What is Bacterial Infection (Actinomycosis)?
Actinomyces is an anaerobic, gram-positive bacteria that lives in the mouth and nasal passages of many animals. It has a rod shape and often forms fungus-like branches or hyphae. Some species can cause an actinomycosis infection. This is more common in cattle, but it is also found in dogs, and, rarely, in humans. Actinomycosis has a higher incidence in large-breed outdoor dogs, especially hunting dogs. It is an opportunistic infection that takes advantage of a cut or wound which allows bacteria to penetrate the skin and grow unchecked in an anaerobic environment. Infections are commonly subcutaneous (in the deep layers of the skin, below the dermis), and are often associated with contaminating grass particles that find their way into a cut. Particles that are inhaled or ingested can also cause pneumonia and gastrointestinal lesions. In some cases, the bacteria can spread from the original site causing systemic infection including CNS disease or meningitis. The infection progresses slowly, often developing fibrous mass-like abscesses which are sometimes mistaken for cancerous neoplasm. Cervicofacial infections (in the head or neck area) may spread into the mandibular bone causing teeth to fall out and making it difficult for a dog to eat or breathe. Treatment of actinomycosis is difficult because the anaerobic bacteria penetrate so deeply and surgery is often necessary to remove the infected tissue. Oral antibiotics will need to be taken for a number of weeks to eliminate all the bacteria. Very severe cases, especially those that involve the bone, may be difficult to treat.
Actinomyces are an anaerobic species of bacteria that can cause infection under the skin or elsewhere in the body. They are found normally in the oral cavities and nasal passages of dogs, but cuts or tiny grass particles can allow them to penetrate more deeply and proliferate to form an abscess. Veterinarians call this actinomycosis.
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Symptoms of Bacterial Infection (Actinomycosis) in Dogs
Symptoms can be quite varied depending on the infection site. Take your dog to see a veterinarian immediately if you notice any of the following signs.
- Subcutaneous sores and abscesses
- Drainage tracts close to the site of infection
- Sores and abscesses in the mouth, face, or neck
- Serosanguinous drainage (containing blood and plasma)
- Pus drainage that contains sulphur-like grains
- Pain or swelling in the jaw
- Weight loss
- Difficult or rapid breathing
- Pyothorax (infection of the chest cavity)
- Orbital infection
- Urinary infection (rare)
- Changes in behavior and consciousness
There are many different types of actinomyces bacteria. These are three species commonly identified in canine infections. Actinomyces bovis often causes infection from wound contamination, especially cuts in the mouth. It is more commonly associated with lumpy jaw in cattle, but it can cause the same symptoms in dogs. Actinomyces hordeovulneris is often associated with penetrating grass awns (usually of the species Horedum). It can cause internal abscesses in the lungs, liver and spleen as well as septic arthritis and systemic infection. Actinomyces viscosus causes subcutaneous infection from a wound as well as pyothorax and pneumonia.
Causes of Bacterial Infection (Actinomycosis) in Dogs
Actinomycosis is an opportunistic infection, so it is commonly associated another factor that makes it easier for the bacteria to proliferate.
- Cut or wound (especially in the mouth)
- Penetration or swallowing of a foreign body
- Exposure to long grass
- Chronic periodontal disease
- Poor dental hygiene
- Lung cancer
- Prior surgery
- Concurrent ear or eye infection
- Spending time outside
- Higher incidence among large breed hunting dogs
Diagnosis of Bacterial Infection (Actinomycosis) in Dogs
Your dog’s symptoms will help the veterinarian diagnose actinomycosis. Subcutaneous infection with orange colored granular discharge is a typical sign. Abnormal lung sounds will usually be noticeable with a chest infection. Lameness, jaw pain, exophthalmos, or swelling can also show which areas are affected. Dogs often have fever with systemic infection.
A definitive diagnosis is made by taking a culture of the infected tissue. A biopsy may be necessary for deep or internal infections. Rod-shaped gram-positive bacteria are visible upon examination of a stained culture. X-rays may be needed to diagnose fibrous mass-like lesions. This can help to find the source of internal infection and determine how far the condition has progressed. Radiographs of the head and neck area are common, as well as of the lungs or abdomen. These can also be used to eliminate some other causes and diagnose any concurrent diseases like cancer. Since some actinomycosis abscesses can resemble cancer, a biopsy may be necessary to tell the two apart.
A history of your dog’s activities and recent injuries can help the vet determine the likelihood that actinomycosis is the problem. Outdoor activities, especially in wilderness areas are more conducive to actinomycosis. A recent wound or surgery can also increase the risk.
Treatment of Bacterial Infection (Actinomycosis) in Dogs
Actinomycosis is treated with a systemic antibiotic for a minimum of four to six weeks. Beta-lactam penicillin-type antibiotics are frequently prescribed, but other antibiotics have also proved effective and may be recommended by your vet. Oxygen might be needed for dogs with serious pneumonia.
It can be difficult for any antibiotic to penetrate deep infections and abscesses, so in many cases the veterinarian will also recommend surgical removal of infected tissue. With subcutaneous infection this will be relatively minor. The veterinarian will cut away the skin tissue under anesthetic to allow drainage. More invasive surgery could be needed to remove infected masses from the abdomen, liver or spleen. Infections that have progressed into the bone are rarely treated successfully due to the difficulty with penetrating and removing the infected tissue.
Recovery of Bacterial Infection (Actinomycosis) in Dogs
Recovery will depend on the severity of your dog’s condition. Localized infections usually respond to antibiotic treatment. Infections of the chest cavity can also often be treated if an antibiotic is prescribed early in the progression of the disease. Severe systemic infections that have been developing for a while can be harder to treat. Your dog’s chances will be evaluated by a veterinarian upon diagnosis.
In order to prevent the disease, avoid grassy wilderness as much as possible, check your dog’s mouth frequently for cuts and scrapes, and clean and sterilize any wounds or sores frequently. Seek treatment immediately if you notice any signs of infection. Actinomycosis develops slowly, so treating the condition right away will give your dog a better chance of recovery.
Bacterial Infection (Actinomycosis) Questions and Advice from Veterinary Professionals
I have a 7 year 9 month old hunting Decker terrier. Presenting with slight wt loss, shaking, history of hot spots occasionally in past (assumed to be from a grass allergy, hot spots would arise after being in the field) then four months ago new onset of small subcutaneous cysts that drain plasma/bloody but clear, no pus and a long history of enlarged cervical lymph nodes. These grass allergy were treated with steroid shots and oral cephsporin. My vet had enough concern we did not have the right diagnose and treatment he recently referred us to to an allergist veteranian who found three other slightly enlarged lymph nodes. General anesthesia was administered, the cervical lymph was aspirated and biopsies were done on the other three lymph nodes. Slides and cultures were done and over the last two weeks, they have been shared with several sources to get a diagnosis. Yesterday, we finally got a diagnosis of Actinomycosis. Penicillin has been ordered for 4-6 weeks, treatment starts on Monday, I will be giving the injection. I have a whole collection of documented photos of the effected area I could share.
I would be very interested to see the photos. My best friend's beloved dog died of what could be actinomycosis with serious wounds ( absess like) in her left hind leg. Her immune system was compromised and she died suddenly after the wounds were discovered. She had several of the symptoms described but definitely not all. Results of the biopsy are still pending but it was painful to lose such a beautiful, sweet dog whom I loved as if she was my own. Thank you.
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Want to know what the lump is on my dogs lower jaw we took her to vet and they gave medicine and it started to work went back after 2 weeks and they gave us more medicine but it was different and we have had her on it for 2 weeks but has not helped got worse today we don’t want to lose her what should we do but I was reading and t sounds like this but she has not had any symptoms but today she has barely ate and I have been noticing her panting more
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Dog w/some neur.damage. recurring utis. Incontinent. In jan he became very ill with some kind of infection. He was on 2 wKS of Clavamox. Then shortly after 4 wKS of zeniquin. That ended Feb 20. March 12 he was lethargic, no appetite. He died that night.ER vet said heart rate 250,hypoglycemic, high wbc,rbc,Hct,hgb,lymps,monos,neut,retics,bun/urea,phos,glob,potassium. Low eos,glu,hc03,ph,tc02.I know it was a severe bacteria infection, just don't know what caused it. My concern is that a uti spread to his kidneys and caused it. ER vet asked us about manual expressing. He was concerned about it just being overflow. My usual vet said expressing is only for dogs that can't pee on their own. I'm reading now that just because I saw urine in his belly band doesn't mean he was going. It could have been overflow and that could've developed into a uti and spread to his kidneys. I just want to know if this is a possibility based on his bloodwork? I have another dog with the same issues that I am trying to protect. My usual vet dismissed this, but I think he's afraid that I am blaming him. I am not. What else could have it been?
Further to my previous answer. Dogs with belly bands have a high incidence rate of urinary tract infections and infections can spread from the lower urinary tract up the ureters to the kidneys. It would have been best to have had a necropsy performed and a sample taken from Will’s kidney for analysis. There is always a risk of urinary infections with belly bands and infections if not managed or treated can spread; it is important to keep your dog’s belly band clean and to clean around the prepuce to prevent urine scald and infections. Regular urinary tests will help detect any infection that has formed. Regards Dr Callum Turner DVM
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