Beck Ana, Huber Doroteja, Polkinghorne Adam, Kurilj Andrea Gudan, Benko Valerija, Mrljak Vladimir, Reljić Slaven, Kusak Josip, Reil Irena, Beck Relja
Department of Veterinary Pathology, Faculty of Veterinary Medicine, University of Zagreb, Vjekoslava Heinzela 55, 10000, Zagreb, Croatia.
Centre for Animal Health Innovation, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, 4556, Brisbane, Australia.
Parasit Vectors. 2017 Apr 4;10(1):168. doi: 10.1186/s13071-017-2106-8.
Babesia spp. and Theileria spp. are important emerging causes of disease in dogs. Alongside these domesticated hosts, there is increasing recognition that these piroplasms can also be found in a range of wild animals with isolated reports describing the presence of these pathogen in foxes (Vulpes vulpes) and captive grey wolves (Canis lupus). The prevalence and impact of these infections in free-ranging populations of canids are unknown. To gain a better insight into the epidemiology and pathogenesis of piroplasm infections in free-ranging grey wolves, pathological and molecular investigations into captive and free-ranging grey wolves in Croatia were performed.
The carcasses of 107 free-ranging wolves and one captive wolf were the subjects of post-mortem investigations and sampling for molecular studies. A blood sample from one live captured wolf for telemetric tracking was also used for molecular analysis. PCR amplification targeting the 18S RNA gene revealed that 21 of 108 free-ranging wolves and one captive animal were positive for Theileria/Babesia DNA. Subsequent sequencing of a fragment of the 18S RNA gene revealed that 7/22 animals were positive for Babesia canis while the other amplified sequence were found to be identical with corresponding 18S rDNA sequences of Theileria capreoli isolated from wild deer (15/22). Haematological and cytological analysis revealed the presence of signet-ring shaped or pear-shaped piroplasms in several animals with the overall parasite burden in all positive animals assessed to be very low. Pathological investigation of the captive animal revealed fatal septicemia as a likely outcome of hemolytic anaemia. There was little or no evidence of hemolytic disease consistent with babesiosis in other animals.
Importantly, the presence of B. canis in free-ranging grey wolves has not been described before but has been reported in a single fox and domestic dogs only. That B. canis infections cause disease in dogs but have little impact on wolf health possibly suggests that the wolf is the natural and the domestic dog is a secondary host. Surprisingly, the frequent finding of Theileria capreoli in wolves suggests that this Theileria species is not restricted to ungulates (cervids) but commonly infects also this carnivore species. Nevertheless, the potential role that these asymptomatically infected animals may play in the dispersal of these pathogens to susceptible sympatric species such as domesticated dogs requires further investigation.
巴贝斯虫属和泰勒虫属是犬类重要的新发疾病病因。除了这些家养宿主外，人们越来越认识到这些梨形虫也能在一系列野生动物中发现，有单独报道描述了这些病原体在狐狸（赤狐）和圈养灰狼（犬属）中的存在情况。这些感染在自由放养的犬科动物种群中的流行情况和影响尚不清楚。为了更好地了解自由放养灰狼中梨形虫感染的流行病学和发病机制，对克罗地亚圈养和自由放养的灰狼进行了病理学和分子研究。
107只自由放养狼和1只圈养狼的尸体是尸检调查和分子研究采样的对象。从1只用于遥测追踪而活捉的狼身上采集的一份血样也用于分子分析。针对18S RNA基因的PCR扩增显示，108只自由放养狼中的21只和1只圈养动物的泰勒虫属/巴贝斯虫属DNA呈阳性。随后对18S RNA基因片段进行测序，结果显示22只动物中有7只为犬巴贝斯虫阳性，而其他扩增序列与从野生鹿分离的泰勒虫属的相应18S rDNA序列相同（22只中有15只）。血液学和细胞学分析显示，几只动物中存在印戒形或梨形梨形虫，所有阳性动物的总体寄生虫负荷评估为非常低。对圈养动物的病理学调查显示，致命性败血症可能是溶血性贫血的结果。在其他动物中几乎没有或没有与巴贝斯虫病相符的溶血性疾病证据。
重要的是，犬巴贝斯虫在自由放养灰狼中的存在此前尚未有描述，但仅在1只狐狸和家养犬中报道过。犬巴贝斯虫感染在犬中会导致疾病，但对狼的健康影响很小，这可能表明狼是自然宿主，而家养犬是中间宿主。令人惊讶的是，在狼中频繁发现泰勒虫属，这表明该泰勒虫属物种不仅限于有蹄类动物（鹿科动物），也通常感染这种食肉动物物种。然而，这些无症状感染动物在将这些病原体传播给易感同域物种（如家养犬）中可能发挥的潜在作用需要进一步研究。
