What is Coccidioidomycosis (Coccidioidomycosis)?
The fungus Coccidioides, which transforms into different forms, causes a disease called coccidioidomycosis, also known as San Joaquin Valley fever. This disease is commonly found in dry regions of the Western Hemisphere. The fungus Coccidioides was first identified by a medical intern in 1892 and was later given the name Coccidioides immitis. The effects of coccidioidomycosis can vary widely. Some people might not show any symptoms, while others may suffer from a severe disease that can even lead to death.
What Causes Coccidioidomycosis (Coccidioidomycosis)?
Coccidioides is a type of fungus that can exist in two states: mycelia or spherules. Both of these forms don’t reproduce sexually and their closer relatives include Histoplasma capsulated or Blastomyces dermatitidis according to molecular studies.
Two types of Coccidioides are recognized: C. immitis, which lives in California, and Coccidoides posadasii. This second type is found not only in other US states, but also in different parts of the world. Both types have the same clinical symptoms and reactions to treatments and can only be told apart by molecular methods.
Thus, in clinical labs, they’re usually not identified on a species level. These fungi prefer dry desert conditions with high salt content. They grow in soil, and in special lab settings, as mycelia or filamentous forms.
The infectious particles of Coccidioides, called arthroconidia, are breathed in and get deposited in the lungs. There, they transform into spherules filled with endospores. These spherules can burst in tissues releasing these endospores, which can intensify the infection.
Coccidioides species grows well on most fungal or bacterial media after about five to seven days of incubation. Quite often, the colonies appear white, but this is not indicative as the fungus is highly infectious at this stage. Therefore, lab workers should be informed when Coccidioides species are suspected to prevent potential outbreaks.
Risk Factors and Frequency for Coccidioidomycosis (Coccidioidomycosis)
Coccidioides, a type of fungus, is native to certain areas of the United States, including California, Arizona, Utah, Nevada, and New Mexico. The disease it causes, Coccidioidomycosis, also known as Valley Fever, is a condition that must be reported to health authorities. Recently, Arizona has seen a rise in cases of this disease, but the reason for this increase is not known. In 2011, the rate of Valley Fever was about 43 cases for every 100,000 people, with the highest rate among those aged 60 to 79 years— around 69 cases per 100,000 people. In some locations, this disease could be responsible for 15% to even 30% of pneumonia cases that were not caught in a hospital. Interestingly, the infectious particles can travel in the wind, which means the disease can affect people living far from where the fungus is typically found.
Signs and Symptoms of Coccidioidomycosis (Coccidioidomycosis)
Most of the time, infections don’t have symptoms (60% of cases). But when there are symptoms, they’re often mistaken for a type of pneumonia caught from being out in day-to-day life. The symptoms usually start to show seven to 21 days after being exposed to the cause of the infection. Common symptoms include fever, coughing, difficulty breathing, and chest pain. Depending on the size of the infection, the symptoms may start suddenly or build up over time. It’s also common to have a headache, lose weight and develop a rash. The rash usually isn’t very noticeable, disappears quickly, comes on early in the disease, and for that reason, it’s often overlooked. Certain kinds of skin redness (erythema nodosum or erythema multiforme) affect women more often.
Other common symptoms include joint pain that moves around the body, particularly in the knees and ankles. A combination of these symptoms – fever, skin redness, and joint pain – is sometimes referred to as ‘desert rheumatism.’ Patients will often have higher than usual levels of certain substances in their blood (erythrocyte sedimentation rate and eosinophils). Chest x-ray may show areas of cloudiness on one side only. If the disease has spread beyond the chest, patients may have enlarged lymph nodes near the windpipe. Lung cavities are seen in only about 8% of adult patients, but are more common in children.
In some patients, the disease can cause lung nodules and cavities early on and a disease causing lung cavities and fibrosis (scarring) in the long term. These cavities are usually on the periphery, solitary, and get a thin wall over time. If detected early, surgery to remove the cavity and stopping the lung leak is the best treatment. In a third of the patients, the disease can also affect the pleura, the membrane that covers the lung.
People with a weakened immune system, pregnant ladies, and those of African and Filipino descent, are often more prone to a spread of this disease beyond the lungs. Skin lesions are common in these cases. There may be no cloudiness on chest x-ray in such patients. Bone infection, most commonly in the spine, which mimics bone infection caused by the bacterium Staphylococcus aureus, is common. It can also present with a collection of pus in the muscles of the back and accumulation of pus around the spinal cord. Joint involvement is frequent, with knee joints most frequently affected. 90% of these cases can show involvement of the brain and its protective coverings. If left untreated, brain involvement can be life-threatening. A predominance of a type of white blood cell, Eosinophil, is found in the fluid that protects the brain and spinal cord. The base of the brain is often affected and there can be a build-up of fluid inside the brain, a condition called hydrocephalus.
Testing for Coccidioidomycosis (Coccidioidomycosis)
Identifying the presence of ‘Coccidioides’ organisms in a patient can be an absolute confirmation of coccidioidal infection. This method of diagnosis is mainly used in patients with complex lung or widespread conditions. Notably, the collection of sputum does not have a risk of disease spread.
The most common way of diagnosing primary coccidial infections is by performing a blood test. In many cases, patients may not produce sputum, making fungal cultures unattainable. Also, tests on cerebrospinal fluid (the fluid in your brain and spine) often do not show any presence of coccidiodomycosis, a fungal disease. Even a very slight reaction in these tests should not be ignored. Importantly, a negative result on these tests does not mean the infection is absent, so the test may need to be run again after two months.
One test, known as the IgM test, detects an antibody called tube precipitin, which is found in about 90% of patients in the first three weeks after exposure to the fungus. However, these antibodies are only found in around 5% of patients seven months after exposure. Another type of antibody called complement-fixing (CF) antibodies can also be identified in other body fluids, making them particularly useful in diagnosing coccidial meningitis, an infection of the brain and spinal cord.
An enzyme immunoassay (EIA) test can also be performed to detect Coccidiosis IgM and IgG antibodies. However, these results have to be confirmed with other tests because the EIA test uses different signals for measurement. Although the EIA test is highly sensitive, it can provide false-positive results more often than other tests.
The antibodies found by the original tests, tube precipitin, and CF, can also be identified by alternative procedures with the same sensitivity. However, these alternative tests use different signals to measure the antibodies.
Generally, the serological tests, which detect antibodies in your blood, are likely to be positive if the person has been exposed to Coccidioides species. In a study involving 41 patients confirmed with coccidioidomycosis, over half the patients had a positive CF result, 70% had a positive immunodiffusion complement-fixing (IDCF) result, and 81% had a positive EIA result. However, in 15% of the patients, all these tests were negative.
Polymerase chain reaction (PCR) tests, which can directly detect coccidioidomycosis DNA in patient samples, are not commercially available, but when undertaken in research environments they’ve proven high specificity and accuracy. Additionally, certain methods can identify a specific RNA sequence in lab-grown fungus.
Latex tests, despite their simplicity and wide availability, have lower success rates and often provide false positives. Antigenemia and antigenuria (presence of antigens in the blood and urine respectively) can occur with early or long-term Coccidioides infections. Taking a PCR test can be useful when diagnosing meningitis, as the cerebrospinal fluid cultures often come back negative. In a study of immunosuppressed patients with coccidioidomycosis, most of them had a positive urine test for the antigen.
Treatment Options for Coccidioidomycosis (Coccidioidomycosis)
In 2016, the Infectious Disease Society of America published treatment guidelines for a disease called coccidioidomycosis. This disease varies widely in how it presents, from a mild respiratory illness to more serious lung disease that can look like nodules, cavities, or fibrocavitary disease. In severe cases, especially in people with weak immune systems, coccidioidomycosis can spread throughout the body. The best treatment is a drug called Diflucan, taken daily in doses between 400 mg and 1200 mg. Another option is Itraconazole, but it can interact with other medications.
When coccidioidomycosis affects the lungs, it should be treated if it is severe. Reasons to treat it include significant weight loss, persistent intense night sweats, symptoms lasting longer than three weeks, extensive lung involvement, inability to work due to symptoms, or patients being over 55 years old. Usually, three months of treatment with a group of drugs known as oral azole is sufficient.
If there are lung nodules that don’t cause symptoms, they should be monitored with imaging scans, and if they grow or there’s a risk of cancer, surgery should be considered. Cavities in the lung that don’t cause symptoms should also be monitored, and treated if needed. Medications known as azoles, such as fluconazole, are recommended for fibrocavitary disease.
For certain types of pneumonia caused by the disease, a drug called Amphotericin B might be used. If the disease affects the coverings of the brain and spinal cord (meningitis), drugs like Fluconazole are preferred, which is taken for life.
Patients with HIV and coccidioidomycosis need to be treated if their immune system is weak, but those with a stable immune system can safely stop therapy. For severe infections, a combination of drugs is recommended.
What else can Coccidioidomycosis (Coccidioidomycosis) be?
When a person is having respiratory problems, the list of potential medical issues can be quite diverse. Some possible conditions that doctors keep in mind are:
- Acute Respiratory Distress Syndrome (severe shortness of breath)
- Blastomycosis (a fungal infection in the lungs)
- Enteropathic Arthropathies (joint diseases related to intestinal conditions)
- Eosinophilic Pneumonia (a rare lung disease caused by white blood cells)
- Granuloma (inflammatory nodules often found in the lungs)
- Histoplasmosis (another type of fungal infection in the lungs)
- Lung Abscess (a pus-filled cavity in the lung)
- Lung Cancer
- Lymphoma (cancer of the lymphatic system that can affect the lungs)
- Myelophthisic Anemia (a condition where bone marrow is replaced by other substance)
It’s critical for healthcare providers to thoroughly consider these conditions and carry out the necessary tests to make a correct diagnosis.
