Mycoplasma Infection in Rats: Treatment and Prevention

Understanding Mycoplasma in Rats

What is Mycoplasma pulmonis?

Mycoplasma pulmonis is a cell‑wall‑deficient bacterium belonging to the class Mollicutes. It infects the upper and lower respiratory tracts of laboratory rats and other rodents, establishing a persistent colonization that can progress to disease.

The organism exhibits the following features:

Pleomorphic cells ranging from 0.2 µm to 0.5 µm in diameter.
Lack of a rigid peptidoglycan layer, rendering it resistant to β‑lactam antibiotics.
Genome of approximately 1 Mb, encoding proteins essential for adherence and immune evasion.
Ability to attach to ciliated epithelial cells via specialized surface proteins.

Pathogenicity arises from chronic inflammation of the respiratory mucosa. The bacterium induces hyperplasia of bronchial epithelium, peribronchiolar lymphoid infiltrates, and, in severe cases, pneumonia with alveolar consolidation. The infection often persists subclinically, serving as a reservoir for transmission within colonies.

Transmission occurs primarily through direct contact, aerosolized droplets, and contaminated bedding. Prevalence is high in breeding facilities lacking strict biosecurity measures; infection rates can exceed 70 % in unmanaged colonies.

Clinical signs include:

Nasal discharge and sneezing.
Labored breathing, especially during exertion.
Weight loss and reduced growth in juvenile animals.
Occasional otitis media secondary to eustachian tube involvement.

Diagnosis relies on a combination of methods:

Culture on specialized mycoplasma media under microaerophilic conditions.
Polymerase chain reaction targeting species‑specific 16S rRNA sequences.
Serology detecting antibodies against M. pulmonis antigens.
Histopathology revealing characteristic peribronchiolar lymphoid hyperplasia.

Understanding the biology and clinical impact of Mycoplasma pulmonis is essential for managing respiratory disease in rat colonies and for implementing effective control strategies.

How Mycoplasma Affects Rats

Common Symptoms of Mycoplasma Infection

Mycoplasma infection in laboratory rats frequently presents with respiratory and systemic signs that can compromise experimental outcomes. Respiratory involvement manifests as sneezing, audible wheezing, and increased respiratory rate. Nasal and ocular discharge may be clear to serous, occasionally becoming mucoid. Upper‑airway inflammation often leads to labored breathing and audible stridor, especially during exertion.

Systemic manifestations include:

Progressive weight loss despite adequate food supply
Reduced water consumption and dehydration
Anorexia or diminished feed intake
Lethargy and decreased grooming activity
Fever detectable by rectal thermometry (typically 38–40 °C)
Hind‑limb weakness or ataxia in severe cases

Reproductive colonies may exhibit decreased fertility, irregular estrous cycles, and embryonic loss. Some infected rats remain subclinical, showing only mild weight fluctuation or transient nasal discharge, yet they can serve as reservoirs for transmission. Early recognition of these signs enables timely therapeutic intervention and containment measures.

Progression of the Disease

Mycoplasma infection in laboratory rats begins with an incubation period of 5–10 days after exposure. During this phase, the organism colonizes the respiratory epithelium without producing observable symptoms. Bacterial adhesion molecules interact with host cell surface receptors, allowing replication within the mucosal layer and evasion of innate immune defenses.

Clinical disease emerges as bronchial inflammation intensifies. Common manifestations include:

Nasal discharge and sneezing
Labored breathing, especially during exertion
Weight loss and reduced feed intake
Mild fever detectable by rectal temperature measurement

Histopathology shows peribronchiolar infiltrates of neutrophils, lymphocytes, and macrophages, followed by epithelial hyperplasia and occasional necrosis. If untreated, the infection can progress to chronic bronchopneumonia, characterized by fibrotic remodeling of airway walls and persistent cough. Secondary bacterial opportunists may colonize damaged tissue, increasing morbidity and mortality rates.

Effective management relies on early detection and interruption of the disease trajectory. Antimicrobial therapy with tetracycline-class agents halts bacterial replication, reducing inflammatory load and preventing transition to chronic lesions. Concurrently, strict biosecurity measures—such as quarantine of new arrivals, regular health monitoring, and environmental decontamination—limit pathogen spread and reduce the likelihood of disease escalation.

Transmission Routes

Mycoplasma organisms spread among laboratory rats through several well‑documented pathways. Recognizing each route is essential for effective biosecurity and disease management.

Direct animal‑to‑animal contact: nose‑to‑nose or grooming exchanges transfer organisms across mucosal surfaces.
Aerosolized particles: respiratory droplets generated by coughing or sneezing remain viable in the cage environment, allowing inhalation by nearby rodents.
Contaminated bedding and cage equipment: mycoplasma adheres to cellulose fibers, plastic surfaces, and water bottles, persisting until cleaning or replacement.
Maternal transmission: infected dams can pass the pathogen to offspring during gestation or through lactation, establishing infection in litters.
Ingestion of contaminated feed or water: oral exposure occurs when feed or water becomes polluted by infected secretions.
Personnel and animal‑care staff: gloves, gowns, and hands act as fomites, moving the pathogen between cages if proper disinfection is omitted.

Control measures must address each pathway. Routine cage changing, HEPA‑filtered ventilation, strict personal protective equipment protocols, and monitoring of breeding colonies reduce the likelihood of spread. Effective prevention relies on eliminating sources of contamination and interrupting transmission cycles at every identified route.

Managing Mycoplasma Infections

Diagnostic Methods

Clinical Examination

Clinical examination of laboratory rats suspected of Mycoplasma infection begins with a systematic observation of general condition and specific physical signs. The examiner should assess body weight, coat quality, and activity level, noting any weight loss, ruffled fur, or lethargy. Respiratory assessment includes counting breaths per minute, listening for nasal discharge, and detecting wheezing or crackles with a stethoscope. Ocular inspection should reveal conjunctival redness, swelling, or discharge. Palpation of the abdomen may uncover hepatomegaly or splenomegaly, which are common in systemic mycoplasmal disease.

Diagnostic sampling follows the physical assessment:

Nasal swab or lavage for culture on specialized mycoplasma media.
Blood collection for serology (ELISA) and PCR to detect organism DNA.
Bronchoalveolar lavage fluid for cytology and PCR.
Tissue biopsies (lung, liver) when necropsy is indicated.

Interpretation of results relies on correlating clinical findings with laboratory data. Positive PCR or culture confirms infection, while seroconversion indicates exposure. Elevated white‑blood‑cell counts and abnormal liver enzymes support systemic involvement.

Effective treatment and prevention strategies depend on early detection. Prompt antimicrobial therapy, typically tetracycline or enrofloxacin, is instituted after confirmation. Environmental control measures—enhanced cage sanitation, filtered air, and quarantine of new arrivals—reduce transmission. Regular clinical monitoring, combined with periodic laboratory screening, maintains colony health and minimizes outbreak risk.

Laboratory Testing

Laboratory testing is the primary means of confirming Mycoplasma infection in rat colonies and guiding therapeutic decisions. Samples are collected from the respiratory tract, ocular secretions, or tissues at necropsy. Proper handling includes immediate placement on ice, transport in Mycoplasma‑specific transport medium, and processing within 24 hours to preserve organism viability.

Diagnostic methods fall into three categories:

Culture – inoculation of selective broth or agar under microaerophilic conditions; identification by colony morphology, pH change, and polymerase chain reaction (PCR) confirmation.
Molecular assays – quantitative PCR targeting the 16S rRNA gene provides rapid detection and load estimation; multiplex panels can simultaneously screen for co‑infecting agents.
Serology – enzyme‑linked immunosorbent assay (ELISA) or indirect immunofluorescence detect antibodies; useful for monitoring herd exposure but not for acute diagnosis.

Interpretation of results requires correlation with clinical signs and colony history. Positive culture or PCR confirms active infection, prompting immediate treatment with appropriate antibiotics such as doxycycline or enrofloxacin. Seropositivity alone indicates prior exposure and may warrant further investigation.

Quality control measures include the use of positive and negative controls in each assay, periodic proficiency testing, and validation of detection limits. Documentation of sample origin, collection date, and test methodology ensures traceability and supports epidemiological tracking across facilities.

Treatment Approaches

Antibiotic Therapy

Antibiotic therapy remains the primary intervention for Mycoplasma infections in laboratory rats. The organism’s lack of a cell wall renders β‑lactam agents ineffective, directing treatment toward agents that inhibit protein synthesis or DNA replication.

Tetracyclines (e.g., doxycycline) administered orally at 10 mg/kg daily for 7–10 days achieve high tissue concentrations and reduce bacterial load.
Macrolides (e.g., tylosin, erythromycin) given via feed or drinking water at 50–100 mg/kg per day provide an alternative for colonies with tetracycline‑resistant strains.
Fluoroquinolones (e.g., enrofloxacin) delivered subcutaneously at 5 mg/kg for 5 days are effective against severe systemic disease but require careful monitoring for cartilage toxicity.

Therapeutic regimens should begin promptly after laboratory confirmation. Duration of therapy depends on clinical response; a minimum of five half‑lives after the last positive culture is recommended. Serial PCR testing of oropharyngeal swabs confirms clearance, while necropsy cultures verify eradication in research‑critical colonies. Resistance monitoring includes susceptibility testing before initiating treatment and after completion to detect emerging patterns.

Prevention relies on strict biosecurity and targeted prophylaxis. Incorporating low‑dose macrolides into feed during quarantine periods reduces colonization risk without inducing overt resistance. Regular environmental decontamination with Mycoplasma‑effective disinfectants, combined with sentinel animal monitoring, limits re‑introduction. Documentation of antibiotic use, dosing schedules, and outcome metrics supports reproducibility across facilities.

Common Antibiotics Used

Antibiotic therapy for mycoplasma infection in laboratory rats relies on agents that penetrate the cell membrane and inhibit protein synthesis, since the organisms lack a conventional cell wall and are intrinsically resistant to β‑lactam drugs. The most frequently employed classes include tetracyclines, macrolides, and fluoroquinolones.

Tetracyclines – Doxycycline and oxytetracycline are administered via drinking water or feed at concentrations of 0.5–2 g/L, providing systemic exposure that suppresses colonization. Treatment courses typically last 7–14 days, with dosage adjustments for young or pregnant animals to avoid growth retardation.
Macrolides – Azithromycin and erythromycin are delivered orally or subcutaneously. Azithromycin, given at 10–20 mg/kg once daily, offers a prolonged half‑life that reduces handling stress. Erythromycin requires multiple daily injections (50–100 mg/kg) and is less favored due to injection site irritation.
Fluoroquinolones – Enrofloxacin, administered at 5–10 mg/kg in the drinking water, achieves high tissue concentrations and is effective against resistant strains. Monitoring for potential cartilage toxicity in growing rats is essential.

Selection of an antibiotic must consider susceptibility patterns, route feasibility, and the health status of the colony. Prophylactic inclusion of low‑dose tetracycline in feed during high‑risk periods (e.g., after quarantine or transport) reduces the incidence of new infections without compromising microbiota balance. Continuous microbiological surveillance and periodic susceptibility testing ensure that chosen regimens remain effective and prevent the emergence of resistant mycoplasma populations.

Duration of Treatment

Effective management of mycoplasma infection in laboratory rats requires a clearly defined treatment period. The standard therapeutic course with tetracycline‑based regimens lasts 10–14 days, administered continuously at the recommended dose. Shorter courses (<7 days) have shown incomplete pathogen clearance and higher relapse rates, while extensions beyond 21 days provide no additional benefit and increase the risk of drug‑induced dysbiosis.

Factors that modify the optimal duration include:

Severity of clinical signs: severe respiratory or systemic involvement may warrant the full 14‑day schedule, whereas subclinical carriers can be treated for 10 days.
Age and immune status: neonates and immunocompromised animals often require the longer end of the range to ensure eradication.
Strain susceptibility: documented resistance to macrolides or fluoroquinolones necessitates adherence to the maximum recommended period to prevent selection of resistant populations.

Monitoring should commence on day 5 of therapy, with PCR or culture confirmation of mycoplasma absence before discontinuation. If tests remain positive, extend treatment by an additional 3–5 days and repeat verification. Completion of the prescribed interval without residual detection confirms successful resolution and reduces the likelihood of re‑infection in the colony.

Supportive Care

Supportive care is a critical component of managing mycoplasma disease in laboratory rats. Adequate hydration mitigates the dehydration that frequently accompanies respiratory and systemic infection. Provide sterile, warm water ad libitum and consider subcutaneous or oral fluid therapy for animals showing signs of fluid loss.

Nutritional support sustains immune function and promotes recovery. Offer highly palatable, nutrient‑dense diets; supplement with easily digestible protein sources and vitamins, particularly A, C, and E. Monitor feed intake daily and adjust portions to prevent weight loss.

Environmental management reduces secondary stressors. Maintain cage temperature between 20‑24 °C and relative humidity at 45‑55 %. Ensure optimal ventilation without drafts, and keep bedding dry and clean to limit bacterial load. Implement quarantine for affected cohorts to prevent cross‑contamination.

Clinical monitoring detects complications early. Record respiratory rate, body weight, and behavior at least twice daily. Administer analgesics such as meloxicam or buprenorphine according to dosage guidelines to alleviate pain and improve welfare. If fever develops, antipyretics may be employed under veterinary supervision. Regular veterinary assessments guide adjustments to supportive protocols and ensure humane outcomes.

Environmental Adjustments

Environmental control reduces the incidence and severity of mycoplasma disease in laboratory rats. Maintaining low humidity (30–40 %) limits bacterial survival on surfaces and in aerosol droplets. Regular monitoring of temperature (20–22 °C) ensures stable conditions that discourage pathogen proliferation.

Effective adjustments include:

Exhaust ventilation rates of at least 15 air changes per hour; use high‑efficiency particulate air (HEPA) filters on supply and exhaust ducts.
Installation of air curtains at cage rack entrances to prevent cross‑contamination between rooms.
Implementation of a sealed cage system with individually ventilated cages (IVCs) that provide filtered airflow directly to each animal.
Routine decontamination of bedding, feed, and water bottles with autoclaving or validated chemical disinfectants before reuse.
Separation of animal cohorts by health status; designate mycoplasma‑free zones with restricted personnel access.

Cleaning protocols must employ detergent‑free, low‑pH solutions to avoid residual chemicals that could impair the immune response. Surfaces should be wiped down daily and disinfected weekly with agents proven effective against mycoplasma species, such as quaternary ammonium compounds at manufacturer‑recommended concentrations.

Staff training emphasizes proper donning and doffing of personal protective equipment, hand hygiene before and after cage handling, and strict adherence to entry‑exit procedures. Documentation of environmental parameters, cleaning schedules, and personnel movement supports traceability and rapid response to any breach.

By integrating these environmental measures with antimicrobial therapy, facilities achieve a robust barrier against mycoplasma transmission, sustaining colony health and experimental reliability.

Nutritional Support

Nutritional management is a critical component of managing mycoplasma disease in laboratory rats. Adequate energy intake prevents weight loss associated with chronic infection and supports tissue repair. Diets should provide 3–4 % more calories than standard rodent chow during active disease phases, with frequent monitoring of body weight and feed consumption.

Specific nutrients influence immune competence and pathogen clearance. Supplementation of the following items is recommended:

Vitamin E (100–200 IU/kg diet) – antioxidant that protects cell membranes.
Vitamin C (500 mg/kg diet) – supports phagocytic activity.
Zinc (30–50 ppm) – essential for lymphocyte development.
Selenium (0.2–0.5 ppm) – cofactor for glutathione peroxidase.
Arginine (1–2 % of diet) – precursor for nitric oxide production.
Omega‑3 fatty acids (EPA/DHA, 0.5 % of diet) – modulate inflammatory responses.
Probiotic strains (Lactobacillus spp., 10⁸ CFU/g feed) – maintain gut microbial balance.

Hydration must be maintained with sterile, electrolyte‑balanced water. Adding glucose (2–5 %) to drinking solutions reduces dehydration risk and supplies readily absorbable energy. Avoidance of high‑fat, low‑fiber formulations reduces gastrointestinal stress and limits secondary infections.

Regular assessment of serum nutrient levels, together with clinical observation, allows adjustment of the dietary regimen. Prompt correction of deficiencies shortens the infection course and improves overall colony health.

Prevention Strategies

Biosecurity Measures

Biosecurity is the primary defense against mycoplasma infections in laboratory rat colonies. Effective programs combine physical barriers, procedural controls, and continuous surveillance to prevent introduction and spread of the pathogen.

Key components include:

Controlled access: restrict entry to animal rooms, use badge systems, and maintain a log of personnel movements.
Personal protective equipment (PPE): require gloves, gowns, shoe covers, and hair nets; change PPE when moving between areas.
Facility design: install HEPA‑filtered ventilation, separate animal suites for different health statuses, and provide dedicated equipment for each zone.
Cage management: use individually ventilated cages, autoclave or disinfect all bedding and supplies before entry, and avoid sharing rack space.
Quarantine: isolate new arrivals for a minimum of four weeks, test specimens by PCR or culture before integration.
Routine monitoring: conduct monthly health screens, record results in a central database, and act immediately on positive findings.
Disinfection protocols: apply validated agents (e.g., 10 % bleach, peracetic acid) to surfaces, cages, and equipment after each use; verify efficacy with ATP testing.

Implementation demands written standard operating procedures, regular staff training, and periodic audits to confirm compliance. Documentation of each step enables traceability and rapid response to breaches.

Consistent adherence to these measures reduces infection prevalence, protects research integrity, and supports animal welfare.

Quarantine Protocols

Quarantine measures are the primary barrier preventing the spread of mycoplasma among laboratory rat colonies. Upon receipt of new animals, isolate them in a dedicated barrier room for a minimum of 30 days, monitoring for respiratory signs and conducting PCR screening at entry and before release. All personnel entering the quarantine zone must wear disposable gowns, gloves, and shoe covers, and must follow a strict entry‑exit protocol that includes hand disinfection and equipment decontamination.

Key elements of an effective quarantine program include:

Physical separation: dedicated airflow, HEPA filtration, and negative pressure relative to adjacent rooms.
Health monitoring: weekly clinical observations, biweekly serology or PCR testing, and immediate removal of any animal showing abnormal signs.
Sanitation procedures: routine cleaning with mycoplasma‑effective disinfectants (e.g., 0.5 % sodium hypochlorite), sterilization of cages and water bottles before reuse.
Record keeping: detailed logs of animal IDs, test results, and personnel access to ensure traceability and compliance with institutional biosafety policies.

Compliance with these protocols minimizes the risk of introducing mycoplasma into established colonies and supports the broader goal of disease control in rodent facilities.

Hygiene Practices

Effective control of Mycoplasma spp. in laboratory rats relies heavily on strict hygiene protocols. Routine cage cleaning removes contaminated bedding, feces, and urine that can harbor the pathogen. Replace bedding at least twice weekly, and disinfect cages with an approved virucidal agent before reuse.

Implement a comprehensive disinfection regimen for all surfaces and equipment. Use a 0.5 % sodium hypochlorite solution or an equivalent commercial disinfectant, allowing the recommended contact time before wiping dry. Autoclave reusable tools whenever possible.

Maintain a quarantine period for all incoming animals. Isolate new rats for a minimum of four weeks, monitor for clinical signs, and test biological samples before integration with the main colony. Separate housing reduces the risk of cross‑contamination.

Adopt personal protective measures for staff. Wash hands with antimicrobial soap before and after handling animals, wear disposable gloves, and change laboratory coats when moving between rooms. Store PPE in a designated area to avoid accidental reuse.

Key hygiene practices include:

Daily removal of soiled bedding and food debris.
Weekly deep cleaning of racks, water bottles, and feeding stations.
Regular testing of water and feed for Mycoplasma contamination.
Controlled animal density to limit stress‑induced shedding.
Installation of high‑efficiency particulate air (HEPA) filtration in animal rooms.

Consistent application of these procedures minimizes environmental reservoirs, interrupts transmission cycles, and supports the overall health of rat colonies.

Environmental Management

Effective environmental control reduces the incidence of mycoplasma disease in rat colonies and supports therapeutic outcomes. Clean housing units prevent pathogen persistence; daily removal of soiled bedding, weekly deep cleaning of cages, and routine sterilization of water bottles eliminate reservoirs. Use autoclaved or irradiated bedding material to avoid re‑introduction from contaminated sources.

Ventilation systems should maintain airflow rates of at least 30 changes per hour, with HEPA filtration to capture aerosolized particles. Temperature and humidity levels kept within 20‑22 °C and 40‑60 % respectively discourage mycoplasma survival and limit stress‑induced susceptibility.

Quarantine procedures isolate new arrivals for a minimum of four weeks. During this period, perform PCR screening of oral swabs and serological testing. Positive animals are either treated with validated antibiotics or removed from the breeding program to prevent spread.

Disinfection protocols require agents proven effective against Mycoplasma spp., such as 70 % ethanol, 10 % bleach, or commercial mycoplasma‑specific disinfectants. Apply solutions to all surfaces, equipment, and transport containers after each use, allowing appropriate contact time.

Regular environmental monitoring includes:

Air sampling for mycoplasma DNA using qPCR.
Surface swabs of cage racks, water bottles, and feeding trays.
Record‑keeping of cleaning schedules, disinfectant concentrations, and audit results.

Implementing these measures creates a controlled environment that minimizes infection pressure, facilitates recovery of affected animals, and sustains colony health over the long term.

Ventilation Considerations

Adequate ventilation limits aerosol transmission of mycoplasma among laboratory rats. Proper airflow reduces pathogen concentration in cage environments and supports overall health of the colony.

Key ventilation parameters:

Air changes per hour (ACH) of 10–15 in animal rooms.
High‑efficiency particulate air (HEPA) filtration for supply and exhaust lines.
Relative humidity maintained at 40–60 % to prevent droplet formation.
Temperature kept within 20–24 °C to avoid stress‑induced immunosuppression.

Design and operation guidelines:

Position supply vents to create laminar flow across cage racks, avoiding dead‑space zones.
Install exhaust vents at the highest points to promote upward removal of contaminated air.
Use pressure differentials (positive pressure in clean zones, negative pressure in quarantine areas) to control directional movement of air.
Validate airflow patterns with smoke tests or computational fluid dynamics modeling before occupancy.

Monitoring and maintenance practices:

Record ACH and filter integrity weekly; replace filters according to manufacturer specifications or when pressure drop exceeds 10 Pa.
Calibrate humidity and temperature sensors monthly; adjust HVAC settings promptly after deviations.
Conduct microbial air sampling quarterly to confirm absence of mycoplasma DNA in ventilation ducts.

Implementing these measures minimizes airborne spread, complements antimicrobial therapy, and sustains a pathogen‑free rat colony.

Substrate Choices

Choosing the appropriate substrate is critical when addressing mycoplasma infections in laboratory rats, both for diagnostic culture and for evaluating therapeutic agents.

Culture media must support the fastidious growth requirements of Mycoplasma spp. Recommended options include:

SP4 broth or agar – provides essential nutrients (cholesterol, serum, and nucleic acids) and yields rapid colony formation.
Freund’s medium – suitable for isolates that prefer a lower pH environment; often combined with selective antibiotics to suppress contaminating flora.
Modified Hayflick medium – useful for long‑term maintenance of strains, especially when serial passage is required for susceptibility testing.

When selecting a substrate for in vivo studies, consider the following factors:

Bedding material – use low‑dust, autoclaved cellulose or corncob bedding to minimize environmental reservoirs; avoid wood shavings that can harbor mycoplasma DNA.
Feed formulation – employ pelleted diets sterilized by gamma irradiation; avoid powdered feeds that may introduce contaminants during handling.
Water delivery system – prefer autoclaved, filtered water bottles over tap water lines, which can serve as biofilm substrates for mycoplasma persistence.

For drug delivery, substrate compatibility influences efficacy:

Oral gels formulated with hydroxypropyl methylcellulose provide a stable matrix that protects antibiotics from degradation in the gastrointestinal tract.
Injectable emulsions based on sterile oil‑in‑water carriers ensure uniform dispersion of lipophilic agents, reducing the risk of precipitation that could compromise dosing.
Topical ointments using petroleum‑based bases allow localized treatment of skin lesions without promoting bacterial overgrowth.

In diagnostic laboratories, substrate selection also affects detection sensitivity. Employing solid media with a thin, uniform layer facilitates colony visualization and reduces background growth, while broth cultures supplemented with selective agents improve isolation rates from low‑level infections.

Overall, substrate decisions must align with the biological characteristics of mycoplasma, the experimental design, and the intended preventive or therapeutic outcome. Proper selection enhances diagnostic accuracy, supports reliable drug efficacy testing, and helps maintain a mycoplasma‑free environment in rat colonies.

Nutritional Considerations

Adequate nutrition is a critical component of both therapeutic management and prophylaxis of Mycoplasma‑associated disease in laboratory rats.

During active infection, dietary regimens should prioritize energy density and high‑quality protein to offset increased metabolic demand and tissue catabolism. A diet containing 20–24 % crude protein, supplemented with readily digestible amino acids such as lysine and methionine, supports immune cell proliferation and antibody synthesis. Energy provision can be enhanced by increasing carbohydrate content to 45–55 % of metabolizable energy, while limiting excessive fat to prevent gastrointestinal upset.

Micronutrient support influences disease outcome. Vitamin A at 3,000–5,000 IU/kg feed promotes mucosal integrity; vitamin E (150–200 IU/kg) and selenium (0.2 ppm) act synergistically as antioxidants, reducing oxidative stress induced by the pathogen. Zinc (30–50 ppm) and copper (6–10 ppm) are essential for enzymatic functions of the immune system and should be present at recommended levels to avoid immunosuppression.

Probiotic supplementation can modulate the gut microbiota, limiting colonization by opportunistic organisms that may exacerbate Mycoplasma infection. Viable strains of Lactobacillus and Bifidobacterium, administered at 10⁸–10⁹ CFU/g feed, have demonstrated efficacy in maintaining barrier function and enhancing local immunity.

Preventive nutrition focuses on consistency and cleanliness. Provide a pelleted diet with low dust to minimize aerosolized particles that can carry Mycoplasma. Ensure water is free of contaminants and consider adding a mild antimicrobial agent (e.g., 0.01 % sodium benzoate) to reduce bacterial load without harming the host.

Key nutritional actions:

Increase protein to 20–24 % and carbohydrate to 45–55 % of metabolizable energy during infection.
Supplement vitamins A, E, selenium, zinc, and copper at levels supporting immune competence.
Incorporate probiotic cultures at 10⁸–10⁹ CFU/g feed for gut health.
Use low‑dust pelleted formulation and maintain sterile water supplies for prophylaxis.

Implementing these measures alongside antimicrobial therapy enhances recovery rates and reduces the incidence of Mycoplasma transmission within rat colonies.

Genetic Predisposition and Breeding Practices

Genetic background determines individual susceptibility to mycoplasma disease in laboratory rats. Certain inbred strains carry alleles of the major histocompatibility complex that reduce the efficiency of cellular immunity, resulting in higher colonization rates and prolonged shedding. Polymorphisms in toll‑like receptor genes and cytokine promoters have been linked to variations in inflammatory response, influencing both clinical manifestation and transmission potential.

Breeding management directly shapes the genetic composition of a colony and therefore its infection risk. Practices that increase genetic uniformity, such as repetitive sibling matings, amplify the prevalence of vulnerability alleles. Conversely, strategic outcrossing and the introduction of resistant genotypes dilute susceptibility factors. Routine health surveillance, quarantine of new arrivals, and the culling of confirmed carriers are essential components of a preventive breeding program. Typical measures include:

Maintaining specific pathogen‑free (SPF) status through barrier housing.
Implementing periodic serological and PCR testing of breeding stock.
Selecting breeders based on documented resistance markers.
Avoiding excessive inbreeding coefficients by tracking pedigree data.

Combining genetic screening with disciplined breeding protocols reduces the incidence of mycoplasma infection, limits outbreak severity, and supports the overall health of research colonies. Continuous evaluation of genotype‑infection correlations allows refinement of selection criteria, ensuring long‑term resilience against the pathogen.

Stress Reduction Techniques

Effective management of mycoplasma disease in laboratory rodents requires attention to animal welfare, particularly stress mitigation. Elevated cortisol levels impair immune function, reduce vaccine efficacy, and hinder antibiotic response. Implementing stress reduction measures directly supports therapeutic outcomes and lowers infection recurrence.

Practical techniques include:

Environmental enrichment such as nesting material, chewable objects, and tunnel systems.
Consistent handling routines performed by the same personnel, using gentle restraint methods.
Controlled lighting cycles that mimic natural photoperiods, avoiding abrupt changes.
Sound attenuation through acoustic insulation or white‑noise generators to reduce sudden noise spikes.
Temperature and humidity regulation within optimal ranges for the species, preventing thermal discomfort.

Monitoring protocols should record behavioral indicators (e.g., grooming, activity patterns) and physiological markers (e.g., serum corticosterone) before and after interventions. Data integration with treatment regimens enables adjustment of antimicrobial schedules, ensuring maximal efficacy while minimizing adverse effects.