Laboratory investigations on the life-cycle of the Karoo paralysis tick (Ixodes rubicundus Neumann, 1904).
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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.
The Australian paralysis tick Ixodes holocyclus occurs along the eastern coast of Australia. Its interaction with a wide variety of hosts causes a serious toxicosis (tick paralysis) in domestic pets and livestock (occasionally in wildlife and humans) as well as hypersensitivity reactions in humans. Tick paralysis in animals is usually fatal in the absence of speedy antitoxin treatment and human hypersensitivity may result in life-threatening anaphylaxis. The protection of such hosts against toxic or allergic effects by vaccination or desensitisation respectively has been the objective of most of our recent research. The role, biosynthesis and nature of the paralysing toxin (holocyclotoxin) and of the allergens is gradually being elucidated. In this review, some emphasis has been placed on recent research on the interactions of humans with this tick and on the partial characterisation of the allergens.
Feeding under constant cold conditions resulted in a marginal shortening of feeding period and a major shortening of the subsequent developmental phase of all stages of Ixodes rubicundus Neumann 1904, the Karoo paralysis tick. Paralysis occurred in laboratory rabbits when nymphae were fed on them under constant warm, constant cold and fluctuating ambient winter conditions. This paralysis was found to be dependent on infestation rate and feeding conditions. Under constant cold conditions paralysis resulted from lower levels of infestation than under warm or under fluctuating winter conditions. Neurological parameters used in assessing the progression of the paresis are discussed.
Three beagle dogs were immunised against the paralysing effects of holocyclotoxin, using toxic extracts derived from salivary glands of the Australian paralysis tick, Ixodes holocyclus. Upon subsequent challenge with four ED50's of toxin the animals were completely immune, whereas during the early stages 2 of 3 dogs became paralysed after injection with 0.5 ED50. Three immunised beagles, on which 15 I. holocyclus ticks had fed, showed no symptoms but a control beagle became paralysed after 4 I. holocyclus females fed on it. Treatment was instituted immediately upon the onset of clinical signs and the dog recovered uneventfully.
Diffuse neuromuscular disease occurs sporadically in dogs. The most commonly reported diffuse neuromuscular diseases are polyradiculoneuritis (coonhound paralysis), tick paralysis, botulism, and myasthenia gravis (1,2,12). This clinical report describes an atypical presentation of a diffuse neuromuscular disease in a dog.
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Cross-reactivity between all the paralysis inducing tick species of veterinary relevance in Africa was demonstrated, by using a monoclonal antibody directed against the paralysis inducing toxin of Rhipicephalus evertsi evertsi. Western blot results, together with amino acid composition studies indicated that this monoclonal antibody recognizes protein bands of similar molecular mass and amino acid composition in R. evertsi evertsi and Ixodes rubicundus. This suggests that the Karoo paralysis toxin of I. rubicundus is possibly also a trimer with a high degree of homology to the spring lamb paralysis toxin of R. evertsi evertsi. The conclusive identity of these protein bands of I. rubicundus could not be shown. Bio-assay studies performed on 1-day-old chickens suggested that the anti-spring lamb paralysis toxin monoclonal antibody also recognizes the paralysis toxin present in Argas (Persicargas) walkerae, by rendering some degree of protection against the effect of this toxin.
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Tick and tick-borne disease (TBD) problems of sheep and goats are less well studied than those of cattle. Nevertheless, small ruminants are able to acquire worthwhile resistance to most tick species and the principles of enzootic stability and the need to preserve it are similar to those with cattle. In practice, sheep and goats are often grazed nomadically and initial TBD infections may be delayed. This may well account for losses from Nairobi sheep disease and heartwater. Sheep and goats are also affected by direct tick damage including tick bite abscesses, tick paralysis, tick-induced dermatophilosis, etc. Otherwise direct damage is believed to be only slight and stress from dipping causes reductions in liveweight gain greater than those caused by the ticks. Even "pour-on" preparations produce no economic benefit in studied situations despite the lack of stress. A pragmatic approach to tick management is needed for varying situations although the need to preserve enzootic stability is of paramount importance.
The appetence responses of the ixodid ticks Ixodes rubicundus and Rhipicephalus punctatus to various stimuli were quantified under laboratory conditions. A greater percentage of I. rubicundus generally responded to the different stimuli at lower than at higher temperatures while the converse was usually true for R. punctatus. Radiation heat and shadowing evoked a response in the greatest percentage of I. rubicundus, whereas CO2 and host odour were responsible for a similar reaction in R. punctatus. A single perturbation of the substrate caused more than 50% of I. rubicundus to respond while constant perturbation resulted in a progressive decrease in the proportion of ticks reacting. Significantly more R. punctatus than I. rubicundus were attracted to a CO2 trap and the R. punctatus were also attracted to the trap over a greater distance. Significantly more older than younger ticks of both species responded to the various stimuli.
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Seasonal inflammatory neurologic disorders following tick-bites have been reported more and more often during the last few years. They usually consist in a peripheral neurologic syndrome. However, involvement of the central nervous system is not uncommon. Two new cases seen at the Val-de-Grâce Hospital are reported here. The author reviews the circumstances in which the disease occurs and it's clinical features. The course is variable and may result in serious sequelae. Pathogenesis remains unknown. Viral, toxinic, and immuno-allergic factors have been incriminated. Practitioners should consider this diagnosis, during the summertime, especially in high-risk subjects (campers, agricultural workers, troops during field exercise).
The Australian scrub-tick Ixodes holocyclus causes a series of significant toxic effects in its victims. The most important feature of tick envenomation is neuromuscular paralysis. Children poisoned by ticks may manifest only local motoneural effects, usually facial paralysis. Progressive ascending flaccid paralysis occurs if the removal of an embedded tick is delayed. The specific neurological features of tick-bite are discussed in the light of a series of 6 children who all showed signs of tick paralysis. Tick venom is known to slow nerve conduction, and may have a botulinum-like effect at the neuromuscular junction. The literature on the neurological effects of tick-envenomation is reviewed.
Tick paralysis is probably a common condition in wild birds, but rarely observed. The authors report the case of a collared dove (S. decaocto) presenting a fatal neurological syndrome associated with the fixation of a Ixodes pari female above the right eye. Virological studies of bird's tissues and of the tick were negative. These findings were compatible with tick paralysis or a minor equivalent of this syndrome. In addition, it was the first time that a collared dove is found as host for I. pari.
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A general review of the tick-borne diseases of sheep and goats is given, with the emphasis on those thought to be of greatest economic importance. These include babesiosis, theileriosis, cowdriosis, anaplasmosis, ehrlichiosis, Nairobi sheep diseases and tick paralysis. A commented list of tick-borne diseases and their vectors is presented. It is stressed that large gaps remain in our knowledge of the real importance in the field of many of these diseases, especially in local stock.