Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843, USA.
Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, 30602, USA; Zoetis, Veterinary Medicine Research and Development, Kalamazoo, MI, 49007, USA.
Vet Parasitol. 2020 Apr;280:109070. doi: 10.1016/j.vetpar.2020.109070. Epub 2020 Mar 30.
Onchocerca lupi is an emerging zoonotic parasite of dogs, endemic to the southwestern USA and areas of the Old World. Currently, there are no specific serological diagnostic tests able to detect O. lupi infection. Recent literature has demonstrated that commercially available heartworm antigen tests, despite being highly sensitive, may cross-react with infections by other filarid nematodes. There is no information on potential cross-reactivity of such tests in serum of dogs infected with O. lupi. Our objective was to assess serum samples of dogs naturally-infected with O. lupi for potential cross-reactivity before and after heat-treatment using a commercial heartworm ELISA kit. We obtained serum from 23 dogs naturally-infected with O. lupi. These dogs presented with ocular disease, and were consulted to schedule either surgical removal of ocular nodules due to infection or enucleation. Samples were tested in triplicate using the DiroCHEK® Heartworm Antigen Test kit (Synbiotics Corporation, Zoetis, Kalamazoo, MI, USA) following the manufacturers' protocol pre- and post-heat-treatment. Samples were heat-treated using a dry heat block at 103 °C for 10 min and then centrifuged at 1818×g for 20 min. Out of a total of 23 dogs, 19 (82.6 %) had no antigen detected regardless of heat-treatment, three dogs tested positive before and after heat-treatment, and a single dog turned positive after heat-treatment. These three dogs that were positive before and after heat-treatment were confirmedly co-infected with Dirofilaria immitis by the veterinarians responsible for these cases, and we were unable to get the history or follow up with the dog that turned positive post-heat-treatment only. Our data suggest that O. lupi infections should not result in false-positives when using the DiroCHEK® in dog serum, before or after heat-treatment. Dogs with clinical ocular onchocercosis that test antigen-positive in DiroCHEK® are likely co-infected with D. immitis, and should be further tested, including evaluation of microfilariae in blood and diagnostic imaging. If heartworm infection is confirmed, the animals should be enrolled in the recommended treatment protocol in accordance to the guidelines of the American Heartworm Society or other local organizations.
犬复孔绦虫是一种新兴的犬源人畜共患寄生虫，流行于美国西南部和旧世界的一些地区。目前，尚无专门的血清学诊断检测方法能够检测到犬复孔绦虫感染。最近的文献表明，尽管商用的心丝虫抗原检测非常敏感，但可能与其他丝虫线虫的感染发生交叉反应。目前尚无关于此类检测在感染犬复孔绦虫的血清中潜在交叉反应的信息。我们的目的是使用商业心丝虫 ELISA 试剂盒评估未经热处理和热处理后犬自然感染犬复孔绦虫血清样本的潜在交叉反应。我们从 23 只自然感染犬复孔绦虫的犬中获得了血清。这些犬患有眼部疾病，并被咨询是否要进行眼部结节的手术切除或眼球摘除。根据制造商的方案，使用 DiroCHEK®心丝虫抗原检测试剂盒（Synbiotics Corporation，Zoetis，Kalamazoo，MI，USA）对这些样本进行了三次重复检测，检测前和热处理后均进行了检测。样本在 103°C 的干热块中加热 10 分钟，然后以 1818×g 的速度离心 20 分钟。在总共 23 只犬中，无论是否经过热处理，19 只（82.6%）均未检测到抗原，3 只犬在热处理前后检测为阳性，只有 1 只犬在热处理后转为阳性。这 3 只在热处理前后均为阳性的犬被负责这些病例的兽医证实同时感染了犬恶丝虫，我们无法获得仅在热处理后转为阳性的那只犬的病史或后续信息。我们的数据表明，在使用 DiroCHEK®检测犬血清时，犬复孔绦虫感染不应导致假阳性，无论是否进行热处理。在 DiroCHEK®中检测到抗原阳性的具有临床眼部盘尾丝虫病的犬可能同时感染了犬恶丝虫，应进一步进行检测，包括血液微丝蚴检查和诊断影像学检查。如果确认存在心丝虫感染，应根据美国心丝虫协会或其他当地组织的指南，将动物纳入推荐的治疗方案。
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