Detection of avian reoviruses causing tenosynovitis in breeder flocks in Iran by reverse transcription-polymerase chain reaction [RT-PCR] and restriction enzyme fragment length polymorphism [RFLP]

Avian reoviruses [ARVs] are members of the Orthoreovirus genus; one of the 12 genera of the Reoviridae family. The ARVs are the cause of some important diseases in poultry such as reovirus-induced arthritis, tenosynovitis, chronic respiratory disease, and mal-absorption syndrome. In this study, the presence of ARVs in the Iranian breeder flocks was investigated through reverse transcriptionpolymerase chain reaction [RT-PCR] and restriction enzyme fragment length polymorphism [RFLP]. A total of 800 fecal swab samples were initially collected from breeder flocks [older than 45 weeks of age]. They were then sent to the laboratory in containers with PBS, and after that they were pooled and finally to 120 samples were obtained. The total RNA extracted from the pooled fecal samples were used to amplify the selected parts of the S1 [1023 bp] and S4 [437 bp] genes from the ARV field isolates using RT-PCR. The positive RT-PCR amplified products were further analyzed by RFLP using five restriction enzymes. Based on the findings, 5 samples were positive with the S1 primer and 6 samples were with the S4 one. The patterns observed after the digestion of PCR products revealed that the isolates of this study were identical to both the S1133 vaccine and standard strains. The findings suggested that the RT-PCR/RFLP analysis might be considered as a simple and rapid approach for the differentiation of ARV isolates. This study was the first molecular detection of the ARVs presence in the Iranian breeder flocks using the RTPCR amplification of the S1 and S4 genes and RFLP analysis

[Virulence determination of Iranian Escherichia coli isolates from poultry in day-old chicks using a lethality test]

Colibacillosis due to Escherichia coli is one of the most important infectious diseases in poultry. While the influence of E. coli virulence factor in birds may differ due to interactions with other influential factors, the sole presence of such factors in E. coli does not determine its pathogenicity. Therefore, it is necessary to test the pathogenic capability of E. coli isolates on susceptible birds. The purpose of this study was to determine the virulence of three E. coli isolates from colibacillosis and compare their effects on day-old chicks using a lethality test. Seventy 1-day-old chicks were divided into 3 treatment groups of 20 chicks and 2 control groups of 5 chicks. Each treatment group was assigned to one E. coli isolate and divided into 4 sub-groups of 5 chicks. The overnight broth culture of each E. coli isolate was washed with PBS three times and diluted. Then, 0.5 ml of undiluted culture [tilde10[9] CFU/mL], and the dilutions of 0.1, 0.01, and 0.001 of each culture were injected subcutaneously to each of the 5 birds in each subgroup behind the neck. One group of 5 birds was injected by PBS while negative control group did not receive anything. The chicks were monitored every 12 hours for 6 days. The dead chicks during the course of the experiment and all survived ones were necropsied and samples were taken from hearts and livers for bacteriological culture. Virulence of each E. coli isolate was evaluated based on a scoring system developed on death time, gross pathological observations, and bacteriological findings. All E. coli isolates of this study were capable of causing mortalities and producing the lesions typical of colibacillosis. There were no significant differences among the three E. coli isolates in their in vivo virulence abilities but the difference between each of the three E. coli isolates and each of the two control groups was significant [p

[Pathogenicity indices of Newcastle disease viruses isolated from Iranian poultry flocks in Iran]

Newcastle disease [ND] is caused by serotype I of avian paramyxoviruses. The ND virus [NDV] strains are conveniently grouped as velogenic, mesogenic, lentogenic, and nonpathogenic-intestinal pathotypes. The purpose of this study was to determine the pathogenicity indices of the isolated NDVs from poultry flocks in Iran. Samples were provided from poultry flocks in different provinces of Iran and prepared for NDV isolation. From many isolated NDVs, 12 isolates belonged to 10 provinces with highly populated poultry farms which were selected for this study. A clone for each of these virus isolates was generated using limiting dilution procedure. Then, the mean death time [MDT], intracerebral pathogenicity index [ICPD, and intravenous pathogenicity index [IVPI] were determined for each virus clone and compared with those of standard virulent strains such as Hertz 33.56 and Texas GB. The results showed that the pathogenicity indices of the NDVs in the present study ranged from 41.6 - 60 hr for MDT, 1.76 - 1.91 for ICPI, and 2.68- 2.88 for IVpI indicate which the velogenic type of our viruses. The findings of this study suggested that the very virulent NDVs currently circulating in Iranian poultry flocks are close to and even more virulent than standard virulent NDVs. Isolation, identification, pathotype determination, and molecular characterization of Iranian NDVs may help authorities to make right decisions to reduce the risks posing the Iranian poultry industry

Isolation, identification, and antimicrobial susceptibility of Clostridium perfringens isolates from acute necrotic enteritis of broiler chickens

The aim of this study was to isolate, identify and determine the antimicrobial susceptibility of Clostridium perfringens [CP] isolates from acute necrotic enteritis of broiler chickens. All broiler carcasses diagnosed as necrotic enteritis [NE] were sampled, subjected to microbial tests and 40 isolates were identified according to standard procedures. The antimicrobial susceptibility of CP isolates to 20 antibacterial agents was then determined. The results show widespread resistance among CP isolates. The most frequent resistance was observed to neomycin sulfate [87.5%], and then to lincomycin and tetracycline [both 80%]. No isolate was resistant to chloramphenicol and the least frequency of resistance was observed to vancomycin [10%], sulfamethoxazole+trimethoprim [17.5%], and penicillin [20%]. All isolates were multiple drug resistant types. There were 39 resistant patterns among the CP isolates, 95% of which were distributed in 38 resistant patterns. These multiple and variable resistance patterns observed among the CP isolates, even among different isolates from one farm, demonstrate a challenge for veterinarians in the field to choose the correct compound to combat the occurrence of NE

[Effect of experimental coccidial infection on cellular immunity induced by newcastle disease vaccination in broilers]

In order to evaluate the possible immunosuppressive effects of coccidial infection on Cell Mediated Immunity [CMI] of broiler chickens, 640 Ross male day old broiler chicks were randomly divided into 4 equal groups of 160 [each consist of 4 replicates of 40]. The negative control group remained unchallenged, while the other three groups challenged with 3 different levels of high, medium and low doses of mixed inoculums of E. acervulina and E. maxima at 15 days of age. For the assessment of CMI, Macrophage Migration Inhibition [MIF] test was performed. For this purpose blood samples were collected at 15, 22, 36 days of age. No significant difference was observed among MIF of different groups at 15 days of age [p>0.05]. At 22 and 36 days of age a significant difference observed among MIF of high dose and control groups [p<0.05]. According to the results, it can be concluded that severe coccidial infection may compromise specific CMI activity in broilers

Experimental induction of necrotic enteritis in broiler chickens by clostridium perfringens isolates from the outbreaks in Iran

To establish an stable challenge system for induction of necrotic enteritis [NE] in broiler chickens, different potential factors and predisposing conditions were imposed in 6 separate different experiments using 525 day-old chicks in total. Despite the presence of some predisposing factors and using 4 isolates of Clostridium perfringens [CP] from acute and severe NE outbreaks as challenge bacteria, the disease was not successfully reproduced in the first 4 experiments. In the 5th and 6th experiments, the predisposing conditions were changed and each bird was challenged with 3 ml [3_10[8] CFU/ml] of CP live culture via oral route and also the feed mixed with CP suspension 2 times per day and for 5 consecutive days. Clinical signs and mortalities, and lesions associated with NE were observed in the later two experiments. This study showed that by stressful nutritional and management procedures such as increased stocking density and high levels of wheat and fish meal; induction of relative immunosuppression; using sufficient CP concentration and appropriate ways of its multiplication; and applying challenge bacteria isolated from acute outbreaks, NE may be experimentally induced in broiler chickens

[Effect of administration of anti-coccidial drugs and vaccines on broiler chicks performance in experimental coccidiosis]

To compare the effect of coccidiostate drugs and coccidial vaccines on the perfrormance of coccidia - infected broiler chicks. Completely randomized design.Nine hundred and sixty day-old Ross 208 broiler chicks. Chicks were randomly assigned to eight treatments. Each treatment contained 3 replicates of 40 chicks. Treatment 1 and 2 [as negeative and positive control] did not receive any coccidiostates or coccidial vaccines. Treatments 3 and 4 fed diets supplemented with Salinomycine and Diclazoril respectively, but did not immunize. Treeatments 5 to 8 immunized with coccidial vaccines [including Livacox Q, Paracox 5, Livacox T, and Iracoc, respectively] by drinking water on 5 days of age. Chicks in treatments 2 to 8 were inoculated with a suspension containing four Eimeria species on 26 days of age. Surveillances for coccidian oocysts of feces samples were carried out from 7 to 13 days of post-challanged. Body weight [BW], body weight gain [BWG], and feed conversion ratio [FCR] were determined weekly. Data for all response variables were subjected to ANOVA. Variable means for treatments showing significant differences in the ANOVA, were compared using the scheffe's test. The results indicated that using coccidial vaccines and coccidiostate drugs decreased oocysts per gram [OPG] of feces significantly [P<0.05]. The highest mean of BW was related to the chicks treated with salinomycine with significant differences in BW among treatments. The lowest FCR was related to non-challanged chicks [negative control].According to the results of this experimental trial, it could be concluded that coccidial vaccines and coccidiostate drugs could decrease the OPG significantly and improve production performance partially, in coccidia-infected broiler chicks