of the cysts, they were classified on the basis of their ultrastructural characteristics as Sarcocystis mucosa (Blanchard 1885) Labbé 1889.

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PubMed1987

Experimental infection with Sarcocystis medusiformis in sheep.

The development of the parasite was studied in 48 sheep killed between 188 and 1132 days after experimental inoculation with Sarcocystis medusiformis sporocysts from cats. Immature sarcocysts were present at 188 days post inoculation (d.p.i.). At 331 d.p.i. macroscopic sarcocysts with an elongate fusiform appearance were seen in the laryngeal, abdominal and diaphragm musculature. The largest cyst measured 2 mm in length by 0.5 mm in width at 331 d.p.i.; histologically they contained metrocytes at the periphery of the cyst with more densely staining merozoites in the central region. By 443 d.p.i. typical 'thin' cysts 2-3.5 mm in length were seen in the flank and external thoracic muscles. By 765 d.p.i. sarcocysts were 5 mm in length. The ultrastructure of the cyst wall of these cysts resembled that of S. medusiformis. At 1132 d.p.i. sarcocysts measured 4 mm X 0.5 mm.

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PubMed1986

Demonstration of schizogonous stages of Sarcocystis gigantea in experimentally infected sheep.

Sarcocystis-free lambs were orally dosed with 1 X 10(6) sporocysts of Sarcocystis gigantea. Schizonts were found in endothelial cells of capillaries and arterioles of the brain, lung and kidney of lambs 7 and 14 days post-inoculation (d.p.i.). Between 21 and 35 d.p.i. there was extensive multi-focal encephalitis; however no organisms were detected in association with these lesions.

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PubMed1986

Resistance of Trichostrongylus colubriformis to levamisole and morantel: differences in relation to selection history.

Two field strains of Trichostrongylus colubriformis were tested by in vitro and in vivo methods for resistance to morantel, levamisole and thiabendazole and compared with an anthelmintic-naive laboratory-passaged strain (McM). One field strain (TAS) was isolated from a dairy goat herd which had experienced severe helminthiasis despite intensive anthelmintic usage. The other (BCK) was isolated from sheep which had been treated solely with levamisole over a 6-year period. The BCK strain had very high levels of both levamisole and morantel resistance. In contrast the TAS strain was resistant to morantel but highly susceptible to levamisole. This finding is contrary to the expectation that selection with morantel automatically confers resistance to levamisole, the converse of which was shown to apply in the BCK strain. Although the TAS strain was exposed to levamisole prior to isolation, examination of the drug's pharmacokinetics in goats indicated that it exerted little if any anthelmintic effect, and therefore selection pressure, on the parasite population. This study suggests that the mechanism of levamisole resistance covers a wide spectrum, and embraces that for morantel. It also suggests that in order to conserve the effectiveness of the levamisole/morantel group of broad spectrum anthelmintics, morantel should be used to the exclusion of levamisole until resistance is detected, at which time levamisole may be introduced to re-establish high levels of control.

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PubMed1984

Morphology of Sarcocystis gigantea in experimentally-infected sheep.

The development of the parasite and lesions was studied in 32 sheep killed 10 days to 47 months after inoculation with Sarcocystis gigantea sporocysts from cats. At 21-42 days post-inoculation (d.p.i.), there was a mild encephalitis, but organisms were not seen in the brain. Immature sarcocysts were detected from 40-84 d.p.i. The cyst wall was not measurable by light microscopy at 40 d.p.i., but was 1.5-2 microns thick at 84 d.p.i. At 119 d.p.i. both immature cysts containing only metrocytes, and mature cysts containing both metrocytes and merozoites, were present. These mature cysts did not have a secondary cyst wall. A mature cyst, 350 microns in length, was found in a sheep killed at 8 1/2 months p.i. At 10 m.p.i. cysts were up to 0.5 mm long and a secondary cyst wall was present. At 47 m.p.i. cysts were 2-5 X 4.5-7.5 mm, and were found only in the muscles of tongue, oesophagus, pharynx and flank.

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PubMed1984

Development and growth of Sarcocystis gigantea in experimentally-infected sheep.

Immature, microscopic Sarcocystis gigantea sarcocysts were detected in experimental sheep from 1.3 to 4 months after dosing with sporocysts from cats. Mature, microscopic sarcocysts were also present at 4 months post-inoculation (p.i.). S. gigantea sarcocysts were 0.35 mm long at 8.5 months p.i. and gradually increased in size to 7.5 mm by 45 months p.i. Transmission back to cats was demonstrated at 14 months p.i.

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PubMed1984

Serological diagnosis of Echinococcus granulosus infection in sheep using cyst fluid antigen processed by antibody affinity chromatography.

Serum antibody responses in sheep naturally or experimentally infected with Echinococcus granulosus and/or other larval cestodes were examined using an enzyme-linked immunosorbent assay (ELISA) with various antigens prepared from sheep hydatid cyst fluid ( SHCF ). Serum donors included: sheep experimentally infected with E. granulosus and their age-matched non-infected controls; sheep experimentally infected with other helminth parasites; sheep naturally infected with E. granulosus both from Tasmania and the Australian mainland; sheep from Tasmania naturally infected with larval cestodes other than E. granulosus; and naturally reared sheep completely free from infection with larval cestodes. Attempts were made to eliminate serological reactions which were not specific for E. granulosus by using a series of antibody affinity chromatography steps to deplete crude SHCF antigen; these included adsorption with a monoclonal antibody, 3EgH 29-2, removal of host IgG using rabbit anti-sheep IgG antibody, and removal of antigens which bound non-specifically to normal sheep immunoglobulin. The final affinity-depleted antigen product was designated AD SHCF . Specific serological reactivity in infected sheep was very low. Affinity depletion of SHCF using 3EgH 29-2 did not appear to increase the specificity of serological diagnosis of E. granulosus infection when experimentally infected sheep were compared with their non-infected controls provided the latter were age-matched with experimental animals. The other affinity adsorption steps significantly reduced non-specific background binding to antigen by normal sheep serum. Despite this reduction in background in the ELISA, only low levels of antibody could be detected in naturally-infected sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1983

Causes of mortality and morbidity of wild koalas, Phascolarctos cinereus (Goldfuss), in Victoria, Australia.

Between 1975 and 1980, necropsy investigations were conducted on 44 wild koalas (24 males, 20 females) from several localities in Victoria, Australia. An additional 11 (5 males, 6 females) were presented for clinical appraisal and treatment. Traumatic injuries resulting from motor vehicle accidents and intra-specific conflict were the commonest reason for submission (19 of 55; 35%). Keratoconjunctivitis (8 of 55; 15%), ascending urinary tract infections (6 of 20 females; 30%), ascending genital tract inflammation (10 of 20 females; 50%) and sarcoptic mange (2 of 55; 4%) were recognized as specific diseases or disease syndromes. A peracute syndrome characterized by lassitude, depression, anorexia and coma was identified in moribund koalas submitted from the wild and also in hospitalized animals. The condition, termed koala stress syndrome, was thought to be initiated by intercurrent disease or trauma, long term hospitalization and frequent manipulation and treatments. Hematological observations in 54 apparently healthy wild koalas from five different populations and on 17 sick or injured animals are also presented. Certain blood parameters are discussed in relation to the health status of the populations or individuals. Areas for further research into koala diseases are also discussed.

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