Mastitis is an important constraint to milk production in pastoralist camel (Camelus dromedarius) herds in Kenya. The objective of this study was to investigate the prevalence, risk factors, and bacterial panorama of subclinical mastitis (SCM) in pastoralist camel herds in Isiolo County, Kenya. Furthermore, antimicrobial susceptibility in udder pathogens was studied. A cross-sectional sample of 206 camels from 20 milking herds was screened using the California Mastitis Test (CMT), and quarter milk was subjected to bacterial culturing. Isolates were confirmed using MALDI-TOF mass spectrometry analysis, and antimicrobial susceptibility was determined using the broth microdilution method. Interviews focusing on herd management were conducted with camel owners. Subclinical mastitis, defined as a CMT score ≥ 3 (scale 1 to 5) and absence of clinical symptoms in the udder, were present in all visited herds. On the individual level, 46% of the camels had at least 1 quarter affected with SCM, and on the quarter level the prevalence was 26%. Intramammary infections (IMI) were common; out of 798 quarter milk samples, 33% yielded conclusive bacterial growth. The sensitivity and specificity of CMT for correctly identifying quarters with IMI were 82% and 92%, respectively. The most prevalent pathogen was Streptococcus agalactiae (72% of IMI-positive quarters), followed by non-aureus staphylococci (19%) and Staphylococcus aureus (13%). Antimicrobial susceptibility testing revealed that only a low proportion (4.9%) of Strep. agalactiae isolates was sensitive to tetracycline. For Staph. aureus, 59.1% of isolates exhibited sensitivity to penicillin. Skin lesions on the teats or udder were a risk factor for SCM. Increased age, parity, and stage of lactation were associated with increased risk of both SCM and IMI. Older camels with a blind teat or a previous history of mastitis were more likely to be infected with Strep. agalactiae. Hygiene routines for milking were largely absent in the observed herds, and knowledge of adequate milk handling was limited. The poor udder health is likely to depend on multiple factors, most prominently the within-herd maintenance of contagious udder pathogens, in combination with difficult sanitary conditions and lack of awareness among camel keepers. This study showed that in pastoralist camel herds around Isiolo town, SCM and IMI specifically caused by Strep. agalactiae are common udder health problems and are associated with increasing age, parity, and stage of lactation, and skin lesions on the teats and udder. Resistance to tetracycline in Strep. agalactiae was common. Control strategies specifically targeting SCM and adapted to pastorally managed camel herds need to be developed to reduce disease, combat antimicrobial resistance, and improve the livelihoods of pastoralists.

中文翻译：

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肯尼亚伊西奥洛的牧民奶牛场中的亚临床乳腺炎：患病率，危险因素和抗菌药敏感性。

乳腺炎是肯尼亚牧民骆驼（Camelus dromedarius）牛群牛奶生产的重要限制。这项研究的目的是调查肯尼亚Isiolo县牧民骆驼群的亚临床乳腺炎（SCM）的患病率，危险因素和细菌概况。此外，还对乳房病原体中的抗生素敏感性进行了研究。使用加利福尼亚乳腺炎测试（CMT）筛选了来自20个挤奶牛群的206头骆驼的横截面样本，并对四分之一牛奶进行了细菌培养。使用MALDI-TOF质谱分析法确认了分离物，并使用肉汤微稀释法确定了抗生素敏感性。与骆驼主人进行了以牧群管理为重点的访谈。亚临床乳腺炎 被定义为CMT得分≥3（等级1至5）且乳房中无临床症状的动物，均出现在所有探访的牛群中。在个体方面，有46％的骆驼受SCM感染的比例至少为四分之一，在四分之一水平上，患病率为26％。乳房内感染（IMI）很常见。在798个季度的牛奶样本中，有33％的细菌最终生长。CMT正确识别IMI季度的敏感性和特异性分别为82％和92％。最普遍的病原体是无乳链球菌（IMI阳性季度的72％），其次是非金黄色葡萄球菌（19％）和金黄色葡萄球菌（13％）。抗菌药敏试验表明，只有低比例（4.9％）的链球菌。无乳杆菌分离株对四环素敏感。对于葡萄球菌。金黄色，59。1％的分离株对青霉素具有敏感性。乳头或乳房的皮肤病变是SCM的危险因素。年龄，胎次和哺乳阶段的增加与SCM和IMI的风险增加有关。患有盲人奶嘴或有乳腺炎病史的骆驼更容易感染链球菌。无乳。在观察到的牛群中，挤奶的卫生程序基本不存在，并且对挤奶的充分了解有限。不良的乳房健康很可能取决于多种因素，最主要的是传染性乳房病原体的群内维持，加上卫生条件恶劣和骆驼饲养者缺乏意识。这项研究表明，在Isiolo镇附近的牧民骆驼群中，SCM和IMI专门由链球菌引起。无乳杆菌是常见的乳房健康问题，与年龄，胎次，泌乳阶段的增加以及奶头和乳房的皮肤损害有关。对链球菌的四环素有抗性。无乳头很常见。需要制定专门针对SCM并适应牧区​​管理的骆驼群的控制策略，以减少疾病，抵抗抗菌素耐药性并改善牧民的生计。