Determination of body temperature changes in mastitis mouse models is a core preclinical endpoint for quantifying the systemic febrile response triggered by intramammary lipopolysaccharide (LPS) or bacterial challenge. Using calibrated rectal thermometry, implantable temperature transponders, or infrared thermography, this assay generates objective ΔT data that support the efficacy evaluation of anti-inflammatory, antipyretic, and antibacterial candidates. All procedures are performed in accredited third-party laboratories under internationally recognized laboratory animal welfare and housing standards.
Technical Overview
Mastitis is the inflammation of the mammary gland, typically induced in laboratory mice by intramammary infusion of lipopolysaccharide (LPS) through the teat canal or by direct inoculation of pathogens such as Staphylococcus aureus or Escherichia coli. Following induction, the release of endogenous pyrogens such as interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and prostaglandin E2 drives a measurable rise in core body temperature. Determination of body temperature changes therefore provides a sensitive, quantitative, and non-terminal pharmacodynamic readout of the systemic inflammatory response.
In preclinical studies, the temperature change value (ΔT), peak temperature rise (Tmax), time to peak, and the area under the temperature–time curve (AUC) are used to characterize disease progression and to assess the antipyretic and anti-inflammatory efficacy of test articles. Measurements are conducted in environmentally controlled animal facilities compliant with GB 14925 (laboratory animal environment and housing facilities), and all protocols are subject to ethical review in accordance with GB/T 35892 and the 3Rs principles (replacement, reduction, refinement).
Testing Samples
Model Animals
Female specific-pathogen-free (SPF) mice, typically 8–10 weeks old and weighing 18–22 g, are used. Common strains include BALB/c, C57BL/6, ICR, and KM mice. Lactating mice (days 7–10 post-partum) or age-matched virgin females may be selected depending on the study design, since mammary gland responsiveness varies with physiological state.
Biological Specimens
- Abdominal and inguinal mammary gland tissue for histopathology and myeloperoxidase (MPO) activity assay
- Serum and plasma for cytokine quantification (TNF-α, IL-1β, IL-6) and complete blood counts
- Mammary tissue homogenates for bacterial load enumeration in infectious models
Test Articles
- Small-molecule anti-inflammatory and antipyretic drug candidates
- Antibiotic formulations intended for mastitis therapy
- Natural product extracts and traditional medicine preparations
- Functional feeds, probiotics, and immunomodulatory biologics
Testing Items
The testing panel covers both primary temperature endpoints and supporting inflammatory markers that contextualize the febrile response:
- Baseline core body temperature (°C) recorded over 2–3 consecutive days prior to model induction
- Dynamic core temperature profile at defined post-induction intervals (e.g., 0, 2, 4, 6, 8, 12, 24, and 48 hours)
- Temperature change (ΔT = Ttime point − Tbaseline), peak rise, time to peak, and temperature–time AUC
- Regional surface temperature of the inguinal and abdominal mammary area by infrared thermography
- Supporting endpoints: mammary injury score, histopathological grading (H&E staining), MPO activity, cytokine levels, and white blood cell differential counts
Testing Methods
Model Establishment
Mice are anesthetized and the teat canal of the fourth (inguinal) mammary gland is cannulated with a fine micro-syringe. LPS (for example 10–50 μg per gland dissolved in sterile saline) or a defined inoculum of S. aureus is infused gently to avoid ductal damage. Sham-operated controls receive sterile saline only. Following recovery, animals are returned to individually ventilated cages with ad libitum access to food and water.
Temperature Measurement Techniques
- Rectal probe thermometry: a lubricated digital probe is inserted to a fixed depth of approximately 1.0–1.5 cm for a standardized 10–15 seconds; instruments are calibrated and traceable to national metrology standards.
- Implantable transponder microchips: subcutaneously implanted identification transponders enable rapid, low-stress repetitive readings without restraint-induced artifacts.
- Infrared thermography: calibrated thermal cameras map surface temperature distribution over the mammary and inguinal region, providing spatial information on local inflammation, with reflected-temperature compensation performed in accordance with ASTM E1862 practice.
Measurement Schedule and Environmental Control
Animals undergo a 5–7 day acclimation period, during which handling habituation minimizes stress-induced hyperthermia. Baseline temperatures are recorded for at least three consecutive days. After induction, measurements follow the pre-defined time matrix, always performed by the same trained operator at consistent circadian times. The procedure room is maintained at 22 ± 2 °C with 50 ± 10% relative humidity and a 12 h/12 h light–dark cycle.
Data Processing and Statistics
ΔT values are expressed as mean ± SD. Group comparisons are analyzed using one-way or repeated-measures ANOVA followed by appropriate post hoc tests, with p < 0.05 considered statistically significant. Fever-inhibition rate is calculated as (ΔTmodel − ΔTtreated) / ΔTmodel × 100%. Raw data, calibration certificates, and complete analytical reports are archived under a auditable quality system.
Applications
Body temperature change determination in murine mastitis models is widely applied across pharmaceutical and biological research:
- Screening and efficacy confirmation of antipyretic and anti-inflammatory drug candidates
- Evaluation of antibiotics and novel antimicrobial strategies for mastitis therapy, with translational relevance to bovine mastitis control
- Pharmacodynamic studies of natural products, plant extracts, and traditional medicine formulations
- Mechanistic investigation of pyrogenic cytokine cascades and fever signaling pathways during mammary inflammation
- Safety pharmacology studies in which body temperature serves as a core safety endpoint
- Publications, regulatory submission support, and preclinical data packages prepared by accredited third-party laboratories
FAQ
Why is body temperature measured in a local inflammation model such as mastitis?
Although mastitis is initiated locally in the mammary gland, LPS and cytokines enter the systemic circulation and act on the hypothalamic thermoregulatory center. The resulting fever is an objective, dynamic, and quantifiable indicator of systemic inflammatory severity, making ΔT a reliable pharmacodynamic biomarker for antipyretic and anti-inflammatory interventions.
Which induction method is more appropriate, LPS or bacterial challenge?
LPS infusion produces a reproducible, non-infectious inflammatory and febrile response that is well suited to standardized efficacy testing. Live S. aureus or E. coli inoculation better mimics clinical infectious mastitis and supports bacterial load enumeration, but requires enhanced biosafety containment. The choice depends on the study objective.
How are stress-related artifacts avoided during measurement?
Handling habituation during acclimation, consistent operators, fixed insertion depth and dwell time, gentle restraint, and measurements taken at the same circadian phase collectively minimize handling-induced hyperthermia. Implantable transponders offer the lowest artifact burden for repeated measurements.
What magnitude of temperature rise is considered a successful febrile response?
A sustained increase of ≥ 0.8–1.0 °C above the individual baseline within 4–8 hours post-induction is generally accepted as evidence of successful febrile response, and a significant, dose-dependent reduction of ΔT in treated groups indicates antipyretic efficacy.
How long does a typical study take?
A standard study, including acclimation, baseline recording, model induction, 48-hour dynamic monitoring, and terminal specimen collection, is typically completed within 2–3 weeks, with an additional 1–2 weeks for histopathology and biochemical analysis.
How is animal welfare ensured?
All protocols are reviewed and approved by the institutional animal care and ethics committee, follow GB/T 35892 ethical review guidelines and GB 14925 housing standards, include humane endpoints, analgesia where appropriate, and minimum necessary group sizes consistent with the 3Rs principles.