03.04.08

Lymphosarcoma in Guinea Pigs

Posted in Medical at 4:17 am by ACR&S

The second medical crisis that we have in the Sanctuary doesn’t actually involve one of our Sanctuary pigs. My partner DKMS technically owns three of our 17 guinea pigs; we call these our “pet” pigs, and he, not ACR&S, pays for all of their care and supplies. Two were adopted from ACR&S and one from the WI Guinea Pig Rescue.

Cinnamon was rescued by ACR&S in 2006 from a local animal shelter. We already had a ton of young, adoptable pigs; she was estimated to be about 3 years old and was pretty scraggly looking, with rough-textured fur; so we didn’t think she’d be very adoptable, but we couldn’t leave her in the shelter. DKMS was looking for another friend for his pig Stinky and decided to adopt her almost immediately.

Cinnamon is probably 5 years old now, and this summer she developed some stiffness in her legs and would occasionally limp a few steps. An X-ray found that she had arthritis, so she was placed on a daily dose of Metacam for pain. It helped tremendously and she stopped limping; she also loves her medicine and fights to hold onto the syringe!

On Feb 19, when giving Cinnamon her medication, we noticed that she looked a little “off”. She wasn’t moving as much or as normally as usual. I picked her up and found that she was COVERED in large, hard nodules - under her throat and jaw, and beneath each leg. They literally sprang up within 24 hours. These are the locations of the lymph nodes, so our first fear was a severe infection, and we rushed her to the vet for antibiotics. The vet placed her on antibiotics, but also did a biopsy to confirm, and a few days later we had the results: lymphosarcoma.

Background & Incidence

Lymphosarcoma is a malignant cancer involving lymphatic tissue or lymphocytes. The lymph nodes produce lymphocytes, which are white blood cells that help the body protect itself from infection. Lymphosarcoma occurs when the lymphocytes undergo a malignant change and begin to multiply, eventually crowding out healthy cells and creating tumors in the lymph nodes or other parts of the immune system. [1] Lymphomas and lymphosarcomas are much better understood in humans, and divided in to a huge number of sub-classifications based on location and type of affected cells. The same sub-classifications could probably be made in animals as well, but the disease(s) are not as well studied as in humans.

The small number of scientific articles I have found on lymphosarcoma don’t give much information, but it’s reported as very rare. One case report from 2000 notes that there were only 15 cases out of 5,000 animals in a 1991 report. [2] A 2003 paper states “neoplasias are practically non-existent in animals less than 1 year of age (Wagner and Manning 1976). In animals surviving three years the frequency of tumours is as high as 15% (Blumenthal and Rogers 1965). In some laboratory strains, animals older than three years, had tumour incidence ranging from 14.4% to 30% (Wagner and Manning 1976).” [3] Note the age of all of these source articles! And yet, these data contradict the owner anecdotes and some veterinary teaching information, both of which seem to indicate lymphosarcoma occurs fairly commonly, at least in older pigs.

Symptoms

Symptoms can vary, primarily by the location and type of lymphosarcoma. The most obvious symptom is usually swollen or enlarged lymph nodes, but owner anecdotes from medical threads on Guinea Lynx include include loose stools, loss of appetite, weight loss, difficulty breathing, and increased thirst or urination. [4] In some cases, owners went to the vet for one of these secondary symptoms, and the enlarged lymph nodes were only discovered during the physical examination by the vet.

Treatment & Prognosis

Treatments in dogs and cats (and humans) can include chemotherapy. In a guinea pig, chemotherapy is not as well studied; protocols are not established based on large-sample trials, and their small size makes it difficult since the drugs are designed for larger species. However, it has been done, and there are drug protocols for chemo available on Guinea Lynx.

Due to Cinnamon’s age, her vet did not feel that she would have a positive response to chemo. It causes nausea and GI upset, and she would be likely to go into GI stasis; it also works by suppressing immune function, making her more susceptible to opportunistic infections. He instead suggested that we keep her on pain medication, and also put her on Prednisone. Prednisone is said to shrink the tumors, or at least to slow their growth. As a steroid, it also reduces inflammation and pain.

Most of the treatment information on lymphosarcoma in guinea pigs comes from anecdotal reports of owners who have been through the disease with their pet. However, the prognosis is almost universally bad. One well-respected poster reports: “The average survival rate is quite variable, but I have yet to hear of one living longer than 6 weeks.” [5] Even when the pig is on Prednisone, a commonly reported complication is the tumors in the throat lymph nodes pressing on the trachea or esophagus, making eating and breathing difficult.

Given the information we have found, we do not expect Cinnamon to be with us very much longer. So now we are mostly focusing on making her comfortable and her last days enjoyable. She is still housed with her friend Stinky, who cuddles up with her and has been seen grooming her ears. She’s been a wonderful little girl and we’ll be very sorry to see her leave us.

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