Clinical and subclinical infections with Cryptosporidium in animals

Cryptosporidium spp. are frequent parasites of livestock and companion animals, raising questions about the clinical significance of such infections. Cryptosporidium infections have a wide spectrum of clinical signs that can vary from asymptomatic to serious infection to death. In neonatal ruminants, cryptosporidiosis is considered an important disease characterised by diarrhoea and mortality. In companion animals most infections are asymptomatic but severe clinical illness has also been reported in dogs, cats and horses. In birds, three main clinical forms of cryptosporidiosis are primarily seen in naturally occurring infections, i.e. respiratory, intestinal, and renal. In reptiles, cryptosporidiosis is an emerging problem given that infections are frequently chronic and lethal. Molecular tools have been developed to detect and differentiate Cryptosporidium at the species/genotype and subtype levels. The use of those tools has led to a more in-depth understanding of the genetic diversity of Cryptosporidium which plays an important role in the diverse clinical presentations of cryptosporidiosis. This review presents an overview of the current knowledge on clinical cryptosporidiosis in livestock, pets, and other animals.