Iranian Journal of Veterinary Research
Volume:10 Issue: 1, Winter 2009

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 PI. The virus was also found in the spleen, trachea and lungs on days 3 and 6 PI. Viral RNA was observed only on day 6 PI in feces. The most remarkable clinical signs and virus detection appeared on day 6 PI. 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 PI. Our findings suggest that the virus has tissue tropism for respiratory, urinary, lymphoid and digestive systems.

Avian adenovirus was isolated from naturally infected birds during 1990 to 2003 in the vicinity of Karachi, Pakistan. The virus is known to cause hydro-pericardium syndrome (HPS) in poultry. The mortality was recorded 20-50% in commercial broilers. Fifty field samples were collected; however, six samples were selected for molecular studies. These isolates were grown and characterized by cell culture using chicken embryo liver cell culture, chicken embryo pathogenicity, agar gel precipitation (AGP), serum neutralization test, DNA extraction, polymerase chain reaction (PCR) and restriction enzyme analysis (REA). Reference strain J2-A (ATCC VR-829) was used to confirm that HPS isolates belongs to avian adenovirus type-4. The disease was reproduced in 28-day-old broilers by intramuscular inoculation of cell extracts. Typical hydro-pericardium was observed in experimental chickens 72 h post-inoculation. The 50% neutralization endpoint of pooled sera of these isolates was not recorded more than 1:40. The results showed that there was no difference in PCR product of 1319 bp with H3/H4 primer on agarose gels, which is characteristic of group 1 avian adenovirus (AA). Restriction fragment length polymorphism (RFLP) analysis of PCR products using restriction enzyme Hpa II resulted in five bands confirming the presence of AA in the analyzed samples.

In the present study, we reported infection with eighteen species of the genus Dactylogyrus, belong to the family Dactylogyridae from five breeder fish species, including common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), big head carp (Hypophthalmichthys nobilis) and black carp (Myelopharyngodon piceus) which introduced and imported to Iranian freshwaters from Russia, Romania, Hungary and China over the last 40 years. The infection was also found in Carassius auratus gibelio, it is not known when this fish species was introduced into the country. The Dactylogyrus spp. were as follows: Dactylogyrus achmerovi, D. anchoratus, D. aristichthys, D. baueri, D. dulikeity, D. ctenopharyngodonis, D. extensus, D. hypophthalmichthys, D. intermedius, D. intermedioides, D. lamellatus, D. magnihamotus, D. nobilis, D. sahuensis, D. suchengtaii, D. taihuensis, D. vastator and D. wegeneri. Among these, D. vastator and D. anchoratus infecting common carp and D. lamellatus infecting grass carp are very harmful and were responsible for high mortalities observed in fry and fingerling production in Iran. Uncontrolled import of live fish into the country can lead to transmission of pathogenic monogeneans or other group of parasites to native fishes, causing a great economical and ecological threat to valuable native fishes. For example, transmission of D. anchoratus from common carp to Barbus sharpeyi, an important native fish species, despite of the high host-specificity of monogeneans, indicates the possibility of transmission of exotic monogenean parasites to native hosts. It is strongly suggested that the risk of introducing exotic pathogens along with importing fish or any other living organism to the country, should be assessed well in advance, in order to protect native species and the ecosystem.