Abstract
Cryptosporidium parvum is a zoonotic protozoan parasite of human and veterinary public health concern that causes gastrointestinal disease. Animal contact is a major risk factor for C. parvum outbreaks which require thorough investigation through the use of molecular subtyping. Recently, a multi-locus variable-number tandem repeat analysis (MLVA) scheme was established for C. parvum, offering improved subtyping resolution compared to the commonly used single-locus 60 kDa glycoprotein gene (gp60) subtyping approach. Using the C. parvum MLVA scheme, the genetic diversity of known gp60 subtyped faecal DNA extracts collected between April 1st 2023 and March 31st 2024 was explored. A representative group of a common Scottish gp60 subtype (IIaA15G2R1, n = 28) was analysed by MLVA and found to consist of 8 distinct complete MLVA profiles, with 4-12-5-7-27-36-16 (n = 12) being the most common. Genetic diversity within samples involved in three historic animal contact outbreaks (Outbreaks A, B and C) was investigated. Outbreak A, involving a single gp60 subtype (IIaA19G1R1), consisted of only one MLVA profile (4-12-5-8-27-15-17). Outbreak B was caused by two gp60 subtypes (IIaA17G1R1 and IIaA15G2R1), which were further subdivided into four MLVA profiles, two per gp60 subtype (4-14-4-7-27-37-15 and 4-14-5-7-27-27-15, and 4-13-4-8-27-31-17 and 4-12-5-7-27-42-16, respectively). Lastly, Outbreak C, thought to have two-point sources of infection, involved one gp60 subtype (IIaA15G2R1), which was subdivided into four distinct MLVA profiles (4-12-5-7-27-36-16, 4-12-5-7-27-32-15, 4-12-5-7-27-30-15, and 4-14-5-7-36-33-15). Improved MLVA resolution allowed outbreak specimens with insufficient epidemiological data to be linked to a source through sharing a common MLVA profile.