Valley Fever

I had a client come in today and we were chatting after the appointment. She shared that her father in law, a “snowbird” from the mid-west, had just gone through surgery back home to remove a mass in his chest that turned out to be Valley Fever.

Unfortunately, this is not uncommon with people or animals. I’ve heard of dogs in other parts of the country having their leg amputated for “cancer” just to find Valley Fever on the biopsy or even being euthanized when they were diagnosed with “cancer” from the appearance of a chest x-ray. Here in Arizona we’re so hyperaware of the varied appearance of this disease that we test everything with unexplained clinical signs. More times than not it does in fact turn out to be Valley Fever.

The actual organism name for Valley Fever is Coccidioidomycosis or Cocci for short (I know! that’s why we call it Valley Fever). It is a fungal organism present in the soil and contagious to many species including primates, dogs and cats. In the United States this disease is only found in the southwest, from Southern California, to western Texas.

The organism is spread primarily through the air and spores are inhaled. With more chronic disease the spores can spread or disseminate throughout the body. It is not contagious from animal to animal, however since it is in the environment we will frequently see multiple animals in one household affected.

The most common presentation is with the primary or lung form. These pets usually present with coughing (or trouble breathing in cats), lethargy, fever, poor appetite and weight loss. The typical chest x-ray will show enlarged lymph nodes above the heart.

We also see with great frequency a disseminated form, most commonly a limping dog with a bone lesion. We also find granulomas or fungal masses in skin, central nervous system and in the abdomen. We’ve had dogs and cats present with signs of meningitis, generalized pain, weakness, seizures, occasionally even vomiting or diarrhea and weight loss. We’ve had dogs with fluid in the heart sac (pericardial effusion) or around the lungs (pleural effusion), and testicular masses. Sometimes these pets don’t have any specific sign we can point to, they just don’t feel well, maybe losing weight or just “off” in some way.

There is a blood test for Valley Fever called an antibody titer where we measure the animal’s immune response (antibodies) to the organism. A titer test uses serial dilutions to give us an approximate level of antibodies in the serum. The titer corresponds to the highest dilution that still shows a positive reading. The results are posted as 1:2 (being the lowest titer), then 1:4, 1:8, 1:16, 1:32, 1:64, 1:128 and finally 1:256.

We know that most people and animals living in the desert southwest for any time will have been exposed to the disease and now carry antibodies (a positive titer) against Valley Fever. So how do we know when a titer means that they are actively sick with the organism?

With a positive titer of 1:16 or higher this is an easy diagnosis. When we have a low or negative titer (1:2 or 1:4) it can be a little more difficult. If the animal has classical symptoms we will generally just treat. When their signs are non-specific or could also be explained by another disease we have to look further into the blood work. Frequently we will also find a high white blood cell count, primarily along the monocyte line and high globulins (one of the blood proteins). When even those tests come up negative and we find no other reason for the signs or symptoms we will often try a course of treatment to see if the patient responds.

Some patients will have symptoms of illness before their immune system has made enough antibodies to test positive. This is where a little of the “art” of diagnosis comes in. Even with our knowledge of this disease and diagnostic tools, there will still be those cases that end up being diagnosed by biopsy.

Treatment for Valley Fever is generally quite successful although it may take a long time. The medication we use most frequently is an antifungal called Fluconazole. This medication is a so-called “fungistatic” drug. This means that the medication can stop the growth or spread of the fungus, but doesn’t kill the organism. The patients own immune system is responsible for destroying the granuloma therefore it is very important that we support the immune system, feeding only high quality food and using nutritional supplements such as Immune Assist while they are being treated for Valley Fever. Some pets also require anti-inflammatory or pain medications or other supplementation to get through the most acute phase of the disease.

In general, most people see an improvement within the first month. Treatment lasts a minimum of 6 months with most pets being off drugs within a year. Sometimes we get a poor responder and they are on medications lifelong. The last scenario is rare.

So how do we know when to stop treating? We know we can’t rely on clinical signs alone. Pets will be feeling great long before their titers drop and blood work improves. We frequently see cases where owners discontinue medication too soon and the disease comes back often worse than before. So again, how do we know? We use a few general guidelines.

  1. A drop in the titer – ideally 1:2 but at least below 1:4
  2. Resolution of clinical signs
  3. White blood cell count and blood proteins are back to normal
  4. X-ray signs (if available) have resolved

Even after looking at all of this and using our best judgment, we will recommend monitoring the titer every 3-6 months for the next year to be sure it’s not trending higher again.
It’s always good to remember a little about this disease, especially if you or your family come and go to the desert southwest. Remember to discuss with your doctor or veterinarian your travel habits as this will hopefully help them in making a diagnosis.

What's Next

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  • 2

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