Prevalence of Antibodies Against three Active Types of Foot and Mouth Disease Virus in Cattle in Khartoum State at Central Sudan: Epidemiological Significance

Abstract

Prevalence of antibody against types “O”, “A” and “SAT2” of foot-and-mouth disease virus (FMDV) was studied in cattle sera collected in the year 2005 from Khartoum State at central Sudan, using the liquid-phase blocking ELISA (LPBE). The test was optimized for the screening assay by selection of optimum antigen doses that produced parallel serum titration curves. Results showed high prevalence of type “A” antibody (85.65%) followed by that of type “O” (81%) then “SAT2” antibody (65.78%). Apart from an observed natural resistance in local breeds to type “O” infection, no epidemiological factor seemed to affect separately the prevalence’s of each of the three serotypes; prevalence rates of the serotype-specific antibody increased or decreased simultaneously in different locations. Prevalence was higher in the west and south than in the east and north of the State, coinciding with the known direction of animal movements in Sudan, and higher near traffic lines than in milking farms, where sedentary type of management prevails. The result indicated the maintained activity of three serotypes of FMDV at central Sudan. Prevalence of type “O” antibody was similar to that previously reported in Sudanese cattle and that of “SAT2” was coinciding with the history of its introduction in Sudan. The much higher prevalence of type “A” antibody than the earlier report was likely to be due to testing of sera at low dilution (1/32) in the present LPBE in comparison to high dilutions (1/100 to 1/200) in previous work. This is apparently more to be relevant since the present LPBE distinguished positivity to type “A” from that to type “O” and “SAT2” by lower number of strong positive sera and more sharp decline of their titration curves, consistent with the known antigenic diversity of this virus type.