Examination of Horizontal Transmission of Nippostrongylus brasiliensis in Mice to Assess Biosecurity Risks

• Published in: Journal of the American Association for Laboratory Animal Science 2023-05, Vol.62 (3), p.243-253
• Main Authors: Floyd, Rebecca J, Ricart Arbona, Rodolfo J, Carrasco, Sebastian E, Lipman, Neil S
• Format: Article
• Language: English
• Subjects: Animals; Biosecurity; Female; Housing, Animal; Mice; Mice, Inbred C57BL; Mice, Inbred NOD; Mice, SCID; Nippostrongylus; Original Research; Rats
• ISSN: 1559-6109; 2769-6677
• DOI: 10.30802/AALAS-JAALAS-23-000004

Mice are commonly infected with Nippostrongylus brasiliensis (Nb) to study their immune responses. However, biosecurity measures have not been established for housing Nb infected mice and rats. Transmission reportedly does not occur when infected mice are cohoused with naive mice. To test this, we inoculated female NOD.Cg- Prkdc scid Il2rg tm1Wjl /Sz (NSG; n = 12) and C57BL/6J (B6; n = 12) mice with 750 Nb L 3 larvae. These mice were then cohoused with naïve NSG ( n = 24) and B6 ( n = 24) mice (1 infected and 2 naïve mice per cage (24 cages) for 28 d in static microisolation cages that were changed every 14 d. We also did several studies to determine the conditions that favor horizontal transmission. First, we assessed in vitro development to the L 3 stage of Nb egg-containing fecal pellets maintained under 4 environmental conditions (dry, moist, soiled bedding, and control). Second, we assessed infection of naïve NSG mice ( n = 9) housed in microisolation cages that contained soiled bedding spiked with infective L 3 larvae (10,000/cage). Third, we gavaged NSG mice ( n = 3) with Nb eggs to model the potential for infection after coprophagy. We found that naïve NSG (9 of 24) and B6 (10 of 24) mice cohoused with an infected cagemate passed Nb eggs in feces as early as 1 d after cohousing and intermittently thereafter for varying periods. This shedding was presumably the result of coprophagy because adult worms were not detected in the shedding mice at euthanasia. Although eggs developed in vitro into L 3 larvae under moist and control environmental conditions, none of the NSG mice housed in cages with L 3 -spiked bedding or gavaged with eggs became infected with Nb. These findings indicate that infectious horizontal transmission does not occur when mice are housed with Nb-shedding cage mates in static microisolation cages with a 14-d cage-changing interval. Results from this study can be used to inform biosecurity practices when working with Nb-infected mice.