Cryptosporidium infection is associated with reduced growth and diarrhoea in goats beyond weaning.

Cryptosporidium and Giardia are common parasites of ruminant livestock worldwide. These parasites are associated with diarrhoea outbreaks in young goats (pre-weaning), but the impacts on health and productivity for older goats (post-weaning) are not well understood. Here we show Cryptosporidium faecal shedding is associated with reduced growth and diarrhoea in goats aged approximately 9-15 months. Goats were sampled four times at one-month intervals. Faecal shedding for a range of pathogens were determined using quantitative PCR and sequencing (Cryptosporidium, Giardia, Eimeria, Salmonella, Campylobacter), and microscopy (trichostrongylid nematode worm egg count and Entamoeba). Cryptosporidium faecal shedding was associated with 1.5 kg lower growth for the one-month period following sampling. Specifically, C. xiaoi was associated with 1.9 kg lower growth in the following month. This is the first report of production impacts associated with C. xiaoi in ruminants older than 3 months of age. Cryptosporidium shedding was associated with an over 4-fold increase in risk of diarrhoea, with C. parvum associated with 10-fold and C. ubiquitum associated with 16-fold increase in risk of diarrhoea. Notably, C. xiaoi shedding was not associated with increased risk of diarrhoea. Giardia shedding was associated with looser faecal consistency, but not diarrhoea. Higher Eimeria oocyst counts were weakly associated with lower live weight, poorer body condition and looser faecal consistency. Shedding of other enteric pathogens were not associated with impacts on live weight, growth or diarrhoea risk. This study challenges the two notions that Cryptosporidium infections only impact health and productivity of goats during the pre-weaning period, and that Cryptosporidium (and specifically C. xiaoi) infections in the absence of diarrhoea are asymptomatic. Recognising the potential for impacts of Cryptosporidium infection on growth rates in the absence of diarrhoea will support improved design for experiments testing impacts of Cryptosporidium on ruminant health and production. Improved understanding of the role of protozoan infections on animal health has implications for the management of goats in order to reduce adverse impacts on farm profitability, animal welfare and public health risk.