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Biomedical subjects

D D Heath

Publications and source records attributed to D D Heath.

At least 91 records · Page 5Linked to original sources
PubMed1981

Effect of population density on growth and development of Taenia hydatigena in dogs.

Groups of puppies were infected with either one, five, 10, 20 or 40 cysticerci of Taenia hydatigena and necropsied 70 days later. The number of worms recovered from each group was proportional to the number of cysticerci fed. Individual weights of worms decreased significantly with increasing numbers. The lengths of worms and relative numbers of pregravid and gravid proglottids also decreased with increasing population density. Gravid segments were present on some worms at all population densities.

Animals↗
PubMed1981

Resistance to Echinococcus granulosus infection in lambs.

A high level of resistance of oral infection with Echinococcus granulosus eggs was stimulated in lambs by two or more subcutaneous injections of oncospheres given 14 days apart. The degree of resistance was significantly higher than that resulting from a single injection. Resistance was apparently stimulated by the activated oncosphere or a stage of cyst development prior to 14 days of age. Studies on oncospheres cultured in vitro in sera collected from animals during immunization or after oral challenge showed that most cysts were killed before 7 days of culture had elapsed. This confirmed the observation that resistance was stimulated by an early stage of cyst development. The in vitro test also showed that two injections of oncospheres resulted in a marked increase in the lethal effects of serum. These lethal effects decreased with time, providing circumstantial evidence that the high degree of resistance stimulated by two or more injections may only be transient.

Animals↗
PubMed1980

Simulating strategies for control of Echinococcus granulosus, Taenia hydatigena and T. ovis.

A deterministic model to compare various control strategies for parasites having two hosts is presented. When applied to Echinococcus granulosus, Taenia hydatigena and T. ovis, the model shows that maximum progress would be achieved when both the definitive and the intermediate host are treated simultaneously. This type of model may prove of value in studies on the control of other two-host parasites.

Animals↗
PubMed1980

Development of early larval stages of Taenia ovis in vitro using a cell monolayer.

An in vitro culture system incorporating a cell monolayer was used to induce most activated oncospheres of Taenia ovis to enter post-oncospheral development. Seven distinct developmental phases were recognized during the 23 days required for development to reach a stage similar to that achieved after 14 days in vivo. Secretions or tegumental substance were released during each developmental phase.

Animals↗
PubMed1980

An attempt to immunise dogs against Taenia hydatigena.

An attempt was made to immunise dogs against Taenia hydatigena. Worms were cultured in vitro and macromolecular secretions were collected, concentrated and injected in a water-in-oil emulsion into dogs. A high serum antibody titre to these antigens was stimulated but no immunity was induced to a challenge infection of five cysticerci. There was no change in antibody titre following acquisition of the challenge infection. Dogs varied markedly in their susceptibility to this parasite.

Animals↗
PubMed1979

The duration of passive protection against Taenia ovis larvae in lambs.

In an attempt to induce passive protection in lambs against Taenia ovis larvae that would last for the 15-20 weeks from birth to slaughter as fat lambs, one group of ewes was immunized by a series of injections of 2000, 4000, 8000, 16 000 and 32 000 activated oncospheres of Taenia ovis prior to parturition. Another group of ewes was not immunized. All ewes had previously grazed pasture lightly infected with T. ovis eggs. Most lambs from non-immunized ewes developed cysts after oral infection with T. ovis eggs. However, no lambs from immunized ewes developed cysts up to and including 6 weeks after birth. Between 8 and 16 weeks after birth a proportion of lambs were found to be susceptible to infection. By 18 weeks after birth all lambs were apparently susceptible. The 99% confidence band for the mean duration of demonstrable complement-fixing antibody titres was 6.2-7.8 weeks for lambs from immunized ewes. The persistence of maternal protective antibody in some lambs could possibly preclude successful active immunization of all lambs against T. ovis larvae before 18 weeks of age.

Animals↗
PubMed1979

'Arc 5' antibodies in sera of sheep infected with Echinococcus granulosus, Taenia hydatigena and Taenia ovis.

The 'arc 5' precipitin band, formed when test human serum is reacted against immunoelectophoresed hydatid cyst fluid antigen, has provided a positive diagnosis of Echinococcus granulosus infection. These antibodies to 'arc 5' antigen have now been found in the sera of sheep. They appear 2 weeks after infection with Taenia ovis, after 3 weeks with T. hydatigena and after 16 weeks with E. granulosus. An antigen similar to the 'arc 5' antigen of E. granulosus cyst fluid was also demonstrated in cyst fluid from T. hydatigena, but it would not be positively identified in T. ovis cyst fluid. The presence of 'arc 5' in immunoelectrophoresis tests is not suitable for specific immunodiagnosis of E. granulosus infections in sheep in New Zealand. 'Arc 5' antibodies were only associated with living E. granulosus cysts and were not present if cysts were dead. The location of the cysts in either liver or lungs and the onset of brood capsule production did not influence the presence of 'arc 5' antibodies.

Animals↗
PubMed1979

Cross-protection between the cysts of Echinococcus granulosus, Taenia hydatigena and T ovis in lambs.

Lambs were infected orally at 14 weeks of age with either Taenia hydatigena, T ovis or Echinococcus granulosus eggs. To induce high levels of resistance to oral reinfection, they were then injected intramuscularly with eggs of the homologous species four weeks and eight weeks later. The degree of immunity was then tested by oral challenge with eggs from either the homologous or an heterologous species. Autopsy results indicated that prior infection with an homologous species induced a very high degree of immunity to challenge infection. Prior infection with all combinations of heterologous species resulted in a lesser degree of immunity, which appeared to have acted on the establishment phase of development and did not influence cyst survival.

Animals↗