Cryptosporidiosis exhibits a relatively wide geographical distribution in Ireland with 58% and 18.3% of Electoral Divisions and Small Areas associated with at least one confirmed case during the study period, respectively. Crude Incidence Rates (CIRs) of infection indicate a moderately increasing trend, ranging from 9.8/100,000 in 2008 to 12.4/100,000 in 2017 [
10]. Most (59.3%) sporadic cases were associated with children ≤ 5 years, which concurs with several previous studies [
3,
7]. Within the ≤ 5 years cohort, cases were more frequently associated with male children (OR 1.3873), potentially reflecting the tendency of male children to mount weaker immune responses [
21], an enhanced susceptibility to environmental exposures via gender-related outdoor activities [
22], or a gender-related bias in healthcare-seeking behaviours [
23]. Conversely, female children were statistically associated with outbreak-related cryptosporidiosis, potentially reflecting higher levels of direct contact (and subsequent transmission) between parents/family members and female children [
24]. A recent small-scale investigation of the regional epidemiology of cryptosporidiosis in County Cork, Ireland, demonstrated moderately increased infection rates among 20–34-year olds, suggesting likely anthroponotic transmission via caregiver contact with infected children [
25]. Geographically, most sporadic cases (65.8%) occurred in categorically rural areas (χ
2 = 110.493, p < 0.001; Table
1), where approximately 37.3% of the Irish populace reside [
26]. A previous Scottish study by Pollock et al. similarly found
C. parvum infection was associated with areas characterised by lower human population density and a higher ratio of farms to humans, both indicators of rurality [
27]. While the current study represents the first nationwide study of the spatiotemporal epidemiology of cryptosporidiosis in Ireland, this finding was expected, and likely attributable to increased exposure to sources of
Cryptosporidium spp. oocysts in rural areas, including farmyard animals [
28], direct exposure to contaminated surface waters [
29] and the use of groundwater as a drinking water source [
6]. Conversely, urban areas exhibited a significantly higher secondary (OR 1.5383) and travel-related (OR 3.5742) case occurrence, likely indicative of
C. hominis infections as opposed to the agriculturally (rural) associated
C. parvum, however, as
Cryptosporidium spp
. is not identified within the Irish disease reporting system, this is somewhat speculative.