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By Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, Section Editor, Updates; is Associate Editor for Infectious Disease Alert.
Preparing for Coccidioides Laboratory Exposure
Source: Stevens DA, et al. Expert Opinion: What to do when there is a coccidioides exposure in a laboratory. Clin Infect Dis 2009;49:919-923.
Exposure to coccidioidomycosis in the laboratory can represent a significant hazard, resulting in serious and even fatal infection. In particular, opening culture plates in the lab, without appropriate precautions, can result in the aerosolization of artificially large numbers of arthroconodia. Human coccidioidal infection can occur with inhalation of only 1-10 arthroconidia; therefore, the consequence of such exposure is significant.
Most exposures are inadvertent, and occur when an unsuspecting respiratory sample yields coccidioides in culture in the lab. If C. immitis infection is suspected, it is important for the physician to notify the laboratory regarding this possibility when submitting the specimen. However, despite appropriate warning by the ID Fellow on service, who directly phoned the lab ahead of time, and provided a written history on the lab slip ("h/o cocci"), a recent aspirate managed to escape our laboratory's usual precautions. Specimens from a patient with recognized coccidioidomycosis were submitted to the lab for culture. The plates were opened and examined by a pregnant microbiology technician in the presence of a second technician on day 2 (no growth) and day 3. Three colonies of early growth of a fungus were noted on day 3. At that point, the technicians pieced together the history and the possible risk and notified their laboratory supervisor (it is important to note that the terminology "cocci" on the lab request may be misleading and the full name should be indicated). An incident report was written and filed. Only several days later did the employees report to employee health for evaluation. The question was what, if anything, should be done at that point.
This excellent review article highlights the recommended steps for dealing with laboratory exposure, including assessing the risk, environmental measures, and management of exposed personnel. Although pregnancy increased the risk for more severe and disseminated infection, and also precludes the use of prophylactic azole therapy, it was decided the risk of exposure in this case was minimal. Cultures with less than 72 hours of incubation generally do not present a risk, but formation of arthroconidia can occur as early as 96 hours, and large numbers of arthroconidia may be present by 7-10 days of culture. Baseline and follow-up serologic studies were recommended for the two affected employees, but chemoprophylaxis was not provided. If exposure does occur, the administration of either itraconazole or fluconazole orally for 6 weeks is recommended for non-pregnant employees.
Given the increasing number of elderly who travel to cocci-endemic areas such as Arizona and New Mexico for the winter, and who are at risk for coccidioidal infection when they return home months, laboratories, even those in non-cocci-endemic areas, should be prepared for a possible coccidioides exposure.
The Benefits of Broader Exposure
Source: Ege MJ, et al. Exposure to environmental microorganisms and childhood asthma. N Engl J Med2011;364:701-709.
It has been speculated that children growing up in an overly clean, suburban environment may experience greater atopy and asthma than children growing up in the inner city or on a farm. These investigators report on the results obtained from two large-scale cross-sectional studies, performed in Europe, comparing the prevalence of atopy and asthma in children. The first study focused on 6,963 children of farmers and school-aged children (ages 6-13 years) growing up in largely rural areas of central Europe; 52% lived on a farm; and 8% had a diagnosis of asthma. Dust from the children's mattresses were collected and DNA extractions were performed. The second study focused on a stratified random sample of 3,668 school-aged children (ages 6-12 years) living in central Europe. Only 16% of these children lived on farms and 11% of these children had a diagnosis of asthma. Airborne dust samples were collected from the children's bedrooms for 2 weeks.
Both studies revealed that the risk of asthma was inversely related to the diversity of microbial exposure in the children's bedroom environment, independent of whether they lived on a farm. In addition, the presence of a more circumscribed range of exposure to a few organisms was also inversely related to an increased risk of asthma. Attempts to create a statistically relevant diversity score, either by a factor analysis or by summing the total exposure, demonstrated that diversity of flora, however it was measured, was significantly less in children with asthma (but not atopy).
Several "zones" identified in the factor analysis suggested that exposure to groups of bacteria and fungi were associated with a protective effect, although no single organism could be identified as protective. In addition, exposure to fungal taxon eurotium and penicillium seemed to have a protective effect.
Chinese Duck Egg-Drop Syndrome
Source: A ProMED post; March 29, 2011; available at: http://www.promedmail.org.
Duck-related foods in China are both a delicacy and a dietary staple, from salted duck eggs to pecking duck. Last spring, farmers in several provinces of eastern China, where duck farming is common, noticed that egg production was decreasing. In some areas, egg production fell by more than 90% and some ducks became ill, and quickly died of an apparent infection.
Further study has revealed that a novel flavivirus, called BYD virus, is responsible. The virus was isolated from ducks in several areas, is cytopathic in egg embryo tissue culture, and results in a similar disease when administered to healthy ducks. The virus has been identified as an envelope-positive stranded RNA virus that bears similarity to Tembusu virus in nucleotide sequencing. Tembusu is a mosquito-born virus prevalent in Southeast Asia. This places this new virus in the Ntaya serogroup of the flavivirus genus, similar to Israel Turkey Meningoencephalitis virus (ITM), for which a vaccine has been used for many years in Israel. It is still not clear how the virus is spread, and whether mosquitoes are a required vector. Increasing evidence suggests that another flavivirus, West Nile virus, can be transmitted among crows from cloacal shedding and close contact, and may not require a mosquito vector.
TB in Captive Elephants in the United States
Source: Murphree R, et al. Elephant-to-human transmission of tuberculosis, 2009. Emerg Infect Dis 2011;17:366-371.
Animal-to-human transmission of tuberculosis (TB) has been well-documented for a number of mammalian species, including deer, dogs, and even cats (a topic of a recent "Doc Martin" episode). Transmission of TB from circus elephants occurred in the 1990s. Since then, TB has become endemic in captive elephants in the United States, prompting the FDA in 1998 to require annual trunk washings for tuberculosis culture for all captive elephants in the United States. At present, about 270 Asian and 220 African elephants live in the United States, many of them at refuges for the old or infirm. The problem is, no one really knows how to detect latent TB in elephants (imagine the size of the skin test), although interferon-based assays show promise, trunk washings are not sufficiently sensitive.
In 2004, a non-profit reserve in Tennessee, which cares for retired or sick elephants within a 2,700-acre area, received two Asian elephants with a history of active TB. Infection control and treatment protocols were established, and a separate quarantine area for elephants with active infection was created. Sadly, one the elephants died of TB in 2005, but the other was cleared of infection at 1 year of treatment.
The reserve accepted eight more elephants from the same source in 2006 all of whom had been potentially exposed to TB. The elephants were trained to provide their own truncal washing samples (instill 30-60 cc of saline, lift and lower, lift and lower, and exhale into a plastic bag). In addition, environmental samples from the elephants, their living quarters, and their excrement were cultured. All trunk washing from elephants at the refuge, as well as environmental samples, from 2006 to 2009 were negative, except for one elephant suspected of having active TB, who was quarantined and treated with TB medications (she was poorly tolerant).
Despite these measures, 13 of 46 employees converted their PPD. Five were elephant caregivers, two were maintenance workers, and three were administrative staff who worked in an adjacent two-story building. The two maintenance workers swept hay and sawdust and shoveled excrement on a daily basis, and power washed the barn daily. Smoke tests confirmed that air from the main barn circulated through the administrative building. Although only one caregiver had close contact with the quarantined elephant, employees who worked for > 4 hours in a year in the quarantine area were more likely to convert their skin tests. However, at least five of the employees with skin test conversion had no exposure to the quarantine area.
Employees who converted their skin tests admitted to less rigorous use of N95 mask, in part because trunk washings had been consistently culture-negative from elephants in the main barn, yielding a general laxity regarding IC precautions.
This information suggests that episodic secretion or transmission of TB from elephants believed to be culture-negative by trunk washings is likely. The practice of annual trunk washings for screening should be re-evaluated, and IC practices should be more strictly enforced for employees with contact with high risk elephants.