Patil, R.D.Priyanka2023-02-232023-02-232022-12-17https://krishikosh.egranth.ac.in/handle/1/5810194322The present study was conducted to determine the pathology caused by Escherichia coli infection in bovine calves in Himachal Pradesh. A total of 222 fecal samples were collected from dead, clinically sick and apparently healthy calves upto one year of age. Necropsy examination of 30 calves upto one year of age including 24 males and 6 females was done during the time period of 1 June, 2021 to 30 June, 2022. Grossly, enteritis was present in 26 (86.67%) calves, ulcerative abomasitis in 5 cases (16.67%), diptheretic enteritis in 1 case (3.33%), milk rumenitis in 1 case (3.33%), nodular abomasitis in 1 case (3.33%) and haemorrhagic typhlitis in 1 (3.33%) case. Histopathologically, vascular changes (congestion, edema, haemorrhages etc.), villous denudation and sloughing, cryptal necrosis, hyperplastic activity of enterocytes, increased goblet cell activity and infiltration of inflammatory cells were the consistent findings. Along with this, macroshizonts and microschizonts of coccidia in tips of villi, bacterial colonies, depletion of lymphocytic element from Peyer’s patches and proliferation of fibrous connective tissue in Peyer’s patches were also found. E. coli was found to be the major cause for gastrointestinal pathologies (55.78%) and responsible for deaths among calves. The prevalence of E. coli in Himachal Pradesh was found to be 47.75% out of which pathogenic E. coli contributed to 40.1%. Molecular pathotyping revealed that enteropathogenic E. coli (EPEC) was present in 57/222 (25.67%) samples, enterohaemorrhagic E. coli (EHEC) was 31/222 (13.96%), enterotoxigenic E. coli (ETEC) was 28/222 (12.61%) and enteroaggregative E. coli (EAEC) was present in 80/222 (36.04%) fecal samples. 25 different serotypes of all the 106 E. coli isolates were identified with serotype O119 (12.26%) being most common followed by O98 (10.38%) and O126 (9.43%). CST for 106 isolates of E. coli against 16 commonly used antibiotics revealed that highest resistance was shown by Cloxacillin (58.49%) followed by Furazolidone (53.77%). 21 E. coli isolates were found to be resistant against one antibiotic group, 17 were resistant against two antibiotic groups, 26 were found to show resistance against three antibiotic groups and rest 42 samples were resistant to more than three antibiotic groups. Upon screening of 15 plant extracts (50% aqua- alcoholic) for their antimicrobial potential against 6 serotypes of multidrug resistant (MDR)-E.coli, five plant extracts i.e. Artemisia nilagirica (C.B. Clarke) Pamp., Asparagus adscendens Roxb., Phyllanthus urinaria, Physalis peruviana Linn. and Tinospora cordifolia were found to have zones of inhibition of varying diameters at different concentrations. In conclusion, the present study revealed that E. coli infection leading to enteritis was the major cause of death in bovine calves upto 1 year of age in Himachal Pradesh. The plant extracts seem to be future alternative to counteract the antimicrobial resistance in animals and humans.EnglishThesis