الفهرس 
Cover PageOnly 14 pages are availabe for public view
 |  | from | 157 |  |  |
| | | from | 157 | | |
Abstract
The incidence of Histophilus. somni among desert sheep was determined by bacteriological
examination of 185 swabs collected from sheep suffering from respiratory disorders and 425 nasal and
pharyngeal swabs collected from apparently healthy sheep. 45 isolates of H. somni were recovered
from respiratory diseased animals at a percentage of 24.4%, where as no isolates were obtained from
cultivation of swabs collected from healthy animals. The correlation between seasonal variation and
percent of respiratory disorders attributed to H. somni was studied in the present investigation. It was
observed that the highest incidence of disease occurred during autumn and winter with a percent of
34.7% and 15% respectively. No respiratory affections appeared during summer or spring. The
incidence of H. somni in the reproductive system of sheep and goat was investigated by bacteriological
examination of 120 vaginal swab collected from apparent healthy sheep and 80 swabs from apparent
healthy goats. Failed detection of H. somni which indicates that Hsomni cannot be considered as
normal inhabitant of respiratory and reproductive tract of small ruminants and its presence indicates
infection of small ruminants but symptoms depend on the virulence of the isolated H.somni. The
biochemical characteristics of 45 isolates of H. somni were studied. All strains were oxidase, nitrate
positive and urease negative. Carbohydrate fermentation showed fermentation of glucose and sucrose
by all isolates, but lactose fermentation and catalase activity, indole and H2S gave variable results. A
representative of each of 6 groups of the 45 H. somni isolates classified according to their virulence
was selected for performing pathogenicity test of H. somni in guinea pigs and mice. Four strains No (l ,
2,3,5) showed pathogenicity for both animals, while isolates No (4,6) were non pathogenic.
Histopathological studies of experimentally infected guinea pig and mice with virulent isolates,
revealed the following: features were embolic meningitis, pneumonia and congestion in spleen, kidney
and liver .which indicating that H. somni can’t be considered as normal inhabitant of respiratory and
reproductive tract of small ruminants and its presence indicates infection of small ruminants but
symptoms depend on the virulence of H. somni Antigenic relationship between H. somni was
performed by studying the cross reactivity between hyperinunune sera prepared from each of the 6
isolates and homologous and heterologous strains by using agglutination test. Cross reactivity could be
detected between heterologous antigens, but agglutination test with homologous antigen was more
prominent. SDS-protein profile analysis of whole cell proteins revealed the presence of common 7
protein bands between the 6 different H. somni isolates while 49 bands were polymorphic. A unique
band ranged from 27 to 37 KDa isolated to OMP was detected in pathogenic strains No (I, 2, 3, 5)
and was not present in OMP of the non pathogenic isolates No (4, 6). 100% protection could be
obtained by vaccination of guinea pigs with bacterin prepared from formalin inactivated whole cell of
H. somni No (1) while vaccination with bacterins prepared from non pathogenic isolates did not protect
animals against challenge with virulent strains of H. somni. -The present investigation revealed that
pathogenicity of H. somni can be correlated with the presence of band of protein ranged from 27 to 37
KDa protein associated with the OMPs of virulent strains only and can be considered as the protective
antigen present in bacterin vaccine. 11- Antimicrobial sensitivity test was carried out on 45 Histophilus
somni isolates. They were highly sensitive to Amoxycillin+ clapulanate potassium, Cefotaxime sodum,
Gentamicin, Kanamycin and Novobiocin (100% each). And intermediately susceptible to Amoxicillin
(64.4%) Chloramphenicol ,Sulpha Methoxazole-Trimethoprim and Thiamphenicol (33.3%) for each,
Ampicillin (22%), Streptomycin (13.3%). On the other hand, the resistance pattern among the H. somni
was sebheridine (77.7%), Sulpha Methoxazole-Trimethoprim (66%), Streptomycin (53.3%),
Amoxicillin (35.5%), Cefoberazone (33.3%), Norfloxacin (28.8%), Chloramphenicol and
Erythromycin (22.2%) for each, Thiamphenicol (l3%).