Equine Lymphangitis
Encyclopedia
Lymphangitis in horses is an inflammation or swelling associated with impairment of the lymphatic system
, particularly in a limb. It is most commonly a bacterial infection, although bacterial culture may be negative.
Often referred to as Fat/Big Leg Disease, it is sometimes known as Weed or Monday Morning Disease (not to be confused with the more common usage of MMD referring to Exertional Rhabdomyolysis/Azoturia
).
This article refers mainly to Sporadic Lymphangitis. Ulcerative lymphangitis is referred to in passing, as it is managed in a similar manner. Epizootic Lymphangitis
is similar to glanders
, but caused by the fungus Histoplasma farciminosum
.
has been cultured from some cases (particularly of ulcerative lymphangitis; however, in others, bacterial culture is negative. This may be because:
Of these, a) is thought to be the most likely, and d) the most improbable.
, or occasionally as far proximally as the stifle
. In some cases swelling continues through the udder or sheath and along the subcutaneous abdominal veins. In the early stages, the swelling is primarily a "pitting oedema"; in other words, if pressed, a depression remains in the skin of the limb. The affected leg may reach twice or even three times its normal size, and may be very sensitive to the touch. In chronic cases, much of the swelling is firm, as scarring and fibrosis occur.
Lymphangitis is commonly associated with a wound, which may be very minor. This is a likely entrance for bacterial access to the lymph ducts.
The degree of lameness
is variable, but may be sufficient to give the impression of a fracture
.
The horse may or may not be pyrexic (fevered).
The limb may occasionally ooze serum.
In Ulcerative Lumphangitis, there may also be "cording" of the lymphatics and the formation of hard nodules and abscesses; occasionally a greenish, malodorous discharge is present. In the USA in particular, the disease may be characterised by multiple small, open sores.
and ultrasonography are often used to rule out the differential diagnoses of a fracture or tendinitis. Ultrasonography can also help to define boundaries of abscess pockets. Aspiration of a fluid sample for microbial culture is worth trying, but is often unrewarding.
s (typically potentiated sulphonamides or penicillin
and streptomycin
, but Doxycycline
may be the most effective). If possible, microbial culture and sensitivity testing
should be performed, so the most efficacious antibiotic can be chosen. However, it should be remembered that intracellular organisms such as Corynebacterium pseudotuberculosis will be susceptible to certain antibiotics in-vitro that are not effective for the specific organism in the horse. These horses are typically treated with Rifampin in addition to one of the previously mentioned antibiotics. In addition, anti-inflammatories are important, to reduce the swelling and pain of the inflammatory
response. NSAIDs are commonly used (Flunixin is the drug of choice, but phenylbutazone
may also be used). Corticosteroids are sometimes used in severe cases, but should be used with caution due to their potential to weaken the immune response to infection, and the possibility of inducing laminitis
.
In ulcerative lymphangitis, intravenous iodine salts may also be used; and abscesses should be poulticed or lanced. Ideally, an abscess should only be lanced after it has matured well and has an obvious soft spot, or the procedure should be guided with ultrasound to find the best site for drainage that avoids important structures.
"Physiotherapy" is also important, particularly maintaining movement by walking out and massage to improve lymphatic drainage and reduce the oedema.
Bandages may also be useful, as may cold hosing in the initial phase. A sweat bandage or poultice is often applied. An overly tight bandage should not be applied, as swelling may continue, decreasing circulation through the limb, and potentially causing a bandage-bow.
After-care often is advised to include consistent turnout and exercise.
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...
, particularly in a limb. It is most commonly a bacterial infection, although bacterial culture may be negative.
Often referred to as Fat/Big Leg Disease, it is sometimes known as Weed or Monday Morning Disease (not to be confused with the more common usage of MMD referring to Exertional Rhabdomyolysis/Azoturia
Equine Exertional Rhabdomyolysis
Equine exertional rhabdomyolysis is a syndrome that damages the muscle tissue in horses...
).
This article refers mainly to Sporadic Lymphangitis. Ulcerative lymphangitis is referred to in passing, as it is managed in a similar manner. Epizootic Lymphangitis
Epizootic lymphangitis
Epizootic lymphangitis is a contagious lymphangitis disease of horses and mules caused by caused by the fungus Histoplasma farciminosum. Cattle are also susceptible, but more resistant to the disease than equids.See also Glanders and Equine Lymphangitis....
is similar to glanders
Glanders
Glanders is an infectious disease that occurs primarily in horses, mules, and donkeys. It can be contracted by other animals such as dogs, cats and goats...
, but caused by the fungus Histoplasma farciminosum
Histoplasma
Histoplasma is a genus of dimorphic fungi commonly found in bird and bat fecal material. Histoplasma contains a few species, including—H. capsulatum—the causative agent of histoplasmosis; and Histoplasma capsulatum var. farciminosum , causing epizootic lymphangitis in horses...
.
Causes
Corynebacterium pseudotuberculosisCorynebacterium
Corynebacterium is a genus of Gram-positive rod-shaped bacteria. They are widely distributed in nature and are mostly innocuous. Some are useful in industrial settings such as C. glutamicum. Others can cause human disease. C...
has been cultured from some cases (particularly of ulcerative lymphangitis; however, in others, bacterial culture is negative. This may be because:
- a) The micro-organism responsible is difficult to culture (e.g. many MycoplasmaMycoplasmaMycoplasma refers to a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogenic in humans,...
species). - b) The organism has been effectively eliminated by the immune systemImmune systemAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
and the pathologyPathologyPathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
is due to an excessive immune response after the organism has been cleared. - c) The organism is not a bacterium but a fungusFungusA fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
and therefore very difficult to culture. - d) There is no causative organism and the disease has another cause.
Of these, a) is thought to be the most likely, and d) the most improbable.
Clinical signs
Extreme swelling of a limb, usually a hindlimb is seen, often as far proximally as the hockHock
The word hock may mean:* Hock , a type of wine* Hock , part of an animal's leg* Ham hock, a meat joint from the lower leg of a pig* To leave an item with a pawnbroker* Hans Henrich Hock, German historical linguist...
, or occasionally as far proximally as the stifle
Stifle joint
The stifle joint is a complex joint in the hind limbs of quadruped mammals such as the sheep, horse or dog. It is the equivalent joint to the human knee...
. In some cases swelling continues through the udder or sheath and along the subcutaneous abdominal veins. In the early stages, the swelling is primarily a "pitting oedema"; in other words, if pressed, a depression remains in the skin of the limb. The affected leg may reach twice or even three times its normal size, and may be very sensitive to the touch. In chronic cases, much of the swelling is firm, as scarring and fibrosis occur.
Lymphangitis is commonly associated with a wound, which may be very minor. This is a likely entrance for bacterial access to the lymph ducts.
The degree of lameness
Lameness (equine)
Lameness in horses and other equidae is a term used to refer to any number of conditions where the animal fails to travel in a regular and sound manner on all four feet...
is variable, but may be sufficient to give the impression of a fracture
Bone fracture
A bone fracture is a medical condition in which there is a break in the continuity of the bone...
.
The horse may or may not be pyrexic (fevered).
The limb may occasionally ooze serum.
In Ulcerative Lumphangitis, there may also be "cording" of the lymphatics and the formation of hard nodules and abscesses; occasionally a greenish, malodorous discharge is present. In the USA in particular, the disease may be characterised by multiple small, open sores.
Diagnostics
RadiographyRadiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
and ultrasonography are often used to rule out the differential diagnoses of a fracture or tendinitis. Ultrasonography can also help to define boundaries of abscess pockets. Aspiration of a fluid sample for microbial culture is worth trying, but is often unrewarding.
Treatment
The mainstays of treatment are the administration of broad-spectrum antibioticBroad-spectrum antibiotic
The term broad-spectrum antibiotic refers to an antibiotic that acts against a wide range of disease-causing bacteria. A broad-spectrum antibiotic acts against both Gram-positive and Gram-negative bacteria, in contrast to a narrow-spectrum antibiotic, which is effective against specific families of...
s (typically potentiated sulphonamides or penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
and streptomycin
Streptomycin
Streptomycin is an antibiotic drug, the first of a class of drugs called aminoglycosides to be discovered, and was the first antibiotic remedy for tuberculosis. It is derived from the actinobacterium Streptomyces griseus. Streptomycin is a bactericidal antibiotic. Streptomycin cannot be given...
, but Doxycycline
Doxycycline
Doxycycline INN is a member of the tetracycline antibiotics group, and is commonly used to treat a variety of infections. Doxycycline is a semisynthetic tetracycline invented and clinically developed in the early 1960s by Pfizer Inc. and marketed under the brand name Vibramycin. Vibramycin...
may be the most effective). If possible, microbial culture and sensitivity testing
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...
should be performed, so the most efficacious antibiotic can be chosen. However, it should be remembered that intracellular organisms such as Corynebacterium pseudotuberculosis will be susceptible to certain antibiotics in-vitro that are not effective for the specific organism in the horse. These horses are typically treated with Rifampin in addition to one of the previously mentioned antibiotics. In addition, anti-inflammatories are important, to reduce the swelling and pain of the inflammatory
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
response. NSAIDs are commonly used (Flunixin is the drug of choice, but phenylbutazone
Phenylbutazone
Phenylbutazone, often referred to as bute, is a non-steroidal anti-inflammatory drug for the short-term treatment of pain and fever in animals. In the United States, it is no longer approved for human use.-In humans:...
may also be used). Corticosteroids are sometimes used in severe cases, but should be used with caution due to their potential to weaken the immune response to infection, and the possibility of inducing laminitis
Laminitis
Laminitis is a disease that affects the feet of ungulates. It is best known in horses and cattle. Symptoms include lameness, and increased temperature in the hooves...
.
In ulcerative lymphangitis, intravenous iodine salts may also be used; and abscesses should be poulticed or lanced. Ideally, an abscess should only be lanced after it has matured well and has an obvious soft spot, or the procedure should be guided with ultrasound to find the best site for drainage that avoids important structures.
"Physiotherapy" is also important, particularly maintaining movement by walking out and massage to improve lymphatic drainage and reduce the oedema.
Bandages may also be useful, as may cold hosing in the initial phase. A sweat bandage or poultice is often applied. An overly tight bandage should not be applied, as swelling may continue, decreasing circulation through the limb, and potentially causing a bandage-bow.
After-care often is advised to include consistent turnout and exercise.