Minnesota Department of Health (MDH) Bug Bytes

August 22, 2008
Vol. 9: No. 5

Topics in this Issue:

1. First Case of Powassan Encephalitis Ever in Minnesota
2. Encephalitis Guidelines
3. Salmonella Hadar and Turkeys
4. New Penicillin Susceptibility Breakpoints for Streptococcus pneumoniae
5. The Return of Measles

1. First Case of Powassan Encephalitis Ever in Minnesota

In September 1958, a 5 year-old boy from Powassan, Ontario was admitted to the Toronto Hospital for Sick Children with headache, drowsiness, and tremors of the left arm. Two days later he developed fever and lapsed into unconsciousness; he became comatose and died 4 days after his initial admission. An autopsy demonstrated an encephalitis histopathologically consistent with an arthropod-borne encephalitis virus. Portions of his brain were inoculated intracerebrally into mice, which in turn developed encephalitis. The virus isolated from the patient’s brain was designated Powassan virus.

In June 2008, a 10 year-old boy from Cass County, Minnesota became ill with symptoms that included difficulty speaking and swallowing. He progressed to encephalitis. He had no recent history of out-of-state travel. His family reported that he had multiple tick bites in the weeks prior to illness onset. Extensive testing for various infectious and non-infectious causes of central nervous system disease, including West Nile virus and Lyme disease, did not reveal an etiology. We called upon our sister Emerging Infections Program site, the New York State Department of Health Wadsworth Center Viral Encephalitis Laboratory for help. They identified Powassan virus of the “deer tick virus” lineage via PCR in a CSF sample. The patient was also positive for antibody to Powassan virus in serum. This represents the first human case of Powassan virus infection ever identified in Minnesota. Following an extended hospitalization, the patient has continued to improve.

Powassan virus is tick-transmitted flavivirus found in northern regions of North America and eastern Russia. The virus is related to tick-borne encephalitis (“spring-summer encephalitis”) virus endemic to northern Eurasia, as well as several mosquito-borne flaviviruses, including West Nile virus. Since Powassan virus was first identified, fewer than 50 cases have been identified in the United States and Canada. Recent molecular studies have isolated two virus lineages, one found primarily in woodchuck-feeding ticks (“prototype Powassan virus”) and one found in the blacklegged tick, which sometimes feeds on people (“deer tick virus”; the same tick that transmits Lyme disease, anaplasmosis, and babesiosis in Minnesota). Signs and symptoms of Powassan encephalitis may include fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties, and memory loss. Past case reports describe that long-term sequelae are common.

Risk of Powassan encephalitis in Minnesota is likely very small, but the severity of this disease underscores the need for diligent use of tick repellents when spending time in tick habitat.

Learn more about: tick-borne illness>>

2. Encephalitis Guidelines

And speaking of encephalitis, the Infectious Diseases Society of America just released guidelines (August 1 Clinical Infectious Diseases) for the management of encephalitis. Epidemiologic clues and risk factors should be determined to help identify potential etiologic agents. Tick-borne agents in Minnesota causing encephalitis include Borrelia burgdorferi, possibly Anaplasma phagocytophilum, and now Powassan virus. Potential mosquito-borne pathogens include West Nile virus, LaCrosse encephalitis virus, St. Louis encephalitis virus, Eastern equine encephalitis, and Western equine encephalitis. Despite extensive testing, most cases of encephalitis go unexplained. For example, in a sister Emerging Infections Program, the California Encephalitis Project, an underlying cause was not identified in 62% of 334 patients despite extensive evaluation and testing. Of the confirmed or probable cases, 69% were viral, 20% were bacterial, 7% were prion-related, 3% were parasitic, and 1% were fungal.

Unexplained encephalitis is classified as an unexplained critical illness and is a reportable to us at (651) 201-5414.

Learn more about: unexplained critical illness>>


3. Salmonella Hadar and Turkeys

We are investigating a cluster of five cases of Salmonella Hadar that match by PFGE subtype. Illness onset dates ranged from mid-June to mid-July. Illness was associated with turkey consumption including turkey legs, ground turkey patties, and turkey breakfast sausage purchased at three different retail grocery stores of two different grocery store chains. The turkey sausage was consumed raw; we definitely don’t recommend this.

Leftover ground turkey patties were recovered from one case household; they tested positive for S. Hadar with a matching PFGE subtype to the case isolates’ PFGE subtype. The Minnesota Department of Agriculture traced back the turkey legs to a Minnesota turkey processing plant. Another state has also isolated the same S. Hadar PFGE subtype from samples of ground turkey; this ground turkey was traced back to a different turkey processing plant in Minnesota owned by the same company of the first plant.

We reported our findings to the rest of the country. Nationwide, 33 other S. Hadar isolates have been reported to PulseNet from 13 other states. We are currently coordinating with other states and the CDC to investigate these cases.

Learn more about: Salmonella>>


4. New Penicillin Susceptibility Breakpoints for Streptococcus pneumoniae

Streptococcus pneumoniae is a common cause of pneumonia, meningitis, and bacteremia. Identification of antibiotic resistant S. pneumoniae is important because treatment with an antibiotic to which pneumococcus is resistant can result in treatment failure. In January 2008, the Clinical and Laboratory Standards Institute published new penicillin minimum inhibitory concentration (MIC) breakpoints for defining the susceptibility of parenterally treated non-meningitis cases of S. pneumoniae. The change in breakpoints will allow clinicians to increase use of penicillin to treat penicillin-susceptible non-meningitis invasive disease, instead of using broader-spectrum antibiotics. Use of narrow spectrum agents, such as penicillin, is critical to controlling and preventing the spread of antimicrobial resistant S. pneumoniae, as well as other infections Professional society treatment guidelines for community-acquired pneumonia and meningitis state that penicillin should be used for treatment when penicillin-susceptible S. pneumoniae is isolated as the causative pathogen.

Under the former criteria, susceptible, intermediate and resistant MIC breakpoints for penicillin were ≤0.06, 0.12-1, and ≥2 µg/ml, respectively, for all pneumococcal infections, whether treated orally or parenterally. Under the new criteria, parenterally treated non-meningeal isolates have breakpoints of ≤2, 4, and ≥8 µg/ml, respectively; breakpoints for orally treated non-meningeal isolates did not change. Meningeal isolates, all of which should be treated parenterally, are now considered either susceptible or resistant, with penicillin breakpoints of ≤0.06 or ≥0.12, respectively.

To assess the new breakpoints, CDC examined Emerging Infections Program data from 10 sites including ours. During 2006-2007, 7,903 cases of invasive disease were reported with isolates available for 6,845. Of these, 94% were associated with non-meningeal syndromes such as pneumonia with bacteremia. For non-meningeal isolates, comparing new and old breakpoints, 1,192 more were penicillin-susceptible (had been 4,797 [74.7%] and now 5,989 [93.2%]). There were 605 fewer non-meningeal isolates with intermediate susceptibility to penicillin (had been 962 [15.0%] and now 357 [5.6%]) and 587 fewer fully resistant isolates (had been 664 [10.3%] and now 77 [1.2%]). Under the new breakpoints the proportion of meningeal isolates considered to be penicillin-susceptible (73%) was no different. Under the new breakpoints, with elimination of the intermediate category of resistance, 71 more meningeal isolates were categorized as fully resistant (had been 45 [10.7%] and now 116 [27.5%]).

Learn more about: Streptococcus pneumoniae>>


5. The Return of Measles

We recently saw our first non-imported case of measles since 2001. On August 5 measles was confirmed in a 10 month-old child born in the United States to a foreign-born mother from Hennepin County. The child had fever onset on July 29 and was seen in an Emergency Department. The child was seen again on August 2 and 3 in two different clinics. The child had high fever, a rash illness that progressed from hairline to trunk, coryza, and conjunctivitis. The mother self-reported a history of natural illness in herself as a child. An outstanding astute clinician from the Park Nicollet Brookdale Clinic called our 24/7 number on August 3 with a tentative diagnosis of measles and we directed her to draw sera for testing. The child’s infection was diagnosed in our laboratory with a positive IgM serology. A convalescent sera demonstrated an equivocal IgM and significant (i.e. 4-fold rise in titer) IgG serology, further confirming the case.

Cases and outbreaks of measles are currently occurring throughout the United States, with 131 cases reported from 15 states and the District of Columbia from January through July, the most since 1996. Most have occurred in unvaccinated or under-vaccinated individuals. Transmission has occurred in community and healthcare settings including homes, schools, childcare centers, hospitals, emergency rooms, and clinics.

To date, we have not been able to determine the source of the child’s infection. No secondary cases have been detected.

Learn more about: measles>>


Bug Bytes is a combined effort of the Infectious Disease Epidemiology, Prevention and Control Division and the Public Health Laboratory Division of MDH. We provide Bug Bytes as a way to say THANK YOU to the infection control professionals, laboratorians, local public health professionals, and health care providers who assist us.

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Updated Friday, November 19, 2010 at 02:16PM