Minnesota Department of Health (MDH) Bug Bytes
July 29, 2008
Vol. 9: No.3
West Nile virus (WNV) is back. Last week we received reports of the first 3 cases of the 2008 season. All three had the milder West Nile fever alone; illness onsets were July 4, 13, and 18, and ages of the patients were 2, 15, and 65 years. The cases resided in Becker, Carver, and Clay Counties. For the rest of the United States, 14 states have reported 43 WNV cases with the median age of patients being 46 years (range: 12-80 years). None of the cases were fatal.
With increasing Culex tarsalis mosquito populations in Minnesota we are entering the prime time for WNV transmission.
Learn more about: west nile virus>>
Human anaplasmosis (HA, formerly known as human granulocytic ehrlichiosis) is a tick-borne rickettsial disease caused by infection with Anaplasma phagocytophilum, a Gram-negative, obligate intracellular bacterium of neutrophils. A. phagocytophilum is transmitted by the blacklegged tick in Minnesota. The incidence of reported HA cases in Minnesota has risen dramatically during recent years, to a record number of 322 reported cases in 2007 (see July 3 issue of Bug Bytes). In November 2007, we were contacted about an A. phagocytophilum infection in a hospitalized 68-year old patient who in October had received multiple blood transfusions and subsequently developed thrombocytopenia.
A peripheral blood smear demonstrated intracellular A. phagocytophilum morulae in neutrophils. Retrospective review of a blood smear from October 15 showed no evidence of intracellular morulae. In early November, Memorial Blood Centers (MBC) initiated an investigation to identify whether any donors of the 59 transfused blood products had evidence of A. phagocytophilum infection. MBC also asked all donors to submit a post-donation blood sample for serological testing and fill out a questionnaire describing recent illness history and potential tick exposure.
A single red blood cell (RBC) donor, a 64-year old female from Saint Louis County, was positive for evidence of A. phagocytophilum infection by both PCR and IFA. Her PCR-positive RBC product was donated on September 28 and transfused on October 13. Parts of Saint Louis County are endemic for HA. She did not recall a tick bite but described outdoor activities in wooded areas in a blacklegged tick-endemic region of northeastern Minnesota within the month before her donation. She reported no history of febrile illness during the month before or after her October donation.
We were notified yesterday of another possible transfusion-associated HA case and have initiated an investigation.
During 2001-2005, Minnesota reported one of the highest incidences of HA in the United States at 2.5 cases per 100,000 persons, and the incidence in some Minnesota counties (primarily in the central and east-central parts of the state) is over 50 times higher than the state average. Physicians should be vigilant for possible transfusion-transmission of tickborne diseases, especially when using blood products originating from highly endemic areas.
Learn more about: anaplasmosis>>
In Minnesota, we work with the Minnesota Board of Animal Health (BAH) on animal rabies case investigations. We handle human health issues and BAH handles animal health issues. During 2003-2007, we tested 11,680 suspect animals for rabies by the direct fluorescent antibody test (median, 2,334 samples per year). Positive samples from 2004 on were further tested by reverse transcriptase polymerase chain reaction (RT-PCR) and sequenced. Two hundred ninety four (2.5%) of the samples tested positive. The most frequently tested species were cats (n=3,984), dogs (n=3,493), and bats (n=2,340). The highest proportion of positive samples (51%, 152/296) occurred in skunks, Minnesota’s terrestrial rabies reservoir. Most skunks in the northern two thirds of Minnesota were infected with the Western Canadian Skunk (WCS) variant and most skunks in southern Minnesota were infected with the North Central United States Skunk (NCUSS) variant. Among bats, 79 (3.4%) of 2,340 submissions tested positive. Two big brown bats were identified with silver-haired bat variants of rabies. The remainder of the bats carried the expected host variant. Over the 5-year period, 418 raccoons were tested, and all were negative. Among domestic farm animals (cattle, horses, goats, and sheep), cattle had the highest proportion of positive samples (9%, 27/301) and represented 90% (27/30) of positive samples within the group. Domestic carnivores (dogs, cats, and ferrets) had a lower proportion of positive samples (0.4%, 32/7,513), although they constituted the majority of submissions. Bat variants were identified in one dog and one woodchuck. All other terrestrial animals were infected with either the WCS or NCUSS variants.
Note that these numbers and proportions cannot be used to estimate the risk from any single exposure. We offer consultation regarding exposure and rabies risk to health care providers 24/7 at 651-201-5414.
Learn more about: rabies>>
Since April 2008, 1,304 persons infected with Salmonella Saintpaul with the same PFGE pattern have been identified in 43 states and the District of Columbia. Among the persons with information available, illnesses began between April 10 and July 6, 2008. Patients range in age from <1 to 99 years; 53% are female. The rate of illness is highest among persons 20 to 29 years old; the rate of illness is lowest in children 5 to 19 years old and in persons 80 or more years old. At least 239 persons were hospitalized. The infection may have contributed to two deaths.
An initial epidemiologic investigation in New Mexico and Texas comparing foods eaten by ill and well persons identified consumption of raw tomatoes as strongly linked to illness. Recently, many clusters of illnesses have been identified in Texas and other states among persons who ate at restaurants. These clusters have led CDC and other state health departments to broaden the investigation to include food items that are commonly consumed with tomatoes. A later national case-control study found an association between illness and tomatoes, jalapenos, and cilantro. These foods were often consumed together, not allowing for determination of which item(s) caused the illnesses.
As reported in the last issue of Bug Bytes, we became aware of a cluster of cases in Minnesota on July 3. Eight of the first 9 cases we interviewed all had patronized the same restaurant. All had consumed dishes with a red pepper/jalapeno topping. At that point in time the restaurant had stopped using fresh tomatoes. In a subsequent case-control study comparing 13 ill to well meal companions and also to randomly selected well patrons from the same restaurant, we were able to definitively link illness to jalapenos (p= 0.03; p = 0.00002). Our colleagues at the Minnesota Department of Agriculture (MDA) were able to trace the source of the jalapenos back to one of two farms in Mexico and distributors based in Texas. Based on our information and that from elsewhere, the U.S. Food and Drug Administration (FDA) tested and isolated the same strain of Salmonella from a jalapeno from the same distribution center where our likely Texas distributor was located. A detailed account of our investigation was reported in the July 24 editions of the Minneapolis Star Tribune and the St. Paul Pioneer Press. As of this date, we have had 31 confirmed cases; two were infected out-of-state, 27 were associated with the restaurant; and two cases were unrelated to the restaurant.
Thanks to all the clinicians, laboratories, disease reporting sources, MDA, and FDA, we were able to help identify jalapenos as a cause of this large, lengthy national outbreak. It is still unclear what role tomatoes, if any, played elsewhere in the outbreak.
Learn more about: salmonella>>
As part of our Emerging Infections Program (EIP) Active Bacterial Core Surveillance (ABCs) we, along with 10 other EIP sites, have been conducting active population-based surveillance for several invasive bacterial pathogens since 1995 including group B streptococcus (GBS). A recent (May 7) article in JAMA documented the dynamic epidemiology of nearly 15,000 cases GBS disease from 1999-2005 in EIP sites among newborns and others.
The incidence among infants from birth through 6 days of age (early-onset cases) decreased 27% over the time period from 0.47 per 1,000 live births to 0.34 per 1,000 live births. This reduction coincided with the revision of GBS perinatal prevention guidelines advocating antenatal culture-based screening for identifying pregnant women chemoprophylaxis candidates.
On the other hand, the incidence for persons aged 15 to 64 years increased 48%, and 20% among adults aged 65 years and older. It is unknown what the reason is for the increase. There is a disproportionate disease burden among blacks both in pregnant and non-pregnant adults of all ages.
In 2007, 331 cases of GBS disease including 12 deaths were reported in Minnesota. There were 23 early-onset cases, only 12 of whom had undergone prenatal GBS screening.
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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