- Congenital Disorders
- PRIMARY CILIARY DYSKINESIA
- HYPOPLASIA OF THE TRACHEA
- CONGENITAL TRACHEAL COLLAPSE
- CONGENITAL BRONCHIAL COLLAPSE
- Infectious Tracheobronchitis
- CANINE INFECTIOUS TRACHEOBRONCHITIS
- FELINE INFECTIOUS TRACHEOBRONCHITIS
- PARASITIC TRACHEOBRONCHITIS
- TRACHEAL AND BRONCHIAL TRAUMA
- TRACHEAL AND BRONCHIAL FOREIGN BODY
Cough is the most common clinical sign associated with tracheal and bronchial disease. Following a history and thorough physical examination to rule out infectious tracheobronchitis, thoracic and soft-tissue cervical radiographs may be indicated. Thoracic radiography is perhaps the single most important diagnostic test in the evaluation of the puppy or kitten that presents with cough as its primary complaint. Tracheal hypoplasia, extraluminal compressive diseases, diseases causing tracheal stenosis, intraluminal masses, and tracheal collapse may be apparent radiographically. Tracheoscopy with a small-diameter endoscope (approximately 3.5 to 5 mm in diameter or a rigid arthroscope) is useful in evaluating the trachea when obstructive or mucosal disease is suspected. It is especially useful in the diagnosis of tracheal collapse, tracheal foreign body, tracheal stenosis, parasitic tracheobronchitis, and tracheal osteochondroma.
PRIMARY CILIARY DYSKINESIA
Primary ciliary dyskinesia is a congenital respiratory disorder that is characterized by absent or deficient mucociliary clearance (). The ciliary dysfunction reduces mucociliary transport, which frequently leads to persistent or recurrent rhinitis, sinusitis, bronchitis, and bronchopneumonia. Chronic cough, nasal discharge, and recurrent bronchopneumonia are the most common complaints. Affected dogs may experience signs from birth. Breeds affected include the bichon frise, Border collie, Chihuahua, Chinese shar-pei, chow chow, English springer spaniel, English pointer, English setter, Dalmatian, Doberman pinscher, golden retriever, miniature poodle, Old English sheepdog, and Rottweiler. The condition is likely inherited as an autosomal recessive trait (). Definitive diagnosis depends on demonstration of decreased mucociliary clearance and abnormal structural appearance of the cilia by electron microscopy. Decreased mucociliary clearance can be detected by using nuclear imaging to monitor the clearance of a small drop of 99mTc-labeled macroaggregated albumin from the nasal cavity or distal region of the trachea. Treatment of primary ciliary dys-kinesia requires the periodic or continuous use of antimicrobial agents and supportive care (see Table Therapeutic Asents Used in Respiratory Disorders).
HYPOPLASIA OF THE TRACHEA
Hypoplasia of the trachea is a congenital defect in which there is apposition or overlap of the free ends of each of the tracheal rings, resulting in narrowing of the cross-sectional tracheal diameter (). The disease is seen most commonly in English bulldogs, Boston terriers, and boxers, but both brachycephalic and nonbrachycephalic breeds can be affected. The disorder has also been diagnosed in the cat (). Although most affected animals will show clinical signs early in life, not all animals with hypoplasia of the trachea will be symptomatic. When present, signs of hypoplasia of the trachea are usually evident within the first 5 months of life and may include coughing, gagging, respiratory distress, stridor, decreased exercise tolerance, and syncope. Crackles or wheezes may be heard on thoracic auscultation. Other associated congenital anomalies include elongated soft palate, stenotic nares, megaesophagus, cardiac defects, and cleft palate. Radiographic diagnosis can be made with the aid of a lateral thoracic radiograph by dividing the tracheal diameter at the thoracic inlet (TD) by the diameter of the thoracic inlet (TI) (). The TD/TI should be less than 0.16 in brachycephalic dogs with tracheal hypoplasia and less than 0.2 in affected nonbrachycephalic dogs. Dyspnea does not appear to be related to the degree of narrowing of the tracheal lumen. In most cases, dogs with dyspnea have concurrent anomalies that can account for the respiratory distress (). Treatment of dogs showing signs of hypoplasia of the trachea is directed toward treatment of underlying respiratory tract infection if present and correction of concurrent anomalies if possible.
CONGENITAL TRACHEAL COLLAPSE
Congenital tracheal collapse is uncommon but was reported in a dog that demonstrated respiratory distress and an obstructed breathing pattern. The cause of the tracheal collapse was an absence of cartilage in the tracheal rings ().
CONGENITAL BRONCHIAL COLLAPSE
Congenital bronchial collapse is also uncommon, having been reported in a 6-week-old Pekingese that suffered severe respiratory distress (). At necropsy, pneumothorax and pulmonary emphysema were identified and believed to be the result of the bronchial collapse.
CANINE INFECTIOUS TRACHEOBRONCHITIS
Canine infectious tracheobronchitis, commonly referred to as “kennel cough,” usually occurs where dogs are housed together (i.e., animal shelters, pet shops, boarding kennels, and veterinary hospitals). Bordetella bronchiseptica, canine parainfluenza virus, and Mycoplasma species are the most frequent causative agents (). Other agents that may be involved include canine distemper virus, canine adenovirus-2, canine adenovirus-1, canine reo-virus-1, canine reovirus-2, canine reovirus-3, and canine herpesvirus. Affected dogs usually have had recent exposure to other dogs and experienced sudden onset of a paroxysmal cough. Other signs may include oculonasal discharge, conjunctivitis, depression, and fever. Coughing is usually self-limiting, resolving within 2 weeks. A more serious form of the disease, characterized by chronic bronchopneumonia, is seen in young puppies and young adult dogs with congenital airway abnormalities.
Diagnosis is primarily based on clinical signs and a history of exposure to other dogs. Thoracic radiographs are usually not necessary but if taken are normal unless secondary bronchopneumonia is present. Culture of tracheobronchial lavage solutions should be performed in dogs that have systemic illness, have radio-graphic evidence of bronchopneumonia, or fail to improve after symptomatic therapy to treat the signs.
Affected dogs should be isolated from other dogs and maintained in a warm, stress-free environment. Antimicrobial therapy, although not always needed, is indicated for puppies and young adults because of the likely involvement of Bordetella bronchiseptica or Mycoplasma species and the potential severity of bronchopneumonia as a sequela (see Table Therapeutic Asents Used in Respiratory Disorders). Ideally, antimicrobial therapy should be based on bacterial culture and sensitivity testing. Chloramphenicol or amoxicillin/clavulanate combinations are initial choices for antimicrobial therapy because they are usually effective treatment for both Bordetella bronchiseptica and Mycoplasma species (). Antitussives can be used to suppress excessive nonproductive coughing in animals without evidence of bronchopneumonia (see Table Therapeutic Asents Used in Respiratory Disorders). Prevention is based on vaccination programs and avoidance of potentially infected dogs. Sodium hypochlorite bleach (diluted 1 to 32 with water and a freshly prepared solution) may be used for disinfection of the infected premises.
FELINE INFECTIOUS TRACHEOBRONCHITIS
Infectious tracheobronchitis is uncommon in adult cats, but in cats younger than 1 year of age it can be especially common and associated with Bordetella bronchiseptica infection and the same viral agents that cause infectious upper respiratory infections (). Cats housed together in confined quarters frequently contain inapparent, chronic carrier cats that shed feline herpesvirus intermittently and/or feline calicivirus continuously. Active upper respiratory disease in these carrier cats is often triggered by stressful situations such as weaning, overcrowding, and poor husbandry.
In dogs, Bordetella bronchiseptica causes paroxysms of a dry, hacking cough. Although coughing may occur in cats, it is usually mild. More typical signs include fever, sneezing, oculonasal discharge, submandibular lymphadenopathy, and increased lung sounds. Most illness is usually self-limiting, with spontaneous resolution occurring after about 10 to 14 days. Severe bronchopneumonia associated with Bordetella bronchiseptica may occur, especially in kittens younger than 12 weeks of age ().
Specific diagnosis of feline bordetellosis is difficult because the signs associated with it mimic those seen with the viral respiratory disease agents. Oropharyngeal and tracheobronchial cultures may be used to identify active Bordetella bronchiseptica infection. Isolation of the organism from active cases is relatively easy; however, chronic carrier cats often shed few organisms and require repeated oropharyngeal cultures.
Infected cats can be treated with tetracycline or amoxicillin/clavulanate combinations for 10 to 14 days (). Antimicrobial therapy does not eliminate the carrier state but does reduce the severity of the disease. Proper husbandry can minimize the impact of Bordetella broncbiseptica infection in a group. Good nutrition, sanitation, ventilation, parasite control, and control of other respiratory agents minimize the occurrence of clinical disease in these environments.
Although feline bordetellosis is not as prevalent as feline herpesvirus or feline calicivirus infections, it is evident that in some young feline populations Bordetella broncbiseptica infections significantly contribute to persistent acute respiratory tract disease. The intranasal vaccine currently available affords complete protection; however, upper respiratory disease, if it does occur, can be restricted to short courses and is mild (). Kittens may be vaccinated with the intranasal Bordetella broncbiseptica vaccine as young as 4 weeks of age.
Capillaria aerophila of dogs and cats and Oslerus (Filaroides) osleri of dogs are occasionally found in the trachea and bronchi of young animals. The clinical sign is usually a nonproductive cough. Nodules containing masses of mature and immature Oslerus (Filaroides) osleri may be detected near the tracheal bifurcation during endoscopy. Eggs or larvae of the parasites may be identified by fecal examination using a modified Baermann technique or cytologic examination of lavage solution obtained by transtracheal aspiration or tracheobronchial lavage. Successful treatment is usually possible with fenbendazole (50 mg/kg daily given orally for 10 to 21 days) or ivermectin (300 u,g/kg given orally or subcutaneously once). One month after therapy, eggs and larvae should have disappeared from the animal’s feces.
TRACHEAL AND BRONCHIAL TRAUMA
Tracheal and bronchial trauma are seen with penetrating wounds or blunt trauma to the cervical region or thorax. Overinflation of the cuff of an endotracheal tube during anesthesia can also result in trauma to the tracheal mucosa. Coughing, dyspnea, and persistent peritracheal, subcutaneous, or mediastinal emphysema after cervical or thoracic trauma indicate thorough evaluation of the airways. Small wounds are often self-limiting, but extensive tissue damage, which may accompany penetrating bites or gunshot wounds, may require immediate care. Immediate treatment of tracheal or bronchial trauma should center on maintaining a patent airway, providing oxygen, and treating shock and/or hemorrhage. Antiinflammatory doses of glucocorticoids may decrease edema and inflammation that is contributing to airway obstruction. Wounds may require surgical de-bridement and apposition after the animal is stable.
TRACHEAL AND BRONCHIAL FOREIGN BODY
Foreign objects that lodge in the trachea or bronchi are more commonly seen in puppies than in kittens, having been inhaled during normal play activities or while eating. Varying degrees of tracheal obstruction result in an obstructed breathing pattern and coughing. Subcutaneous emphysema may also be evident in the cervical area if tracheal integrity has been breached. Diagnosis of tracheal foreign objects is made by radiographic examination or, if necessary, endoscopy. Tracheal foreign objects that are free in the tracheal or bronchial lumen can occasionally be removed by holding the animal with the head down and rapidly compressing its thorax or by inducing a cough by tracheal palpation while the head is held in a lowered position. Otherwise, tracheal or bronchial foreign objects can be removed with a retrieving instrument passed through or along the side of a small endoscope (). Failing endoscopic removal, surgical intervention will be necessary.
Tracheal neoplasia of dogs and cats is uncommon. Tracheal osteochondroma (also referred to as tracheal osteochondral dysplasia), however, occurs in dogs younger than 6 months (). These growths are benign and are not aggressive locally. Affected dogs usually demonstrate coughing, exercise intolerance, and an obstructed breathing pattern. The growths are readily seen radiographically as solitary distinct intratracheal masses that may, on occasion, be ossified. Surgical removal is the treatment of choice.
Selections from the book: “Veterinary pediatrics: dogs and cats from birth to six months”. Johnny D. Hoskins. (2001)
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