Theis J H
Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis, CA 95616, USA.
Vet Parasitol. 2005 Oct 24;133(2-3):157-80. doi: 10.1016/j.vetpar.2005.04.007.
Coin lesions in the human lung present significant differential diagnostic problems to the physician. There are at least 20 known causes of such lesions, including neoplastic lesions, infectious diseases, and granulomas. The human medical literature contains many misconceptions about the life cycle of Dirofilaria immitis, including the method of entry of the infective-stage larvae and the development of the young adult worm. These misconceptions have obscured the recognition of the clinical presentation of pulmonary dirofilariasis and the potential for D. immitis to lodge in many other areas of the human body besides the lung. Exposure to infective larvae of D. immitis is more common in humans than is currently recognized. Reported cases in humans reflect the prevalence in the canine population in areas of the United States. The veterinary literature provides compelling evidence that D. immitis is a vascular parasite, not an intracardiac one. Its presence in the right ventricle is a post-mortem artifact, because it has never been shown to be there by echocardiography or angiography in a living dog, even though these techniques have demonstrated adult D. immitis in the pulmonary, femoral, and hepatic arteries; posterior vena cava; and right atrium of live dogs. Physicians have taken the name "heartworm" literally, believing that the worm lives in the heart and only after it dies does it embolize to the pulmonary artery. However, the coin lesion is spherical in shape, not pyramidal, as embolic infarcts to the lung in humans are known to be. The coin lesion is an end-stage result of the parasite's death in the vascular bed of the lungs and the stimulation of a pneumonitis followed by granuloma formation. This pneumonitis phase of human pulmonary dirofilariasis is often not recognized by the radiologist because of the way pneumonitis is diagnosed and treated and because the developing nodule is obscured by the lung inflammation. Serologic methods for use in humans are needed for clinical evaluations of patients with pneumonitis living in highly enzootic D. immitis regions. As well, epidemiological surveys are needed to determine the real extent of this zoonotic infection.
人类肺部的硬币状病灶给医生带来了重大的鉴别诊断难题。已知至少有20种病因可导致此类病灶，包括肿瘤性病变、传染病和肉芽肿。人类医学文献中存在许多关于犬恶丝虫生命周期的误解，包括感染期幼虫的进入方式和年轻成虫的发育过程。这些误解掩盖了对肺丝虫病临床表现的认识，以及犬恶丝虫除了肺部之外在人体许多其他部位寄生的可能性。人类接触犬恶丝虫感染期幼虫的情况比目前所认识到的更为常见。人类报告的病例反映了美国某些地区犬类种群中的患病率。兽医文献提供了令人信服的证据，表明犬恶丝虫是一种血管寄生虫，而非心内寄生虫。它在右心室的存在是一种死后假象，因为即使这些技术已在活犬的肺动脉、股动脉和肝动脉、后腔静脉及右心房中证实了成年犬恶丝虫的存在，但通过超声心动图或血管造影从未在活犬中显示它存在于右心室。医生从字面上理解“心丝虫”这个名称，认为这种虫子生活在心脏中，只有在它死后才会栓塞到肺动脉。然而，硬币状病灶是球形的，而不是已知的人类肺部栓塞性梗死那样呈锥形。硬币状病灶是寄生虫在肺部血管床中死亡以及随后引发肺炎并形成肉芽肿的终末期结果。由于肺炎的诊断和治疗方式以及发育中的结节被肺部炎症所掩盖，人类肺丝虫病的这个肺炎阶段往往未被放射科医生识别出来。对于生活在犬恶丝虫高度流行地区的肺炎患者进行临床评估，需要用于人类的血清学方法。同样，需要进行流行病学调查以确定这种人畜共患感染的实际范围。
