Haemophilus somnus is a common bacteria known to cause many disease processes in cattle, sheep, goats and bison. The bacteria are most devastating in feedlots and backgounding cattle, where it is the causative agent for ITEME (Infectious Thrombo-Embolic-Meningo- Encephalitis). This bacteria has also been linked to arthritis, pneumonia, abortion, septicemia and heart failure.
ITEME generally occurs 4-6 weeks after the livestock have been on feed in the feedlot or been grouped together. The affected cattle will show signs of encephalitis (brain infection) as this bacteria is attracted to nervous tissue. Signs will include blindness, staggering and they eventually progress to the animal laying on its side convulsing. These animals are often just found dead in the pen. In less severe cases, affected animals will display signs of pneumonia. This pneumonia is very similar to that of Shipping Fever. A common outcome to the pneumonia is septicemia, meaning it is in the blood and spreading all over the body. These calves may develop stiffness and arthritis, which usually affects the stifles and hocks. In backgrounding situations, the bacteria can be spread to the cow herd where it may have an effect on fertility.
Diagnosis of ITEME is generally straight forward. The diagnosis is based on the history of feedlot animals in the fall months developing nervous signs with or without arthritis and pneumonia. The differential diagnosis for the nervous signs includes Polioencephalomacia (Polio), grain overload and lead poisoning.
During an outbreak, prompt treatment must be initiated immediately. Broad spectrum antibiotics should be used in all the animals affected and comingled with affected calves. These animals may also be treated with thiamine to aid in the protection of the brain. Treatment can be successful if started early in the process. The brain damage caused by H. somnus is irreversible, so even if the animal is treated and survives it may have to be culled. Other cattle in the feedlot should be checked every 2 hours. Prognosis is poor if the animal is already down. Mortality rate can be as high as 90% in some outbreaks.
Because ITEME has such a devastating effect on a group of animals, prevention is vital. At Twin Valley Veterinary Health Services, we recommend that all calves are vaccinated against H. somnus. We recommend vaccinating with Fermicon 7/Somnugen, our Black Leg vaccine that also protects for ITEME. Calves should be vaccinated in the spring as new borns, in the fall at weaning and again as yearlings the next spring. The vaccine can be given as early as one week of age and is also safe in pregnant females.
If you have any questions regarding the above information or any questions/concerns in general, please contact Twin Valley VHS at 745-6642.
Dr. Justin Noble DVM
Twin Valley Veterinary Health Services