A quantitative measurement of the effect of avian influenza virus on the ability of turkeys to eliminate Pasteurella multocida from the respiratory tract

C-reactive protein, haptoglobin, serum amyloid A and pig major acute phase protein response in pigs simultaneously infected with H1N1 swine influenza virus and Pasteurella multocida

Background

Swine influenza (SI) is an acute respiratory disease caused by swine influenza virus (SIV). Swine influenza is generally characterized by acute onset of fever and respiratory symptoms. The most frequent complications of influenza are secondary bacterial pneumonia. The objective of this work was to study the acute phase proteins (APP) responses after coinfection of piglets with H1N1 swine influenza virus (SwH1N1) and Pasteurella multocida (Pm) in order to identify whether the individual APP response correlate with disease severity and whether APP could be used as markers of the health status of coinfected pigs.

Results

In all coinfected pigs clinical sings, including fever, coughing and dyspnea, were seen. Viral shedding was observed from 2 to 7 dpi. The mean level of antibodies against Pm dermonecrotoxin in infected piglets increase significantly from 7 dpi. Anti-SwH1N1 antibodies in the serum were detected from 7 dpi. The concentration of C-reactive protein (CRP) increased significantly at 1 dpi as compared to control pigs, and remained significantly higher to 3 dpi. Level of serum amyloid A (SAA) was significantly higher from 2 to 3 dpi. Haptoglobin (Hp) was significantly elevated from 3 dpi to the end of study, while pig major acute phase protein (Pig-MAP) from 3 to 7 dpi. The concentrations of CRP, Hp and SAA significantly increased before specific antibodies were detected. Positive correlations were found between serum concentration of Hp and SAA and lung scores, and between clinical score and concentrations of Pig-MAP and SAA.

Conclusions

The results of current study confirmed that monitoring of APP may revealed ongoing infection, and in this way may be useful in selecting clinically healthy pigs (i.e. before integration into an uninfected herd). Present results corroborated our previous findings that SAA could be a potentially useful indicator in experimental infection studies (e.g. vaccine efficiency investigations) or as a marker for disease severity, because of correlation observed between its concentration in serum and disease severity (lung scores, clinical scores).

Nonspecific cellular defense of the avian respiratory system: a review

The normal, steady-state, avian respiratory system has very low numbers of residing avian respiratory phagocytes (ARP). Birds must rely heavily on the influx of ARP to defend against infectious agents. The system is refractory to elicitation by inert stimulants, but responds efficiently to replicating bacteria, with very rapid influx of large numbers of activated ARP (polymorphonuclear neutrophils, heterophils, and macrophages) with increased phagocytic proportions and capacities. The numbers subside within a few a days. Activated ARP act in a non agent-specific manner: Pasteurella multocida-activated ARP can defend against a severe Escherichia coli airsacculitis. Parenteral routes of stimulation generally are not, respiratory routes are very, efficient in activating ARP. Heterophils are the most efficient in defensive reactions, such as oxidative burst, production of nitric oxide and killing of bacteria. Respiratory viruses may stimulate, but also may diminish some of the defensive functions of ARP. This is also true for attenuated, modified live virus vaccines. These vaccines must be used carefully in the presence of subclinical bacterial, mycoplasmal infections. Published literature on non-specific cellular defense of the avian respiratory system is very limited, particularly about interactions among multiple infectious agents and the system.

Environment-immune interactions

The need for effective immune function for the maintenance of health has been clearly established in both agriculturally significant animal species and humans. Intensive agricultural practices present production species with numerous disease challenges during the rearing period. Environmental factors represent a ubiquitous, yet frequently manageable, category of immunomodulators that can influence immune performance and ultimately disease susceptibility or resistance. However, strategies for assessing overall immune potential have not been widely implemented for agricultural species. This is in contrast to the use of immune evaluation for human health considerations. Immune assessment relative to environmental-immune interactions can produce benefits in two areas. First, the efficiency of the production operation can be enhanced. Second, the welfare of the animals during the production cycle can be optimized. This paper presents an overview of environmental factors known to influence the immune function of poultry and the opportunities to manage environmental factors to benefit the health of the animals. In addition, the paper discusses the status of immunological assessment for humans and laboratory animals and proposes potential immune assessment panels that could serve as a tool to optimize the environmental management of poultry populations.