Cytauxzoon felis is a tick-transmitted intraerythrocytic apicomplexan infecting felids in the southeastern and midwestern United States. Bobcats (Lynx rufus) are the natural wildlife reservoir of C. felis, where in enzootic areas prevalence can reach 100%. Domestic cats can be subclinically infected with C. felis or can develop cytauxzoonosis. Two studies have documented the presence of C. felis in domestic cats in Illinois; these studies have shown a limited number of cases submitted to specialty labs. During 2014–2018, we obtained blood samples collected by veterinary staff from 514 cats that were apparently healthy and 74 cats that were suspected of cytauxzoonosis. These samples were screened using a sensitive, nested PCR to detect the presence of C. felis DNA. We herein document frequent occurrences of cytauxzoonosis (8–15 cases/year from 4 veterinary clinics) and 12.5% prevalence of subclinical infections in southern Illinois, a locality showing a sharp increase in cases of cytauxzoonosis. Our results suggest a high risk of cytauxzoonosis in southern Illinois, despite only recently being recognized in the area. We found no specific risk factors for cytauxzoonosis or subclinical infections in this location. In addition, cases of cytauxzoonosis occur every month of the year (with the highest frequency in summer) and therefore tick prevention should be used in domestic cats in enzootic regions throughout the year.

Cytauxzoon felis是一种蜱传播的红细胞内顶端复合体，感染美国东南部和中西部的猫科动物。山猫（Lynx rufus ）是猫科动物的天然野生动物宿主，在地方性动物流行地区患病率可达100%。家猫可能会亚临床感染猫衣原体或可能出现细胞虫病。两项研究记录了伊利诺伊州家猫中存在C. felis ；这些研究表明，提交给专业实验室的案例数量有限。2014年至2018年期间，我们获得了兽医人员从514只明显健康的猫和74只疑似患有细胞虫病的猫身上采集的血液样本。使用灵敏的巢式 PCR 对这些样本进行筛选，以检测猫 C. felis DNA的存在。我们在此记录了伊利诺伊州南部细胞虫病的频繁发生（4 个兽医诊所每年 8-15 例）和 12.5% 的亚临床感染患病率，该地区的细胞虫病病例急剧增加。我们的结果表明，伊利诺伊州南部存在细胞虫病的高风险，尽管该地区最近才被认识到。我们在该地点没有发现细胞虫病或亚临床感染的特定危险因素。此外，一年中每个月都会发生细胞虫病病例（夏季发病率最高），因此对于地方性动物流行地区的家猫应全年进行蜱虫预防。