Zoonotic pathogens in Ixodes scapularis, Michigan.To the Editor: Ixodes scapularis Ixodes scapularis Deer tick A tick with a 2-yr life cycle, and 3 feeding seasons; the cycle begins in spring with soil deposition of fertilized eggs; by summer, larvae emerge and imbibe a blood meal from small vertebrates–eg, white-footed mouse– , the black-legged tick black-legged tick see ixodes. , is the predominant vector of reportable human vectorborne disease in the United States. It transmits agents that cause Lyme borreliosis Lyme borreliosis Another name for Lyme disease. Mentioned in: Lyme Disease , human anaplasmosis, and human babesiosis babesiosis (bəbē'bēō`sĭs), tick-borne disease caused by a protozoan of the genus Babesia. Babesiosis most commonly affects domestic and wild animals and can be a serious problem in cattle. . I. scapularis--borne disease is becoming more frequent as this tick expands its range from tick-endemic foci in the northeastern and upper midwestern United States. Despite Michigan's proximity to large tick-endemic areas (Wisconsin and Minnesota to the west and Indiana to the south), active and passive surveillance data indicated that the only populations of I. scapularis established in the state before 2002 were in Menominee County in the Upper Peninsula (1,2). However, wildlife sampling and tick dragging in 2002-2003 suggested that I. scapularis had begun to invade southwestern Michigan (3), with nearby populations in northwestern Indiana (4) as the putative source. Because we suspected these invading ticks were bringing zoonotic Zoonotic A disease which can be spread from animals to humans. Mentioned in: Zoonosis pathogens into southwestern Michigan, we assessed pathogen prevalence within the state's invading and endemic I. scapularis populations. Over a 1.5-week period in April-May 2006, we collected adult I. scapularis by drag sampling at 3 recently invaded sites in southwestern Michigan and 2 tick-endemic sites in Menominee County. We targeted adult I. scapularis in the spring because this life stage has had 2 chances of becoming infected and because the adult questing peak in Michigan is greater in spring than fall (2,3). All collected ticks were bisected aseptically, and total DNA DNA: see nucleic acid. DNA or deoxyribonucleic acid One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. was extracted from half after overnight lysis lysis /ly·sis/ (li´sis) 1. destruction or decomposition, as of a cell or other substance, under influence of a specific agent. 2. mobilization of an organ by division of restraining adhesions. 3. (DNeasy Tissue Kit; QIAGEN, Valencia, CA, USA). We used 3 PCRs to assay for Borrelia burgdorferi Borrelia burg·dor·fe·ri n. A spirochete causing Lyme disease in humans. Borrelia burgdorferi The spirochete agent of Lyme disease, which contains several outer membrane proteins and a highly immunogenic flagellar , B. lonestari, and B. miyamotoi (5); Anaplasma phagocytophilum (6); and Babesia Babesia /Ba·be·sia/ (bah-be´ze-ah) a genus of protozoa found as parasites in red blood cells and transmitted by ticks; its numerous species include B. bige´mina, B. bo´vis, and B. spp., including Babesia microti Babesia mi·cro·ti n. A species of Babesia that causes babesiosis in humans, usually transmitted by the northern deer tick. Babesia microti and Babesia odocoilei (7). Borrelia-positive and Babesia-positive amplicons were purified and sequenced for species identification. Tick densities were highest overall at tick-endemic Menominee County sites; in southwestern Michigan, they were highest at those sites closest to the putative source of the Indiana invasion. We collected 28 adult and 1 nymphal nymph n. 1. Greek & Roman Mythology Any of numerous minor deities represented as beautiful maidens inhabiting and sometimes personifying features of nature such as trees, waters, and mountains. 2. I. scapularis and 2 adult Dermacentor variabilis Dermacentor var·i·a·bi·lis n. A tick that transmits tularemia and is the principal vector of Rocky Mountain spotted fever in the central and eastern US; the American dog tick. from tick-endemic sites. Of the adult I. scapularis, 17 (60.7%) were positive for B. burgdorferi, 4 (14.3%) were positive for A. phagocytophilum, and 2 (7.1%) were positive for Babesia odocoilei (Table). We also collected 91 adult and 10 nymphal I. scapularis and 5 adult D. variabilis from newly invaded sites. Of the adult I. scapularis, 43 (47.3%) were positive for B. burgdorferi, 1 (1.1%) was positive for A. phagocytophilum, and 4 (4.4%) were positive for Babesia odocoilei. All 4 Babesia odocoilei--positive ticks were co-infected with B. burgdorferi (this rate of co-infection was significantly greater than random expectation; p = 0.046, by Fisher exact test). Within the tick-endemic area, comparison with prior survey data (8) indicated that the B. burgdorferi infection rate in adult ticks increased from 31.3% in 1992 to 60.7% in the present survey (p<0.001, by Fisher exact test). A similar increasing trend was evident in the invasion area, where prevalence increased from 37.0% in 2002-2003 (at a collection site 5 km south of our southernmost site; [3]) to 47.3% in 2006. This latter trend was only marginally statistically significant due to small sample size and the short period between surveys (p = 0.046, by 1-tailed Fisher exact test). B. burgdorferi infection in I. scapularis has been reported in Michigan (1-3,8). To our knowledge, ours is the first report of A. phagocytophilum and Babesia odocoilei in ticks in Michigan; they are present in both the endemic and recently invaded populations. Similar infection rates for these pathogens have been reported in I. scapularis from Indiana (9). B. burgdorferi and A. phagocytophilum are human pathogens; Babesia odocoilei, an intraerythrocytic protozoan protozoan (prō'təzō`ən), informal term for the unicellular heterotrophs of the kingdom Protista. Protozoans comprise a large, diverse assortment of microscopic or near-microscopic organisms that live as single cells or in simple parasite maintained in transmission cycles in white-tailed deer white-tailed deer or Virginia deer Common reddish brown deer (Odocoileus virginianus), an important game animal found alone or in small groups from southern Canada to South America. , is not known to be pathogenic to humans (7). Several other Borrelia Borrelia A genus of spirochetes that have a unique genome composed of a linear chromosome and numerous linear and circular plasmids. Borreliae are motile, helical organisms with 4–30 uneven, irregular coils, and are 5–25 micrometers long and 0. and Babesia species (i.e., B. lonestari, B. miyamotoi-like spirochetes, and Babesia microti) from US ticks were not detected in our sample. I. scapularis nymphs, which are epidemiologically important (10), were not the focus of our sampling. However, several were collected, including some infected with B. burgdorferi, A. phagocytophilum, or both (Table). These data imply a risk for Lyme borreliosis and human anaplasmosis in areas endemic for and recently invaded by I. scapularis. For example, Lyme disease Lyme disease, a nonfatal bacterial infection that causes symptoms ranging from fever and headache to a painful swelling of the joints. The first American case of Lyme's characteristic rash was documented in 1970 and the disease was first identified in a cluster at incidence in the tick-endemic zone has increased significantly over the past 10 years (from 0.33 to 1.53 cases per 10,000 persons during 1997-2006; [r.sup.2] = 0.56, p = 0.01). Incidence in the invasion zone has been much lower (mean 0.03 cases per 10,000 persons over same period) but appears to be increasing. Further increases in tick population size, infection, and co-infection can be expected as the invasion continues (9). Thus, medical practitioners in southwestern Michigan should be aware of the changing increasing risk for tickborne diseases and consider disease resulting from these pathogens during diagnosis. Acknowledgments We thank M. Rosen, K. Boatman, and G. Hamer for field and laboratory assistance; H. Goethert and S. Telford III for providing positive control Babesia microti and Babesia odocoilei DNA; the private landowners in Menominee County for their cooperation; and the Michigan Department of Natural Resources The Michigan Department of Natural Resources is the agency of the state of Michigan charged with maintaining natural resources such as state parks, state forests, and recreation areas. for access to field sites. This study was supported by the Department of Fisheries and Wildlife, Michigan State University Michigan State University, at East Lansing; land-grant and state supported; coeducational; chartered 1855. It opened in 1857 as Michigan Agricultural College, the first state agricultural college. ; cooperative agreement no. CI00171-01 from the Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. (graduate assistantship as·sis·tant·ship n. An academic position that carries a stipend and usually involves part-time teaching or research, given to a qualified graduate student. to S.A.H.), and grant 4T35 RR017491-04 from the National Institutes of Health (fellowship to C.C.B.). References (1.) Walker ED, Stobierski MG, Poplar ML, Smith TW, Murphy AJ, Smith PC, et al. Geographic distribution of ticks (Acari: Ixodidae) in Michigan, with emphasis on Ixodes scapularis and Borrelia burgdorferi. J Med Entomol. 1998;35:872-82. (2.) Strand MR, Walker ED, Merritt RW. Field studies on Ixodes dammini Ixodes dam·mi·ni n. A species of Ixodes that is a vector of Lyme disease and human babesiosis in the United States. tick in the Upper Peninsula of Michigan The Upper Peninsula of Michigan is the northern of the two major land masses that comprise the U.S. state of Michigan. It is commonly referred to simply as the Upper Peninsula, the U.P., or Upper Michigan, and more casually as the land "above the Bridge". . Vector Control Bulletin of North Central States. 1992;1:11-8. (3.) Foster E. Ixodes scapularis (Acari: Ixodidae) and Borrelia burgdorferi in southwest Michigan: population ecology and verification of a geographic risk Geographic risk Risk that arises when an issuer issues policies concentrated within certain geographic areas, such as the risk of damage from a hurricane or an earthquake. model [master's thesis]. East Lansing (MI): Michigan State University; 2004. (4.) Pinger ping·er n. A device used underwater to produce pulses of sound, as for an echo sounder. pinger Noun a device that makes a pinging sound, esp. a timer Noun 1. RR, Timmons L, Karris K. Spread of Ixodes scapularis (Acari: Ixodidae) in Indiana: collections of adults in 1991-1994 and description of a Borrelia burgdorferi-infected population. J Med Entomol. 1996;33:852-5. (5.) Bunikis J, Garpmo U, Tsao J, Berglund J, Fish D, Barbour AG. Sequence typing reveals extensive strain diversity of the Lyme borreliosis agents Borrelia burgdorferi in North America and Borrelia afzelii in Europe. Microbiology. 2004;150: 1741-55. (6.) Zeidner NS, Burkot TR, Massung R, Nicholson WL, Dolan MC, Rutherford JS, et al. Transmission of the agent of human granulocytic ehrlichiosis human granulocytic ehrlichiosis: see ehrlichiosis. by Ixodes spinipalpis ticks: evidence of an enzootic en·zo·ot·ic adj. Prevalent among or restricted to animals of a specific geographic area. Used of a disease. n. An enzootic disease. enzootic peculiar to or present constantly in a location. See also endemic. cycle of dual infection with Borrelia burgdorferi in northern Colorado. J Infect Dis. 2000;182:616-9. (7.) Armstrong PM, Katavolos P, Caporale DA, Smith RP, Spielman A, Telford S III. Diversity of Babesia infecting deer ticks (Ixodes dammini). Am J Trop Med Hyg. 1998;58:739-42. (8.) Walker ED, Smith TW, DeWitt J, Beaudo DC, McLean RG. Prevalence of Borrelia burgdorferi in host-seeking ticks (Acari, Ixodidae) from a Lyme disease endemic area Endemic area A geographical region where a particular disease is prevalent. Mentioned in: Leprosy, Scrub Typhus in northern Michigan. J Med Entomol. 1994;31:524-8. (9.) Steiner FE, Pinger RR, Vann CN, Abley MJ, Sullivan B, Grindle N, et al. Detection of Anaplasma phagocytophilum and Babesia odocoilei DNA in Ixodes scapularis (Acari: Ixodidae) collected in Indiana. J Med Entomol. 2006;43:437-42. (10.) Stafford KC III, Cartter ML, Magnarelli LA, Ertel SH, Mshar PA. Temporal correlations between tick abundance and prevalence of ticks infected with Borrelia burgdorferi and increasing incidence of Lyme disease. J Clin Microbiol. 1998;36: 1240-4. Sarah A. Hamer, * Pamela L. Roy, * Graham J. Hickling, ([dagger]) Edward D. Walker, * Erik S. Foster, ([dagger]) Christina C. Barber, * and Jean I. Tsao * * Michigan State University, East Lansing, Michigan East Lansing is a city in the U.S. state of Michigan. The city is located directly east of Lansing, Michigan, the state's capital. Most of the city is within Ingham County, though a small portion lies in Clinton County. , USA; ([dagger]) University of Tennessee The University of Tennessee (UT), sometimes called the University of Tennessee at Knoxville (UT Knoxville or UTK), is the flagship institution of the statewide land-grant University of Tennessee public university system in the American state of Tennessee. , Knoxville, Tennessee, USA; and ([double dagger]) Michigan Department of Community Health, East Lansing, Michigan, USA Address for correspondence: Sarah A. Hamer, Department of Fisheries and Wildlife, Michigan State University, 13 Natural Resources Bldg, East Lansing, MI 48824, USA; email: hamer@msu.edu
Table. Prevalence of 3 pathogens in Ixodes scapularis ticks from 2
Michigan field sites, spring 2006 *
No. ticks infected or
co-infected (%)
No.
Site Life stage Ix. scapularis
E-1 A 16
E-2 A 12
N 1
I-1 A 4
N 2
I-2 A 18
N 8
I-3 A 69
All endemic sites A 28
N 1
All invaded sites A 91
N 10
No. ticks infected or
co-infected (%)
Borrelia Anaplasma
Site burgdorferi phagocytophilum
E-1 9 (56.3) 1 (6.3)
E-2 8 (66.7) 3 (25.0)
1 (100.0) 0
I-1 2 (50.0) 0
0 1 (50.0)
I-2 9 (50.0) 0
2 (25.0) 1 (12.5)
I-3 32 (46.4) 1 (1.4)
All endemic sites 17 (60.7) 4 (14.3)
1 (100) 0
All invaded sites 43 (47.3) 1 (1.1)
2 (20.0) 2 (20.0)
No. ticks infected or
co-infected (%)
Babesia B. burgdorferi and
Site odocoilei A. phagocytophilum
E-1 1 (6.3) 1 (6.3)
E-2 1 (8.3) 1 (8.3)
0 0
I-1 0 0
0 0
I-2 1 (5.6) 0
0 1 (12.5)
I-3 3 (4.3) 0
All endemic sites 2 (7.1) 2 ([dagger]) (7.1)
0 0
All invaded sites 4 (4.4) 0
0 1 ([dagger]) (10.0)
No. ticks infected or
co-infected (%)
B. burgdorferi and
Site B. odocoilei
E-1 0
E-2 1 (8.3)
0
I-1 0
0
I-2 1 (5.6)
0
I-3 3 (4.3)
All endemic sites 1 ([dagger]) (3.6)
0
All invaded sites 4 ([double dagger]) (4.4)
0
* E, endemic site; A, adult: N, nymph; I, invaded site.
([dagger]) Nonsignificant level of co-infection; p = 0.378-0.640,
by Fisher exact test.
([double dagger]) Significant level of co-infection; p = 0.046,
by Fisher exact test.
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