this program is brought to you by trudel animal health canine infectious respiratory
disease complex is a syndrome of diseases that can be caused by several different bacterial
and viral pathogens these pathogens are awfully highly contagious and co-infections are very
common in these patients most times they have a very characteristic clinical appearance
and so usually the diagnosis can be suspected just with a brief history
vaccinations and comprehensive prevention strategies are important when dealing with
these diseases however even vaccines aren't 100 effective and don't fully induce sterilizing
immunity thus highlighting the importance of preventative strategies let's take a look at our
bacterial pathogens so we'll start with bordetella bronchoseptica commonly known as kennel cloth
this is a gram-negative coxal bacilli bacteria that's airborne and adheres to the cilia in dogs
these bacteria have an outer capsule which protects from defense mechanisms and it
allows secretions for bacterial colonization it also produces endotoxins or exotoxins
causing the necrosis of epithelial cells and it generally has a two to ten day incubation period
these will produce that classic cough that's normally seen in high populated areas such as
kennels or puppy mills and now let's take a quick second and review the anatomy of the upper airways
the upper airway starts with daenerys which lead into the nasal passages
inside of each nasal passage we'll find what are called turbinates
these are thin very scroll-like bones that are covered with nasal epithelium
there's a dorsal a ventral and an ethmoidal turbinate these will help divide each passage
into four main passageways or meatuses these nasal passages are lined with pseudostratified
columnar epithelial cells and they have on top of them cilia and mucous from mucous glands
and goblet cells found within we also find in the caudal dorsal aspect of these passageways sensory
neurons that lead to the olfactory nerve which is cranial nerve one this part of our upper airway is
very important as inhaled air is warmed humidified and filtered before it reaches the lungs in
the nasal passages we also find what are called paranasal sinuses these are ciliated out pouchings
of nasal passages and for each dog and cat there's about three pairs a frontal maxillary and spinodal
the function of these perinatal sinuses are still unknown once we go through our nasal passages
we end up in our pharynx the pharynx is a common passageway for the respiratory and the digestive
system it's divided by the soft palate into the nasal pharynx and the oral pharynx going on down
next we're at the larynx so this is going to be a musculocartilaginous organ that guards
the entrance to the trachea it's made up of four cartilages that surround the rhema glottis and
those are going to be a paired set of aretenoids and then unpaired epiglottis cricoid and thyroid
the larynx is very important for voice production as well as again protecting that trachea
the vocal cords are connective tissue that are attached to the arytenoid cartilages
and help us produce sound our next bacterial pathogen is streptococcus equi subspecies
zoo epidemicus this is an opportunistic bacteria that's a beta hemolytic lance field group c
streptococcus its incubation is roughly a couple days and it clinically manifests itself with
a severe bronchopneumonia its clinical disease in dogs is very similar to that
seeing with streptococcal exotoxin or toxic shock syndrome in people
mycoplasma is our next bacteria mycoplasma cyanos has a similar incubation period of
three to ten days it's also a commensal organism that's normally found in the mucosa in about 25
of dogs it's a fastidious organism that lacks a cell wall and it's actually one of the smallest
known free living organisms it's transmitted via aerosol and it's commonly found in younger dogs
secondary opportunistic bacterial pathogens that we may also see associated with these patients
include streptococcus canis pasteurella pseudomonas staph species e coli or klebsiella
pneumoniae now let's take a look at our viral pathogens we'll start with canine adenovirus ii
this is the non-enveloped double-stranded dna virus that infects our non-ciliated
bronchiolar epithelial cells it also impacts the epithelial cells of the nasal mucosa
our pharynx on our tonsillar crypts our mucous cells in our trachea and the bronchi and type 2
alveolar cells it has an incubation period of three to six days and clinically manifests
with mild upper respiratory signs and a harsh cough usually for about two weeks in duration
the stem provirus is found in the genus morbili virus and family paramyxo it has an
incubation period of three to six days and it's an enveloped rna virus that can cause a myriad
of clinical signs primarily dealing with the respiratory gastrointestinal and neurologic system
classically we see these patients with respiratory pneumonia gastrointestinal signs such as vomiting
neurologic signs with changes in mentation photosensitivity seizure episodes
this is a highly contagious virus that's spread via aerosol particles initially
infect the monocytes within the lymphoid and the tonsillar tissues of the upper respiratory tract
and then disseminate throughout the body via the lymphatic system
canine this tempura virus is shed from all bodily secretions starting at five days after infection
and that shedding can actually continue for up to four months hence the virulence of the virus
other clinical signs can include ocular changes
hard pad keratosis as well as changes to the nasal plenum influenza virus so canine influenza virus
strain h3n2 and h3n8 are segmented negative sense rna genomes that are enveloped viruses
canine influenza virus belongs to the family orthomixo and the genus alpha influenza virus
it's also further subtyped based on its hemo agglutin h and neuromonadase gene
canine influenza virus was actually first documented in florida in 2004
with another strain subsequently following in chicago in 2015.
it has a pretty short incubation period of about two to four days
and the clinical signs can range from subclinical to severe respiratory signs before we get any
further let's take a quick second and go over the anatomy of the lower airways first is the trachea
so the trachea extends from our cricoid cartilage of the larynx and it goes all the way down up
until it's bifurcation at the carina within the thoracic cavity the trachea is composed of 35
c-shaped cartilage rings of hyaline cartilage with the open part facing dorsally essentially
that tracheal will bifurcate into bronchi and they're lined with ciliated epithelial cells
from our primary bronchi we'll go down to lobar bronchi and it'll keep dividing into
our segmental bronchi from there we'll keep dividing and form our bronchioles
and then our alveolar ducts division continues and we'll start to see the formation of our alveolar
sacs and then our alveoli which are like grapes and this is going to be the site of external
respiration so our alveoli are going to be thin walled sacs of simple squamous epithelial cells
surrounded by capillaries the sacs are going to be thin for again be able to do oxygen exchange and
they're also going to be lined with what's called surfactant which is going to be very important
for lung compliance or stretchability of that lung the lungs themselves are divided into lobes
the hylus is the center of the lobe where we see air blood lymph and nerve enter and leave the lung
in the dog and the cat there's going to be four lobes on the right side of the chest and two lobes
on the left side with the cranial lobe on the left being divided into a cranial and a caudal segment
now if we take a step back and look at the entire thoracic cavity that these lungs are held within
the thoracic cavity is going to be lined with pleura pleura is a very thin serous membrane
that's composed of about five layers there's a visceral pleura that covers the actual lungs
and that helps to provide support and a parietal pleura which covers the chest wall
and that's going to form a space and that space in between them is what's known as the pleural cavity
within that cavity we see an area called the mediastinum and this is going to be an
area or space that's formed between the lungs that holds the heart the trachea
the esophagus major blood vessels nerves and lymphatics that mediastinum can be broken up into
a cranial segment which is going to be mostly our trachea our esophagus our thymus and our sternal
lymph nodes a ventral portion which has our thymus and our frontal pericardial ligament which
attaches our pericardial sac to our diaphragm and a middle segment which is going to contain
the heart and of course some major pulmonary vessels the aorta and a couple lymph nodes so
now that we have our pleural space we'll look at our actual thoracic cavity itself and thoracic
cavity externally is made up of our rib cage dogs and cats have 13 pairs of ribs on each side
the caudal segment of our thoracic cavity is made up by the diaphragm
which is a musculocutaneous partition between the thoracic and the abdominal cavity this
diaphragm has a tendinous center with three thin peripheral muscles that it uses for attachment
the diaphragm has a convex shape and it extends into the thorax and it actually accounts for
about 75 percent of change in the intrathoracic volume para influenza virus is an enveloped single
stranded negative sense rna virus that belongs to the family paramixo and the genus rubella
and it's closely related to the simian virus 5. it has an incubation period of about 3-10 days
and it's highly contagious with upper respiratory signs lasting up to 10 days
canine respiratory coronavirus is a group 2a coronavirus in the family corona
verde and is an enveloped rna virus this virus was first described in a group of shelter dogs
with respiratory disease in 2003 in the united kingdom is now has been identified worldwide
it has a variable incubation period and its clinical signs manifest as
subclinical to very mild upper respiratory signs
canine herpes virus one this is an enveloped double-stranded dna virus
its incubation period can last anywhere from six to ten days and it's usually a disease of
neonates producing subclinical or very mild respiratory signs if it does impact an adult
the major clinical manifestation of the herpes virus is reproductive failure in female dogs
other potential viruses that we can see as secondary viruses include canine pneumovirus which
is probably one of the newer pathogens that we find being associated with this infectious disease
complex in dogs most of these diseases both viral and bacterial can be prevented with good strategic
husbandry again most of these incubation periods overlap each other and the infection rates of
these dogs come into play when they're in close housing whether that's at the grooming facility
at pet stores at the vet's office anywhere that they don't have proper vaccination on board
hence the importance of all your puppy vaccines and the preventative care that comes with that
also commonly being available to primary care veterinarians is the availability of
pcr testing and being able to detect these organisms so we can actually see what the
prevalence is out in the population all right let's take what we just covered and take a look
at an infectious respiratory disease case in a dog alright so this is scruffy he's a five-year-old
male neutered mixed breed dog who presents to your clinic with signs of coughing lethargy and
a mild fever of 103.5 degrees fahrenheit scruffy is a social butterfly who does go to doggy daycare
visits the dog park at least once a week and also goes to the groomer at least once a month the pet
owner mentions that several other dogs at doggy daycare have been sick lately scruffy has examined
at your clinic so with that patient history what do you think is the next best thing for us to do
so what did you guys think as always you want to make sure that you do as thorough of a physical
exam as possible so you want to make sure that you auscultate the lungs examine the oral cavity
and of course get as much information about the history of the dog
including vaccine status and home environment as possible all right so we do our thorough physical
exam and pe findings include that the dogs and mucous membranes are dry lung sounds are harsh
and the respiratory issues all seem to be confined to the lower respiratory tract so now
that we know what part of the respiratory tract is affected what would your next diagnostic step be
all right so what do you guys think while all these diagnostics can help provide supplemental
information the most non-invasive direct form of getting a definitive diagnosis is going to
be pcr testing so we submit our pcr and results confirm canine influenza h3n2 treatment for canine
influenza virus is focused on supportive care that means using nebulizers to help with breathing
non-steroidal anti-inflammatory drugs can also be used to lower the fever and broad
spectrum antibiotics can be used to treat secondary opportunistic bacterial infections
in this case this dog is a risk to other dogs this dog should be quarantined to help stop the
spread of the disease remember vaccines are not 100 protective against canine influenza
but they can greatly reduce the severity of the infection and help minimize the spread