Table 1.

Introducing variation to the laboratory mouse during helminth infections.

Variable	Observation	References
Diet	Protein deprivation enhances susceptibility to T. muris and H. polygyrus accompanied by a reduced Type 2 immune response, in one study strain-dependent	[88,127,128]
	Zinc deficient mice suffer prolonged infections with gut nematode infections and depressed Type 2 immune responses	[89,129,130]
	A high fat diet leads to increased resistance to T. muris infection and reduced Type 1 responses	[90]
	Fermentable dietary fibre prevents expulsion of T. muris and heightens the Type 1 response	[91]
	During protein deprivation, co-infection affected parasite survival and fitness via host immunity	[131]
Age	18−28 months old mice are less able to clear gut nematode infections and have reduced Type 2 immune responses compared to 3 month old mice	[28,132]
Sex	Female mice are more resistant to T. muris infection associated with elevated Type 2 cytokines	[26]
	BALB/c female mice are more susceptible to L. sigmodontis infection	[133]
Genetics	Inbred strains of mice differ in their ability to expel gut nematode infections	[27,134,135,136]
	Resistance to helminth infection is associated with genes within the Major Histocompatibility complex
Microbiome	Helminths can upregulate microbiota-derived short chain fatty acids correlating with reduced Type 2 immune responses and increase regulation	[137]
	N. brasiliensis infection reduced segmented filamentous bacteria, reducing Th17 responses via a Type 2 mechanism	[138]
	During a high fat diet, H. polygyrus induces gut microbiota changes via a Type 2 immune response, affecting obesity	[139]
	H. polygryus ameliorates viral lung pathology via a microbiome dependent upregulation in Type 1 interferons	[140]
	Multiple helminth species enrich the bacterial species Lactobacillaceae with varied outcomes on worm persistence according to the helminth species	[65,66,67,68,69,70,141]
	Genetic and sex differences impact on how the gut microbiota responds to helminth infection	[142]
Infection history	Single high dose infection of between 100−400 T. muris eggs results in a dominant Type 2 immune response and worm expulsion in most mouse strains	[135]
	Low dose infection (<50 eggs) results in a Type 1 immune response and susceptibility to T. muris infection	[143]
	Repeated low dose (“trickle”) infections enables a build-up of Type 2 immunity and ultimately worm expulsion; though outcome is influenced by genetic background	[44,143]
	Strain-dependent, trickle infections with H. polygyrus result in a declining worm burden after several weeks	[144,145]
	Helminth co-infections shapes immune response to future infectious challenges	[146,147,148]

Underlined further variables altered beyond the main variable denoted on the left-hand side.