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Biomedical subjects

G G Clark

Publications and source records attributed to G G Clark.

At least 37 records · Page 2Linked to original sources
PubMed1995

Failure of immune sera to neutralize dengue-2 virus in intrathoracically inoculated Aedes aegypti.

Aedes aegypti became infected when inoculated with a mixture of dengue-2 virus and anti-dengue-2 antibodies, but not when they were exposed to the same mixture per os. This phenomenon merits more detailed investigation. Understanding why this difference in mosquito infection rate occurs may lead to improved dengue virus assays or provide insights into the nature of dengue virus-antibody interactions.

Aedes↗
PubMed1995

[The epidemiological situation of dengue in America. The challenges for its surveillance and control].

The recent occurrence of cases of dengue hemorrhagic fever has placed dengue in the agenda of priorities in many countries in the Americas. International efforts directed to the control of the epidemic are supported by the epidemiological surveillance of dengue cases and serotypes while control of the vector is still in need of innovative and more effective measures. These are the challenges to be met by countries in the region, where the laboratory should be incorporated as the key component of the surveillance system. The medical community requires adequate training in the diagnosis and treatment of the severe forms of dengue infection and the community should be deeply involved in the control strategies. Scant resources in the region impose serious constrains to the program which should be comprehensive, intensive and well coordinated. The medical services, the vector control personnel, the surveillance team, the civil authorities and the community have important roles to play in the control of dengue fever.

Aedes↗
PubMed1994

Dengue surveillance--United States, 1986-1992.

PROBLEM/CONDITION: Dengue is an acute, mosquito-transmitted viral disease characterized by fever, headache, arthralgia, myalgia, rash, nausea, and vomiting. The worldwide incidence of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) increased from the mid-1970s through 1992. Although dengue is not endemic to the 50 United States, it presents a risk to U.S. residents who visit dengue-endemic areas. REPORTING PERIOD COVERED: 1986-1992. DESCRIPTION OF SYSTEM: Dengue surveillance in the 50 United States and the U.S. Virgin Islands relies on provider-initiated reports to state health departments. State health departments then submit clinical information and serum samples to CDC for diagnostic confirmation of disease among U.S. residents who become ill during or after travel to dengue-endemic areas and among residents of the U.S. Virgin Islands. In Puerto Rico, an active, laboratory-based surveillance program receives serum specimens from ambulatory and hospitalized patients throughout the island, clinical reports on hospitalized cases, and copies of death certificates that list dengue as a cause of death. Laboratory diagnosis relies on virus isolation or serologic diagnosis of disease (i.e., IgM or IgG antibodies against dengue viruses). RESULTS: In 1986, the first indigenous transmission of dengue in the United States in 6 years occurred in Texas; from the time of that incident through 1992, however, no further endemic transmission was reported. During 1986-1992, CDC processed serum samples from 788 residents of 47 states and the District of Columbia. Among these 788 residents, 157 (20%) cases of dengue were diagnosed serologically or virologically. Of the 157 patients, 71 (45%) had visited Latin America or the Caribbean; 63 (40%), Asia and the Pacific; seven (4%), Africa; and nine (6%), several continents. All four dengue virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4) were isolated from travelers to Asia and the Pacific; however, travelers to the Americas acquired infections with only DEN-1, DEN-2, or DEN-4. Even though the number of laboratory-diagnosed dengue infections among travelers was small, severe and fatal disease was documented. In the U.S. Virgin Islands and Puerto Rico, three serotypes (DEN-1, DEN-2, and DEN-4) circulated during 1986-1992. In Puerto Rico, disease transmission was characterized by a cyclical pattern, with peaks in incidence occurring during months with higher temperatures and humidity (usually from September through November). The highest incidence of laboratory-diagnosed disease (1.2 cases per 1,000 population) occurred among persons < 30 years of age; rates were similar for males and females.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Community-based integrated control of Aedes aegypti: a brief overview of current programs.

Dengue viruses are maintained in endemic transmission cycles in tropical urban areas where epidemics periodically occur. Until about 30 years ago, there were long intervals (10-40 years) between epidemics but they are now occurring in many areas at 3-5-year intervals. These epidemics are most likely caused by virus strains with different epidemic potential. Accompanying this increased frequency in epidemic activity has been a change in the disease pattern with cases of the severe form of dengue (dengue hemorrhagic fever) becoming much more common. The occurrence of these factors and the expanding geographic distribution of dengue hemorrhagic fever in the past 15 years have made it necessary to re-evaluate currently recommended methods for prevention and control. The result has been increasing emphasis on the development of effective sustainable Aedes aegypti control programs based on source reduction using community participation. A brief overview of global programs using this approach is presented with emphasis on the Puerto Rican program, one of the earliest developed.

Aedes↗
PubMed1994

Use of the "CDC backpack aspirator" for surveillance of Aedes aegypti in San Juan, Puerto Rico.

We constructed a battery-powered backpack aspirator to collect adult Aedes aegypti mosquitoes. This simple, easily constructed aspirator facilitates the indoor collection of this important vector species. The collections made with the aspirator provide useful information about the biology and behavior of Ae. aegypti that can be used in education and vector control programs and in the evaluation of ultra-low volume insecticide spray programs directed against this species. The cost for construction is ca. $150.

Aedes↗
PubMed1993

Detection of multiple blood feeding in Aedes aegypti (Diptera: Culicidae) during a single gonotrophic cycle using a histologic technique.

We evaluated a histologic technique for its usefulness in detecting multiple blood feeding by Aedes aegypti (L.) in a single gonotrophic cycle. To standardize the procedure, we carried out a laboratory study in which 166 mosquitoes imbibed two blood meals at known intervals. Eighty percent (78/98) of the multiple meals were detected when the interval between meals was from 1 to < to = 24 h and the time from the second meal to fixation ranged from 0 to 12 hr. At intervals outside this range, only 34% (23/68) of the multiple meals were detected. Overall, 61% (101/166) of the double meals were detected. Examination of 96 engorged Ae. aegypti collected by aspiration from inside houses in San Juan, Puerto Rico, indicated that 50% had imbibed multiple meals. Most wild-caught mosquitoes took their last meal the day before capture, and most multiple feeders fed twice on consecutive days. A dark line of digested blood, or heme, around the first meal and a physical separation between meals were the most useful histologic parameters for detecting multiple feeding in wild Ae. aegypti. An association of multiple feeding with advanced stages of oocyte development suggests that, at the time of collection, most Ae. aegypti from the study site had fed twice in each gonotrophic cycle. We conclude that, although it is labor intensive, histologic examination is an appropriate technique for a longitudinal, community-wide survey of multiple feeding by Ae. aegypti.

Aedes↗
PubMed1992

Mosquito vector control and biology in Latin America--a second symposium.

The second Spanish language symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 58th Annual Meeting in Corpus Christi, TX in March 1992. The principal objective, as it was for the 1991 symposium, was to increase and stimulate greater participation in the AMCA by vector control specialists and public health workers from Latin America. This publication includes summaries of 25 individual presentations that were given in Spanish. The symposium included the following topics: biology and chemical control of Aedes aegypti and anopheline vectors of malaria; field and laboratory studies of biological control agents for Aedes aegypti; community participation in the prevention of dengue; and other various aspects of the biology of other medically important arthropods (e.g., Simulium ochraceum, Lutzomyia and Culicoides).

Aedes↗
PubMed1992

Dengue activity in Puerto Rico, 1990.

Reported dengue activity in Puerto Rico (PR) increased in 1990 for the fourth consecutive year. The Community Hygiene Division of the PR Health Department received 9,540 reports of suspected dengue cases. Of the blood samples obtained from 7,660 patients, 1,911 were confirmed as dengue infection by laboratory tests at the Dengue Branch, San Juan Laboratories, Centers for Disease Control. Dengue 2 (DEN-2) continued to be the most frequently isolated serotype among all confirmed cases, hospitalized patients, and the confirmed cases with hemorrhagic manifestations. Disease was reported throughout the island and during all months, but activity, as in previous years, was lowest from April through July, and highest from September to November. The highest rates of laboratory-confirmed illness occurred in towns on the south coast and in the central mountains, with only one or two circulating virus serotypes (DEN-2 in the south; DEN-2 and DEN-4 in the central mountains). Although cases were confirmed in infants and octogenarians, the majority of laboratory-confirmed cases (1,293, 68%), and the highest attack rates (0.70/1000), were reported in persons younger than 30. Of patients with confirmed cases, 289 (15%) were hospitalized, and 438 (23%) reported at least one hemorrhagic manifestation. One presumptive dengue case with fatal outcome was reported in 1990 in a 17-year-old woman in whom a febrile illness, seizures, and coma developed; she died after cardiorespiratory arrest. Recent dengue infection in this individual was serologically documented, but no virus was isolated.

Adolescent↗
PubMed1991

Effects of single introduction of Toxorhynchites moctezuma upon Aedes aegypti on a Caribbean Island.

In March 1989, first instar Toxorhynchites moctezuma larvae were introduced into all potential Aedes aegypti oviposition sites (n = 214) that contained water in the village of Clifton on Union Island in St. Vincent and The Grenadines. One month after this introduction, the mean number of adult Ae. aegypti collected with a backpack aspirator in houses in Clifton dropped significantly. Sixty-four percent fewer males and 80% fewer females were collected after introduction of the predator. In the untreated village of Ashton, the overall drop was 24%, with males showing an increase of 27% and females a drop of 55%. The average wing length of females collected in Clifton increased slightly, whereas it remained the same in Ashton.

Aedes↗
PubMed1989

Egg of Aedes (Gymnometopa) mediovittatus (Diptera: Culicidae).

The egg of Aedes mediovittatus (Coquillett) is described from scanning electron micrographs. The egg is black, slightly tapered toward the posterior pole, and is approximately 771 microns long and up to 175 microns wide. On the entire egg surface there are about 970 polygonal outer chorionic cells, each bounded by a raised outer chorionic reticulum which forms a wall around each cell. Incorporated into the inner surface of this wall are 13-18 relatively small, poorly defined and variably shaped tubercles. In the center of each cell there is a large, buttonlike, more or less round tubercle with a pitted upper surface. Over most of the egg surface, the walls of this tubercle are connected by spokelike bridges of variable diameter to the cell floor or reticulum wall. The structure of the outer chorionic cells is somewhat modified in areas approaching the anterior and posterior poles.

Aedes↗
PubMed1988

Vector potential of selected North American mosquito species for Rift Valley fever virus.

Selected North American mosquito species were evaluated as potential vectors of Rift Valley fever virus. Field populations of Aedes canadensis, Ae. cantator, Ae. excrucians, Ae. sollicitans, Ae. taeniorhynchus, Ae. triseriatus, Anopheles bradleyi-crucians, Culex salinarius, Cx. tarsalis, and Cx. territans perorally exposed to 10(6.2)-10(7.2) plaque forming units of Rift Valley fever virus readily became infected. Infection rates ranged from 51% (65/127) for Cx. salinarius to 96% (64/67) for Ae. canadensis. Disseminated infection rates were generally greater at 14 days than at 7 days after the infectious bloodmeal, and, with the exception of An. bradleyi-crucians, they were not significantly different than the pooled rate of 59% for each species tested. Only 5/55 (9%) of the An. bradleyi-crucians developed a disseminated infection. For most of the species, about half of the mosquitoes with a disseminated infection transmitted an infectious dose of virus to hamsters. While all species, with the exception of An. bradleyi-crucians, transmitted virus, Ae. canadensis, Ae. taeniorhynchus, and Cx. tarsalis had the highest vector potential of the species tested. Following inoculation of approximately 10(1.6) plaque forming units of virus, 100% of the mosquitoes of each species became infected. For most species, transmission rates were similar for inoculated individuals and those that developed a disseminated infection following peroral infection. Viral titers of transmitting and nontransmitting-disseminated individuals were similar for all species tested. These data suggest that, if Rift Valley fever virus was introduced into North America, several mosquito species would be capable of transmitting it.

Aedes↗
PubMed1988

Malpais spring virus: a new vesiculovirus from mosquitoes collected in New Mexico and evidence of infected indigenous and exotic ungulates.

Two virus isolates, 1 each from Aedes campestris and Psorophora signipennis mosquitoes collected in south central New Mexico in August 1985, were shown by neutralization tests to be identical to each other, but not to any of more than 250 arthropod-borne and other viruses. Electron microscopy of 1 isolate (85-488NM, chosen as the prototype) indicated that this strain shares morphologic characteristics with viruses of the family Rhabdoviridae. Indirect fluorescent antibody tests indicated that this virus is a member of the genus Vesiculovirus, but is not closely related to any of the North American or other rhabdoviruses with which it was tested, including vesicular stomatitis (Indiana) and vesicular stomatitis (New Jersey) viruses. The name Malpais Spring virus is proposed for this newly recognized vesiculovirus. A serologic survey indicated that Malpais Spring virus infects indigenous (mule deer and pronghorn) and exotic (gemsbok) ungulates at and near the sites where the mosquitoes from which the virus strains were isolated were collected. Antibody prevalence in wild animals indicates that the pronghorn and gemsbok may play roles as hosts for Malpais Spring, epizootic hemorrhagic disease (New Jersey), and bluetongue viruses in this area.

Aedes↗
PubMed1987

Congenital corneal anesthesia with retinal abnormalities, deafness, unusual facies, persistent ductus arteriosus, and mental retardation: a new syndrome?

Two sibs who had hypesthetic corneas, absence of the peripapillary choriocapillaris and retinal pigment epithelium, sensorineural hearing loss bilaterally, persistent ductus arteriosus, moderate mental retardation, and unusual facial appearance are described. Their mother had mild to moderate sensorineural hearing loss, retinal changes and similar facial features. The differential diagnosis is discussed. We believe this is a clinically distinct syndrome with autosomal dominant inheritance.

Abnormalities, Multiple↗
PubMed1987

Antibody response of sandhill and whooping cranes to an eastern equine encephalitis virus vaccine.

As a possible strategy to protect whooping cranes (Grus americana) from fatal eastern equine encephalitis (EEE) viral infection, studies were conducted to determine the immune response of this species and sandhill cranes (Grus canadensis) to a formalin-inactivated EEE viral vaccine. Viral-specific neutralizing antibody was elicited in both species after intramuscular (IM) vaccination. Subcutaneous and intravenous routes of vaccination failed to elicit detectable antibody in sandhill cranes. Among the IM vaccinated cranes, the immune response was characterized by nondetectable or low antibody titers that waned rapidly following primary exposure to the vaccine. However, one or more booster doses consistently elicited detectable antibody and/or increased antibody titers in the whooping cranes. In contrast, cranes with pre-existing EEE viral antibody, apparently induced by natural infection, exhibited a rapid increase and sustained high-antibody titers. Even though EEE virus vaccine induced neutralizing antibody and produced no adverse side effects, further studies will be required to determine the protective efficacy of the antibody.

Alphavirus↗
PubMed1986

Mortality of captive whooping cranes caused by eastern equine encephalitis virus.

Of 39 captive whooping cranes (Grus americana), 7 died during a 7-week period (Sept 17 through Nov 4, 1984) at the Patuxent Wildlife Research Center, Laurel, Md. Before their deaths, 4 cranes did not develop clinical signs, whereas the other 3 cranes were lethargic and ataxic, with high aspartate transaminase, gamma-glutamyl transferase, and lactic acid dehydrogenase activities, and high uric acid concentrations. Necropsies indicated that the birds had ascites, intestinal mucosal discoloration, fat depletion, hepatomegaly, splenomegaly, and visceral gout. Microscopically, extensive necrosis and inflammation were seen in many visceral organs; the CNS was not affected. Eastern equine encephalitis (EEE) virus was isolated from specimens of the livers, kidneys, lungs, brains, and intestines of 4 of the 7 birds that died, and EEE virus-neutralizing antibody was detected in 14 (44%) of the 32 surviving birds. Other infectious or toxic agents were not found. Morbidity or mortality was not detected in 240 sandhill cranes (Grus canadensis) interspersed among the whooping cranes; however, 13 of the 32 sandhill cranes evaluated had EEE virus-neutralizing antibody. Of the 41 wild birds evaluated in the area, 3 (4%) had EEE virus-neutralizing antibody. Immature Culiseta melanura (the most probable mosquito vector) were found in scattered foci 5 km from the research center.

Animals↗