VAIL, Colorado (EGMN) – Tick paralysis is often misdiagnosed – with potentially dire consequences – as one of the other diseases that cause an acute ascending paralysis with preserved mental status.
The arthropod-inflicted paralysis is most often confused with Guillain-Barré syndrome. Other causes of an acute ascending paralysis with preserved mental status include spinal cord tumors and acute poliomyelitis. Botulism, in contrast, causes a descending paralysis with preserved mental status, Dr. Sean O’Leary said at the annual conference on pediatric infectious diseases, which was sponsored by the Children’s Hospital, Denver.
Conducting a thorough search for an embedded tick is essential in a patient with an acute ascending paralysis with preserved sensorium, particularly when there is a history consistent with potential tick exposure. Treatment of tick paralysis is simple: remove the tick. Clinical improvement will follow within hours.
In unrecognized and untreated cases of tick paralysis, however, the fatality rate is about 10%, with death typically occurring just 18-30 hours after symptom onset, according to Dr. O’Leary of the Children’s Hospital and the University of Colorado, both in Denver.
Tick paralysis is more common in children than adults. The highest-risk group is young girls with long hair that can readily hide an engorged tick that’s had a blood meal. At 3 days after attachment, the tick (usually a female) begins secreting the neurotoxin that causes the paralysis. Symptoms appear 4-7 days after attachment. The peak time for tick paralysis is tick mating season: April through June.
The clinical scenario typically begins with loss of appetite and voice, followed by gait instability, ascending flaccid paralysis, excessive salivation, eye irritation, pupil asymmetry, and vomiting. Death usually is from respiratory failure. For more than half a century, there have been postmortem reports of ticks being found embedded in the skin of people who died suddenly of unexplained paralytic illnesses.
About 8% of the 870 named tick species have been associated with intoxication syndromes. The species that cause the most cases of human, dog, and livestock paralysis in North America are Dermacentor andersoni and D. variabilis, both of which are vectors for the rickettsial disease Rocky Mountain spotted fever. In the United States, tick paralysis occurs most often in the Pacific Northwest and Rocky Mountain states.
The tick toxin’s pathogenic mechanism isn’t fully understood. Australian investigators have reported that the toxin inhibits acetylcholine release at the neuromuscular synapse, but tick paralysis there is caused by Ixodes species, and it’s not clear that the same mechanism is at work in the paralysis caused by Dermacentor species, Dr. O’Leary said.
How to Remove a Tick
The proper way to remove a tick is to grab it with blunt forceps as close to the skin as possible and pull it straight out with steady pressure, according to Dr. O’Leary.
Don’t apply a hot nail or blown-out match to the critter’s backside. Don’t use tweezers or sharp forceps. Avoid using a twisting or corkscrew motion in removing the tick. Don’t crush or squeeze the tick’s body, as that can cause the tick to release more of the infectious organism or toxin.
Don’t handle the tick barehanded. “There have been documented cases of disease transmission” in people who did that, said Dr. O’Leary.
And although in bygone days it was a popular practice to apply gasoline, lidocaine, petroleum jelly, or other substances to the embedded tick to encourage it to back out, the current thinking is, don’t do it.
“There are horror stories about the use of those things,” he said.
Dr. O’Leary declared having no relevant financial relationships.
Copyright (c) 2010 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
科罗拉多州维尔(EGMN)——蜱瘫痪常常被误诊,可引起急性上行性麻痹而神志状态保持清醒,其后果可能十分严重。
丹佛儿童医院、科罗拉多大学丹佛校区的Sean O’Leary博士在由丹佛儿童医院主办的小儿传染病年会上说,节肢动物攻击引起的瘫痪极易与吉兰巴雷综合征相混淆。导致急性上行性麻痹而神志保持清醒的其他原因包括脊椎肿瘤和急性脊髓灰质炎。相比之下,肉毒杆菌中毒可引起下行性麻痹而神志保持清醒。
对有急性上行性麻痹而神志保持清醒的患者,必须全面查找嵌入体内的蜱,尤其是可能有蜱接触史时。蜱瘫痪的治疗很简单:取出蜱。在治疗后数小时内即可获得临床改善。
然而,若对蜱瘫痪不加识别和治疗,致死率约为10%,通常会在起病后18~30 h死亡。
与成人相比,蜱瘫痪更常见于儿童。高危人群为留长发的年轻女孩,蜱易于隐藏在头发中吸食头部鲜血。在接触3天后,蜱(通常为雌性)开始分泌可引起瘫痪的神经毒素。接触后4~7天可出现症状。蜱瘫痪发病的高峰时间为蜱交配季节:4月至6月。
临床典型表现为:最初出现食欲不振和声音消失,随即出现步态不稳、上行性软瘫、过度流涎、眼部刺激、瞳孔不对称以及呕吐。通常死于呼吸衰竭。半个多世纪以来,有关突然死于不明原因的瘫痪病的人经尸检发现皮肤内隐匿蜱的报道屡见不鲜。
870个蜱种中大约有8%与中毒综合征有关。北美人类、狗以及牲畜瘫痪最常见的病原体为安氏革蜱(Dermacentor andersoni)和变异革蜱(D. variabilis),均为立克次体病落基山斑疹热的传播媒介。
蜱毒素的发病机制尚未完全清楚。
如何取出蜱
取出蜱的正确做法为:用钝钳尽可能贴近皮肤钳住蜱,然后用恒定压力将其直接拖出来。
切勿使用热钉子或吹灭的火柴去烫其尾部。切勿使用镊子或尖头钳子。在取出蜱的过程中切勿使用扭力或螺旋动作。切勿夹碎蜱体,以避免蜱释放更多的传染性微生物或毒素。
切勿徒手处置蜱。
另外,切勿采用过去常用的错误方法,如汽油、利多卡因、凡士林油或其他物质。
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