Examination of intra-sinus infraorbitalis chicken challenge model of Avibacterium paragallinarum serotype A for vaccine efficacy trials

Infectious Coryza, caused by Avibacterium paragallinarum, is a significant poultry respiratory disease, particularly in the developing countries. It causes marked economic losses by growth retardation and drop in egg production. Vaccination is the most effective preventive measure against IC. The ability of the vaccine to prevent infection is tested in laboratory challenge conditions where the challenge strain, its dose and the challenge route play a crucial role. This study summarizes the establishment of an intra-sinus challenge model of a serotype A strain for vaccine efficacy testing and its testing in a vaccination-challenge efficacy design. In contrast to the literature statements, our results supported the usefulness of the direct intra-sinus challenge method using a high titre of challenge bacteria, which is estimated with high accuracy on the day of challenge using the OD measurement of the culture. This method was successfully applied in an efficacy test with a commercially available combined IC vaccine

Examination of the Virulence of <i>Actinobacillus pleuropneumoniae</i> Serovar 16 in Pigs

Different virulence variants of A. pleuropneumoniae are involved in the etiology of porcine pleuropneumonia. The purpose of the present trial was examination of the virulence of the Actinobacillus pleuropneumoniae A-85/14 strain, the type strain of serovar 16, in an animal challenge experiment. Thirty 12-week-old piglets seronegative for A. pleuropneumoniae were allocated into three trial groups each of 10 animals, and they were infected intranasally with 106, 107, or 108 colony forming units (cfu) of the strain, respectively. Clinical signs were recorded twice a day, and the animals were euthanized 6 days after the infection. Typical clinical signs and postmortem lesions of porcine pleuropneumonia were seen in the animals of each trial group; however, they were generally mild, and no significant differences could be seen between the three groups. Even 106 colony forming units of A. pleuropneumoniae A-85/14 strain could induce clinical signs and lesions. Based on these results, the type strain of serovar 16 of A. pleuropneumoniae must be regarded as a typical pathogenic strain of the species