Ulf Polster

Porcine reproductive and respiratory syndrome virus (PRRSV): kinetics of infection in lymphatic organs and lung.

Summary Pigs were infected by the oronasal route with European isolates of the porcine reproductive and respiratory syndrome virus (PRRSV; I10 and Cobbelsdorf). The kinetics of infection in lymphatic organs and the lung were analysed by immunofluorescence detection of virus antigen, re‐isolation of the virus and reverse transcription‐polymerase chain reaction (RT‐PCR) for PRRSV‐specific RNA. The kinetics of PRRSV infection proceeded in three phases, irrespective of the varying infestation of lymphatic organs within the first days post‐infection (p.i.). First, an early acute infection of lymphatic organs developed within the first week and was characterized by a high number of antigen‐positive macrophages. Second, a delayed acute infection of the lung was observed, which was most pronounced during the second and third week p.i. when a high number of infected alveolar macrophages was observed. The acute infection of lymphatic organs had resolved at this time. Infected cells in the lung were predominantly located in pneumonic lesions. Third, a persistent infection was demonstrated by RT‐PCR and immunohistology when the experiments were terminated at day 49 p.i. The virus persisted in lymphatic organs, especially in the tonsils, and in the lung. At this stage, indications for a re‐occurrence of acute infection were observed in restricted areas of the lung.

Mucosal immunization with live recombinant bovine respiratory syncytial virus (BRSV) and recombinant BRSV lacking the envelope glycoprotein G protects against challenge with wild-type BRSV.

ABSTRACT Recombinant bovine respiratory syncytial virus (rBRSV) and an rBRSV deletion mutant lacking the G gene (rBRSVΔG) were characterized in calves with respect to replication competence, attenuation, and protective efficacy as live-attenuated BRSV vaccines. Both recombinant viruses were safe and induced protection against a BRSV challenge infection. rBRSV replicated efficiently in the upper respiratory tract. Intranasal immunization with rBRSVΔG led to infection but not to mucosal virus replication. Neutralizing antibodies were induced by rBRSV and rBRSVΔG. Thus, the BRSV attachment glycoprotein G seems to be dispensable in vaccinating calves against BRSV.

Recombinant virus-expressed bovine cytokines do not improve efficacy of a bovine herpesvirus 1 marker vaccine strain

Cytokines play a key role as regulators of the immune response. To elucidate whether the efficacy of a live virus vaccine can be improved by co-expression of cytokines, expression cassettes for bovine interleukins (boIL)-2, -4, -6, and -12 and bovine interferon-gamma (boIFN-gamma) were integrated into the glycoprotein E (gE)-locus of the bovine herpesvirus 1 (BHV-1) vaccine virus strain GK/D. Cell culture analyses demonstrated that expression of the cytokines did not impair the replication of the recombinant viruses. To test safety and efficacy, groups of 4-6 months old BHV-1 seronegative calves were vaccinated intranasally with the parental virus strain GK/D or the recombinants, and challenged intranasally 3 weeks later with virulent BHV-1. The animals were monitored for clinical signs, virus excretion and antibody status after vaccination and challenge. All vaccines were well tolerated and protected the immunised calves from clinical disease following challenge, and reduced duration and titres of challenge virus shedding. Calves inoculated with the boIL-6, boIL-12 and boIFN-gamma expressing recombinants showed a significant reduction in vaccine virus shedding but secreted more challenge virus than the other vaccinees. These findings indicate that expression of these cytokines mediates a better control of the vaccine virus replication which, however, interferes with the immunogenicity of the vaccine. In summary, all recombinant viruses were safe and effective, but protection afforded by the recombinants was not improved as compared to vaccination with the parental virus strain GK/D.

Granulomatous inflammation of salt glands in ducklings (Anas platyrhynchos) associated with intralesional Gram-negative bacteria.

The “nasal glands” occur in many bird species and are powerful sodium ion-excretory organs. In ducks, they are located in supraorbital bony recesses. Granulomatous inflammation of these glands occurs with an incidence of approximately 1% in ducklings (Anas platyrhynchos), and is not associated with specific clinical symptoms. We investigated nine glands of eight animals with granulomas by gross pathology and histopathology, and compared results of bacteriology with 20 non-lesioned nasal glands. Adenitis was characterized by multifocal to coalescent heterophilic granulomas with central necrotic heterophils, and multinucleate giant cells, lymphocytes and plasma cells. Within the centres of the granulomas, there were clusters of Gram-negative bacteria that were identified as halotolerant Pseudomonas aeruginosa, Proteus mirabilis and Aeromonas hydrophila. Normal glands contained exclusively various halotolerant Gram-positive bacteria, mostly Streptococcus sp. and Enterococcus sp. The distribution of lesions and lack of clinical symptoms were suggestive of a localized ascending infection via the secretory ductules.

Mesenteric Lymphangitis and Sepsis Due to RTX Toxin-Producing Actinobacillus spp in 2 Foals With Hypothyroidism–Dysmaturity Syndrome

Actinobacillus suis–like organisms (ASLOs) have been isolated from the genital, respiratory, and digestive tracts of healthy adult horses, horses with respiratory disease, and septic foals. Two foals with congenital hypothyroidism–dysmaturity syndrome from separate farms developed ASLO infection. At necropsy, both had contracted carpal flexor tendons, thyroid hyperplasia, and thrombotic and necrotizing mesenteric lymphangitis and lymphadenitis; one foal also had mandibular prognathism. Numerous ASLOs were isolated from tissues from both foals, including intestine. Biochemical testing and mass spectrometric analysis of the two Actinobacillus isolates did not allow unequivocal identification. Comparative genetic analysis was done on these and similar isolates, including phylogeny based on 16S rRNA, rpoB and recN genes, as well as RTX (repeat in toxin) toxin typing of apxIA–apxIVA and aqxA genes. One isolate was identified as Actinobacillus suis sensu stricto, based on the presence of apxIA and apxIIA but not aqxA, whereas the other isolate had aqxA but neither apxIA nor apxIIA, consistent with A equuli ssp haemolyticus. Based on genotypic analysis of the isolates included for comparison, 3 of 3 equine ASLOs and 2 of 5 A equuli isolates were reclassified as A equuli subsp haemolyticus, emphasizing the importance of toxin genotyping in accurate classification of actinobacilli.

Systemic listeriosis in caged canaries (Serinus canarius)

The occurrence of listeriosis in 12 caged canaries is described where 50% of the birds, including the female and all of the offspring, died within 2 weeks without clinical signs. At necropsy, multifocal necrotizing and partly granulomatous hepatitis, splenitis, myocarditis, interstitial nephritis, and exudative pericarditis with intra-lesional Listeria monocytogenes were the predominant findings as shown by histopathology and immunohistochemistry. Microbiology, serology and polymerase chain reaction revealed L. monocytogenes serotype 1/2a as the causative agent. Thus listeriosis has to be considered in the differential diagnosis for granulomas associated with mycobacteriosis, yersiniosis, coligranulomatosis or fungal infections.