Minnesota Department of Health (MDH) Bug Bytes
September 5, 2001
Vol. 2: No. 16
1. EEE in Minnesota - Avoid Those Bug Bites
On August 30, our laboratory confirmed the diagnosis of Eastern equine encephalitis (EEE) in a horse from a farm from Blue Earth County that died on August 23. To our knowledge, this is the first evidence of EEE in Minnesota ever. As described in the last issue of Bug Bytes, EEE is transmitted by mosquitoes, and birds serve as the reservoir. Horses and humans are accidental hosts. Clinical cases are usually seen in horses before human cases are recognized. EEE has a very high case fatality rate of >30% (and at times >70%). Onset of illness is sudden with a prodrome of fever, malaise, headache, nausea, vomiting, abdominal pain, and photophobia. Progressive neurological abnormalities then occur, with patients presenting with a diffuse encephalitis. The incubation period for EEE is typically 5-15 days.
We visited the farm to assess the mosquito population; moderate numbers of species that could transmit to humans were seen. However, it's difficult to predict what the human risk may be since variables relating to propagation of EEE in mosquitoes and birds, and then to horses and humans are complex and somewhat unknown. Furthermore, the risk from mosquitoes at this time of the year is declining. We are warning residents of south central Minnesota to avoid mosquito bites. Clinicians are asked to be vigilant for suspect human cases, particularly among residents of south central Minnesota. By the way, as an update to the last issue of Bug Bytes, no human cases of EEE have been seen in Wisconsin to date.
For those that may miss the joy of mosquitoes, you can hear
them at http://www.toutpourlamusique.com/
waves/moustque1.way Attention: Non-MDH link
2. Bacillus cereus - It's the Rice
On July 26, a person called our foodborne complaint hotline (1-877-FOOD ILL) to report a suspected foodborne illness that began after she ate lunch at a Dakota County restaurant. On August 9, 10, 21, and 22 six additional complaints were made to us, either via the hotline, e-mail (firstname.lastname@example.org), or our main phone number (651-201-5414). In all, seven complaints were received involving nineteen ill patrons. Seventeen of the nineteen cases were interviewed, and all reported eating fried rice. Fourteen patrons reported diarrhea, 13 reported vomiting, and 10 reported abdominal cramps. The median incubation period was 2 hours (range 0.5 - 6.5 hours). Bacillus cereus was suspected due to the common food item, the reported symptoms, and the median incubation period. We later isolated Bacillus cereus from the fried rice and from stool from a case.
The restaurant was inspected on August 10 and orders were issued for the correction of violations including the method of preparation and handling of fried rice. An on-site investigation was done again on August 22 after more complaints were received, and at that time the restaurant was closed until compliance with orders could be demonstrated. The restaurant reopened on August 23.
Bacillus cereus is a spore-forming bacterium that produces two enterotoxins. A heat stable enterotoxin is implicated in illness characterized by vomiting and abdominal cramps, with diarrhea in approximately one third of cases. A heat labile enterotoxin is associated with an illness characterized by watery diarrhea and abdominal cramps, with vomiting in approximately one fourth of cases. The incubation period for the former is shorter (1-6 hours) than for the latter (6-24 hours). The mode of transmission is generally via ingestion of food that has been kept at ambient temperatures after cooking, allowing for spore germination and growth. It is not transmitted person-to-person and most recover within 24 hours. Only actively ill patients should be tested for the bacteria.
3. Salmonella DT104 and Cats
In last week's MMWR (at http://www.cdc.gov/mmwr/preview/
mmwrhtml/mm5033a1.htm Attention: Non-MDH link) was an article detailing three outbreaks of multidrug resistant Salmonella Typhimurium associated with employees and clients of veterinary clinics and animal shelters. One of the outbreaks was ours, occurring in 1999 in nine cats and seven humans, associated with a Hennepin County animal shelter. We linked the cats and humans through routine serotyping, molecular subtyping, and antimicrobial resistance testing. All of the isolates we tested were resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline (R-type ACSSuT). Three cat and two human isolates tested were definitive type (DT) 104. We were able to determine a connection for six of the human cases with cats adopted from the shelter.
Small animals shed Salmonella. Persons should wash hands after handling them and especially before eating.
4. A Buffet of Salmonella Newport
Thanks to quick reporting by the Mayo Clinic lab and ICPs, a cluster of salmonellosis cases was identified on August 17. Serotyping and molecular subtyping at MDH revealed that all the cases were Salmonella Newport of an identical PFGE subtype. Nine cases have been identified to date. Cases all reported eating at a common Rochester restaurant, offering a buffet, during the first two weeks of August. Environmental assessment of the restaurant, conducted by Olmsted County Public Health Services, revealed multiple opportunities for cross-contamination between raw and ready-to-eat foods and inadequate heating and cooling procedures. All foodworkers were restricted from work until screened negative for Salmonella, and were instructed on handwashing, proper cooling/heating procedures, and the dangers of working while experiencing gastrointestinal symptoms.
Of interest, the S. Newport isolates were resistant to several antimicrobials including ampicillin, chloramphenicol, sulfamethoxazole, streptomycin, tetracycline, cephalothin, and ceftriaxone. This reflects a continuing trend seen by us of increasing antimicrobial resistance in S. Newport isolates observed since 1999. The resistance to third generation cephalosporins is particularly troublesome, as they are a drug of choice for the treatment of invasive salmonellosis, especially in children, for which fluoroquinolones are not recommended.
5. Meningitis and College Students
In a recent JAMA (at http://jama.ama-assn.org/
issues/v286n6/rfull/joc10124.html Attention: Non-MDH link) was an article examining risk factors for meningococcal disease among college students. Although college students have a lower incidence of meningococcal disease than among the general population of the same age, freshmen who live in dormitories have an elevated risk compared to other college students. Use of the currently available quadrivalent polysaccharide vaccine among college students could substantially decrease their risk of meningococcal disease.
We participated in this published case control study as part of our Emerging Infections Program. Since 1999, we have seen 7 meningococcal disease cases among college students (4 in 1999, 2 in 2000, and 1 to date in 2001).
6. Surgery and CJD
Last week we received a call from a healthcare facility stating that a patient who had had hip surgery three weeks prior had just been diagnosed with Creutzfeldt-Jakob disease (CJD). The instruments used for the surgery had been processed in the normal manner and had been used on subsequent patients. The question was whether or not the subsequent surgical patients had been at risk of exposure to CJD prions since CJD may not be inactivated by typical disinfection and sterilization procedures.
Cases of iatrogenic CJD have resulted from cadaveric pituitary hormone therapy, transplants of dura mater or corneas, and contaminated neurosurgical instruments or depth electrodes. Although CJD prions may be present in other body tissues, transmission is thought to be unlikely. There are no known cases of transmission associated with exposure to blood. Standard precautions are used when caring for patients with CJD. Thus, after consultation with others, we advised that there was not a risk to subsequent patients because CJD would likely not be transmitted from instruments used in hip surgery. Had this been neurosurgery the answer would have been different and would have forced the facility to do a more extensive review.
Infection control recommendations for CJD were published
in the May 1, 2001 issue of Clinical Infectious Diseases and are
also at http://www.who.int/emc-documents/
tse/whocdscsraph2003c.html and at http://www.cdc.gov/od/ohs/
biosfty/bmbl4/bmbl4s7d.htm Attention: Non-MDH links
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