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D L Huxsoll

Publications and source records attributed to D L Huxsoll.

At least 19 recordsLinked to original sources
PubMed1992

Narrowing the zone of uncertainty between research and development in biological warfare defense.

Although "research" is not prohibited by the Biological Weapons Convention, States Parties to the Convention have maintained the spirit of the Convention in actions relating to research. The confidence-building measures agreed to at RC2 refer to research facilities, publication of research results, and promotion of contacts between scientists engaged in research related to the Convention. However, assessment of basic research on biological agents is not a productive way to distinguish an offensive from a defensive program. Additionally, if a country were to initiate a biological weapons program, basic research on biological agents may not be necessary. For example, the extensive published research on Bacillus anthracis, both as a cause of anthrax in cattle and other species and as a biological-warfare agent, would enable any motivated group or nation to initiate a biological weapons program that could immediately advance to the development and scale-up stages. Research on biological agents for offensive purposes would be characterized by activities such as selection for growth, virulence, and toxin production; improving stability under varying environmental conditions; and selection of strains that might overcome existing means of prophylaxis and treatment. A biological program with an offensive intent would in most cases be characterized by evidence of development efforts in mass production and dissemination, which are often agent-specific. Thus, an assessment of development may distinguish offensive from defensive programs. If a country were to initiate a biological weapons research program, and were willing to risk worldwide condemnation should existence of such a program become known, it is likely that such a program would include development and production capabilities. If a country were not committed to production capability, there would be no rationale for an offensive biological research that would bring worldwide condemnation. Critics of the U.S. Biological Defense Research Program have suggested that the program could easily and quickly be turned into an offensive effort. To accomplish this, however, we have to assume that all military personnel, including the civilians employed by the Department of the Army, are unethical and willing to break the law and run the risk of placing the U.S. in a noncompliance status. The Army is under constant scrutiny by governmental agencies, by visiting scientists, by audiences at scientific meetings, by scientists who review manuscripts for publications, by news media, and by private citizens.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological Warfare↗
PubMed1990

Excess of seminomas observed in Vietnam service U.S. military working dogs.

During the Vietnam War, US military working dogs served with their companion dog handlers in close proximity, sharing common exposures to war-related activity, many zoonotic infectious agents, chemical pesticides, phenoxy herbicides, and extensive use of therapeutic drugs. To gain insight into the effects of the Vietnam experience, we investigated the occurrence of neoplasms in military working dogs based on standard necropsy examination by the Armed Forces Institute of Pathology. We observed that these dogs experienced significant elevated risks for testicular seminoma and, independently, testicular dysfunction. Experimental evidence shows testicular dysfunction and impaired spermatogenesis in laboratory animals exposed to phenoxy herbicides, dioxin, or tetracycline, and antibiotic used extensively in military working dogs in Vietnam. Because an unexplained significant decrease in sperm quality in Vietnam veterans has been observed by the Centers for Disease Control, further research is warranted if we are to clarify military service in Vietnam as a risk factor for testicular dysfunction. The testis should be made a priority site in the study of Vietnam experience-related cancers.

Animals↗
PubMed1985

Adaptation of Ehrlichia sennetsu to canine blood monocytes: preliminary structural and serological studies with cell culture-derived Ehrlichia sennetsu.

Ehrlichia sennetsu, the causative agent of human sennetsu rickettsiosis, was successfully propagated in primary canine blood monocyte cultures. The growth cycle of this organism appears to be similar to that of Ehrlichia canis. The antigen derived from our E. sennetsu cultures was used to develop an indirect fluorescent antibody test for detection and titration of serum antibodies to the organism. Using this test system, we found that five human serum samples obtained from patients clinically diagnosed as having sennetsu rickettsiosis were positive for anti-E. sennetsu antibodies. In addition, 29% of the serum samples obtained from 200 patients having a fever of unknown origin and residing in various regions of Malaysia were also serologically positive. All sera from apparently healthy individuals were negative in the test. Dogs inoculated with cell culture-adapted E. sennetsu developed a significant specific antibody titer to E. sennetsu, and the organism was subsequently isolated from their blood. These animals showed no clinical evidence of disease. The possibility of a higher prevalence of human sennetsu rickettsiosis in Southeast Asia and the potential usefulness of the canine model for studies of human sennetsu rickettsiosis are discussed.

Animals↗
PubMed1984

Febrile illness in Malaysia--an analysis of 1,629 hospitalized patients.

We studied 1,629 febrile patients from a rural area of Malaysia, and made a laboratory diagnosis in 1,025 (62.9%) cases. Scrub typhus was the most frequent diagnosis (19.3% of all illnesses) followed by typhoid and paratyphoid (7.4%); flavivirus infection (7.0%); leptospirosis (6.8%); and malaria (6.2%). The hospital mortality was very low (0.5% of all febrile patients). The high prevalence of scrub typhus in oil palm laborers (46.8% of all febrile illnesses in that group) was confirmed. In rural Malaysia, therapy with chloramphenicol or a tetracycline would be appropriate for undiagnosed patients in whom malaria has been excluded. Failure to respond to tetracycline within 48 hours would usually suggest a diagnosis of typhoid, and indicate the need for a change in therapy.

Adolescent↗
PubMed1982

Serological analysis of Rickettsia tsutsugamushi isolates from North Queensland.

Fifty-two Rickettsia tsutsugamushi isolates from humans, rodents and chiggers in North Queensland were serologically characterized by the direct immunofluorescence test. A majority (71%) of the isolates was a mixture of two or more strains. The most frequently detected strains in the 52 isolates were TA716 (84%), TA763 (42%), TA686 (33%), and Karp (31%). The Gilliam strain was detected in only 4% of the isolates.

Animals↗
PubMed1982

Doxycycline propylaxis for human scrub typhus.

The use of doxycycline, as a prophylactic antibiotic against scrub typhus was investigated in a prospective, randomized, double-blind study. Twenty volunteers were divided into two similar groups. Beginning three days before exposure to Leptotrombidium fletcheri chiggers infected with Rickettsia tsutsugamushi, and continuing for six weeks after exposure, one group received weekly 200-mg oral doses of doxycycline and the other group received a placebo. Nine of 10 doxycycline-treated subjects remained well during prophylaxis but developed antibody to scrub typhus, whereas nine of 10 subjects given the placebo required treatment for scrub typhus. Therefore, the efficacy of the regimen in preventing scrub typhus was 89% (eight cases prevented of nine expected). Ten days after successfully completing prophylaxis, eight of nine subjects reported minor self-limiting symptoms. A single dose of doxycycline was given on day 3 of illness to volunteers who developed scrub typhus. Such therapy was initially effective but was frequently followed by relapse and cannot be recommended.

Adult↗
PubMed1982

Rickettsia sennetsu in human blood monocyte cultures: similarities to the growth cycle of Ehrlichia canis.

Microscopic examination of cultured human monocytes infected with Rickettsia sennetsu and stained by the Giemsa method revealed the presence of various organismal growth forms in the cytoplasm of the infected cells. The growth forms were loosely scattered individual organisms, clusters of organisms, various sizes of dense inclusion bodies in intact and vacuolated cytoplasm, and organisms in close proximity to disintegrated monocytes. The appearance and the morphology of these R. sennetsu growth forms were similar to those of Ehrlichia canis propagated in canine monocytes. Specific identification of R. sennetsu was made by staining cultured monocytes with fluorescein-conjugated globulins extracted from the pooled sera of patients recovering from sennetsu rickettsiosis. Mice infected with cultured R. sennetsu developed gross pathological changes indicative of infection, and the organism was demonstrated in their spleens, peritoneal macrophages, and mononuclear blood cells. Human monocyte culture appeared to be more sensitive than the previously used African green monkey kidney cell line (BSC-1) for the isolation of R. sennetsu from samples containing minute infectious quantities of this organism.

Animals↗
PubMed1982

Characterization of Rickettsia tsutsugamushi strains in two species of naturally infected, laboratory-reared chiggers.

The strains of Rickettsia tsutsugamushi found in naturally infected, laboratory-reared Leptotrombidium (Leptotrombidium) arenicola and L. (L.) fletcheri chiggers were characterized by direct immunofluorescence (FA) and by mouse and monkey virulence tests. The strains existing in the L. (L.) arenicola chiggers consisted of different combinations of TA716, TA763, TA686, Karp, and Kato. In addition to these five strains, Gilliam was found in the L. (L.) fletcheri chiggers. Results indicate that individual chiggers can be simultaneously infected with several antigenic strains of R. tsutsugamushi. Although these antigens appear to remain stable within familial lines when several generations were viewed, the antigenic patterns observed in two succeeding generations did not always correlate. This variable expression of antigens was considered to be due to a quantitative fluctuation from one generation to the next in the strains of rickettsiae combined with a lack of sensitivity of the direct FA test in detecting small numbers of antigenically different rickettsiae. Phenotypic variation was considered to be a less probable explanation. Morbidity and mortality were minimal in ICR mice fed upon by individual chiggers of either species, but infection rates were 85-99%. Tissue suspensions prepared from mice infected by L. (L.) arenicola produced higher mortality and longer duration of illness in mice than those prepared from L. (L.) fletcheri-infected mice. Silvered leaf and cynomolgus monkeys were fed upon by the two species of chiggers or inoculated with the mouse tissue suspensions. In both cases, minimal clinical responses were observed.

Animals↗
PubMed1982

Transmission of scrub typhus to human volunteers by laboratory-reared chiggers.

Laboratory-reared, Rickettsia tsutsugamushi-infected Leptotrombidium arenicola and L. fletcheri chiggers were fed on 1 and 2 human volunteers respectively. All subjects developed typical clinical signs and symptoms of scrub typhus beginning days 8-10 post chigger attachment (PCA); these included fever, severe headache, myalgia, regional lymphadenopathy, and eschar. The two L. fletcheri subjects developed a transient generalized rash on days 3-4 after the onset of fever, and these two individuals also appeared to suffer a more severe clinical disease. Rickettsemias were detected in all three volunteers beginning on day 7 PCA, 1-3 days before the onset of clinical disease. Rises in indirect fluorescent antibody titers occurred starting on days 13-19 PCA (day 4-11 post fever) and in Weil-Felix OXK titers starting on days 26-22 PCA (days 7-14 post fever). These results strongly suggest that the use of laboratory-reared chiggers is a reliable means of transmitting scrub typhus infections to volunteers.

Adult↗
PubMed1981

Clinical and immunologic responses of silvered leaf monkeys (Presbytis cristatus) to experimental reinfection with Rickettsia tsutsugamushi.

Silvered leaf monkeys (Presbytis cristatus) that had recovered from active Rickettsia tsutsugamushi infections 14 months previously became rickettsemic when inoculated with homologous, related, or unrelated strains of R. tsutsugamushi. In contrast to the results after the initial infection that produced disease, no signs were observed after the subsequent infections. Most animals responded with detectable titers of antibody to the Karp antigen regardless of the inoculated strains. Strains recovered during rickettsemia usually had antigens related only to the challenge strains, but in three silvered leaf monkeys, antigens characteristic of both the original and the challenge strains were detected.

Animals↗
PubMed1981

Evidence of a serologic relationship between Ehrlichia canis and Rickettsia sennetsu.

A serologic relationship between Rickettsia sennetsu, the etiologic agent of human sennetsu rickettsiosis in western Japan, and Ehrlichia canis, the agent of canine ehrlichiosis, has been demonstrated. Using the indirect fluorescent antibody test, convalescent sera from patients with sennetsu fever reacted with Ehrlichia canis antigen. In the direct fluorescent antibody test, immunoglobulins from four patients with sennetsu rickettsiosis stained E. canis morulae in canine monocytes. This finding is significant in view of the morphologic uniqueness of the two agents and a lack of serologic relatedness with other major rickettsial agents.

Adolescent↗
PubMed1981

Rickettsia tsutsugamushi strains found in chiggers collected in Thailand.

R. tsutsugamushi strains found in chiggers collected from 3 different sites throughout Thailand were antigenically characterized. Monotypic infections were observed in 76.7% of the chiggers. Karp was the most predominant strain, followed by TA716, TA763, TA686 and Kato. This study represents the first confirmed report of R. tsutsugamushi infection in 8 different chigger species in Thailand.

Animals↗