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At least 19 recordsLinked to original sources

Tick paralysis in Brazil.

From July to December 1977 and from June to November 1978 the toxic effects of Amblyomma cajennense were studied in cattle sheep and goats. Locomotor disturbances commencing as hind-limb paralysis ascended to the upper nervous centres causing paralysis. This was observed in natural infections and confirmed experimentally. Tick paralysis is reported for the first time in Brazil, manifesting itself in a different form to that usually attributed clinically to the disease. Also for the first time reference is made to tick paralysis induced by all developmental stages of A. cajennense.

Animals

Pyrexia in response to Rhipicephalus appendiculatus infestation in calves.

Bos taurus calves free from tick-borne diseases were prophylactically treated with oxytetracycline hydrochloride and phenamidine isothionate 40% (w/v) injections and infested twice with adult Rhipicephalus appendiculatus ticks. Mono- and diphasic temperature rises were observed during primary and secondary exposures respectively with the peak occurring when the ticks were completing engorgement. However, the first rise in the secondary infestation occurred well before repletion and was associated with a hypersensitivity state. The feeding performance, viability and fecundity of female ticks were impaired during the secondary exposure.

Amidines

Improved toxin/antitoxin assays for studies on the Australian paralysis tick Ixodes holocyclus.

Sensitive biological assays of toxin/antitoxin potency have been developed to assist in research on characterization of salivary toxins of the Australian paralysis tick Ixodes holocyclus and on immunity to tick paralysis. The toxin assay utilizes suckling mice (4-5 g); a quantitative paralysis index is applied over a range of doses. The antitoxin assay is based on an in vitro/in vivo neutralization test which required a sensitive toxin assay and methods of standardization of toxin preparations. This assay permits the monitoring of blood antibody levels in animals during the course of development and loss of immunity and is assisting a study into the feasibility of producing an anti-paralysis vaccine. The method also allows standardization of commercial tick paralysis antiserum. The methods and applications are described and comparisons made with previous assays. Sample data are examined statistically by regression and variance analyses; parallelism of dosage-response lines is tested and relative toxicities (toxin) or potencies (antiserum) calculated.

Analysis of Variance

Immunization of rabbits to produce high serum titres of neutralizing antibodies and immunity to the paralyzing toxin of Ixodes holocyclus.

Rabbits have been immunized against the effects of the paralyzing toxin of the Australian paralysis tick Ixodes holocyclus by injecting them with preparations extracted from tick salivary glands. Immunized rabbits were able to withstand doses of toxin known to kill unimmunized rabbits. Neutralizing antibodies were detectable in serum after 2-4 doses of the crude extract or of the relatively pure antigenic fraction. When injections were continued at intervals of from 2-7 weeks, hyperimmunity was retained for at least 68 weeks. Hyperimmune serum, reaching a very high titre of neutralizing antibodies, was obtained after 3-6 injections. Titres tended to decline when boosting ceased, but after a "rest period' high titres were restored by further boosting with normally lethal doses of toxin. No symptoms of tick paralysis developed despite low titres prior to boosting. Thus, once hyperimmunity had been established, high titres of circulating antibodies were not immediately essential for immunity to tick paralysis. An IgG fraction was obtained from rabbit serum using a Protein A-Sepharose method; 33.4 micrograms of IgG protein fully neutralized, and 19.5 micrograms IgG half neutralized, 1 micrograms of crude toxin protein. This procedure with rabbits may permit the production of a purified tick-paralysis antitoxin more suitable for human use than the existing antitoxin based on canine hyperimmune serum.

Animals

Tick-paralysis toxoid: an effective immunizing agent against the toxin of Ixodes holocyclus.

Glutaraldehyde treatment of the toxin of the Australian paralysis tick Ixodes holocyclus produced a potent, immunogenic toxoid. Three subcutaneous injections (2 to 4 weeks apart) into rabbits produced very high antitoxin titres in their serum, although circulating antitoxin titres declined in the absence of stimulation. Twenty weeks later, immunized rabbits were unaffected by lethal doses of toxin injected subcutaneously.

Animals

Cattle and the paralysis tick Ixodes holocyclus.

Paralysis of domestic stock by the paralysis tick Ixodes holocyclus is chiefly a disease of young animals (especially calves) and of non-habituated stock introduced into tick-infested country in spring. The tick has a wide host range, but its principal hosts are bandicoots. The tick has one generation per year and the adult female, which causes almost all paralysis, is abundant in spring and early summer and occurs most commonly in overgrown or regrowth country where bandicoots are abundant. The distribution and behavior of the long and the short-nosed bandicoots are reviewed. The number of ticks required to induce paralysis in cattle and the protection from paralysis afforded by prior experience of the tick are discussed.

Animals