Population-based incidence of human granulocytic ehrlichiosis in northwestern Wisconsin, 1997-1999.

The incidence of human granulocytic ehrlichiosis (HGE) in the upper Midwest is uncertain. Active surveillance for suspected HGE was conducted from 1997 through 1999 in a 13-county region of northwestern Wisconsin. Suspected HGE cases were classified, according to the national case definition, as confirmed, probable, or not HGE. In total, 112 confirmed cases and 30 probable cases of HGE were identified. The median age of the 142 case patients was 56 years, and 92 (65%) were male; 111 (78%) were residents of the surveillance region. The mean annual incidence of confirmed and probable HGE was 9.3 cases per 100,000 residents; there was no increase from 1997 to 1999. The incidence was highest among persons > or =50 years old and residents of Washburn County. The incidence of HGE in this region exceeded prior estimates, but it was lower than the reported incidence in areas of endemicity in Connecticut.

Tickborne infections as a cause of nonspecific febrile illness in Wisconsin.

Lyme disease, human granulocytic ehrlichiosis (HGE), and babesiosis are tickborne infections that are indigenous to Wisconsin. To assess their importance as a cause of nonspecific fever, we recruited patients with febrile illness at 10 clinics in northwestern Wisconsin from May through August of both 1997 and 1998. Eligible patients had a temperature >38.0 degrees C but no rash or other localizing source. Acute and convalescent serological tests were performed for Borrelia burgdorferi, Babesia microti, and Ehrlichia equi; polymerase chain reaction was performed to detect granulocytic Ehrlichia rDNA. Seventeen (27%) of 62 eligible patients had laboratory evidence of tickborne infection, including 7 (11%) with probable Lyme disease only, 8 (13%) with HGE only, and 2 (3%) with apparent coinfection. No patients with Babesia infection were identified. Patients with and without tickborne infection were similar with regard to age, sex, symptoms, history of tick bite, and outdoor exposure. The results suggest that tickborne infections are an important cause of nonspecific febrile illness during the tick season in northwestern Wisconsin.

Ixodes scapularis (Acari: Ixodidae): abundance and rate of infection with Borrelia burgdorferi in four state parks in Wisconsin.

Four state parks located in Lyme disease endemic regions of Wisconsin were surveyed for the presence of Ixodes scapularis Say during May and June of 1998 by drag sampling along hiking trails. Nymphal abundance varied between parks, with the average number of nymphs encountered in 1 h ranging from 6.2 +/- 3.8-47.1 +/- 36.3 (mean +/- SD). Questing nymphs were tested for the presence of Borrelia burgdorferi by culture in BSK medium and 7-12% was found to be infected. The average risk of encountering an infected nymph (entomologic risk index) ranged from 0.5 to 5.2 infected nymphs per hour. The highest entomological risk index was recorded from a small island park in northwestern Wisconsin during the last week in May (8.0 infected nymphs per hour). These results indicate a lower risk for human Lyme disease exposure in Wisconsin state parks in comparison with highly endemic areas of the northeastern United States.

Rabies prevention.

Rabies is an almost uniformly fatal encephalomyelitis with no treatment option other than supportive care for those who contract the illness. Mortality worldwide is estimated to be 40,000-70,000 people annually. Fortunately, public health measures begun in the 1940s and 1950s regarding vaccination and control of domestic animals in this country and the availability of safe and effective rabies postexposure prophylaxis treatment (RPEP) for humans has made rabies a rare disease in the United States. Community healthcare providers continue to play a pivotal role in the prevention of this devastating disease. This article emphasizes the challenges that the evolving epidemiology of rabies presents to our healthcare system, especially regarding international travel, the importance of domestic animal vaccination against rabies, the use and cost of RPEP, recent rabies epizootics in wildlife populations and the role of bats in disease transmission.

A foodborne outbreak of Campylobacter jejuni (O:33) infection associated with tuna salad: a rare strain in an unusual vehicle.

We report a foodborne outbreak of Campylobacter jejuni infection in a summer camp. Outbreak-related cases occurred in 79 persons including 3 secondary cases in campers. Campylobacter jejuni was isolated from stool specimens from 16 of 21 patients who submitted a sample; 13 viable isolates were serotyped and all were serotype O:33 (somatic O scheme) or HL:18 (heat-labile scheme), and biotype III (Lior scheme). This serotype is widely distributed geographically but rarely isolated from humans. Samples of water from the wells supplying the camp were negative for faecal coliforms, and raw milk had not been served in the camp. A matched (1:1) case-control study identified tuna salad served for lunch on 19 July as the likely food item associated with illness (matched odds ratio=22; 95% confidence intervals (CI)=3.6-908). Swimming in the camp pool and other recreational water use in area lakes by the campers were not statistically associated with illness. The precise mechanism of introduction of the organism into the tuna salad remains unknown; contamination most likely occurred through cross-contamination with another food product, the hands of a food handler, or a work surface. Several deficiencies in the operation of the camp kitchen were identified. In Wisconsin, kitchens of such camps are subject to different inspection rules than restaurants. Camp staff, administrators, counselors, food managers, and infirmary staff, should fulfil important roles in their respective areas to prevent future outbreaks.

Hepatitis A infections in Wisconsin: trends in incidence and factors affecting surveillance, 1986-1995.

From January 1986 through December 1995, 4,143 cases of hepatitis A virus (HAV) infection were reported in Wisconsin. The annual hepatitis A incidence remained stable from 1986 through 1988, with a mean annual rate of 4.7 cases per 100,000 (endemic HAV incidence rate). During 1989-1993, the incidence of HAV infection increased with a peak in 1992 of 19 cases per 100,000 population. A large foodborne outbreak (1992) and community wide outbreaks among African American residents (1989-1993) and Native Americans residents (1991) were associated with these high rates of HAV infection. The community wide outbreaks affected different groups: among African Americans, incidence rates were highest in young adults 15-34 years old; among Native Americans rates were highest in children 5-14 years old. Approximately 2,343 (57%) patients had no apparent risk factor (e.g., international travel, contact with person with HAV infection) for acquiring HAV infection. Factors limiting control of HAV infection in Wisconsin included poor reporting by laboratories (only 19% of all reported cases were independently reported to the Wisconsin Division of Health by a laboratory and fewer than 50% of these reports were from private laboratories), incomplete reporting by Wisconsin physicians or designees (74% of cases confirmed in Wisconsin laboratories were reported in 1995), failure to submit follow-up case report forms (14% of cases), and a prolonged interval between diagnosis and follow-up (> or = 15 days for 610 cases). Efforts should be enhanced to improve the reporting of cases of HAV infection by private laboratories, particularly through the use of automated electronic reporting.

Incomplete sanitation of a meat grinder and ingestion of raw ground beef: contributing factors to a large outbreak of Salmonella typhimurium infection.

Consumers in the United States continue to eat raw or undercooked foods of animal origin despite public health warnings following several well-publicized outbreaks. We investigated an outbreak of Salmonella serotype Typhimurium infection in 158 patients in Wisconsin during the 1994 Christmas holiday period. To determine the vehicle and source of the outbreak, we conducted cohort and case-control studies, and environmental investigations in butcher shop A. Eating raw ground beef purchased from butcher shop A was the only item significantly associated with illness [cohort study: relative risk = 5.8, 95% confidence interval (CI) = 1.5-21.8; case control study: odds ratio = 46.2, 95% CI = 3.8-2751]. Inadequate cleaning and sanitization of the meat grinder in butcher shop A likely resulted in sustained contamination of ground beef during an 8-day interval. Consumer education, coupled with hazard reduction efforts at multiple stages in the food processing chain, will continue to play an important role in the control of foodborne illness.

Prevalence of granulocytic Ehrlichia infection among white-tailed deer in Wisconsin.

Human granulocytic ehrlichiosis (HGE) is caused by an agent that is nearly indistinguishable from the veterinary pathogens Ehrlichia equi and Ehrlichia phagocytophila. The deer tick, Ixodes scapularis, is a vector of the HGE agent, and the white-tailed deer is the primary host for adult Ixodes ticks. We assessed the distribution of granulocytic Ehrlichia infection among deer living within (Wisconsin) and outside (western and southern Iowa) the geographic range of L. scapularis. Whole-blood samples were tested for HGE 16S ribosomal DNA (rDNA) by PCR, and E. equi antibody was detected by indirect immunofluorescence assay (IFA). Antibody titers of > or = 1:64 were defined as positive, and all positive samples were retested with a second lot of substrate antigen. E. equi antibody was present in 14 (8%) of 187 Wisconsin deer and 0 of 60 Iowa specimens (rate ratio undefined; P = 0.025). An additional 30 serum samples from Wisconsin deer were excluded because IFA results were discrepant between substrate lots. The reciprocal antibody titers ranged from 64 to 512 (geometric mean, 141) for positive samples. PCR results were positive for 27 (15%) of 181 Wisconsin deer. The prevalence of infection in northwestern Wisconsin deer was not significantly different from that in central Wisconsin deer, as determined by IFA and PCR. In two samples that were sequenced, the 16S rDNA was nearly identical to that of the granulocytic Ehrlichia species but distinct from that of Anaplasma marginale. The DNA sequences of the samples differed from the published sequences for E. equi, E. phagocytophila, and the HGE agent by 1 or 2 nucleotides (> or = 99.1% homology) at phylogenetically informative sites. Granulocytic Ehrlichia organisms in deer are widely distributed within the geographic range of L. scapularis in Wisconsin. Deer may serve as useful sentinels for areas where HGE transmission to humans may occur.

Spatial analysis of the distribution of Lyme disease in Wisconsin.

Surveillance measures for human cases of Lyme disease in Wisconsin were compared and associated with tick distribution and vegetation coverage. During 1991-1994, 1,759 confirmed human cases of Lyme disease reported to the Wisconsin Division of Health were assigned a county of residence, but only 329 (19%) could be assigned with certainty a county of exposure. Distributions of cases by county of exposure and residence were often consistent from year to year. Tick distribution in 46 of 72 Wisconsin counties was mapped based on collections by researchers, statewide surveys of infested deer, and submissions from the public. Satellite data were used to calculate a normalized difference vegetation index (NDVI) for each county. A geographic information system (GIS) was used to map distributions of human Lyme disease cases, ticks, and degree of vegetation cover. Human case distribution by county of exposure was significantly correlated with tick distribution; both were positively correlated with high NDVI values in spring and fall, when wooded vegetation could be distinguished from agricultural crops in the satellite image. Statistical analysis of spatial patterns using a measure of spatial autocorrelation indicated that counties with most human cases and ticks were clustered in parts of western Wisconsin. A map delineating the counties with highest risk for Lyme disease transmission was generated based on numbers of exposed human cases and tick concentrations.

An outbreak of cryptosporidiosis associated with a resort swimming pool.

An outbreak of cyptosporidiosis occurred in late April 1993 among resort hotel guests which was temporally associated with, but geographically distant from, a massive waterborne outbreak of cryptosporidiosis in Milwaukee, Wisconsin, that occurred in late March and early April of 1993. A case-control study was performed among groups with members who reported illness and among a systemic sample of groups who stayed at the resort hotel during the risk period. Of 120 persons interviewed, 51 (43%) met the case definition. Swimming in the resort hotel's pool was significantly associated with case status (OR = 9.8; 95% Cl 3.4, 29.7), as was consumption of ice from the hotel's ice machines (OR = 2.3; 95% Cl 1.01, 5.2). When analysis was restricted only to laboratory-confirmed cases and controls, swimming pool use was the only risk factor significantly associated with illness (OR = 13.0; 95% Cl 2.6, 88.7). Following waterborne outbreaks of cryptosporidiosis associated with water supplies, swimming pools should be considered as possible ongoing sources for transmission regionally.

Massive outbreak of waterborne cryptosporidium infection in Milwaukee, Wisconsin: recurrence of illness and risk of secondary transmission.

Contamination of the public water supply in Milwaukee during March and April 1993 resulted in a massive outbreak of cryptosporidium infection. We investigated the clinical and epidemiological features of visitors to the Milwaukee area in whom cryptosporidiosis developed, and we conducted a telephone survey of Milwaukee County households to evaluate the risk of recurrent illness and secondary transmission. Cryptosporidium infection during this outbreak generally seemed more severe than cases described in previous reports of large case series. The risk of secondary transmission within a household was low (5%) when the index case involved an adult. The recurrence of watery diarrhea after apparent recovery was a frequent occurrence among visitors with laboratory-confirmed cryptosporidium infection (39%) and among visitors and Milwaukee County residents with clinical infection (21%). The interval between the initial recovery and the onset of recurrence was prolonged (> or = 5 days) in 6%-8% of persons. This pattern of recurrence and its impact on transmission and our understanding of the pathophysiological mechanisms of cryptosporidium infection merit further investigation.

A massive outbreak in Milwaukee of cryptosporidium infection transmitted through the public water supply.

BACKGROUND: Early in the spring of 1993 there was a widespread outbreak of acute watery diarrhea among the residents of Milwaukee. METHODS: We investigated the two Milwaukee water-treatment plants, gathered data from clinical laboratories on the results of tests for enteric pathogens, and examined ice made during the time of the outbreak for cryptosporidium oocysts. We surveyed residents with confirmed cryptosporidium infection and a sample of those with acute watery diarrhea consistent with cryptosporidium infection. To estimate the magnitude of the outbreak, we also conducted a survey using randomly selected telephone numbers in Milwaukee and four surrounding counties. RESULTS: There were marked increases in the turbidity of treated water at the city's southern water-treatment plant from March 23 until April 9, when the plant was shut down. Cryptosporidium oocysts were identified in water from ice made in southern Milwaukee during these weeks. The rates of isolation of other enteric pathogens remained stable, but there was more than a 100-fold increase in the rate of isolation of cryptosporidium. The median duration of illness was 9 days (range, 1 to 55). The median maximal number of stools per day was 12 (range, 1 to 90). Among 285 people surveyed who had laboratory-confirmed cryptosporidiosis, the clinical manifestations included watery diarrhea (in 93 percent), abdominal cramps (in 84 percent), fever (in 57 percent), and vomiting (in 48 percent). We estimate that 403,000 people had watery diarrhea attributable to this outbreak. CONCLUSIONS: This massive outbreak of watery diarrhea was caused by cryptosporidium oocysts that passed through the filtration system of one of the city's water-treatment plants. Water-quality standards and the testing of patients for cryptosporidium were not adequate to detect this outbreak.

Changes in population density and distribution of Ixodes dammini (Acari: Ixodidae) in Wisconsin during the 1980s.

Changes in the density and distribution of Ixodes dammini, Spielman Clifford, Piesman & Corwin were assessed in Wisconsin by examining hunter-killed deer for ticks in 1981 and 1989. Deer examination sites were distributed widely across the state and included 23 sites in 1981 and 15 sites in 1989; 10 sites were visited both years. Between 1981 and 1989, I. dammini became more abundant throughout its range, and I. dammini range expanded into the southwestern portion of Wisconsin. I. dammini was not found in the eastern one-third of the state. When compared with 1981, the 1989 survey revealed significant increases in the proportion of infested deer in the southwest (Arena), higher levels of infestation of individual deer (number of ticks per individual deer) in the central west (Bangor-W. Salem), and significantly less disparity between the proportions of infested male deer and infested female deer in the north (Spooner) compared with sites farther south. These results are consistent with a pattern of I. dammini range expansion from north to south, followed by an increase in population density in the colonized areas. Dermacentor albipictus Packard was present throughout the range of I. dammini and at sites in the northeastern quadrant of Wisconsin where I. dammini was not found. The range of D. albipictus did not change between the survey years, but its population density increased significantly at sites in the north. There is no evidence for interaction between the two tick species that might affect tick distribution or population density, nor can the greater number of I. dammini found in 1989 be attributed to increased tick activity because of warmer weather; temperatures were cooler in 1989 than 1981.

Antibodies to Borrelia sp. in wild foxes and coyotes from Wisconsin and Minnesota.

Serum samples from 93 red foxes (Vulpes vulpes) and nine gray foxes (Urocyon cinereoargenteus) trapped in Wisconsin and 23 coyotes (Canis latrans) trapped in Wisconsin and Minnesota were tested for antibodies to Borrelia sp. with an indirect fluorescent antibody test which used Borrelia burgdorferi as the whole-cell antigen. Seven red foxes (8%) and two coyotes (9%) had antibody titers greater than or equal to 1:64. All the positive samples were from areas known to be endemic for human Lyme disease. Implications for the epizootiology of Lyme borreliosis in wild canids are not well understood, but even if these species are not actual reservoirs of B. burgdorferi they could serve to increase the range of the vector and establish new endemic foci of the spirochete.

Susceptibility of the gray wolf (Canis lupus) to infection with the Lyme disease agent, Borrelia burgdorferi.

Four juvenile gray wolves (Canis lupus) were inoculated with live Borrelia burgdorferi. One received an intravenous inoculum, a second was inoculated subcutaneously, and two more were fed Peromyscus maniculatus sucklings which had earlier been inoculated with B. burgdorferi. The intravenously inoculated wolf developed a generalized lymphadenopathy and a persistent serum antibody titer to the spirochete which peaked at 1:512. Borrelia burgdorferi was visualized in liver sections of this wolf using direct immunofluorescent staining. The subcutaneously inoculated wolf showed a low and transient antibody response which peaked at 1:64, and manifested no clinical or postmortem abnormalities. The wolves which were fed inoculated mice showed no detectable antibody response. They were clinically normal throughout the project, and there were no detectable lesions at necropsy. Two control wolves were inoculated intravenously with formalin killed B. burgdorferi. Serum antibody titers of these controls peaked at 1:64 and 1:32, respectively, and fell to 1:16 by day 48 postinoculation. A survey of serum samples from 78 wild-trapped wolves from Wisconsin and Minnesota revealed that one was positive and another was suspect for B. burgdorferi infection based on presence of antibody to the spirochete. We conclude that the wolf is susceptible to infection by B. burgdorferi and that wolves are being infected in the wild.

Borreliosis in free-ranging black bears from Wisconsin.

Blood, kidney and tick samples were obtained from 18 hunter-killed black bears (Ursus americanus) from three sites in northern Wisconsin. A Borrelia sp., morphologically and antigenically similar to Borrelia burgdorferi, was isolated from the blood of two of the animals, and from the kidney of a third. Ixodes dammini and Dermacentor variabilis were found on the bears. This is the first report of borreliosis in the Ursidae, and of the primary vector of Lyme disease, I. dammini, from this host.