Thyphoid Fever in Poultry

I am poultry vet from Pakistan. It is very hot in Pakistan plain areas and mostly I observe typhoid fever in poultry farms. I use neomycin and furaltadone combination along with water supplements to treat fever and some times florfenicol salt to treat high typhoid fever, but in some farms this practice is not giving me so much good results as it should and I observe enteritis along with typhoid fever and give the same treatment along with probiotics in feed. But from some days not so much good results are coming. Could any doctor help me to increase my skill in the field? I would be very thankful.