5例人皮蝇导致的猫疖性蝇蛆病和外用氟雷拉纳的治疗效果

王帆

Furuncular myiasis caused by Dermatobia hominis in five cats and effificacy of topical fluralaner for its treatment

5例人皮蝇导致的猫疖性蝇蛆病和外用氟雷拉纳的治疗效果

翻译: 王羽迪

Background – Dermatobia hominis (D. hominis) is a botfly that causes furuncular myiasis in several species of domestic and wild animals. However, reports of feline infestation by larvae of this dipteran are rare.

Objective – To report the natural occurrence of furuncular myiasis caused by D. hominis in five cats and the efficacy of topical fluralaner for its treatment.  

Animals – Five adult mixed-breed cats (four males, one female) were diagnosed and treated, all living in the state of Rio de Janeiro, Brazil.  

Results – The cats were treated with topical fluralaner. After this treatment, the larvae were dead after 24 h in three cats and after 48 h in two. There was spontaneous expulsion of larvae in two cats, and it was necessary to perform manual expression for removal of dead larvae in the other three cats.

Conclusions and clinical importance – Dermatobia hominis can cause furuncular myiasis in cats, although this appears to be less common than in other animal species. Topical fluralaner proved to be effective in the treatment of this parasitic disease.

背景-人皮蝇(D.hominis)是一种引起多种家养和野生动物疖性蝇蛆病的皮蝇。然而, 猫被这种双翅目幼虫感染的报道很少。

目的-报告5只猫自然发生人皮蝇引起的疖性蝇蛆病, 以及外用氟雷拉纳对其治疗的效果。

动物-诊断并治疗了5只成年混血猫 (4只雄性, 1只雌性) ,均生活在巴西里约热内卢。

结果-猫外用氟雷拉纳治疗。3只猫治疗24 h后幼虫死亡, 2只猫治疗48 h后幼虫死亡。2只猫自发排出幼虫,另3只猫需要进行人工挤压才能清除死亡幼虫。

结论和临床意义-人皮蝇可引起猫疖性蝇蛆病, 但这似乎没有其他动物常见。外用氟雷拉纳被证明对治疗这种寄生虫病有效。

Introduction  

引言

Among the dipterans that cause myiasis in cats, specie of the families Oestridae, Calliphoridae, Sarcophagidae and Muscidae are most prominent. Dermatobia hominis  (Diptera: Oestridae) is a botfly that causes furuncular myiasis. It is endemic in neotropical America.

在引起猫蝇蛆病的双翅目动物中，以狂蝇科、丽蝇科、麻蝇科和蝇科的种类最多。人皮蝇(双翅目：狂蝇科)是一种引起疖性蝇蛆病的皮蝇。它是热带美洲的地方流行病。

The biological cycle of D. hominis is complex, as adult flies are rarely seen, and the females use other dipterans to carry their eggs to the host. The parasitic stage is caused by larvae from the 1st to the 3rd instars, which  penetrate the skin of the mammalian host and cause furuncular myiasis when the slave dipteran alights on the skin of a warm-blooded animal to feed. The larvae emerge through the breathing pore to pupate in the soil after approximately six weeks. The next stages are free-living, with pupae in the soil and adults living in forested areas.

人皮蝇的生物周期很复杂，因为很少看到成虫，雌虫利用其他的双翅目昆虫把卵带到宿主那里。寄生阶段是由1到3龄的幼虫引起的，当双翅目寄生昆虫落在温血动物的皮肤上进食时，幼虫会穿透哺乳动物宿主的皮肤，导致疖性蝇蛆病。大约六周后，幼虫通过呼吸孔钻出，在土壤中化蛹。接下来的阶段是自由生活，蛹在土壤中，成虫生活在森林地区。

Dermatobia hominis is an obligate parasite of mammals such as cattle, dogs, goats, pigs, horses , rabbits and  humans.There are only a few scientific reports of feline parasitism, and among these, two are from Brazil and  one is from Venezuela.

人皮蝇是牛、犬、山羊、猪、马、兔子和人类等哺乳动物的专性寄生虫。关于猫寄生的科学报告很少，其中两份来自巴西，一份来自委内瑞拉。

Infestation by D. hominis larvae causes pain, local inflammation, serosanguinous exudate formation, rest lessness, irritation and pruritus, which can result in nodule ulceration and secondary bacterial infection.

人皮蝇幼虫的感染导致疼痛、局部炎症、血清渗出、坐立难安、刺激和瘙痒，这可能导致结节性溃疡和继发细菌感染。

The treatment in other mammalian species generally involves administration of antiparasitic agents and/or surgical removal of the larvae during anaesthesia. For cats,the literature describes the removal of the larvae through digital compression with the animal sedated, without use of antiparasitic drugs. The use of ivermectin, followed by application of selamectin seven days later, has been described for the treatment of nasal myiasis caused by Oestrusovis (Diptera: Oestridae) in a cat, and use of lotilaner has been reported for the treatment of ulcerative myiasis caused by Chrysomya bezziana (Diptera: Calliphoridae) in two cats. There are no reports of ectoparasiticide use for the treatment of furuncular myiasis caused by D. hominis in cats. This study reports the occurrence of furuncular myiasis caused by D. hominis in  five naturally infested cats and the effectiveness of topical fluralaner for treatment.  

其他哺乳动物的治疗通常包括使用抗寄生虫药物和/或在麻醉状态下进行手术清除幼虫。 对于猫，文献描述了在动物被镇静的情况下通过挤压来去除幼虫，而不使用抗寄生虫药物。有报道称，使用伊维菌素治疗一只猫由羊狂蝇（双翅目：狂蝇科）引起的鼻蛆蝇病，七天后再使用赛拉菌素，还有报道称，使用洛替拉纳治疗两只猫由蛆症金蝇（双翅目：丽蝇科）引起的溃疡性蛆蝇病。目前尚无使用体外驱虫药治疗猫由人皮蝇引起的疖性蝇蛆病的报道。本研究报告了5只因自然感染人皮蝇导致猫疖性蛆蝇病和外用氟雷拉纳的治疗效果。

Case series

病例分析

During the period from October 2019 to May 2020, in the city of Seropedica, Rio de Janeiro, five 3–12-year-old cats  (one female, four males) belonging to different owners  were presented owing to painful, hyperaemic, exudative, nodular lesions with a central orifice in which live moving  larvae were visible (Figure 1). The signalment of each animal and location of the lesions are shown in Table 1.

2019年10月至2020年5月期间，在里约热内卢的Seropedica市，有5只3 - 12岁的猫(1只母猫，4只公猫)分别属于不同的主人，它们有疼痛、充血、渗出、结节性病变，中央孔可见活动的幼虫(图1)。每只动物的特征和病变位置见表1.

Figure 1. Lesions of cats with furuncular myiasis caused by Dermatobia hominis larvae.

In all cases, it is possible to observe a hyperaemic nodular lesion with a central orifice, from which a serosanguinous secretion is drained.Lesions had different locations on different cats: (a) Case 5, on the tail; (b) Case 3, on the tail; (c) Case 1, in the dorsal cervical region; (d)Case 4, on the side of the right posterior limb.

图1.人皮蝇幼虫引起猫疖性蝇蛆病的病变。

在所有病例中，都可以观察到充血的结节性病变，其中央有孔，渗出血清分泌物。不同猫的病变部位不同:(a)病例5，尾部;(b)案例3，尾部;(c)病例1，在颈背区;(d)病例4，右后肢侧面。

After owner approval, all cats were hospitalised and  clinically monitored by veterinarians for 48 h. The mortality of the larvae was confirmed by the attending veterinarian in each case. For treatment, one pipette containing  0.89 mL of Bravecto Topical Solution (MSD Animal Health; Cruzeiro, SP, Brazil) was applied. This dose corresponds to the range of fluralaner doses (40–94 mg/kg per cat) recommended for cats weighing between 2.8 and 6.25 kg. All cats received analgesia with meloxicam (0.05 mg/kg) once daily and dipyrone (25 mg/kg) twice daily for three consecutive days.  

经主人批准后，所有猫均入院接受兽医临床监测48小时。所有幼虫均由主治兽医确认死亡。治疗时，一支滴剂含0.89 mL贝卫多外用溶液。该剂量对应于体重在2.8 - 6.25 kg之间的猫的氟雷拉纳剂量范围(每只猫40-94 mg/kg)。所有猫均给予美洛昔康(0.05 mg/kg)每日1次，安乃近(25 mg/kg)每日2次，连续3天。

The cats were evaluated for periods of 12 h, 24 h and 48 h for larval mortality, which was determined by the absence of movement inside the wound. Larvae died after 24 h in three cats and after 48 h in two cats. Spontaneous expulsion of a single dead larva occurred in two  cats. Although it was necessary to perform manual expression for removal of dead larvae in the other three cats, the procedure was easy to perform and did not require sedation. After removing the larvae, the wounds were cleansed with 0.01% povidone iodine and the skin lesions had improved after seven days.  

对猫进行12小时、24小时和48小时的幼虫死亡率评估，幼虫死亡率由伤口内的活动情况决定。3只猫感染的幼虫在24小时后死亡，2只猫感染的幼虫在48小时后死亡。虽然在其他三只猫中需要手动清除死的幼虫，但操作简单，不需要镇静。清除幼虫后用0.01%聚维酮碘清洗创面，7天后皮肤病变有所改善。

The expelled larvae were analysed under a stereomi croscope for observation of the presence or absence of morphological characteristics compatible with D. hominis  larvae, as described by Guimaraes and Papavero (Figure 2).

在立体显微镜下对去除的幼虫进行分析，按着Guimaraes和Papavero的描述，以观察其是否具有与人皮蝇幼虫的一致形态特征。

Figure 2. Third-stage larva of Dermatobia hominis with robust anterior end, with spines and hooks only in the widest part of the body and tapering posterior end.

图2, 人皮蝇3期幼虫，前段粗壮，有刺，钩只位于虫体最宽部位，后端逐渐变细。

Discussion  

讨论

This report describes five cases of furuncular myiasis caused by D. hominis larvae in domestic cats. Topical fluralaner caused spontaneous expulsion of larvae in two cats. The larval mortality rate observed was 100%, in three cats after 24 h and in two cats after 48 h. Dermatobia hominis infestation is considered to be uncommon in domestic cats, even though it already has been described by other authors. The dipteran species that most commonly cause this type of myiasis in cats belongs to the genus Cuterebra (Diptera: Oestridae).

这个报告描述了5例家猫感染人皮蝇幼虫引起的疖性蛆蝇病。外用弗雷拉纳可引起两只猫的幼虫自然排出。观察到的3只猫在24小时后幼虫死亡率为100%和2只猫在48小时后的幼虫死亡率为100%。人皮蝇在家猫中感染不常见，但也已经被其他作者描述过。最常引起猫蝇蛆病的是双翅目属(双翅目:狂蝇科)

The most common site affected in the cats of this  report was the tail base. This may perhaps be explained by the difficulty of self-grooming and consequent removal of larvae. The development of myiasis in the feline species usually is associated with clinical debilitation that limits hygiene habits, such as obesity, dental problems or neglect of skin wounds by owners.The typical hosts for D. hominis are dogs and wild animals. The cases described here occurred in outdoor-access cats and the owners lived next to forested areas. Therefore, these factors may be related to a greater risk of infestation by D. hominis larvae.  

在这篇报告中，猫最常见患病部位是尾部。这可能由于难以自我梳理和随后清除幼虫。蝇蛆病在猫科动物体内的发展通常与临床虚弱限制自我清洁行为有关,如肥胖、牙科问题或主人对皮肤伤口的忽视。人皮蝇的代表宿主是犬和野生动物。这里描述的病例发生在户外活动的猫和主人住在森林地区附近。因此，这些因素可能是人皮蝇幼虫感染的较大风险因素。

The only treatment that has been described previously for myiasis caused by D. hominis in cats is surgical removal after sedation of the animal. The advantage of  using an ectoparasiticide is the fact that there is no need to subject the animal to sedation, which could present some risk depending on the presence of concomitant diseases. Ectoparasiticides such as macrocyclic lactones have been reported for the treatment of myiasis in other mammalian species and for Cuterebra infestations and Oestrusovis in cats. Among the isoxazolines, lotilaner has been reported to be efficacious for the treatment of C. bezziana causing ulcerative myiasis in two cats, where oral administration caused 100% mortality of larvae in the two animals evaluated 24 h after administration. In our series, two cases required >24 h exposure time for complete larval death. Whether this reflects a slower uptake time for the topical application of an isoxazoline versus oral administration remains to be determined in further studies. However, it is important to highlight that these  reports have evaluated the effectiveness of two different isoxazolines against two different dipteran species in cats.  

以前描述过的治疗猫由人皮蝇引起的蝇蛆病的唯一方法是麻醉猫后进行手术清除,使用体外杀虫剂的优点是无需对动物进行镇静，而镇静可能会带来一些风险，这取决于是否存在共发症。据报道，大环内酯类体外杀虫剂可用于治疗其他哺乳动物的蝇蛆病，也可用于治疗猫的黄蝇属感染和狂蝇属感染。在异噁唑啉类药物中，洛替拉纳对两只猫由蛆症金蝇感染的溃疡性蝇蛆病的治疗有效，经口服24 h后，两只猫的幼虫死亡率为100%。在这个系列病例中，有两个案例需要>24小时的接触时间才能使幼虫完全死亡。这是否反映了外用异噁唑啉比口服的吸收时间更慢，仍有待进一步研究确定。然而，重要的是要强调，这些报告评估了两种不同的异噁唑啉对猫两种不同的双翅目物种感染的有效性。

The isoxazolines are a newer class of parasiticides that have proven to be safe and effective for treatment of a variety of ectoparasites of importance to cats. Although furuncular myiasis is rare in cats, topical fluralaner appears to be a safe and effective option for eliminating D. hominis larvae.

异噁唑啉是一种较新的杀虫剂，已证明能安全有效的治疗猫的各种体外寄生虫感染。虽然疖性蝇蛆病在猫上很罕见，但外用氟雷拉纳似乎是一种安全有效的清除人皮蝇幼虫的治疗方案。

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