Lithuanian University of Health Sciences, Institute of Microbiology and Virology, Lithuania, Tilžės str. 18, 47181, Kaunas, Lithuania.
National Food and Veterinary Risk Assessment Institute, National Food and Veterinary Risk Assessment Institute, J. Kairiūkščio str. 10, 08409, Vilnius, Lithuania.
Acta Vet Scand. 2021 Mar 20;63(1):12. doi: 10.1186/s13028-021-00577-z.
Rabies vaccination of wildlife carnivores is a powerful tool to prevent, control and eliminate rabies. The presence of neutralizing rabies antibodies in blood is considered a reliable indicator of adequate vaccination. The main purpose of the present study was to analyze the seroprevalence of specific antibodies in target populations of Lithuanian red fox (RF) and raccoon dog (RD) during the oral rabies vaccination (ORV) campaigns during the 2010-2019 period.
Over the ten-year period, 7,261 RF and 2,146 RD sera samples were collected post-mortem in field conditions and tested using a commercial standardized enzyme-linked immunosorbent assay (ELISA) kit in Lithuania. In the ORV spring and autumn vaccination periods, 31.8% (20.3-43.4 95% CI - 95% confidence interval) and 31.7% (21.2-42.1 95% CI) of RF, and 34.1% (22.5-45.7 95% CI) and 34.7% (22.7-46.7 95% CI) of RD sera samples, respectively, were identified as ELISA-positive (seroconversion ≥ 0.5 EU/mL-Equivalent Units per Millilitre). The seroprevalence analysis in adult/ juvenile animal subpopulations indicated that 34.9% (27.2-42.5 95% CI) and 29.2% (20.3-37.9 95% CI) of RF, and 35.6% (25.2-46.0 95% CI) and 30.6% (20.2-40.9 95% CI) of RD sera samples, respectively, were identified as ELISA-positive (seroconversion ≥ 0.5 EU/mL). Statistically strong determinate correlations (r) between the serological results (pos.%) in RF adult/juvenile animal subpopulations (r = 0.937) and between RF and RD positive seroconvert (pos.%) sera samples during the spring vaccinations (r = 0.864) were demonstrated. In different ORV periods, 14-29% of RF and 7-25% of RD sera samples were identified as ELISA-negative (seroconversion < 0.5 EU/mL), but with low (0.125 < 0.49 EU/mL) antibody (Abs) titres.
The 2010-2019 ORV programme has been an effective tool in both RF and RD populations in Lithuania. The rabies-free status of Lithuania was self-declared in 2015 with only three rabies cases identified in buffer zones since then. The percentage of ELISA-positive serum samples (seroconversion ≥ 0.5 EU/mL) during the different periods of vaccination was similar in RF and RD populations-32% and 34% respectively. The identified seroconversion average of 21.5% in RF and 16% in RD sera samples were officially identified as ELISA-negative (seronversion < 0.5 EU/mL), but with low 0.125 < 0.49 EU/mL Abs titres. That low, but positive seroconversion participated in the formation of populations overall immune status and can influence the interpretation of oral vaccination efficacy.
对野生动物肉食动物进行狂犬病疫苗接种是预防、控制和消除狂犬病的有力工具。血液中中和狂犬病抗体的存在被认为是充分接种疫苗的可靠指标。本研究的主要目的是分析 2010-2019 年期间立陶宛红狐（RF）和浣熊犬（RD）目标人群在口服狂犬病疫苗接种（ORV）期间的特定抗体血清阳性率。
在十年期间，在立陶宛现场条件下从死后收集了 7261 份 RF 和 2146 份 RD 血清样本，并使用商业标准化酶联免疫吸附测定（ELISA）试剂盒进行了测试。在 ORV 春季和秋季接种期间，分别有 31.8%（20.3-43.4%95%置信区间）和 31.7%（21.2-42.1%95%置信区间）的 RF，以及 34.1%（22.5-45.7%95%置信区间）和 34.7%（22.7-46.7%95%置信区间）的 RD 血清样本被鉴定为 ELISA 阳性（血清转化率≥0.5 EU/mL-等效单位/毫升）。对成年/未成年动物亚群的血清阳性率分析表明，分别有 34.9%（27.2-42.5%95%置信区间）和 29.2%（20.3-37.9%95%置信区间）的 RF，以及 35.6%（25.2-46.0%95%置信区间）和 30.6%（20.2-40.9%95%置信区间）的 RD 血清样本被鉴定为 ELISA 阳性（血清转化率≥0.5 EU/mL）。在 RF 成年/未成年动物亚群的血清学结果（阳性%）之间（r=0.937）和 RF 和 RD 阳性血清转化率之间（r=0.864）之间表现出统计学上很强的确定性相关性。在不同的 ORV 期间，14-29%的 RF 和 7-25%的 RD 血清样本被鉴定为 ELISA 阴性（血清转化率<0.5 EU/mL），但抗体（Abs）滴度较低（0.125<0.49 EU/mL）。
2010-2019 年 ORV 计划一直是立陶宛 RF 和 RD 种群的有效工具。自 2015 年以来，立陶宛宣布自己处于无狂犬病状态，此后仅在缓冲区发现了 3 例狂犬病病例。在不同的接种期，RF 和 RD 人群中 ELISA 阳性血清样本的百分比（血清转化率≥0.5 EU/mL）相似，分别为 32%和 34%。在 RF 和 RD 血清样本中，分别有 21.5%和 16%的血清转化率被官方认定为 ELISA 阴性（血清转化率<0.5 EU/mL），但 Abs 滴度较低（0.125<0.49 EU/mL）。这种低但阳性的血清转化率参与了种群整体免疫状态的形成，并可能影响口服疫苗接种效果的解释。
