Are there effective herbal therapies to treat salmonella?

No. Salmonella enteritis infection usually resolves without the need of any antibiotic treatment. For severe infections or infections in immunocompromised patients several antibiotics are effective. There are no effective herbal treatments for salmonella infections.
Yes. Daily consumption of coriander seeds, or fresh coriander leaves or black cumin can help to prevent or reduce the effects of salmonella.