Yazeed Raouf

The performance of Chekit and Priocheck (Ceditest) 3-ABC ELISAs was evaluated in an area of endemicity using 196 sheep and 45 bovine sera. The Checkit ELISA failed to detect 8 positive sheep sera out of 10 detected by the Priocheck ELISA whilst both ELISAs detected 13 bovine sera as positive or borderline. The dissimilarity in the performance of the two ELISAs in testing sheep field sera, a target population, was shown to be consistent with their reported differences following experimental infection in cattle and was largely due to differences in their methodology. Sera expected to form high affinity and small immune complexes are better detected in the system of Priocheck-NS blocking ELISA while sera expected to form low affinity (recent infection) and large immune complexes are better detected in the latter system of Chekit ELISA. Identification of this aspect is crucial for optimization of these assays and for conclusive interpretation of their results. Prevalence in the test sheep group as detected by the Priocheck ELISA (8.47%) was more pertinent to the expected true prevalence than that detected by the Checkit ELISA (0.51%). The Checkit ELISA could prove to be useful for detection of relatively recent FMD virus circulation and, hence, control plans in enzootic areas. Key words: Foot-and-mouth disease; 3-ABC serology; Ceditest; Priocheck: Chekit ELISA; Blocking ELISA

Mononuclear cells infected with Theileria annulata schizonts were isolated at 4 different times from monolayer cultures of primary kidney cells derived from apparently healthy, 2 to 6 weeks old zebu calves. The presence of such an organism could interfere with the manufacturing procedure of rinderpest tissue culture vaccine if it is to be carried out in calf kidney cell culture.

The performance of Chekit and Priocheck (Ceditest) 3-ABC ELISAs was evaluated in an area of endemicity using 196 sheep and 45 bovine sera. The Checkit ELISA failed to detect 8 positive sheep sera out of 10 detected by the Priocheck ELISA whilst both ELISAs detected 13 bovine sera as positive or borderline. The dissimilarity in the performance of the two ELISAs in testing sheep field sera, a target population, was shown to be consistent with their reported differences following experimental infection in cattle and was largely due to differences in their methodology. Sera expected to form high affinity and small immune complexes are better detected in the system of Priocheck-NS blocking ELISA while sera expected to form low affinity (recent infection) and large immune complexes are better detected in the latter system of Chekit ELISA. Identification of this aspect is crucial for optimization of these assays and for conclusive interpretation of their results. Prevalence in the test she...

Like other East African countries, Sudan experienced circulation of several SAT2 topotypes. In Sudan, topotype XIII and VII of SAT2 virus were recorded. This work meant to evaluate the impact of such diversity on diagnosis and control. A Sudanese SAT2 foot-and-mouth disease virus (FMDV) of topotype VII originated in 2010 showed poor antigenic relationship (r1 value ≈ 0.00) with Sudanese SAT2 FMDV from 2008 when topotype XIII was circulating. After one or three doses of a vaccine derived from SAT2 virus in 2010, heterologous antibody titres with SAT2 virus in 2008 were ≤ 1.2 log 10, not consistent with likely protection, while homologous titres were 1.65 (after one dose) or 1.95 and 2.55 log10 (after 3 doses). SAT2 positive field sera from Sudan in 2016 were not unvaryingly identified by virus neutralization tests (VNT) employing SAT2 viruses from 2010 and 2008. Proportions of positive sera by SAT2 virus from 2010 were always higher than those by viruses from 2008; consistent with th...

Two hundred and eleven sera collected in 2005 from cattle in Khartoum state, in Central Sudan, were examined for antibodies against SAT1 serotype of foot-and-mouth disease virus using the liquid-phase blocking ELISA. The ELISA was modified for the single dilution test ...

Mononuclear cells infected with Theileria annulata schizonts were isolated at 4 different times from monolayer cultures of primary kidney cells derived from apparently healthy, 2 to 6 weeks old zebu calves. The presence of such an organism could interfere with the manufacturing procedure of rinderpest tissue culture vaccine if it is to be carried out in calf kidney cell culture.

Foot-and-mouth disease (FMD) is widely distributed in Sudan where outbreaks occur on an annual basis especially during the winter months (December-February). This study aimed to increase our understanding of the epidemiological patterns of FMD in Sudan and connections to neighbouring countries by characterising the genetic sequences of FMD viruses (FMDV) collected from seven Sudanese states over a 10-year period (between 2009 and 2018). FMDV was detected in 91 of the 265 samples using an antigen-detection ELISA. Three serotypes were detected: O (46.2%), A (34.1%), and SAT 2 (19.8%). Fifty-three of these samples were submitted for sequence analyses, generating sequences that were characterised as belonging to O/EA-3 (n=18), A/AFRICA/G-IV (n=23) and SAT 2/VII/Alx-12 (n=12) viral lineages. Phylogenetic analyses provided evidence that FMDV lineages were maintained within Sudan, and also highlighted epidemiological connections to FMD outbreaks reported in neighbouring countries in East and North Africa (such as Ethiopia and Egypt). This study motivates continued FMD surveillance in Sudan to monitor the circulating viral lineages and broader initiatives to improve our understanding of the epidemiological risks in the region.