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Factors generating aggregation of Heligmosomoides polygyrus (Nematoda) in laboratory mice
1Institute of Parasitology, McGill University, Ste-Anne de Bellevue, Quebec, Canada.
Abstract:
The importance of host heterogeneity in generating aggregation was investigated using Heligmosomoides polygyrus (Nematoda) in laboratory mice. Parameters of infection were compared between inbred and outbred mice, between primary and challenge infection protocols, and between gavage and natural exposure protocols, to investigate the relative effects of innate resistance, acquired resistance and behaviour, respectively. Heterogeneity in acquired resistance was identified as the most consistent factor leading to variability and aggregation of H. polygyrus numbers in mice. This hypothesis was supported in two experiments where groups of mice did not develop resistance to challenge infection (use of certain inbred strains of mice and immunosuppression with corticosteroids in the drinking water) and where variability in worm numbers after the challenge infection was comparable with that after the primary infection. Heterogeneity in host behaviour, particularly in behaviours enhancing skin contact with larvae, also was associated with increased heterogeneity in worm burden, though not as consistently as heterogeneity in acquired resistance. Surprisingly, worm burdens were not more variable in outbred compared with inbred mice. Our data suggest that the relative contributions of innate resistance, acquired resistance and behaviour in generating variable worm burdens are likely to vary spatially and temporally.
Insights
Host heterogeneity drives parasite aggregation. Acquired resistance in mice significantly impacts Heligmosomoides polygyrus (Nematoda) worm burden variability, more so than innate resistance or behavior.
Area of Science:
- Parasitology
- Immunology
- Animal Behavior
Background:
- Parasite infections often exhibit aggregated distributions, where a few hosts harbor most of the parasites.
- Understanding host factors contributing to this aggregation is crucial for parasite ecology and control.
Purpose of the Study:
- To investigate the role of host heterogeneity in generating aggregation of Heligmosomoides polygyrus (Nematoda) in laboratory mice.
- To compare the effects of innate resistance, acquired resistance, and host behavior on parasite burden variability.
Main Methods:
- Infection parameters of H. polygyrus were compared between inbred and outbred mice.
- Primary and challenge infection protocols were used.
- Gavage and natural exposure routes were compared to assess innate resistance, acquired resistance, and behavior.
Main Results:
- Heterogeneity in acquired resistance was the most consistent factor causing variability and aggregation of H. polygyrus.
- Experiments with non-resistant mice (specific inbred strains, corticosteroid immunosuppression) showed challenge infection variability similar to primary infection.
- Host behavior, particularly behaviors increasing larval contact, also contributed to worm burden heterogeneity, but less consistently than acquired resistance.
Conclusions:
- Acquired resistance heterogeneity is a primary driver of H. polygyrus aggregation in mice.
- Worm burdens were not more variable in outbred versus inbred mice, contrary to expectations.
- The relative contributions of innate resistance, acquired resistance, and behavior to parasite burden variability can change over space and time.