Distribution of Ehrlichia chaffeensis (Rickettsiales: Rickettsiaeceae) in Amblyomma americanum in southern Indiana and prevalence of E. chaffeensis--reactive antibodies in white-tailed deer in Indiana and Ohio in 1998.

To continue monitoring the prevalence and distribution of Ehrlichia chaffeensis (Rickettsiales: Rickettsiaeceae) in southern Indiana, a total of 498 Amblyomma americanum (L.) ticks (262 adults and 292 nymphs) was collected from five southern Indiana counties during May and June 1998. Ticks were pooled and examined for the presence of E. chaffeensis using nested polymerase chain reaction and primers specific for the 16S rRNA gene of E. chaffeensis. The average minimum infection rate for adult ticks collected in 1998 was 3.8% (ranging from 0 to 7.7% in various counties) as compared with previous average minimum infection rates of 1.6% in 1995 and 4.9% in 1997. None of the pools of A. americanum nymphs tested positive. In addition, blood samples were collected from 325 white-tailed deer taken in Indiana and 327 taken in Ohio in November 1998. Serum samples were tested for the presence of E. chaffeensis-like organisms reactive to antibodies using an indirect immunofluorescence assay (IFA). Antibodies were found in deer from six Indiana counties where infection rates ranged from 42.6 to 66.7% and in four Ohio countries where infection rates ranged from 4.4 to 25%. The results of this study reconfirm that E. chaffeensis is well established in southern Indiana and also provide the first evidence of E. chaffeensis-like organisms infecting white-tailed deer in Ohio, suggesting the need to survey Ohio ticks for the presence of Ehrlichia.

Infection rates of Amblyomma americanum (Acari: Ixodidae) by Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) and prevalence of E. chaffeensis-reactive antibodies in white-tailed deer in southern Indiana, 1997.

To monitor the percentage and stability of Ehrlichia chaffeensis-infected ticks in southern Indiana over time, pools of Amblyomma americanum (L.) ticks were screened for infection in southern Indiana for a 2nd time. Nested polymerase chain reaction (with 6% DMSO included only in the 2nd reaction) was performed on 920 ticks in pools of 5 individuals from 9 sites (5 sites previously examined and 4 new ones) in 6 counties. The average minimum infection rate for all sites for 1997 was 1.6%, lower than that of 4.9% previously observed for 1995. However, when only the 5 sites that were positive for infected ticks in 1995 were reexamined, the average minimum infection rate was even more disparate (1.4% in 1997 and 5.1% in 1995). To correlate the presence of infected ticks with the presence of exposed deer, which serve as a reservoir, dried blood samples collected from hunter-killed deer at 2 locations in southern Indiana were tested for E. chaffeensis-reactive antibodies using an indirect immunofluorescent assay. Antibodies were detected in 45 and 47% of 98 samples examined from the 2 stations. These data provide support to our previous report of a population of E. chaffeensis-infected A. americanum in southern Indiana and the high proportion of deer previously exposed to E. chaffeensis suggests a stable maintenance of E. chaffeensis in this tick-vertebrate zoonotic system.

Community health nurses' knowledge of Lyme disease: implications for surveillance and community education.

A statewide assessment was conducted to determine the general knowledge and professional practices about Lyme disease (LD) of local health department nurses. The study sample included 226 nurses practicing in 80 health departments in Indiana. Data were collected using a self-administered questionnaire and analyzed using group independent t tests. Findings showed that nurses were most knowledgeable about personal protection against LD and least knowledgeable about symptoms, case definition, and reporting criteria. Nonbaccalaureate degreed nurses scored significantly higher on questions about LD than the baccalaureate or master's prepared nurses. Results point to the need for better dissemination of LD information among public health nurses, expanded LD education for the public, and further development of LD surveillance activities.

Minimum infection rate of Ambylomma americanum (Acari: Ixodidae) by Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) in southern Indiana.

In 1994 and 1995, 8 cases of human monocytic ehrlichiosis were confirmed. These cases originated from southern counties where the putative tick vector Ambylomma americanum (L.) is well established. To confirm the presence of Ehrlichia chaffeensis in ticks in southern Indiana and to determine the minimum infection rate, specimens of A. americanum were collected from 5 counties (7 sites). Nucleic acid was isolated from 88 pools of ticks (430 individuals) using an optimized phenol/CTAB (cetyltrimethylammonium bromide) extraction procedure and subjected to polymerase chain reaction analysis using species-specific 16S rRNA gene bacterial primers. Twenty-one of 88 pools (a minimum of 21 of 430 individuals) were positive for the presence of E. Chaffeensis, yielding an average minimum infection rate of 4.9%. Minimum infection rates at individual sites ranged from 0 to 9.4%. These data extend the known distribution of the bacterium to 3 southern counties of Indiana and suggest a higher prevalence of E. chaffeensis than previously reported for Missouri, North Carolina, or Kentucky.

Spread of Ixodes scapularis (Acari:Ixodidae) in Indiana: collections of adults in 1991-1994 and description of a Borrelia burgdorferi-infected population.

Collection records for the adult black legged tick, Ixodes scapularis Say, in Indiana for the period 1991-1994 are presented and a new, established population of Borrelia burgdorferi-infected I. scapularis is described. The number of I. scapularis adults collected in Indiana increased progressively from 19 in 1991 to > 200 in 1994, and the number of Indiana counties reporting at least 1 adult increased from 13 to 29. Also, during this period, 4 countries in northwestern Indiana yielded > 10 specimens each, and B. burgdorferi-infected ticks were collected in 2 of these counties. An established population of I. scapularis, as evidenced by the presence of questing larvae, nymphs, and adults, was discovered in Jasper County in 1993. Twelve of 39 adults (31%) and 4 of 44 nymphs (9%) collected with cloth drags were infected with B. burgdorferi. Three of 49 (6%) white-footed mice, Peromyscus leucopus, collected from the site were also infected with B. burgdorferi. We believe that this focus was established at least 8 yr ago, and that a tick originating from this focus was responsible for a case of Lyme disease reported from this county in 1985.

Inability of Ixodes cookei and Amblyomma americanum nymphs (Acari: Ixodidae) to transmit Borrelia burgdorferi.

The vector competency of Ixodes cookei Packard and Amblyomma americanum (L.) for Borrelia burgdorferi was studied using Syrian hamsters. Ixodes dammini Spielman, Clifford, Piesman & Corwin were used as controls. Darkfield and immunofluorescent examinations of midgut diverticula revealed B. burgdorferi spirochetes in 32 of 36 (88.9%) I. dammini larvae, 5 of 36 (13.9%) I. cookei larvae, and 7 of 36 (19.4%) A. americanum larvae within 48 h after feeding on infected Syrian hamsters. B. burgdorferi were also observed in the midguts of 94 of 107 (87.8%) I. dammini nymphs that developed from the fed larvae. However, none of 30 I. cookei nymphs was positive for spirochetes and only 1 of 60 (1.7%) A. americanum nymphs was found positive for B. burgdorferi. Nymphs of each tick species, reared from larvae that had fed on infected hamsters, were allowed to feed on uninfected hamsters to determine their ability to transmit B. burgdorferi. Transmission was demonstrated only by I. dammini nymphs.

Collections of adult Ixodes dammini in Indiana, 1987-1990, and the isolation of Borrelia burgdorferi.

The collection records for Ixodes dammini Spielman, Clifford, Piesman & Corwin in Indiana are summarized for the period 1987-1990. In 1990, 13 of 729 deer examined were found to harbor adult I. dammini ticks. Eleven of these ticks were collected from 10 deer at a site in Newton County in northwestern Indiana. Borrelia burgdorferi spirochetes were isolated from a single female I. dammini tick collected from this site.

Ixodes dammini (Acari: Ixodidae) in Indiana.

Ixodes dammini Spielman, Clifford, Piesman and Corwin is reported from Indiana for the first time. Four specimens were taken from deer and one from a dog. All specimens are adult females and all were collected in 1987. The significance of this finding is discussed.

Lyme disease: an increasing health risk for school-age children.

Lyme disease, a bacterial infection with noticeable short-term and serious long-term consequences, is the most common tick-borne disease. First described in 1977, Lyme disease poses a significant health threat to school-age children exposed to the tick vector primarily in three specific regions of the United States. This article describes Lyme disease and its clinical signs and symptoms, and discusses the school nurse's role in identification, management, and prevention of this new health risk.

Species composition and feeding success of mosquitoes attracted to caged dogs in Indiana.

A field study using caged dogs in mosquito bait traps was conducted in eastcentral Indiana to determine the species composition of mosquitoes coming to feed. Fourteen species of mosquitoes from 5 genera were collected; Aedes trivittatus predominated. Feeding success rates were measured as the percentage of mosquitoes collected that had a fresh blood meal. The species having the highest rates were: Culex erraticus, Aedes stimulans and Ae. trivittatus. Aedes vexans and Cx. pipiens/restuans had markedly lower feeding success rates. A New Jersey light trap operated at the same site each year yielded a different species composition. Because of its propensity for feeding on dogs, Ae. trivittatus may be considered as a major potential vector of heartworm disease in dogs, even where it is one of several possible vector species present in abundance.

Trivittatus virus infections in wild mammals and sentinel rabbits in central Iowa.

A serological survey was conducted in Iowa to determine the prevalence rate of California group virus antibodies in sera of several vertebrate species. Serum specimens were assayed for infectivity-neutralizing antibody in a microneutralization system with baby hamster kidney cell culture. Of 77 sera assayed, 21 (27%) neutralized trivittatus (TVT) virus infectivity. The antibody prevalence rate was highest for eastern cottontail rabbits inasmuch as 46% (10/22) of the serum specimens form this species possessed neutralizing activity. Other vertebrate species having TVT virus antibody included the fox squirrel, 29% (7/24), opossum, 12% (3/25), and raccoon, 17% (1/6). One cottontail rabbit serum neutralized both TVT virus and Jamestown Canyon (JC) virus infectivity, and one opossum serum specimen neutralized JC virus. None of the vertebrate sera neutralized La Crosse, St. Louis encephalitis, or western equine encephalomyelitis virus infectivity. Trivittatus virus neutralizing antibody was detected in the sera of sentinel rabbits, and TVT virus was isolated from the blood collected from one of these sentinels shortly after the first population peak of adult Aedes trivittatus mosquitoes in 1973. The implications of these data and the possibility of trans-ovarial transmission of TVT virus in A. trivittatus are discussed.

Host preferences of Aedes trivittatus (Diptera: Culicidae) in central Iowa.

The vertebrate host preferences of Aedes trivittatus mosquitoes were studied to gain an insight into the possible hosts of trivittatus (TVT) virus (California encephalitis group) in Iowa. Engorged mosquitoes were collected with a Malaise trap and Dry Ice-baited CDC miniature light traps. The origin of mosquito blood meals was determined by the capillary tube precipitin test. Of 600 A. trivittatus blood meals tested, 409 (68.2%) reacted positively with anti-rabbit serum. The incidences of mosquitoes feeding on other vertebrate species ranged from 0.2% to 2.5%. The vertebrate host preferences of A. trivittatus suggest a close association between this mosquito species and the eastern cottontail rabbit (Sylvilagus floridanus) in central Iowa. Furthermore, the results indicate that the eastern cottontail rabbit may be an important host for TVT virus in Iowa.