Minnesota Department of Health (MDH) Bug Bytes
August 10, 2001
Vol. 2: No. 15
1. Alert: EEE to Our East
In the last 2 weeks, approximately 21 horses have died in Rusk, Barron, and Chippewa Counties, Wisconsin, approximately 55 miles east of the Minnesota border. A specimen from one horse was tested by our laboratory and found by PCR to be positive for eastern equine encephalitis (EEE) virus; serum from a second horse was positive for IgM antibody to EEE virus at the USDA National Veterinary Services Laboratory.
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. West Nile virus is getting all the publicity but it pales in comparison to EEE. 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 are assisting Wisconsin in mosquito population assessment in the affected area.
Although no human cases have been reported in Wisconsin to date, clinicians are asked to be vigilant, particularly among persons returning to Minnesota from western Wisconsin. We encourage collection and submission of sera for testing. Please call us at (612) 676-5414 for assistance.
2. Tiger Bite
On Sunday July 22, we were called by a physician for advice about a 7 year-old child that had been bitten by a tiger at an animal refuge in southern Minnesota. The tiger had broken through its cage and picked up the child in its mouth and carried it, inflicting severe puncture wounds. In these instances, there are two options with respect to rabies: 1) treat the patient (with rabies immune globulin and a 5-dose series of rabies vaccine), or 2) test the animal. The attending physician elected not to treat the child.
As you are probably aware, much media attention ensued as the Minnesota Board of Animal Health and we proceeded to have the animal euthanized and tested. To clarify to readers, despite what may have been reported, there was no other recognized public health option. There is no recognized rabies incubation period or quarantine period for wild animals such as tigers; thus, the period of viral shedding in saliva is undetermined. There is no way to test the brain of the animal without killing it. According to the Natural History of Rabies 2nd Edition, in order to test the brain, "…at least two slides each of hippocampus, brain stem, and cerebellum should be prepared…" There is no reliable way to test the skin, neck, or saliva. Again, according to this reference, "…since a 100% correlation between the rabies virus in these tissues and the salivary glands of infected animals does not exist, these tests cannot be used to assess the need for human rabies post-exposure treatment after a bite." The animal was euthanized and tested and found to be negative for rabies.
3. Hepatitis C Cluster
On April 16, we were notified by a St. Louis County plasma center of a hepatitis C virus (HCV) positive donor who had a documented seroconversion. On April 23, the same plasma center reported two additional HCV-seroconverting donors, one of which was the sex partner of the previously reported case.
In conjunction with St. Louis County Public Health, we reviewed records to identify both acute and chronic HCV cases reported since the last quarter (October-December) of 2000. MDH STD disease investigators were deployed to interview cases to identify possible intersects within community contacts. We identified six acute HCV cases in injecting drug users (IDUs) - a cluster of three in St. Louis County (two white, one Native American); two in Hennepin County (both Hispanic, one with ties to the Native American community); and one in Cass County (Native American). HCV testing was recommended for persons identified as needle-sharing or sex partners of the acute cases. To date, no intersection has been found between the six cases, except for the two plasma donors noted above; however, we did identify a concentration of needle-sharing IDUs among Native Americans in Cass County. Several of these persons were previously reported as chronically infected with HCV. The identification of these HCV cases highlights the importance of considering HCV infection in persons presenting with a history of IDU, evidence of recent IDU, or obvious gastrointestinal symptoms of viral hepatitis. These individuals may also be at risk for HIV infection. Persons suspected of being at risk for HCV infection should also be tested for hepatitis A and B and vaccinated if susceptible.
4. Swimming with E. coli O157:H7
Through routine surveillance, submission of isolates, and PFGE subtyping, we noticed a cluster of eight cases of E. coli O157:H7 last week (thank you ICPs and labs!). We interviewed the cases and found that seven had swam or waded in Bush Lake in Bloomington during the week of July 15-21. Four persons were hospitalized; there were no cases of HUS. No source case was identified, but it is likely that a child ill with E. coli O157:H7 had an accident and contaminated the swimming area. Others became infected when they accidentally ingested contaminated water.
Bloomington health officials took note of water quality testing since then and closed Bush Lake due to high fecal coliform levels. These levels may be unrelated to the E. coli O157:H7 cluster, but may reflect an issue of high bather load, low water turnover, or other problems. Our investigation of the E. coli O157:H7 cases continues.
5. Viral Meningitis Time
Viral meningitis season is right on schedule. Each year in July and August, we receive an increased number of reports of suspect viral meningitis cases and this year is no exception. Four communities in north and central Minnesota have reported small clusters of cases in the last two weeks. Reports of sporadic cases have been received from throughout the state with 42 cases reported so far for July. Several different enteroviruses have been identified in cases for which culture results are available, including echovirus types 6, 9, and 18. Enterovirus is spread person-to-person either by the fecal-oral route or through respiratory secretions.
6. We're No. 2
Minnesota was ranked the second healthiest state in the country for 2001 by the Morgan Quitno Press. Twenty-one factors, including two infectious disease factors (AIDS and STD incidence rates) were used to calculate the rankings. Last year Minnesota placed third by this same organization. On a related note, Minnesota was just found to have the second best immunization rates in the country among preschoolers based on the CDC National Immunization Survey (ranked second for two of the three categories [we ranked third in the third category] published in last week's MMWR at http://www.cdc.gov/mmwr/preview/
mmwrhtml/mm5030a1.htm Attention: Non-MDH link). Why not No. 1 next year?
7. Annual Communicable Disease
Our annual summary of communicable diseases reported to MDH for 2000, published in our Disease Control Newsletter (DCN) has gone to press, and should be mailed shortly. If you are not on the DCN mailing list and want to be, contact us at 1-800-366-2597.
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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