Development of an inactivated whole cell vaccine through immersion for immunoprophylaxis of Francisella orientalis infections in Nile tilapia (Oreochromis niloticus L.) fingerlings and juveniles.

Francisella orientalis infections, known as francisellosis, are one of the most important diseases affecting the production of Nile tilapia, causing high mortality rates in the most susceptible fish stages: fingerlings and juveniles. Antibiotic therapy is the method of choice for treating the disease, as there are no commercially available vaccines. In this study, we developed an inactivated whole-cell vaccine using an isolate of F. orientalis in combination with the aqueous adjuvant Montanide IMS 1312 VG, which was administered to Nile tilapia through immersion. Two immunization trials (1 and 2) were conducted with fish at the fingerling and juvenile stages. For each trial, five different experimental groups were established: a complete vaccine (bacterin in combination with aqueous adjuvant), bacterin, aqueous adjuvant, and positive and negative controls. Thirty days after vaccination, an experimental challenge was performed through intraperitoneal injection of the same F. orientalis isolate. As a result, the vaccinated fingerlings were the only group in which mortality and progression of clinical signs of francisellosis were statistically significantly reduced, although relative percentage of survival (RPS) was low at 50%. In the juvenile group, RPS was higher at 63%, but not statistically significant. Nevertheless, an RPS of only 50% is acceptable for using vaccines in the field. The bacterin and adjuvant treatments alone were not effective, showing an RPS of 37% and 0%, respectively. Post-vaccination mortality was observed in the group exposed only to the adjuvant, which may indicate excessive immune stimulation at this stage. Interestingly, the immune response elicited by the vaccine was unable to eliminate the pathogen from the host; therefore, the surviving animals became carriers. Although the immune response elicited by the vaccine was unable to eliminate the pathogen from the host, this vaccine formulation could be a viable alternative for use in the field and serve as another means of controlling the mortality caused by the pathogen. Our study provides the first report of vaccination, using immersion, against francisellosis at the most susceptible stages of farmed Nile tilapia. Future studies should address the efficiency of immersion vaccines under field conditions.

ACUTE NECROTIZING AND EOSINOPHILIC MYOCARDITIS IN A CHIMPANZEE (PAN TROGLODYTES).

Cardiac disease is of importance in captive chimpanzee (Pan troglodytes) health. Here we report an eosinophilic and necrotizing myocarditis in a 17-y-old chimpanzee with no previous history of cardiac disease that progressed to death within 48 h. Toxic and infectious causes were ruled out. The chimpanzee had eosinophilia at different occasions in previous years. The animal had a severe, diffuse, and acute monophasic necrotizing myocarditis, with a moderate lymphoplasmacytic infiltrate that was rich in eosinophils. Ante- and postmortem investigations are compatible with an unusual eosinophilic myocarditis with clinical evolution and morphology comparable with human eosinophilic myocarditis secondary to hypereosinophilic syndrome.

Genome Sequence of Corynebacterium ulcerans Strain 210932.

In this work, we present the complete genome sequence of Corynebacterium ulcerans strain 210932, isolated from a human. The species is an emergent pathogen that infects a variety of wild and domesticated animals and humans. It is associated with a growing number of cases of a diphtheria-like disease around the world.