Canine influenza
Encyclopedia
Canine influenza is influenza
occurring in canines
. Canine influenza is caused by varieties of Influenzavirus A
, such as equine influenza virus H3N8, which in 2004 was discovered to cause disease in dogs. Because of the lack of previous exposure to this virus, dogs have no natural immunity
to this virus. Therefore, the disease is rapidly transmitted between individual dogs. Canine influenza may be endemic
in some regional dog populations of the United States
. It is a disease with a high morbidity but a low mortality
.
race dog
fatalities from a respiratory illness at a Florida
racetrack in January 2004. The exposure and transfer apparently occurred at horse racing
tracks, where dog racing also occurs. This was the first evidence of an influenza A virus causing disease in dogs. However, serum
collected from racing Greyhounds between 1984 and 2004 and tested for canine influenza virus (CIV) in 2007 had positive tests going as far back as 1999. It is possible that CIV caused some of the respiratory disease outbreaks at tracks between 1999 and 2003.
H3N8 was also responsible for a major dog flu outbreak in New York
state in all breeds of dogs. From January to May 2005, outbreaks occurred at 20 racetracks in 10 states (Arizona
, Arkansas
, Colorado
, Florida, Iowa
, Kansas
, Massachusetts
, Rhode Island
, Texas
, and West Virginia
). As of August 2006, dog flu has been confirmed in 22 U.S. states, including pet dogs in Wyoming, California, Connecticut, Delaware, and Hawaii. There are three areas in the United States that may now be considered endemic for CIV due to continuous waves of cases: New York, southern Florida, and northern Colorado/southern Wyoming. There is no evidence that the virus can be transferred to people, horses, cats, or other species.
H5N1
(avian influenza) was also shown to cause death in one dog in Thailand
, following ingestion of an infected duck
.
negative sense
single-stranded RNA virus
es. Genome analysis has shown that H3N8 was transferred from horses to dogs and then adapted to dogs through point mutation
s in the gene
s. The incubation period
is two to five days and viral shedding
may occur for seven to ten days following the onset of symptoms. It does not induce a persistent carrier
state.
s), and the fatality rate for Greyhounds in early outbreaks was 5 to 8 percent, although the overall fatality rate in the general pet and shelter population is probably less than 1 percent. Symptoms of the mild form include a cough that lasts for ten to thirty days and possibly a greenish nasal discharge. Dogs with the more severe form may have a high fever and pneumonia
. Pneumonia in these dogs is not caused by the influenza virus, but by secondary bacteria
l infections. The fatality rate of dogs that develop pneumonia secondary to canine influenza can reach 50 percent if not given proper treatment. Necropsies in dogs that die from the disease reveal severe hemorrhagic pneumonia and evidence of vasculitis
.
increases suspicion of infection with canine influenza, especially in areas where the disease has been documented. A serum
sample from a dog suspected of having canine influenza can be submitted to a laboratory that performs PCR
tests for this virus.
(USDA) Animal and Plant Health Inspection Service
(APHIS) approved the first canine influenza vaccine. This vaccine must be given twice initially with a 2 week break and then annually thereafter. Because any vaccine can have negative side effects on some dogs, many dog owners are choosing not to vaccinate due to the fact that most dogs recover from the flu with mild symptoms and research indicates that after a dog has recovered from canine influenza, immunity appears to last at least 2 years.
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
occurring in canines
Canidae
Canidae is the biological family of carnivorous and omnivorous mammals that includes wolves, foxes, jackals, coyotes, and domestic dogs. A member of this family is called a canid . The Canidae family is divided into two tribes: Canini and Vulpini...
. Canine influenza is caused by varieties of Influenzavirus A
Influenzavirus A
Influenza A virus causes influenza in birds and some mammals and is the only species of Influenzavirus A. Influenzavirus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon...
, such as equine influenza virus H3N8, which in 2004 was discovered to cause disease in dogs. Because of the lack of previous exposure to this virus, dogs have no natural immunity
Immunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...
to this virus. Therefore, the disease is rapidly transmitted between individual dogs. Canine influenza may be endemic
Endemic (epidemiology)
In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...
in some regional dog populations of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. It is a disease with a high morbidity but a low mortality
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
.
History
The highly contagious equine influenza A virus subtype H3N8 was found to have been the cause of GreyhoundGreyhound
The Greyhound is a breed of sighthound that has been primarily bred for coursing game and racing, and the breed has also recently seen a resurgence in its popularity as a pedigree show dog and family pet. It is a gentle and intelligent breed...
race dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
fatalities from a respiratory illness at a Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
racetrack in January 2004. The exposure and transfer apparently occurred at horse racing
Horse racing
Horse racing is an equestrian sport that has a long history. Archaeological records indicate that horse racing occurred in ancient Babylon, Syria, and Egypt. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 648 BC...
tracks, where dog racing also occurs. This was the first evidence of an influenza A virus causing disease in dogs. However, serum
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
collected from racing Greyhounds between 1984 and 2004 and tested for canine influenza virus (CIV) in 2007 had positive tests going as far back as 1999. It is possible that CIV caused some of the respiratory disease outbreaks at tracks between 1999 and 2003.
H3N8 was also responsible for a major dog flu outbreak in New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
state in all breeds of dogs. From January to May 2005, outbreaks occurred at 20 racetracks in 10 states (Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
, Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, Florida, Iowa
Iowa
Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...
, Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
, Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, Rhode Island
Rhode Island
The state of Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a state in the New England region of the United States. It is the smallest U.S. state by area...
, Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, and West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...
). As of August 2006, dog flu has been confirmed in 22 U.S. states, including pet dogs in Wyoming, California, Connecticut, Delaware, and Hawaii. There are three areas in the United States that may now be considered endemic for CIV due to continuous waves of cases: New York, southern Florida, and northern Colorado/southern Wyoming. There is no evidence that the virus can be transferred to people, horses, cats, or other species.
H5N1
H5N1
Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
(avian influenza) was also shown to cause death in one dog in Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
, following ingestion of an infected duck
Duck
Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...
.
The virus
Influenza A viruses are envelopedViral envelope
Many viruses have viral envelopes covering their protein capsids. The envelopes typically are derived from portions of the host cell membranes , but include some viral glycoproteins. Functionally, viral envelopes are used to help viruses enter host cells...
negative sense
Sense (molecular biology)
In molecular biology and genetics, sense is a concept used to compare the polarity of nucleic acid molecules, such as DNA or RNA, to other nucleic acid molecules...
single-stranded RNA virus
RNA virus
An RNA virus is a virus that has RNA as its genetic material. This nucleic acid is usually single-stranded RNA but may be double-stranded RNA...
es. Genome analysis has shown that H3N8 was transferred from horses to dogs and then adapted to dogs through point mutation
Point mutation
A point mutation, or single base substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA. Often the term point mutation also includes insertions or deletions of a single base pair...
s in the gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s. The incubation period
Incubation period
Incubation period is the time elapsed between exposure to a pathogenic organism, a chemical or radiation, and when symptoms and signs are first apparent...
is two to five days and viral shedding
Viral shedding
Viral shedding refers to the successful reproduction, expulsion, and host-cell infection caused by virus progeny. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell by several methods.The term is used...
may occur for seven to ten days following the onset of symptoms. It does not induce a persistent carrier
Asymptomatic carrier
An asymptomatic carrier is a person or other organism that has contracted an infectious disease, but who displays no symptoms. Although unaffected by the disease themselves, carriers can transmit it to others...
state.
Symptoms
About 80 percent of infected dogs with H3N8 show symptoms, usually mild (the other 20 percent have subclinical infectionSubclinical infection
A subclinical infection is the asymptomatic carrying of an by an individual of an agent that usually is a pathogen causing illness, at least in some individuals. Many pathogens spread by being silently carried in this way by some of their host population...
s), and the fatality rate for Greyhounds in early outbreaks was 5 to 8 percent, although the overall fatality rate in the general pet and shelter population is probably less than 1 percent. Symptoms of the mild form include a cough that lasts for ten to thirty days and possibly a greenish nasal discharge. Dogs with the more severe form may have a high fever and pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
. Pneumonia in these dogs is not caused by the influenza virus, but by secondary bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l infections. The fatality rate of dogs that develop pneumonia secondary to canine influenza can reach 50 percent if not given proper treatment. Necropsies in dogs that die from the disease reveal severe hemorrhagic pneumonia and evidence of vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
.
Diagnosis
The presence of an upper respiratory tract infection in a dog that has been vaccinated for the other major causes of kennel coughKennel cough
Kennel cough is a highly contagious canine illness characterized by inflammation of the upper respiratory system. It can be caused by viral infections such as canine distemper, canine adenovirus, canine parainfluenza virus, or canine respiratory coronavirus, or bacterial infections such as...
increases suspicion of infection with canine influenza, especially in areas where the disease has been documented. A serum
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
sample from a dog suspected of having canine influenza can be submitted to a laboratory that performs PCR
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
tests for this virus.
Vaccine
In June 2009, the United States Department of AgricultureUnited States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
(USDA) Animal and Plant Health Inspection Service
Animal and Plant Health Inspection Service
Animal and Plant Health Inspection Service is an agency of the United States Department of Agriculture responsible for protecting animal health, animal welfare, and plant health. APHIS is the lead agency for collaboration with other agencies to protect U.S. agriculture from invasive pests and...
(APHIS) approved the first canine influenza vaccine. This vaccine must be given twice initially with a 2 week break and then annually thereafter. Because any vaccine can have negative side effects on some dogs, many dog owners are choosing not to vaccinate due to the fact that most dogs recover from the flu with mild symptoms and research indicates that after a dog has recovered from canine influenza, immunity appears to last at least 2 years.
Further reading
- A New Deadly, Contagious Dog Flu Virus Is Detected in 7 States The New York Times
- States that have identified dogs with CIV
- Canine Influenza from The Pet Health Library
- Canine Influenza from Veterinary Partner
- Canine Influenza Fact Sheet Center for Food Security and Public Health (CFSPH), Iowa State University College of Veterinary MedicineIowa State University College of Veterinary MedicineIowa State University's College of Veterinary Medicine was established in 1879 and is the oldest veterinary college in the United States. Iowa State has graduated 6,400 veterinarians and is one of the largest veterinary research facilities in the nation....
- AVMA Backgrounder: canine influenza