Minnesota Department of Health (MDH) Bug Bytes

September 3, 2008
Vol. 9: No. 6

Topics in this Issue:

1. Epidemic Keratoconjunctivitis
2. A Difficult Tuberculosis Outbreak
3. Pasteurella multocida
4. Frozen Rodents: Another Risky Food
5. Save the Date

1. Epidemic Keratoconjunctivitis

We were notified on August 21 of multiple cases of severe epidemic keratoconjunctivitis (EKC) occurring in southeastern Minnesota. Patients were seen in local optometry, primary care, and ophthalmology clinics, and emergency rooms and regional tertiary care facilities.

We queried local ophthalmology clinicians for possible cases of EKC. To date, 123 cases have been reported with onset from 6/28/08 to 8/22/08. Of the reported cases, 54% are female with a median age of 52 years (range, 3 months to 91 years) with 15% being <18 years of age. Nine cases grew adenovirus on viral culture of conjunctivae. Strain typing is in process. Most reported cases have not had viral cultures obtained but their symptoms were consistent with a viral conjunctivitis.

Of the 49 cases whose medical records have been reviewed, all had unilateral or bilateral conjunctivitis, 73% had eyelid swelling, 67% had decreased visual acuity, 61% had evidence of keratitis or corneal erosions, and 47% had corneal membranes that required stripping. Most have not yet had resolution of their symptoms. The clinical course generally occurred over a period of 4 or more weeks with corneal membrane formation occurring during the second to third week. No permanent visual loss has been reported.

Multiple family clusters and nosocomial transmission has occurred. Infection control recommendations were provided to all ophthalmology and optometry clinics, as well as to schools and day care centers, in the region including:
(1) emphasizing standard precautions including meticulous hand hygiene and use of gloves and face shields if mucous membrane or body fluid contact is possible,
(2) using designated exam rooms for patients with possible eye infections,
(3) performing high-level disinfection or sterilization of all reusable instruments according to manufacturer recommendations, and
(4) using single use medication vials or discard multiuse vials after one use.
Infection control resources for the public and health care providers are available at: http://www.health.state.mn.us/divs/idepc/diseases/conjunctivitis/index.html.

Cases in non-Minnesota residents have been reported to us and additional case clusters may be occurring in Minnesota as well as other states. Staff at the CDC Division of Healthcare Quality Promotion are assisting in the investigation elsewhere in the country.

Please report unusual cases to us.

Learn more about: conjunctivitis>>

2. A Difficult Tuberculosis Outbreak

We and the Nobles County Community Health Services Department are investigating a cluster of tuberculosis (TB) cases that have occurred in the Worthington area. Six culture-confirmed and 7 suspect cases of TB are currently on four-drug TB therapy. Evidence suggests recent TB transmission in the area. Only one of these case-patients was not foreign-born or born in the United States to foreign-born parents. The case-patients range in age from 6 months to 40 years, and include six children under the age of 5 years and three children between the ages of 5 and 13 years. Drug susceptibility testing on three of the patients revealed that the isolates are susceptible to all of the four standard first-line TB medications. Preliminary genotyping has not identified any clear links to TB cases in other states.

The index case was a 6-month old reported in May with culture-positive pulmonary disease who had been ill for 3-4 months. Many of the adults in this child’s extended family and household have been diagnosed with latent TB infection (LTBI), and all five siblings and cousins are being treated for suspect active TB. The father of the case is involved in a musical band that performs in church and in the community. An investigation of the band identified the likely source case to be an adult male who moved to the United States from Central America in 2005. His symptoms began in October 2007 and it was determined that he likely was infectious for at least 9 months before a diagnosis was made and treatment begun. Contact investigations identified individuals with LTBI in the source case’s household, workplace, and in social settings associated with the band. The source case sang with the band that played regularly at church services and at several community events during spring 2008, exposing approximately 200 people. Transmission of TB through singing has been documented previously.

Of the 20 TB cases from this particular country of origin that have been reported in Minnesota since 1997, 12 (60%) currently or previously lived in Nobles County, and two others lived in neighboring counties. This outbreak is occurring in a rural county that typically has 1-4 TB cases per year and illustrates the challenges of maintaining an adequate TB control infrastructure in a low incidence area. Local public health resources have been stressed by TB case reporting, contact investigations, providing directly observed therapy, and ensuring that infected contacts complete a 9-month course of LTBI therapy. Specific challenges faced by the health department and medical providers in this outbreak include lack of health insurance for most of the adults involved in the outbreak, languages and cultural differences, delays in obtaining laboratory results, and a reluctance on the part of patients to reveal the identity of their close contacts.

Over 80% of TB cases in Minnesota occur among foreign-born persons. Approximately 20% occur outside of the Twin Cities metropolitan area. Although TB cases are decreasing nationally, for the first time since national surveillance began in 1953, the TB case rate in Minnesota (4.6/100,000) exceeded the national rate (4.4/100,000) in 2007.

Learn more about: Tuberculosis>>


3. Pasteurella multocida

Two weeks ago we received a report of a suspect meningococcal meningitis case in a 39-year old female. The patient was found unresponsive in her home with a high fever. The hospital clinical laboratory initially read a Gram-stain of CSF as having white blood cells and Gram-negative bacilli. The patient was transferred to a tertiary care hospital and the next day this hospital lab reported Gram-negative coccobacilli and a diagnosis of Pasteurella multocida.

P. multocida is estimated to infect up to half of the 1-2 million persons bitten, scratched, or licked on open wounds by dogs or cats each year in the United States. It is part of the normal flora of a number of animal species including dogs, cats, Norway rats, pigs, opossums, and buffalo. Human cases are thought to result from the direct inoculation of organisms or from respiratory tract colonization with spread to other organ systems causing skin/soft tissue infections, bone/joint infections, sepsis, pneumonia, endocarditis, or meningitis. Meningitis is relatively rarely reported. Of 29 P. multocida meningitis cases reported in the English language literature, mortality was 25% overall.

Although most commonly associated with cat bites, the Minnesota case owned a dog. She had no known bites but was very close to the animal.

Learn more about: meningococcal meningitis>>


4. Frozen Rodents: Another Risky Food

We have an article in press that documents an emerging zoonotic disease risk. In December 2005 and January 2006, we identified 4 human clinical isolates of Salmonella Typhimurium that were indistinguishable by PFGE. We interviewed them and found that three of the cases attended the same junior high school and had handled snakes in the science classroom, and the fourth had a sibling in the school. We collected environmental samples from the school’s science classroom for Salmonella culturing; these included environmental samples and frozen vacuum-packed mice purchased over the Internet to feed the classroom snakes (both were constrictors).

Through PulseNet, a national molecular subtyping surveillance network for enteric bacteria, 21 human S. Typhimurium isolates with indistinguishable PFGE patterns were identified in the United States, December 2005 through August 2006. Each state determined whether these human cases had recent exposure to snakes fed vacuum-packed rodents. Nineteen of the cases were interviewed, and 7 cases reported contact with frozen vacuum-packed rodents from the same Internet-based supplier in Texas. One of these 7 cases was hospitalized for 7 days.

In Minnesota, the outbreak PFGE subtype of S. Typhimurium was isolated from the snakes, frozen feed rodents, and the classroom environment. Three human cases were identified in Michigan, Pennsylvania, and Wyoming. The outbreak PFGE subtype of S. Typhimurium was isolated from the Pennsylvania case’s frozen rodents (this 14 year-old boy was feeding four pet constrictors!) and the Michigan case’s pet snake. Texas state officials conducted trace-backs of the vacuum-packed mice and collected samples at the breeding facility, a relatively small breeder with over 100,000 rodents. The outbreak PFGE subtype of S. Typhimurium was also isolated from this rodent facility.

Human transmission likely occurred through direct contact with snakes and contaminated environmental surfaces. Our investigation was the second recent multi-state salmonellosis outbreak associated with commercially distributed rodents (the first being an outbreak associated with “pocket pets” which we also investigated and reported on in the New England Journal of Medicine). Users of these rodents need to be educated about the risk, and stronger oversight of the commercial rodent industry is warranted as this breeder used poor animal husbandry.

Learn more about: Salmonella>>


5. Save the Date

The 14th Annual Emerging Infections in Clinical Practice and Public Health will be held Friday November 14 at the Minneapolis Radisson University Hotel. More information and registration information is at https://cme.ahc.umn.edu/Scripts/4Disapi.dll/4DCGI/events/ConferenceList.html?Action=GetEvents



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