Short report: Thai tick typhus, Rickettsia honei, and a unique rickettsia detected in Ixodes granulatus (Ixodidae: Acari) from Thailand.

A unique Rickettsia species (Rickettsia thailandii sp. nov.) was identified in an Ixodes granulatus by use of polymerase chain reaction heteroduplex mobility assay by use of segments of the citrate synthase gene. This tick was collected from Rattus rattus from Nakhon Ratchasima province in 1970. Another I. granulatus was infected with Thai tick typhus strain TT-118, Rickettsia honei sp. nov. Stenos, Roux, Walker & Raoult; this tick was removed from a R. rattus collected 4 years later from the same province. Ixodes granulatus is the first tick species in Australasia shown to be infected with R. honei and the unique Rickettsia species.

Prevention of sporogony of Plasmodium vivax in Anopheles dirus mosquitoes by transmission-blocking antimalarials.

The sporontocidal activity of four dihydroacridine-diones (WR-233602, WR-243251, WR-250547, and WR-250548) and three fluoroquinolones (WR-279135, WR-279298, and WR-279288) was determined against naturally circulating isolates of Plasmodium vivax. Laboratory-reared Anopheles dirus mosquitoes were infected with P. vivax by feeding them on gametocytemic volunteers reporting to local malaria clinics in Kanchanaburi and Tak provinces, Thailand. Four days after the infectious feed, mosquitoes were re-fed on uninfected mice treated 90 minutes previously with a given drug at a dose of 100 mg base drug/kg mouse body weight. Sporontocidal activity was determined by assessing both oocyst and sporozoite development. None of the fluoroquinolones exhibited sporontocidal activity against P. vivax, whereas all 4 dihydroacridine-diones affected sporogonic development to some degree. WR-233602 affected oocyst development, but had no impact on sporozoite production, WR-250548 affected oocyst development and had a limited effect on sporozoite production, and WR-243251 and WR-250547 had a marked impact on all phases of sporogony. These data demonstrate that experimental dihydroacridine-diones are capable of interrupting the sporogonic development of P. vivax. These compounds may be useful in preventing malaria transmission.

Spotted fever group Rickettsia in Dermacentor variabilis (Acari: Ixodidae) infesting raccoons (Carnivora: Procyonidae) and opossums (Marsupialia: Didelphimorphidae) in Tennessee.

Spotted fever group Rickettsia were present in 13 of 1,171 (1.1%) of adult Dermacentor variabilis Say removed from raccoons (Procyon lotor L.) and Virginia opossums (Didelphis virginiana Kerr) in western Tennessee. Spotted fever group Rickettsia were detected by amplification of a 617-bp segment of the citrate synthase gene by polymerase chain reaction.

Genetic heterogeneity of Borrelia burgdorferi sensu lato in the southern United States based on restriction fragment length polymorphism and sequence analysis.

Fifty-six strains of Borrelia burgdorferi sensu lato, isolated from ticks and vertebrate animals in Missouri, South Carolina, Georgia, Florida, and Texas, were identified and characterized by PCR-restriction fragment length polymorphism (RFLP) analysis of rrf (5S)-rrl (23S) intergenic spacer amplicons. A total of 241 to 258 bp of intergenic spacers between tandemly duplicated rrf (5S) and rrl (23S) was amplified by PCR. MseI and DraI restriction fragment polymorphisms were used to analyze these strains. PCR-RFLP analysis results indicated that the strains represented at least three genospecies and 10 different restriction patterns. Most of the strains isolated from the tick Ixodes dentatus in Missouri and Georgia belonged to the genospecies Borrelia andersonii. Excluding the I. dentatus strains, most southern strains, isolated from the ticks Ixodes scapularis and Ixodes affinis, the cotton rat (Sigmodon hispidus), and cotton mouse (Peromyscus gossypinus) in Georgia and Florida, belonged to Borrelia burgdorferi sensu stricto. Seven strains, isolated from Ixodes minor, the wood rat (Neotoma floridana), the cotton rat, and the cotton mouse in South Carolina and Florida, belonged to Borrelia bissettii. Two strains, MI-8 from Florida and TXW-1 from Texas, exhibited MseI and DraI restriction patterns different from those of previously reported genospecies. Eight Missouri tick strains (MOK-3a group) had MseI patterns similar to that of B. andersonii reference strain 21038 but had a DraI restriction site in the spacer. Strain SCGT-8a had DraI restriction patterns identical to that of strain 25015 (B. bissettii) but differed from strain 25015 in its MseI restriction pattern. Strain AI-1 had the same DraI pattern as other southern strains in the B. bissettii genospecies but had a distinct MseI profile. The taxonomic status of these atypical strains needs to be further evaluated. To clarify the taxonomic positions of these atypical Borrelia strains, the complete sequences of rrf-rrl intergenic spacers from 20 southeastern and Missouri strains were determined. The evolutionary and phylogenetic relationships of these strains were compared with those of the described genospecies in the B. burgdorferi sensu lato species complex. The 20 strains clustered into five separate lineages on the basis of sequence analysis. MI-8 and TXW-1 appeared to belong to two different undescribed genospecies, although TXW-1 was closely related to Borrelia garinii. The MOK-3a group separated into a distinct deep branch in the B. andersonii lineage. PCR-RFLP analysis results and the results of sequence analyses of the rrf-rrl intergenic spacer confirm that greater genetic heterogeneity exists among B. burgdorferi sensu lato strains isolated from the southern United States than among strains isolated from the northern United States. The B. andersonii genospecies and its MOK-3a subgroup are associated with the I. dentatus-cottontail rabbit enzootic cycle, but I. scapularis was also found to harbor a strain of this genospecies. Strains that appear to be B. bissettii in our study were isolated from I. minor and the cotton mouse, cotton rat, and wood rat. The B. burgdorferi sensu stricto strains from the south are genetically and phenotypically similar to the B31 reference strain.

Temporal changes in prevalence of scrub typhus rickettsia (Orientia tsutsugamushi) infecting the eggs of Leptotrombidium imphalum (Acari: Trombiculidae).

Eggs from seven colony lines of the chigger mite Leptotrombidium imphalum (Vercammen-Grandjean & Langston) were examined for infection with Orientia tsutsugamushi (Hyashi), the etiologic agent of scrub typhus. The polymerase chain reaction (PCR) using primers OtP 56.809 and OtM 56.1221, which amplify a 291 bp region of the P56 gene of O. tsutsugamushi, was used to detect scrub typhus within single eggs. All seven chigger mite lines produced infected eggs with varying rates of infection (Li1 = 8.1%, n = 124; Li2 = 45.6%, n = 90; Li3 = 30.1%, n = 144; Li4 = 31.7%, n = 145; Li5 = 21.3%, n = 136; Li6 = 41.6% n = 77; Li7 = 22.5%, n = 110). The 3 wk with the highest infection rates for each line using Fourier analysis were as follows: Li1 = 2, 7, 14; Li2 = 4, 6, 12; Li3 = 3, 6, 12; Li4 = 4, 6, 12; Li5 = 5, 7, 14; Li7 = 4, 6, 12. Li6 only had nine measurements over time; therefore, Li6 was excluded from individual analysis. Infection rates of scrub typhus in eggs occurred in a 2-wk 2-d cycle, using Fourier analysis of combined data. Not only did infection rates vary among the progeny of females, but temporal variation also occurred.

Host association and seasonal activity of Amblyomma americanum (Acari: Ixodidae) in Missouri.

From June 1993 through June 1996, 2,260 adult, 4,426 nymphal, and 2,178 larval lone star ticks Amblyomma americanum (L.) were collected in Missouri from vertebrate hosts and by dragging a cloth over vegetation. Prevalence, mean intensity, and relative abundance of each stage varied among hosts. The relative abundance of adult lone star ticks was highest on white-tailed deer, but this stage was also collected from raccoons, opossum, red fox, coyotes, and wild turkey. Nymphs were collected from gray squirrels, eastern cottontail rabbits, opossums, red fox, Carolina wren, and bobwhite quail, but the highest relative abundance occurred on wild turkey, white-tailed deer, and raccoons. Eastern cottontail rabbits, white-tailed deer, raccoons, and squirrels had the highest relative abundance of larval lone star ticks, but they were also found on opossums and wild turkey. The activity of adult lone star ticks was greatest from May through July. The activity for nymphs was highest from May through August, and for larvae, July through September.

New host and distribution record of Amblyomma javanense (Acari: Ixodidae) in Thailand.

Amblyomma javanense (Supino) was collected from a Malayan pangolin (Manis javanica Desmarest) and a wild boar (Sus scrofa L.) from Tak province on the western boundary of Thailand along the Myanmar (Burma) border. To date, this tick species has not been recorded from this area and from a wild boar.

Host utilization and seasonal occurrence of Dermacentor species (Acari:Ixodidae) in Missouri, USA.

A total of 3,235 Dermacentor variabilis (Say) specimens were collected from birds, mammals, and by dragging vegetation, and 2,683 D. albipictus (Packard) ticks were collected from deer from 1993 to 1996. Peak seasonal occurrence of adult D. variabilis was from May through July with a precipitous decrease in August. Nymphal D. variabilis populations peaked in June. Peak activity of larvae was bimodal, with one activity peak during late summer (September) and a second peak in winter or early spring. The raccoon, Procyon lotor (L.), was the principal host of adults followed by the Virginia opossum, Didelphis virginiana Kerr. Rodents and the eastern cottontail rabbit, Sylvilagus floridanus (J. A. Allen), were the primary hosts of nymphs. The marsh rice rat, Oryzomys palustris (Harlan), was the principal host of larvae followed by the pine vole, Microtus pinetorum (Le Conte), and white-footed mouse, Peromyscus leucopus (Rafinesque). All stages of D. albipictus were found only on white-tailed deer, Odocoileus virginianus (Zimmermann). Numbers of adult and nymphal D. albipictus peaked in November, whereas larvae peaked in September.

Seasonal activity and host associations of Ixodes scapularis (Acari: Ixodidae) in southeastern Missouri.

Based on tick collections recovered from wild vertebrates and by dragging, the seasonal occurrence of adult blacklegged ticks, Ixodes scapularis Say, extended from October through May in southeastern Missouri. Adult activity was bimodal with the higher peak occurring in November followed by a lower peak in February. The activity of immature I. scapularis had the general pattern of that found in the Northeast where Lyme disease is hyperendemic, with larval activity (July) peaking after that of nymphs (May and June). Vertebrates varied in their importance as hosts of I. scapularis. White-tailed deer, Odocoileus virginanus (Zimmerman), and coyotes, Canis latrans Say, were the primary hosts of adult I. scapularis. Broad-headed skinks, Eumeces laticeps (Schneider), and eastern fence lizards, Sceloporus undulatus (Latreille), were the primary hosts of nymphal I. scapularis. The broad-headed skink, 5-lined skink, Eumeces fasciatus (L.), and Carolina wren, Thryothorus ludovicianus (Latham), were the primary hosts of larval I. scapularis. Homeotherms were important hosts of immature I. scapularis, accounting for 30% of nymphs and 39% of larvae collected. The eastern cottontail rabbit, Sylvilagus floridanus (Allen), may play an important role in the epidemiology of Lyme disease in Missouri. Isolates of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner were made from ticks recovered from rabbits, making the cottontail rabbit a key species for further study of the epidemiology of Lyme borreliosis in Missouri.

Patterns of infestation by adult Dermacentor variabilis (Acari: Ixodidae) in a mark-recapture study of raccoons (Mammalia: Carnivora) and Virginia opossums (Mammalia: Didelphimorphia) in Tennessee.

A mark-recapture study of raccoons (Procyon lotor L.) and Virginia opossums (Didelphis virginiana Kerr) was conducted from February 1991 through April 1994 to determine host interactions with adult Dermacentor variabilis Say. We captured 1,293 raccoons and Virginia opossums during the 3-yr study (140 individual raccoons and 160 individual Virginia opossums) with 1,895 adult D. variabilis collected. Raccoons had a significantly higher mean intensity and higher prevalence of adult ticks than Virginia opossums (Mann-Whitney Z = 6.15, chi 2 = 51.9, P < 0.001). Mean intensity follows Margolis et al. (1982) as being the mean number of parasite species per infected host. Prevalence follows Margolis et al. (1982) as being the number of individuals of the host species infected with a parasite species divided by the number of hosts examined. The time required for a higher prevalence and mean intensity of ticks to occur on raccoons than Virginia opossums was < 7 d. No significant differences occurred between the mean intensity or prevalence of D. variabilis between sexes or among age classes of raccoons. Significant differences in prevalence and mean intensity of ticks occurred between sexes and among age classes of Virginia opposums. Infestation increased by 0.64 ticks per day on Virginia opossums and 1.77/d on raccoons during the first 7 d. The base host finding rate (ticks per host per day) of adult D. variabilis on Virginia opossums was 0.064 and 0.053 on raccoons. Tick interactions with hosts are quantified and may reflect behavioral differences between sexes and among age groups intraspecifically, and host preferences of adult D. variabilis interspecifically.

First isolation and cultivation of Borrelia burgdorferi sensu lato from Missouri.

Five Borrelia burgdorferi sensu lato isolates from Missouri are described. This represents the first report and characterization of such isolates from that state. The isolates were obtained from either Ixodes dentatus or Amblyomma americanum ticks that had been feeding on cottontail rabbits (Sylvilagus floridanus) from a farm in Bollinger County, Mo., where a human case of Lyme disease had been reported. All isolates were screened immunologically by indirect immunofluorescence by using monoclonal antibodies to B. burgdorferi-specific outer surface protein A (OspA) (antibodies H3TS and H5332), B. burgdorferi-specific OspB (antibody H6831), Borrelia (genus)-specific antiflagellin (antibody H9724), and Borrelia hermsii-specific antibody (antibody H9826). Analysis of the isolates also involved a comparison of their protein profiles by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Finally, the isolates were analyzed by PCR with six pairs of primers known to amplify selected DNA target sequences specifically found in the reference strain B. burgdorferi B-31. Although some genetic variability was detected among the five isolates as well as between them and the B-31 strain, enough similarities were found to classify them as B. burgdorferi sensu lato.

The fleas (Siphonaptera) of Tennessee.

Thirty-three species of fleas are recorded from the state of Tennessee. New state records are reported for two species, the pulicid fleas Euhoplopsyllus glacialis affinis and Pulex simulans. Two species of fleas with catholic feeding habits appear to be especially widespread and abundant in Tennessee. These are the pulicid Ctenocephalides felis which parasitizes cats, dogs, humans, opossums, and other medium to large sized mammals, and the hystrichopsyllid Ctenophthalmus pseudagyrtes which is associated with several species of small mammals, particularly shrews, moles, voles, and native mice. For a southeastern state, Tennessee has a relatively rich flea fauna. The figure of 33 flea species recorded here for Tennessee is higher than documented figures for other southeastern states (17 species for Alabama, 19 for Florida, 20 for Georgia, 12 for Mississippi, 18 for North Carolina, 19 for South Carolina). This is largely because several species with boreal origins inhabit the higher elevations characteristic of the Appalachian Mountains in the eastern part of the state. Although plague is not enzootic as far east as Tennessee, and murine typhus is rare of absent, suitable flea vectors inhabit the state and one abundant flea species, C. felis, is a pest because it feeds on companion animals and humans.

Sucking lice (Anoplura) of mammals of Tennessee.

Twenty-five species of sucking lice are recorded from wild and domestic mammals, including humans, from Tennessee. Collections of 10 of these species (Haematopinus eurysternus, Hoplopleura captiosa, Hoplopleura hirsuta, Hoplopleura oryzomydis, Hoplopleura trispinosa, Linognathus africanus, Linognathus setosus, Linognathus vituli, Neohaematopinus sciuropteri and Polyplax auricularis) represent newly documented state records. Host specificity was exhibited by 22 species of lice with each of these species being recovered from just one mammal species. Louse infestation prevalences are included for large samples of hosts. A host-parasite list for Tennessean sucking lice is included.

Some factors affecting infestation of white-tailed deer by blacklegged ticks and winter ticks (Acari:Ixodidae) in southeastern Missouri.

A total of 5,669 ticks of 4 species was collected from 515 hunter killed, white-tailed deer. Odocoileus virginianus (Zimmerman), in southeastern Missouri from 1993 through 1995. The American dog tick, Dermacentor variabilis (Say) (4 adults), the lone star tick, Amblyomma americanum (L.) (57 adults, 2 nymphs), the blacklegged tick, Ixodes scapularis (Say) (3,120 adults), and the winter tick, Dermacentor albipictus (Packard) (2.059 adults, 436 nymphs, 1 larva) were collected. Patterns of adult D. albipictus and I. scapularies infesting deer were analyzed with respect to upland versus lowland habitat, county, and host sex. Prevalence and intensity of infestation by D. albipictus were higher on bucks than does, and a higher infestation prevalence was recorded for this tick on deer from upland than from lowland habitats. Mean intensities for D. albipictus were not significantly different between counties. Prevalence and mean intensity of infestation for I. scapularis were significantly higher on deer from uplands than lowlands and on bucks than does; mean intensities also differed between counties for this tick. Because adjacent populations, as well as the sex of the host, can differ in infestation rates, differences between local populations of I. scapularis should be recognized to optimize tick surveys and population models.

Gastrointestinal helminths in the river otter (Lutra canadensis) in Tennessee.

The first records of 3 helminth parasites from otters, Lutra canadensis, collected in Tennessee are reported. Digestive tracts of 91 river otters collected from 1983 to 1993 were examined for helminth parasites. Thirty otters were infected with Baschkirovitrema incrassatum, 5 otters were infected with Acanthocephalus sp., and 1 otter was infected with 2 Strongyloides lutrae. No significant differences in prevalence, mean abundance, or mean intensity of B. incrassatum occurred between counties or months. No significant differences in the prevalence or mean intensity of B. incrassatum occurred between years, but significant yearly differences in mean abundance were recorded from 1988 through 1993 (P < 0.05). There were no statistical differences in B. incrassatum parasitization between males and females or juvenile and adult otters.

Fleas and lice parasitizing mammals in Missouri.

Three species of chewing lice, 11 species of sucking lice, and 28 species of fleas are recorded from mammals in Missouri. Of these, seven species of sucking lice (Hoplopleura acanthopus, Hoplopleura hesperomydis, Hoplopleura sciuricola, Neohaematopinus sciuri, Neohaematopinus sciurinus, Neohaematopinus sciuropteri, and Solenopotes ferrisi) and one species of flea (Doratopsylla blarinae) represent new state records. From 1993 to 1995, 773 individual mammals were examined for ectoparasites in southeastern Missouri. One species of chewing louse, 6 species of sucking lice, and 11 species of fleas were recovered from 18 of the 21 mammal species examined. Ctenophthalmus pseudagyrtes was recovered from more mammal species (6) than any other flea species; and the white-footed mouse, Peromyscus leucopus, was parasitized by more flea species (5) than other hosts examined. Except for H. sciuricola, which was recovered from two congeneric species of tree squirrels, each species of louse was confined to a separate host species.

Interspecific differences between small mammals as hosts of immature Dermacentor variabilis (Acari: Ixodidae) and a model for detection of high risk areas of Rocky Mountain spotted fever.

Fourteen species of small mammals were captured from July 1990 through August 1991 in Tennessee, from which 1,217 immature Dermacentor variabilis and 1 Ixodes dentatus were collected. Mammal species were given scores of importance (TS) as hosts to immature D. variabilis based on mean intensity and prevalence. The rice rat ranked the highest, with a TS = 5, followed by the golden mouse TS = 4, white-footed mouse TS = 3, pine vole TS = 2, cotton rat TS = 1, with the Norway rat, house mouse, and short-tailed shrew all having a TS = 0. Assigning a TS allows a quantitative method for differentiating and ranking small mammals as hosts for immature D. variabilis. Relative abundance of a species can also be important in determining D. variabilis populations, even with a low TS. The potential of Rocky Mountain spotted fever (RMSFP) to occur in an area was estimated using the total score of small mammal hosts in an area and multiplying the relative abundance of important host species. The RMSFP of a site, based only upon small mammal species composition and relative abundance of important host species, was an accurate estimate of adult D. variabilis infesting raccoons and opossums at that trap site (P < or = 0.001). A RMSFP of 1.61 is needed to produce an estimated 252 adults per ha (RMSF threshold) at 98% survival of engorged immature ticks (P < 0.001).

The occurrence of antibodies to Naegleria species in wild mammals.

Individuals from 13 wild mammalian species collected in southwestern Tennessee were serologically positive for anti-Naegleria spp. antibodies (ANA). This is the first report of ANA in wild mammals. Interspecific differences in the occurrence of ANA and titers indicate that wild mammals have differing degrees of contact with Naegleria spp. based on ecological or behavioral adaptations, and possibly the innate ability of a species to produce ANA. Intraspecifically, it appears that if a mammal is exposed to Naegleria spp. in the environment, titers of ANA will not significantly differ, regardless of age or sex. Adults of many species had significantly higher occurrences of ANA. Populations of juvenile wild mammals are probably at higher risk than adults to naeglerial infection in the environment, not because of lower titers, but because their chance of having ANA is less than adults. Differences in the occurrence of ANA in wild mammals may also reflect how humans are exposed to Naegleria spp. in the environment.

Ticks (Acari: Ixodidae) infesting medium-sized wild mammals in southwestern Tennessee.

Seven species of ixodid ticks (n = 2,661) were found on medium-sized wild mammals (n = 295) during a 13-mo study in Shelby County, Tennessee. The seven tick species collected were Dermacentor variabilis (Say), Amblyomma americanum (L.), Rhipicephalus sanguineus (Latreille), Ixodes texanus (Banks), I. cookei (Packard), I. scapularis (Say), and Haemaphysalis leporispalustris (Packard). The raccoon had the greatest tick species diversity in all of the aforementioned ticks except H. leporispalustris and R. sanguineus. The raccoon and opossum accounted for 96.9% of the ticks collected and were the most commonly captured medium-sized mammals. The only tick collected in high enough numbers for statistical analysis was D. variabilis. Mammal species and habitat type were the most important factors affecting the mean number of adult D. variabilis per mammal. The mean number of D. variabilis adults carried by raccoons was significantly higher than opossums. Whether a habitat occurred within Memphis city limits or outside city limits also affected the number of adult D. variabilis on mammals. The interaction between habitat, mammal, and whether inside or outside the city limits was near statistical significance. It is suggested that there is biological significance; within city limits, medium-sized wild mammals are forced into wooded areas where there is a subsequent increase in tick populations in these habitat patches.

New host of Ixodes dentatus (Acari: Ixodidae), and first record in Tennessee.

Two specimens of Ixodes dentatus Marx were found in southwestern Tennessee in Shelby County during a 14-mo tick survey. This was the first record for this tick in Tennessee. An adult female was found on a dry ice trap and one larva was found on a live-trapped Peromyscus leucopus, the first time this tick has been reported from P. leucopus. This may be another combination of vector and host in the ecology and transmission of B. burgdorferi in the wild.