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13 Cards in this Set
- Front
- Back
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Orthomyxoviridae
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-Contain those viruses that cause influenza in humans and animals
-Enveloped viruses with helical nucleocapsids and spherical or pleomorphic morphology -LInear, negative-sense, single-stranded RNA -Replication occurs in the nucleus -Two important glycoproteins *haemogglutinin (H) *neuroraminidase activity (N) -Genome is segmented, facilitating genetic reassortment -Subtypes of Influenza A are important human, avian, porcine, and equine pathogens |
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Neuraminidase (N)
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-Cleaves the sialic acid containing receptor to the virion
-Degrades mucus -Promotes both entry of virus into cells and release of virions from infected cells -Inhibitors block the release of the virus, halting virus replication *Examples: Tamiflu (oral) and Relenza (inhalation) |
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Haemagglutinin molecule (H)
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-Bind to cell receptors
-Responsible for virus attach and envelope fusion |
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Classification of Influenza viruses
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-Type of Influenza virus
-Host spp -Geographical origin -Strain number -Year of isolation -Subtype (H or N) |
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Epidemiology of Influenza A viruses
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-Birds are the reservoir hosts (waterfowl): virus replicates in their intestines
-Cause significant infections in humans, pigs, horses and birds -Efficient fecal/oral transmission from migrating aquatic birds -Jumps the species barrier -Hemagglutinin is the major determinate for host range *different spp have different side chain linkages |
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Swine Influenza
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-Highly contagious respiratory disease of pigs
-Most common subtypes: H1N1 (classical and avian-like), H1N2 (human-avian reassortants), and H3N2 (human and avian-like) -Usually assoc with recent introduction into a herd -Principle route of transmission is by direct contact *aerosol transmission may occur under suitable weather conditions in areas with high pig populations -Incubation period 24-72 hrs -Usually occurs in Fall or Winter -Clinical signs: nasal discharge, paroxysmal coughing, fever, conjunctivitis, pneumonitis, abortion, loss of weight -Recovery within 10 days |
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What was the last influenza pandemic that occurred in humans?
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H1N1 in 2009
-Droplet transmission |
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Avian influenza
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-In birds, particularly waterfowl
-Shed in feces -Survives for long periods in water -Many strains asymptomatic -Clinical signs: sudden death, cessation of egg laying, respiratory diseases, lacrimation, sinusitis, diarrhea, edema of the head, face and neck, cyanosis of the comb and wattles -Control: notifiable to national regulatory authorities (OIE), movement restrictions, slaughter those infected in countries free of disease, vaccine in some countries -H5N1 could lead to a human pandemic |
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Equine influenza
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-Equine viruses of avian origin
-H7N7 (may be extinct) and H3N8 -H3N8 is most important cause of respiratory disease, almost worldwide -Outbreaks in vaccinated populations -Outbreaks assoc. with movement and assembly of horses for shows, sales, racing, or training -Highly contagious -Shed in aerosols (coughing), windborne aerosol, and contamination of clothing/equipment/vehicles -Clinical signs: elevation in temp, dry deep cough, nasal discharge, enlarged lymph nodes, inappetence, limb oedema, secondary bacterial infection, pneumonia, abortion, neurological signs -Recovery within two weeks |
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Diagnosis of Equine Influenza
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- Paired clotted blood samples for serology 10-14 days apart (4 fold rise in antibody titre)
-Nasopharyngeal swab for virus isolation -ELISA -PCR: most sensitive |
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Control of Equine influenza
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-Mandatory vaccination of highly mobile horses
*boosters required for different type of horses (racehorses, competition) -Vaccination and boosters recommended for all horses |
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Treatment of Equine influenza
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-Rest 1 week for 1 day pyrexia
-Nursing and supportive care -Anti-inflammatories and antibiotics -Vaccination in face of outbrreak |
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Equine influenza virus in dogs
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-High seroprevalence in dogs
-80% respiratory disease -Fever and cough for 10-14 days with subsequent recovery -Sometimes peracute death with hemorrhage in the respiratory tract -Mortality rate 5% (used to be 36%) |
