Two Ehrlichia pathogens were found in immature Ixodes ricinus (L.) ticks collected from migratory passerine birds in the Curonian Spit area of the Baltic Region of Russia (Kaliningrad enclave). During the spring and fall of 2000, 1,606 passerine birds (eight species) were collected; 6.8% of them (110/1,606) were infested by ticks, and 51.8% (57/110) of tick clusters contained various human pathogenic microorganisms. Human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) agents were found in 14% (8/57) of cases. Borrelia afzelii, Borrelia garinii, and Borrelia burgdorferi sensu stricto were found in 92.9% (53/57) of the ticks. In five out of eight cases, infection of both Ehrlichia and Borrelia were obtained. In one case, a single nymph contained HME, B. afzelii, and B. garinii. Borrelia burgdorferi s.s. and B. afzelii were found together in one pool of four nymphs and one larva. All agents were identified using polymerase chain reaction and species-specific primers. In 8.8% of the ticks collected from birds in the fall and 22% in the spring, pathogens were isolated from attached co-feeding nymphs and larvae. These data demonstrate that Ehrlichia exchange could occur between co-feeding ticks on animals without systemic infection.

Field male Aedes aegypti (L.) and Aedes albopictus (Skuse) adults caught from fixed monitoring stations weekly for 1 yr were screened for dengue viruses (DEN-1, DEN-2, DEN-3, and DEN-4). The assay was carried out using a single-step reverse transcription (or transcriptase)-polymerase chain reaction (PCR) (RT-PCR) followed by a semi-nested PCR using an upstream consensus primer and four type-specific primers within the nonstructural protein three gene (NS3) of dengue viruses. The diagnostic fragments for DEN-1, DEN-2, DEN-3, and DEN-4 serotypes were of sizes 169, 362, 265, and 426 bp, respectively. Results showed that in Singapore 1.33% and 2.15% of Aedes aegypti and Aedes albopictus adult male mosquitoes, respectively, were positive for dengue viruses. The serotypes detected in male Ae. aegypti was DEN-1 (44%), followed by DEN-2 (22.2%) and DEN-3 (22.2%), and DEN-4 (11.1%). For Aedes albopictus males, the serotype was DEN-4 (38.9%), followed by DEN-2 (33.3%), DEN-3 (16.7%), and DEN-1 (11.1%).

Surveillance for mosquito-borne viruses was conducted in Barkedji area from 1990 to 1995, following an outbreak of Rift Valley fever (RVF) virus in southern Mauritania. Mosquitoes, sand flies, and midges were collected from human bait and trapped by solid-state U.S. Army battery-powered CDC miniature light traps baited with dry ice or animals (sheep or chickens) at four ponds. Overall, 237,091 male and female mosquitoes representing 52 species in eight genera, 214,967 Phlebotomine sand flies, and 2,527 Culicoides were collected, identified, and tested for arboviruses in 9,490 pools (7,050 pools of female and 331 of male mosquitoes, 2,059 pools of sand flies and 50 pools of Culicoides). Viruses isolated included one Alphavirus, Babanki (BBK); six Flaviviruses, Bagaza (BAG), Ar D 65239, Wesselsbron (WSL), West Nile (WN), Koutango (KOU), Saboya (SAB); two Bunyavirus, Bunyamwera (BUN) and Ngari (NRI); two Phleboviruses, Rift Valley fever (RVF) and Gabek Forest (GF); one Orbivirus, Ar D 66707 (Sanar); one Rhabdovirus, Chandipura (CHP); and one unclassified virus, Ar D 95537. Based on repeated isolations, high field infection rates and abundance, Culex appeared to be the vectors of BAG, BBK, Ar D 65239 (BAG-like), and WN viruses, Ae. vexans and Ae. ochraceus of RVF virus, Mansonia of WN and BAG viruses, Mimomyia of WN and BAG viruses, and Phlebotomine of SAB, CHP, Ar D 95537, and GF viruses. Our data indicate that RVF virus circulated repeatedly in the Barkedji area.

A total of 152 ixodid ticks (Acari: Ixodidae) consisting of nine species was collected from 82 passerine birds (33 species) in 14 locations in Canada from 1996 to 2000. The Lyme disease spirochete Borrelia burgdorferi Johnson, Schmidt, Hyde, Steigerwaldt & Brenner was cultured from the nymph of a blacklegged tick, Ixodes scapularis Say, that had been removed from a common yellowthroat, Geothlypis trichas L., from Bon Portage Island, Nova Scotia. As a result of bird movement, a nymphal I. scapularis removed from a Swainson’s thrush, Catharus ustulatus incanus (Godfrey), at Slave Lake, Alberta, during spring migration becomes the new, most western and northern record of this tick species in Canada. Amblyomma longirostre Koch, Amblyomma sabanerae Stoll, and Ixodes baergi Cooley & Kohls are reported for the first time in Canada. Similarly, Amblyomma americanum L., Amblyomma maculatum Koch, and Ixodes muris Bishopp & Smith are reported for the first time on birds in Canada. After removal of an I. muris gravid female from a song sparrow, Melospiza melodia Wilson, at St. Andrews, New Brunswick, eggs were laid, which developed into larvae, and this new tick-host record demonstrates that birds have the potential to start a new tick population. We conclude that passerine birds disperse several species of ixodid ticks in Canada, and during spring migration translocate ticks from the United States, and Central and South America, some of which are infected with B. burgdorferi.

The detection of cryptic species by biochemical methods indicates that within the phlebotomine fauna morphological data are not always adequate for species diagnosis. Cellulose acetate and polyacrylamide enzyme electrophoresis methods were compared for their effectiveness in identifying 13 species of Venezuelan phlebotomine sand flies and resolving alleles. Eight diagnostic loci unambiguously separated these 13 species of sand flies. Although acrylamide was as effective as cellulose acetate in species separation, differences were detected in the resolution of some alleles. Cellulose acetate identified more alleles at Ak and Fum, and resolved better at Pgm, whereas acrylamide identified more alleles at Gpi, Mdh, and Me. Therefore, erroneous species diagnoses may occur, if diagnostic loci detected by one technique are used by a second technique without adequate reference standards.

The survival and molting incidence of fifth-instar nymphs of Panstrongylus megistus (Burmeister, 1835), a vector of Chagas’ disease, were investigated following sequential heat shocks in which a mild shock (35 or 40°C, 1 h) preceded a more drastic one (40°C, 12 h). The shocks were separated by 8-, 18- 24-, or 72-h periods at 28°C. The heat-shock tolerance response was more effective when the first shock was given at 40°C. When the period between shocks was 18 h, the tolerance to sequential shocks (in terms of specimen survival) weakened, which suggested a transient control of the process that enables the organism to circumvent the unfavorable effects of severe shock. In terms of molting incidence, the heat-shock tolerance was only demonstrated when the period between the first shock at 40°C for 1 h and the second shock at 40°C for 12 h was ≥24 h. These results are the first to demonstrate the induction of heat-shock tolerance in a blood-sucking hemipteran.

Effects of fetal bovine serum (FBS) and complement on phagocytic activity in Ornithodoros moubata (Murray 1877) hemocytes and protease activity in the hemocytes were examined. At least three morphologically different cell types, granulocytes, plasmatocytes, and prohemocytes, were detected in hemolymph of O. moubata, and granulocytes and plasmatocytes showed phagocytic activity. FBS altered phagocytic activity of granulocytes, and complement affected phagocytic activity of plasmatocytes. Ticks were inoculated with fluorescent polystyrene beads in combination with FBS or complement. The average number of beads in granulocytes was significantly higher in the FBS injected group than the control (P < 0.01). The percentage of bead-ingesting plasmatocytes in complement inoculated ticks was significantly lower than that in heat-inactivated complement inoculated and control ticks (P < 0.05). Proteases of tick hemocytes localized in small granules in the cytoplasm not only in phagocytic hemocytes but also in prohemocytes. Results suggested modulation of tick hemocyte function through serum components, and digestion of phagocytosed foreign bodies in the hemocytes.

We investigated some entomological factors underlying altitudinal prevalence variation in the Venezuelan Amazonia human onchocerciasis focus. Spatial and temporal variation in relative abundance, daily biting rate, proportion of parous flies, and monthly parous biting rate were studied for the three main simuliid vectors (based on their vectorial competence: Simulium oyapockense s.l. Floch & Abonnenc ≈ S. incrustatum Lutz ≪ S. guianense s.l. Wise). Yanomami villages were selected among sentinel communities of the ivermectin control program, representing hypo- to hyperendemicity conditions of infection. Spatial variation was explored via increasing village altitude on two river systems (A: Ocamo-Putaco and B: Orinoco-Orinoquito). Temporal variation was studied between 1995 and 1999 by sampling the biting population during dry and rainy months. Environmental variables included monthly rainfall and maximum river height. Simuliid species composition itself varied along the altitudinal and prevalence gradient. S. oyapockense s.l. prevailed below 150 m. Above this altitude and up to 240 m, S. incrustatum and S. guianense s.l. became more frequently and evenly collected along A but not along B, where S. incrustatum remained absent. The daily biting rate of S. oyapockense s.l. was higher during the dry season along A, whereas the converse took place along B. Daily biting rate of S. incrustatum was lowest during early rains. By contrast, the daily biting rate of S. guianense s.l. was highest during this period. There was a significant negative cross-correlation between proportion of parous of S. oyapockense s.l. and river height (2 and 3 mo lagged), whereas this variable (1 and 2 mo lagged) was positively correlated with the proportion of parous flies for S. incrustatum. Monthly parous biting rate values suggest that the months contributing most to onchocerciasis transmission in the area are likely to be the dry season and the transition periods between seasons.

The impact of permethrin-treated bednets on the feeding and house entering/exiting behavior of malaria vectors was assessed in two studies in western Kenya. In one study, matched pairs of houses were allocated randomly to receive bednets or no bednets. Exiting mosquitoes were collected in Colombian curtains hung around half of each house; indoor resting mosquitoes were collected by pyrethrum spray catches. The number of Anopheles gambiae Giles and An. arabiensis Patton estimated to have entered the houses was unaffected by the presence of bednets; Anopheles funestus Giles was less likely to enter a house if bednets were present. Anopheles gambiae and An. funestus were less likely to obtain a blood meal and significantly more likely to exit houses when bednets were present. No difference was detected in An. arabiensis rates of blood feeding and exiting. In a second experiment, hourly night biting collections were done on 13 nights during the rainy season to assess whether village-wide use of permethrin-treated bednets caused a shift in the time of biting of malaria vectors. A statistically significant shift was detected in the biting times of An. gambiae s.l., although the observed differences were small. No change was observed in the hourly distribution of An. funestus biting. Our study demonstrated that, at least in the short-term, bednets reduced human-vector contact and blood feeding success but did not lead to changes in the biting times of the malaria vectors in western Kenya.

It generally is assumed that the daily probability of survival of wild adult mosquitoes is independent of age. To test this assumption we conducted mark-release-recapture studies in Puerto Rico and Thailand to determine if estimated daily survival rates between two different age cohorts of the dengue vector Aedes aegypti (L.) were the same. Survivorship was estimated with nonlinear regression analysis using bootstrapping to obtain estimates of errors. Initial recapture success of the younger cohort was greater than the older cohort at both locations. Our analysis revealed a significantly greater survival rate for the younger cohort of females in Puerto Rico, and no significant differences between age cohorts in Thailand. For comparison, a traditional approach for analyzing these type of data, linear regression of log-transformed captures over time (exponential model), was used to calculate the probability of daily survival based on slopes of linear regression lines for recaptured mosquitoes. With this method, the estimated daily survival rate of older females (13–23 d old) was significantly greater than survival of younger ones (3–13 d old) in Puerto Rico and Thailand. In addition, short-range movement of mosquitoes was observed in Puerto Rico; maximum dispersal distance detected was 79 m. Survival rates of adult Ae. aegypti may be age-dependent and nonlinear regression analysis is a sensitive approach for comparing patterns of mosquito survival based on mark, single release, multiple recapture data.

We investigated how constant temperatures of 22, 24, and 26°C experienced across the full life cycle affected the dynamics of caged populations of Aedes albopictus (Skuse). All cages were equipped with plastic beakers that served as sites for oviposition and larval development. We measured the per capita daily mortality and emergence rates of the adults and size of adult females, and estimated the intrinsic rate of increase (r) and asymptotic density (K) for each caged population. Populations at 26°C had greater intrinsic rates of increase and lower asymptotic densities than populations at 22 and 24°C. Populations at high temperatures initially had greater daily per capita emergence rates, and steeper declines in per capita emergence rate as density increased over the course of the experiment. There was no temperature effect on the size of adult females nor on the per capita daily mortality rate of adults. Results indicated that populations of Ae. albopictus occurring in regions with relatively high summer temperatures are likely to have high rates of population growth with populations of adults peaking early in the season. These populations may attain relatively low peak densities of adults. Populations occurring in regions with low summer temperatures are likely to experience slow, steady production of adults throughout the season with population size peaking later in the season, and may attain higher peak densities of adults. High temperature conditions, associated with climate change, may increase the rate of spread of Ae. albopictus by increasing rates of increase and by enhancing colonization due to rapid population growth.

Total protein, lipid, and glycogen of Aedes vexans (Meigen) were related linearly to body size at eclosion. Starvation after emergence led to the determination of minimal irreducible amounts of protein, lipid, and glycogen and the availability of the teneral reserves, whereas access to sucrose revealed the potential for reserve synthesis. Glycogenesis and lipogenesis increased reserves ≈10-fold the teneral value within 1 and 2 wk after emergence, respectively. Carbohydrate feeding was an essential behavior before blood feeding and oogenesis commenced. Female flight was tested on a flight mill. Maximal flights of 10–17 km in a single night occurred at 2 wk posteclosion and paralleled maximal reserve syntheses. Comparisons of our laboratory data to host-seeking mosquitoes in the field confirmed our data. The vast majority of maternal lipid was transferred to the yolk when a blood meal was taken, but only a quarter of the blood protein was recovered from mature ovaries. Maternal glycogen was used mainly for flight. Fecundity varied between 20 and 120 eggs per female and was determined largely by body size and blood meal volume. At 27°C, maximal egg numbers were produced, but at 22 and 17°C the caloric yolk content was greater. Females from the southern United States were smaller than females from northern areas. However, southern females had similar fecundity as northern females, and their flight performances were similar. Differences in the reproductive physiology between this species and Ae. aegypti were discussed.

Basic ecophysiological data are presented on the development and reproduction of Aedes albopictus (Skuse) that were reared and maintained at four temperatures between 12 and 32°C. Median larval developmental time from hatching to pupation was correlated inversely with temperature, lasting 7 d at 32°C and up to 28 d at 12°C. Duration of the pupal period also varied from 2–3 d at 32°C to 7–12 d at 12°C. This extension of larval development elongated the phagoperiod and gave rise to larger imagoes. Based on wing length measurements, body sizes varied from 10 to 57 mm³ for females and from 10 to 30 mm³ for males. The caloric protein content at emergence showed a linear and significant regression with body size, independent of sex, treatment, or temperature. Teneral lipid content also followed a linear relationship with body size at warmer temperatures, whereas at low temperatures it increased exponentially with body size. Glycogen was always below 10% of the protein or lipid levels. Reserves at emergence determined median adult survival times, which ranged from 16 d at 32°C to 100 d at 17°C. Access to sucrose solution allowed females to increase their teneral glycogen up to fourfold within 1 wk, and their lipids up to 10-fold within 2 wk. Despite a broad variation, the number of mature oocytes (15–110 eggs per female) was correlated positively with body size, but inversely with the rearing and maintenance temperature. Utilization of the blood meal protein for oogenesis ranged between 35 and 50%, again inversely correlated with temperature; absolute compositions per oocyte were 6.3–6.5 mcal of protein but ranged from 5 to 7 mcal of lipid.

As done previously with adult females of Culex pipiens pallens Coquillett, a mixture of 17 amino acids was infused into the hemocoel of females of seven anautogenous and one autogenous mosquito species belonging to three genera. In Culex. p. quinquefasciatus Say, Cx. tritaeniorhynchus Giles, Cx. kyotoensis Yamaguti & LaCasse, Aedes albopictus (Skuse), Armigeres subalbatus (Coquillett), and Cx. p. molestus Forskal, which previously had laid autogenously matured first batch of eggs, ovarian development was stimulated and frequently continued to maturity. In most mosquitoes, the number of mature follicles nearly doubled when the period of infusion was extended from 24 to 48 h. Therefore, the two previously indicated roles of amino acids, one to initiate ovarian development and the other to regulate the number of maturing oocytes, were confirmed in these species. In Cx. halifaxii Theobald and Ae. japonicus (Theobald), however, the frequency of activation and maturation of ovaries was low compared with the other species, indicating that those species may require some factors other than an increase in amino acids for normal ovarian development after a blood meal.

Ivermectin has potent systemic activity against numerous species of nematodes and arthropods, but there are some important species in these two groups, such as the cat flea, Ctenocephalides felis (Bouché), that appear to be refractory to it. In an effort to determine if the lack of systemic activity against C. felis is specific to ivermectin, or if it is a class-wide phenomenon, 20 avermectin derivatives were tested in an artificial membrane flea feeding system at concentrations of 20, 10, and 1 μg/ml. Results showed that ivermectin had LC₉₀ and LC₅₀ values against fleas of 19.1 and 9.9 μg/ml, respectively. Only four of the other 19 compounds evaluated possessed both LC₉₀ and LC₅₀ values more potent than ivermectin and even then the advantage was modest. Among those four compounds was a two-fold increase in potency relative to ivermectin when the LC₉₀ values were considered (range, 9.2–10.3 μg/ml) and a two- to eight-fold increase when the LC₅₀ values were examined (range, 1.23–5.26 μg/ml). Neither the possession nor the number of oleandrosyl sugars on the macrocyclic backbone were relevant for additional flea activity because among these four compounds were two disaccharides, a monosaccharide and an aglycone. Also, bond disposition between C-22 and 23 did not contribute to increase in activity because these molecules comprise members with either single or double bonds. One of these avermectin analogs was scaled-up and tested subcutaneously in a dog at >100 times the commercial ivermectin dosage and zero efficacy was observed against the flea. We conclude that even the best in vitro avermectin does not have the in vivo potential to become a commercial oral or subcutaneous flea treatment for companion animals.

Japanese encephalitis (JE) virus first appeared in Australia in 1995, when three clinical cases (two fatal) were diagnosed in residents on Badu Island in the Torres Strait, northern Queensland. More recently, two confirmed human JE cases were reported in the Torres Strait Islands and Cape York Peninsula, in northern Queensland in 1998. Shortly after JE virus activity was detected in humans and sentinel pigs on Badu Island in 1998, adult mosquitoes were collected using CO₂ and octenol-baited CDC light traps; 43 isolates of JE virus were recovered. Although Culex sitiens group mosquitoes yielded the majority of JE isolates (42), one isolate was also obtained from Ochlerotatus vigilax (Skuse). Four isolates of Ross River virus and nine isolates of Sindbis (SIN) virus were also recovered from members of the Culex sitiens group collected on Badu Island in 1998. In addition, 3,240 mosquitoes were speciated and pooled after being anesthetized with triethylamine (TEA). There was no significant difference in the minimum infection rate of mosquitoes anesthetized with TEA compared with those sorted on refrigerated tables (2.8 and 1.6 per 1,000 mosquitoes, respectively). Nucleotide analysis of the premembrane region and an overlapping region of the fifth nonstructural protein and 3′ untranslated regions of representative 1998 Badu Island isolates of JE virus revealed they were identical to each other. Between 99.1% and 100% identity was observed between 1995 and 1998 isolates of JE from Badu Island, as well as isolates of JE from mosquitoes collected in Papua New Guinea (PNG) in 1997 and 1998. This suggests that the New Guinea mainland is the likely source of incursions of JE virus in Australia.

Newly engorged nymphs of the lone star tick, Amblyomma americanum (L.), were continuously exposed to 4 μg/cm² of pyriproxyfen residues in glass vials. Treatment of engorged nymphs (n = 285) resulted in significant molting inhibition, with more than one-fourth (26.7%, n = 76) of nymphs dying before or during ecdysis. Treatment effects were evident among ticks that molted to the adult stage, with 26.7% (n = 76) of females, and 17.9% (n = 51) of males exhibiting moribund physical characteristics (i.e., lethargy; dull, discolored and desiccated cuticles; lacking full locomotor competency). A few molted adult ticks (10 males, four females) were dead upon inspection. Only 11.2% of pyriproxyfen treated, emergent females (n = 32), and 11.5% of treated emergent males (n = 25) from 285 ticks treated as engorged nymphs, exhibited “normal” physical appearance and possessed a full range of locomotor activity. Treated adult ticks maintained within a desiccating environmental chamber at 0% RH and 23°C, had significantly accelerated whole-body water loss rates in comparison to untreated males and females maintained under the same environmental conditions. Additionally, treated adult ticks maintained under optimal environmental conditions (23°C and >95% RH) sustained 100% mortality within 32 d following assignment to these conditions (or 79 d posttreatment as engorged nymphs), whereas untreated ticks had 0% mortality for the same duration of time. Results demonstrate that continuous exposure of nymphs to pyriproxyfen disrupted molting, and accelerated both whole-body water loss and subsequent mortality among emergent adult ticks.

The relative potential for a person accidentally acquiring host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say, and lone star tick, Amblyomma americanum (L.), while wearing either of two types of footwear, walking, crawling on hands and knees, and sitting on large fallen logs in deciduous woods, was evaluated. Although flag samples indicated substantial populations of I. scapularis nymphs and low to moderate numbers of A. americanum at the study sites, relatively few I. scapularis and fewer still A. americanum nymphs were acquired during 30-s and 5-min walks. Significantly fewer I. scapularis were picked up when boots were worn with ankles taped (an anti-tick precaution) than when sneakers were worn with socks exposed during 5-min walks, but when thus attired, there was no significant difference between the number of nymphs acquired during 30-s walks. Nymphs of I. scapularis did not appear to accumulate incrementally on footwear or clothing during walks when boots were worn and ankles taped. Crawling for 30 s (≈3 m distance) yielded significantly more I. scapularis nymphs than walking for 30 s. During crawling, I. scapularis nymphs were picked up on 58% of the 30-s samples. Most ticks picked up during crawls were on pant legs. When a flannel flag cloth (0.5 by 0.5 m) was appressed to the upper surface of logs suitable to be sat upon by tired hikers, I. scapularis nymphs were found on 87% of the logs and in 36% of the samples. These data indicate that the potential for contact with host-seeking nymphs of I. scapularis occurring at these densities is greatly elevated by engaging in activities that involve contact with fallen logs and close contact of hands and knees with leaf litter.

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.

The dynamics of the anti-Hypoderma antibody response after a treatment with injectable and pour-on ivermectin against first instars of Hypoderma sp. were determined in naturally infested cows. Cattle were randomly assigned to three groups: group 1, which served as an untreated control; group 2, treated with pour-on ivermectin at a dose of 500 μg/kg of body weight, and group 3, which received 200 μg/kg of body weight of ivermectin by subcutaneous injection. Both ivermectins showed total efficacy against L-1 of Hypoderma sp. In untreated control animals, grubs became detectable in the 2 mo after treatment. Indirect enzyme-linked immunosorbent assay (ELISA) showed a significant increase in group 3 antibody levels 1 mo after treatment, whereas in group 2 the increase was not significant. Following the peak of antibody activity in group 3, antibody levels declined at a faster rate than in those treated topically. In both treated groups, cattle remained serologically positive for 4 mo after ivermectin treatment. Thus, serological surveillance programs for cattle grubs conducted during this posttreatment period will not be influenced by treatment with ivermectin. The persistence of antibody levels after larval destruction makes the indirect ELISA unsuitable for the prediction of the efficacy of treatment.

The ability of Ixodes scapularis Say and Amblyomma americanum (L.) to remain on drags, once acquired, was tested in sparse and dense shrub layer vegetation. When placed on bottoms of drags, adults of both species remained attached for distances three to four times greater in sparse vegetation compared with dense vegetation. When attached to the tops of drags, the differences in retention of ticks on drags between vegetation densities were significant only for A. americanum. In dense vegetation, drags should be checked at 10-m intervals, whereas in sparse vegetation this distance can be extended to 20 m without significant loss of acquired ticks.

A total of 278 bats belonging to 16 species was examined for ticks from various sites in New Mexico from 1994 to 1998. Seven species of bats were parasitized by ticks: larvae of Ornithodoros kelleyi Cooley & Kohls, Ornithodoros rossi Kohls, Sonenshine & Clifford (Argasidae), or both. Both species of ticks are reported from New Mexico for the first time. Infestation prevalences for parasitized bats ranged from 2 to 25% on different host species for O. kelleyi and from 7 to 25% for O. rossi. The pallid bat, Antrozous pallidus, and the big brown bat, Eptesicus fuscus, were parasitized by both tick species. No distinct host specificity was noted for either tick species.