Efficacies of prevention and control measures applied during an outbreak in Southwest Madrid, Spain

Leishmaniasis is a vector-borne disease of worldwide distribution, currently present in 98 countries. Since late 2010, an unusual increase of human visceral and cutaneous leishmaniasis cases has been observed in the south-western Madrid region, totaling more than 600 cases until 2015. Some hosts, such as human, domestic dog and cat, rabbit (Oryctolagus cuniculus), and hare (Lepus granatensis), were found infected by the parasite of this disease in the area. Hares were described as the most important reservoir due to their higher prevalence, capacity to infect the vector, and presence of the same strains as in humans. Various measures were adopted to prevent and control the disease, and since 2013 there was a slight decline in the human sickness. We used a mathematical model to evaluate the efficacy of each measure in reducing the number of infected hosts. We identified in the present model that culling both hares and rabbits, without immediate reposition of the animals, was the best measure adopted, decreasing the proportion of all infected hosts. Particularly, culling hares was more efficacious than culling rabbits to reduce the proportion of infected individuals of all hosts. Likewise, lowering vector contact with hares highly influenced the reduction of the proportion of infected hosts. The reduction of the vector density per host in the park decreased the leishmaniasis incidence of hosts in the park and the urban areas. On the other hand, the reduction of the vector density per host of the urban area (humans, dogs and cats) decreased only their affected population, albeit at a higher proportion. The use of insecticide-impregnated collar and vaccination in dogs affected only the infected dogs’ population. The parameters related to the vector contact with dog, cat or human do not present a high impact on the other hosts infected by Leishmania. In conclusion, the efficacy of each control strategy was determined, in order to direct future actions in this and in other similar outbreaks. The present mathematical model was able to reproduce the leishmaniasis dynamics in the Madrid outbreak, providing theoretical support based on successful experiences, such as the reduction of human cases in Southwest Madrid, Spain.

利什曼病（Leishmaniasis）是一种全球分布的虫媒传染病，目前已在98个国家流行。自2010年末起，西班牙马德里西南部地区出现人类内脏利什曼病与皮肤利什曼病病例异常增多的情况，截至2015年累计报告病例超600例。该区域已检出感染该疾病病原体——利什曼原虫（Leishmania）的宿主包括人类、家犬、家猫、穴兔（Oryctolagus cuniculus）以及格拉纳达野兔（Lepus granatensis）。由于格拉纳达野兔的感染率更高、具备感染媒介昆虫的能力，且携带与人类相同的病原体菌株，因此被认定为该地区最主要的储存宿主。当地已采取多项疾病防控措施，自2013年起人类病例数出现小幅下降。本研究采用数学模型评估各项措施在减少感染宿主数量方面的防控效能。模型分析结果显示，扑杀野兔与穴兔且不进行即时补栏，是当前已采取的最优防控措施，可降低所有宿主的感染比例。具体而言，扑杀野兔相较于扑杀穴兔，更能有效降低各类宿主的感染个体占比。同样，减少媒介昆虫与野兔的接触，也可显著降低感染宿主的比例。降低公园内单位宿主对应的媒介昆虫密度，可同时降低公园与城区宿主的利什曼病发病率。反之，降低城区（人类、家犬、家猫）单位宿主对应的媒介昆虫密度，仅能减少该区域受影响的种群，尽管其降幅比例更高。使用杀虫剂浸渍项圈以及为家犬接种疫苗，仅对受感染的家犬种群有效。与家犬、家猫或人类相关的媒介接触参数，对其他感染利什曼原虫的宿主群体并未产生显著影响。综上，本研究明确了各项防控策略的实际效能，可为本次及其他类似暴发疫情的后续防控工作提供科学指导。本数学模型成功复现了马德里暴发疫情中的利什曼病传播动态，基于西班牙马德里西南部地区人类病例减少的成功实践，为该类疾病的防控工作提供了理论支撑。