This name refers to the chest of the horse bulging outward, resembling a male pigeon strutting around to impress the females. There is no connection to the birds with this bacterial infection. there are many names for this disease including "dryland Distemper", "deep pectoral abscess", "ulcerative lymphangitis" and 'caseous lymphadenitis". There may be a connection to biting flies, however, so strict fly control is very helpful. The bacteria causing this disease is named Corynebacterium Pseudotuberculosis, and the name comes from the bacterial tendency to hide from immunity and medical therapy inside the animals cells the way real Tuberculosis can.
This bacteria also causes disease ( caseous lymphadenitis ) in sheep, goats, cattle, llamas, dogs and may even be spread to humans in rare instances. The most likely theory concerning its spread is that biting insects can spread it. It is capable of living in soil for long periods of time, and ultimitely picked up by the flies and injected into the horse or other animal. It can take a long period of time to localize into a lymph node or a deep muscular abscess, but can rarely even go into the chest or abdomen of the animal and be very hard to diagnose. We see these abscesses in the fall and winter seasons, but that may be because the disease takes so long to develop, that they may be infected in the summer and not show anything until the fall. Dr Humphrey Knight spent his entire career trying to find more about this disease and we still don't know many things for sure about it, nor do we have a vaccine either. It can develop abscesses all along the chest, belly and sheath of horses which can be located by ultrasound imaging and eventually drained with a big needle or opened with a scalpel. I recently drained one, with a big needle, after ultrasound scanning it, and replaced the pus removed, with penicillin. When the culture came back the next week, the abscess was noticeably smaller already and eventually faded away and disappeared on its own, without having to lance it at all. That brings up the question of medical therapy and contagion. It is not considered contagious between horses if the abscess has been cleanly opened and washed out and packed with Betadine and gauze. If the abscess drains naturally and wipes onto another horse, it could infect the other horse in some instances. No one knows for sure about the contagious question, but large stables who quarantine have no different spread of it than those who don't.
The western U.S. has the abscess form of the disease predominantly and the eastern U.S. usually has the 'ulcerative lymphangitis' form of it leading to a very swollen and painful leg. Both forms can occur and often overlap geographically with the western form steadily spreading into states east of California that never used to see it at all.
The use of antibiotics before the abscesses break open, or are lanced, is up to the individual veterinarian since some cases are making the horse sicker than others. Once the abscess opens, usually just flushing it out is all the therapy needed, but the internal abscesses may need antibiotics for many weeks or even months. The painful swollen legs infections will need antibiotics immediately and it may reoccur many times in the horses life. This is a big subject and usually if you ask your local veterinarian about it, the vet can fill you in on the disease in your area. Bob Saunders DVM
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This name refers to the chest of the horse bulging outward, resembling a male pigeon strutting around to impress the females. There is no connection to the birds with this bacterial infection. there are many names for this disease including "dryland Distemper", "deep pectoral abscess", "ulcerative lymphangitis" and 'caseous lymphadenitis". There may be a connection to biting flies, however, so strict fly control is very helpful. The bacteria causing this disease is named Corynebacterium Pseudotuberculosis, and the name comes from the bacterial tendency to hide from immunity and medical therapy inside the animals cells the way real Tuberculosis can.
This bacteria also causes disease ( caseous lymphadenitis ) in sheep, goats, cattle, llamas, dogs and may even be spread to humans in rare instances. The most likely theory concerning its spread is that biting insects can spread it. It is capable of living in soil for long periods of time, and ultimitely picked up by the flies and injected into the horse or other animal. It can take a long period of time to localize into a lymph node or a deep muscular abscess, but can rarely even go into the chest or abdomen of the animal and be very hard to diagnose. We see these abscesses in the fall and winter seasons, but that may be because the disease takes so long to develop, that they may be infected in the summer and not show anything until the fall. Dr Humphrey Knight spent his entire career trying to find more about this disease and we still don't know many things for sure about it, nor do we have a vaccine either. It can develop abscesses all along the chest, belly and sheath of horses which can be located by ultrasound imaging and eventually drained with a big needle or opened with a scalpel. I recently drained one, with a big needle, after ultrasound scanning it, and replaced the pus removed, with penicillin. When the culture came back the next week, the abscess was noticeably smaller already and eventually faded away and disappeared on its own, without having to lance it at all. That brings up the question of medical therapy and contagion. It is not considered contagious between horses if the abscess has been cleanly opened and washed out and packed with Betadine and gauze. If the abscess drains naturally and wipes onto another horse, it could infect the other horse in some instances. No one knows for sure about the contagious question, but large stables who quarantine have no different spread of it than those who don't.
The western U.S. has the abscess form of the disease predominantly and the eastern U.S. usually has the 'ulcerative lymphangitis' form of it leading to a very swollen and painful leg. Both forms can occur and often overlap geographically with the western form steadily spreading into states east of California that never used to see it at all.
The use of antibiotics before the abscesses break open, or are lanced, is up to the individual veterinarian since some cases are making the horse sicker than others. Once the abscess opens, usually just flushing it out is all the therapy needed, but the internal abscesses may need antibiotics for many weeks or even months. The painful swollen legs infections will need antibiotics immediately and it may reoccur many times in the horses life. This is a big subject and usually if you ask your local veterinarian about it, the vet can fill you in on the disease in your area. Bob Saunders DVM