Transmission of a Freshwater Isolate of Ichthyophonus (Clade C) to Two Marine Fish Species.

The ingestion of infected prey is the most recognizable mode of transmission for Ichthyophonus, but because this mode of transmission is unidirectional from small prey fish to larger predators, it cannot sustain the parasite within or among populations nor does it explain transmission to planktivores. Recently, waterborne transmission was demonstrated in cultured Rainbow Trout Oncorhynchus mykiss, which could explain how the parasite is transmitted without piscivory. However, it is possible that this is an adaptation to aquaculture conditions, and may not occur among wild fish. To address this question, experiments were conducted to determine if a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species, as well as if transmission is possible between different marine species. Pacific Staghorn Sculpins Leptocottus armatus were fed a freshwater isolate of Ichthyophonus (clade C) and then housed with susceptible sentinel Rock Soles Lepidopsetta bilineata. Ninety two percent of the orally exposed sculpins and 30% of the sentinel soles were Ichthyophonus-positive at the end of the study, with 0% infected controls. These results demonstrate that a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species and can be transmitted in seawater in the absence of piscivory. It also provides a plausible mechanism for transmission to small prey fish and planktivores, as well as within a population of piscivores when infected prey is not available.

[Possible influence of genetic polymorphism in the area of GSTs genes on the serum PCB level]. / Mozný vplyv génového polymorfizmu v oblasti GSTs génov na sérovú hladinu polychlorovaných bifenylov (PCB).

OBJECTIVE: To find out whether the serum PCB level depends on genetic polymorphism in the area of GSTs genes. MATERIAL AND METHODS: In the group of 147 men (112 with an average age of 59.1 ± 10.1 and serum PCB level > 1,000 ng/ g lipid -  PCB1, and 35 with an average age of 56.2 ± 12.9 and serum PCB level < 700 ng/ g lipid -  PCB2), the PCR RLFP analysis of DNA was used to determine the genetic polymorphism in the area of GSTs genes. RESULTS: As regards PCB, an association was found between serum PCB concentrations and the null genotype of GSTT1 gene. Men above the median PCB levels displayed, with significantly greater frequency, the null genotype GSTT1 compared to men below the median PCB levels, both in the PCB1 set and in the PCB2 set. In the PCB1 set, the presence of the null genotype GSTT1 increased the risk of high PCB levels 11- fold, in the PCB2 set 4- fold (p < 0.001). In the PCB2 set, an association was also discovered between GSTP1 Val/ Val genotype and higher PCB levels. The risk of high PCB levels in the individuals with the Val/ Val genotype was 5- fold higher than in the carriers of the Ile allele (p < 0.001). In neither set was the GSTM1 genotype associated with serum PCB concentrations. CONCLUSION: The association between high PCB levels and the GSTT1 null and GSTP1 Val/ Val suggests that harmful effects depend not only on the intake amounts of PCB but also on the ability of the organism to detoxify these substances. Individuals living in the same environment are therefore at different risks of developing a disease when exposed to PCB. Polymorphism in the area of GSTTl gene (GSTT1 null) could be a potential genetic risk marker.

Toxicity assessment of sediments from three European river basins using a sediment contact test battery.

The toxicity of four polluted sediments and their corresponding reference sediments from three European river basins were investigated using a battery of six sediment contact tests representing three different trophic levels. The tests included were chronic tests with the oligochaete Lumbriculus variegatus, the nematode Caenorhabditis elegans and the mudsnail Potamopyrgus antipodarum, a sub-chronic test with the midge Chironomus riparius, an early life stage test with the zebra fish Danio rerio, and an acute test with the luminescent bacterium Vibrio fischeri. The endpoints, namely survival, growth, reproduction, embryo development and light inhibition, differed between tests. The measured effects were compared to sediment contamination translated into toxic units (TU) on the basis of acute toxicity to Daphnia magna and Pimephales promelas, and multi-substance Potentially Affected Fractions of species (msPAF) as an estimate for expected community effects. The test battery could clearly detect toxicity of the polluted sediments with test-specific responses to the different sediments. The msPAF and TU-based toxicity estimations confirmed the results of the biotests by predicting a higher toxic risk for the polluted sediments compared to the corresponding reference sediments, but partly having a different emphasis from the biotests. The results demonstrate differences in the sensitivities of species and emphasize the need for data on multiple species, when estimating the effects of sediment pollution on the benthic community.

High prevalence of prediabetes and diabetes in a population exposed to high levels of an organochlorine cocktail.

AIMS/HYPOTHESIS: A heavily polluted area of Eastern Slovakia was targeted by the PCBRISK cross-sectional survey to search for possible links between environmental pollution and both prediabetes and diabetes. METHODS: Associations of serum levels of five persistent organic pollutants (POPs), namely polychlorinated biphenyls (PCBs), 2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), 2,2'-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (p,p'-DDT), hexachlorobenzene (HCB) and beta-hexachlorocyclohexane (beta-HCH), with prediabetes and diabetes were investigated in 2,047 adults. Diabetes and prediabetes were diagnosed by fasting plasma glucose in all participants and by OGTT in 1,220 compliant participants. RESULTS: Our population was stratified in terms of individual POPs quintiles and associations between environmental pollution, prediabetes and diabetes were investigated. Prevalence of prediabetes and diabetes increased in a dose-dependent manner, with individuals in upper quintiles of individual POPs showing striking increases in prevalence of prediabetes as shown by OR and 95% CI for PCBs (2.74; 1.92-3.90), DDE (1.86; 1.17-2.95), DDT (2.48; 1.77-3.48), HCB (1.86; 1.7-2.95) and beta-HCH (1.97; 1.28-3.04). Interestingly, unlike PCBs, DDT and DDE, increased levels of HCB and beta-HCH seemed not to be associated with increased prevalence of diabetes. Nevertheless, individuals in the 5th quintile of the variable expressing the cumulative effect of all five POPs (sum of orders) had a more than tripled prevalence of prediabetes and more than six times higher prevalence of diabetes when compared with the 1st referent quintile. CONCLUSIONS/INTERPRETATION: Increasing serum concentrations of individual POPs considerably increased prevalence of prediabetes and diabetes in a dose-dependent manner. Interaction of industrial and agricultural pollutants in increasing prevalence of prediabetes or diabetes is likely.

Experimental infection of domestic cats (Felis domesticus) with Cytauxzoon manul from Pallas' cats (Otocolobus manul).

In a random, blind study, six domestic cats were assigned to two treatment groups that received either sterile water or dexamethasone by subcutaneous injection prior to intravenous inoculation with Pallas' cat (Otocolobus manul) blood infected with Cytauxzoon manul. A seventh domestic cat served as a control and was inoculated only with sterile water. Cats were monitored for clinical signs consistent with cytauxzoonosis, and periodically screened for hemoparasitemia. All domestic cats (6/6) that received Pallas' cat blood infected with C. manul developed a low but detectible parasitemia by 9 days post-inoculation, yet remained clinically healthy. All domestic cats (7/7) were subsequently challenged with Cytauxzoon felis and developed clinical signs typical of cytauxzoonosis within 5 days post-challenge. Affected animals were euthanized and cytauxzoonosis was confirmed by histopathology. While inoculation of domestic cats with Pallas' cat blood infected with C. manul induced a parasitemia, it did not cause disease or provide protection against challenge with C. felis. Further studies are warranted to determine the potential for interspecies transmission and disease with C. manul.

Simple solid-phase extraction method for determination of polychlorinated biphenyls and selected organochlorine pesticides in human serum.

A simple off-line solid-phase extraction (SPE) method for isolation of polychlorinated biphenyls (PCBs) and selected organochlorine pesticides (OCPs) from human serum has been developed. The procedure includes denaturation of serum proteins by a mixture of water-1-propanol, application of the sample by aspiration twice repeatedly through the SPE column and elution with a mixture of n-hexane-dichlormethane. After final clean-up the compounds of interest were analysed by gas chromatography with micro-electron capture detection (GC-microECD). The recoveries achieved for PCB congeners using spiked porcine serum samples were 99-120% and for OCPs 88-115%. Relative standard deviations (RSD) ranged from 3 to 7%. The method was applied to real human serum samples and the recoveries of analytes in the serum were proportionally recalculated considering the recovery of the internal standard PCB-174. PCB-103 served as a syringe standard to correct volume of samples analysed. The aim of this study was to develop an effective off-line SPE procedure by optimization of existing SPE methods to supply laborious, solvent- and time-consuming liquid-liquid extraction (LLE) in routine analytical process.

Prevalence and spatial distribution of intraerythrocytic parasite(s) in Puget Sound rockfish (Sebastes emphaeus) from the San Juan Archipelago, Washington (USA).

Two morphologically distinct forms of an intraerythrocytic parasite(s) were detected by microscopic observation of Giemsa-stained blood films in 45.7% of 119 rockfish (Sebastes emphaeus) from the San Juan Archipelago (Washington State, U.S.A.). Infection prevalence for both forms was 53% in males, 44% in females, and 33% in fish of undetermined gender. A binucleate "ring-stage" was present at all 4 geographic sites, with a mean prevalence of 45.7%, while mean prevalence of a larger gamont-like form from the same sites was 5.1%. The relationship of the 2 forms to each other could not be determined. Neither schizogony nor binary fission was evident in any of the infected erythrocytes and the parasites contained no obvious pigment. The possibility of the 2 morphologic forms being 2 distinct species is supported by the observation that no difference in parasitemia was seen in the binucleate form among sites (1.6-1.9%), while parasitemia of the gamont-like form varied significantly among sites, ranging from a high of 4% to a low of 0.1%. Taxonomic status of either form could not be determined at this time based on limited existing morphologic data.

Sequence variation of the ribosomal DNA second internal transcribed spacer region in two spatially-distinct populations of Amblyomma americanum (L.) (Acari: Ixodidae).

Sequence analysis of the ribosomal DNA second internal transcribed spacer (ITS 2) region in 2 spatially distinct populations of Amblyomma americanum (L.) revealed intraspecific variation. Nucleotide sequences from multiple DNA extractions and several polymerase chain reaction amplifications of eggs from mixed-parentage samples from both populations of ticks revealed that 12 of 1,145 (1.0%) sites varied. Three of the 12 sites of variation were distinct between the 2 A. americanum populations, which corresponded to a rate of 0.26%. Phylogenetic analysis based on ITS 2 sequences provided strong support (i.e., bootstrap value of 80%) that wild A. americanum clustered into a distinguishable group separate from those derived from colony ticks.

A new species of Cytauxzoon from Pallas' cats caught in Mongolia and comments on the systematics and taxonomy of piroplasmids.

DNA was extracted and the 18S ribosomal RNA gene was amplified and sequenced from the blood of 2 Pallas' cats (Otocolobus manul) infected with small intraerythrocytic piroplasms. Sequences of the parasite were found to be identical with that of a previously reported Cytauxzoon-like piroplasm from a Pallas' cat. Phylogenetic analyses of the parasite DNA sequences obtained from the 3 Pallas' cats to other piroplasms revealed a sister group relationship to C. felis. The mean corrected percent sequence divergence between the Pallas' cat parasite and C. felis was 1.490%, which is greater than that for most other piroplasms in which species status has been accepted. On the basis of the sequence variation, we propose to name the Pallas' cat parasite C. manul. Phylogenetic analyses of C. manul also revealed a close relationship with the Spanish Cytauxzoon-like isolate because they exhibited only 0.389% sequence divergence, yet these sequences exhibit a mean of 1.690% sequence divergence from the New World isolate of C. felis. Our phylogenetic analyses also revealed several taxonomic problems that have impeded the development of a classification that accurately reflects evolutionary history of piroplasms. As currently arranged, Babesia and Theileria are paraphyletic taxa and are in need of reorganization.

Experimental infection of adult and juvenile coyotes with domestic dog and wild coyote isolates of Hepatozoon americanum (Apicomplexa: Adeleorina).

Each of five adult and four juvenile coyotes (Canis latrans) was exposed to an oral dose of 50 Hepatozoon americanum oocysts recovered from Amblyomma maculatum ticks that previously fed on either naturally infected domestic dogs (Canis familiaris) or naturally infected wild coyotes. All coyotes exposed to H. americanum became infected, regardless of isolate source, and all exhibited mild to moderate clinical disease that simulated American canine hepatozoonosis in naturally infected dogs. At 100 days postexposure, parasitemia was greater in juvenile than adult coyotes (0.9% and 0.3%, respectively); radiographic imaging of femurs revealed moderate exostosis in all juveniles and mild to moderate new bone growth in four of five (80%) adult coyotes. Gross postmortem analysis of bone lesions demonstrated variation between age groups of coyotes but not between isolates of H. americanum. Microscopic evaluation of skeletal muscle revealed that parasite-induced lesions were significantly more numerous (t = 5.0, df = 7, P = 0.001) in juvenile than adult coyotes. Results of this study indicate that juvenile and adult coyotes are equally susceptible to experimental infection with H. americanum isolated from domestic dog and wild coyote sources. The age of coyotes at the time of exposure, and possibly the number of H. americanum oocysts ingested, might influence morbidity and mortality, but it appears that both adult and juvenile coyotes could be reservoirs of H. americanum.

Feline cytauxzoonosis.

Cytauxzoon felis is a protozoan hemoparasite of wild and domestic cats. In domestic cats, it causes severe clinical disease with high mortality.

There are at least three genetically distinct small piroplasms from dogs.

The 18S nuclear subunit ribosomal RNA (18S rRNA) gene of small piroplasms isolated from dogs from Okinawa (Japan), Oklahoma, North Carolina, Indiana, Missouri, and Alabama, was isolated and sequenced. Phylogenetic analysis of these sequences and comparisons with sequences from other Babesia, Cytauxzoon, and Theileria species revealed that all canine small babesial isolates, with the exception of isolates from California and Spain, were placed in a group containing the Babesia spp. sensu stricto. Within the Babesia spp. sensu stricto, there was support for separating the small canine piroplasms from the large canine piroplasm, Babesia canis. The isolate from California was in a distinct phylogenetic clade, closely related to babesial isolates from wildlife and humans from the Western US. The canine isolate from Spain was closely related to Babesia microti. These results suggest that there are multiple small piroplasm species in dogs. The isolates from the Midwestern and Eastern US and the one from Japan probably represent a single species with wide geographic distribution.

Increased thyroid volume and prevalence of thyroid disorders in an area heavily polluted by polychlorinated biphenyls.

OBJECTIVE: To evaluate whether long-term exposure to heavy environmental pollution with polychlorinated biphenyls (PCBs) could result in impairment of thyroid status as evaluated by an epidemiological field survey. METHODS: Thyroid volume (ThV) was measured by ultrasound in 238 employees of a factory (EMP) which previously produced PCBs and 454 adolescents from the surrounding area polluted by PCBs. Controls (C) were 572 adults and 965 adolescents from much less polluted areas. In the 238 EMP and various numbers (shown in parentheses) of adult C the levels of thyroid-stimulating hormone (TSH) (n = 498), thyroxine (n = 498), thyroglobulin (n = 278) and thyroid antibodies (anti-peroxidase (TPO Ab), n= 517; anti-thyroglobulin (Tg Ab), n=455; anti-TSH receptor (TSHR Ab), n=238) were estimated in serum, while only TSH and TPO Ab were measured in 269 and 171 adolescents from polluted and control areas respectively. In several subjects in whom thyroid disease was suspected, total tri-iodothyronine or free thyroxine and tri-iodothyronine were measured. In a total of 362 adults and adolescents the urinary iodine was estimated. RESULTS: Using the Mann-Whitney test, ThV in EMP (mean+/-S.E. = 18.85+/-0.69 ml, median= 17.3 ml, upper quartile=22.9 ml, n=238) was significantly higher (P< 0.001) than that in C (13.47+/-0.48 ml, 11.5 ml, 15.3 ml, n = 486 respectively). Similarly, ThV in adolescents from the polluted area (9.37+/-0.17 ml, 8.9 ml, 11.0 ml, n = 454 respectively) was significantly higher (P< 0.001) than that in C (8.07+/-0.10 ml, 7.6 ml, 9.6 ml, n = 965 respectively). In adults, a significantly increased prevalence of TPO Ab (P<0.05) was found (using the chi-square test) in EMP women of all ages (54/190) vs C women (70/282), in EMP women aged 31-50 years (40/117 vs 70/282 respectively) and those aged 41- 50 years (28/77 vs 54/215 respectively). Compared with C, there was also a higher prevalence of Tg Ab in EMP women aged 31-60 years (36/169 vs 50/342 respectively) and of TSHR Ab (P< 0.001) in the group of EMP men and women (25/238) vs sex- and age-matched C (6/238). No difference between EMP and C was found in the level of thyroxine (mean+/-S.D = 116.1+/-31.2 nmol/l, n = 238 vs 112.2+/-37.0 nmol/l, n = 460 respectively), TSH in the range 0.1-4.5 mU/l(1.56+/-0.86 mUl/l, n = 219 vs 1.51+/-0.84 mU/l, n = 460 respectively), prevalence of TSH >4.5 (14/238 vs 28/498 respectively) and <0.1 mU/l(5/238 vs 10/498 respectively). The prevalence of individuals without any defined clinical or laboratory signs of thyroid disorders among EMP who had worked in the factory for 21-35 years (43/128, 33.6%) was significantly lower than that in twice as many matched C (118/256, 46.1%, P< 0.025) or in EMP who had worked for only 11-20 years (36/73, 49.3%, P< 0.05). In adolescents, no difference was found in the prevalence of TPO Ab or TSH >4.5 mU/l between the polluted (17/269, 6.3%, and 2/243, 0.8% respectively) and C areas (15/171, 8.5% and 4/140, 2.8% respectively). The median values of urinary iodine were in the optimal range (microg per dl/number of cases) and about the same in polluted (12.6/90 and 11.4/55) and C areas (14.1/80, 13.2/82 and 13.4/55). CONCLUSIONS: Since iodine intake in Slovakia is considered sufficient as a result of 45 years of well-monitored iodine prophylaxis, the increased ThVand prevalence of thyroid disorders in the polluted areas presumably results from long-term exposure to toxic substances rather than from a difference in life-long iodine intake. The increased prevalence of some thyroid antibodies may be related to the known immunomodulatory effects of PCBs.

Serological survey for Lyme disease in domestic dogs and white-tailed deer from Oklahoma.

Sera from 223 randomly selected dogs and 489 white-tailed deer (Odocoileus virginianus) were tested for antibodies to Borrelia burgdorferi using an indirect kinetic ELISA. Dog samples were obtained in 1989 whereas deer samples were obtained between 1975 and 1990. Ten known negatives and two known positives from each group were run on each plate as controls. Samples showing mean mOD values above the mean of negatives + 3 SD were considered positive. Twenty-six dog (11.7%) and 22 deer (4.5%) samples were positive. Deer reactors were first detected among 1978 samples. Reactive deer were from central and eastern Oklahoma whereas reactive dogs were mostly from central Oklahoma. Confirmed human cases between 1986 and 1989 were distributed throughout the state, thus showing no correlation with either deer or dog results.

American canine hepatozoonosis. An emerging disease in the New World.

Hepatozoon canis was first described from dogs in 1905 in India and Rhipicephalus sanguineus was identified as the vector. Dogs on the Texas Gulf Coast were recognized in 1978 to have hepatozoonosis, and it was thought that H. canis had entered the New World. Later, it was realized that American canine hepatozoonosis (ACH) is more debilitating than its Old World counterpart, often resulting in death. When the malady and parasite were characterized, a new species, H. americanum, was described, in 1997. Phylogenetic analysis, based on 18S rRNA gene sequence and classical taxonomic features, revealed that the two dog parasites are closely related. Amblyomma maculatum, the Gulf Coast tick (GCT), has been demonstrated to be an excellent vector; nymphal ticks were readily infected and oocysts from newly molted adults were uniformly infectious for dogs. The merogonic cycle of H. americanum in dogs and the sporogonic development in the invertebrate host have been described. ACH is diagnosed primarily by histologic examination of skeletal muscle. Curative therapy is not available, but anti-protozoal and anti-inflammatory drugs may prolong life. Naturally infected coyotes have been found in Oklahoma and Texas, and experimental infections have been produced in this canid. Additional effort is needed to determine the vertebrate host range of H. americanum and to define the enzootic cycle of which dogs have become a part; likewise, more work is required to determine whether larval GCTs can acquire infection and transmit it as nymphs.

A redescription of schizogony of Cytauxzoon felis in the domestic cat.

Cytauxzoon felis is a protozoan parasite that is transmitted by Dermacentor variabilis ticks and causes a uniformly fatal disease in domestic cats. In order to study schizogony and merozoite formation, D. variabilis nymphs were allowed to feed on domestic cats experimentally infected with C. felis, after which the molted adult ticks were fed on susceptible cats. Lung and liver tissues were collected from the cats during clinical cytauxzoonosis and were fixed for light and transmission electron microscopy. Some stages of parasite development were evident with light microscopy, but specific events associated with merogony could be documented only with electron microscopy. Schizogony was observed in endothelial macrophages of all tissues examined. The parasite appeared first as a multinucleated syncytium in which nuclear proliferation was evident. As the parasite syncytium developed, it became an increasingly elaborate labyrinth with extensive branches that were interconnected by thin processes of parasite cytoplasm. Organelles, including mitochondria and rhoptries, became apparent. Merozoite formation seemed to occur by rapid sequential fission along the margins of the multinucleated sporont in the cytoplasm of the host cell. As the sporont became smaller, merozoites were produced in a rosette-like configuration from the remaining parasite mass. Merozoites entered erythrocytes directly by endocytosis, without apparent injury to these cells. The sequence of events associated with merozoite formation in Cytauxzoon felis described herein differs from the previous description for this species and appears to be analogous to that described for the genus Theileria.

Occurrence of the Gulf Coast tick (Acari: Ixodidae) on wild and domestic mammals in north-central Oklahoma.

Parasitic life stages of Amblyomma maculatum Koch were collected from domestic cattle and several species of wild mammals during a 3.5-yr study (May 1998-October 2001) in north-central Oklahoma. Adult ticks were the predominant life stage collected from cattle, white-tailed deer, coyotes, and raccoons, whereas only immature ticks were collected from cotton rats and white-footed mice. The prevalence of adult A. maculatum on white-tailed deer (n = 15) examined in June, July, and August 1998 was 80, 100, 100%, respectively. The prevalence of adult A. maculatum on cattle (n = 84) ranged from 52% in February 1999 to 100% in May 1999. The prevalence of adult A. maculatum on coyotes (n = 16) was 100% in April 1998 and 43% on coyotes (n = 7) examined in January 2001. The prevalence of adult A. maculatum on raccoons (n = 23) examined during May, June, and July 1999 was 13%. No A. maculatum of any life stage were recovered from opossums (n = 7). Nine hundred forty-five rodents were trapped over 294 trap-nights; prevalence of A. maculatum larvae and nymphs on cotton rats (n = 395) was 34 and 15%, respectively, whereas on white-footed mice (n = 517), prevalence was 1.5 and 1.4%, respectively. No A. maculatum were recovered from pack rats (n = 33). There were significant differences (P = 0.0001) in larval infestation prevalence between cotton rats and white-footed mice in the spring, summer, and fall and for nymphs in the spring and summer. Results of A. maculatum parasitism and seasonal occurrence on hosts in this study are compared with previous research conducted in Oklahoma and with collection records of A. maculatum in the Entomology Museum at Oklahoma State University.

Isolation of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) from Ixodes scapularis and Dermacentor albipictus ticks (Acari: Ixodidae) in Oklahoma.

Borrelia burgdorferi was isolated from Ixodes scapularis Say and Dermacentor albipictus Packard that were removed as partially fed adults from white-tailed deer, Odocoileus virginianus Zimmermann, in Oklahoma. Isolation in media was accomplished only after homogenates of pooled field-collected ticks were inoculated into laboratory-reared Peromyscus leucopus and reisolated from the urinary bladder into BSK II media. Both isolates were confirmed by western blot analysis and reactivity with monoclonal antibody H5332. These are the first reported isolates of B. burgdorferi from Oklahoma from these two tick species and are the first isolates from ticks from the south-central United States that were infective for laboratory-reared P. leucopus.

Attempted transmission of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) (JDI strain) by Ixodes scapularis (Acari: Ixodidae), Dermacentor variabilis, and Amblyomma americanum.

Laboratory-reared Ixodes scapularis Say, Amblyomma americanum (L.), and Dermacentor variabilis (Say) were fed on New Zealand white rabbits experimentally infected with Borrelia burgdorferi (JDI strain). At repletion, spirochetes could be detected by dark-field microscopy only in I. scapularis. Acquisition rates were 18 and 21%. When previously exposed nymphs of each species were fed on susceptible rabbits, I. scapularis was the only tick of the three species that transmitted B. burgdorferi. When a single rabbit was experimentally infected with B. burgdorferi and infested at 7-d intervals with I. scapularis, A. americanum, D. variabilis, and a second time with I. scapularis, B. burgdorferi was detected again only in cultures from the two groups of I. scapularis. When molted nymphs from each tick species were allowed to feed on susceptible rabbits, spirochetes again were isolated only at necropsy from the rabbits on which the two groups of I. scapularis fed.

Experimental transmission of Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) among white-tailed deer by Amblyomma americanum (Acari: Ixodidae).

Ehrlichia chaffeensis Anderson, Dawson & Wilson, causative agent of human (predominantly monocytic) ehrlichiosis, was successfully transmitted experimentally by Amblyomma americanum (L.) to white-tailed deer, Odocoileus virginianus (Zimmerman). Deer were needle-exposed intravenously to E. chaffeensis in tissue-culture canine macrophage (DH82) cells, and 11 d later were exposed to laboratory-reared A. americanum larvae, nymphs, and adults for acquisition feeding. Three months after this feeding, naive deer and dogs were exposed to recently molted nymphs and adults. Attempted reisolation of the pathogen by way of tissue culture was successful from one needle-exposed deer but not from the tick-exposed deer or dogs. Based on serologic evidence and polymerase chain reaction data, both nymphal and adult ticks transmitted E. chaffeensis to naive deer but not to dogs.