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Toxins have been shown to present in the salivary glands, whole body extracts, and eggs of ticks. They cause histological lesions in the skin, and in various organs of tick hosts. Among toxicoses, tick paralysis is of the greatest medical and veterinary importance. Toxins are secreted by cells "b" of acinus II in salivary glands during tick feeding.
Ticks were collected at monthly intervals for 16 consecutive months from individual dogs by their owners in or close to the town of Stellenbosch, Western Cape Province. They were also collected for 27 consecutive months from dogs presented for a variety of reasons at three veterinary clinics in Stellenbosch, and from dogs upon admission to an animal welfare shelter. At one of the veterinary clinics ticks were also collected from cats. Dog owners collected six ixodid species from their pets and the most numerous of these were Haemaphysalis leachi and Rhipicephalus gertrudae. Twelve ixodid tick species and the argasid tick, Otobius megnini were collected from dogs at veterinary clinics and the animal shelter, and H. leachi, R. gertrudae and Rhipicephalus sanguineus were the most numerous. A total of nine dogs were infested with the Karoo paralysis tick, Ixodes rubicundus. No clear pattern of seasonality was evident for H. leachi, which was present throughout the year. The largest numbers of adult R. gertrudae were generally present from August to October, while adult R. sanguineus were collected during October 2000, February and March 2001, from January to April 2002 and during October 2002. Five ixodid tick species, of which H. leachi was the most numerous and prevalent, were collected from cats.
Synthetic pyrethroid pour-on compounds have been developed for use on cattle but many are now also registered for the control of ectoparasites on small ruminants. The breed of small livestock has been known to influence the efficacy of various pour-ons and we hypothesized that differences in the duration of protection afforded by a synthetic pyrethroid pour-on against ticks on small livestock, would be greatest between hairy and woolly breeds. Angora goats with mohair, Dorper sheep with hairy wool, and Merino sheep with wool were treated with 1% m/v deltamethrin pour-on with an oil base at a dosage rate of 1 ml 5 kg-1 body mass. The duration of effective protection against Ixodes rubicundus, the Karoo paralysis tick, was determined under field conditions. Angora goats proved to be the highest risk group, but were afforded the least protection. Efficacy never reached 100% in this group and within 3 weeks the goats were already at risk of paralysis. Dorper sheep were afforded above 90% protection for 3 weeks and 85% after 4 weeks. In the case of the Merino sheep efficacy of protection remained above 90% up to 7 weeks post-treatment and was still 87% during Week 8. Differences in the amount of sebum and suint in the epidermis of the different breeds may be responsible for differences in the rate of spread and the rate of dilution of the active compound in the epidermis.
OBJECTIVE: To attribute a cause and quantify allergic-like symptoms observed among island residents. DESIGN: Skin prick tests and intradermal injections with ultraviolet-irradiated, filtered (0.22 microns) whole-body homogenates of the soft tick, Ornithodoros capensis, were used to reproduce experimentally the symptoms observed. SETTING: Heron Island, Great Barrier Reef, Australia. PARTICIPANTS: Island residents were designated as such after having spent more than 1 month on the island during the summer seabird breeding season. INTERVENTIONS: Control measures were instigated using a residual insecticide, delta-methrin, sprayed inside sleeping quarters. MAIN OUTCOME MEASURES: Acaricide spraying reduced (X2 = 4.42; P less than 0.05) the number of island residents complaining of having been bitten by ticks, yet was considered an inefficient control measure as 67% reported being attacked by ticks after spraying. RESULTS: Among 97 island residents, elevated total IgE levels were associated with reaction to tick bite in 11 cases (X2 = 27.17; P less than 0.001), but were not of reliable diagnostic value. Symptoms included intense pruritus, blistering (a major feature), erythema, weeping lesions, lymphangitis, dull ache, rheumatic pain and general lassitude, and intense discomfort. Sera from two of four volunteers with known reactions to O. capensis and one of four others with reactions to the Australian paralysis tick, Ixodes holocyclus, cross-reacted with antigens from a total of four of six biting/stinging and non-biting arthropods (radioallergosorbent tests). CONCLUSIONS: Symptoms associated with reactions to tick bite peaked in severity at 35-40 hours and thus the response was most likely delayed type IV hypersensitivity.
Amongst blood-feeding arthropods, ticks of the family Ixodidae (hard ticks) are vectors and reservoirs of a greater variety of infectious agents than any other ectoparasite. Salivary glands of ixodid ticks secrete a large number of pharmacologically active molecules that not only facilitate feeding but also promote establishment of infectious agents. Genomic, proteomic and immunologic characterization of bioactive salivary gland molecules are, therefore, important as they offer new insights into molecular events occurring at the tick-host interface and they have implications for development of novel control strategies. The present work uses complementary DNA (cDNA) sequence analysis to identify salivary gland transcripts expressed by the Rocky Mountain wood tick, Dermacentor andersoni, a vector of the human pathogens causing Rocky Mountain spotted fever, Colorado tick fever, tularemia, and Powassan encephalitis as well as the veterinary pathogen Anaplasma marginale. Dermacentor andersoni is also capable of inducing tick paralysis. Automated single-pass DNA sequencing was conducted on 1440 randomly selected cDNA clones from the salivary glands of adult female D. andersoni collected during the early stages of feeding (18-24h). Analysis of the expressed sequence tags (ESTs) resulted in 544 singletons and 218 clusters with more than one quality read and attempts were made to assign putative functions to tick genes based on amino acid identity to published protein databases. Approximately 25.6% (195) of the sequences showed limited or no homology to previously identified gene products. A number of novel sequences were identified which presented significant sequence similarity to mammalian genes normally associated with extracellular matrix (ECM), regulation of immune responses, tumor suppression, and wound healing. Several coding sequences possessed various degrees of homology to previously described proteins from other tick species. Preliminary nucleotide variation analysis of these and other tick sequences suggests extensive nucleotide diversity, which has implications for evolution of tick feeding. Intra-species diversity studies can be a promising tool for identifying sequence variations potentially associated with phenotypic traits affecting vector-host-pathogen interactions.
From 1990 through 1995, 913 ticks removed from 460 human patients in Georgia or South Carolina were identified and recorded. The majority of these specimens (758, 83.0%) were lone star ticks, Amblyomma americanum. One hundred and four (11.4%) American dog ticks Dermacentor variabilis, 36 (3.9%) blacklegged ticks Ixodes scapularis, 9 (1.0%) Gulf coast ticks Amblyomma maculatum, and 6 (0.7%) brown dog ticks Rhipicephalus sanguineus were also recovered. All active stages (larvae, nymphs, and adults) of A. americanum were represented, whereas nymphs and adults of D. variabilis and I. scapularis and only adults of A. maculatum and R. sanguineus were recorded. Compared with data published for other regions in the U.S.A., A. americanum was a much more prevalent parasite of humans in the current survey. Only 1 (3%) of the I. scapularis collected was a nymph. Because these tick species are vectors of zoonotic pathogens or cause tick paralysis in humans, the data have epidemiological significance.
The unique geographic isolation of Australia has resulted in the evolution of a distinctive range of Australian arachnid fauna. Through the pioneering work of a number of Australian arachnologists, toxinologists, and clinicians, the taxonomy and distribution of new species, the effective clinical treatment of envenomation, and the isolation and characterisation of the many distinctive neurotoxins, has been achieved. In particular, work has focussed on several Australian arachnids, including red-back and funnel-web spiders, paralysis ticks, and buthid scorpions that contain neurotoxins capable of causing death or serious systemic envenomation. In the case of spiders, species-specific antivenoms have been developed to treat envenomed patients that show considerable cross-reactivity. Both in vitro and clinical case studies have shown they are particularly efficacious in the treatment of envenomation by spiders even from unrelated families. Despite their notorious reputation, the high selectivity and potency of a unique range of toxins from the venom of Australian arachnids will make them invaluable molecular tools for studies of neurotransmitter release and vesicle exocytosis as well as ion channel structure and function. The venoms of funnel-web spiders, and more recently Australian scorpions, have also provided a previously untapped rich source of insect-selective neurotoxins for the future development of biopesticides and the characterisation of previously unvalidated insecticide targets. This review provides a historical viewpoint of the work of many toxinologists to isolate and characterise just some of the toxins produced by such a unique group of arachnids and examines the potential applications of these novel peptides.
Myasthenia gravis is a disorder of neuromuscular transmission that occurs in congenital and acquired autoimmune forms. Acquired myasthenia gravis is probably the most common neuromuscular disorder in dogs that can be diagnosed and treated. An early, accurate diagnosis and appropriate therapy is of utmost importance to a good clinical outcome in this disorder. This article focuses on the diagnosis and treatment of acquired myasthenia gravis in dogs and cats with brief discussions of other disorders of neuromuscular transmission, including congenital myasthenia gravis, tick paralysis, botulism, and organophosphate intoxication.
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An acute flaccid paraparesis or ascending quadriparesis in an infant or child constitutes a very important pediatric neurology emergency. The Guillain-Barré syndrome (GBS) is the most frequent cause. This is primarily an autoimmune, post-infectious, demyelinating, peripheral nervous system process. A small percentage of children develop a primary axonal process not unlike that identified more commonly in China. Because of the potential for acute respiratory compromise, any child suspected of having GBS needs immediate hospitalization. The major considerations in differential diagnosis include transverse myelitis, toxic neuropathies, tick paralysis, infantile botulism, myasthenia gravis, and dermatomyositis. On occasion, some younger children present with an acute severe pain syndrome that may mask as a pseudo-encephalopathy. Another clinical variant is the Miller-Fisher syndrome characterized by ataxia, ophthalmoparesis, and areflexia. This is associated with a high frequency of the anti-GQ-1-b antibodies. Although most children with GBS have a relatively benign clinical course, some become very ill and require intubation with intensive care monitoring. Immunomodulating treatment should be used for any child who loses the ability to walk. To date, no well-controlled study has been completed analyzing the relative merits of the two most commonly used therapies, namely plasmapheresis or intravenously administered immunoglobulin.
The clinical spectrum of this remarkable non-syphilitic spirochaetosis (spirochaeta infection) of the nervous system is described in light of 53 further cases with reference to our earlier description of 47 cases. As the etiological diagnosis is not possible in all cases the knowledge of clinical courses is especially important. Males are affected almost twice as often as women. The disease is especially prevalent in the sixth decade. Usually, the syndrome begins in the warm season with exquisite pain and other sensory irritations in combination with marked malaise. Initial signs during the winter as well as painless clinical courses were also noted. About one half of the patients remembered contact with arthropodes or a chronic migrating erythema. In most cases (95%), asymmetrical peripheral signs followed the painful stage. More than two thirds of the patients showed affection of cranial nerves, usually facial palsy. Twenty percent demonstrated paresis of the extremities alone, the combination of involvement of cranial nerves and extremities was noted in one third of the cases. The sensory signs were usually only mild. Occasionally, the neurological impairment was limited to isolated sensory impairment. In contrast to the closely related Lyme disease, central nervous affection as well as cardiac and arthritic involvement is rare: 34 percent demonstrated mild psychopathological impairment; in one case a Babinski-phenomenon was elicited. Knee joint pain and gonarthritis were found in one case each. Even though meningeal signs were usually absent, the CSF showed alterations suggestive of chronic lymphocytic meningitis in all cases. At the same time, local synthesis of all three immune globulins was documented, especially of IgM (85%).
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Envenomation by arachnids causes significant medical illness worldwide. Scorpion sting is the most important arachnid envenomation causing adult morbidity and pediatric mortality. Important groups of spiders include the widow spiders (Latrodectus spp.), the recluse spiders (Loxosceles spp.), and two spiders confined to single countries: the Australian funnel web spider (Atrax and Hadronyche spp.) and the armed spider (Phoneutria spp.) from Brazil. There are four widow spider antivenoms available, including the Australian redback spider antivenom and the American black widow antivenom. Despite good in vitro animal work demonstrating effective neutralization with these antivenoms, and cross-reactivity between many species, there continues to be a reluctance to use them in some countries. They are both associated with a relatively low rate of allergic reactions. Redback antivenom is routinely used by the intramuscular route, which may not be as effective as intravenous use based on clinical experience and animal studies. Antivenoms are available for Loxosceles spp., but there is little evidence to support their effectiveness, particularly against local effects. The Australian funnel web spider causes severe neurotoxic envenomation, and antivenom appears to be effective in reported cases. An antivenom exists for the Brazilian armed spider, but is used in only a minority of cases. Many scorpion antivenoms exist worldwide, but there remains significant controversy regarding their efficacy. Animal and human venom level studies demonstrate neutralization of circulating venom in systemic envenomation. Clinical experience in countries where antivenom has been introduced suggests it has reduced pediatric mortality. However, three controlled trials demonstrated that antivenom was not effective, but these included few severe cases. Until controlled trials of antivenom in systemically envenomated patients are undertaken, antivenom use appears justified in severe envenomation. Although envenomation from arthropods is common, no antivenoms exist for these, excepting Lonomia caterpillars in South America, and Ixodes paralysis ticks in Australia.
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The blacklegged tick, Ixodes (Ixodes) scapularis Say, 1821, is redescribed, based on laboratory reared specimens originating in Bulloch County, Georgia. Information on distribution, host associations, morphological variation, and medical/veterinary importance is also presented. A great deal of recent work has focused on this species because it is the principal vector of the agent of Lyme disease (Borrelia burgdorferi Johnson, Schmidt, Hyde, Steigerwaldt & Brenner) in eastern North America. Its distribution appears to be expanding, and includes the state of Florida in the southeastern United States north to the provinces of Nova Scotia and Prince Edward Island, Canada, west to North and South Dakota, United States, and south to the state of Coahuila, Mexico. Although I. scapularis feeds on at least 125 species of North American vertebrates (54 mammalian, 57 avian, and 14 lizard species), analysis of the U.S. National Tick Collection holdings show that white-tailed deer, Odocoileus virginianus (Zimmermann), cattle, Bos taurus L., dogs, Canis lupus L., and other medium-to-large sized mammals are important hosts for adults as are native mice and other small mammals, certain ground-frequenting birds, skinks, and glass lizards for nymphs and larvae. This tick is a polytypic species exhibiting north-south and east-west morphological clines. Analysis of variance and Student-Newman-Keuls multiple comparisons revealed significant interpopulational variation that is expressed most significantly in the nymphal stage. Nymphs from northern (Minnesota, Massachusetts, Maryland) populations had relatively larger basis capituli with shorter cornua (except Maryland) than southern (North Carolina, Georgia) populations. Midwestern populations (Minnesota, Missouri) differed from eastern populations (Massachusetts, Maryland, North Carolina, Georgia) in idiosomal characters (broader scuta, larger coxae III, and IV). In addition to Lyme disease, this tick is also a primary vector of the agent of human and rodent babesiosis, Babesia microti Franca. Under laboratory conditions it has transmitted the agents of deer babesiosis, Babesia odocoilei Emerson & Wright, tularemia, Francisella tularensis McCoy & Chapin, and anaplasmosis, Anaplasma marginale Theiler. Moreover, I. scapularis can reach pest proportions on livestock, and females can cause tick paralysis in dogs.
The Guillain-Barré syndrome is a pediatric neurologic emergency and the most common cause in children of rapidly evolving, usually flaccid, weakness with associated areflexia. Two treatable illnesses, namely tick paralysis and acute cord compression, demand immediate differential diagnosis. Rarely, poliomyelitis still mimics infantile Guillain-Barré syndrome. Specific precursor infections, such as Campylobacter jejuni, are now recognized to affect the clinical presentation of Guillain-Barré syndrome. Cerebrospinal fluid evaluation and electromyography are usually diagnostic; new modalities, such as anti-GM1 antibodies, magnetic resonance imaging, and magnetic stimulation, are being evaluated in childhood Guillain-Barré syndrome. Although most cases of Guillain-Barré syndrome have benign courses, all require initial respiratory and autonomic monitoring to prevent fatal outcomes. No well-controlled pediatric studies comparing plasmapheresis with intravenous immunoglobulin have occurred. Results of treatment with either modality are encouraging. A synopsis of these reports is included in this review.
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