Departament de Biologia, Salut I Medi Ambient, Facultat de Farmacia, Universitat de Barcelona, Barcelona, Spain.
Laboratorio de Inmunopatología Clínica, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain.
Parasit Vectors. 2021 Mar 25;14(1):178. doi: 10.1186/s13071-021-04682-w.
Feline leishmaniosis is a vector-borne parasitic disease caused by Leishmania spp. Leishmania infection in dogs is prevalent in the Mediterranean basin, but in other animals, such as cats, it could also play a role in the epidemiology of the disease. Information on the geographical distribution and epidemiological features of L. infantum infection in cats is scarce, particularly in urban stray cats living in regions where canine leishmaniosis is endemic. As diagnosis can be challenging, combining different serological and molecular methods is a useful approach. Our aim was to investigate the prevalence of infection of L. infantum in apparently healthy stray cats in an endemic region of Spain (Zaragoza city) using serological and molecular methods, and to compare the results of the different techniques.
The prevalence of Leishmania infection was studied in stray cats captured in urban and peri-urban areas of Zaragoza. Blood was collected from each animal for serology and molecular analysis. Three serological methods, namely the immunofluorescent antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA) and western blot (WB), were used to detect L. infantum antibodies and a real-time PCR (qPCR) assay was used to detect L. infantum DNA. The results were analyzed by Fisher's exact test and Cohen's kappa statistic (κ) to assess the level of agreement between the diagnostic techniques.
Serological analysis of blood samples from 180 stray cats revealed 2.2% (4/179) Leishmania infection positivity by IFAT, 2.8% (5/179) by ELISA and 14.5% (26/179) by WB. Leishmania DNA was detected by qPCR in 5.6% (10/179) of the cats. Sixteen cats (8.9%) tested positive by only one serological technique and four tested positive by all three serological methods used. The overall rate of infected cats (calculated as the number of cats seropositive and/or qPCR positive) was 15.6%, and only two cats tested positive by all the diagnostic methods. A significant association was found between male cats and a positive qPCR result. Comparison of the techniques revealed a fair agreement in seropositivity between blood qPCR and IFAT (κ = 0.26), blood qPCR and ELISA (κ = 0.24), WB and ELISA (κ = 0.37) and WB and IFAT (κ = 0.40). The highest agreement between seropositive results was between IFAT and ELISA (κ = 0.89), and the lowest was between blood qPCR and WB (κ = 0.19). The prevalence of the feline leukemia virus antigen was 4.49% (8/178 cats) and that of the feline immunodeficiency virus (FIV) antibody was 6.74% (12/178), while co-infection with both retroviruses was observed in one female cat (1/178). Leishmania ELISA and IFAT seropositivity were statistically associated with FIV status by the chi-square test.
The results obtained in this study, using serological tests and qPCR, indicate the existence of L. infantum asymptomatic infection in apparently healthy stray cats in the city of Zaragoza, an endemic area in Spain.
猫利什曼病是一种由利什曼原虫引起的媒介传播寄生虫病。在犬类中，利什曼原虫感染在地中海盆地很普遍，但在其他动物（如猫）中，它也可能在疾病的流行病学中发挥作用。关于猫感染婴儿利什曼原虫的地理分布和流行病学特征的信息很少，特别是在犬利什曼病流行的城市流浪猫中。由于诊断可能具有挑战性，因此结合使用不同的血清学和分子方法是一种有用的方法。我们的目的是使用血清学和分子方法调查在西班牙（萨拉戈萨市）流行地区的明显健康的流浪猫中婴儿利什曼原虫感染的流行情况，并比较不同技术的结果。
在萨拉戈萨市的城市和城郊地区捕获的流浪猫中研究了利什曼原虫感染的流行情况。从每只动物采集血液进行血清学和分子分析。使用三种血清学方法，即免疫荧光抗体试验（IFAT）、酶联免疫吸附试验（ELISA）和 Western blot（WB），来检测婴儿利什曼原虫抗体，并使用实时 PCR（qPCR）检测婴儿利什曼原虫 DNA。通过 Fisher 精确检验和 Cohen's kappa 统计量（κ）来分析结果，以评估诊断技术之间的一致性水平。
对 180 只流浪猫的血液样本进行血清学分析显示，IFAT 检测出 2.2%（4/179）的利什曼原虫感染阳性，ELISA 检测出 2.8%（5/179）的利什曼原虫感染阳性，WB 检测出 14.5%（26/179）的利什曼原虫感染阳性。qPCR 在 5.6%（10/179）的猫中检测到利什曼原虫 DNA。16 只猫（8.9%）仅通过一种血清学技术检测呈阳性，4 只猫通过使用的三种血清学方法均呈阳性。感染猫的总体率（按血清学阳性和/或 qPCR 阳性的猫数计算）为 15.6%，只有两只猫通过所有诊断方法检测呈阳性。雄性猫与 qPCR 阳性结果之间存在显著关联。技术比较显示，qPCR 与 IFAT（κ=0.26）、qPCR 与 ELISA（κ=0.24）、WB 与 ELISA（κ=0.37）和 WB 与 IFAT（κ=0.40）之间的血清学阳性结果具有适度一致性。IFAT 与 ELISA 之间的阳性结果一致性最高（κ=0.89），qPCR 与 WB 之间的一致性最低（κ=0.19）。猫白血病病毒抗原的流行率为 4.49%（8/178 只猫），猫免疫缺陷病毒（FIV）抗体的流行率为 6.74%（12/178 只猫），而在一只雌性猫中观察到两种逆转录病毒的共同感染（1/178）。利什曼 ELISA 和 IFAT 血清学阳性与 FIV 状态通过卡方检验具有统计学关联。
本研究使用血清学检测和 qPCR 获得的结果表明，在西班牙流行地区的萨拉戈萨市，明显健康的流浪猫中存在婴儿利什曼原虫无症状感染。
