虱子：当心这个会玩单杠双杠的家伙！

在沉寂了几年后，最近门诊阴虱病患者猛然多起来，而且有不少被误当做湿疹、皮炎治疗数月，患者奇痒难忍，最终家里配偶、小孩都被传染，因此笔者在此呼吁大家提高警惕，医生在看病时也要注意检查。

在三种虱子中，以阴虱体型最为强壮，很像螃蟹，因此也被称为蟹虱，其2对大螯上有锯齿边缘，握住毛干犹如手握单杠双杠, 牢牢抓住不轻易放松，所以阴虱的间接传染不多，主要通过性接触或直接紧密接触而传染(图1~4）。

图一：湖蟹

图二：体形强壮的阴虱

图三：毛干上大量幼虫及成虫

图三：正在玩单杠的阴虱

关于虱子大家都不陌生。
虱毛目（学名：Phthiraptera）是原虱目和食毛目的合称，通称虱或虱子（英语：louse，slice）。全世界约有3,000种。虱寄生于人体、其他哺乳动物（除了单孔目和蝙蝠外）和鸟类的身上。以人类为宿主的虱有三种：人头虱、人体虱和阴虱（又称耻阴虱，见图）。其中，人头虱和人体虱属于人虱科（Pediculus  humanus），阴虱属于阴虱科（Pthirus pubis）。

头虱

幼虫

头皮大量幼虫

虱体型较小，无翅，身体扁平，寄生于毛发处，有善于勾住毛发的足（攫握器）。虱为渐变性发育，终生寄生于宿主体表，以宿主血液、毛发、皮屑等为食。寄生于人体的虱主要以宿主血液为食，其若虫每日吸血1次，成虫每日吸血数次。

虱病本身是寄生虫疾病，虱吸血时会向人体内注入唾液以防止血液凝聚，因而使人产生搔痒感。人亦可能因抓搔而使皮肤破损、溃烂和细菌感染。此外，人体虱还可传播流行性斑疹伤寒、战壕热、回归热等恶性传染病。
阴虱本身并不传播其他疾病，但是由于阴虱主要通过人类性行为传播，故属于性传播疾病的一种。

转发Bolognia 皮肤病学第三版有关阴虱文章一篇，以加深印象。

阴虱

Key features 关键特征
More properly designated “crab lice” (rather than “pubic lice”) because infestations may involve other hair-bearing sites such as the beard, eyelashes, axillae and perianal region
最好的称谓应该是称蟹虱，而不是称为阴虱，因为它可以在有其他毛发部位如胡须、眼睫毛、腋毛或肛周区域寄生。
Transmitted by sexual or close contact and to a lesser extent via contaminated clothing, towels and bedding
传播主要是通过性传播或密切接触传播，通过衣服、毛巾或床传播的机会较少。
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ntroduction 导言
Infestation with Pthirus pubis, the crab louse, causes discomfort, pruritus and embarrassment and may coexist with other sexually transmitted infections. 阴虱，或称蟹虱寄生，引起不适、瘙痒和尴尬难堪。本病可以跟其他性传播感染同时存在。
History 历史
The parasitic relationship between humans and crab lice dates back to prehistoric times.
可以追溯到史前
Epidemiology 流行病学
The incidence rate seems to be slightly higher in men, probably due to their increased amount of coarse body hair. Infestations with crab lice can be found in all socioeconomic and ethnic groups, although those of Asian descent or with minimal pubic hair are rarely infested. The highest prevalence is in men who have sex with men. Infestation is most frequently observed in those 15 to 40 years of age, correlating with increased levels of promiscuous sexual activity. Although infestation is often considered a sexually transmitted disease, individuals who have had no sexual exposures are occasionally infested via fomite transmission from contaminated clothing, towels or bedding.
男性发病率稍高，可能由于他们体毛的量比较粗大有关。蟹虱可以寄生在所有社会经济阶层和人种中，在亚洲人种较少，在阴毛稀少者中也比较罕见。在男同性恋者中传染率也高。发病年龄以15-40岁为多见，这与其性活动增加是相符合的。虽然本病被认为是一种性传播疾病，但是那些没有性活动的个体偶尔也有通过污染物如衣服、毛巾和床传染的。
Pathogenesis 发病机制
Crab lice, Pthirus pubis, are approximately 1 mm in length with a wider, shorter body than head lice, and they resemble tiny crabs (Fig. 84.10). Their eggs, which are found attached to human hairs, are viable for up to 10 days; the adult crab louse can live for at least 36 hours away from the host. Crab lice have serrated edges on their first claw that enable them to ambulate on the entire body surface. Thus, infestation occurs not only in pubic hair, but also in hair of the scalp, eyebrows, eyelashes, moustache, beard, axillae and perianal area. Indeed, 60% of patients with pubic lice are infested in at least two different hair-bearing sites. When the pubic area is shaved or treated, surviving crab lice can travel to other hairy areas of the body, including the scalp.
蟹虱，即阴虱，大约1mm长，1mm宽，身体比头端，它们很像一个微小的蟹。它们的卵，附着在人类毛发上，可以长达10天。成年蟹虱可以离开宿主存活至少36小时。蟹虱在它的第一对螯上有锯齿状边缘，这使得它能够在整个身体表面移动。所以这就使这种虱的感染不只是出现在阴毛处，而且也会在头发、眉毛、眼睫毛、胡须、腋毛和肛周区域出现。的确，阴虱患者的60%至少有2个不同毛发部位感染（在我国情况好像不一样，没那么多，因为中国人体毛、胡须，特别是长胡须都不多。译者注）。当阴毛剃除或在治疗时，幸存的阴虱就会转移到身体其他毛发部位，包括头发处。
Clinical features 临床特点
in individuals with chronic crab lice infestations. They are slate-gray to bluish, irregularly shaped macules measuring 0.5–1 cm in diameter. The breakdown of bilirubin to biliverdin by enzymes in louse saliva has been postulated to cause these lesions.
The possibility of additional sexually transmitted infections should be considered and the original source of the infestation sought in order to reduce the risk of recurrence.
在慢性蟹虱感染的个体中，它们表现为灰石板色到浅蓝色，不规则型的斑点，大小直径在0.5-1cm. 有假说认为虱子唾液中有种酶，导致胆红素或胆绿素破裂，从而形成这种损害。其他性传播感染的可能性要考虑到，并且感染的诱发原因要了解清楚，以减少复发的危险。
Pathology 病理学
Crab lice cause nonspecific inflammatory changes in the epidermis and dermis. Because lice live on the surface of the skin, they would not be evident histologically.
蟹虱在表皮真皮中引起非特异性炎症改变。由于虱子生活杂皮肤表面，因此它们在组织学改变并不明显。
Dierential diagnosis 鉴别诊断
The identification of crab lice and/or their nits is diagnostic (see Fig. 84.10). Skin diseases associated with pruritus have to be considered in the differential diagnosis, including other infestations (e.g. scabies) and arthropod bites. Nits on pubic or axillary hairs must be distinguished from white piedra and trichomycosis pubis or axillaris.
找到蟹虱及其幼虫可以确诊本病。与瘙痒相关的皮肤病在鉴别诊断中必须考虑到，包括其他感染，如疥疮和节肢动物叮咬。在耻骨部或腋毛处幼虫必须跟白色毛结节病和耻骨部或腋毛部毛发真菌病鉴别。
Treatment 治疗
Topical insecticides are the standard therapy for crab lice. Sexual partners should be treated simultaneously. Most commonly, permethrin (1% or 5%) and synergized pyrethrin products are utilized (Table 84.3). As with head lice, all topical insecticides should be applied on two occasions, 1 week apart, to ensure a proper therapeutic approach to hatched eggs. Moreover, all hairy areas of the body must be inspected for the existence of lice and then treated if there is any possibility of their presence. A single application of these topical products to only pubic hair may limit success rates to as low as 55%.
Currently, the safest and most effective topical treatment is 5% permethrin cream applied generously overnight to all possibly infested hairy areas, and then repeated 1 week later. Lindane has poor efficacy and higher toxicity, and the shampoo is not approved for extensive body application. Oral ivermectin on days 1 and 8 can be used for patients with perianal or eyelash involvement or when topical therapy is unsuccessful (see Table 84.3).
局部应用杀虫剂对于蟹虱是标准治疗。性伴侣也应该同时得到治疗。最常用的药物是1%-5%合成除虫菊酯和复方除虫菊酯（表84.3.). 像头虱治疗一样，所有的局部杀虫剂都应该用2次，间隔一周，以保证已孵化出的卵得到适当治疗。另外，注意检查所有有毛部位，只要有任何虱子存在的可能性，都要进行杀虫治疗。单纯对阴部使用局部杀虫治疗，就有可能降低成功率，低至55%。
目前，最安全有效的局部治疗药物是5%合成除虫菊酯霜，对全身所有毛发部位广泛涂抹，保留一个晚上，1周后重复涂抹。林旦（一种农用杀虫剂，国内被开发成治疗疥疮的药物，近些年市场不容易买到，译者注）有效性低，且毒性大。全身应用香波治疗并没有被认可。在开始的1-8天口服双氢除虫菊素可以用来治疗那些肛周或眼睑毛感染的患者，或者局部治疗效果不好的患者。

后续：文章看到最后，我科潘主任才公布一个治疗阴虱的秘方。在我国没有上述药物成品购买，似乎阴虱没有好药治疗。我在临床上，推荐患者使用风油精涂抹治疗，方法简便，疗效几乎百发百中。当然涂抹风油精仅限于阴毛处，对于眼睫毛处感染不合适，不过幸好眼睫毛感染在临床上少而又少。

浙江省人民医院皮肤科杭州上塘路158号开设皮肤科、皮肤美容专科、痤疮专科、性病专科开展皮肤外科、激光治疗、肉毒素除皱注射、微波+肉毒素联合治疗腋臭、光动力治疗、过敏原检测、敏感皮肤、青春痘和玫瑰痤疮治疗。

浙江省人民医院皮肤科樊一斌副主任医师：周一皮肤肿物门诊；周五专家门诊