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Biomedical subjects

W C Reeves

Publications and source records attributed to W C Reeves.

At least 127 records · Page 7Linked to original sources
PubMed1990

Distribution of neutralizing antibodies to California and Bunyamwera serogroup viruses in horses and rodents in California.

Neutralization tests were done on sera from 141 horses from high elevation regions of California. Antibody prevalences to Jamestown Canyon, snowshoe hare, and California encephalitis viruses in the California serogroup and Northway virus in the Bunyamwera serogroup were 55%, 43%, 18%, and 46%, respectively. In 51 horses from rural low elevation regions, seroprevalences were 31%, 35%, 35%, and 37%, respectively. Twenty-four horses from a suburban lowland area were seronegative, except for a single horse with a low titer to snowshoe hare virus. Seroprevalence to Jamestown Canyon and snowshoe hare viruses was associated with increasing age. Only 2 of 177 rodents from the Sierra Nevada had antibodies to Northway virus; none had antibodies to Jamestown Canyon or snowshoe hare viruses.

Animals↗
PubMed1990

Seroepidemiology of human T cell lymphotropic virus in the Republic of Panama.

The human T-lymphotropic virus (HTLV) and associated diseases, adult T cell leukemia and spastic paraparesis, appear to be endemic in southwestern Japan and the Caribbean. This cross-sectional population-based study was conducted to describe the seroepidemiology of HTLV in the Republic of Panama. HTLV antibody was measured by first generation and commercial ELISA tests and confirmed by competitive binding ELISA, a radioimmunoassay for anti-p 24, and Western blot. Of 3,231 subjects greater than or equal to 15 years of age, 135 (4.2%) had antibody detected in ELISA screening tests, but because only 20% were confirmed positive, HTLV seroprevalence varied from 0.2-2% throughout the Republic. Infection with HTLV clustered in Guaymi Indians living in Bocas del Toro province (9.9% prevalence rate). With the exception of Guaymi Indians, no major geographic, urban/rural, male/female or racial differences in antibody prevalence were observed; specifically, HTLV infection rates were not elevated in black Panamanians. Clustering of infection in an isolated Amerind population must be further investigated. The small proportion of screen-positive sera which confirmed positive illustrates the importance of strict uniform criteria for seropositivity.

Binding, Competitive↗
PubMed1990

Neurocysticercosis in Panama: preliminary epidemiologic study in the Azuero region.

Neurocysticercosis was not been reported from Panama until 1984. The first documented case was a 5-year-old male who lived with his family in a typical subsistence agriculture environment lacking all sanitary amenities. Pigs and other animals ranged freely in and around the home. This report concerns clinical studies of the patient and his family conducted 4 years later. The index case had neurologic sequelae and was strongly seropositive. A cerebral CT scan revealed multiple intracerebral calcifications. Three family members had antibody to Cysticercus detected by immunoblot assay. A 7-year-old seropositive sister had an intracerebral calcification detected by CT scan. All 6 family members had completely normal neurologic examinations.

Adolescent↗
PubMed1990

Human T cell lymphotropic virus infection in Guaymi Indians from Panama.

Preliminary studies found that 9% of Guaymi Indians from Bocas del Toro province have antibody to human T cell lymphotropic virus (HTLV-I/II). The present study enrolled 317 (21% of the population) Guaymi Indians from Changuinola, the capital of Bocas del Toro province and 333 (70% of the population) from Canquintu, an isolated rural village. Demographic information and family relationships were ascertained and subjects were screened for neurologic diseases. Serum specimens were screened by an enzyme-linked immunosorbent assay for HTLV-I/II antibody and positives were confirmed according to U.S. Public Health Service criteria. Twenty-five (8%) Guaymi residing in Changuinola and 7 (2.1%) from Canquintu were confirmed seropositive. In Changuinola, antibody was virtually limited to residents greater than or equal to 15 years of age (24 [16%] of 153) and rates were slightly higher in males than in females; in Canquintu, antibody rates did not increase significantly with age and appeared higher in females than in males. In Changuinola, there was no evidence for household clustering of infection. In contrast, HTLV antibody among Canquintu residents clustered significantly by household. HTLV-associated neurologic disease was not detected in either population. The atypical seroepidemiology observed in both locations might be explained if the virus endemic to the Guaymi differed from HTLV-I previously described in the Caribbean basin and Japan.

Adolescent↗
PubMed1990

Persistence of mosquito-borne viruses in Kern County, California, 1983-1988.

The persistence of arboviruses was studied from 1983 to 1988 in mixed agriculture, marsh, riparian, and foothill habitats in Kern County, CA. Western equine encephalomyelitis (WEE) virus was isolated frequently during 1983 from Culex tarsalis and Aedes melanimon and was detected by the seroconversion of sentinel chickens. WEE virus then disappeared, even though vector competence studies during 1984-1986 showed that Cx. tarsalis was able to transmit WEE virus. St. Louis encephalitis (SLE) virus was detected sporadically in 3 of the 6 years of the study by isolation from Cx. tarsalis and/or by sentinel chicken seroconversion. When mosquito pools were screened for virus in suckling mice, Turlock (TUR) and Hart Park (HP) viruses were isolated from Cx. tarsalis during each summer. Vertical transmission of HP was indicated by the isolation of virus from a pool of male Cx. tarsalis. California encephalitis (CE) virus was isolated repeatedly from host-seeking Ae. melanimon females, males, and adults reared from field-collected immatures, verifying vertical transmission in nature. Horizontal transmission of CE virus among both jackrabbits (Lepus californicus) and desert cottontails (Sylvilagus auduboni) appeared to amplify Ae. melanimon infection rates during the summer of 1985, but elevated herd immunity depressed infection rates during 1986. Thus, CE, HP, and TUR viruses persisted in Kern County, while WEE virus appeared to become extinct and required reintroduction. The sporadic occurrence of SLE virus activity remains unexplained, but its persistence may require both vertical transmission and reintroduction.

Aedes↗
PubMed1990

Daily survivorship of adult Aedes communis in a high mountain environment in California.

Using mark-release-recapture methods and linear regression analysis, daily survivorship for 3 groups of Aedes communis in a high mountain environment in the Sierra Nevada of California were estimated to be 0.90, 0.91 and 0.88, respectively. Multiple recaptures of marked females were made for up to 33 days after release. Precise estimates were not made of gonotrophic cycle lengths. However, parity data, based on dissections of samples of marked and unmarked females, suggest the length of gonotrophic cycles was between 1 and 2 weeks.

Aedes↗
PubMed1990

[The risk factors of invasive carcinoma of the cervix uteri in Latin America].

A study of 759 patients with invasive cervical cancer, 1,430 controls, and 689 sexual partners of the participants who declared that they were monogamous was conducted in Colombia, Costa Rica, Mexico, and Panama from January 1986 to June 1987, to evaluate the risk factors associated with this neoplasm. The principal risk factors identified were: initiation of sexual relations by the woman at an early age, number of stable sexual partners (relationships of more than three months' duration), number of liveborn children, presence of DNA from human papilloma virus (HPV) types 16 or 18, history of venereal disease, lack of exposure to early detection programs, deprived socioeconomic conditions, and number of sexual partners of the partners of the monogamous women. Smoking increased the risk in those women who were shown to have DNA from HPV types 16 or 18. Fifty percent of the patients and 29% of the controls said they had never had a cytological examination (Papanicolaou test). No association was observed between the presence of HPV and sexual behavior. The study showed the need for further research on the possible mechanisms involved in carcinogenesis and infection. The common denominators of the risk factors mentioned are underdevelopment and poverty, which affect broad sectors of these populations. Mass detection programs targeting high-risk groups can reduce the high incidence of cervical cancer in Latin America.

Age Factors↗
PubMed1990

Risk factors for invasive carcinoma of the uterine cervix in Latin America.

A study of 759 cervical cancer patients, 1,430 controls, and 689 sex partners in four Latin American countries has made it possible to assess the influence of multiple factors upon the risk of invasive cervical cancer. The principal risk factors identified were the woman's age at first coitus, the number of her steady sex partners, her number of live births, the presence of DNA from human papillomavirus (HPV) types 16 or 18, a history of venereal disease, nonparticipation in early detection programs, and low socioeconomic status. There is good reason to believe that extensive detection programs directed mainly at high-risk groups in the Americas can reduce the high incidence of cervical cancer in this Region.

Adult↗
PubMed1990

[Neurologic diseases associated with the HTLV-1 virus in Panama].

Studies of the prevalence of the human T-cell lymphotropic virus (HTLV-1) in 1984 to 1986 in the Republic of Panama revealed a national seroprevalence of 1 to 2%. Since 1985 clinical epidemiological studies of neurological diseases associated to HTLV-1 are being done. Two hundred and fitly six clinical cases of thirty eight different neurological diseases of unknown etiology studied in the Neurology Services of the Santo Tomas Hospital and the Social Security Metropolitan Hospital Complex have been associated in some way to the HTLV-1. Twelve cases of progressive spastic paraparesis were identified and related to HLTV-1 as an etiologic agent. The ratio of men to women was maintained at 1:1 with the average age at onset at 44 years and without racial preference. There are important doubts about the association of this virus to multiple sclerosis. The seroprevalence of the HTLV-1 virus in Panama is found to be similar to that reported in neighboring countries and the association of tropical spastic paraparesis to THLV-1 infection is identified.

Adult↗
PubMed1989

Regional distribution of human papillomavirus DNA and other risk factors for invasive cervical cancer in Panama.

A population-based national cancer registry has documented strikingly different regional incidence rates of cervical cancer in the Republic of Panama. Such regional differences in disease rates could represent regional differences in the occurrence of risk factors, in particular, human genital papillomaviruses (HPV). This study enrolled newly diagnosed invasive cancer patients in the Republic of Panama over an 18-mo period. Behavioral risk factors were measured by interviewing cases and matched controls. In addition, DNA extracted from biopsies of the cancers was tested for HPV sequences. Early age at first coitus, multiple pregnancies, and nonparticipation in Pap smear screening programs were significant risk factors for cervical cancer in this population. These factors and low levels of education occurred more frequently among women residing in regions with higher cancer rates than women residing in the region with lower cancer rates. HPV DNA was detected most frequently (70%) among cases from the region with the lowest cancer rate (30 of 100,000) and least frequent (54%) among cases where the cancer rate was the highest (51 of 100,000). The observations suggest that risk factors other than HPV contribute to the differences in cervical cancer rates among women residing in various regions of Panama.

Age Factors↗
PubMed1989

The male factor in the etiology of cervical cancer among sexually monogamous women.

To address the hypothesis that male sexual behavior may affect the etiology of invasive cervical cancer, a case-control study was undertaken in Panama, Costa Rica, Colombia and Mexico. The study enrolled husbands of those women with invasive cervical cancer and of those age-matched controls who reported only one lifetime sexual partner. A total of 204 case and 485 control husbands (78% and 72%, respectively, of identified husbands) were interviewed, clinically examined, and had penile swabs taken for papillomavirus assays. Risk increased significantly (p = 0.005) with the number of sexual partners reported by the husband (RR = 2.0 for 26+ vs. less than 6 partners). Low educational status of the husband was also an important predictor of risk, possibly indicating the role of unmeasured aspects of sexual behavior. Visits to prostitutes, circumcision status and sexually transmitted disease histories were not important predictors of risk, but evidence from clinical examination indicated that poor genital hygiene may be involved. Human papillomavirus (HPV) expression as defined by filter in situ hybridization was detected in 20-23% of subjects and, except in the small group with both HPV types 6/11 and 16/18, was not related to risk. This may reflect sampling problems in the male or the importance of host factors which enhance viral carcinogenicity in the female.

Circumcision, Male↗
PubMed1989

Human T-cell leukemia virus-I and hematologic malignancies in Panama.

Serum samples were obtained in a 2-year period (November 1, 1984-December 31, 1986) from 136 Panamanian patients with hematologic malignancies identified by a population-based registry designed for studies investigating human T-cell lymphotropic virus (HTLV)-I. Only three patients had clinical and serologic findings of HTLV-I-associated adult T-cell leukemia/lymphoma (ATLL). The authors conclude that although classical HTLV-I-associated ATLL occurs in the Panamanian population, it is not as prevalent as in other Caribbean populations.

Aged↗
PubMed1989

Human papillomavirus infection and cervical cancer in Latin America.

To evaluate a possible association between infection with human papillomavirus (HPV) and cervical cancer, we performed a multicenter case-control study in Latin America of 759 cases of invasive cervical cancer and 1467 randomly selected age-matched controls. Demographic, sexual, behavioral, and other clinical data were obtained by interview, and HPV DNA was assayed in cervical-swab specimens with use of filter in situ hybridization. Cervical infection with HPV 16 or 18 or both was strongly associated with cervical cancer. HPV DNA was detected in 62 percent of the cases but only 32 percent of the controls, and the relative risk of cancer increased from 2.1 (95 percent confidence interval, 1.6 to 2.8) to 9.1 (6.1 to 13.6) with hybridization reactions of increasing strength. Although the number of sexual partners, age at first intercourse, number of live births, and Pap-smear history were also significant risk factors, the strong associations between infection with HPV 16 or 18 or both and cervical cancer persisted after we adjusted for these variables. These observations are consistent with the hypothesis that genital infection with HPV 16 or 18 may have a role in the pathogenesis of cervical cancer. Other well-known risk factors were also identified in the study, but they did not affect the association between HPV and cervical cancer.

Adult↗
PubMed1989

Invasive cervical cancer and smoking in Latin America.

A case-control study of 667 patients with invasive squamous cell carcinoma of the cervix and 1,430 controls from four Latin American countries showed an age-adjusted relative risk (RR) of 1.2 [95% confidence interval (CI) = 1.0-1.4] for women who had ever smoked, with risk rising to 1.7 (95% CI, 0.8-3.6) for women who smoked greater than or equal to 30 cigarettes per day. The associations were practically eliminated after adjustment for the number of sexual partners and alcohol consumption, probably a surrogate for an unidentified life-style risk factor. Some excess risk persisted among women who smoked for extended periods (RR = 1.5 for greater than or equal to 40 yr), as well as those who began smoking at older ages (RR = 1.7 for greater than 30 yr), which suggests a late-stage effect. In addition, among women who tested positive for human papillomavirus (HPV) type 16 or 18 by filter in situ hybridization, there was an increased risk for women who had ever smoked and a dose-response relationship with the number of cigarettes smoked (adjusted RRs compared with HPV-negative nonsmokers = 5.0 for HPV-positive nonsmokers, 5.5 for less than 10 cigarettes/day, and 8.4 for greater than or equal to 10 cigarettes/day). In contrast, HPV-negative women had no increased risk associated with smoking. These results, from a high-incidence area where intensive smoking among women is still relatively rare, suggest that smoking has a limited effect on cervical cancer risk, possibly only among women with specific types of HPV.

Age Factors↗
PubMed1989

Genital human papillomavirus infection in Panama City prostitutes.

Little is known of the natural history of genital human papillomavirus (HPV) infections in women from high-risk populations. Samples were collected from 183 Panama City prostitutes and assessed for HPV (filter in situ DNA hybridization) and for sexually transmitted agents. The cohort was followed for 8 mo; 51% of subjects completed four monthly return visits and 16% were sampled eight times. The proportion of women found infected with HPV increased significantly with increasing numbers of consecutive samples tested; 38 (21%) of 183 women were positive after one visit and 46 (82%) of 56 who completed six visits were infected. The pattern of viral detection over time was not random, which implied that most prostitutes were persistently infected with genital HPVs and that either scattered foci of infection or periodic reactivation of latent virus occurred. Our findings suggest that multiple sampling is necessary to accurately estimate HPV infection rates and to define whether patterns of DNA expression are present.

Adolescent↗