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canine influenza (Important info )
#1
Canine Influenza.
THIS IS AN IMPORTANT ARTICLE IN PART DUE TO WHAT IS OCCURRING ACROSS USA SHOW CIRCUIT
You all MUST learn to recognise this virus and stop its transmission if its in the show circuits of your country. Dead dogs don’t wear rosettes !
 
Canine influenza or dog flu is of recent occurrence (2004) and is an acute, highly contagious respiratory infection of relatively short duration and low mortality caused by an influenza A virus thought to be of equine origin. Influenza A virus, closely related to subtype H3N8 and presumed to have been acquired from a horse(s). Subtype H3N8 virus is a frequent cause of equine influenza. The transmission of influenza from horses to dogs is especially interesting in light of the fact that dogs were not commonly regarded as hosts for influenza A viruses. Although circumstantial evidence from surveillance studies indicates that human-lineage influenza viruses occasionally cross the species barrier to dogs, none of these human viruses are known to have spread efficiently within the canine population. Although the disease was first seen in race tracks it has since spread to veterinary clinics, boarding facilities and animal shelters. Infection is via the respiratory tract and spread is mainly by infectious aerosols resulting from coughing but also indirectly by fomites. The incubation period is 2 - 5 days and the course in uncomplicated cases is 1 - 3 weeks. The majority of affected dogs show mild disease with older dogs and puppies more severely affected. Among the clinical signs are fever, coughing, dyspnoea, anorexia, depression and mucoid to purulent nasal discharge. The severe, infrequent form is characterized by pneumonia with secondary bacterial infection. The fatality rate has ranged around 10%. Unfortunately canine influenza can only be distinguished from other respiratory infections by laboratory means. Diagnosis can be confirmed through serological testing for antibodies to canine influenza virus. Influenza viruses belong to the Orthomyxoviridae (“straight mucus”), and are further subdivided into Types A, B, and C. Canine Influenza Virus is a Type A virus, as are Avian, Swine, Equine, and seasonal influenza virus of people. There is a non-seasonal influenza of people in the Type B category, and an uncommon form of human and swine influenza in the Type C category. Migratory waterfowl are considered the natural hosts of the influenza virus, and in those birds this virus is found in the gastrointestinal epithelium. It is so well adapted to its host that low-path strains of influenza virus causes no overt symptoms of disease (high path avian influenza strains can cause a wide range of clinical pathology, including GI, cardiac, pulmonary, CNS, peripheral nervous tissue damage in water fowl). The migratory patterns of waterfowl assure that this virus has a worldwide distribution, and because of the ease with which viral particles in waterfowl feces can be distributed, it is no marvel that influenza viruses spill into other species. In mammals, influenza is a respiratory disease, with inoculation of the respiratory epithelium (usually via nasal or tracheal epithelial contact) causing binding of the HA to the epithelia cells’ surface glycoproteins. Ratios of particular glycoside residues are species dependent, and alter the binding affinity of the HA. Mutations in the HA regions responsible for binding to epithelial cell glycoproteins may alter the ability of a viral particle to bind to a new host species with a different ratio of expressed surface sialic acid residues. Binding is followed by a rapid influx of proton (H-) via the M2 ion channel in the viral capsule; an acid environment is essential for viral replication, as the RNA polymerases are effective only in an acid intracellular environment. In mammals, the entire respiratory tract epithelium can be infected, from the nasal passages all the way down to the terminal alveoli, and influenza virus can replicate within alveolar macrophages, too. Canine Influenza Virus Canine Influenza Virus (CIV) was first isolated from an outbreak of respiratory illness in a greyhound kennel, where 8 of 22 affected dogs died from severe acute pulmonary hemorrhage. One of these dogs yielded a sample from lung tissue, which was positive for influenza virus. Previous field and experimental work had established that dogs could be infected with avian influenza viruses, but in none of those instances were dogs proven capable of infecting other dogs—horizontal transmission. In the 2004 greyhound outbreak, it was not immediately clear whether this was a spillover infection of equine H3N8 into greyhounds, or whether this particular influenza had established itself in a new host and was now capable of horizontal transmission. Further examination of banked sera from other respiratory outbreaks in greyhounds demonstrated presence of CIV as early as 2000 in greyhounds. Since 2004, this disease has been demonstrated in 35 states and is consider enzootic in Florida, New York, New Jersey, Pennsylvania, and Colorado. Retrospectively, an outbreak of respiratory disease in English foxhounds in 2002 was demonstrated to be an H3N8 equine influenza virus, though horizontal transmission did not appear to be established in the dogs in that event. Additionally, equine and canine sialic acid linkages were compared in that retrospective work, demonstrating that dogs and horses share preferential expression of SA alpha2,3 linkages, which may explain why equine influenza may have spread to dogs on multiple occasions. While CIV is the focus of much current interest, it also illustrates the importance of continued vigilance and diagnostics for other contagious respiratory pathogens of dogs. Canine Infectious Respiratory Disease Complex is a constellation of bacterial and viral pathogens, which can cause a range of overlapping or identical signs in dogs, from subclinical or inapparent signs to severe hemorrhagic pneumonia
 
Distribution/Occurrence
Dog flu first occurred in greyhounds in Florida, USA in January 2004. Of the dogs affected by the outbreak about 30% died. The disease was first seen in race tracks but has since spread to veterinary clinics, boarding facilities and animal shelters. Infections have also been confirmed in New York and a number of other states.
Susceptibility
Susceptibility is broad in unexposed dogs. Older dogs and puppies may be more severely affected.
Mode of Infection/Transmission
Infection is via the respiratory tract and spread is mainly by infectious aerosols resulting from coughing but also indirectly by fomites.
Incubation Period/Course
The incubation period is 2 - 5 days and the course in uncomplicated cases is 1 - 3 weeks.
Clinical Features
It appears that the disease is less severe than earlier thought and about 80% of those infected come down with a mild disease. Among the clinical signs are fever, coughing, dyspnea, anorexia, depression and mucoid to purulent nasal discharge. The severe, infrequent form is characterized by pneumonia with secondary bacterial infection. The fatality rate has ranged from 5 - 8% in the early outbreaks among greyhounds but somewhat less in later outbreaks in other breeds.
Diagnosis
Dog flu can only be distinguished from other respiratory infections, such as kennel cough which it resembles clinically, by laboratory means.
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