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Biomedical subjects

C B Cropp

Publications and source records attributed to C B Cropp.

48 records · Page 3Linked to original sources
PubMed1981

Arbovirus infections among laboratory personnel in Ibadan, Nigeria.

Laboratory-acquired infections encountered between 1963 and 1977 among personnel of the Virus Research Laboratory, Ibadan, Nigeria, are reported. Two cases of chikungunya infection occurred and one each with Dugbe, Wesselsbron, and dengue viruses. In each case, virus was isolated or development of antibody demonstrated. Among virus and two each to chikungunya and Rift Valley fever viruses, without experiencing any clinically recognized disease.

Adult↗
PubMed1981

Diagnosis of eastern equine encephalomyelitis by immunofluorescent staining of brain tissue.

Brain tissues were obtained from 5 horses with clinical encephalomyelitis during an epizootic in southwestern Michigan in August-September 1980. These tissues were tested for virus by intracerebral inoculation of suckling mice and by examination of frozen sections and impression smears by the indirect fluorescent antibody (FA) technique. Eastern equine encephalomyelitis virus was isolated and detected by FA technique in brains of 3 horses which died or were euthanatized within approximately 24 hours of onset of the disease but not from 2 horses at 2 and 3 days after onset. The latter 2 animals had serum-neutralizing antibodies at the time of death. Seven areas of the brain of 1 horse were tested. The proportion of fluorescing cells in frozen sections correlated with infectivity titers. Impression smears were negative. Viral titers ranged from 10(5.7) to 10(10.0) suckling mouse intracerebral median lethal doses/g; highest titers and most intense fluorescence were present in the thalamus and pons, emphasizing the need to obtain selective samples of central brain structures for diagnostic examination. The FA technique appears useful for the rapid diagnosis of fatal eastern equine encephalomyelitis and may be applicable in laboratories not equipped for isolation of viruses.

Animals↗
PubMed1980

Variation in virulence for mice and rhesus monkeys among St. Louis encephalitis virus strains of different origin.

The virulence characteristics of 67 strains of St. Louis encephalitis (SLE) virus isolated from various sources in North, Middle, and South America were compared in mice and rhesus monkeys. Each virus strain was titrated in mice exactly 21 days old and virulence was expressed as the ratio of intracerebral (ic)/intraperitoneal (ip) LD50. Virus strains fell into three groups: 1) high virulence (ic/ip LD50 ratio approximately 1.0); 2) intermediate virulence (variable mortality over a wide dose range); and 3) low virulence (ic/ip LD50 less than or equal to 0.00002). Virus strains isolated during Culex pipiens and Cx. nigripalpus--borne epidemics in the eastern United States were highly virulent for mice, whereas a high proportion of the endemic virus strains isolated from Cx. tarsalis in the western United States were attenuated. Virus strains isolated from birds (the usual host for SLE virus) were highly virulent, in contrast to strains from rodents and carnivores, which were attenuated. Isolates from humans exhibited variable virulence characteristics. In experimentally-infected mice, virulence correlated with high viremia, replication in extraneural tissues, and earlier neuroinvasion. Mouse virulence correlated with clinical and histopathologic markers of pathogenicity for ic inoculated rhesus monkeys. Monkeys immunized with nonpathogenic strains by subcutaneous inoculation were partially protected against ic challenge with a virulent virus strain. The virulence classification of SLE virus strains is discussed in terms of epidemiologic correlations. This classification provides a framework for future studies on the antigenic, genetic, and biochemical bases for SLE virus strain variation.

Animals↗
PubMed1980

Recovery of Tonate virus ("Bijou Bridge" strain), a member of the Venezuelan equine encephalomyelitis virus complex, from Cliff Swallow nest bugs (Oeciacus vicarius) and nestling birds in North America.

A second virus with distinct biological, serological, and physiochemical properties was detected as a minority viral subpopulation in specimens of Cliff Swallow nest bugs (Oeciacus vicarius) and nestling bird sera containing Fort Morgan (FM) virus. The second virus, detected by a breakthrough neutralization test employing FM antiserum, was present in 5 of 11 FM virus-positive pools of nest bugs and in 4 of 38 birds from Colorado and South Dakota. The concentration of the second virus was 10-fold to 1,000-fold lower than that of FM virus. The second virus, which was provisionally named "Bijou Bridge" (BB) virus was shown by conventional serological tests to be a member of the Venezuelan equine encephalomyelitis (VEE) complex, and by tests employing antisera to the E2 viral glycoprotein to be identical with Tonate virus, previously isolated from birds and mosquitoes only in French Guiana. Experimental infection of House Sparrows and Cliff Swallows showed that they develop brief BB viremias and antibodies. Oe. vicarius bugs were resistant to oral infection with BB virus. The epidemiological significance of recovery of Tonate virus in North American is discussed.

Animals↗
PubMed1979

Viruses isolated from reptiles: identification of three new members of the family Rhabdoviridae.

The growth of four viruses isolated from lizards in Brazil (Marco, Chaco, and Timbo viruses) and Australia (Almpiwar virus) was studied in a variety of continuous cell lines of mammalian, reptilian, amphibian, and piscine origin. Although replication was found in certain cell lines derived from the coldblooded species, cytopathic effect (CPE) was absent or minimal and growth was less than or equal to that in mammalian cells. Those observations appear to limit the value of poikilothermic cells for primary isolation of viruses from field-collected, cold-blooded vertebrates or arthropods that feed upon them. The four reptilian viruses were found to be naturally occurring temperature sensitive agents, with optima for growth of approximately 30 degrees C. Electron microscope studies showed three of the viruses (Marco, Chaco, and Timbo) to be new members of the family Rhabdoviridae. Marco virus particles were conically shaped and resembled bovine ephemeral fever virus, and two lyssaviruses (Kotonkan and Obodhiang). Chaco and Timbo viruses were cylindrical viruses resembling other rhabdoviruses with particle lengths longer than the prototype VSV. No serologic relationships were found in cross complement fixation tests between these viruses, Marco virus, and 34 other rhabdoviruses.

Animals↗
PubMed1978

Necrotizing myocarditis in mice infected with Western equine encephalitis virus: Clinical, electrocardiographic, and histopathologic correlations.

Western equine encephalitis (WEE) virus was found in myocardial tissue of adult mice during the first five days after inoculation of the virus, with a peak titer (5.0 log plaque-forming units/g) at 24 hr. Light microscopy revealed a multifocal necrotizing myocarditis with a prominent inflammatory response and hyaline and granular degeneration of myofibers. Electron microscopy showed cytoplasmic viral nucleoids and budding and free mature WEE viral particles. Serial electrocardiograms showed the development of disturbances of rate and rhythm, defects in conduction, marked elevation in the ST segment, and low voltage. Myocarditis has not been previously recognized as a complication of alphavirus infection in humans. and we found no evidence for myocardial damage in 11 persons with acute WEE virus infections studied electrocardiographically in 1975. Demonstration of myocarditis in the WEE virus-infected mouse, however, suggests the need to monitor human patients for possible cardiac involvement during future epidemics of WEE virus infection.

Animals↗
PubMed1978

Experimental infection of house sparrows (Passer domesticus) with Rocio virus.

Rocio encephalitis is a new epidemic flaviviral infection of man, first described in São Paulo State, Brazil in 1975. The ecology of the viral transmission cycle remains largely unknown. Experimental studies were undertaken to assess the role of a wild avian species, the House Sparrow, as a maintenance or amplifying host. Approximately two-thirds of nesting and adult sparrows developed 2- to 3-day viremias of low to moderate magnitude (2.0--4.3 log/ml). Rocio-immune birds were not protected against challenge with St. Louis encephalitis (SLE) virus, but prior SLE viral infection prevented detectable viremia in birds challenged with Rocio virus. These studies provide some support for the hypothesis that birds are hosts for Rocio virus, but the House Sparrow probably plays a relatively minor role in viral transmission. Because sparrows are relatively inefficient viremic hosts, they would be expected to play a minor role in transmission should Rocio virus be introduced into the United States.

Animals↗
PubMedDate not supplied

Epidemic dengue 2 in the city of Djibouti 1991-1992.

From October 1991 to February 1992, an outbreak of acute fever (in which thick blood films were negative for malaria) spread rapidly in the city of Djibouti, Djibouti Republic, affecting all age groups and both nationals and foreigners. The estimated number of cases was 12,000. The clinical features were consistent with a non-haemorrhagic dengue-like illness. Serum samples from 91 patients were analysed serologically for flavivirus infection (dengue 1-4, West Nile, yellow fever, Zika, Banzi, and Uganda-S), and virus isolation was attempted. Twelve strains of dengue 2 virus were isolated. Dengue infection was confirmed by a 4-fold or greater rise in immunoglobulin (Ig) G antibody in paired serum specimens, the presence of IgM antibody, or isolation of the virus. Overall, 46 of the suspected cases (51%) were confirmed virologically or had serological evidence of a recent flavivirus infection. Statistical analysis showed that the presence of a rash was the best predictor of flavivirus seropositivity. In November 1992, Aedes aegypti was widespread and abundant in several districts of Djibouti city. A serological study of serum samples collected from Djiboutian military personnel 5 months before the epidemic showed that only 15/177 (8.5%) had flavivirus antibodies. These findings, together with a negative serosurvey for dengue serotypes 1-4 and yellow fever virus performed in 1987, support the conclusion that dengue 2 virus has only recently been introduced to Djibouti.

Adolescent↗