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Background: 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. Methods: 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 cutoffs. 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. Results: Three kits (TOXO-MS, NCS-MS and NCC) showed almost perfect agreement (kappa > 0.901) with immunoblot results when the cutoffs 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. Conclusions: 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.

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IntroductionNeospora caninum is an important cause of abortion in cattle worldwide. Infection in cattle occurs horizontally by ingestion of oocysts shed by canids or vertically, from an infected dam to the fetus, and may result in abortion, stillbirth, or birth of seropositive offspring. The control of bovine neosporosis is difficult and costly. The objectives of this study were to estimate the current nationwide seroprevalence of N. caninum infections in Swiss cattle and to assess risk factors for infection with this parasite.MethodsWe conducted a cross-sectional study with cattle farms randomly selected and stratified according to population size, resulting in a sample of 780 female cattle. The cattle originated from 161 farms distributed over all Switzerland. The serum samples were tested for antibodies against N. caninum using a commercial ELISA and if inconclusive, retested using an in-house immunoblot technique. To collect farm parameters relevant to N. caninum transmission and prevention, farm owners were mailed a questionnaire which addressed topics putatively related to N. caninum infection such as husbandry, history of abortion, and presence of dogs on farm. Univariate analysis by generalized linear mixed model (with animal seropositivity as outcome variable) and logistic regression modeling (with farm seropositivity as outcome variable) was conducted on farm parameters investigated in the questionnaire.ResultsBy ELISA and immunoblot, 4.2% (33/780) of cattle sera yielded positive results. At the farm level, 16.2% (26/161) of the sampled farms had at least one seropositive animal. The return rate of the valid questionnaires was 54.0%. At the animal level, odds for farm seropositivity were 3.8 times higher when rodents had been recorded by the farmer as a problem on the farm. At the farm-level, two protective factors were identified: rearing of replacement heifers and feeding of concentrated feed.ConclusionWe recorded a low seroprevalence of N. caninum in a random sample of Swiss cattle representative for the years 2017–2018. Based on a questionnaire survey, we could identify risk and protective factors for infection with N. caninum, however their biological relevance needs to be confirmed in further studies.