Molecular epidemiology of Bartonella species isolated from ground squirrels and other rodents in northern California.

Bartonella spp. are endemic in wild rodents in many parts of the world. A study conducted in two northern California counties (Sonoma and Yolo) sampling California ground squirrels (Otospermophilus beecheyi) and four other rodent species (Peromyscus maniculatus, P. boylii, P. truei and Neotoma fuscipes) led to the isolation of small Gram-negative bacilli which were identified as Bartonella spp. based on colony morphology, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and partial gene sequencing. Overall, Bartonella spp. were isolated from the blood of 71% (32/45) of the ground squirrels and one third (22/66) of the other rodents. PCR-RFLP analysis of the gltA and 16S rRNA genes yielded seven unique profiles, four for the ground squirrels and three for the other rodents. Isolates from each PCR-RFLP profiles were submitted for partial sequencing. Ground squirrel isolates were most closely related to B. washoensis, whereas the other rodent isolates were closest to B. vinsonii subsp. vinsonii and B. vinsonii subsp. arupensis. Two of these three species or subspecies are known zoonotic agents.

An Improved PCR Protocol For Detection of Babesia duncanI In Wildlife and Vector Samples.

Human babesiosis is a tick-borne protozoal disease of increasing clinical significance in North America. Most cases in the eastern and Midwestern regions of the United States are reportedly due to Babesia microti infections. By contrast, most human infections reported in California and Washington have been attributed to a new species that was first identified in 1991 and subsequently named Babesia duncani. Although the tick vector and mammalian reservoir hosts for B. microti are well characterized, the vector and reservoir hosts for B. duncani are unknown. As a result, specific risk factors for human infections cannot be characterized. Identification of potential hosts and vector species has been hampered by the lack of specific and sensitive molecular diagnostic tools to amplify parasite DNA. To address this need, a nested PCR assay targeting the ß-tubulin gene, a well-conserved locus in piroplasm parasites with a highly variable intron region among species, was developed. The assay was evaluated by spiking tick and mammalian DNA extracts with DNA from a B. duncani isolate derived from a human patient (WA-1) as well as related Babesia spp. from Californian wildlife. This assay was highly specific, with a sensitivity of approximately 1 copy of template DNA in a background of tick DNA. At this level of detection B. duncani was detectable in larval tick samples, and the target locus allowed for visual differentiation between species by gel electrophoresis. This assay offers researchers a new tool for elucidating the natural transmission cycle of B. duncani.

Human babesiosis: an emerging tick-borne disease.

Human babesiosis is an important emerging tick-borne disease. Babesia divergens, a parasite of cattle, has been implicated as the most common agent of human babesiosis in Europe, causing severe disease in splenectomized individuals. In the US, Babesia microti, a babesial parasite of small mammals, has been the cause of over 300 cases of human babesiosis since 1969, resulting in mild to severe disease, even in non-splenectomised patients. Changing ecology has contributed greatly to the increase and expansion of human babesiosis in the US. A relatively recently described babesial parasite, the WA1-type, has been shown to be the causative agent in seven human cases in the western US. This parasite is closely related to babesial parasites isolated from large wild ungulates in California. Like B. microti, WA1-type parasites cause mild to severe disease and the immunopathogenesis of these parasites is distinctly different from each other in experimental infections of hamsters and mice. A B. divergens-like parasite was also identified as the cause of a fatal human babesiosis case in Missouri. Isolated cases of human babesisosis have been described in Africa and Mexico, but the causative parasites were not well characterized. Standard diagnostic techniques for human infection, such as examination of Giemsa-stained thin blood smears and serology, have been complemented with molecular techniques, such as PCR. Current treatment for babesiosis is focused on a regimen of clindamycin and quinine, although new drugs have shown promise. Prevention of infection relies on self-monitoring for the presence of ticks and, in some locations, targeted application of pesticides to decrease tick abundance. Identification of human infection with Babesia spp. will probably increase as physicians and the public become more aware of the disease, as people live and recreate in rural tick-infested areas, and as the numbers of immunocompromised individuals increase.

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.

Description and epidemiology of Theileria youngi n. sp. from a northern Californian dusky-footed woodrat (Neotoma Fuscipes) population.

An epidemiologic study designed to identify the small mammal reservoir for the zoonotic WA1-type babesial parasite resulted in the discovery of a small, intraerythrocytic piroplasm in smeared blood from dusky-footed woodrats (Neotoma fuscipes) in northern California. The woodrat parasites were isolated and compared to other piroplasm parasites based on their morphology, antigenicity, and genetic characteristics. These studies indicated that the woodrat parasites were not the WA1-type babesial agent but were of the genus Theileria. We accordingly named it Theileria youngi. The prevalence in the woodrat population was high (61%). Infection was unrelated to gender or age of the woodrats. Potential vectors for this tick-transmitted parasite included 3 species of ticks recovered from the woodrats. Dermacentor occidentalis, Ixodes woodi, and Ixodes pacificus. Mostly larval or nymphal stages were recovered, suggesting transstadial transmission is possible. This is the first piroplasm fully characterized from a dusky-footed woodrat.

Babesia leo n. sp. from lions in the Kruger National Park, South Africa, and its relation to other small piroplasms.

Babesia leo, a small piroplasm isolated from lions in South Africa is described as a distinct species based on a phylogenetic analysis of the 18S rRNA gene. Intraerythrocytic trophozoite and merozoite stages of B. leo are morphologically indistinguishable from other small piroplasms of felids. Previous studies showed that B. leo was biologically and antigenically distinct from B. felis, which is known to infect wild and domestic felids in South Africa. Molecular characterization showed strong support for the phylogenetic seperation of B. leo as a distinct species from B. felis and other felid piroplasms. Phylogenetic analysis also showed that Babesia microti and all of the felid piroplasms from Africa with known 18S rRNA gene sequences available, including B. leo, formed a single, separate clade, sister to the other babesial and theilerial piroplasm parasites.

Seroprevalence of two Babesia spp. isolates in selected bighorn sheep (Ovis canadensis) and mule deer (Odocoileus hemionus) populations in California.

Sera from 111 bighorn sheep (Ovis canadensis) and 95 mule deer (Odocoileus hemionus) were tested using an indirect immunofluorescence assay for antibodies to two isolates of Babesia spp. recently obtained from these hosts in California (USA). The study populations were from six locations: three areas of real or potential sympatry of bighorn sheep and deer, one area with deer only, and two areas with bighorn sheep only. Antibody titers from seroreactive individuals were similar with both babesial isolate antigens (P < 0.05), and seroprevalence was highest in the areas of host sympatry. A moderate to high seroprevalence (> or = 30%) in some of the study populations was evidence that babesial parasites may be common in bighorn sheep and mule deer in some areas of California.

Phylogenetic relationships of human and wildlife piroplasm isolates in the western United States inferred from the 18S nuclear small subunit RNA gene.

The 18S nuclear small subunit ribosomal RNA gene of piroplasms from wildlife and human cases of babesiosis in the western USA were isolated by PCR and sequenced. Phylogenetic analyses of these sequences and comparisons with sequences from other Babesia and Theileria species revealed that piroplasm isolates from the human cases were indistinguishable from some of the isolates from the western wildlife species, most notably the isolates from mule deer (Odocoileus hemionus). These results suggest that large ungulates may serve as reservoirs for human piroplasm infection. The western piroplasm isolates from humans and wildlife formed a distinct clade, separate from other piroplasms found worldwide.

Seroepidemiology of emerging tickborne infectious diseases in a Northern California community.

A seroprevalence and risk factor study of emerging tickborne infectious diseases (Lyme disease, ehrlichiosis, and babesiosis) was conducted among 230 residents of a semirural community in Sonoma County, California. Over 50% of residents reported finding a tick on themselves in the preceding 12 months. Samples from 51(23%) residents were seroreactive to antigens from one or more tickborne disease agents: 1.4% to Borrelia burgdorferi, 0.4% to Ehrlichia equi, 4.6% to Ehrlichia chaffeensis, and 17.8% to the Babesia-like piroplasm WA1. Only 14 (27%) of these seroreactive residents reported one or more symptoms compatible with these diseases. Seroreactivity was significantly associated with younger age (<16 years), longer residence in the community (11-20 years), and having had a physician's diagnosis of Lyme disease. In northern California, the risk of infection with these emerging tickborne diseases, particularly in children, may be greater than previously recognized.

Transfusion-transmitted babesiosis in Washington State: first reported case caused by a WA1-type parasite.

Most cases of babesiosis reported in the United States have been tickborne and caused by Babesia microti, the etiologic agent of all previously described transfusion-transmitted cases. A 76-year-old man with the first recognized case of transfusion-transmitted infection with the recently identified WA1-type Babesia parasite is described. The subject received multiple blood transfusions in 1994. Indirect immunofluorescent antibody testing of serum from 57 blood donors implicated a 34-year-old man (WA1 titer, 1:65,536) whose donation had been used for packed red cells. Isolates of the organisms that infected the recipient and the donor, both of whom were spleen-intact residents of Washington State, were obtained by hamster inoculation. The DNA sequence of a 536-bp region of the nuclear small subunit-rRNA gene of both isolates was identical to that of WA1 (isolated in 1991 from the index WA1 case-patient). Effective measures for preventing transmission of babesiosis by blood transfusion are needed.

Theileriosis in a Missouri beef herd caused by Theileria buffeli: case report, herd investigation, ultrastructure, phylogenetic analysis, and experimental transmission.

A 6-year-old Simmental cow infected with Theileria buffeli had a clinical disease characterized by theilerial parasitemia, macrocytic normochromic anemia with acanthocytosis and spherocytosis, lymphoid hyperplasia (lymphocytosis, edematous lymphadenomegaly), dysproteinemia, evidence of liver disease, and a low serum antibody titer against T. buffeli. The cow was in a herd in which all cattle originated in Missouri; 22/75 (29%) of cattle had a theilerial parasitemia and 26/75 (35%) had titers to T. buffeli of > or =1:160. Classification of the Missouri bovine organism as T. buffeli was based on DNA sequencing and comparison to sequences for T. buffeli and Theileria sp. type A obtained from GenBank. Intraerythrocytic veils and piroplasms were seen during transmission electron microscopy. The organism was successfully transmitted to two splenectomized calves, which developed mild anemias while parasitemic. Blood from the second calf was used as the source of T. buffeli antigen for an indirect immunofluorescence antibody test. Theilerial isolates from a Missouri white-tailed deer were also sequenced and resembled Theileria sp. types F and G and were not consistent with the bovine organism.