ABSTRACT:Cattle Egrets have a worldwide distribution, feed in proximity to cattle and other domestic animals, and often nest in large colonies in urban woodlots. Over a 3-yr period, nestlings from five Cattle Egret colonies from Central Texas, USA, were surveyed for salmonellosis. Prevalence of infection ranged from 29% to 95%. Seventeen Salmonella enterica subsp. enterica serotypes were isolated, of which the 4,5,12:i-monophasic serotype predominated in cultures of both the digestive tract and pooled spleen and liver. Of 11 4,5,12:i-monophasic isolates phage typed, eight were determinate type 193. The 4,5,12:i-monophasic isolates were susceptible to all antibiotics tested and were highly invasive in the day-old chick infection model. Microscopic lesions were found in the livers of Cattle Egrets with systemic infections with the 4,5,12:imonophasic serotype, suggesting that infections with this serotype may often be fatal. Twenty-nine serotypes were identified in 179 S. enterica subsp. enterica isolates from horses admitted to the Texas A&M University Veterinary Teaching Hospital in 2 yr following the Cattle Egret study. The 4,5,12:i-monophasic serotype was not isolated from horses, but 12 serotypes were isolated from both horses and Cattle Egrets. The temporal distribution of the horse cases suggested that Cattle Egrets and horses may be exposed to similar sources of Salmonella, but provided no evidence of transmission between these two species. Similar conclusions were drawn when Cattle Egret isolates were compared to isolates from feedlot and dairy cattle from Texas and surrounding states. Given that the Cattle Egret 4,5,12:i-monophasic serotype was highly invasive and other isolates of this serotype have been associated with food poisoning, it is likely that Cattle Egret colonies pose a health risk to humans living near them.

Streptococcus iniae (junior synonym S. shiloi) isolated from tilapia and trout in Israel and in the United States were subtyped by restriction length polymorphism (RFLP) based on PCR amplified 16S rDNA and by ribotyping. 16S rDNA RFLP discriminated between S. iniae and other fish pathogens but not between S. iniae strains. HindIII and EcoRI ribotypes of S. iniae discriminated American from Israeli strains rejecting the possibility of an epidemiological link between S. iniae infections in the two countries. Israeli strains isolated from tilapia and trout could not be completely differentiated. The S. iniae ATCC 29178T (T = Type strain) strain, isolated from a freshwater dolphin belonged to a ribotype different from those of all the fish isolates.

Five groups of Tswana-cross castrated male cattle between 20 and 30 months of age (a total of 158 animals) were transported from a ranch in a heartwater-free area of south Botswana to a feedlot near Gaborone in the east of Botswana where heartwater is endemic. On arrival, one group was vaccinated intravenously with the Onderstepoort sheep blood heartwater vaccine, one group was vaccinated intravenously with the new Onderstepoort tick-derived heartwater vaccine and a third group was vaccinated subcutaneously with this tick-derived vaccine. Vaccine reactions were blocked with long acting oxytetracycline on the first day of fever. A fourth group had a series of injections of long acting oxytetracycline on days 0, 7, 14 and 21 after arrival, and a fifth served as untreated controls. The animals remained at the feedlot for 65 days during which time they faced a low level of challenge by Amblyomma hebraeum ticks. None contracted heartwater and so they were then challenged, together with a further group of control cattle, with a dose of the sheep blood vaccine. Some animals in all groups had severe heartwater reactions and died despite therapy, but 76.7 per cent, 64.5 per cent and 74.3 per cent of the cattle in the blood vaccine, intravenous tick vaccine and long acting oxytetracycline groups respectively were resistant to challenge, compared with 48.3 per cent of the subcutaneous tick vaccine group and 36.4 per cent of the controls. It was concluded that intravenous vaccination of susceptible adult cattle with either the blood or the tick-derived vaccine needs careful monitoring in the month after vaccination and does not necessarily result in immune animals.(ABSTRACT TRUNCATED AT 250 WORDS)