# Investigating genetic diversity within Cryptosporidium parvum outbreaks using multi-locus variable number tandem repeat analysis

## TL;DR

Researchers used a new genetic method to better understand and track outbreaks of a parasite that causes gastrointestinal disease.

## Contribution

A multi-locus variable-number tandem repeat analysis (MLVA) scheme was applied to improve subtyping resolution of Cryptosporidium parvum.

## Key findings

- A common gp60 subtype (IIaA15G2R1) was found to contain eight distinct MLVA profiles.
- MLVA analysis revealed distinct genetic diversity within historic outbreaks linked to animal contact.
- MLVA provided improved resolution for linking outbreak specimens to sources compared to traditional gp60 subtyping.

## 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.

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•A multi-locus approach investigating genetic diversity of Cryptosporidium parvum gp60 subtypes.•Eight complete MLVA profiles were identified from a group of common gp60 subtype IIaA15G2R1.•Improved MLVA resolution enhanced outbreak investigation compared to gp60 analysis.

A multi-locus approach investigating genetic diversity of Cryptosporidium parvum gp60 subtypes.

Eight complete MLVA profiles were identified from a group of common gp60 subtype IIaA15G2R1.

Improved MLVA resolution enhanced outbreak investigation compared to gp60 analysis.