Forest and surface water as predictors of Borrelia burgdorferi and its vector Ixodes scapularis (Acari: Ixodidae) in Indiana.

The objective of this study was to assess whether the distribution of Borrelia burgdorferi, the causative agent of Lyme disease, and its vector tick Ixodes scapularis Say (Acari: Ixodidae) across Indiana is influenced by large-scale landscape features, specifically the proportion of forest within the surrounding landscape and the distance to water features such as lakes and major streams. Hunter-killed deer were checked for ticks in designated check-stations in the opening firearm hunting season between 2005 and 2007. Hunting locations for approximately 3,600 deer were used in ArcGIS (ESRI, Redlands, CA) to examine the influence of forest and water features in the surrounding area on the occurrence of the tick and bacteria. In total, 82 of the 92 (89%) Indiana counties were sampled from 2005 to 2007. The proportion of tick-infested deer was 13.6, 15.8, and 25.5% in these years, respectively. There was a significant nonlinear response for I. scapularis to forest cover in 1 yr that indicated a greater probability of this tick presence at intermediate levels of forest area. Infested does were harvested in significantly more forested areas than bucks. No significant correlation was found neither between levels of forest area and B. burgdorferi nor between water bodies and both organisms.

Ultrastructure of Babesia WA1 (Apicomplexa: Piroplasma) during infection of erythrocytes in a hamster model.

Babesia Washington-1 (WA1) is a newly identified intraerythrocyte infectious agent of human babesiosis in the western United States. The purpose of the present study is to describe the ultrastructural changes in affected erythrocytes during the infectious process in a susceptible animal model, the golden Syrian hamster. Two, 1-mo-old female hamsters were inoculated intraperitoneally (i.p.) with 1.8 x 10(9) Babesia WA1-infected erythrocytes originally isolated from a human case and serially passaged in hamsters. Saphenous vein blood samples (20 microl) were collected at 0, 24, 36, 48, 60, 72, 84, and 96 hr postinoculation (PI). Parasitemia was determined at each time interval by quick staining of blood smears showing 0, 2.5, 5, 10, 12.5, 22.5, 70, and almost 100% parasitemic erythrocytes at the corresponding PI time interval, respectively. Animals showed weakness and dehydration 72 hr PI inoculation, and were killed by 96 hr PI. Selected blood samples from 0, 24, 48, 72, and 96 hr were fixed in cacodylate buffer, dehydrated in ethanol gradients, resin embedded, and then thin sectioned and stained with uranyl acetate and lead citrate for transmission electron microscopy or gold-coated for scanning electron microscopy (SEM). Shape and surface membrane changes in erythrocytes were demonstrated by SEM and were more evident at 72 and 96 hr PI. Infected erythrocytes underwent changes in shape 24 hr PI, from few protrusions to several perforations, some of them resembling a "swiss cheese" appearance 96 hr PI. Several erythrocytes had irregular surface membranes and Babesia WA1 organisms were seen at different stages of development within erythrocytes, from single trophozoites to several merozoites (young trophozoites), some of them dividing to form typical tetrads. In general, Babesia WAI induced severe morphological changes in the erythrocytes, and these changes were more evident in almost all infected cells 96 hr PI.

Gestational attenuation of Lyme arthritis is mediated by progesterone and IL-4.

Infection of different strains of laboratory mice with the agent of Lyme disease, Borrelia burgdorferi, results in arthritis, the severity of which has been correlated with the dominance of Th1 cytokines. In this study, we demonstrate that changes in B. burgdorferi-specific immunologic responses associated with pregnancy can alter the outcome of Lyme arthritis in mice. Whereas nonpregnant female C3H mice consistently developed severe Lyme arthritis, pregnant mice had a marked reduction in arthritis severity that was associated with a slight reduction in IFN-gamma and markedly increased levels of IL-4 production by B. burgdorferi-specific T cells. Similar reductions in arthritis severity and patterns of cytokine production were observed in nonpregnant, progesterone-implanted mice. Ab neutralization of IL-4 in progesterone-implanted mice resulted in severe arthritis. Our results are consistent with the known shift toward Th2 cytokine expression at the maternal-fetal interface, and are the first to show a pregnancy-related therapeutic effect in an infectious model.

Effects of heat stress on the antimicrobial drug resistance of Escherichia coli of the intestinal flora of swine.

The effects of heat stress on the antimicrobial drug resistance of Escherichia coli of the intestinal tract of swine were studied in animals from a farm that had not been supplementing antimicrobials in feed for the past 10 years. In one study, 10 finisher hogs were heat stressed (34 degrees C) for 24 h. Antimicrobial resistance levels after stress were significantly higher (P < 0.05) when compared with pre-stress levels for amikacin, ampicillin, cephalothin, neomycin and tetracycline from faecal samples. This high level of resistance persisted to slaughter that occurred at 10 days post-stress for most of the antimicrobials mentioned. In a second study, samples of different sections of the gastrointestinal tract were collected after heat stress and compared with control, non-stressed animals. Results indicated that E. coli which colonized the ileum and caecum had a higher level of resistance to ampicillin and tetracycline than the E. coli which colonized the colon and rectum. When animals were exposed to heat stress, resistance to ampicillin and tetracycline of E. coli in the lower digestive tract increased (P < 0.05) to a level similar to that observed in the ileum and caecum. Based on these findings, an investigation was made to test the hypothesis that (a) an increase in intestinal motility increases shedding of resistant E. coli and (b) heat stress induces a reduction in intestinal transit time in swine. For each study, two groups of three, randomly selected finisher hogs each were formed (treated and control groups). In study (a), induction of increased motility and peristalsis was obtained using an intramuscular injection of the cholinergic drug neostigmine methylsulphate. Escherichia coli isolates were obtained from the ileum, caecum, colon and rectum after animals were slaughtered. A higher level of ampicillin-resistant E. coli was found in the caecum (40%) than in other segments of the intestinal tract. In treated animals, level of resistance increased for organisms from the colon and rectum. Similar results were obtained for tetracycline resistance. In study (b), intestinal transit time was measured using chromium-EDTA as a marker. Swine were euthanized and samples were collected throughout the intestinal tract (duodenum to rectum) 8 h after administration of the marker to control and heat-stressed animals. Results indicated a reduced transit time for the stressed group. These findings corroborate the initial hypothesis that an outflow of resistant organisms moves from the upper tract (ileum and caecum) to the lower tract (colon and rectum).

A polymorphic multigene family encoding an immunodominant protein from Babesia microti.

Human babesiosis in the United States is caused predominantly by Babesia microti, a tick-transmitted blood parasite. Improved testing methods for the detection of infection with this parasite are needed, since asymptomatic B. microti infection represents a potential threat to the blood supply in areas where B. microti is endemic. We performed immunoscreening of an expression library of genomic DNA from a human isolate of B. microti (strain MN1). Among 17 unique immunoreactive clones, we identified 9 which represent a related family of genes with little sequence homology to other known sequences but with an architecture resembling that of several surface proteins of Plasmodium. Within this family, a tandem array of a degenerate six-amino-acid repeat (SEAGGP, SEAGWP, SGTGWP, SGTVGP) was found in various lengths between relatively well conserved segments at the N and C termini. In order to examine within-clone variation, we developed a PCR protocol for direct recovery of a specific bmn1-6 homologue directly from 30 human blood isolates, 4 corresponding hamster isolates, and 5 geographically corresponding Peromyscus leucopus (white-footed mouse) isolates. Isolates from the hamsters had the same sequences as those found in the corresponding human blood, suggesting that genetic variation of bmn1-6 does not occur during passage. However, clones from different patients were often substantially different from each other with regard to the number and location of the degenerate repeats within the bmn1-6 homologue. Moreover, we found that strains that were closely related geographically were also closely related at the sequence level; nine patients, all from Nantucket Island, Mass., harbored clones that were indistinguishable from each other but that were distinct from those found in other northeastern or upper midwestern strains. We conclude that considerable genetic and antigenic diversity exists among isolates of B. microti from the United States and that geographic clustering of subtypes may exist. The nature of the bmn1-6 gene family suggests a mechanism of antigenic variation in B. microti that may occur by recombination, differential expression, or a combination of both mechanisms.

Effects of cold stress on the antimicrobial drug resistance of Escherichia coli of the intestinal flora of swine.

Faecal samples were initially collected from pigs of different age groups, over periods considered to be seasonally normal and stable (baseline), and during times in which drastic drops in environmental temperature (cold stress) occurred. Baseline bacterial resistance to ampicillin and tetracycline were significantly higher (P < 0.05) in younger than in older pigs. Also, when animals were exposed to excessively cold conditions, there was a significant (P < 0.05) increase in ampicillin and tetracycline resistance in Escherichia coli for animals of all age groups. These results may indicate that factors other than feeding or use of antibiotics may play a role in establishing or maintaining the antibiotic resistance microflora of pigs, especially in those operations where animals are maintained outdoors, with minimal protection against extreme weather conditions.

Differential effects of infection with a Babesia-like piroplasm, WA1, in inbred mice.

A newly identified intraerythrocytic Babesia-like organism, WA1, and its relatives were recently shown to be infectious for humans in the western United States. The purpose of the present study was to determine the susceptibilities of selected mouse genotypes to WA1 infection in an attempt to develop a murine model of the human disease. Several mouse strains were inoculated intraperitoneally with various passages of WA1-parasitized erythrocytes. Parasitemia was evaluated by blood smears and by PCR with blood samples collected at various intervals after inoculation. Hematologic parameters were monitored in blood samples at all intervals. C57BL/6 and C57BL/10 mice exhibited mortality rates of <10%. BALB/cJ, CBAJ, and 129/J mice had higher peak parasitemias than did C57BL mice, with mortality rates of 40, 50, and 50%, respectively. A/J, AKR/N, C3H, and DBA/1J mice also had higher peak parasitemia and mortality rates (>95%). An F1 cross of C57BL/6 (resistant) and C3H.RKK (susceptible) mice had a mortality rate similar to that of the resistant parental strain. Histopathology of BALB/cJ and C3H mice at 9 and 14 days after inoculation revealed erythrophagocytosis and deposition of an iron-negative pigment in multiple organs. Morbidly ill C3H mice at 14 days had severe pulmonary edema, hemoglobinuria, and glomerulonephritis.

The epidemiology of rodent and lagomorph rabies in Maryland, 1981 to 1986.

Records from the Maryland Public Health Department were screened for confirmed rodent and lagomorph rabies between 1981 and 1986. Questionnaires were designed for collection of information about events that led to the exposure of human and/or domestic animals to rabid rodent or lagomorphs. These species comprised 1.2% of all the reported rabies in the state. Woodchucks (Marmota monax) constituted 80.0% of all the reported rodent/lagomorph rabies cases in Maryland. The majority showed aggressive behavior (55.0%). Woodchucks exposed 15 persons (75.0% of all the exposures by rodents/lagomorphs). Domestic animal and human rabies exposure due to rodents and lagomorphs represents a small but significant number of the total exposure to rabid animals.