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Mouse models for evaluation of virulence of Chlamydia psittaci isolated from ruminants
A Rodolakis1, F Bernard, F Lantier
1INRA Station de Pathologie de la Reproduction, Nouzilly, France.
Abstract:
Intestinal strains of Chlamydia psittaci isolated from faeces of clinically healthy sheep or goats were differentiated from pathogenic strains isolated from animals affected with chlamydial diseases by their virulence in mice. The invasiveness of strains after footpad inoculation was estimated in non-pregnant mice by recording the colonisation and the enlargement of the spleen on days 6 and 9 after inoculation. The abortifacient effect was judged by measuring the colonisation of placenta and fetuses of pregnant mice inoculated intravenously on day 11 +/- 1 of pregnancy. While 25 of 27 pathogenic strains were invasive and able to colonise placenta and fetuses, eight of 10 intestinal strains were not. The model permits graded differentiation between virulent and non-virulent strains and suggests that in propitious circumstances intestinal chlamydia could reach and colonise the placenta and disturb the pregnancy.
Insights
Intestinal Chlamydia psittaci strains from healthy animals are less virulent than pathogenic strains. A mouse model differentiated these strains, showing intestinal strains can potentially cause pregnancy complications.
Area of Science:
- Veterinary Microbiology
- Infectious Diseases
- Animal Reproduction
Background:
- Chlamydia psittaci is an important veterinary pathogen causing disease in livestock.
- Intestinal strains of C. psittaci are often isolated from healthy animals, but their pathogenic potential is unclear.
- Differentiating between pathogenic and non-pathogenic strains is crucial for disease control.
Purpose of the Study:
- To differentiate intestinal strains of Chlamydia psittaci from pathogenic strains using a mouse model.
- To assess the virulence and abortifacient potential of different C. psittaci isolates.
- To evaluate the utility of a mouse model for strain characterization.
Main Methods:
- Isolation of Chlamydia psittaci from faeces of healthy sheep/goats and diseased animals.
- Virulence assessment in mice via footpad inoculation (non-pregnant mice) and intravenous inoculation (pregnant mice).
- Evaluation of spleen colonization, placental, and fetal colonization to determine invasiveness and abortifacient effects.
Main Results:
- 25 out of 27 pathogenic strains were invasive and colonized placenta/fetuses.
- 8 out of 10 intestinal strains showed limited invasiveness and did not colonize placenta/fetuses.
- The mouse model allowed for graded differentiation between virulent and non-virulent strains.
Conclusions:
- A mouse model effectively differentiates virulent and non-virulent Chlamydia psittaci strains.
- While generally less virulent, intestinal C. psittaci strains possess the potential to cause reproductive harm under certain conditions.
- Further research is needed to understand the transmission dynamics and risks associated with intestinal C. psittaci in livestock.