Epidemiological consequences of reproductive senescence in a long-lived vector

长寿媒介生殖衰老的流行病学后果

• 批准号: BB/P006159/1
• 负责人: Sinead English
• 金额: $ 36.28万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FP006159%2F1
• 关键词: Epidemiological; consequences; reproductive; senescence; long

Tsetse flies transmit single-celled parasites - trypanosomes - to livestock with a single infectious bite. Once infected, the animal develops animal African trypanosomiasis (AAT), a fatal disease which kills 1-2 million cattle and costs sub-Saharan Africa 3-5 billion USD in lost agricultural potential each year. Strategies to control this disease are informed by mathematical models describing rates of parasite transmission between tsetse and hosts and changes in the numbers of tsetse. A crucial aspect of an insect's ability to transmit a disease-causing parasite is its longevity and susceptibility to infection. For a wide variety of animals, longevity and susceptibility to infection are affected by the investment made by an individual's mother. This maternal effect is likely to be very important for tsetse because of their unusual reproductive biology. Unlike most other insects, female tsetse get pregnant, lactate and give birth to live young, which weigh more than the mother. Tsetse can survive over six months in the field with females producing a single larva every ~10 days. The close link between an individual fly and its mother suggests that there will be a marked maternal effect on tsetse longevity and immunity and hence parasite transmission. Models for trypanosomiasis are based on the Ross-Macdonald model for human malaria, however, and do not consider the role of maternal investment in tsetse population dynamics or epidemiology as malaria mosquitoes - like most other vectors - reproduce through egg laying.This project will investigate how maternal investment changes with age and nutrition in tsetse, the consequences for offspring survival and ability to spread trypanosomes, and the contribution of these processes to tsetse population and disease transmission dynamics. We will conduct parallel observations of tsetse in the laboratory - using a large colony of flies at the Liverpool School of Tropical Medicine - and in the field, using flies of estimated age caught using an innovative sampling method in their natural habitat in Zimbabwe. We will experimentally manipulate nutrition in females and measure the costs of reproduction by preventing females from mating until they are older, to assess whether late-life declines in reproductive output (such as those reported in humans) reflect depleted resources or build-up of damage as a by-product of reproduction. We will develop new evolutionary models to understand whether such patterns represent adaptive strategies to maximize the total number of offspring produced in a lifetime, constraints due to physiology, or a combination of these processes.We will follow offspring born to mothers of varying age and nutritional state to test whether offspring born to older or nutritionally stressed mothers are more likely to die young or become infected by trypanosomes. We will also test whether maternal effects are stronger in sons than daughters. Finally, we will use insights from these experimental observations and evolutionary models to improve epidemiological models predicting the spread of tsetse-borne diseases. These diseases can persist at low prevalence and vector density, only to flare up when control efforts are relaxed or new habitats become suitable. Our new models will be used to predict the role of mothers in helping tsetse populations to persist or shift range as a result of human-related and environmental change. The accuracy of these models will be validated against existing data on the distribution and abundance of tsetse, their hosts and disease prevalence.

采采蝇通过一次感染性叮咬将单细胞寄生虫-锥虫-传播给牲畜。一旦被感染，动物就会发展出动物非洲锥虫病（AAT），这是一种致命的疾病，每年会导致1-2百万头牛死亡，并使撒哈拉以南非洲损失30 - 50亿美元的农业潜力。控制这种疾病的策略是通过数学模型来描述采采蝇和宿主之间的寄生虫传播率以及采采蝇数量的变化。昆虫传播致病寄生虫能力的一个关键方面是它的寿命和对感染的敏感性。对于各种各样的动物来说，寿命和感染的易感性受到个体母亲所做投资的影响。由于采采蝇不寻常的生殖生物学特性，这种母性效应可能对采采蝇非常重要。与大多数其他昆虫不同，雌性采采蝇怀孕、哺乳并生下活的幼崽，幼崽比母亲重。采采蝇可以在野外生存6个月以上，雌性每10天生产一只幼虫。个体苍蝇和它的母亲之间的密切联系表明，采采蝇的寿命和免疫力以及寄生虫的传播会受到明显的母体影响。然而，锥虫模型是基于人类疟疾的Ross-Macdonald模型，没有考虑采采蝇种群动态或流行病学中母体投资的作用，因为疟疾蚊子-像大多数其他媒介一样-通过产卵繁殖。本项目将调查采采蝇母体投资如何随年龄和营养而变化，对后代生存和传播锥虫能力的影响，以及这些过程对采采蝇种群和疾病传播动态的贡献。我们将在实验室中进行舌蝇的平行观察-使用利物浦热带医学院的一大群苍蝇-并在现场，使用估计年龄的苍蝇在津巴布韦的自然栖息地中使用创新的采样方法捕获。我们将实验性地操纵女性的营养，并通过阻止女性交配直到她们长大来测量生殖成本，以评估生殖输出的晚年下降（如人类报告的那些）是否反映了资源枯竭或作为生殖副产品的损害积累。我们将开发新的进化模型，以了解这种模式是否代表适应性策略，以最大限度地提高一生中产生的后代总数，由于生理学的限制，或这些过程的组合。我们将跟踪不同年龄和营养状态的母亲所生的后代，以测试是否更年长或营养紧张的母亲所生的后代更有可能过早死亡或被锥虫感染。我们还将测试母亲的影响是否在儿子身上比女儿更强。最后，我们将利用这些实验观察和进化模型的见解来改进预测采采蝇传播疾病传播的流行病学模型。这些疾病可以在低流行率和病媒密度的情况下持续存在，只有当控制工作放松或新的栖息地变得合适时才会突然爆发。我们的新模型将用于预测母亲在帮助采采蝇种群持续生存或因人类相关和环境变化而改变范围方面的作用。这些模型的准确性将根据采采蝇的分布和丰度、其宿主和疾病流行率的现有数据进行验证。

项目成果

Population Biology of Vector-Borne Diseases

媒介传播疾病的群体生物学

• DOI: 10.1093/oso/9780198853244.003.0010
• 发表时间: 2020
• 作者: English S

Incorporating effects of age on energy dynamics predicts nonlinear maternal allocation patterns in iteroparous animals.

• DOI: 10.1098/rspb.2021.1884
• 发表时间: 2022-02-23
• 期刊: Proceedings. Biological sciences
• 作者: Barreaux AMG;Higginson AD;Bonsall MB;English S
• 通讯作者: English S

Investigating the unaccounted ones: insights on age-dependent reproductive loss in a viviparous fly

调查不明原因：胎生果蝇年龄依赖性生殖损失的见解

• DOI: 10.3389/fevo.2023.1057474
• 发表时间: 2023
• 期刊: Frontiers in Ecology and Evolution
• 影响因子: 3
• 作者: English S

Population Biology of Vector-Borne Disease

媒介传播疾病的群体生物学

• 发表时间: 2020
• 作者: English S

Additional file 1: of Wing length and host location in tsetse (Glossina spp.): implications for control using stationary baits

附加文件 1：采采蝇（舌蝇属）的翅长和寄主位置：对使用固定诱饵进行控制的影响

• DOI: 10.6084/m9.figshare.7580573
• 发表时间: 2019
• 作者: Hargrove J