John's Disease (J.D.)
A specific infectious chronic enteritis affecting cattle usually of 2 - 6 years age group. Sheep and goats are also affected. Caused by Mycobacterium paratuberculosis. Chronic emaciation in spite of normal appetite. Chronic recurrent diarrhoea which does not respond to treatment. Intestinal mucosa thickend and corrugated. Absorption of nutrients does not occur.
Confirmation
Scrapings from rectal m.m.. for acid-fast bacilli in epithelial cell. Serum for C.F. test. Allergic test. Johnin test (Single intradermal test using 0.2 ml. Johnin in the skin of neck. Appreciable oedematous swelling at 48 hrs. indicates positive reaction. Double intradermal testing with Avian tuberculin is also conducted.
Fecal Microscopic Examination:
Collect Faecal samples directly from rectum. One gram faecal sample is triturated with pestle and inortar in NSS. Centrifuge triturated mixture at 2000 rpm for 10 minutes. Prepare smears from supernatant of these samples and stain with hiezl-Neelson method of acid fost staining.
Treatment
Infection is very resistant to treat. Streptomycin @ 25 mg kg body wt. given a prolonged period effects only a transient recovery, hence not economical and usually not advocated Inj. Streptomycin 5 gm vial is now available.
Control By segregation. No vaccine available.