Characterisation of field tropical Theileriosis and associated risk factors in two bioclimatic areas of Algeria

IF 3.1 2区医学 Q2 INFECTIOUS DISEASES

Ticks and Tick-borne Diseases Pub Date : 2024-01-19 DOI:10.1016/j.ttbdis.2024.102310

Tahar Kernif , Bachir Medrouh , Zoubir Harrat , Fairouz Saidi , Hocine Ziam

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引用次数: 0

Abstract

Tropical theileriosis (TT) is a tick-borne disease caused by Theileria annulata and commonly infects cattle in tropical and subtropical regions, including Algeria. It is a significant obstacle to cattle breeding programs established to improve production in Algeria. The present investigation aimed to estimate the current molecular prevalence, risk factors, and genetic characterisation of T. annulata in two bioclimatic areas of Algeria. In a cross-sectional study, 679 blood samples (629 from healthy cattle selected on farms and 50 from diseased cattle identified by veterinarians) were collected from the humid (n = 307+50) and semi-arid (n = 322) areas and screened by blood smear examination followed by polymerase chain reaction targeting cytochrome oxidase subunit 3 (cox III) mitochondrial and the 18S ribosomal RNA (18S rRNA) genes for Theileria spp. Seventy-six positive samples (56 clinically healthy and 20 with clinical signs) for Theileria spp. were confirmed to be T. annulata by the merozoïtes surface antigen-1 (Tams1) gene showing a rate of 8.9 % in clinically healthy and 40.0 % in suspected cattle. Among the 307 bloods samples collected from healthy cattle in the humid area, 25 cattle (8.1 %) were positive for T. annulata. Of the 322 healthy cattle from the semi-arid site, 31 (9.6 %) were carriers of T. annulata DNA. In subclinical population, demographic and environmental parameters analysis indicated that T. annulata infection was higher in adult crossbred cattle raised in the intensive and semi-intensive system (P<0.001). The multiple logistic regression analysis showed that age, breed, farming system, and bioclimatic area are potential risk factors for T. annulata infection in cattle (P<0.05). Multiple alignments of cox III sequences of T. annulata showed high heterogeneity with 25 polymorphic sites (nucleotide diversity π = 0.02402), resulting in two haplotypes with a low genetic diversity index (Hd) of 0.533. The 18S rRNA sequence alignment revealed only one T. annulata genotype with 100 % identity to the strains isolated from cattle and ticks in Mediterranean and Asian countries. Our preliminary results will serve as a basis for further studies on the genetic diversity and molecular epidemiology of T. annulata.

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阿尔及利亚两个生物气候区的野外热带毛癣菌病特征及相关风险因素

热带蜱虫病（TT）是由环状蜱虫引起的一种蜱媒疾病，通常感染热带和亚热带地区（包括阿尔及利亚）的牛。这种疾病严重阻碍了阿尔及利亚为提高产量而制定的养牛计划。本调查旨在估算目前阿尔及利亚两个生物气候区环状丝虫病的分子流行率、风险因素和遗传特征。在一项横断面研究中，从潮湿地区（n = 307+50）和半干旱地区（n = 322）收集了 679 份血液样本（629 份来自农场挑选的健康牛，50 份来自兽医确认的病牛），通过血液涂片检查，然后进行聚合酶链反应，以细胞色素氧化酶亚单位 3 (cox III) 线粒体和 18S 核糖体 RNA (18S rRNA) 基因为目标，筛查环状丝虫病。76 份阳性样本（56 份临床健康，20 份有临床症状）通过梅氏表面抗原-1（Tams1）基因证实为环状丝虫，临床健康牛的阳性率为 8.9%，疑似牛的阳性率为 40.0%。在潮湿地区从健康牛身上采集的 307 份血样中，有 25 头牛（8.1%）对环状丝虫病呈阳性反应。在半干旱地区的 322 头健康牛中，31 头（9.6%）是环状酪氨酸梭菌 DNA 携带者。在亚临床人群中，人口统计学和环境参数分析表明，在集约化和半集约化系统中饲养的成年杂交牛感染环口丝菌的比例更高（P<0.001）。多元 Logistic 回归分析表明，年龄、品种、养殖系统和生物气候区是牛感染环尾丝虫的潜在风险因素（P<0.05）。环斑蓟马 cox III 序列的多重比对显示出高度异质性，有 25 个多态位点（核苷酸多样性 π = 0.02402），形成两个遗传多样性指数（Hd）为 0.533 的低单倍型。18S rRNA序列比对结果显示，只有一个T. annulata基因型与从地中海和亚洲国家的牛和蜱中分离出来的菌株具有100%的相同性。我们的初步结果将为进一步研究环斑蜱的遗传多样性和分子流行病学奠定基础。

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来源期刊

Ticks and Tick-borne Diseases INFECTIOUS DISEASES-MICROBIOLOGY

CiteScore

6.90

自引率

12.50%

发文量

185

审稿时长

6-12 weeks

期刊介绍： Ticks and Tick-borne Diseases is an international, peer-reviewed scientific journal. It publishes original research papers, short communications, state-of-the-art mini-reviews, letters to the editor, clinical-case studies, announcements of pertinent international meetings, and editorials. The journal covers a broad spectrum and brings together various disciplines, for example, zoology, microbiology, molecular biology, genetics, mathematical modelling, veterinary and human medicine. Multidisciplinary approaches and the use of conventional and novel methods/methodologies (in the field and in the laboratory) are crucial for deeper understanding of the natural processes and human behaviour/activities that result in human or animal diseases and in economic effects of ticks and tick-borne pathogens. Such understanding is essential for management of tick populations and tick-borne diseases in an effective and environmentally acceptable manner.