Ulcerative dermatitis in barramundi due to coinfection with Streptococcus iniae and Shewanella algae.

Streptococcus iniae is a pathogenic bacterium which causes septicaemia, while Shewanella algae is an opportunistic pathogen found in marine environments. In this study, we investigated an uncommon coinfection of these 2 bacterial species which resulted in systemic disease and cutaneous ulcers in a barramundi Lates calcarifer farm in the Persian Gulf, Iran. Culture, molecular and histopathological specimens were taken from different organs. In histopathology, results indicated deep bacterial ulceration of skin and subcutaneous muscles. Haemorrhage and hyperaemia were the most common signs observed in visceral organs. In culture, Gram-positive cocci were grown from visceral organs while Gram-negative bacilli were isolated from ulcers. In molecular examination, Streptococcus iniae and Shewanella algae were identified from visceral and ulcer samples, respectively, by PCR of the 16S rRNA gene. The disk diffusion method was used to determine antimicrobial susceptibility of isolated bacteria, with Shewanella algae being resistant to most routinely used antibiotics. In this study, a mixed infection of 2 bacterial species was found; we conclude that systemic streptococcosis could act as a predisposing factor for Shewanella penetration into skin and subsequent ulcer formation. Coinfections are very common in mammals; however, this subject has received little attention in other species, such as fish, and particularly in aquaculture. This study highlights the potential significance of coinfections in barramundi, the effect on the severity of the disease and the potential for new opportunistic pathogens arising.

Evaluation of inactivated vaccine of the variant 2 (IS-1494 /GI-23) genotype of avian infectious bronchitis.

The infectious bronchitis virus (IBV) is the cause of avian infectious bronchitis (IB). IB is one of the most highly contagious diseases, which results in many economic losses in the poultry industry worldwide. The nature of this virus is such that it generates new genotypes continuously. Proper vaccination is the most suitable way of combatting IB. One of the novel genotypes of IBV, which has been circulating in the Middle Eastern countries, is the variant 2 (IS-1494/GI-23) genotype. This study aims to design and produce an autogenous variant 2 vaccines. After isolation and characterization of the Iranian variant 2, the inactivated vaccine was formulated according to the OIE guidelines, and its different aspects (Purity, titration, inactivation, immunization) were evaluated. The designed vaccine passed all of OIE quality control standards. In the assessment process, the protection rate in the groups receiving the variant 2 and commercial vaccines was 67 % and 60 %, respectively. Although the differences were not significant, they indicated better protection, and the viral load in the feces and the kidney of the group receiving the variant 2 vaccine was lower than that in the commercial vaccine. It is suggested that the variant2 strain should be added as one of the local strains to the commercial inactivated vaccines in areas affected by this genotype. The use of this vaccine in layer and breeder flocks can help to protect them against variant 2 during the production phase. Also, the transfer of maternal antibodies to offspring can provide strain-specific immunity for one-day-old chickens.