Genetic uniqueness of Cryptosporidium parvum from dairy calves in Colombia

Fecal specimens from 432 pre-weaned calves younger than 35 days were collected over a 2-year period (2010-2012) from 74 dairy cattle farms in the central area of Colombia. These samples were microscopically examined for the presence of Cryptosporidium oocysts, and positive specimens were selected for molecular examination. Microscopy revealed that 115 calves (26.6%) from 44 farms (59.5%) tested positive. Oocyst shedding was recorded in calves aged 3-day-old onwards, although the infection rate peaked at 8-14 days (40.7%). Infection rates were higher in diarrheic (52.2%) than in non-diarrheic calves (19.9%) (p < 0.0001, χ²), and infected calves had up to seven times more probability of having diarrhea than non-infected calves. Cryptosporidium species and subtypes were successfully identified in 73 samples from 32 farms. Restriction and sequence analyses of the SSU rRNA gene revealed C. parvum in all but two isolates identified as Cryptosporidium bovis. Sequence analyses of the 60-KDa glycoprotein (gp60) gene revealed eight subtypes within the IIa family. An unusual subtype (IIaA18G5R1) was the most prevalent and widely distributed (more than 66% specimens and 68% farms) while the subtype most frequently reported in cattle worldwide (IIaA15G2R1) was found in less than 13% of specimens and 16% farms. The remaining subtypes (IIaA16G2R1, IIaA17G4R1, IIaA20G5R1, IIaA19G6R1, IIaA20G6R1, and IIaA20G7R1) were restricted to 1-3 farms. This is the first large-sample size study of Cryptosporidium species and subtypes in Colombia and demonstrates the genetic uniqueness of this protozoan in cattle farms in this geographical area.