Happi Anise N, Toepp Angela J, Ugwu C A, Petersen Christine A, Sykes Jane E
Department of Veterinary Pathology, University of Ibadan, Ibadan, Nigeria.
College of Public Health, Center for Emerging Infectious Diseases, University of Iowa, Iowa City, Iowa, USA.
Vet Parasitol Reg Stud Reports. 2018 Jan;11:55-60. doi: 10.1016/j.vprsr.2017.12.002. Epub 2017 Dec 19.
Many sick dogs brought to the University of Ibadan Veterinary Teaching Hospital (UIVTH) are infested with ticks and are anemic. Up until recently, light microscopy (LM) has been the only available means used for detection of blood-borne infections. In other parts of the world, PCR-based assays been used as a gold standard for accurate diagnosis of blood-borne infections. In this study, we used LM and broad-spectrum rRNA gene PCR-based assays on 116 blood samples from dogs brought to the UIVTH for detection of the 18S rRNA gene of Babesia and the 16S rRNA genes of Ehrlichia and hemotropic mycoplasmas. The relationship between clinicopathological findings and PCR results was evaluated. Age, sex, presence of ticks, anemia, co-infection status, and fever were also assessed in relation to PCR positivity to determine the risk factors using stepwise logistic regression analyses. Light microscopic examination revealed an overall prevalence of infection of 14.7% (17/116). Organisms detected were Babesia canis (3.5%), Ehrlichia canis (10.3%) and Trypanosoma congolense (0.9%) and a single co-infection with Babesia canis and Ehrlichia canis (0.9%). PCR analysis revealed 89/116 (76.7%) positive samples. Infections with 1, 2 and 3 infectious agents occurred in 49 (55.1%), 36 (40.4%) and 4 (4.5%) samples, respectively. Specifically, among the 89 PCR positive samples, Babesia spp. (85.4%) was the most abundant infection followed by Ehrlichia spp. (46.1%) and hemoplasmas (13.5%). Sequencing of PCR products identified two samples (1.7%) that contained Hepatozoon canis DNA. Sequencing of hemoplasma positive samples identified 'Candidatus Mycoplasma haemobos' in 0.8% of dogs. Using PCR, a 5-fold higher prevalence of blood-borne infections was found in the dogs (76.7%, 89/116) than with LM (14.7%, 17/116) alone" Dogs between 1 and 12months were the most frequently infected with multiple agents (47.2% double and 50.0% triple infections). Male dogs had the highest prevalence of infection (80.4%) and more triple infections (75.0%). A total of 57.3% of infected dogs were anemic. Anemic dogs were 2.77 times more likely to test positive for Ehrlichia spp. (OR: 2.77 95% CI: 1.25-6.16) and dogs with ticks were 3.6 times more likely to test positive for hemoplasmas (OR=3.60 95% CI: 1.05-12.38). This study underscores the abundance of blood-borne infections in dogs in Ibadan, Nigeria, which is underestimated using light microscopy. This is also the first evidence of existence of 'Candidatus Mycoplasma haemobos' in a dog in Nigeria and in Africa. Consequently there is a need for molecular diagnostic facilities for routine screening of sick animals, as multiple infections were not found by light microscopy.
许多被带到伊巴丹大学兽医教学医院（UIVTH）的患病犬都感染了蜱虫且患有贫血。直到最近，光学显微镜检查（LM）一直是检测血源感染的唯一可用方法。在世界其他地区，基于PCR的检测方法已被用作准确诊断血源感染的金标准。在本研究中，我们对116份来自UIVTH的犬血样进行了LM和基于广谱rRNA基因PCR的检测，以检测巴贝斯虫的18S rRNA基因、埃立克体和嗜血性支原体的16S rRNA基因。评估了临床病理结果与PCR结果之间的关系。还评估了年龄、性别、蜱虫感染情况、贫血、合并感染状况和发热与PCR阳性之间的关系，以使用逐步逻辑回归分析确定危险因素。光学显微镜检查显示总体感染率为14.7%（17/116）。检测到的病原体有犬巴贝斯虫（3.5%）、犬埃立克体（10.3%）和刚果锥虫（0.9%），以及一例犬巴贝斯虫和犬埃立克体的合并感染（0.9%）。PCR分析显示89/116（76.7%）的样本呈阳性。感染1、2和3种感染因子的样本分别有49（55.1%）、36（40.4%）和4（4.5%）例。具体而言，在89份PCR阳性样本中，巴贝斯虫属（85.4%）是最常见的感染，其次是埃立克体属（46.1%）和支原体（13.5%）。PCR产物测序鉴定出两份样本（1.7%）含有犬肝簇虫DNA。支原体阳性样本测序在0.8%的犬中鉴定出“犬血支原体”。使用PCR检测发现，犬血源感染的患病率（76.7%，89/116）比单独使用LM检测（14.7%，17/116）高5倍。1至12个月大的犬最常感染多种病原体（47.2%为双重感染，50.0%为三重感染）。雄性犬的感染患病率最高（80.4%），三重感染更多（75.0%）。共有57.3%的感染犬患有贫血。贫血犬检测埃立克体属呈阳性的可能性是正常犬的2.77倍（OR：2.77，95%CI：1.25 - 6.16），感染蜱虫的犬检测支原体呈阳性的可能性是正常犬的3.6倍（OR = 3.60，95%CI：1.05 - 12.38）。本研究强调了尼日利亚伊巴丹犬血源感染的普遍性，光学显微镜检查低估了这种情况。这也是尼日利亚和非洲犬中存在“犬血支原体”的首个证据。因此，由于光学显微镜检查未发现多重感染，需要分子诊断设施对患病动物进行常规筛查。
