Calves with cryptosporidiosis do not just carry one parasite. Using an optimized 18S rRNA metabarcoding workflow, Cryptosporidium in calves turned out to go together with a reorganized eukaryotic gut community. Mammal-blocking primers paired with a V8 primer set lowered host reads by 30 to 50 percent, and the infected animals showed less eukaryotic richness and a different community makeup. Why the calf gut eukaryome stays largely unmeasured Cryptosporidium parvum is an apicomplexan parasite, and the diarrhea it causes is a major economic and production problem for the livestock industry. The cost shows up in treatment and in animals that never reach their expected weight. What sits outside that cost calculation…