Relation Of Ta To Tm Of Primers

UPDATE ON SWINE INFLUENZA

Summary
The swine flu caused by influenza A virus belonging to the family Orthomyxoviridae

. Influenza virus subtypes most frequently reported in pigs worldwide are H1N1, H1N2 and H3N2. In Spain, recent studies have revealed a wide dissemination of these subtypes in the pig, and a considerable percentage of animals with antibodies to different subtypes simultaneously. Clinical symptoms caused by influenza virus in

pig includes fever, lethargy, anorexia, weight loss and cough, among other signs. Traditionally, it has been reported that the entry of a new virus on a farm causes the appearance of the characteristic signs of the disease
in animals of all ages. However, new research
point to a condition that often progresses with subclinical.
control and prevention of disease relapse in establishing appropriate biosecurity measures and the use of vaccine strategies.

Keywords: influenza, pork, prevention, diagnosis
Summary

Swine Swine influenza update is Caused by influenza type A influenza virus from the Orthomyxoviridae
family. H1N1, H1N2 and H3N2 are the swine influenza virus subtypes
most frequently reported worldwide in pigs. In Spain, recent studies show a widespread dissemination of these subtypes in pig population, and a considerable proportion of animals presenting antibodies against different subtypes simultaneously.
Clinical signs caused by influenza virus in pigs include fever, lethargy, anorexia, weight loss and cough, among others. Traditionally, it has been reported that the introduction of a new virus on a farm would cause clinical disease in animals of all ages. However, new studies point to the spread of the infection in farms without clinical signs
Control and prevention of disease fall on the establishment of appropriate Measures biosecurity and the use of Vaccination strategies.

Key words: influenza, pig, prevention, diagnosis Meritxell Grifé1 Simon, Gerard E. Martin Valls2 and Jordi Casal i Fàbrega3

Contact the authors: 1 degree in veterinary medicine at the Autonomous University of Barcelona - Centre for Research in the Animal Health (CRES), UAB-IRTA, Campus de la Universitat Autònoma de Barcelona, \u200b\u200b08193 Bellaterra ( Barcelona, \u200b\u200bSpain) - Tel: 935 814 527 - Fax: 935 814 490 - email: @ cresa.uab.cat meritxell.simon
2 Ph.D. in veterinary medicine at the Autonomous University of Barcelona - Centre for Research in the Animal Health (CReSA) , UAB-IRTA, Campus de la Universitat Autònoma de Barcelona, \u200b\u200b08193 Bellaterra (Barcelona, \u200b\u200bSpain) - Tel: 935 814 561 - Fax: 935 814 490 - email: @ cresa.uab.cat gerard.martin
3 Ph.D. in veterinary medicine at the Autonomous University of Barcelona - Department of the Animal Health / Centre Research in the Animal Health (CReSA) - Campus of the Universitat Autònoma de Barcelona, \u200b\u200b08193 Bellaterra (Barcelona, \u200b\u200bSpain) - Tel: 935 811 047 - Fax: 935 812 006 - email: @ uab.cat
jordi.casal
Influenza or swine flu is an infection caused by Orthomixovirus that affects a variety of species which include humans, pigs, horses and birds. In mammals clinical course abruptly with fever and respiratory signs. In recent
time the flu has been topical in the first place because
to the emergence of highly pathogenic avian influenza H5N1 in Southeast Asia and later spread to Europe via wild birds in 2006. More recently, in April 2009, set off alarms in Mexico with the emergence of a new variant of H1N1 and its subsequent spread to the rest of the world. The name swine flu which initially gave this latest outbreak has served to increase interest in the flu in this species and to verify that there really is a significant lack of some aspects of the infection in pigs. In this article we briefly review existing knowledge about the infection in pigs. ETIOLOGY


The Swine Flu is a disease caused by the genus Influenza virus type A belonging to the family Orthomyxoviridae (Figure 1). Influenza viruses are divided into subtypes depending on the two surface glycoproteins: hemagglutinin (HA) and neuraminidase (NA). The HA is directly involved in the infection process since it allows the virus to bind to receptors on the cell membrane and colonize the cell (Murphy et al., 1999). On the other hand, the NA allows the release of virions and thus facilitates virus
exit the cell and its spread to other uninfected cells (Murphy et al., 1999). In total we have described 16 types of hemagglutinin (H1-H16) and 9 neuraminidase (N1-N9).
The genome of Influenza type A is broken into eight segments of ribonucleic acid (RNA), a feature that makes possible
genetic recombination between different viruses that are infecting the same cell simultaneously. On the other hand, RNA viruses are under strong genetic drift due to the high error rate of RNA polymerase.
The influenza virus originated in birds. However, some types can affect mammals, especially humans, pigs, horses and lions.
The respiratory tract of pigs has receptors for influenza virus typically
both avian (a-2, 6) and mammals (a-2, 3). For this reason, the swine was considered an array for the generation of novel influenza viruses from genetic recombination of the virus from birds and mammals. A recent example we have with the H1N1 pandemic virus, which incorporates human genes, poultry and pigs and, although this strain affects human species, its origin could be closely related to swine (Smith et al., 2009) . EPIDEMIOLOGY


The main route of entry of swine influenza virus in a farm is the introduction of infected animals, but also have described other pathways such as aerosols, fomites, and even the movement of personnel or material contaminated clothing (Alexander, 2007). Once inside the farm, the virus is transmitted primarily by direct contact between farm animals for as long as susceptible individuals (Olsen et al., 2006).
As discussed in the previous section, subtypes H1N1, H1N2 and H3N2 swine influenza are most common. Have also isolated other subtypes of influenza virus, although less frequently, and have not become established extensively in the pig population. These include: the subtypes H1N7, H4N6, H3N3 and H3N1 (Brown et al., 1994; Karasin and Olsen 2000; Karasin et al., 2004; Lekcharoensuk et al., 2006).
In Spain, H1N1 and H3N2 subtypes were identified for the first time
middle of the decade of the 80 (Plana Duran et al., 1984, Castro et al., 1988). As regards the H1N2 subtype was first isolated in samples taken in 2003 (Maldonado et al., 2006). Recent studies have revealed a wide spread of swine influenza subtypes prevalent in pigs in English pig. (Maldonado et al., 2006; Fraile et al., 2010; Simon-Grifé et al., 2010a). The latter work, carried out in 100 pig farms were obtained at random from farms throughout the English territory, found antibodies to H1N1, H1N2 and H3N2 in 91%, 50% and 82% of farms
respectively. In 79% of the farms and in 20% of animals tested
antibodies were detected two or more subtypes. PATHOGENESIS AND CLINICAL


Infection with swine influenza virus is limited to the respiratory tract but also described a case in the extrarespiratoria (Kawayoka et al., 1987). The virus replicates in cells of the nasal mucosa, tonsils, trachea, lung and tracheobronchial limfonodos (Brown et al., 1993, Heinen et al., 2000).
The incubation period of the disease is 1-3 days (Olsen et al., 2006;
Kahn and Line, 2006). Usually the virus excretion can begin 24 hours after infection and in most cases continued until 7-10 days later
(Olsen et al., 2006, OIE, 2008), although viral shedding has been reported durations
over four months, these cases are rare
(Blasckovic et al., 2000).
antibodies against swine influenza virus are detectable in serum
from seven days postinfection (PI), although the optimal time
detection is at 2-3 weeks PI, when the peak occurs in titles
antibodies (Larsen et al., 2000).
Clinical symptoms caused by influenza A virus in pigs is very similar to that produced
in humans. Among the most common clinical signs can
noted fever, lethargy, anorexia, weight loss and cough (Van Reeth, 2007;
OIE, 2008). It also may be other signs such as conjunctivitis, nasal secretions and abortions (Heinen, 2003, OIE, 2008). Traditionally,
described the entry of a new influenza virus on a farm produces
the typical clinical picture of the disease in a high percentage of animals
(Olsen, 2006). However, recent studies have shown that infection of a complete set of animals need not be accompanied by clinical signs
(Simon-Grifé et al., 2010b).
morbidity in a holding up to 100%, but the mortality rate is very low
(
Gross lesions observed in animals with swine influenza correspond to a bronchiole-interstitial pneumonia and are usually confined to the lobes apical or heart disease, although experimental infections have been reported lesions covering more than 50% of the lung (Richt et al., 2003).


DIAGNOSTIC METHODS The diagnosis of swine influenza can be achieved by virus isolation, detection <1%). Generalmente, la recuperación es rápida y comienza entre los 5 y 7días después de la aparición de los signos clínicos (Heinen, 2003; Olsen et al., 2006). Las infecciones bacterianas secundarias o las coinfecciones con otros virus pueden incrementar la gravedad de la enfermedad (Heinen, 2003; OIE, 2008).
nucleic acid and antibody detection techniques. Viral isolation


different ways to isolate the influenza virus. The methodology used is traditionally
isolation in embryonated chicken eggs (OIE, 2008). However, working with chicken eggs is long, tedious and requires some practice for inoculation. It is also necessary to put the embryo. For these reasons we have developed different
cell lines can be infected with influenza virus, such as cell line Madin-Darby Canine Kidney
(MDCK), which is the most commonly used. The virus will become evident when observing cytopathic effect therein. The use of embryonated eggs and MDCK allow the isolation, production and virus titration, and can provide some information about the behavior of the infective strain. Both are procedures for further study in more detail the behavior and origin of the virus.


amplification of genetic material present in the generic detection techniques are of type A viruses and also
techniques to the characterization and determination of subtype of Influenza A.

generic methods are currently used techniques chain reaction polymerase transcription (RT-PCR) in real time (Figure 3) for the generic detection of Influenza type A (Spackman et al.
2008, Slomka et al., 2010). These techniques are based on the detection of the matrix gene (M), a highly conserved region of influenza virus A (Spackman et al., 2008), so as to detect and quantify virtually all influenza viruses type A, but not useful to characterize / subtype strains.
Complementary to other RT-PCR (conventional and real-time) are able
to amplify the hemagglutinin and neuraminidase pig (H1, H3, N1 and N2). Using these techniques can be determined directly subtype if it is a typical swine strain (Young et al., 2002; Chiapponi
et al., 2003; Richt et al., 2004; Lee, 2008; Mallinga et al., 2010). The high rate of mutations that have the influenza virus requires periodic renewal of the techniques of nucleic acid detection, adapting to the new virus originated. Detection of antibodies


These techniques are appropriate for analyzing post-seroconversion viral infections either clinical or subclinical, or also after a vaccination.
technique for the detection of antibodies is hemagglutination inhibition (IHA) (OIE, 2008). This technique is capable, a priori, to distinguish between antibodies
different viral subtypes and even different sampling


To make a proper diagnosis is very important that the sample is appropriate. In summary, then specified for each technique the sample type, time of blood sampling, animals should be sampled and the purpose for which it is made.
Characteristics of the samples of choice for every laboratory diagnostic technique
Technical
Sample Type
Optimal timing of sampling

Purpose conventional RT-PCR and real-time nasal swab
Lung

1 to 7 days from the onset
clinical signs
Detection and quantification ■ ■ ■ ■
viral subtyping and sequencing of the strain
Isolation in embryonated eggs or MDCK
Isolated viral titration and production for use
back
ELISA Serum IHA

From 2-3 weeks post-infection

■ ■ Confirmation of influenza virus circulation
■ ■ Assess vaccine efficacy
■ ■ Determine / the subtype / s current / s ( IHA only)

Recently, studies by Kyriakis et al. (2010) have shown that consecutive infections or vaccinations against one or more subtypes in a single animal makes it generates, in low titer antibodies against influenza subtypes that have not been previously exposed. These data suggest a rethinking of interpretation strains belonging to the same subtype (Van Reeth et al., 2006, Kyriakis et al., 2010). The sensitivity of this technique is dictated by the strains used as antigen. In this sense, is recommended for the IHA strains isolated homologous to the region from which sera were obtained to be analyzed. low titers obtained by IHA in field samples, and it could be false positive.
also now sell kits of ELISA can detect antibodies
against any influenza A virus (Idvet, Idexx, Hipra). It is quick and simple test application based on the detection of specific antibodies of the nucleocapsid (NP) and the M protein, which are proteins highly conserved in all influenza virus A.
technique IHA and ELISA kits are complementary, since a negative result to the IHA, which in turn is positive for ELISA, suggesting the circulation of a strain or subtype different from those used as antigen for the IHA. However, the sensitivity of the ELISA market is lower than the IHA when we refer to a particular subtype. PREVENTION AND CONTROL


Prevention of swine influenza is based on two pillars, biosecurity measures and vaccination strategies. Biosecurity measures


Biosecurity measures are appropriate to prevent and control the entry and spread of influenza virus on a farm.
The arrival of infected animals has been postulated as a common way of introducing influenza virus in a pig (Alexander et al., 2007; Simon-Grifé et al., 2010a). For this reason, the implementation of a quarantine period in animals is a newly introduced effective measure to reduce the risk of infection from the farm.
bird access to the farm or other materials, such as feed or water should be avoided because the birds have been described as a potential source
introduction of influenza virus (Pensaert et al., 1981).
People who have contact with farm animals can act as sources for the introduction of human viruses


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