الفهرس 
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Abstract
Avian Mycoplasmosis are considered one of the important
economic problems for chickens, therefore methods of control should be applied to protect against infection.
This study included the following items
Examination of broiler flocks including 200 chicks of
different ages ranged from one day old till 48 days old obtained from 10 different Governorates of Egypt. These flocks were suffering from respiratory signs
Eighty (13.3% ) mycoplasma isolates were recovered out of 600 samples collected from tracheae, lungs and air sacs from 200 examined broiler chickens. The highest isolation rate was from 5-7 weeks old chickens, while the lower rate from the 1-14 days old chicks. The percentage of isolation of mycoplasma from lungs
tacheae, air sacs were 7% ,11.5 % and 21.5 % respectively. The isolates of M gczilisepticum from the lungs ,tracheae and air• sacs of the examined naturally infected broilers were 35 (43.7) out of the total mycoplasma isolates. The highest percentage of isolation ofM gaiZisepticum was at the ages of 5 – 7 weeks and the least percentage was at one day to 14 day old.
The percentage of isolation ofM gallisepticum from lungs,
tacheae, air sacs were 10%, 13.7 % and 20 % respectively. Serum samples collected from naturally infected broiler chickens were tested for the presence of antibodies against M gallisepticum by SPA and the 45 samples were positive with percentage of 45%.
Results of examination, by using ELISA, of the serum
samples collected at the age ranging 35-48 days from naturally infected broiler chickens by ELISA to detect M. gallisepticum antibody revealed that 45 (45%) samples were positive , 38 samples (38%) were negative and 17 samples (17%) were
suspected. Antibiotic sensitivity test was carried out to study the sensetivity of the representing M gallisepticum isolates for 10 different antibiotics. The results revealed that these strains of M gallisepticum were highly sensetive to enrofixacin. The experimental infection was carried out to evaluate the efficiency of enrofloxacin as an anti-Mycoplasma gallisepticum compound. 120 one day old broiler chicks (Hubbered) were used in this experiment. Eight from these chicks were investigated seologically and culturally and were found to be negative for mycoplasma. At the age of 21 days the brioler chicks were divided into 6 subgroups beside a control negative group and each
of them was treated as foliwoing:
1- The first subgroup was experimentally infected by
Iv.! gallisepticum (S6) strain, then after one week of infection
chicks were treated by enrofloxacin.
2- The second subgroup was experimentally infected by field
strain of M gilisepticurn and then treated after one week of
infection with enrofloxacin.
3- The third subgroup was given enrofloxacin as a prophylactic
medication for 3 days followed by experimental infection by M. gallisepticurn (S6) strain.
4- The fourth subgroup was given enrofloxacin as a prophylactic
medication for three days followed by experimental infection with M gallisepticum field strain.
5- The fiveth subgroup was experimentally infected with
Iv! gallisepticurn (S6) strain and considered as control
positive. 6- The sixth subgroup was experimentally infected with lvi. gcsllisepticum field strain and considered as control positive.
7- The control negative group kept nontreated noninfected
from the results of the experimental infection, it was
concluded that
1- There were no deathes allover the observation period of the experiment.
2- Symptoms, postmortem lesions were more severe in birds
which exposed to artificial inoculation and not received
enrofloxacin (control positive birds) than those exposed to the artificial infection and received enrofloxacin.
3- There were significant increase in body weights in chickens treated with enrofloxacin more than in chickens experimentally infected by either Al. gallisepticztm (S6) strain or Al gallisepticum field isolate and not treated with enrofloxacin and also more than that birds which kept as a nontreated noninfected (negative control). 4- Serological studies were carried out for the detection of
mycoplasma antibodies by using SPA test and ELISA, and it
was confirmed that ELISA was more specific.
5- Reisolation rates for M gailisepticum from the experimentally infected chickens were lower in enrofloxacin treated groups than in non treated groups.