Preliminary seromonitoring of rinderpest among cattle raised under different husbandry systems in Saudi Arabia.

Using the competitive enzyme-linked immunosorbent assay for the seromonitoring of rinderpest in Saudi Arabia, antibodies were detected in 30% of the sera of 1,018 cattle slaughtered at Riyadh abattoir during June and July 1995. The correlation between the detection of antibodies and the origins of the slaughtered animals was analysed. All the culled dairy cows had detectable antibodies. The proportions of bulls giving serologically positive results were as follows: 57% for animals imported from rinderpest-free countries and vaccinated upon arrival in Saudi quarantine, 20% for native breeding animals and 17% for five- to ten-month-old bull calves born on commercial dairy farms and then raised on separate feedlot farms. In addition, of 105 native cattle sacrificed during the Hajj season in May 1994, 77% had antibodies against rinderpest virus. On the other hand, testing of 17 groups of dairy heifers (from 1 week to 24 months of age), born to immune dams and vaccinated against rinderpest at the ages of six and ten months, revealed the absence of detectable antibodies in the sera of some animals which were between two and ten months of age. Results are interpreted in relation to evaluation of the continuing vaccination programmes and their efficacy as an element of the national programme for the control of rinderpest.

Control of Brucella melitensis infection in a large camel herd in Saudi Arabia using antibiotherapy and vaccination with Rev. 1 vaccine.

The authors describe an attempt to control Brucella melitensis infection in a large camel herd in Saudi Arabia. Sera from the entire herd (2,536) were examined by the Rose Bengal and standard United States of America buffered plate agglutination tests. The overall Brucella seroprevalence was 8%. Milk samples from the 120 seropositive milking camels were cultured on Brucella-selective media. B. melitensis biovars 1, 2 and 3 were isolated from 41 camels (34%). Seropositive camels (202) were treated for the first time with a combination of long-acting oxytetracycline (OTC) at a dose of 25 mg/kg administered intramuscularly (i.m.) every 2 days for 30 days and streptomycin at 25 mg/kg i.m. every 2 days for 16 days. In addition, milking camels were given OTC-intramammary infusion at a rate of 10 ml/teat every 2 days for 8 days. This regimen was found to be effective in eliminating the shedding of Brucella organisms by camels, with no relapse. Moreover, all treated camels became seronegative within 16 months after treatment. Seronegative camels (2,331) were vaccinated for the first time with the B. melitensis Rev. 1 strain vaccine, as follows: a) 175 young camels (aged three months to one year) were each inoculated subcutaneously with a full dose (1-2 x 10(9) viable organisms in 1 ml). Brucella antibody titres between 1:50 and 1:200 were detected 2-4 weeks post-vaccination. Brucella antibodies decreased gradually until the animals became seronegative 8 months after vaccination. b) 2,156 camels aged more than one year were each inoculated subcutaneously with a reduced dose (1-2 x 10(6) viable organisms in 1 ml). Antibody titres measured 2-4 weeks post-vaccination varied from 1:25 to 1:200. The titres decreased gradually, until the animals became seronegative 3 months post-vaccination. No Brucella organisms were recovered from repeated udder secretion samples from all vaccinated milking camels, and no abortions were recorded among pregnant vaccinated camels.

Serological survey of foot and mouth disease in Saudi Arabia.

An immunodiffusion test using foot and mouth disease (FMD) virus infection-associated (VIA) antigen was used to detect precipitating antibodies in serum samples collected from non-vaccinated indigenous ruminants raised in different regions of Saudi Arabia. Of 5,985 sheep sera, 1,371 goat sera, 1,052 cattle sera and 694 serum samples from unspecified species of ruminants, precipitating activity was detected in 1,209 (20%), 127 (9%), 172 (16%) and 38 (5%) samples, respectively. In addition, 100 sera showing precipitating activity against VIA antigen originating from 13 different regions were tested for the presence of naturally-occurring neutralising antibodies against the four serotypes of FMD virus (O, A, Asia 1, and C) currently prevalent in the region and incorporated in the vaccine being used. All sera tested gave varying titres against serotypes O, A and/or Asia 1. However, none of the sera showed neutralising activities against serotype C. The results obtained are interpreted with regard to the geographical distribution and epizootiology of FMD in Saudi Arabia.

Successful therapeutic regimens for treating Brucella melitensis and Brucella abortus infections in cows.

Three therapeutic regimens were evaluated in 121 cows naturally infected with Brucella melitensis or Brucella abortus, using a combination of long-acting oxytetracycline (LA-OTC), streptomycin (ST) and OTC-intramammary infusion (IMI). Cessation of shedding of Brucella in udder secretions and absence of Brucella in selected tissues were considered criteria for successful treatment. Regimen A (tested on 35 cows) consisted of LA-OTC 25 mg/kg administered intramuscularly (i.m.) every 3 days for 42 days, ST 25 mg/kg i.m. daily for 8 days, and OTC-IMI 20 ml/teat daily for 4 days. Regimen B (tested on 53 cows) was similar to regimen A, except that ST was administered every 2 days for 16 days and OTC-IMI every 2 days for 8 days. Both regimens were equally effective in eliminating Brucella organisms from all cows involved in the tests and no relapses were recorded. However, regimen C, which was similar to regimen A, except that ST was administered every 3 days for 24 days and OTC-IMI every 3 days for 12 days, resulted in the elimination of Brucella organisms from only 30 (91%) of 33 cows. Before commencement of the therapeutic regimens, B. melitensis biovar 1 or 2 had been repeatedly isolated from udder secretions of 103 cows and B. abortus biovar 1 from mammary secretions of 18 cows.

Application of double sandwich enzyme-linked immunosorbent assay for the diagnosis of foot-and-mouth disease in Saudi Arabia.

Using foot-and-mouth disease (FMD) diagnostic reagents provided by the FMD-World Reference Laboratory, Pirbright (United Kingdom), an indirect sandwich enzyme-linked immunosorbent assay (ELISA) was applied for local diagnosis of FMD in the Kingdom of Saudi Arabia. Testing epithelial tissues and/or vesicular fluids, it was possible to carry out serotyping of FMD virus before its isolation in cell cultures. All the field samples received as well as the oesophageal pharyngeal fluids collected from apparently healthy animals were inoculated onto primary bovine kidney cell cultures and the isolated FMD viruses then serotyped by ELISA. Testing of samples received from 43 outbreaks revealed positive FMD diagnosis in 29 outbreaks (27 caused by serotype "O" and 2 caused by serotype "A" of FMD virus). In addition, ELISA serotyping of 35 carrier strains of FMD virus (isolated from 286 proband samples) revealed 28 serotype "O" and 7 serotype "A" FMD viral isolates. The results are discussed concerning the importance of applying local FMD diagnosis and the current epizootiological status of the disease in Saudi Arabia.

Development of a live cell culture camelpox vaccine.

A Saudi isolate of camel orthopoxvirus was serially propagated on monolayers of camel kidney cell cultures. The attenuation of the 78th passage was tested in two susceptible camels. Two other susceptible camels were inoculated with vaccinia virus four times propagated in camel kidney cell cultures. The four inoculated camels showed no postinoculation clinical symptoms and formed neutralizing antibodies against both the camel orthopox and vaccinia viruses. No postchallenge clinical symptoms were observed in these four camels, while two non-inoculated contact control camels showed typical symptoms of generalized camelpox. These results indicated the safety and potency of the 78th passage of the Saudi isolate of camel orthopoxvirus (designated Jouf-78) to be used for production of live attenuated cell culture camelpox vaccine. The field testing of the vaccine was carried out on two farms using at least 10(3) TCID50 as a recommended field dose. None of the inoculated camels showed any postvaccination reaction and the serological tests showed seroconversion of many vaccinated field camels. The relationship between camel orthopoxvirus and vaccinia virus as well as the advantages of the live attenuated camelpox vaccine are discussed.