Cache Valley Virus (CVV) is an arbovirus transmitted between mosquitos and several vertebrate species, including small ruminants. Infections in adult sheep and goats is generally subclinical, but infection during pregnancy is a growing animal welfare issue as it can result in embryo or pregnancy loss, fetal malformation, and dystocia. Diagnosis in fetal tissue or neonates is made using serologic or molecular testing. Serologic diagnosis in the dam can indicate past infection but does not confirm CVV infection in the fetus. ARS first noted clinical signs of possible CVV during the Nov/Dec 2015 lambing; first seropositive dam was identified in Jan 2021. To estimate incidence of CVV infections among ewes bred from 2019-2023 and lambing in Jan/Feb (n = 185), adverse pregnancy outcome such as embryo loss, birth of dead, deformed, or weak lambs, were used as surrogate markers. The relationship of animal BW (ewes at breeding and post-breeding; lambs at birth and ~60 d of age), dam age, lamb outcome, and breeding year were compared by likely CVV infection status. To estimate seroprevalence in ewes and correlate serology results with pregnancy outcomes, serum was collected from ewes (n = 46) exposed to rams in Aug 2022 at 0 (first day of ram exposure) and ~60 d later. Tissue from aborted or dead lambs and serum from live lambs exhibiting signs of CVV (swollen joints, parrot mouth, deformities) were collected. Serum was screened for neutralizing antibodies using a CVV-specific plaque reduction neutralization test using a 50% cut-off (PRNT50). For this preliminary analysis, specimens with PRNT50 antibody titers ≥ 10 were considered positive. Tissue specimens were tested using bunyavirus and CVV RT-PCR. Data were analyzed by GLM (SAS). Using surrogate markers, an estimate of incidence of CVV during pregnancy was 26.5 ± 2.9% without year differences (P = 0.16) or age (yearling vs older ewes, P = 0.44). There was no association between CVV and dam BW (P > 0.10), number of live+dead lambs born, but CVV possibly reduced number of live lambs by 18% (P = 0.02) and those weaned by 27% (P = 0.002). Live litter birth (CVV, P < 0.001) and weaning BW (CVV × year, P = 0.04) were reduced by CVV. Of 42 ewes bred in Aug 2022, 9 (21%) had a positive titer in Aug (pre-pregnancy) indicating possible past infection, 3 (11%) seroconverted in Oct, indicating possible infection during pregnancy. Of those, 2 (6.7%) had adverse pregnancy outcomes, including one stillbirth with deformities that had a positive RT-PCR on kidney tissue. Further studies are needed to determine whether CVV is becoming more widely prevalent in small ruminants, as are new technologies for early detection and prevention.

中文翻译：

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57 卡什谷病毒对阿肯色州羊群的影响

卡什谷病毒 (CVV) 是一种在蚊子和多种脊椎动物（包括小型反刍动物）之间传播的虫媒病毒。成年绵羊和山羊的感染通常是亚临床的，但怀孕期间的感染是一个日益严重的动物福利问题，因为它可能导致胚胎或妊娠丢失、胎儿畸形和难产。胎儿组织或新生儿的诊断是通过血清学或分子检测进行的。母鼠的血清学诊断可以表明过去的感染情况，但不能确认胎儿是否感染 CVV。ARS 在 2015 年 11 月/12 月产羔期间首次注意到可能存在 CVV 的临床症状；2021 年 1 月发现了第一只血清阳性母羊。旨在估计 2019-2023 年繁殖和 1 月/2 月产羔的母羊 (n = 185) CVV 感染的发生率、不良妊娠结局，如胚胎丢失、死胎、畸形或虚弱的出生羔羊被用作替代标记。通过可能的 CVV 感染状态比较动物体重（配种时和配种后的母羊；出生时和约 60 日龄的羔羊）、损伤年龄、羔羊结果和繁殖年份的关系。为了估计母羊的血清阳性率并将血清学结果与妊娠结局相关联，从 2022 年 8 月 0 日（公羊暴露的第一天）和约 60 天后暴露于公羊的母羊 (n = 46) 中收集了血清。收集流产或死亡羔羊的组织以及表现出 CVV 症状（关节肿胀、鹦鹉嘴、畸形）的活羔羊的血清。使用 CVV 特异性噬菌斑减少中和试验，使用 50% 截止值 (PRNT50) 筛选血清中的中和抗体。对于此初步分析，PRNT50 抗体滴度 ≥ 10 的样本被视为阳性。使用布尼亚病毒和CVV RT-PCR 测试组织样本。数据通过 GLM (SAS) 进行分析。使用替代标记，妊娠期间 CVV 发生率估计为 26.5 ± 2.9%，无年份差异 (P = 0.16) 或年龄差异（一岁母羊与老年母羊，P = 0.44）。CVV 与母羊体重 (P > 0.10)、生羔羊活羊数和死羔羊数量之间没有关联，但 CVV 可能使活羔羊数量减少 18% (P = 0.02)，断奶羔羊数量减少 27% (P = 0.002) ）。CVV 降低了活产仔数（CVV，P < 0.001）和断奶体重（CVV × 年，P = 0.04）。在 2022 年 8 月繁殖的 42 只母羊中，9 只（21%）在 8 月（怀孕前）滴度呈阳性，表明可能过去感染，3 只（11%）在 10 月出现血清转化，表明可能在怀孕期间感染。其中，2 例 (6.7%) 出现不良妊娠结局，其中 1 例死产畸形且肾组织 RT-PCR 呈阳性。需要进一步的研究来确定 CVV 是否在小型反刍动物中变得更加普遍，以及早期检测和预防的新技术。