Environmental reservoirs for human infection

Environmental reservoirs for human infection

Updates By Carol A. Kemper, MD, FACP

Mystery blastomycosis in Wisconsin Hmong

Roy, M, et al. A larger community outbreak of Blastomycosis in Wisconsin with geographic and ethnic clustering. Clin Infect Dis 2013:57:655-662.

An increase in human Blastomycosis cases in Marathon County, Wisconsin from 2005 to 2010, many of which appeared to cluster within households and neighborhoods, prompted epidemiological investigation. Many of the cases occurred in children (not the usual victims), nor with the usual risk factors for exposure, such as outdoor activities. Cases of blastomycosis in Northern Minnesota and Wisconsin are often related to such outdoor activities as camping, hiking, hunting, spending time at a cabin, clearing brush, and gardening.

Cases were defined as a compatible clinical illness, with microbiologic confirmation (either by a positive culture or a clinical specimen with consistent fungal morphology). In all, 55 cases were identified, 70% of which were hospitalized, including two deaths; 20 (45%) of the cases occurred in Hmong residents. This represents a significant increase in the number of annual cases in this area since 2005 - an estimated 11% annual increase with peaks in 2006 and 2010. Asians were disproportionately affected compared with non-Asians (the age-adjusted incidence in Asians increased 586% compared with a decrease of 9% in non-Asians).

Using spatial analysis to map cases, 5 distinct clusters involving 30 (55%) of the cases were identified within certain residences or neighborhoods. Compared with non-Asian cases, case-control analysis demonstrated that Asian cases were more likely to have underlying chronic illness, a household member with Blastomycosis infection, and exposure to an excavation or construction site but they are much less likely to smoke, significantly less likely to participate in those kinds of outdoor activities generally associated with Blastomycosis infection, and they were less likely to travel within 90 days of onset of infection.

While no specific environmental foci could be identified, the authors believe the clustered cases must be related to one or more similar environmental sources, with suspected aerosolization to the neighborhoods or homes. They also speculate that Hmong similar to Filipinos may have a genetic predisposition to B. dermatitidis infection.

Saxophone lung: an off-note?

Similar to the Scottish bagpiper who developed severe fungal pneumonia from exposure to his uncleaned pipes (both Rhodoturula and Fusarium were cultured from the bag on his pipes, which had not been cleaned for years, (see IDA July 2013, p. 118), a recent case study presented at the annual meeting of the American College of Allergy, Asthma and Immunology described a man with persistent cough and wheezing. He was initially treated for allergic pulmonary broncho-aspergillosis (ABPA), but failed to improve with corticosteroids. It was discovered he played the clarinet in a Dixie band but had not cleaned his clarinet in 30 years. Cultures from a reed grew Exophiala spp. and his symptoms resolved once his instrument was cleaned.

Increasingly it is being recognized that woodwind instruments can harbor bacteria and fungi if they are not cleaned properly on a regular basis. "Saxophone lung" is the result of an allergic reaction to repeated exposure to a mold colonizing an instrument. Case reports describe patients with persistent cough, wheezing, and/or shortness of breath — including saxophone, trombone and clarinet players. Similar to ABPA, it may respond to steroids, but removal of the source is ultimately curative. Another similar case in the literature was described as a 48-year-old man who presented with interstitial pneumonia.¹ CT scan showed patchy ground glass infiltrates, and bronchoalveolar lavage suggested a lymphocytic alveolitis consistent with a hypersensitivity pneumonitis. Open-lung biopsy showed a non-specific interstitial pneumonitis. The cause of the hypersensitivity was not discovered until it was revealed that he played the saxophone at which point two different molds were cultured from his instrument (Ulocladium botrytis and Phoma spp.). Serologic studies showed precipitating antibodies to both molds.

So the next time you see a patient with persistent cough or wheezing, or possible ABPA ask the key question do they play a wind instrument?

References

1. Metzger F, et al. Hypersensitivity pneumonitis due to molds in a saxophone player. Chest 2010 138:724-6.

Aedes Aegypti in my backyard

San Mateo County Mosquito and Vector Control District, Press releases dated August 23 and October 22, 2013; http://smcmad.org/data.

Adult and larval Aedes Aegypti mosquitoes have been identified in my backyard (and across the creek from Stanford University) in Menlo Park, California according to press releases from the San Mateo County Mosquito and Vector Control District. Eggs of the mosquito were first identified at Holy Cross cemetery on August 23rd right down the street from Peet’s coffee, prompting an extensive canvassing of the neighborhood, and distribution of traps throughout the area. As of October 11, 246 samples from 1101 homes in Menlo Park yielded 4 adult mosquitos and 5 eggs. Alerts have been distributed to residents to eliminate standing water, drain untended pools or spas, flowerpots, etc.

Efficient biters A. aegypti can easily transmit yellow fever, dengue, malaria, chikungunya - (which are not endemic to this area and we’d prefer to keep it that way)- as well as several arboviruses that may result in encephalitis most of which is not endemic in this area (and we’d prefer to keep it that way). The mosquito is present in the Southeastern United States, but is seldom seen this far north in California. It was last found in Northern California near the San Francisco airport in 1979, but successfully eradicated. With a turn of good luck temperatures dropped this week into the low 40’s enough to eliminate the problem - for now.

Camels as vector for MERS-CoV?

Perara RA, et al. Seroepidemiology for MERS coronavirus using microneutralisation and pseudoparticle virus neutralization assays reveal a high prevalence of antibody in dromedary camels in Egypt, June 2013. Eurosurveill 2013;18(36): ProMED-mail post, September 5, 2103. www.promedmail.org.

Epidemiological studies have attempted to pinpoint the source (or sources) of human infection from Middle East respiratory syndrome coronavirus (MERS-CoV). Preliminary observations suggest MERS-CoV may infect insectivorous bats, and a recent report described an Egyptian tomb bat containing fragments of DNA consistent with MERS-CoV, although there was not sufficient genetic material for complete comparison. Because an index human case of MERS-CoV infection reported exposure to camels investigators turned their attention toward camels as a potential source.

Samples from 110 dromedary camels, 8 water buffalo, 25 cows, 5 sheep, and 13 goats, along with 815 human samples from Egypt were analyzed, and compared with control specimens obtained from archived specimens from Hong Kong, including 260 swine, 204 bird, and 528 human specimens. Specimens were tested using a novel pseudoparticle neutralization assay and a conventional microneutrolisation assay specific for MERS-CoV, distinct from other coronaviruses.

Remarkably, in two separate serological studies, 93.6% and 98.2% of the dromedary camels tested positive for MERS-CoV, some with extra-ordinary high titers. There was no evidence of cross-reactivity with SARS. Until the "camel virus" can be sequenced, it is not known whether the antibodies identified could be cross-reacting with a closely related virus, a chimeric virus, or the true MERS-CoV. Although camels serve as both a source for meat and milk in that area, serologic studies of Egyptian people fail to find much evidence of serologic reactivity, suggesting this viral infection is not common in people living in Egypt.

Because the camels were brought from Northern Africa, the Sudan and Oman for slaughter in Cairo and had been present for some number of weeks before sampling, it is not known where the camels may have acquired infection. Other studies of camels from Oman and the Canary Islands have also found evidence of antibodies to MERS-CoV in camels, suggesting this virus may generally be present in the camel population in Northern Africa and the Middle East and could serve as a potential reservoir for the occasional human infection.

Pilot whales with MRSA blame the sand

Hower S, et al. Clonally related methicillin-resistant Staphylococcus aureus isolated from short-finned pilot whales (Globicephala macrorhynchus), human volunteers, and a Bayfront Cetacean Rehabilitation Facility. Micro Ecol 2013 (epub ahead of print).

MRSA has complicated the care of non-human mammals, such as prized pigs, deer, circus elephants, and horses in critical care with PICC lines. This brief report describes a group of 26 short-finned pilot whales that were accidently beached in a mass stranding in the Florida keys. They were bused to a rehabilitation center for care, during which routine cultures, obtained for clinical purposes, including those obtained from a dead whale necropsy, yielded both MSSA and MRSA.

In order to determine whether there was a reservoir of infection at the facility, surveillance cultures were obtained from whales, staff, volunteers, multiple sites at the facility, the seawater, and the sand from nearby beaches. Samples were obtained at baseline, two weeks later, and 2 months after the whales had departed the facility. MSSA and MRSA were found at the facility when whales and volunteers were present and samples from the adjacent beach were positive all 3 times, including 2 months later. Molecular studies suggested the majority of the MRSA isolates were clonally related to USA300, although there were multiple other non-identical MSSA and MRSA identified from distinct sources. It appears that MSSA and MRSA may be present in the sandy beach environment either from shedding from animals or humans and which can serve as a reservoir for infection.