Transcript Influenza A Zoonosis

Influenza A Zoonosis
Saad Gharaibeh BVM, PhD, Dip ACPV
Dept. of Pathology and Animal Health
Faculty of Veterinary Medicine
Jordan University of Science and Technology
Irbid 22110, Jordan
NI test
HI test
AGP test
ELISA test
Jong et al., 2000, Journal of Infection
Dr. Gary Butcher specializing in avian
diseases, and has a Ph.D. in poultry virology.
"The threat is basically zero,“
"We're spending all of our
attention on this [virus],
and another one may
sneak up on us."
http://news.bbc.co.uk/2/hi/americas/8021547.stm
Influenza History
• Avian influenza was first described in 1878 as fowl
plaque disease in Italy. The causative agent was isolated
in 1902 (A/chicken/Brescia/1902 [H7N7]). By 1955, it
was characterized as influenza virus.
• In 1930, influenza virus, A/swine/Iowa/30, was isolated.
• In 1933, the first human virus was isolated in London,
England.
Previous Influenza Pandemics
• Spanish flu (1918-1919): H1N1
 Asian flu (1957): H2N2
 Hong Kong flu (1968): H3N2
 Russian flu (1977): H1N1
http://en.wikipedia.org/wiki/Swine_influenza
Field’s virology, 3rd ed
Pig Involvement
A number of findings have suggested a role for pigs in the
emergence of pandemic influenza viruses:
1. Pigs can be naturally or experimentally infected with avian
viruses.
2. Epithelial cells in pig trachea contain both human- and aviantype receptors
3. In nature, continued replication of an avian virus in pigs leads to
variants that preferentially recognize human-type receptors
4. Swine viruses and avian-human reassortant viruses can infect
humans and, in some cases, cause fatal disease
5. Interspecies transfer and reassortment events have led to the
establishment of two new lineages of pig viruses since 1979,
demonstrating that pigs can host genetically diverse viruses
Pig Involvement
• Swine influenza is enzootic in pigs and is the most
prevalent respiratory disease in these animals
• in 1918 and 1919, pigs presented with symptoms similar
to those observed in humans, that is, nasal discharge,
coughing, fever, labored breathing, and conjunctivitis.
• Phylogenetic analyses indicated that the 1918/1919
human and swine viruses were genetically similar and
likely originated from a common ancestor.
Main Influenza Groups in Pigs
• Classical swine viruses H1N1 (1918-1976) America and
Europe
• Avian-like H1N1 (after 1979) America and Europe
• Human-like viruses H3N2 after 1970 in Taiwan.
• Reassortant Viruses H1N2 viruses (after 1978 in Japan)
that resulted from reassortment of classical H1N1 swine
viruses and human H3N2 viruses
• H3N2 triple human/avian/swine reassortant viruses
emerged in North America (1998)
Field’s virology, 5th ed
Swine-Human Virus Exchange
• 1938, serologic evidence for the transmission of a human
virus to pigs.
• 1976, an H1N1 swine virus was isolated from a soldier
who had died of influenza at New Jersey. This virus was
subsequently isolated from five other soldiers, and
serologic studies suggest that more than 500 personnel
were infected.
• Numerous other reports have described the transmission
of swine viruses to humans, and transmission of human
viruses to pigs.
• Avian H9N2 and H5N1 viruses have from Southeast Asia.
Done and Brown, 1999
Pathogenesis in Pigs
• Morbidity may be up to 100%
• Mortality rate is low and recovery is rapid
• Secondary bacterial infections can increase the severity of
illness and may result in complications such as
pneumonia.
• Once a herd is infected, the virus is likely to persist
through the production of young susceptible pigs and the
introduction of new stock.
• Outbreaks of disease occur throughout the year but
usually peak in the colder months.
Pathogenesis in Pigs
• Infection is often subclinical and typical signs are seen in
only 25 to 30% of a herd.
• Disease transmission is primarily direct and occurs via the
nasopharyngeal route through the dispersal of aerosols.
• Nasal secretions are laden with virus during the acute
febrile stages of infection and virus excretion lasts for
approximately 6 days.
• The severity of clinical disease is influenced by many
factors but most importantly by:
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maternal immunity
virus strain
route of inoculation
secondary bacterial infections.
Clinical Signs in Pigs
• Influenza is an acute febrile, respiratory disease
characterised by:
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Fever
Apathy
Anorexia
Laboured breathing
Coughing may be apparent during the later stages of disease
Clinical signs seen less frequently include sneezing, nasal
discharge and conjunctivitis.
Pathological Lesions
• Typical viral pneumonia (interstitial)
• Most often limited to the apical and cardiac lobes of the
lungs, although in severe cases more than half of the lung
may be affected.
• The altered lung areas are depressed and consolidated
and are dark red or purple-red in color, contrasting sharply
with normal tissue.
• The airways are likely to be dilated and filled with bloodtinged, fibrinous exudate.
• The associated bronchial and mediastinal lymph nodes
are usually enlarged.
Histopathological Lesions
• Microscopic lesions usually consist of airways filled with
exudate.
• Widespread alveolar atelectasis, interstitial pneumonia
and emphysema.
• Peribronchial and perivascular cellular infiltration is also
seen.
Avian Influenza Infections in Humans
http://www.mayoclinicproceedings.com/
Public health
(Capua & Alexander, 2005)
H5N1
AI in Human
Courtesy of Dr. Hafez
Thank You