Department of Veterinary Medicine, University of Perugia, Via San Costanzo 4, 06126, Perugia, Italy.
Faculty of Veterinary Medicine and Animal Science, Poznań University of Life Sciences, Wolynska 33, 60-637, Poznań, Poland.
Parasit Vectors. 2022 Mar 24;15(1):104. doi: 10.1186/s13071-022-05218-6.
In canine leishmaniosis (CanL) endemic areas, pathologists often receive skin biopsies for testing with histopathologic findings suggestive-but not conclusive for a definitive diagnosis-of CanL lesions. I the absence of data on the infective status of animals, the diagnosis can therefore be challenging. The aim of this retrospective study was to evaluate the ability of immunohistochemistry (IHC) and quantitative PCR (qPCR) methods to detect Leishmania infection in skin biopsies with a histopathologic diagnosis of lymphoplasmacytic/histiocytic and/or granulomatous dermatitis and to correlate the pattern, depth and severity of the histopathologic lesions with the parasite load detected by qPCR and IHC.
Thirty formalin-fixed, paraffin-embedded skin samples were evaluated by hematoxylin-eosin (H&E) staining, IHC, conventional PCR (cPCR) and qPCR. The severity, pattern and depth of the dermal inflammation and parasite load were graded.
Leishmania was detected by H&E staining in 8/30 sections (26.66%) and by IHC in 14/30 samples (46.66%). Parasite DNA was detected in 14/30 samples (46.66%) by cPCR and in 21/30 samples (70%) by qPCR, with an extremely variable parasite load (1.32-62.700 copies). The level of agreement was fair between H&E staining and cPCR (κ = 0.32), and moderate between H&E staining and IHC (κ = 0.58). The level of agreement between IHC and cPCR was good (κ = 0.65); between IHC and qPCR, moderate (κ = 0.41); and between cPCR and qPCR, fair (κ = 0.28). A significant association was found between the severity of dermal inflammation and the parasitic skin load by IHC, although with weak linear correlation.
Our study underlines the difficulty of obtaining a definitive diagnosis of CanL cutaneous lesions, even with the most accurate diagnostic tests currently available. Based on our results, no single test is suitable on its own for the diagnosis of cutaneous lesions caused by Leishmania. However, in the presence of a moderate/severe lymphoplasmacytic/histiocytic and/or granulomatous dermatitis, we suggest performing IHC, as in our study this technique proved to be the method with the highest discriminatory power to estimate the role of the parasite in skin lesions. In mild lesions, IHC loses its discriminatory power and should be effectively combined with techniques such as qPCR.
在犬利什曼病（CanL）流行地区，病理学家经常收到皮肤活检进行检测，其组织病理学检查结果提示存在但不能明确诊断为 CanL 病变。如果没有关于动物感染状态的数据，那么诊断可能具有挑战性。本回顾性研究的目的是评估免疫组织化学（IHC）和定量 PCR（qPCR）方法检测具有淋巴浆细胞/组织细胞和/或肉芽肿性皮炎组织病理学诊断的皮肤活检中利什曼原虫感染的能力，并将组织病理学病变的模式、深度和严重程度与 qPCR 和 IHC 检测到的寄生虫负荷相关联。
对 30 例福尔马林固定、石蜡包埋的皮肤样本进行苏木精-伊红（H&E）染色、IHC、常规 PCR（cPCR）和 qPCR 评估。对真皮炎症的严重程度、模式和深度以及寄生虫负荷进行分级。
H&E 染色在 8/30 个切片（26.66%）中检测到利什曼原虫，在 14/30 个样本（46.66%）中通过 IHC 检测到。cPCR 在 14/30 个样本（46.66%）中检测到寄生虫 DNA，qPCR 在 21/30 个样本（70%）中检测到，寄生虫载量变化很大（1.32-62.700 拷贝）。H&E 染色与 cPCR 之间的一致性水平为中等（κ=0.32），H&E 染色与 IHC 之间的一致性水平为中度（κ=0.58）。IHC 与 cPCR 之间的一致性水平为良好（κ=0.65）；IHC 与 qPCR 之间的一致性水平为中度（κ=0.41）；cPCR 与 qPCR 之间的一致性水平为中等（κ=0.28）。尽管线性相关性较弱，但真皮炎症的严重程度与 IHC 检测到的寄生虫皮肤负荷之间存在显著相关性。
我们的研究强调了即使使用目前最准确的诊断检测方法，也很难明确诊断 CanL 皮肤病变。根据我们的结果，没有一种单一的检测方法适合单独诊断由利什曼原虫引起的皮肤病变。然而，在存在中度/重度淋巴浆细胞/组织细胞和/或肉芽肿性皮炎的情况下，我们建议进行 IHC，因为在我们的研究中，该技术被证明是估计寄生虫在皮肤病变中作用的最具鉴别力的方法。在轻度病变中，IHC 失去了其鉴别力，应与 qPCR 等技术有效结合。
