What you need to know about infectious respiratory disease in dogs
Dogs that are social or visit pet businesses, like doggie day cares, groomers, boarding facilities, and dog parks, are at risk for infectious diseases, including those that cause coughing.
Multiple bacterial and viral pathogens can result in clinical signs of canine infectious respiratory disease complex. Outbreaks associated with canine cough are very common and reported worldwide.
Pathogens associated with disease are transmitted via the aerosol route through direct or indirect contact with fomites. Most have short incubation periods ranging from a few days up to 2 weeks.
Bacterial pathogens
Bordetella bronchiseptica is a gram-negative coccobacilli that can cause respiratory disease in many species, including dogs, cats, pigs, rabbits, and people.
Bordetella is considered highly contagious. The incubation period ranges from 2 to 10 days. Most cases are mild and involve the upper-respiratory tract. The organism can be shed for at least 1 month, and in some cases, for several months.
Streptococcus equi Subspecies zooepidemicus is a β-hemolytic, streptococcus organism.
Strep zoo has been associated with acute, severe bronchopneumonia in dogs. Outbreaks of severe hemorrhagic pneumonia from it has been described in group-housed dogs.
Dogs initially have mild clinical signs, including a cough and nasal discharge; however, their clinical signs can rapidly progress within 24 to 48 hours of onset, resulting in development of severe acute fibrinosuppurative, necrotizing, and hemorrhagic bronchopneumonia.
Mycoplasma spp. Are gram negative, non-acid fast prokaryotes that lack a cell wall.
Mycoplasmas are currently divided into hemotropic and non-hemotropic types.
Mycoplasmas can be difficult to identify and the pathogenesis of disease is unclear. Most cases of disease are mild in severity.
Viral pathogens
Canine Adenovirus 2, is a nonenveloped double-stranded DNA virus of the family Adenoviridae. The virus infects the non-ciliated bronchiolar epithelial cells, the epithelial cells of the nasal mucosa, pharynx, and tonsillar crypts and the mucous cells in the trachea and bronchi.
Clinical signs are most often mild and consist of sneezing, nasal discharge, and a dry cough.
The incubation period is 3-6 days and viral shedding typically wanes 1 to 2 weeks after infection. The virus can survive in the environment for weeks to months.
Canine distemper virus is in the genus Morbillivirus and family Paramyxoviridae. It is an enveloped RNA virus that can cause clinical signs involving the respiratory, neurologic, and gastrointestinal systems.
Canine distemper is highly contagious and spreads through aerosol secretions.
Viral particles initially infect monocytes within the lymphoid and tonsillar tissues of the upper-respiratory tract and then disseminate throughout the body through the lymphatics.
CDV also infects lymphocytes and causes widespread lymphocyte destruction which results in lymphopenia. The virus is shed through secretions and shedding can continue for up to 4 months.
Fortunately, because of the viral envelope, environmental survival is only several hours, and routine disinfectants will inactivate the virus.
Canine distemper can be fatal. Dogs with the disease can have a wide variety of clinical signs including diarrhea and vomiting, ocular discharge, and various neurologic signs.
Canine influenza viruses are enveloped RNA viruses. Canine influenza belongs to the family Orthomyxoviridae and is further subtyped based on its hemagglutinin (H) and neuraminidase (N) genes.
H3N8: The first documented cases of canine influenza H3N8 were found in Florida racing greyhounds in 2004. The virus then spread throughout the country, mostly being reported in kennels and shelters, and sporadically within the pet population.
H3N2: In 2015, an outbreak H3N2 canine influenza was identified for the first time in the US. This subtype was similar to a strain previously reported in South East Asia and was suspected to be the result of a mutated avian influenza virus. Since 2015, this strain of CIV has spread throughout the United States and reintroductions from Asia have resulted in the appearance of additional outbreaks.
Canine influenza can cause a wide range of severity, from mild to severe. Clinical signs associated include lethargy, cough, nasal and ocular discharge, and occasionally more severe clinical signs associated with pneumonia and death.
Viral shedding from H3N2 has been reported to last up to 24 days.
Canine Parainfluenza Virus is an enveloped single-stranded RNA virus belonging to the family Paramyxoviridae.
Parainfluenza is highly contagious and is found worldwide. Before introduction of vaccines, this virus could be isolated from up to 50% of kenneled dogs with respiratory disease.
Parainfluenza, is also spread via respiratory droplets, and infection occurs within the respiratory epithelial cells. The incubation period is between 3-6 days.
Dogs can exhibit no clinical signs or mild clinical signs of a dry, harsh cough for several days with or without pyrexia.
The envelope of the virus renders it susceptible to inactivation by most commercial disinfectants.
Canine Respiratory Coronavirus is a group 2 coronavirus in the family Coronaviridae and is an enveloped RNA virus.
This virus was first described in a group of shelter dogs with respiratory disease in 2003 in the UK and has now been identified in dogs worldwide.
Infection with canine coronavirus is usually associated with mild clinical signs, including nasal discharge, cough, and sneezing.
Although respiratory tissue appears to be the primary site of viral replication, the virus has also been detected in the stool or intestines of dogs that presented with primary respiratory disease in the absence of GI signs. Viral shedding can occur up to 10 days after infection.
Diagnosis of canine cough:
Clinical diagnosis is usually made with just a history of exposure to other dogs, typical clinical signs, and a physical examination. Complete blood count may show evidence of inflammation, including mild to moderate neutrophilia, presence of band neutrophils, orlymphopenia.
Thoracic radiographs are recommended for cases of moderate to severe illness.
Confirmatory laboratory testing:
PCR testing has become a popular test for respiratory disease. Respiratory panels have been developed that detect the nucleic acid from pathogens, including CPIV, CAV-2, CDV, CRCoV, CHV, CIV, B bronchiseptica, and Mycoplasma sp.
Swabs of the nasal cavity, oropharyngeal cavity, or specimens collected from the lower-respiratory tract can be submitted for testing but false negative are possible with low or intermittent shedding or inappropriate sample handling. PCR testing is best performed on samples that are less than 3 days old. Vaccination within the previous few weeks with live-attenuated vaccines can lead to false positive results.
Serologic assays for measurement of antibodies are also available; however, their clinical use is limited because antibodies occurring in response to vaccination cannot be distinguished those produced from disease.
Treatment:
Treatment of dogs with uncomplicated respiratory disease usually involves supportive care and may include hydration and nutritional support, oxygen therapy, nebulization, and coupage.
Expectorant medications, such as guaifenesin are not recommended. Antiviral therapy is not recommended
Treatment of bacterial pathogens, B bronchiseptica, or opportunistic secondary pathogens should be guided by culture and susceptibility testing, because of antimicrobial resistance issues. Doxycycline is the antibiotic of choice for suspected B bronchiseptica or M cynos infection.
Prevention:
Vaccination protocols for dogs that are social or visit pet businesses, like doggie day cares, groomers, boarding facilities, and dog parks should include vaccines that protect against CPIV, CAV-2, CDV, CIV H3N8 & H3N2, and B. bronchiseptica.
References:
Reference: Greene CE, ed. Infectious Diseases of the Dog and Cat. 4th ed. St. Louis, MO: Saunders/Elsevier; 2012
