[Evaluation of the timing of the Escherichia coli co-infection on pathogenecity of H9N2 avian influenza virus in broiler chickens]

Bacterial co-infections can probably influence the pathogenicity of H9N2 low pathogenic avian influenza virus [AIV]. This study aimed to evaluate the effect of exposure time to Escherichia coli [O:2] on the pathogenicity of H9N2 AIV in broiler chickens. Three hundred and sixty broiler chickens were randomly allocated to six equal groups. At the age of 26 days, all chicks except groups 5 and 6 were inoculated intra-nasally with H9N2 virus. At the same time, the birds in groups 1 and 5 were infected with E. coli via spray route. Birds in groups 3 and 2 were infected with E. coli three days prior to and three days post AI challenge, respectively. Mortality rates, clinical signs, gross and microscopic lesions, excretion and duration of virus shedding in faecal and tracheal samples and seroconversion to H9N2 virus were assessed in the challenged groups. The highest mortality rate was observed in chickens inoculated with H9N2 followed by E. coli. The most severe clinical signs, gross lesions, mortality rate and virus detection were observed at day 6 post challenge [PC] in birds of group 2, while the duration of virus shedding was longer in group 3 [E. coli followed by H9N2] than other groups. In conclusion, E. coli infection prior to, after or concurrently with H9N2 virus infection could exacerbate the adverse effects of the virus. Our results indicate that E. coli and H9N2 together can mutually exacerbate the condition of either disease in broiler chicks as compared to single infected birds

[Efficacy of thermostable I-2 Newcastle disease vaccine compared to B1 commercial vaccine in broiler chicken]

Frequent vaccination failures have occurred in the broiler farms in Eurasian countries during Newcastle disease outbreaks. The disease is enzootic in many countries of the region, especially in southwest Asia. I-2 vaccine has been used successfully in village chickens in many Asian and African countries. Our preliminary study showed good efficacy of the vaccine in broiler chickens. Therefore the current experimental study was conducted to compare viral shedding period of heat resistance I-2 vaccine with B1 commercial vaccine following challenge with Herts'33. For this purpose three hundred commercial broilers were randomly allocated into four groups; 1] Thermostable I-2 vaccine, 2] Hitchner B1 vaccine, 3] Challenge group with no vaccine, and 4] Negative control group. Experimental chicks were vaccinated on days 19 and 26 by the eye drop route and then the birds were challenged via intra ocular route on day 40 with a suspension containing 10[6] EID[50]/ml challenge virus. Experimental chickens were monitored by collecting buccal and cloacal swabs at different times. Collected swabs were submitted to PCR test. The results showed that vaccination can protect the birds against mortality and also decrease virus shedding; also there was not a significant difference between vaccination with I-2 and B1 vaccines

Effect of Zataria multiflora essential oil on immune responses and faecal virus shedding period in broilers immunized with live Newcastle disease vaccines

Zataria multiflora essential oil possesses immunomodulatory effects and the present study investigates its effect on immune responses to live Newcastle disease [ND] vaccines and faecal shedding period of vaccine strain virus in chickens. One hundred and eighty chickens from both sexes were divided into 6 equal groups: group 1: unvaccinated, group 2: vaccinated [B1 vaccine followed by La Sota 10 days later], group 3: vaccinated + levamisole [150 mg/kg/day, orally], groups 4, 5 and 6 were vaccinated and received Z. multiflora essential oil by SC injections at 0.1, 0.2 and 0.4 g/kg/day dosages, respectively. Levamisole and Z. multiflora essential oil were administered for 10 and 5 consecutive days post B1 vaccination. On days 0, 7, 14, 28 and 35 post booster vaccination [PBV], HI test was performed. Delayed type hypersensitivity [DTH] test was accomplished on day 14 PBV. Faecal virus shedding was determined during 15 days PBV with 3 day intervals by RT-PCR method. Zataria multiflora essential oil induced a dose-dependent increase in antibody titers in an extent higher than levamisole as well as a dose-dependent suppression of DTH reaction. Effect of Z. multiflora essential oil at the dosage of 0.1 g/kg on shortening of faecal virus shedding period was exactly the same as levamisole where higher doses demonstrated stronger decrease. In conclusion, Z. multiflora essential oil stimulates humoral immune responses and shortens faecal virus shedding period while suppressing cell-mediated immune responses in chickens vaccinated with live ND vaccines

Evaluation of H9N2 avian influenza virus dissemination in various organs of experimentally infected broiler chickens using RT-PCR

Widespread occurrence of H9N2 low pathogenic avian influenza [LPAI] viruses in many Asian countries during the past decade has resulted in the need for evaluation of the pathogenesis of H9N2 virus infection. In this study, tissue tropism and dissemination of A/Chicken/Iran/772/1998[H9N2] virus throughout the body of broiler chickens were investigated. The clinical signs, gross lesions and antibody titer of the infected chicks were also monitored. Fifty one-day-old commercial broiler chicks were divided randomly into two groups [forty chicks in the experimental and ten chicks in the control group]. At the age of five weeks the chicks in the experimental group were inoculated intranasally with the virus. The samples from various tissues were collected at 1, 3, 6 and 9 days post-inoculation [DPI]. We used reverse transcriptase/polymerase chain reaction [RT-PCR] assay to evaluate the virus dissemination. Chickens exhibited mild respiratory signs, depression and 5% mortality. Viral RNA was detected in the kidneys on days 3, 6 and 9 P1. The virus was also found in the spleen, trachea and lungs on days 3 and 6 P1. Viral RNA was observed only on day 6 P1 in feces. The most remarkable clinical signs and virus detection appeared on day 6 P1. Overall, out of 22 samples taken from each organ of the experimental [dead plus euthanized] birds, 4, 5, 11, 4, and 5 samples from trachea, lungs, kidneys, spleen and feces showed viral RNA, respectively. We could not trace the virus in the blood and pancreas. Data indicated that the number of infected chickens and viral RNA detection from tissues was reduced with increasing antibody titer on day 9 P1. Our findings suggest that the virus has tissue tropism for respiratory, urinary, lymphoid and digestive systems