Molecular Study of Colibacillosis Susceptibility in Calves and Lambs

Single nucleotide polymorphism (SNP) is hereditary change in a DNA sequence that occurs when a single nucleotide in a genome is modified; SNPs are usually considered to be point mutations that have been evolutionarily successful enough to recur in a significant proportion of the population of a species. The ability of certain individuals to respond appropriately to Toll-like receptor (TLR) ligands may be impaired by single-nucleotide polymorphisms (SNPs) within TLR genes, terminating in a modified susceptibility to infectious or inflammatory disease that might contribute to the pathogenesis of complex diseases. Out of the 400 clinical samples of blood collected from calves and lambs suffering from diarrhea, the samples originated from Babylon Veterinary Teaching Hospital and Veterinary Clinics during the period from October 2018 to January 2019, 200 samples were suffering from diarrhea (100 samples of calves and 100 samples of lambs), and 200 samples were the control group. Genotyping of TLR4 polymorphisms was carried out by using amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) technique. For calves’ TLR4 (rs8193046) gene polymorphisms, the results showed there were significant differences in genotypes and alleles frequencies between the diarrheic cases and the control group (p < 0.05). GG homozygous genotype was overrepresented among diarrheic calves. The frequencies of G allele was higher in diarrheic calves compared to the control group. The calves’ GG homozygous genotype was significantly associated with increased susceptibility to Colibacillosis in calves. For lamb-TLR4 (rs160202325) gene polymorphism, GA heterozygous genotype was overrepresented among the cases as of 20 (52.63%), whereas AA was obviously more presented among control individuals as of 6 (60%). There were no difference between diarrheic cases and control groups for alleles frequencies.