Relationships between diarrhoea and immune response to infection with gastrointestinal helminths in Merino sheep

In Merino sheep, I studied how infection with gastrointestinal worms induced responses in the immune system that might cause diarrhoea. Some aspects of the immune response, particularly immunoglobulin A (an antibody), seem to be responsible for inhibiting the growth and reproduction of worms. Other aspects, particularly immunoglobulin E, TNF-a (a cytokine) and eosinophils (a type of white blood cell), seem to promote worm expulsion from the gut by causing diarrhoea. My observations suggest that immune factors, especially if measured after winter infection, could be included in breeding programs to produce sheep that are resistant to both worms and diarrhoea.