Influenza A Zoonosis

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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

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NI test
HI test
AGP test
ELISA test
Jong et al., 2000, Journal of Infection
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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."

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http//news.bbc.co.uk/2/hi/americas/8021547.stm
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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.

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Previous Influenza Pandemics

• Spanish flu (1918-1919) H1N1
• Asian flu (1957) H2N2
• Hong Kong flu (1968) H3N2
• Russian flu (1977) H1N1

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http//en.wikipedia.org/wiki/Swine_influenza
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Fields virology, 3rd ed
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(No Transcript)
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Pig Involvement

• A number of findings have suggested a role for
  pigs in the emergence of pandemic influenza
  viruses
• Pigs can be naturally or experimentally infected
  with avian viruses.
• Epithelial cells in pig trachea contain both
  human- and avian-type receptors
• In nature, continued replication of an avian
  virus in pigs leads to variants that
  preferentially recognize human-type receptors
• Swine viruses and avian-human reassortant viruses
  can infect humans and, in some cases, cause fatal
  disease
• 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

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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.

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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)

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Fields virology, 5th ed
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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.

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Done and Brown, 1999
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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.

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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
• maternal immunity
• virus strain
• route of inoculation
• secondary bacterial infections.

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Clinical Signs in Pigs

• Influenza is an acute febrile, respiratory
  disease characterised by
• 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.

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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 blood-tinged, fibrinous exudate.
• The associated bronchial and mediastinal lymph
  nodes are usually enlarged.

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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.

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Avian Influenza Infections in Humans
http//www.mayoclinicproceedings.com/
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Public health
(Capua Alexander, 2005)
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AI in Human
H5N1
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Courtesy of Dr. Hafez
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Thank You