Representative Salmonella serovars isolated from poultry and poultry environments in Saudi Arabia.

The authors describe the source and prevalence of pathogenic Salmonella serovars among poultry farms in Saudi Arabia. A total of 1,052 (4%) Salmonella isolates were recovered from 25,759 samples of poultry (broilers, layers, broiler breeders and layer breeders) and poultry environments (box liner, litter, drag swab, droppings, mice and feed) were examined bacteriologically between 1988 and 1997 at the Poultry Disease Laboratory at the National Agriculture and Water Research Center in Riyadh. Eleven Salmonella serogroups representing 38 different Salmonella serovars were identified by means of antigenic analysis. The majority of the 276 isolates (26.2%) of Salmonella typed, were recovered from liver, heart and intestines of the broilers and layers. The most prominent Salmonella serogroups isolated were as follows: serogroup C1 (392 isolates, 37.26%), B (289 isolates, 27.47%) and D1 (269 isolates, 25.69%). However, untypable and multiple serogroups were also encountered, the most frequent isolates serotyped belonged to groups C1 (97 isolates, 24.7%), D1 (86 isolates, 31.9%), and B (71 isolates, 24.6%). Salmonella Enteritidis (85 isolates, 98.8%), Salmonella Virchow (48 isolates, 57.8%), Salmonella Paratyphi B var. Java (41 isolates, 57.7%) and Salmonella Infantis (30 isolates, 20.6%) were distributed the most widely as all were encountered in poultry and in poultry environments. S. Enteritidis phage type 4 (30 isolates, 35.3%), was the phage type most frequently detected among group D1 phage types, while 39 (45.8%) of the isolates of S. Enteritidis could not be phage typed.

Decontamination of chicken carcasses artificially contaminated with Salmonella.

A study was conducted to evaluate the efficacy of three chemical disinfectants and of ionising radiation in reducing the level of contamination in chicken carcasses which had been artificially contaminated with Salmonella Virchow. Chicken carcasses were obtained from a local abattoir. Five carcasses and one control carcass were used to test each concentration of disinfectant and the radiation. The amount of contaminant employed was 0.5 ml of 10(4) colony-forming units per ml of S. Virchow spread over the thigh, breast and wing areas. All treatments were conducted in duplicate. The three disinfectants used were as follows: calcium hypochlorite, at concentrations of 20 ppm, 50 ppm, 100 ppm and 200 ppm of available chlorine. Lactic acid at concentrations of 0.5%, 0.75% and 1%. Hydrogen peroxide compound at concentrations of 1%, 2% and 3%. Five inoculated carcasses were immersed at a time in one disinfectant concentration for 15 min, while the control carcasses were simultaneously immersed in water free from disinfectants. Five carcasses, each in a plastic bag, were subjected to varying ascending doses (from 2 to 7 k gray [kGy]) of ionising radiation from radioactive isotopes of cobalt 60. A bacteriological examination of each carcass was conducted after the treatment to determine the presence or absence of S. Virchow. The number of carcasses which gave positive results showing the presence of Salmonella decreased after chemical treatment, but the organism was not completely eliminated. However, in those carcasses subjected to 7 kGy of radiation, Salmonella was eliminated and no changes in the appearance, colour or smell of the carcasses were observed.

Use of live and inactivated Salmonella enteritidis phage type 4 vaccines to immunise laying hens against experimental infection.

Four groups of Dekalb Delta commercial layer hens (8 hens per group) were reared individually in cages in an isolation unit. At the age of 8 weeks, groups 1 and 2 were vaccinated with 9R Salmonella gallinarum live (9R live) vaccine. At the age of 18 weeks, group 1 was re-vaccinated with 9R live S. enteritidis vaccine, while groups 2 and 3 were vaccinated with S. enteritidis bacterin. At the age of 22 weeks, groups 2 and 3 were re-vaccinated with S. enteritidis bacterin. Group 4 was not vaccinated and was kept as a control group. At 24, 27 and 30 weeks of age, the four groups were challenged using various concentrations of S. enteritidis phage type 4 and various routes of inoculation. Eggs, cloacal swabs and blood were collected weekly for bacteriological and serological examination. Isolation of the challenge organism from the eggshells and egg contents of the vaccinated groups was significantly lower than with the control group. There was no correlation between humoral antibodies and the shedding of the challenge organism in eggs or cloacal swabs. A combined vaccination programme of 9R live S. enteritidis vaccine and S. enteritidis bacterin provided better protection to laying hens than either vaccine administered alone. Vaccination should never be performed alone but in conjunction with other measures related to veterinary hygiene and good management.

The combined influence of age of embryo and temperature and duration of incubation on the replication and yield of avian infectious bronchitis (IB) virus in the developing chick embryo.

Two experiments were undertaken to investigate the combined influence of the age of embryo at infection and the temperature and duration of incubation on the replication and yield of the Beaudette strain of IB virus lin allantoic fluid and the chorio allantoic membrane. In general a higher titre of virus was found in the allantoic fluid and chorioallantoic membrane of living embryos than of dead ones and with continued incubation of dead embryos the titre of virus fell still further. For embryos of the same age at infection peak titres were similar for those incubated at 32 degrees C and 37 degrees C but were greater than for the corresponding embryos at 42 degrees C. The range of titres for embryos of all ages associated with duration of incubation was narrower for those incubated at 32 degrees C than at 37 degrees C and 42 degrees C and a longer survival period was observed for embryos incubated at 32 degrees C. Peak titres of virus for all age groups were observed after 24 h at 32 degrees C and after 12 h at 37 degrees C and 42 degrees C and then declined. The highest titre for virus in allantoic fluid, in both experiments, was in the 10 d old embryos at 32 degrees C harvested after 24 h. For the chorioallantoic membrane the highest titre in the first experiment was in 12 d old embryos at 32 degrees C, harvested after 24 h, while in the second it was also in 12 d old embryos but at 37 degrees C and harvested after 12 h. The lowest titre of all was in 10 d old embryos incubated at 42 degrees C. It is considered that the maximum total yield of virus from the allantoic fluid and chorio allantoic membrane of the same embryo will be in those infected at 10 - 12 d of age incubated at 32 degrees C to 37 degrees C.

The survival of infectious bronchitis (IB) virus in water.

Observations on the survival of infectious bronchitis virus in 3 mains waters showed that it survived for a much shorter period in one of them which contained a relatively high content of copper (0.2 mg/1). Other factors adversely affecting survival were 5 ppm of free residual chlorine and increase in temperature over the range of 20-35 degrees C. Survival of virus was prolonged in the presence of 0.1% w/v powdered skim milk (PSM), 1,0% w/v poultry mash, 1,0% w/v fresh poultry droppings, rust and 0,01% sodium thiosulphate. In part this protection might have been against the high copper content of the water used but 0.1 % PSM protected also against the combined effect of a temperature of 35 degrees C and 5 pmm chlorine. Factors which seemed to exert relatively little effect on virus survival were the nature of the container, whether of polystyrene, galvanized iron or glass, the pH range of 7-9 and total hardness of the water.