Suspected tick paralysis (Ixodes holocyclus) in a Miniature Horse

A 9‐year‐old Miniature Horse gelding infested with ticks (Ixodes holocyclus) was presented with flaccid motor paralysis causing recumbency. Neurological examination and other diagnostic tests did not identify an alternative aetiology, leading to a presumptive diagnosis of tick paralysis. The gelding was treated with tick antiserum and intensive supportive care. He made a gradual recovery over the 48 h following presentation and was discharged without further complications. This case report describes in detail the clinical signs and successful treatment of a Miniature Horse with flaccid paralysis caused by suspected envenomation by Ixodes holocyclus.     

Distributions of the paralysis ticks Ixodes cornuatus and Ixodes holocyclus in south-eastern Australia

OBJECTIVE: To describe the actual and potential geographic distributions of Ixodes cornuatus and I holocyclus in south-eastern Australia. PROCEDURE: Examination of ticks from museum collections and trapped animals were made. (Bioclimatic analysis BIOCLIM) was used to predict potential distributions. RESULTS: I holocyclus was collected from rodents (Rattus fuscipes, R lutreolus, R rattus), wombats (Vombatus ursinus), cats and dogs in Gippsland and I cornuatus was collected from rodents (R fuscipes), wombats, cats and dogs in central Victoria. All life-cycle stages of both species were collected during the warmer months of the year. The known distribution of the two species was established from specimens in museum collections and suggested that a boundary between the two may exist in eastern Gippsland. BIOCLIM suggested that the area immediately to the east of Melbourne was climatically suitable for I holocyclus, although no endemic foci of infection are currently known from this region. The potential distribution of I cornuatus included east Gippsland and the Otway Ranges, areas in which the tick is not currently known to occur. CONCLUSIONS: I holocyclus and I cornuatus have more restricted distributions than current collections suggest and therefore may have the possibility to extend their geographical ranges in the future.     

Asymmetrical focal neurological deficits in dogs and cats with naturally occurring tick paralysis (Ixodes holocyclus): 27 cases (1999-2006)

OBJECTIVE: To describe basic epidemiological features, clinical characteristics and outcomes of asymmetrical focal neurological deficits identified in dogs and cats with naturally occurring tick paralysis (Ixodes holocyclus). DESIGN: A retrospective study. PROCEDURE: Computer records were reviewed for all dogs and cats treated for tick paralysis between July 1999 and June 2006 at a suburban veterinary hospital in Newcastle, New South Wales. RESULTS: Neurological deficits were identified in 17/197 dogs and 10/89 cats and included unilateral facial paralysis (14 dogs; 2 cats), anisocoria (4 dogs; 7 cats), unilateral loss of the cutaneous trunci reflex (1 dog; 1 cat) and Horner's syndrome in 2 cats with anisocoria. Occurrence of deficits was not linked to season, severity of tick paralysis, breed, age, sex or body weight. With facial paralysis and anisocoria, the site of tick attachment was invariably on the head or neck and always ipsilateral to the facial paralysis. By contrast, with anisocoria alone, no consistent relationship was noted between any one pupillary dimension and the side of tick attachment. With cutaneous trunci deficits the site of tick attachment was the ipsilateral caudal axilla. Compared with recovery times from generalised signs of tick paralysis, those for facial paralysis were significantly longer (days to weeks; P < 0.001), those for anisocoria showed no significant difference (P = 0.25) and those for cutaneous trunci deficits lagged by 6 and 7 days. CONCLUSIONS: Asymmetrical focal neurological deficits are a consistent finding in a proportion of dogs and cats with naturally occurring tick paralysis due to I. holocylcus.     

Retrospective study of 103 presumed cases of tick (Ixodes holocyclus) envenomation in the horse

Objective Review 103 cases of presumed tick envenomation in horses. Design Retrospective study. Method Variables, including date of presentation, age, breed, weight, presence of ticks, gait and respiration scores, duration of recumbency, treatment, outcome and complications were recorded. A series of univariable screening tests were performed and used in a multivariable logistic regression model. Results There were a total of 103 cases affecting 10 breeds, aged between 1 week and 18 years of age. Horses >6 months old and weighing >100 kg had a higher odds of death than those <6 months old and <100 kg. Cases were seen from North Queensland to the central coast of New South Wales and were more likely to present in the warmer months. There was no association between the number of ticks found on an animal and death. Horses with a higher respiratory score had higher odds of dying, but there was no association between gait score and survival. Horses recumbent >120 h after presentation had higher odds of dying. Complications were reported in 35% of horses. The odds ratio for survival was higher for horses receiving >0.5 mL/kg of tick antiserum. Overall, 74% of horses survived. Multivariable modelling was limited by the small sample size. Conclusion In general, tick envenomation in horses follows the geographic distribution of Ixodes holocyclus. Tick antiserum administered at >0.5 mL/kg increases the odds of survival. It would appear that the complications associated with managing a recumbent horse increase the odds of death.     

Prospective survey of tick paralysis in dogs

OBJECTIVE: To obtain information on tick paralysis in dogs, including the nature of disease, host signalment, tick-host relationship, treatment, disease progression and recovery, and preventive measures. DESIGN: A prospective survey of 577 dogs affected by tick paralysis was conducted during 1998. Forty-two veterinary clinics along the eastern coast of Australia were instructed to complete survey forms for the first 15 dogs that presented with tick paralysis during September to November. RESULTS: Five percent of dogs died from tick paralysis. Younger dogs were more likely to survive. Long coat length was associated with a greater tick burden but not greater tick size, whereas coat thickness had no bearing on either. Dogs with mild disease recovered more quickly from tick paralysis. Respiratory and gait scores reflected disease severity and were good prognostic indicators. The size of the tick did not reflect the severity of the clinical condition it induced in the host. No method of tick removal or in situ treatment improved recovery time or reduced mortality. However, the time spent in hospital was significantly less for dogs from which the live tick was manually removed. Inspiratory stridor, evident in some dogs with tick paralysis, was not related to tick attachment on the neck. The use of acepromazine maleate or dexamethasone did not reduce recovery time or mortality. Increasing the dose of tick antitoxin serum (TAS) above 0.1 mL/kg had no effect on mortality or recovery time. Dogs with severe disease that received an additional dose of TAS were significantly less likely to survive. Subcutaneous use of TAS at the site of tick attachment was of no benefit in reducing mortality or time to initial clinical improvement. A registered preventative product had not been used on the majority of dogs. Clipping the coat to search for ticks did not reduce mortality. CONCLUSIONS: Therapy needs to address cardiopulmonary dysfunction that may be due directly to the effect of tick toxin and not just respiratory compromise caused by progressive respiratory muscle failure.     

The weather determines the number of cases of tick paralysis in dogs and cats in eastern Australia,caused by Ixodes holocyclus,the eastern paralysis tick

We studied over 222,000 cases of emergency veterinary consultations in four regions along the eastern coast of Australia. We found that cases of tick paralysis (TP) caused by the eastern paralysis tick, Ixodes holocyclus, accounted for 7.5% of these cases: >16,000 cases. The season of TP and the number (prevalence) of TP cases varied among regions and over the years. Our study of the association between weather and (i) the start of the season of TP, and (ii) the number of TP cases revealed much about the intricate relationship between the weather and I. holocyclus. We studied the effect of the hypothetical availability of isoxazoline-containing tick-preventative medicines and found that an increase in the availability of these medicines had significantly contributed to the decrease in TP cases. We found that the weather in winter accounted for the time of the year the season of TP starts whereas the weather in summer accounted for the number of TP cases in the TP season. Last, through a study of the effects of shifts in the climate under four hypothetical scenarios (warmer/cooler and drier/wetter than average), we propose that the start of the season of TP depends on how soon the weather in winter becomes suitable for the activity (e.g. host-seeking) and the development of I. holocyclus nymphs, and that the number of TP cases during the TP season depends on how many engorged female ticks and their eggs survive during summer.     

Effects of the paralysis tick, Ixodes holocyclus, on the electrocardiogram of the Spectacled Flying Fox, Pteropus conspicillatus

OBJECTIVE: To evaluate cardiac electrical function in the Spectacled Flying Fox (bat) infested with Ixodes holocyclus. DESIGN: Prospective clinical investigation of bats treated for naturally occurring tick toxicity. PROCEDURE: ECGs were performed on bats with tick toxicity (n = 33), bats that recovered slowly (n = 5) and normally (n = 5) following treatment for tick toxicity, and on normal bats with no history of tick toxicity (n = 9). RESULTS: Bats with tick toxicity had significantly prolonged corrected QT intervals, bradycardia and rhythm disturbances which included sinus bradydysrhythmia, atrial standstill, ventricular premature complexes, and idioventricular bradydysrhythmia. CONCLUSIONS: The QT prolongation observed on ECG traces of bats with tick toxicity reflected delayed ventricular repolarisation and predisposed to polymorphic ventricular tachycardia and sudden cardiac death in response to sympathetic stimulation. The inability to document ventricular tachycardia in bats shortly before death from tick toxicity may be explained by a lack of sympathetic responsiveness attributable to the unique parasympathetic innervation of the bat heart, or hypothermia-induced catecholamine receptor down-regulation. Bradycardia and rhythm disturbances may be attributable to hypothermia.     

Dermatoses caused by infestations of immature Ixodes spp. on dogs and cats in Sydney, Australia

Infestations of larval and nymphal Ixodes spp. were identified in 16 dogs and 16 cats from several small animal clinics in Sydney. Cases occurred in late summer or autumn, peaking in February, and were seasonally recurrent in some individuals. Clinical signs of infestation included a papular dermatitis and irritation or pruritus that ranged from severe to mild or absent. The distribution of tick attachment tended to be cranial and ventral, with the face, legs, axillae and ventrum the most commonly affected sites. The estimated number of ticks in each infestation varied from less than 10 to more than 100. Basic morphological examination of ticks collected from affected animals was performed by attending veterinarians using light microscopy, and larvae and nymphs belonging to the Ixodes genus were identified. Ticks collected from 17 animals and submitted to the Department of Medical Entomology, Westmead Hospital were putatively identified as I. trichosuri (57%) and I. holocyclus (25%) larvae. Histopathological samples of attachment sites collected from three dogs and one cat were characterised by ticks attached in well-demarcated invaginations of the skin ('tick craters') associated with variable epidermal and/or dermal necrosis, focal eosinophilic intraspinous pustules, mild to marked eosinophilic and neutrophilic, superficial to deep, dermal perivascular to interstitial inflammation, and moderate to marked superficial dermal oedema and red cell extravasation. A range of topical acaricidal preparations, including fipronil and synthetic pyrethroids, were used for treatment.     

Reactions to tick antitoxin serum and the role of atropine in treatment of dogs and cats with tick paralysis caused by Ixodes holocyclus: a pilot survey

OBJECTIVE: To determine the incidence and nature of adverse reactions of dogs and cats to tick antitoxin serum and to re-evaluate the role of atropine in the treatment of tick paralysis. DESIGN: A retrospective questionnaire of veterinarians. PROCEDURE: Questionnaires were posted to 320 veterinarians in tick-endemic regions of Australia. Questions referred to dogs and cats treated for tick paralysis over a period of three years: the number treated, treatment protocols and adverse systemic reactions to tick antitoxin serum. Ninety completed questionnaires were returned and responses analysed. RESULTS: Veterinarians reported that approximately 3% of dogs exhibited adverse reactions immediately following treatment with tick antitoxin serum. Eighteen percent of these reactions were described as anaphylaxis, with the remaining 82% attributed to the Bezold-Jarisch reflex. Six percent of cats treated with tick antitoxin serum reacted adversely and the majority of reactions (63%) were ascribed to the Bezold-Jarisch reflex. Atropine was used routinely by 10% of responding veterinarians in the treatment of dogs and cats with tick paralysis. A similar number of veterinarians used atropine only in selected cases. Most veterinarians (76%) reported that they never used atropine in the treatment of tick paralysis in either dogs or cats. Within the survey population, premedication with atropine reduced the number of Bezold-Jarisch reactions following tick antitoxin administration approximately five-fold in dogs and four-fold in cats. CONCLUSIONS: Data from this pilot survey indicate that more cats than dogs have adverse systemic reactions to tick antitoxin serum and that the majority of these reactions in both dogs and cats could be related to the Bezold-Jarisch reflex. The number of reactions to tick antitoxin serum in dogs and cats could be significantly reduced by the routine use of atropine prior to administration of tick antitoxin serum.     

灭蚤项圈对犬、猫蚤的临床试验

采用自身对照试验，以自然感染栉首蚤（Ctenocephalides sp．）的犬与猫为试验动物，验证常熟市金牧药业有限公司生产的灭蚤项圈（犬用、猫用）对蚤的杀灭与防治效果。结果表明：在整个试验期间，所有参与试验的犬、猫均未出现任何不良反应，犬、猫在挂项圈（即用药）后第14～60天，杀虫率分别在97．3％～98．4％与96．6％～98．0％之间，杀虫效果极显著（P〈o．01）。证明灭蚤项圈（犬用、猫用）对犬、猫安全可靠，能长期杀灭犬、猫蚤类。