Epidemiology of cryptosporidiosis in farm livestock, assessment of zoonotic risk and development of control strategies (PhD)

Outcomes

1.  A nssm-PCR was developed which enables quick and easy differentiation of Cryptosporidium species most commonly found in cattle. This PCR can simultaneously identify up to four different Cryptosporidium species (C. andersoni, C. ryanae, C. parvum and C. bovis) it can also be used to identify other Cryptosporidium species (by sequence analysis) where none of the cattle-adapted species have been detected.

2. In the first six weeks of life all calves on the study farm tested positive for Cryptosporidium, the most common species detected in this age group of cattle was parvum. In older calves (3 & 9 months of age) the most common species found were C. ryanae and C. bovis however at 6 months of age the most common species detected was C. parvum. This was not the same genotype which was found in the younger calves.

3. This study found that the majority (<85%) of adult cows shed parvum although most of the cows were shedding a different genotype than the calves. Despite this it is possible that the adult cattle are still a potential source from which the young calves may be infected. During this study a more sensitive method for detection of Cryptosporidium in adult cattle (and other ruminants) was developed.

4. We found that animals become less susceptible to disease if they do not encounter Cryptosporidium until they are older. If animals are kept parasite free for the first 6 weeks of life then the disease caused by Cryptosporidium is much less severe and many animals do not have scour at We also found that the different subtypes of parvum can cause differing disease. One subtype was associated with more scour in the infected animals than the other and the disease started sooner and lasted longer. The other subtype did not cause such severe disease but the infected animals produced more oocysts in their faeces.

The Challenge

Cryptosporidiosis is a parasitic disease which infects animals and humans. This disease is of great importance to the UK livestock industry as Cryptosporidium infected animals may suffer from diarrhoea, loss of appetite and dehydration leading to poor growth rates and, in severe cases even death. Some species of Cryptosporidium may be passed from animals to humans by direct contact or indirectly, often through contaminated water.

The Project

This study will examine livestock in Scotland to determine which species and strains of Cryptosporidium infect cattle, some of which may be infective to humans. This information may identify certain strains that are linked to more severe cases of disease in livestock. The study will also look at the methods farmers currently use to prevent and control the disease and determine which are the most effective.

Information arising from this project will be communicated to farmers to help encourage best practise in prevention and control of cryptosporidiosis in livestock.

Aims & Objectives

1. To develop new typing tools (multiplex PCR) to distinguish Cryptosporidium species commonly found in cattle samples 2
2. To assess the shedding profile of Cryptosporidium species and genotypes found in calves on a study farm
3. To assess the role of adult cattle in the transmission and persistence of Cryptosporidium parvum on a study farm
4. To assess the host-pathogen interactions involved in animals given serial experimental challenges with distinct Cryptosporidium parvum isolates

Student

Sarah Thomson