Coccidioidomycosis (球孢子菌病)

Coccidioidomycosis (头球孢子菌病)， [pronounced: kok-siddee-oydo-my-cohssiss](commonly
known as "Valley fever", as well as "California fever", "Desert rheumatism",
and "San Joaquin Valley fever") is a fungal disease caused by Coccidioides
immitis or C. posadasii. It is endemic in certain parts of Arizona, California,
 Nevada, New Mexico, Texas, Utah and northwestern Mexico.

C. immitis resides in the soil in certain parts of the southwestern United
States, 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.
C. immitis is a dimorphic saprophytic organism that grows as a mycelium in
the soil and produces a spherule form in the host organism.

Presentation

The disease is usually mild, with flu-like symptoms and rashes. The Mayo
Clinic estimates that half the population in some affected areas have suffered
from the disease. On occasion, those particularly susceptible may develop
a serious or even fatal illness. Serious complications include severe pneumonia,
 lung nodules, and disseminated disease, where the fungus spreads throughout
the body. The disseminated form of valley fever can devastate the body,
causing skin ulcers, abscesses, bone lesions, severe joint pain, heart inflammation,
 urinary tract problems, meningitis, and often death. In order of decreasing
risk, people of Filipino, African, Native American, Hispanic, and Asian
descent are susceptible to the disseminated form of the disease.  Men and
pregnant women, and people with weakened immune systems (as from AIDS) are
more susceptible than non-pregnant women.

It has been known to infect humans, cattle, deer, dogs, elk, fish, mules,
livestock, apes, kangaroos, wallabies, tigers, bears, badgers, otters and
marine mammals.

Symptomatic infection (40% of cases) usually presents as an influenza-like
illness with fever, cough, headaches, rash, and myalgia (muscle pain). 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.

An additional risk is that health care providers who are unfamiliar with
it or are unaware that the patient has been exposed to it may misdiagnose
it as cancer and subject the patient to unnecessary surgery.

Types

Coccidioidomycosis may be divided into the following types:

        Primary pulmonary coccidioidomycosis
        Disseminated coccidioidomycosis
        Primary cutaneous coccidioidomycosis

California state prisons, as far back as 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.

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. 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).

C. immitis was investigated by the United States during the 1950s and 1960s
as a potential biological weapon.[citation needed] The Cash strain received
the military symbol OC, and original hopes were for its use as an incapacitant.
 As medical epidemiology later made clear, OC would have lethal effects
on several segments of the population, so it was later considered a lethal
agent. It was never standardized, and beyond a few field trials, it was
never weaponized. Most military work on OC was on vaccines by the mid-1960s.
It is still on the CDC's list of select agents however.

Diagnostic test

The fungal infection can be demonstrated by microscopic detection of diagnostic
cells in body fluids, exudates, sputum and biopsy-tissue. With specific
nucleotide primers C.immitis DNA can be amplified by PCR. It can also be
detected in culture by morphological identification or by using molecular
probes that hybridize with C.immitis RNA. An indirect demonstration of fungal
infection can be achieved also by serologic analysis detecting fungal antigen
or host antibody produced against the fungus.

Treatment

There are no published prospective studies that examine optimal antifungal
therapy for coccidioidomycosis. Mild cases often do not require treatment.
Oral Fluconazole and intravenous Amphotericin B are used in progressive
or disseminated disease, or in which patients are immunocompromised. Alternatively,
 itraconazole or ketoconazole may be used. Posaconazole and voriconazole
have also been used.