Genova identifies multiple H. somni strains
Histophilus somni
Histophilus somni can cause a myriad of problems in cattle including respiratory, cardiovascular, musculoskeletal, nervous system and reproductive disorders. H. somni, a gram-negative bacteria, may first be evident by sudden death of the animal as a result of pneumonia. Usually clinical signs in infected animals include fever, anorexia, and profound depression.
Current Field Observations
Many veterinarians do not believe the currently available commercial products are preventing H. somni as well as they should and are switching to custom, autogenous vaccines. The next question becomes where to get the isolate? With central nervous system cases, the best locations to look for lesions are in the brain and spinal column. For pneumonic cases, look for a yellow jelly-like mass or blob in the lung. If lameness has occurred or the joint area is swollen, you will usually find fluid which can be another source for an isolate. Many times if you open the pericardial sac you will see evidence of infection and if you slice into the papillary muscle often times you will see a cauliflower type growth which is also a good indication of H. somni. Swabs from these areas need to be sent to your diagnostic lab for isolation of H. somni.
Reproductive and Urinary Tract Form
The reproductive form of the disease infects the uterine tract and if the cow is pregnant causes death of the fetus and abortion. The organism then spreads to the vaginal tract and subsequent discharges or urine can spread the disease to other animals. Bulls breeding infected cows can also develop the disease. Other animals can become infected from urine splatter or smelling the vaginal discharge. The reproductive form of the disease, when transmitted to other animals, often manifests itself as a respiratory infection in subsequent animals.
Respiratory Form
The respiratory form of H. somni can affect both the upper and lower respiratory tract. Often when the organism hits the lungs, it results in severe pneumonia and sudden death. It can be the primary cause of pneumonia but is often quickly overgrown by opportunistic bacteria such as Pasteurella multocida and Mannheimia haemolytica. Upon postmortem often times the lungs are heavily overgrown with these other organisms and evidence of H. somni is difficult to
see or locate.
Septicemic Form
The septicemic form H. somni often affects the central nervous system and often results in death unless treated early. The organism circulates through the blood and if it colonizes, it produces a clot blocking the blood flow. The size of the clot and the resulting reduction or elimination of blood flow determines the severity of the clinical signs. If the clot occurs in the brain or spinal column, symptoms can be an altered gait, walking in circles, knuckling over at the fetlocks and eventually the animal will appear to be blind. At this stage, the animal eventually has convulsions. This leads to a comatose state and eventually death. The septicemic form may also affect the joints causing chronic arthritis, swollen joints and chronic lameness.
Miscellaneous Forms
H. somni also occurs in the ears and eyes of cattle. The ear form is characterized by a yellowish discharge coming from the ear canal. The eye form affects the conjunctiva and causes a reddening of the eye, excessive tearing and squinting.
Any form of the disease can cause any of the other forms of the disease. In a cow herd, the infection has a tendency to reach the uterus, thus the reproductive tract is thought to be the reservoir of the disease.
Treatment
Early treatment of H. somni infections is required in order to reduce the number of chronically affected animals and to control mortality. The new generation antibiotics are effective if treatment begins early.
Prevention
A custom vaccine utilizing multiple H. somni isolates from that specific herd can be scientifically formulated by Genova using the herd’s own strains in your vaccination program.