Host factors in determining resistance to cryptosporidiosis in cattle

Cryptosporidium parasites are the most important cause of enteric disease in young cattle in UK and worldwide and are also one of the leading causes of infant diarrhoea in humans [1]. Neonatal calves are very vulnerable to cryptosporidiosis resulting in significant morbidity due to severe diarrhoea and dehydration and there are increasing reports of mortality. Cryptosporidiosis is a challenge to control as infected animals shed billions of infective, long lived oocysts into the environment and these are a source of infection for other animals as well as people. The disease has emerged as an increasing problem in beef suckler units, and livestock industry leaders are very concerned about the lack of safe and effective treatments or vaccines available to help prevent and control cryptosporidiosis and have given their strong support for this proposal.
Our understanding of the host-pathogen interactions that determine disease outcome is limited. Neonatal calves are very vulnerable to infection and often exhibit clinical disease, whereas older calves are more resistant. The factors involved in determining this age-related susceptibility are unclear and this project aims to address the host factors involved in resistance to cryptosporidiosis by applying novel and innovative in vivo, ex vivo and in vitro technologies to examine in detail the host parasite interaction during acute infection and recovery in calves.
One of the constraints for improving our understanding of the factors that determine disease resistance has been the lack of simple research systems that permit the detailed analysis of host parasite interactions. The rodent model is an acknowledged poor comparator for clinical disease in cryptosporidiosis in particular, and the capability for culturing Cryptosporidium parasites in vitro is very limited. This project aims to tackle these gaps in capability by utilising a combination of in vivo and in vitro bovine systems to assess innate and adaptive cellular immune responses and examine the interaction of Cryptosporidium with gut epithelial cells. In addition, innovative 3D bovine gut organoid in vitro culture systems will be applied to enable a detailed analysis of host parasite interactions in the bovine gut epithelium. Data derived from the experimental studies will be validated by comparison to similar data obtained from naturally infected calves on a study farm.
This project will provide the fullest exploration yet of how cattle resist infection with Cryptosporidium parasites. A detailed account of the host responses involved will provide an important knowledge platform that will enable the development of vaccines to aid disease prevention and the identification of relevant biomarkers that will enable selective breeding programmes to improve resilience. In addition, the development of novel in vitro bovine systems would revolutionise our capability to study host-pathogen interactions with Cryptosporidium minimising the need for use of animal models.
Outputs from the project will be of interest to the animal health industry, livestock producers, environmental and public health workers and to academic researchers. The development of effective control strategies will have a significant impact on the sustainable efficiency of animal production, safeguard food security, improve animal health and welfare, reduce waste and environmental contamination and improve public and environmental health.
[1] Streipen B (2013) Nature 503:189

Cryptosporidium is a major cause of enteric disease in livestock. Our understanding of the host-pathogen interactions determining disease outcome is very limited. A notable aspect of bovine cryptosporidiosis is that neonatal calves are highly susceptible and often develop clinical disease, whereas older calves become infected but do not exhibit pathology. The factors underpinning this age-related susceptibility are very unclear, and this project aims to address the host factors involved in resistance to cryptosporidiosis. A significant current impediment for bovine cryptosporidiosis is the lack of a useful and relevant experimental model system to facilitate detailed analysis of host-parasite interaction. The rodent is a poor comparator for clinical disease in ruminants, and the ability to culture Cryptosporidium in vitro is limited. This project aims to tackle these gaps in capability and analyse in detail the innate and adaptive immune responses to Cryptosporidium infection in neonatal (< 1 week) and 6 week old cattle. We will (i) analyse the key cell-mediated immune responses during in vivo infections of naive calves (ii) analyse by confocal microscopy the initial host-parasite interaction in vitro using ex vivo derived epithelial primary cells from calves (iii) analyse host cell gene expression changes in response to parasite invasion and initial replication in the primary gut cells (iv) apply a 3D bovine gut organoid in vitro system to analyse the host-parasite interaction and explore the potential of propagating parasites in vitro and (v) examine translation of findings from experimental systems to a cohort of calves in the field. Outputs from the project will greatly improve our understanding of cattle resistance to cryptosporidiosis, informing vaccine development and breeding strategies and establishing an in vitro system that could revolutionise our capability to study relevant host-parasite interactions with Cryptosporidium.

Cryptosporidiosis is the most important cause of enteric disease in young cattle in UK and worldwide and has also been cited as one of the leading causes of infant diarrhoea in humans by the WHO [1]. It is a neglected disease and there are no safe effective treatments or vaccines available to help prevent and control cryptosporidiosis. In discussions the applicants had with livestock producers leading to this proposal, farmers reported increased incidences of severe cryptosporidiosis within beef suckler units in Scotland. Beef industry leaders are very concerned about the lack of control options and have given their unreserved backing to this proposal in a letter of support.
The outputs from our project will make it possible to understand the host factors involved in determining resistance of cattle to cryptosporidiosis, which is essential to enable the development of prevention and control strategies based on vaccination and use of specific biomarkers in breeding programmes. In addition, infected livestock shed billions of parasites into the environment, resulting in an important source of infection for people and other animals. Cryptosporidium oocysts will survive for long periods in the environment and are resistant to normal water disinfection treatments and therefore pose significant economic and public health issues for water companies and governments.
Who might benefit from our project?
The outputs from our project will bring significant benefits to a wide range of different stakeholder groups. These include: those engaged in research involving protozoan parasites, bovine immunology and in vitro technologies applied to further our understanding of infectious disease; livestock producers from the dairy and beef industries; associated livestock health industries; environmental agencies, public health bodies; water companies; governments and policy makers and the public.
How might these stakeholders benefit from our project?
The research will be of great interest to academics in related scientific fields as the project will considerably improve our understanding of disease pathogenesis and host resistance to cryptosporidiosis in a relevant target host species. The application of innovative in vitro 3D culture technologies to enable detailed analysis of host-pathogen interactions in farm animal species will be of significant interest to researchers working to prevent and control infectious diseases of livestock and has the potential to substantially minimise the use of large animals in experiments going forward. We also wish to provide training for early career scientists in this area of research. Activity 1: Host international workshop on use of in vitro technologies to progress infectious disease research in livestock species.
The livestock industry in UK, and further afield, will benefit from the knowledge gained from our project by using new scientific evidence to direct resources effectively towards prevention and control strategies to tackle cryptosporidiosis. Outputs from the project will enable and target further work to test the feasibility of vaccination and using specific biomarkers to develop breeding programmes for improved resilience of livestock. We will also provide advice to livestock producers on managing Cryptosporidium infection on the farm. Activity 2: Host Industry day to discuss outputs from the project and identify collaborative areas going forward. Activity 3: Conduct on farm roadshow meetings in collaboration with farming organisations.
Policy makers, public health, environment and water companies will benefit from knowledge gained on how to control cryptosporidiosis on farms as this will reduce the resultant environmental contamination bringing economic and health benefits. Activity 4: Develop web-based materials and fact sheets on cryptosporidiosis prevention and control.
[1] Streipen B (2013) Nature 503: 189