Lymphadenitis in Dogs
Lymphadenitis, the inflammation of lymph nodes in dogs, occurs when these nodes become inflamed due to an influx of white blood cells. Various types of white blood cells, including neutrophils, macrophages, and eosinophils, contribute to this inflammation by actively migrating to the affected nodes.
The lymph nodes act as filters, making them susceptible to exposure to infectious agents. Lymphadenitis typically occurs when infectious agents gain entry to a lymph node, leading to an infection. In response, the immune system increases white blood cell production to combat the infection. Common infectious agents responsible for lymphadenitis in dogs include fungi and mycobacteria, which are known to cause serious diseases in mammals.
While there is generally no genetic basis for lymphadenitis, rare cases of immunodeficiency, such as the familial susceptibility of certain basset hounds to mycobacteriosis, may contribute to its occurrence. Newborn puppies are particularly vulnerable to lymphadenitis due to their underdeveloped immune systems, making them more prone to infections.
Symptoms and Types
Symptoms of lymphadenitis are typically subtle and may not result in noticeable enlargement of the lymph nodes for those unfamiliar with veterinary medicine. However, your veterinarian will be able to identify firm nodes through palpation, which can be uncomfortable for the dog. Additionally, the dog may exhibit symptoms such as fever, loss of appetite (anorexia), or other signs of systemic infection. Bacterial infections can lead to abscess formation within the nodes, potentially causing them to open externally and form draining tracts. The severity of complications depends on the location of the infection and whether it affects surrounding organs.
Causes
Bacterial:
- Various pathogenic species have been sporadically reported to cause lymphadenitis.
- Common agents include Pasteurella, Bacteroides, and Fusobacterium spp.
- Certain bacteria like Yersinia pestis (causing bubonic plague) and Francisella tularensis (tularemia) have a particular affinity for lymph nodes, often leading to lymphadenitis.
- Bartonella vinsonii infection can induce granulomatous (nodular) lymphadenitis in dogs.
Fungi:
- Fungal infections often result in lymphadenitis as part of a systemic disease.
- Likely organisms comprise Blastomyces, Cryptococcus, Histoplasma, Coccidioides, and Sporothrix.
- Some other fungal agents have been occasionally reported.
Viruses:
- Numerous viral infections contribute to lymphoid hyperplasia.
- Mesenteric lymph nodes, located in the abdominal wall, are frequently affected.
Other:
- Protozoa such as Toxoplasma and Leishmania may cause lymphadenitis in dogs, although it may not be the most prominent clinical feature.
- Noninfectious causes, such as those associated with pulmonary or systemic eosinophilic diseases, often have unknown origins.
Risk Factors:
- Dogs with compromised immune function are more susceptible to infections and, consequently, to lymphadenitis.
Diagnosis
To diagnose lymphadenitis in your dog, it’s crucial to provide a detailed history of your pet’s health leading up to the appearance of symptoms. Your veterinarian will need to confirm that any palpable or visible mass is indeed a lymph node and not a tumor or another form of inflammation. Additionally, distinguishing lymph node enlargement from other causes or cell proliferation within the nodes, such as cancer, can be challenging based solely on clinical examination.
To ensure an accurate diagnosis, your veterinarian may order a complete blood count and urinalysis to detect signs of bacterial and fungal infections. If the swollen nodes are located in the chest or abdomen, diagnostic procedures may include X-ray and ultrasound imaging to assess the extent of the condition. A fine-needle aspiration of the affected lymph nodes might also be performed to collect samples of fluid and tissue for analysis, enabling a thorough examination of the internal composition of the lymph nodes.
Treatment
As lymphadenitis represents a lesion rather than a distinct disease, there isn’t a standardized set of therapeutic guidelines applicable to all cases. Treatment approaches depend on the nature of the inflammation and the underlying cause. Your veterinarian will design a treatment plan based on the collected evidence and findings. Antibiotics may be recommended; however, the selection of medications will be determined by the specific findings and causative agent identified during diagnosis.
Living and Management
It’s essential to adhere to your veterinarian’s treatment recommendations for your dog’s lymphadenitis. Scheduled follow-up examinations will be necessary to ensure complete elimination of the infection. Certain organisms responsible for lymphadenitis can be zoonotic, meaning they can be transmitted to humans and other species. If this is the case, your veterinarian will provide you with home treatment guidelines to help protect yourself, your family, and other pets from potential infection.
