Environmental survival of Haemophilus somnus and influence of secretions and excretions.

Environmental survival of the Haemophilus somnus virulent strain 43826 was examined by mixing it with bovine secretions and excretions and observing viability after storage at -70 degrees C, 3 degrees C, 23.5 degrees C and 37 degrees C at one day, five days, 12 days, 19 days and intermittently up to 75 days. Survival of the organism beyond 70 days occurred when it was mixed with cerebrospinal fluid, whole blood, blood plasma, vaginal mucus and milk and frozen at -70 degrees C. At 3 degrees C the organism in these fluids survived for five days or less. At 23.5 degrees C the organism survived beyond 70 days when mixed with whole blood and nasal mucus. The viability of H. somnus in urine at all temperatures was less than 24 hours and less than 15 minutes at 20 degrees C and 37 degrees C. Infective cerebrospinal fluid frozen alone in liquid nitrogen and with the addition of various cryopreservatives allowed the organism to survive and maintain virulence for at least 56 days. The implications of these studies to disease transmission and experimental studies is discussed.