The mechanisms of pathogenicity in the tick paralyses.
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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.
Adult female Ixodes holocyclus were collected from the field at Fig Tree Pocket, a Brisbane suburb, at Tamborine Mountain, Queensland and at Lismore, New South Wales, in November 1974. Females were also reared from engorged nymphs collected off bandicoots from Tamborine Mountain July 1974 and 1975. In November 1974 unexposed 2-3 week old British breed calves, weighing between 26 and 46 kg were infested with 2,4,8 or 10 ticks. Neither 2 nor 4 females per calf caused paralysis. A challenge of 8 to 10 females induced paralysis 6 to 9 days after infestation by which time most ticks had engorged. There was little difference between ticks from different geographic localities. The site of attachment had no influence on tick toxicity. In September 1975, 2-3 week old British breed and Sahiwal x Jersey calves were infested with female ticks which had moulted 2-4 weeks prior to infestation. All but one calf with 10 ticks and all calves with 4 ticks became paralysed 8 to 13 days after infestation. At the time of paralysis only 1 of the 86 ticks had engorged and the remainder were small (30 to 50 mg). The greater toxicity of the latter ticks may have been due to the different treatment of ticks prior to infestation or to variations in the production of toxin associated with slow feeding. Four of 7 paralysed calves were saved using canine antitick serum.
In this study the value of drugs administered with hyperimmune serum in the treatment of advanced disease produced by Ixodes holocyclus was compared under controlled conditions. All control dogs died rapidly whereas one dog survived and 3 dogs died after receiving hyperimmune serum alone. When promethazine hydrochloride was administered with hyperimmune serum 2 dogs recovered rapidly while the remaining 2 died. Administration of dexamethasone and hyperimmune serum allowed 3 dogs to survive while administration of phenoxybenzamine hydrochloride in conjunction with hyperimmune serum allowed rapid recovery of all 4 dogs. Phenoxybenzamine hydrochloride, an alpha-adrenergic blocking drug, was chosen because of its potential to attenuate the arterial hypertension previously reported (Ilkiw et al 1988). The survival of all dogs together with the rapid return to normality indicated that this drug was beneficial in the treatment of dogs with advanced signs of tick paralysis.
Three techniques were developed to detect IgE specific to Ixodes holocyclus. The radioimmunoassay (RIA) was found to be superior to both radioallergosorbent test and enzyme immunoassay techniques. Validation of the RIA technique was provided by dilution experiments and by a blind study involving 13 volunteers; the RIA graph was linear over a wide range of concentrations. The RIA ratio clearly discriminated between those volunteers with and without systemic allergic reactions and helped to identify borderline cases showing local or cutaneous allergic reactions. It appears to be suitable for diagnostic and research applications.
The clinical features of bites by the Australian scrub tick, Ixodes holocyclus, are reviewed. Eight cases of tick bite are summarized, including six new cases of tick paralysis in children. In almost all cases neuroparalysis became worse transiently, after the tick had been removed. One child with life-threatening respiratory and bulbar palsy received canine antitick antivenene, with rapid reversal of clinical signs. The differential diagnosis of tick bite includes all acute childhood diseases which can affect the motor units; the importance of including the possibility of tick envenomation in the differential diagnosis of acute weakness or paralysis in children is illustrated. The clinical features of neuromuscular paralysis are described, together with a review of the tick's local effects at the bite site.
The authors report a series of 9 cases of meningoradiculitis after tick bites and compare them with 56 other cases in the literature. Clinically, the bite is followed by a free interval, then more or less extensive local erythema, pain then paralysis is undoubtedly the most typical presentation. Uni- or bilateral paralysis of the 7th cranial nerve was found in more than 50% of cases. Erythema may exceptionally be absent. There may be forms with pain alone. Finally, there may sometimes be pyramidal signs or signs of brain irritation. As concerns the course, one should note the absence of respiratory complications, and although there are usually no or minimal sequelae, one should note the slowness of the recovery in certain paralytic cases. In the laboratory, pleocytosis is constantly found in the C.S.F. As concerns physiopathology, there are 3 theories, virus, allergic and toxic.
Ticks may transmit a variety of human pathogens and are second in importance only to the mosquito as a vector of human disease. The majority of tick-borne diseases are nonspecific in their initial clinical and laboratory presentation and may be confused with a variety of more common illnesses. A history of tick exposure is frequently not available. Although specific serologic tests exist for confirming the diagnosis of many of these diseases, the time required for confirmation of results makes them of little use in the acute situation. Recognition of the epidemiology of tick-borne pathogens and clinical suspicion are of key importance in making the appropriate diagnosis. Early and specific therapy is a principal factor in reducing the morbidity and mortality associated with these diseases.
Although of low morbidity, sweating sickness is readily induced in calves by infestation with positive Hyalomma truncatum adult ticks. This epitheliotrophic disease has no specific cure except by the administration of hyperimmune serum obtained from animals which have recovered and are subsequently immune to the disease. Treatment with hyperimmune serum, however, has associated problems of donor availability, possible serum contamination and i.v. administration of a relatively large volume. This paper compares the treatment and cure of sweating sickness using unrefined hyperimmune serum and that of an experimental suspension. The latter proved relatively inefficient probably due to a low concentration of effective immunoglobulins. Immunoblot analyses of the sera of affected animals, using tick salivary glands as antigen during the course of the trial revealed 4 tick salivary gland proteins with molecular masses of between 27-33 kDa. These are proposed as being associated with sweating sickness immunodominance.
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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.
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Most Australian spiders are capable of causing a bite which produces some degree of local reaction and occasionally systemic effects. However, only the Sydney funnel-web spider which is limited to a 160 kilometre radius from the centre of Sydney and the red-back spider which is found in all States are capable of inflicting a potentially lethal bite.
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Investigations on the impulse propagation and the pattern of amplitudes of toxically by Argas (Persicargas) walkerae larvae impaired peripheral nerves were carried out under oxygen saturated and anoxic conditions. It was demonstrated, that the maximum nerve conduction velocities of the isolated N. ischiadicus were slightly lowered in the first carbogenic and anoxic phase, in comparison with normal nerves. After the second incubation the conduction velocities were, however, almost the same or even higher. The survival times of the nerves after anoxic exposure, which were determined by the temporal persistence of the potentials, revealed that this neurophysiological parameter always resulted in a higher value for the damaged nerves after every two anoxic phases. The diseased nerves therefore tolerate anoxia longer and better than do healthy nerves in respect to their excitability and in their function of impulse propagation. From these in vitro investigations it is concluded that the noxious substance responsible for the paralysis is not cell-bound, but circulates humorally. The toxin possesses membranophilic properties, but its somatic linkage is very labile.