|Classification and external resources|
Histopathological changes in a case of coccidioidomycosis of the lung showing a large fibrocaseous nodule.
Coccidioidomycosis (//, kok-sid-ee-oy-doh-my-KOH-sis), commonly known as cocci, "valley fever", as well as "California fever", "desert rheumatism", and "San Joaquin Valley fever", is a mammalian fungal disease caused by Coccidioides immitis or Coccidioides posadasii. It is endemic in certain parts of Arizona, California, Nevada, New Mexico, Texas, Utah and northern Mexico.
C. immitis resides in the soil in certain parts of the southwestern United States, most notably in California and Arizona. It is also prevalent in northern Mexico, and parts of Central and South America. It is dormant during long dry spells, then develops as a mold with long filaments that break off into airborne spores when the rains come. The spores, known as arthroconidia, are swept into the air by disruption of the soil, such as during construction, farming, or an earthquake.
Infection is caused by inhalation of the particles. The disease is not transmitted from person to person. The infection ordinarily resolves leaving the patient with a specific immunity to re-infection. However, in some cases the infection may manifest itself repeatedly or permanently over the life of the host. C. immitis is a dimorphic saprophytic organism that grows as a mycelium in the soil and produces a spherule form in the host organism.
Signs and symptoms
Symptomatic infection (40% of cases) usually presents as an influenza-like illness with fever, cough, headaches, rash, muscle pain, and joint pain. The rash is maculopapular. Erythema nodosum on lower extremities, and erythema multiforme in necklace-like fashion can occur predominantly in women.
Some patients fail to recover and develop chronic pulmonary infection or widespread disseminated infection (affecting meninges, soft tissues, joints, and bone). Severe pulmonary disease may develop in HIV-infected persons.
In order of decreasing risk, people of Filipino, African, Native American, Hispanic, and Asian descent are more susceptible to the disseminated form of the disease than other ethnic backgrounds. Immunocompromised individuals are more susceptible to the disease.
After Coccidioides infection, Coccidioidomycosis begins with Valley fever, which is its initial acute form. If left untreated, it can progress to chronic and then to disseminated Coccidioidomycosis. Therefore, Coccidioidomycosis may be divided into the following types:
Most of the infected humans do not experience any symptoms or consequences. Serious complications may occur in patients with weakened immune systems, including severe pneumonia, lung nodules, and possible disseminated form, where the infection spreads throughout the body. The disseminated form of Coccidioidomycosis can devastate the body, causing skin ulcers, abscesses, bone lesions, swollen joints with severe pain, heart inflammation, urinary tract problems, and meningitis, which can lead to death.
In soil (and also in agar media), coccidioides exists in filament form. It forms hyphae in both horizontal and vertical directions. With time, cells within hyphae degenerate to form alternating barrel-shaped cells (arthroconidia). Arthroconidia are light-weight and carried by air currents. They can be easily inhaled without the person knowing. On arriving in alveoli, they enlarge in size and internal septations are developed. This structure is called a spherule. Septations develop and form endospores. Rupture of spherules release these endospores, which in turn repeat the cycle and spread the infection locally. Nodules can form in lungs surrounding these spherules. When they rupture, they release their contents into bronchi, forming thin-walled cavities. These cavities can result in symptoms like characteristic chest pain, hemoptysis and persistent cough. In immunocompromised individuals, infection spreads through blood.
The fungal infection can be demonstrated by microscopic detection of diagnostic cells in body fluids, exudates, sputum and biopsy-tissue by methods of Papanicolaou or Gomori's methenamine silver staining. These stains can demonstrate spherules and surrounding inflammation.
With specific nucleotide primers C.immitis DNA can be amplified by polymerase chain reaction (PCR). It can also be detected in culture by morphological identification or by using molecular probes that hybridize with C.immitis RNA. C. immitis and C. posadasii cannot be distinguished on cytology or by symptoms; but only by DNA PCR.
An indirect demonstration of fungal infection can be achieved also by serologic analysis detecting fungal antigen or host IgM or IgG antibody produced against the fungus. The available tests include the tube-precipitin (TP) assays, complement fixation assays, and enzyme immunoassays. TP antibody is not found in cerebrospinal fluid (CSF). TP antibody is specific and is used as confirmatory test, while ELISA is sensitive and thus used for screening.
Chest X-Ray usually shows nodules in upper lobes of the lung and usually less than 4 cm in diameter. They rarely calcify.
Less than 5% of infected, usually immunocompromised, humans develop a disease, and some mild asymptomatic cases often do not require any treatment. Some patients with severe symptoms may warrant anti-fungal therapy. There is a lack of prospective studies that examine optimal anti-fungal therapy for coccidioidomycosis.
On the whole, oral fluconazole and intravenous amphotericin B are used in progressive or disseminated disease, or in immunocompromised individuals. Alternatively, itraconazole or ketoconazole may be used for milder disease. Fluconazole is preferred drug for coccidioidal meningitis, due to its penetration into CSF. Intrathecal or intraventricular amphotericin B therapy is used if infection persists after fluconazole treatment. Itraconazole is used for cases that involve treatment of infected patient's bones and joints. Posaconazole and voriconazole have also been used to treat coccidioidomycosis.
Currently there are no completely effective preventive measures available for people who live or travel through Valley fever endemic areas. It is recommended to avoid airborne dust or dirt, though this is not a guaranteed manner of prevention. People in certain occupations may be advised to wear face masks.
In 1998-2011, there were 111,117 cases of Coccidioidomycosis in the U.S. that were logged into the National Notifiable Diseases Surveillance System (NNDSS). Since in many states Coccidioidomycosis reporting is not mandatory, the actual numbers can be higher. The U.S. national public health institute Centers for Disease Control and Prevention (CDC) called the disease a "silent epidemic" and acknowledged that there is no proven anticoccidioidal vaccine available.
Raising both surveillance and awareness of the disease while medical researchers are developing a human vaccine can positively contribute towards prevention efforts. Research demonstrates that patients from endemic areas who are aware of the disease are most likely to request diagnostic testing for Coccidioidomycosis. Presently, Meridian Bioscience manufactures the so-called EIA test to diagnose the Valley fever, which however is known for producing a fair quantity of false positives. There were reports that Nielsen Biosciences created a skin test to diagnose this systemic disease that on the onset masquerades itself with respiratory illness symptoms. Currently, recommended prevention measures can include type-of-exposure-based respirator protection for persons engaged in agriculture, construction and others working outside in the endemic areas. Dust control measures such as planting grass and wetting the soil, and also limiting exposure to dust storms are advisable for residential areas in endemic regions.
Coccidioidomycosis is confined to the western hemisphere between 40° N and 40° S. Dry soil, especially in the Lower Sonoran Life Zone, is supportive of the pathogenic fungi growth. In harmony with mycelium life cycle, incidence increases with periods of dryness after a rainy season; this phenomenon, termed "grow and blow", refers to growth of the fungus in wet weather, producing spores which are spread by the wind during succeeding dry weather.
Besides humans, dogs, and cats, the fungus can be shown to infect most mammals, even if they do not get sick from it very often. Species in which Valley fever has been found include livestock such as cattle and horses; llamas; marine mammals, including sea otter; zoo animals such as monkeys and apes, kangaroos, tigers, etc.; and wildlife endemic to the geographic area such as cougar, skunk, and javelina.
California state prisons, beginning in 1919, have been particularly affected by Coccidioidomycosis. In 2005 and 2006, the Pleasant Valley State Prison near Coalinga and Avenal State Prison near Avenal on the western side of the San Joaquin Valley had the highest incidence in 2005, of at least 3,000 per 100,000. The receiver appointed in Plata v. Schwarzenegger issued an order in May 2013 requiring relocation of vulnerable populations in those prisons.
Incidence varies widely across the west and southwest. In Arizona, for instance, in 2007, there were 3,450 cases in Maricopa County, which in 2007 had an estimated population of 3,880,181 for an incidence of approximately 1 in 1,125. In contrast, though southern New Mexico is considered an endemic region, there were 35 cases in the entire state in 2008, and 23 in 2007, in a region that had an estimated 2008 population of 1,984,356 for an incidence of approximately 1 in 56,695.
There was an outbreak in the summer of 2001 in Colorado, away from where the disease was considered endemic. A group of archeologists visited Dinosaur National Monument, and eight members of the crew, along with two National Park Service workers were diagnosed with Valley fever.
Infection rates vary greatly by county, and although population density is important, so are other factors that have not been proven yet. Greater construction activity may disturb spores in the soil. In addition, the effect of altitude on fungi growth and morphology has not been studied, and altitude can range from sea level to 10,000 feet or higher across California, Arizona, Texas and New Mexico.
In California from 2000 to 2007, there were 16,970 reported cases (5.9 per 100,000 people) and 752 deaths (0.26 per 100,000 people) with the highest incidence in the San Joaquin Valley (44.1 per 100,000). Following the Northridge Earthquake, there was a sudden increase of cases in the areas affected by the quake, at a pace of over 10 times baseline.
The CDC reported 22,401 new cases of Coccidioidomycosis infections across the U.S. in 2011. The 2011 figures were almost ten times higher than those reported in 1998.
The first case of what was later named Coccidioidomycosis was described in 1892 in Buenos Aires by Alejandro Posadas, a medical intern at the Hospital de Clínicas "José de San Martín". Posados established an infectious character of the disease after being able to transfer it in laboratory conditions to lab animals. In the U.S., E. Rixford, a physician from a San Francisco hospital, and T. C. Gilchrist, a pathologist at Johns Hopkins Medical School, became early pioneers of clinical studies of the infection. They decided that the causative organism was a Coccidia-type protozoan and named it Coccidioides immitis (resembling Coccidia, not mild).
During the next several decades it became clear that the etiological agent of the disease that was at first called Coccidioides infection and later Coccidioidomycosis was a fungal pathogen, and Coccidioidomycosis was also distinguished from Histoplasmosis and Blastomycosis. Further, C. immitis was identified as the culprit of respiratory disorders previously called San Joaquin fever, Desert fever, and Valley fever, and a serum precipitin test was developed by Charles E. Smith that was able to detect an acute form of the infection. In retrospect, Smith played a major role in both medical research and raising awareness about Coccidioidomycosis, especially when he became dean of the School of Public Health at the University of California at Berkeley in 1951.
C. immitis was considered by the United States during the 1950s and 1960s as a potential biological weapon. The explored strain was designated with the military symbol OC, and initial expectations were for its employment as a human incapacitant. Medical research suggested that OC might have had some lethal effects on the populace, and C. immitis started to be classified by the authorities as a threat to public health. However, C. immitis was never weaponized, and most of the military research in the mid-1960s was concentrated on developing a human vaccine. Currently, it is not on the U.S. Department of Health and Human Services (HHS) or Centers for Disease Control and Prevention's list of select agents and toxins.
- Coccidioides immitis
- Coccidioides posadasii
- Medical geology
- List of cutaneous conditions
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|Wikimedia Commons has media related to Coccidioidomycosis.|
- U.S. Centers for Disease Control and Prevention page on Coccidioidomycosis
- Medline Plus Entry for Coccidioidomycosis
- Radiology of Lesions in Valley Fever