Molecular characterization of a novel Rickettsia species from Ixodes scapularis in Texas.

A novel Rickettsia species of undetermined pathogenicity was detected in Ixodes scapularis. DNA sequencing showed the highest nucleotide sequence similarities with R. australis for the 17 kDa gene, R. helvetica for gltA, and R. montana for rompA. The new organism, provisionally designated as genotype Cooleyi, is highly divergent in three conserved genes from recognized Rickettsia species.

Identification of an uncultivable Borrelia species in the hard tick Amblyomma americanum: possible agent of a Lyme disease-like illness.

Bites from the hard tick Amblyomma americanum are associated with a Lyme disease-like illness in the southern United States. To identify possible etiologic agents for this disorder, A. americanum ticks were collected in Missouri, Texas, New Jersey, and New York and examined microscopically. Uncultivable spirochetes were present in approximately 2% of the ticks. Borrelia genus-specific oligonucleotides for the flagellin and 16S rRNA genes were used for amplification of DNA. Products were obtained from ticks containing spirochetes by microscopy but not from spirochete-negative ticks. Sequences of partial genes from spirochetes in Texas and New Jersey ticks differed by only 2 of 641 nucleotides for flagellin and 2 of 1336 nucleotides for 16S rRNA. Phylogenetic analysis showed that the spirochete was a Borrelia species distinct from previously characterized members of this genus, including Borrelia burgdorferi. Gene amplification could be used to detect these spirochetes in ticks and possible mammalian hosts.

Prevalence of Borrelia (Spirochaetaceae) spirochetes in Texas ticks.

Between 1990 and 1992, ticks from eight Texas parks were collected and analyzed to determine the prevalence of spirochete-infected ticks. Borrelia spirochetes were detected in 1.03% of 5,141 Amblyomma americanum (L.) adults examined, a species Texas residents often encounter. No spirochetes were observed in the other tick species tested.

Isolation of Borrelia burgdorferi from arthropods collected in Texas.

The Texas Department of Health Laboratory cultured arthropods from November 1988 through December 1989 in an attempt to isolate Borrelia burgdorferi, the etiologic agent of Lyme disease. Spirochetes were isolated from eight of 1,093 pools of arthropods cultured. The spirochetal isolates were from several tick and one flea species, including Amblyomma americanum, A. maculatum, Ixodes scapularis, and Ctenocephalides felis. These 8 isolates reacted specifically when treated with monoclonal antibodies to B. burgdorferi. Polyacrylamide gel electrophoresis of six lysates showed them to be virtually identical with strain B31 of B. burgdorferi.

Rickettsia in Texas.

Since the first reported case in 1941, Rocky Mountain spotted fever in humans has been reported from many areas of Texas, with two major foci, one located in the north-central region and the other in the eastern region of the state. During the period 1979-1988, 421 cases of RMSF were reported, reaching 108 cases in 1983 and declining in subsequent years. Statewide surveillance programs to detect spotted fever group rickettsiae in tick populations were initiated in 1976. In recent years, the SFG infectivity rates in these tick species have included Dermacentor variabilis, 5.2%; Amblyomma americanum, 7.1%; Rhipicephalus sanguineus, 2.9%; and Ixodes scapularis, 10.2%. Further determination of involved rickettsial species and pathogenicity is needed, as many of these specimens are collected from humans and during epidemiological investigations. Various foci of murine typhus occur in Texas. During 1979-1988, 400 human cases were reported. The majority of cases occurred in people who resided in south Texas. Several investigations have shown a possible link between typhus infections and exposure to Ctenocephalides felis. Other rickettsial infections currently reported in Texas include Q fever and ehrlichiosis.

Isolation of Borrelia spirochetes from patients in Texas.

The Texas Department of Health Laboratory began culturing the Lyme disease spirochete Borrelia burgdorferi in 1985. This organism was subsequently isolated from blood, cerebrospinal fluid, joint fluid, skin, bone, and autopsy tissues from humans. Fluorescent-antibody tests with murine monoclonal antibodies confirmed that seven of these isolates were B. burgdorferi and that two others belonged to the genus Borrelia.

Inhibition of herpes simplex virus DNA synthesis by pokeweed antiviral protein.

Pokeweed antiviral protein at a concentration of 3 microM inhibited both the synthesis and release of infectious herpes simplex virus type 1 in cell culture by 90 and 99%, respectively. Addition of pokeweed antiviral protein to Vero cell monolayers before virus infection was 10 to 15% more effective in reducing virus yields than was the simultaneous addition of the antiviral protein with virus inoculum. Viral DNA synthesis was inhibited by 90% in cells which had been exposed to the antiviral protein, whereas cellular DNA synthesis was unaffected. No significant inhibition in the synthesis of the majority of viral infected-cell polypeptides was observed early postinfection (7 h), with the exception of infected cell polypeptides 4 and 41, whose syntheses were reduced by 38 and 25%, respectively. At 9 to 21 h postinfection, however, the synthesis of individual infected cell polypeptides was reduced by 48 to greater than 99%.