Institute of Parasitology, Vetsuisse-Faculty, University of Bern, Länggassstrasse 122, 3012, Bern, Switzerland.
Clinic for Ruminants, Vetsuisse-Faculty, University of Bern, Bremgartenstrasse 109a, 3012, Bern, Switzerland.
Parasit Vectors. 2020 May 14;13(1):256. doi: 10.1186/s13071-020-04128-9.
Little is known about the epidemiology of Toxoplasma gondii and Neospora caninum infections in alpacas (Vicugna pacos) and llamas (Lama glama) outside South America. The study aimed to estimate the seroprevalence of T. gondii and N. caninum infections in South American camelids (SAC) in Switzerland, to optimize serological tests for SAC and to identify risk factors, which may favour infection.
A total of 571 sera from 132 Swiss farms (374 alpacas and 197 llamas, mean 4.3 animals/farm) were obtained. Four commercial enzyme-linked immunosorbent assays (ELISA) for detecting antibodies against T. gondii (ID Screen Toxoplasmosis Indirect (TOXO-MS)) or N. caninum (i.e. ID Screen Neospora caninum Indirect Multi-species (NCS-MS); ID Screen Neospora caninum Competition (NCC) and ID Screen Neospora caninum Indirect (NCS)) were first assessed for their use on SAC comparing their results with those in immunoblot, and optimizing cut-offs. Subsequently, two kits (TOXO-MS and NCS-MS) were selected for seroprevalence estimation. Additionally, a risk factor analysis for infection was performed on 41 farms, which agreed to participate in a web-based survey.
Three kits (TOXO-MS, NCS-MS and NCC) showed almost perfect agreement (kappa > 0.901) with immunoblot results when the cut-offs were optimized, and one kit (NCS) proved not to be useful for detecting N. caninum seropositive SAC. By TOXO-MS ELISA, 82.3% (308/374) of the alpacas and 84.8% (167/197) of the llamas were seropositive for T. gondii, and 131/132 (99.2%) farms had seropositive animals. By NCS-MS ELISA, 3.5% (13/374) of the alpacas and 2.5% (5/197) of the llamas evidenced antibodies against N. caninum, and 9.1% (12/132) of the farms had seropositive animals. The variables "age" and "female sex" were identified as risk factors for T. gondii infection and "absence of cats in the farm during the last two years" as a protective factor. No risk or protective factors for N. caninum infection could be identified.
This nationwide cross-sectional study demonstrated for the first time the presence of antibodies against T. gondii and N. caninum in the Swiss SAC population, highlighting a high seroprevalence for T. gondii, the presence of cats as a risk factor and suggesting that SAC meat might represent an additional infection source for humans.
关于南美的以外地区羊驼（Vicugna pacos）和骆马（Lama glama）中弓形虫（Toxoplasma gondii）和新生隐球菌（Neospora caninum）感染的流行病学知识甚少。本研究旨在评估瑞士南美的以外地区骆驼（South American camelids，SAC）中弓形虫和新生隐球菌感染的血清流行率，优化针对 SAC 的血清学检测，并确定可能有利于感染的风险因素。
从瑞士的 132 个农场中获得了 571 份血清（374 份羊驼和 197 份骆马，平均每个农场 4.3 份）。最初评估了 4 种用于检测针对弓形虫的抗体的商业酶联免疫吸附测定（ELISA）（ID Screen Toxoplasmosis Indirect (TOXO-MS)）或新生隐球菌的抗体（即 ID Screen Neospora caninum Indirect Multi-species (NCS-MS)；ID Screen Neospora caninum Competition (NCC) 和 ID Screen Neospora caninum Indirect (NCS)），将它们的结果与免疫印迹进行比较，并优化了截断值，以评估其在 SAC 上的应用。随后，选择了两种试剂盒（TOXO-MS 和 NCS-MS）进行血清流行率估计。此外，对同意参与网络调查的 41 个农场进行了感染风险因素分析。
当优化截断值时，三种试剂盒（TOXO-MS、NCS-MS 和 NCC）与免疫印迹结果具有几乎完美的一致性（kappa>0.901），一种试剂盒（NCS）证明对检测新生隐球菌血清阳性的 SAC 没有用。通过 TOXO-MS ELISA，82.3%（308/374）的羊驼和 84.8%（167/197）的骆马对弓形虫呈血清阳性，132/132（99.2%）的农场都有血清阳性动物。通过 NCS-MS ELISA，3.5%（13/374）的羊驼和 2.5%（5/197）的骆马有抗新生隐球菌的抗体，132/132（91.6%）的农场有血清阳性动物。“年龄”和“雌性”被确定为弓形虫感染的风险因素，“过去两年农场内无猫”为保护因素。未发现新生隐球菌感染的风险或保护因素。
这项全国性的横断面研究首次证明了瑞士 SAC 群体中存在针对弓形虫和新生隐球菌的抗体，突出了弓形虫的高血清流行率、猫作为风险因素的存在，并表明 SAC 肉可能成为人类的另一个感染源。
