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The chalcid wasp Ixodiphagus hookeri (Howard) is a parasitoid of several ixodid ticks including the blacklegged tick, Ixodes scapularis Say. We evaluated effects of the feeding process of nymphal I. scapularis on the embryonic development of I. hookeri. Potentially wasp-parasitized nymphal I. scapularis were collected on Prudence Island, RI. Subsamples of the questing nymph cohort were allowed to feed on laboratory white mice. Both the body length and the scutal length of ticks were measured individually for questing nymphs and for feeding nymphs that were removed from hosts at time intervals of 12, 24, 36, 48, and 72 h after attachment. The diameters of wasp eggs they contained were also measured for each designated time interval. There was a positive relationship between the mean scutal index (ratio between body length and scutal length) of ticks and the mean diameter of wasp eggs during 72 h of tick feeding (P < 0.05). Moreover, it appeared that within 24 h of tick attachment, the scutal index of ticks remained unchanged. However, after that period, the scutal index increased significantly (P < 0.05). Diameters of wasp eggs increased continuously during tick feeding and at 72 h after attachment, enclosed eggs and completely formed larvae were found in several ticks. We conclude that factors related to the feeding process of nymphal I. scapularis are necessary to initiate the embryonic development of wasps.

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The reservoir competence of the meadow vole, Microtus pennsylvanicus Ord, for the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner was established on Patience Island, RI. Meadow voles were collected from 5 locations throughout Rhode Island. At 4 of the field sites, M. pennsylvanicus represented only 4.0% (n = 141) of the animals captured. However, on Patience Island, M. pennsylvanicus was the sole small mammal collected (n = 48). Of the larval Ixodes scapularis Say obtained from the meadow voles on Patience Island, 62% (n = 78) was infected with B. burgdorferi. Meadow voles from all 5 locations were successfully infected with B. burgdorferi in the laboratory and were capable of passing the infection to xenodiagnostic I. scapularis larvae for 9 wk. We concluded that M. pennsylvanicus was physiologically capable of maintaining B. burgdorferi infection. However, in locations where Peromyscus leucopus (Rafinesque) is abundant, the role of M. pennsylvanicus as a primary reservoir for B. burgdorferi was reduced.

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Effects of Babesia microti Franca on the pattern of feeding time, the body weight of engorged ticks, and the molting rate of the blacklegged tick, Ixodes scapularis Say, were determined. Using the Syrian golden hamster, Mesocricetus auratus (Waterhouse), as an animal model, we found no significant differences in patterns of feeding time determined for both larvae and nymphs that fed on B. microti-infected and uninfected hamsters. However, an infection of B. microti in hamsters delayed engorgement of the ticks. The presence of B. microti had no adverse effects on the body weight of engorged ticks. The mean body weight of groups of 5 engorged larvae fed on infected hamsters was not significantly different from that on uninfected hamsters. The mean body weight of individual nymphs that fed on infected hosts was significantly higher than that on uninfected hosts. Larvae fed on infected hamsters molted in greater numbers than those fed on uninfected hamsters. However, there was no significant difference in molting rates of nymphs derived from infected and uninfected hamsters. In addition, greater body weights and higher molting rates were observed in both larvae and nymphs that fed on uninfected white-footed mice, Peromyscus leucopus Rafinesque, compared with those on uninfected hamsters. Nymphs fed on mice spent a significantly longer time achieving repletion than those on uninfected hamsters. We suggest a mutualistic relationship in the interactions between B. microti and I. scapularis. This mutualism may potentially enhance the long-term coexistence and survival of both species. Furthermore, we suggest that the pattern of feeding time, the body weight of engorged ticks, and the molting rate of immature I. scapularis are host-dependent.

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Larval blacklegged ticks, Ixodes scapularis, were collected from white-footed mice. Peromyscus leucopus, on Prudence Island (where Microtus pennsylvanicus were not captured) and from meadow voles. M. pennsylvanicus, on Patience Island (where P. leucopus was absent) in Narragansett Bay, Rhode Island from June to October 1992. Ixodes scapularis larvae were also collected by flagging in the vicinity of host captures. On both islands, the relative density of larvae changed from July to September in samples from hosts, but not in flagging samples. Consequently, different sampling techniques can give different assessments of tick populations. Larvae were highly aggregated on both of the host species throughout the sampling period. As the mean relative density of larvae increased in the environment (based on flagging samples), larvae on the hosts became more dense and more crowded. Increased densities of larvae in the environment were not correlated with increased patchiness in the distribution of larvae among host animals on either island. Changes in the spatial distribution of larval I. scapularis on each host species had similar trends as larval densities and distributions within the environment. These results suggest that M. pennsylvanicus can serve as an alternative host for immature I. scapularis in a P. leucopus-free environment and have similar distributional characteristics.

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We described the parasitemia, hematologic changes, and immunity developed by golden hamsters during 8 wk of infection with Babesia microti following experimental inoculation. All 8 hamsters used in this study were readily infected. Animals attained peak parasitemias asynchronously but within a 2-wk period. Most of the animals reached their peak parasitemia by 4 wk postinoculation, attaining a mean +/- SD of 21.9 +/- 9.4% infected erythrocytes (range = 20-35%). Red blood cell count, packed cell volume, and hemoglobin level were used to monitor the course of the hemolytic anemia experienced by infected hamsters. All 3 measures corresponded inversely to the parasitemia; significant hematologic changes (P = 0.0001) were observed during the 8 wk of monitoring. Although all hamsters suffered from severe hemolytic anemia, they also recovered within the same period. Golden hamsters developed a detectable anti-B. microti IgG response by 2 wk postinoculation. Individual animals typically attained peak antibody levels (> or = 1:8, 192) 1 wk after the peak parasitemia. Hamsters retained a high IgG titer (> or = 1:4,096), although parasitemias fell dramatically, fluctuating thereafter at low levels (< 5%).

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The wasp Hunterellus hookeri Howard parasitizes several species of ixodid ticks including Ixodes dammini Spielman, Clifford, Piesman & Corwin, the vector of Lyme disease spirochetes, Borrelia burgdorferi, in the northeastern United States. We detected the occurrence and evaluated the distribution of this wasp parasitoid in populations of I. dammini in Rhode Island. There has been no intentional introduction of a tick parasitoid recorded anywhere in Rhode Island; yet, we found this wasp at one of the six study sites (Prudence Island), where it parasitized 21 (n = 243) and 17% (n = 284) of nymphal I. dammini collected during 1988 and 1989, respectively. The proportion of nymphs parasitized was greatest during May (46%) and was less in June (18%), July (18%), and August (11%). In Rhode Island, the wasp was only found parasitizing ticks at the site with the highest (by a factor of 2) tick population, confirming similar observations in Massachusetts and New York. It is suggested that establishment as well as the distribution of H. hookeri depends upon a super abundant deer tick population. The usefulness of this parasitoid as a biological control agent is yet unknown.

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The distribution of nymphal Ixodes dammini Spielman, Clifford, Piesman & Corwin in residential lawns was assessed by flagging on Prudence Island, RI. The number of ticks per sample was five times greater in lawns adjacent to woods than in lawns adjacent to other lawns. Relative tick abundance was negatively correlated with distance from the woods, but the decline was gradual. Spirochete prevalence in ticks did not differ among lawn types or at different distances from the woods. Therefore, barriers that keep people away from the wood edge probably lower the risk of acquiring Lyme disease, but there is still a risk. Even with physical barriers at lawn-wood edges, personal precautions to prevent tick bites should be followed.

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Involvement of adult Ixodes persulcatus ticks in the transmission of Lyme disease in Hailin County, Heilongjiang Province, China, is reported. In 1986 from April through August adult I. persulcatus was the dominant tick in this endemic area with an infection rate of 43% for the Lyme disease spirochaete, Borrelia burgdorferi. The incidence of Lyme disease cases presenting the symptom of erythema chronicum migrans (ECM) within this area was correlated with the seasonal abundance of adult I. persulcatus and the number of people bitten by ticks. The frequency of ECM formation in all age groups varied and was associated with the frequency of tick bites. In addition, a strain of B. burgdorferi was isolated from a pool of six female I. persulcatus collected from this area. We demonstrate that the seasonal abundance of adult I. persulcatus and its frequent attachment to humans result in the spring and summer transmission of Lyme disease in this endemic area. The role of immature I. persulcatus in Lyme disease transmission is apparently minimal.

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The cestode, Metroliasthes lucida, is reported for the first time from the eastern wild turkey (Meleagris gallopavo) in Rhode Island, United States; this is the first published record from New England. One of eight birds examined was infected with 10 cestodes.

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An enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent-antibody test were used to detect antibodies to Borrelia burgdorferi, the causative agent of Lyme disease, in Peromyscus leucopus (white-footed mouse). Of the 661 mice captured in Connecticut, Rhode Island, and New York during 1980 and 1983 to 1987, 166 (25.1%) had antibodies to B. burgdorferi by ELISA. Comparative analyses of 210 serum specimens, collected in areas where Lyme disease is endemic, revealed a threefold difference in sensitivity between the ELISA (38.1% positive) and the indirect fluorescent-antibody method (12.4%). Although prevalence of seropositive P. leucopus was highest during June, elevated amounts of antibody (1:1,280 to 1:2,560) were detected in mice that harbored spirochetes during all seasons. Being reservoirs for B. burgdorferi, these rodents are suitable for monitoring spirochete infections at foci and should be included in field evaluations of control programs aimed at suppressing Lyme disease.

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The scorpion fauna of Jordan consists of fourteen species belonging to three families (Buthidae, Scorpionidae and Diplocentridae), of which three species are poisonous: Leiurus quinquestriatus, Adroctonus crassicauda and Buthus occitanus. A key to all species is included. Five hundred and forty-seven cases of scorpion stings were reported during 1982-1985, including two fatalities. Clinical data for sixteen cases treated at the Jordan University Hospital are summarized. In Jordan human and cultural customs are related to scorpion stings. Sting accidents according to age groups and seasons are given.

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