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Biomedical subjects

A A Kocan

Publications and source records attributed to A A Kocan.

At least 19 recordsLinked to original sources
PubMed1999

Naturally occurring hepatozoonosis in coyotes from Oklahoma.

Nine of 16 free-ranging coyotes (Canis latrans) from central Oklahoma (USA) had naturally acquired infections of Hepatozoon americanum. Infections were confirmed by recognition of tissue stages closely resembling H. americanum in skeletal and cardiac muscle. At the time coyotes were collected they were infested with a variety of ticks, including adult Gulf Coast ticks (Amblyomma maculatum). We propose that the high prevalence of H. americanum in this small sample of free-ranging coyotes and the ability of these same animals to harbor adult populations of A. maculatum is an important component of the epizootiology of canine hepatozoonosis in North America.

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PubMed1998

A molecular and serologic survey of Ehrlichia canis, E. chaffeensis, and E. ewingii in dogs and ticks from Oklahoma.

Polymerase chain reaction and Southern hybridization were used to survey for the presence of Ehrlichia canis, Ehrlichia chaffeensis, and Ehrlichia ewingii in blood samples of 65 dogs that harbored ticks from northcentral and northeastern Oklahoma. Dog blood samples were also examined for antibodies against E. canis and E. chaffeensis, using an immunofluorescent antibody test. Ten of 65 dogs (15.4%) examined were positive for Ehrlichia spp. by PCR. Four (6.2%) were positive for E. ewingii, 2 (3.1%) for E. canis, and 4 (6.2%) for E. chaffeensis. Seven dogs (10.8%) were seropositive for E. canis or E. chaffeensis. Ticks collected from PCR-positive dogs were examined by PCR for the presence of Ehrlichia DNA. Several groups of ticks were PCR-positive for E. ewingii or E. canis. E. canis was detected in Rhipicephalus sanguineus, which is considered the major vector for that organism. E. ewingii was detected in a larger variety of ticks, including the only known vector Amblyomma americanum, as well as in Dermacentor variabilis and R. sanguineus. Results suggest that Ehrlichia spp. which are canine and human pathogens circulate in dogs in Oklahoma and in several tick species that feed on dogs.

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PubMed1998

Observations on tissue stages of Hepatozoon americanum in 19 naturally infected dogs.

Lesions and associated tissue stages of Hepatozoon americanum in 19 naturally infected dogs are described. Schizogony takes place in an unidentified host cell which, during the early stages of the asexual cycle, is contained within a broad, multilamellar mucopolysaccharide 'cyst.' Material forming the cyst appears to be host-derived. An intense inflammatory response follows rupture of the schizont and disintegration of the cyst wall. There is unusually intense angiogenesis associated with the resulting granulomatous inflammation initiated by the freed merozoites. Phagocytized zoites enter the canine circulatory system through the walls of these vessels. Evidence is presented that suggests a single infecting episode can cause prolonged (> or = 9 months) infection, and further, that infection is perpetuated by repeated asexual cycles. Parasites in peripheral blood leukocytes include both those with and without a visible nucleus.

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PubMed1996

Ehrlichia-like 16S rDNA sequence from wild white-tailed deer (Odocoileus virginianus).

The reservoir hosts of Ehrlichia chaffeensis, etiologic agent of human ehrlichiosis are unknown. Initially, white-tailed deer (WTD) were serologically implicated as possible reservoirs of E. chaffeensis. Subsequent studies showed that WTD were susceptible to infection with E. chaffeensis and that deer-to-deer transmission by a tick vector, Amblyomma americanum, is possible under experimental conditions. To determine if wild WTD were infected with E. chaffeensis, whole blood was collected from 10 deer from Oklahoma and Georgia. All 10 deer had antibodies reactive to E. chaffeensis. Whereas E. chaffeensis was not isolated, restriction enzyme mapping and sequencing of the 16S rDNA gene revealed that a unique Ehrlichia-like agent was present. All 10 deer appeared to be infected with the same agent. We suspect that A. americanum is the vector of this new agent based upon the previously published temporal association between the appearance of E. chaffeensis seropositive WTD and A. americanum. However, the taxonomic and antigenic relationships, geographic distribution, epidemiology, and zoonotic potential of this agent are yet to be determined.

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PubMed1995

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.

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PubMed1993

Experimental Borrelia burgdorferi infections in the white-footed mouse, deer mouse, and fulvous harvest mouse detected by needle aspiration of spirochetes.

Three methods were tested for recovering Borrelia burgdorferi from live mice onto BSK II culture medium. Four laboratory-reared Peromyscus leucopus were inoculated intraperitoneally with the JD-1 isolate of Borrelia burgdorferi. Borrelia burgdorferi spirochetes were recovered from 13 of 20 (65%) samples taken by needle aspiration between days 7 and 40 post-inoculation (PI) and from 1 of 16 samples of skin obtained by ear punch biopsy during the same sampling period. Spirochetes were not recovered from culture media inoculated with mouse blood. The use of needle aspirates for recovering spirochetes was compared among three species of mice: P. leucopus, P. maniculatus, and Reithrodontomys fulvescens. Spirochetes were isolated from 14 of 15 aspiration samples from four P. maniculatus, 12 of 20 from three P. leucopus, and 15 of 20 from four R. fulvescens taken between days 7 and 48 PI. Spirochetes were isolated from only one aspiration sample between days 80 and 95 PI from any of the mice tested. Needle aspiration was an efficient method for repeated recovery of B. burgdorferi from live, experimentally infected mice. We also document R. fulvescens as an experimental host for B. burgdorferi. Based on their susceptibility to infection, all species of mice tested herein may play a role in the epidemiology of Lyme disease where their distribution is compatible with endemic transmission.

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PubMed1993

Detection of Borrelia burgdorferi in tissues of experimentally infected Peromyscus leucopus by the polymerase chain reaction.

A polymerase chain reaction (PCR) assay was used to amplify a 158 base pair (bp) DNA fragment from the ospA locus of Borrelia burgdorferi. This assay could identify all of four distinct B. burgdorferi isolates from Oklahoma and could detect as little as 50 x 10(-15) g of purified DNA from B. burgdorferi (JD-1) after agarose gel electrophoresis and ethidium bromide staining. The assay was used to detect the Lyme spirochete in the heart, liver, spleen, kidney and urinary bladder of four experimentally infected Peromyscus leucopus and results were compared with detection by in vitro cultivation in BSK-II media. Fifteen of twenty organs examined showed 158 bp amplification products. Except for one kidney sample all organs that were culture-positive were also positive by PCR. Two culture-negative heart samples and one culture-negative liver sample were PCR positive. The results indicate that this PCR assay may be useful for detection of B. burgdorferi from field-caught wildlife hosts in epidemiological investigations.

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PubMed1992

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.

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PubMed1992

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.

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PubMed1992

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.

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PubMed1992

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.

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PubMed1992

Isolation of Borrelia burgdorferi from Peromyscus leucopus in Oklahoma.

Borrelia burgdorferi was isolated from a field-caught Peromyscus leucopus from central Oklahoma (USA). The strain was identified as B. burgdorferi by reaction with monoclonal antibody H5332 specific for the outer surface protein OspA of B. burgdorferi. This represents the first isolation of B. burgdorferi from a wild mouse outside of the normal range of the known vectors Ixodes dammini and I. pacificus.

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PubMed1991

Activity of buparvaquone against Theileria cervi in white-tailed deer.

Buparvaquone, a naphthoquinone with known efficacy against Theileria parva parva in cattle, was tested for activity against Theileria cervi piroplasms in both an in vitro culture system and in vivo in experimentally infected white-tailed deer. The in vitro data showed a significant decrease in the incorporation of 3H-hypoxanthine by infected red blood cells treated with buparvaquone when compared to that seen with imidocarb and chloroquine treatment. In both intact and splenectomized deer treated with buparvaquone (2.5 mg kg-1) a gradual decrease in piroplasm parasitaemia was observed following treatment. However, in the splenectomized deer, parasitaemia levels returned to near pretreatment values after approximately 2 weeks.

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PubMed1991

Gastropod availability and habitat utilization by wapiti and white-tailed deer sympatric on range enzootic for meningeal worm.

Gastropod occurrence and the utilization of habitat by sympatric populations of wapiti (Cervus elephus) and white-tailed deer (Odocoileus virginianus) on range enzootic for meningeal worm (Parelaphostrongylus tenuis) were studied on Cookson Hills Wildlife Management Area (WMA) in eastern Oklahoma. Visual observations and fecal pellet group transect data indicated that wapiti spent the majority of their time in open fields and meadows where we recovered the least numbers of gastropods. Although deer were frequently observed in open areas, visual sightings and transect data indicated that they spent more time in forested areas where we recovered the most gastropods. Gastropods harbored low numbers of P. tenuis larvae (0.00 to 0.06 larvae/gastropod) in all habitat types with the greatest recovery from red oak white oak-hickory forests (0.34 larvae/gastropod). Our results indicate that the reason a viable wapiti herd exists on Cookson Hills WMA in a P. tenuis enzootic area is at least partially because of the habitat preference by wapiti and the reduced availability of infected gastropods in the selected areas prefered by the wapiti. We were not able to detect any free-ranging wapiti that were shedding P. tenuis larvae nor were we able to detect past or sub-clinical infections with P. tenuis in wapiti.

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PubMed1989

Serological prevalence and isolation of Babesia odocoilei among white-tailed deer (Odocoileus virginianus) in Texas and Oklahoma.

Serum samples collected from 581 white-tailed deer (Odocoileus virginianus) from Texas and from 124 white-tailed deer from Oklahoma were tested by the indirect fluorescent antibody technique against Babesia odocoilei. Prevalence of seropositive reactors varied from site to site in both states. Prevalence rates were statistically ranked as high, intermediate or low. Deer less than 12-mo-old had a significantly lower prevalence than all other age classes.

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PubMed1988

Tick paralysis.

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Animals↗
PubMed1988

Susceptibility of Amblyomma americanum to natural and experimental infections with Theileria cervi.

One hundred fifty Amblyomma americanum were examined between March and September 1986 from Cookson Hills Wildlife Refuge in eastern Oklahoma (USA). Of these ticks, 11% (17 of 150) were infected with Theileria cervi. Field-collected nymphal ticks had an 8% (3 of 37) prevalence of infection averaging 1.0 infected acini/nymph. Female ticks had a 16% prevalence of infection averaging 1.6 infected acini/female; T. cervi was not observed in salivary glands of field-collected male ticks. When laboratory reared A. americanum nymphs were allowed to feed on experimental white-tailed deer (Odocoileus virginianus) with varying T. cervi parasitemias (less than 1, 2, 6 and greater than 20%), only ticks which fed on deer with parasitemias greater than 1% became infected. Although prevalence and intensity of infection varied in the infected ticks, there was no significant difference in prevalence of infection between males and females. However, females did acquire significantly greater intensities than males. The data from these studies confirm that T. cervi overwinters in A. americanum and suggests that the prevalence, intensity and abundance of infection of T. cervi in ticks is influenced by the parasitemia of the deer host. Furthermore, fawns may play a more important role in the epidemiology of T. cervi transmission than do adult deer because of the coordination between tick activity patterns and deer fawning.

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