# [Feline Respiratory Infections](/knowledge/bacteria/pet-bacteria/feline-respiratory-infections-causes-treatment-zoonosis): Etiology, Transmission, and [Zoonotic Risk](/knowledge/parasites/pet-parasites/zoonotic-risk-humans-get-parasites-from-pets)

## Key Takeaways

- Bacterial pathogens, including _Bordetella bronchiseptica_, _Chlamydia felis_, and _Mycoplasma_ species, are significant contributors to feline respiratory disease, acting as primary invaders or secondary opportunists that exacerbate viral infections.
- Transmission occurs through direct contact with infected secretions, aerosolized droplets from coughing/sneezing, and fomite contamination, with kittens and immunocompromised adults being at highest risk.
- Diagnostic approaches integrate clinical signs with laboratory methods such as bacterial culture, antimicrobial sensitivity testing, and multiplex PCR panels for definitive pathogen identification.
- Treatment necessitates targeted antimicrobial therapy guided by culture and sensitivity, with doxycycline being a common first-line choice for _B. bronchiseptica_, _C. felis_, and _Mycoplasma_ infections.
- Zoonotic risk is primarily associated with _Bordetella bronchiseptica_ and _Pasteurella multocida_, posing a greater concern for immunocompromised individuals through direct contact or bites/scratches.
- Prevention strategies include core vaccinations against common viral triggers, environmental management (ventilation, disinfection), and quarantine protocols for newly introduced cats.

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## Introduction

[Feline upper respiratory tract infections](/knowledge/bacteria/pet-bacteria/feline-upper-respiratory-infections) represent a complex disease syndrome with multifactorial etiology involving viral, bacterial, and mycoplasmal pathogens [<a href="#ref-1">1</a>]. While viral agents such as feline herpesvirus type 1 (FHV-1) and [feline calicivirus](/knowledge/viruses/pet-viruses/feline-calicivirus) (FCV) are frequently incriminated as primary initiators, bacterial pathogens play critical roles as primary invaders or secondary opportunists that exacerbate clinical disease [<a href="#ref-2">2</a>]. Understanding the bacterial component of [feline respiratory infections](/knowledge/bacteria/pet-bacteria/feline-respiratory-infections-causes-treatment-zoonosis) is essential for appropriate antimicrobial stewardship, accurate diagnosis, and management of [zoonotic risk](/knowledge/parasites/pet-parasites/zoonotic-risk-humans-get-parasites-from-pets) [<a href="#ref-3">3</a>]. This article provides a detailed examination of bacterial causes, transmission dynamics, clinical implications, and the zoonotic potential of feline respiratory pathogens.

## Etiology of [Bacterial Respiratory Infections in Cats](/knowledge/bacteria/pet-bacteria/bacterial-respiratory-infections-cats-etiology-clinical-treatment)

### [Bordetella bronchiseptica](/knowledge/bacteria/pet-bacteria/bordetella-bronchiseptica)

_Bordetella bronchiseptica_ is a Gram negative, aerobic coccobacillus that colonizes the ciliated respiratory epithelium of cats and other mammalian hosts [<a href="#ref-1">1</a>, <a href="#ref-4">4</a>]. It is a primary pathogen in feline respiratory disease, particularly in high density housing environments such as shelters and breeding catteries [<a href="#ref-2">2</a>]. The organism expresses adhesins including filamentous hemagglutinin and fimbriae that facilitate binding to ciliated cells [<a href="#ref-4">4</a>]. _B. bronchiseptica_ produces a tracheal cytotoxin that disrupts ciliary function and a dermonecrotic toxin that contributes to epithelial damage [<a href="#ref-1">1</a>].

### Chlamydia felis

_Chlamydia felis_ (formerly _Chlamydophila felis_) is an obligate intracellular Gram negative bacterium that primarily causes conjunctivitis in cats [<a href="#ref-2">2</a>]. Although its role in lower respiratory disease is less pronounced, it can contribute to rhinitis and sneezing, particularly in young kittens [<a href="#ref-1">1</a>]. The organism replicates within cytoplasmic inclusions of conjunctival epithelial cells and induces an inflammatory response characterized by neutrophil infiltration.

### Mycoplasma Species

Several _Mycoplasma_ species, including _Mycoplasma felis_ and _Mycoplasma gateae_, are associated with feline upper respiratory disease [<a href="#ref-2">2</a>, <a href="#ref-3">3</a>]. Mycoplasmas are cell wall deficient bacteria that adhere to respiratory epithelial cells and induce ciliostasis and inflammation [<a href="#ref-1">1</a>]. They are frequently isolated concurrently with viral or other bacterial pathogens and are considered opportunistic secondary invaders [<a href="#ref-2">2</a>].

### Other Bacterial Pathogens

| Pathogen | Role in Feline Respiratory Disease |
|-----|------------------|
| _Pasteurella multocida_ | Commensal of oral cavity; opportunistic invader in compromised hosts [<a href="#ref-1">1</a>] |
| _Streptococcus canis_ | Secondary invader associated with pneumonia [<a href="#ref-2">2</a>] |
| _Escherichia coli_ | Opportunistic pathogen in neonatal kittens with aspiration pneumonia [<a href="#ref-3">3</a>] |
| _Staphylococcus_ spp. | Occasional secondary invader in chronic rhinosinusitis [<a href="#ref-4">4</a>] |

## How Do Cats Get Respiratory Infections

Transmission of bacterial respiratory pathogens occurs via direct contact with infected secretions, fomite exposure, and aerosolization over short distances [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>]. Kittens and immunocompromised adults are at highest risk [<a href="#ref-3">3</a>].

### Transmission Routes

1. **Direct contact**: Nose to nose contact, mutual grooming, and sharing food bowls facilitate pathogen transfer [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>].
2. **Aerosol droplets**: Sneezing and coughing generate droplet nuclei that can transmit _B. bronchiseptica_ and _Mycoplasma_ over distances up to 1 to 2 meters [<a href="#ref-2">2</a>].
3. **Fomites**: Bedding, litter boxes, and human hands can carry viable bacteria for hours to days [<a href="#ref-1">1</a>, <a href="#ref-3">3</a>].
4. **Vertical transmission**: Queens shedding _C. felis_ during parturition can infect newborn kittens [<a href="#ref-2">2</a>].

### Risk Factors

Crowded shelters, multicat households, poor ventilation, and concurrent viral infections (FHV-1, FCV) increase the likelihood of bacterial respiratory infection acquisition [<a href="#ref-3">3</a>, <a href="#ref-4">4</a>]. Stress induced by weaning, transport, or surgery elevates cortisol levels and suppresses mucosal immunity, facilitating bacterial colonization [<a href="#ref-1">1</a>].

## Are [Cat Respiratory Infections](/knowledge/bacteria/pet-bacteria/cat-respiratory-infections-etiology-clinical-signs-zoonotic-potential-management) Dangerous

Severity of bacterial respiratory infections ranges from mild self limiting conjunctivitis to life threatening pneumonia [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>]. In otherwise healthy adult cats, uncomplicated infections typically resolve within 7 to 14 days with supportive care [<a href="#ref-3">3</a>]. However, several factors increase danger.

### Complications

- **Chronic rhinosinusitis**: Persistent inflammation after acute infection leads to turbinate destruction and secondary bacterial colonization [<a href="#ref-1">1</a>, <a href="#ref-4">4</a>].
- **Aspiration pneumonia**: Nasal discharge and altered swallowing reflexes predispose to inhalation of food or water [<a href="#ref-2">2</a>].
- **Neonatal mortality**: Kittens infected with _B. bronchiseptica_ or _C. felis_ may develop severe bronchopneumonia with mortality rates exceeding 50% in untreated litters [<a href="#ref-3">3</a>].
- **Systemic dissemination**: _Pasteurella multocida_ can cause septicemia in neonates [<a href="#ref-1">1</a>].

### Disease Severity Indicators

| Clinical Sign | Interpretation |
|--------|--------|
| Dyspnea, open mouth breathing | Lower respiratory tract involvement [<a href="#ref-2">2</a>] |
| Purulent ocular or nasal discharge | Active bacterial infection [<a href="#ref-3">3</a>] |
| Anorexia for over 24 hours | Risk of hepatic lipidosis [<a href="#ref-1">1</a>] |
| Fever over 104°F (40°C) | Systemic inflammatory response [<a href="#ref-4">4</a>] |

## Diagnostic Approaches

Accurate diagnosis requires integration of clinical signs, cytology, culture, and molecular methods [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>].

```mermaid
flowchart TD
 A["Cat with respiratory signs"] --> B["Clinical examination"]
 B --> C{"Nasal/ocular discharge?"}
 C -->|"Yes"| D["Swab for cytology and PCR"]
 C -->|"No"| E["Radiography if dyspnea"]
 D --> F["Cytology: neutrophils, intracellular bacteria?"]
 F --> G["Culture and antimicrobial sensitivity"]
 F --> H["PCR panel: FHV-1, FCV, C. felis, B. bronchiseptica, Mycoplasma"]
 E --> I["Alveolar pattern?"]
 I --> J["Transtracheal wash for culture"]
 G & H & J --> K["Targeted antimicrobial therapy"]
```

### Sample Collection

Deep nasal or oropharyngeal swabs are preferred for bacterial culture and PCR [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>]. Conjunctival swabs are optimal for _C. felis_ detection [<a href="#ref-3">3</a>]. Samples should be placed in transport medium and processed within 24 hours [<a href="#ref-4">4</a>].

### Laboratory Methods

- **Bacterial culture**: Selective media ([MacConkey agar](/knowledge/diagnostics/microbiology/macconkey-agar-selective-differential-enteric) for _B. bronchiseptica_, enriched chocolate agar for _C. felis_) [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>].
- **PCR assays**: Multiplex panels detect FHV-1, FCV, _C. felis_, _B. bronchiseptica_, and _Mycoplasma felis_ with high sensitivity and specificity [<a href="#ref-2">2</a>, <a href="#ref-3">3</a>].
- **Serology**: Limited utility for bacterial pathogens; antichlamydial antibody testing may aid diagnosis in chronic cases [<a href="#ref-4">4</a>].

## Treatment Principles

Antimicrobial therapy should be guided by culture and sensitivity results when possible [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>].

### First Line Antimicrobials

| Pathogen | Drug of Choice | Alternative |
|-----|--------|-------|
| _B. bronchiseptica_ | Doxycycline | Fluoroquinolones, chloramphenicol [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>] |
| _C. felis_ | Doxycycline | Azithromycin, tetracycline ophthalmic [<a href="#ref-2">2</a>, <a href="#ref-3">3</a>] |
| _Mycoplasma_ spp. | Doxycycline | Fluoroquinolones, tylosin [<a href="#ref-1">1</a>] |
| _P. multocida_ | Amoxicillin clavulanate | Doxycycline, cephalosporins [<a href="#ref-3">3</a>] |

Supportive care includes humidification, nasal clearance, appetite stimulation, and fluid therapy [<a href="#ref-1">1</a>, <a href="#ref-4">4</a>]. Corticosteroids are contraindicated during active bacterial infection [<a href="#ref-2">2</a>].

## [Is Cat Respiratory Infection Contagious to Humans](/knowledge/bacteria/pet-bacteria/feline-upper-respiratory-infection-zoonotic-potential)

Zoonotic potential varies by pathogen. Most feline bacterial respiratory agents have low to moderate [zoonotic risk](/knowledge/parasites/pet-parasites/zoonotic-risk-humans-get-parasites-from-pets), primarily affecting immunocompromised individuals [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>].

### Zoonotic Pathogens of Concern

- **_Bordetella bronchiseptica_**: Documented transmission from cats to immunocompromised humans, including cases of pneumonia in HIV positive patients and neutropenic individuals [<a href="#ref-1">1</a>, <a href="#ref-3">3</a>]. Healthy adults rarely develop disease [<a href="#ref-2">2</a>].
- **_Pasteurella multocida_**: Commonly transmitted via bites or scratches; can cause wound infections, cellulitis, and occasionally respiratory disease in humans [<a href="#ref-1">1</a>, <a href="#ref-4">4</a>].
- **_Chlamydia felis_**: Rarely causes human conjunctivitis; reported in immunocompromised individuals after direct ocular contact with infected cat secretions [<a href="#ref-2">2</a>, <a href="#ref-3">3</a>].
- **_Mycoplasma felis_**: No confirmed zoonotic transmission; considered host specific [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>].

### Risk Mitigation

Immunocompromised individuals should avoid contact with cats showing respiratory signs, practice hand hygiene after handling, and wear gloves when cleaning ocular or nasal discharge [<a href="#ref-3">3</a>, <a href="#ref-4">4</a>].

## Prevention and Control

- **Vaccination**: Core vaccines for FHV-1 and FCV reduce viral predisposing factors; intranasal _B. bronchiseptica_ vaccine is available for high risk cats [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>].
- **Environmental management**: Adequate ventilation, disinfection with quaternary ammonium compounds, and reduced stocking density in shelters [<a href="#ref-2">2</a>, <a href="#ref-3">3</a>].
- **Isolation**: Newly introduced cats should be quarantined for 14 days [<a href="#ref-1">1</a>].

## Conclusion

Bacterial pathogens contribute significantly to [feline respiratory infections](/knowledge/bacteria/pet-bacteria/feline-respiratory-infections-etiology-clinical-presentation-diagnostic-approach), either as primary agents or as secondary invaders following viral infection. Understanding transmission routes, clinical progression, and diagnostic pathways enables effective management and reduces [zoonotic risk](/knowledge/parasites/pet-parasites/zoonotic-risk-humans-get-parasites-from-pets). The question "how do cats get respiratory infections" is answered through a combination of direct contact, aerosol, and fomite transmission. The danger of these infections depends on host factors and pathogen virulence, with severe outcomes in kittens and immunocompromised adults. Regarding [zoonotic risk](/knowledge/parasites/pet-parasites/zoonotic-risk-humans-get-parasites-from-pets), _B. bronchiseptica_ and _Pasteurella multocida_ represent the principal concerns, particularly for immunocompromised human contacts.

## Related Clinical & Scientific Guides

* [Duck Diseases: A Comprehensive Overview for Veterinary Practitioners](/knowledge/bacteria/general/duck-diseases-comprehensive-overview-veterinary)
* [Salmonella Dublin in Cattle: Emerging Pathogen, Diagnostic Challenges, and Public Health Impact](/knowledge/bacteria/general/salmonella-dublin-cattle-emerging-pathogen-diagnostic-public-health)
* [Mycoplasma Infections in Poultry: Vaccination Strategies and Control Programs](/knowledge/bacteria/general/mycoplasma-infections-in-poultry-vaccination-strategies-and-control-programs)

## References

<a id="ref-1"></a>[<a href="#ref-1">1</a>] Greene CE, ed. Infectious Diseases of the Dog and Cat. 4th ed. Elsevier Saunders; 2012.

<a id="ref-2"></a>[<a href="#ref-2">2</a>] Sykes JE. Canine and Feline Infectious Diseases. Elsevier; 2014.

<a id="ref-3"></a>[<a href="#ref-3">3</a>] Lappin MR. [Feline upper respiratory infections](/knowledge/bacteria/pet-bacteria/feline-upper-respiratory-infections-bacterial-pathogens). In: Bonagura JD, Twedt DC, eds. Kirk's Current Veterinary Therapy XV. Elsevier; 2014:1218-1222.

<a id="ref-4"></a>[<a href="#ref-4">4</a>] Sparkes AH, Caney SMA, Sturgess CP, eds. The Feline Medicine Handbook. Veterinary Press; 2016.

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**Disclaimer**: This article is for educational and informational purposes only. It is not intended to substitute for professional veterinary advice, diagnosis, treatment, or regulatory guidance. Always consult a licensed veterinarian or qualified specialist regarding animal health, disease diagnosis, and therapeutic decisions.