Sheep-associated malignant catarrhal fever involving 3-5-week-old calves in Saudi Arabia.

Between late December 1999 and late April 2000, three locally bred Friesian calves (ageing 25, 28 and 35 days) in a dairy farm, at Al-Ahsa locality of the eastern region of Saudi Arabia showed dullness and inappetence. Their rectal temperatures ranged between 41 and 41.5 degrees C. One to 2 days later and onwards, the calves showed lacrimation, nasal discharge, salivation, oedema of the head, conjunctivitis, exo-ophthalmia and corneal opacity. One calf showed diarrhoea. The superficial lymph nodes were oedematous and swollen. The calves died after 7, 5 and 8 days, respectively, following the onset of the disease. Calves and rabbits were experimentally infected with materials from the naturally infected calves. The rabbits showed fever, mild conjunctivitis and one rabbit showed wet faeces. The experimentally inoculated calves showed rise in temperature and mild symptoms but none of them died. The virus from the naturally infected calves and from the experimentally infected rabbits was identified as malignant catarrhal fever (MCF) virus using both the complement fixation test and the fluorescent antibody test, employing a reference anti-serum against the WC 11 strain of MCF virus. Serological survey for MCF antibodies in cattle, sheep and goats from the affected farm revealed that 54% of the examined animals were positive. The situation of MCF in Saudi Arabia was discussed in relation to sheep and wild game. This paper constitutes the first report of MCF in Saudi Arabia and the Gulf region.

Study of Akabane infection in Saudi Arabia by the use of sentinel ruminants.

Two sentinel herds of calves (Eastern and Central regions of Saudi Arabia) and one of sheep and goats (South Western region) were established to study Akabane virus infection. The herd at the Al-Ahsa oasis (Eastern region) showed evidence of Akabane viral activity, as reflected by the presence of maternal (colostral) antibody, which had waned to insignificant concentrations by the time the calves had reached the age of 5 months. There was no evidence of subsequent seroconversion. The other two sentinel herds gave no indication of Akabane viral activity.

Experimental study of vaccines against Salmonella typhimurium infection.

Serological and protective activities of vaccines from S. typhimurium and S. minnesota were studied. It has been demonstrated that active protection against infection in experimental salmonellosis in mice can only be obtained by immunization of the animals using vaccines from complete antigenic complexes isolated from S-strains. It has been found that expressed anti-infection immunity (unlike anti-endotoxic immunity) is induced to the same extent by either high-molecular components (2,000,000 daltons and more), showing great serological activity, or components with relatively low molecular weight (15,000--20,000 daltons) and minimum serological activity. Vaccines from Ra- and Re-strains of S. minnesota do not induce resistance to S. typhimurium infection in mice in either active protection tests or passive protection tests.

[Immunologic study of R-mutants of S. minnesota and water-soluble antigens of S. typhimurium]. / Immunologicheskoe izuchenie R-mutantov S. minnesota i vodorastvorimykh antigenov S. typhimurium.

Protective properties of Ra- and Re-chemotypes of S. minnesota were studied in experiments on active and passive protection of albino mice from infection with a virulent S. typhimurium culture. Vaccines prepared from the Ra- and Re-mutants of S. minnesota were administered to the animals in the sum total dose of from 0.05 to 0.6 mg. Hyperimmune and normal rabbit sera were administered in doses of 0.3 and 0.5 ml. S. mineesota Ra- and Re-mutants in the doses tested proved to possess a weak protective activity: the level of the immunized mice nonspecific protection from the experimental salmonellosis failed to exceed the natural resistance level. Immunogenicity of Ra-mutant was markedly greater than the immunogenicity of Re-mutant. A marked protective activity against the experimental salmonellosis in mice was possessed by the antigenic complexes from the homologous strain only.