Dog Mites Dog Mites

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纪雪薇 林泽萍

陈睿杰 刘志彬 陈睿杰 刘志彬

谢浩源谢浩源

Mites in dogs is known generally as Mange and cause severe irritation in dogs with symptoms of inflammation, itching and hair loss( 炎症，瘙痒和脱毛 ).

Mites cause their damage by tunneling into the skin via the hair follicles and oil glands( 毛囊和皮脂腺 ) of the epidermal layer.

Mites normally live freely in dogs and cats, even humans, without ever bothering their host( 螨虫通常自由的生活在犬、猫甚至人身上而对宿主的生活不造成影响 ); it is only when the immune system of the host suffers because of any number of circumstances do the mite begin their process of infestation – sometimes causing life-threatening conditions.( 当宿主的免疫系统受损时 , 任意数目的螨虫都可以造成感染 , 甚至危害宿主的生命 )

The most frequent types of dog mites are as follows:

S. scabiei var. canis/Mange mites( 犬疥螨 )

Otodectes cynotis/Ear mites( 犬耳痒螨 )

Demodex canis( 犬蠕形螨 )

Sarcoptes is round in outline and up to 0.4 mm in diameter. Adults have 4 pairs of short legs, of which the third and fourth pairs do not project beyond the margin of the body.

虫体呈圆形，龟状，口器短。背部生刚毛。

( 图 1) 雄螨在 1 、 2 、 4 对脚有钟形吸 盘，第三对脚各有长刚毛 1 根。

( 图 2) 雌螨在第 1 、 2 对脚上有钟形吸盘。第 3 、 4 对脚有刚毛。

Its most important recognition characters are the numerous transverse ridges( 横嵴 ) and triangular scales on the dorsum, features possessed not by the other mange mite of domestic mammals. 背部有众多的横嵴和三角形的鳞屑

Sarcoptes mites spend their entire life on or in the skin. The male and female copulate( 交配 ) on the skin surface and the male soon dies off.  The female then burrows into the upper layer of skin and begins forming tunnels.   As she tunnels along eggs are laid that fill the tunnels. ( 雌虫在宿主体表挖掘隧道 , 并在里面产卵 )

Adult mites feed on the serum( 血清 ) that oozes into the tunnels from the surrounding irritated tissue.  When the female mite completes her egg laying mission she dies at the end of the tunnel.  The eggs( 卵 ) soon hatch to form larvae( 幼虫 ) and then molt to become nymphs( 成虫 ).  The larvae and nymphs also feed on serum and skin debris. When the nymph makes a final molt to become an adult they return to the skin surface where they mate and start the life-cycle over anew.  

Incomplete Incomplete metamorphosismetamorphosis

Transmission from animal to animal is thought to be through direct contact( 直接传播 ).  Dog and cats in close contact with an infected host are succeptible.

Animals can also become infected from fomites( 污染物 ) e.g. infested pens and blankets, combs, brushes, collars and any upholstered surfaces( 受到污染的钢笔 , 毛毯 , 梳子 , 刷子 , 项圈和软垫的表面 ).  

Young and poorly nourished animals are the most succeptible to infection.

Severe, constant itching( 严重地 , 不断地瘙痒 ) at any time of year is a classic symptom of sarcoptic mange. Areas with less hair, such as the earflaps, elbows, hocks( 跗关节 ), ventral abdomen( 腹部 ), chest, and legs, are affected most commonly. The mites cause hair loss, a reddened rash, and yellowish crusts( 脱发 , 红疹 ,淡黄色的渗出物 ) to form on the skin in affected areas.

Typically the ear margins and elbows are affected most severely. The ear margins tend to have thickened, crusty material on the tips and yellow scales( 增厚 , 变硬 , 形成鱼鳞状黄痂 ).

The animal may develop a secondary skin infection and severe scratches from the trauma of constantly scratching( 皮肤的继发感染 , 严重抓伤 ). The lymph nodes also may swell( 淋巴结肿大 ) as a result of mite related inflammation.

Diagnosis of sarcoptic mange infection is by deep skin scraping to find the parasite. Multiple scrapings are necessary on skin areas without excoriation( 在无损伤部位多次刮取 ). Deep scrapings are necessary and should be performed to a depth where some bleeding occurs( 在出血部位深层刮取 ).

Scrapings should be examined under the microscope( 显微镜下检查 ), and are best treated with 10% potash before examination. The presence of a single mite is sufficient for diagnosis( 单个螨虫足以确诊 ). However, mites are often absent, even with multiple skin scrapings.( 可先服用治疗螨虫的药物看有否好转 )

A diagnostic clinical sign, although non-specific, is the pinnal-pedal reflex.

①Clipping the hair from the affected area.( 患部剪毛 )②An anti-seborrheic shampoo that breaks down and

removes crusts, skin oil, and debris.( 除去污垢和痂皮 )

③ Debride and swab with parasiticidals dip e.g. Selamectin,Amtiraz, Dipterex.( 局部涂擦杀螨药的油剂 )

④ Medication: Ivermectin/Doramectin 0.2-0.4mg/kg sc/im.⑤All animals and objects that have come into contact

with a dog should be washed thoroughly and disinfected.( 所有与犬只有接触的动物和物品都应该彻底清洁和消毒 )

Comprehensive prevention: The best way to prevent transmission is to

avoid any contact with animals or the environment of any animal that may be carrying scabies( 避免接触任何可能带有疥螨的动物及环境 ).

All boarding facilities, grooming equipment( 剪毛器械 ), and bedding materials( 垫料 ) should be washed thoroughly and disinfected on a regular basis( 定期彻底清洁和消毒 ).

Parasiticidal pet collar( 除虫项圈 )

Otodectes is elliptical with conical mouthpart. The epimeres( 上段 ) extending from the bases of

legs I and II are joined. The male has broad bowl-shaped ambulacra( 钟形吸盘 ) borne on very short unsegmented pedicels( 不分节的腹柄 ) on all the legs, but only legs I and II of the female have pedicels and amulacra. Legs III of the female terminate in two long setae and legs IV are reduced.

虫体呈椭圆形，口器长，呈圆锥状，脚比较长。

雄螨第 1 、 2 、 3 对脚有钟形吸盘，第 4 对脚短小。

雌螨第 1 、 2 、 4 对脚有钟形吸盘，第 3 对脚有 2 条长刚毛。第四对足不发达。

Male Otodectes cynotis Female Otodectes cynotis

The life cycle of Otodectes is similar to that of all other mites, i.e. development from egg to adult via a larval and two nymphal stages. Development time is about 3 weeks.

Otodectes larvae feed for 3 to 10 days, rest for a short time and then molt to become a protonymph( 一期若虫 ). This nymphal stage is rather short and leads to the telonymph( 二期若虫 ); once the female reaches this stage copulation occurs with an adult male mite( 二期若虫交配 ). Fertilization only occurs, however, after the female telonymph has molted to become an adult female( 成虫受精 ).

The life span of adult mites is about 2 months. ( 成虫大约有两个月的寿命 )

Incomplete metamorphosisIncomplete metamorphosis

Infective routes: Contagious infection Young animals are most susceptible

to infestation and, as the mites are highly contagious and not host-specific( 高度传染性和无特定宿主 ), all in-contact animals should be presumed to be infected.

Head shaking. Scratching the ears (there may be sores

around the ears as a result of scratching) . Reddish-brown to black discharge (crusts

and cerumen) in the ears that resemble coffee grounds.( 红棕色 , 黑色像咖啡渣滓样的渗出物 , 痂和耳垢 )

A characteristic otitis externa of parasitic origin.( 寄生虫引起的外耳炎 )

Odour( 气味 ) Sometimes there seem to be no observable

signs of ear mites.

Sometimes  lesions may spreads to other areas of the head or the rest of the body( 病变的扩散 )

Accumulation of exsudate and cerumen in auditory canal( 耳垢和分泌物的沉积 )

A diagnosis of ear is usually made by one of the following methods:

①Direct visualization of the mites with an otoscope.( 检耳镜直接观察法 )

②Microscopic examination of the cerumenous debris from an infected ear canal.( 显微镜下观察感染耳道取出的耳垢 )

① Instillation of Paraffin oil to the ear and then rub( 向耳内滴入石蜡油 )

② Debride and swab with Parasiticidals dip e.g. Selamectin,Amtiraz,Permethrin. ( 局部涂擦杀螨药的油剂 )

③Medication: Ivermectin/Doramectin 0.2-0.4mg/kg sc/im.④ Use antibiotics when secondary bacterial

infections.( 继发性细菌感染时 , 应配合抗生素治疗 )

Comprehensive prevention: The best way to prevent is thus to

keep your pets indoors.(减少外出 ) To avoid any contact with itching and

ectillotic animals.( 避免与有脱毛和瘙痒症状的动物接触 )

Parasiticidal pet collar( 除虫项圈 ) Periodic deworming( 定期驱虫 )

Demodex are easily recognised by their annulate( 环状的 ), vermiform (‘worm-like’) shape( 蠕虫状 ), and is a white, oblong(长形的 ) mite. Adult female mites measure 300 µm and the males about 250 µm. The capitulum(头部口器 ) is horseshoe-like with clearly visible mandibles. The cuticula of the body resembles transverse wrinkles. Four pairs of stump-like legs end with 2 claw-like structures. 虫体长形，呈蠕虫状，分头、胸、腹三部。背腹扁平，头部口器呈马蹄形，胸部有四对粗短的脚，腹部有横皱纹。

Demodex mites spend their entire life on the skin of dogs, where they reside in the hair follicles( 毛囊 ) and, rarely, the sebaceous glands( 皮脂腺 ).

The developmental cycle starts with the larvae hatching from the fusiform(梭形的 ) eggs. The six-legged larvae(六足幼虫 ) moult(蜕皮 ) to become the eight-legged first nymphal stage(八足一期若虫 ). This is followed by a second nymphal stage, which in turn moults to give rise to the final adult stage.

The whole life cycle is completed in about 3 weeks. All stages of the mite can be found in the hair follicles, as well as the lymphatic system, bloodstream, and other bodily organs.

Incomplete Incomplete metamorphosismetamorphosis

The mites are transferred directly from the mother to the puppies within the first week of life.( 主要感染方式 )

Transmission of the mites is by direct contact only( 直接传播 ). That is, the mother and puppy must be physically touching, as the parasite cannot survive off of the animal( 无法在动物体外生存 ).

Most puppies are immune to the mite‘s effects and display no clinical signs or lesions. A few are not immune and it is these puppies that develop full-blown cases of mange.( 大多数不表现出临床症状 )

Demodicosis has two forms: FORM #1: LOCALIZED( 局部型 ): Localized demodicosis occurs as

isolated scaly bald patches( 局灶性的脱毛 , 脱屑 ), usually on the dog‘s face, creating a polka-dot appearance(圆点状 ).

Localized demodicosis is considered a common puppyhood ailment and approximately 90% of cases resolve with no treatment of any kind( 不需治疗常可自愈 ).

FORM #2: GENERALIZED(全身型 )

The entire dog is affected with patchy fur, skin infections, bald, scaly skin.( 皮肤感染 , 脱毛 ,脱屑 ) Sometimes large patches of affected skin are present, sometimes multiple “polka dots” of lesions cover the dog, and sometimes the entire body is involved. The secondary bacterial infections make this a very itchy and often smelly skin disease(细菌继发感染导致非常瘙痒和皮肤有恶臭 ). 

The standard method for diagnosis of infection with Demodex mites is microscopic examination of deep skin scrapings and detection of mites( 显微镜下刮屑检查 ). Another option is to examine plucked hair for the presence of mites.(拔毛检查 )

To perform a skin scraping, the skin should be squeezed( 刮屑前挤压皮肤 ), thus expelling the mites from the depths of the hair follicles to the surface. Demodex mites are present in the skin of healthy dogs and a single mite found in a scraping may be consistent with a diagnosis of healthy skin. (健康的皮肤上发现蠕形螨也是正常的 )

Skin scrapings from several areas are necessary to confirm infestation. ( 多部位刮屑取样 )

①Debride and swab with hydrogen peroxide(双氧水洗擦 )

②Use parasiticidals dip e.g. Selamectin,Amtiraz,Permethrin. ( 涂擦杀螨药的油剂 )

③Medication: Ivermectin/Doramectin 0.2-0.4mg/kg sc/im.④Dexamethasone/Chlortrimeton may be used when

itching seriously.⑤Skin infections are usually present in these cases

and antibiotics will likely be necessary.(抗生素的应用 )

Females should be spayed as soon as the disease is controlled. Also, predisposition to demodicosis is hereditary and should not be passed on.( 对全身型蠕形螨病的母犬不宜留作种用 )

The dog should be fed a reputable brand of dog food so as to avoid any nutritionally related problems. ( 避免营养问题 )

Keep up the pet‘s vaccinations.( 疫苗接种 ) The mites themselves cause suppression of the

immune system so the pet needs every advantage to stay healthy. (提高抵抗力保持健康 )

It is very important that cortisone type medications such as prednisone NOT be used in these cases as they will tip the immune balance in favor of the mite.( 可的松类的药物会导致免疫平衡失调 )