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Abstract

ABSTRACT


The aim of study were to use whey proteins loci as genetic markers to clarify the expected relationships between specific alleles and susceptibility to infection by brucella. A total number of 48 dairy cows, located at Sharkia province in Egypt during a period extended from 2004 to 2005, were examined for brucellosis using different serological tests at dairy laboratory, National Research Centre. The incidence of brucellosis among examined cows by different diagnostic tests on milk and whey were 11 22.91, 10 20.83, 8 16.66, 7 14.58 and 11 22.91 with Milk Ring test MRT, Whey Rose Bengal Plate test WRBPT, Whey Microtiter Agglutination test WMAT, Whey Dithiothereitol Agglutination test WDAT and Brucellin skin test, respectively. The results of absolute specificity were 26.31, 20.0, 17.07, 29.72 and 29.72 with WRBPT, WMAT, WDAT and MRT, respectively. The highest incidence of Brucellin skin test 22.91 indicated that the sensitivity of this test, which depends upon the cellular immunity response, was independent on production of specific antibodies. The concordances between reactors cows in the different tests in this study were 100.0, 97.51, 93.75 and 91.66 for MRT, WRBPT, WMAT and WDAT, respectively. It is noticed that the DHT achieved the highest agreement with MRT 100. Only one isolate of Brucella melitensis biovar 3 could be isolated from milk samples, which gave positive with MRT. The electrophoretic results evident that the whey of cows included obtained closed bands in case of infected samples if compared with free and healthy one. Within -Lg three genotypes were observed AA, AC and CC. Homozygote CC had the greatest number 5 of these genotypes, but, heterozygote AC had the lowest number 1. A higher frequency for allele C of -Lg than allele A of -Lg gene was observed 0.687 and 0.312, respectively. Within -La the presence of three genotypes were appeared AA, AB and BB, the highest number being recorded for homozygote BB with higher frequency in -LaB gene 0.812 than in all fractions of whey proteins. Concerning the -globulin S2, the same genotypes of -La were observed for this fraction, with higher frequency in S2B than S2A 0.687 and 0.312, respectively. The observed homozygous genotype in -Lg, -La and -globulin variants of whey proteins were higher than those expected heterozygous genotypes. Results revealed that the infected cows suffering from brucella distinguished by high frequency of homozygotic genotypes in all studied loci with predominance of -LaB gene marker.

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