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Biomedical subjects

J W LeDuc

Publications and source records attributed to J W LeDuc.

At least 73 records · Page 4Linked to original sources
PubMed1983

The role of mosquitoes in the natural history of California serogroup viruses.

California (CAL) serogroup viruses are associated with Aedes mosquitoes and small mammals. Transovarial transmission has been demonstrated for most CAL viruses and probably represents a major survival mechanism of the group. Stabilized infections with highly efficient transovarial transmission have been reported for some CAL viruses. This mechanism, combined with venereal transmission of virus from transovarially infected males to uninfected females, may substantially reduce the amount of vertebrate-mediated amplification required to maintain CAL viruses in nature. Infection with CAL viruses may be associated with detrimental effects in the mosquito vector.

Aedes↗
PubMed1982

Transmission of Oropouche virus from man to hamster by the midge Culicoides paraensis.

Oropouche virus (arbovirus family Bunyaviridae, Simbu serological group) was experimentally transmitted from man to hamster by the bite of the midge Culicoides paraensis. Infection rates and transmission rates were determined after the midge had engorged on patients with viremia. The threshold titer necessary to enable infection or transmission by the midges was approximately 5.3 log10 of the median lethal dose of the virus in suckling mice per milliliter of blood. Transmission was achieved 6 to 12 days after C. paraensis had taken the infective blood meal. This represents conclusive evidence of transmission of an arbovirus of public health importance to man by a member of the Ceratopogonidae family.

Animals↗
PubMed1982

Transmission of hepatitis A virus among recently captured Panamanian owl monkeys.

The presence of antibody to hepatitis A virus (anti-HAV) in 60% of procured owl monkeys (Aotus trivirgatus) held within the United States prompted a study of recently captured A trivirgatus in Panama. Only 2 of 145 newly captured monkeys, but all of 35 A trivirgatus held within a colony for over 100 days, were found to have anti-HAV. Of 41 sero-negative, newly captured monkeys followed prospectively, 25 became infected with hepatitis A virus (HAV) as evidenced by seroconversion or demonstration of virus in the liver at death. Only one monkey that survived over 60 days within the colony was not infected. HAV was identified in the feces of most infected monkeys prior to the development of antibody and was antigenically indistinguishable from human HAV in cross-blocking radioimmunoassays. This colony-centered epizootic provides strong evidence that A trivirgatus is susceptible to HAV and should be investigated further as a potential model of human hepatitis A.

Animals↗
PubMed1982

Serologic evidence of Jamestown Canyon and Keystone virus infection in vertebrates of the DelMarVa Peninsula.

Serological data accumulated during the past decade indicated that a variety of feral and domestic animals of the Delaware-Maryland-Virginia (DelMarVa) Peninsula were infected with Jamestown Canyon (JC) and/or Keystone (KEY) viruses (Bunyaviridae, California serogroup). Neutralizing (N) antibody to JC virus was most prevalent in white-tailed deer, sika deer, cottontail rabbits and horses. KEY virus N antibody was detected most frequently in gray squirrels and domestic goats. N antibody indicative of past infection by one or both viruses also was found in raccoons, horses and humans. JC and/or KEY virus N antibodies were not demonstrable in sera of several other species of small mammals and reptiles. Investigations were extended to evaluate the role of domestic goats as an amplifying host of JC and KEY viruses and to assess their potential as sentinels of virus transmission. Goats maintained in the Pocomoke Cypress Swamp during the summer season of 1978, acquired N antibodies to JC and KEY viruses. Following experimental inoculation with either JC or KEY virus, all goats developed N antibody despite the absence of a demonstrable viremia in most animals. Goats proved to be effective as sentinels for monitoring the transmission of JC and KEY viruses; however, the exceptionally low titers or absence of viremia following inoculation with these viruses would seem to preclude a potential virus-amplifying role for this species. Although findings implicated primarily gray squirrels and white-tailed deer as possible amplifying hosts of KEY and JC virus, respectively, further investigations will be required to clarify their role, particularly since both viruses may be maintained entirely by transovarial transmission.

Aedes↗
PubMed1981

Isolation of St. Louis encephalitis virus from a patient in Belém, Brazil.

St. Louis encephalitis (SLE) virus was isolated from a 21-year-old female hospitalized on 4 October 1978 in Belém, Brazil. Symptomatology on admission included fever, chills, severe headache, abdominal pain, myalgia, arthralgia and jaundice. SLE virus was isolated from her blood drawn on the 8th day of illness and subsequent seroconversion was documented. Serological tests showed the isolate to be closely related to the Belém prototype of SLE virus but distinct from other flaviviruses tested. The patient was discharged without sequelae after 16 days of hospitalization. Epidemiological investigations where the patient worked and lived revealed no evidence of extensive transmission of SLE virus.

Adult↗
PubMed1981

An outbreak of Mayaro virus disease in Belterra, Brazil. I. Clinical and virological findings.

An outbreak of human illness caused by Mayaro (MAY) virus occurred in Belterra, Pará, Brazil in the first half of 1978. A total of 55 cases were confirmed, 43 by virus isolation and serology, and 12 by serology alone. The disease in Belterra presented as a distinct clinical syndrome characterized by fever, arthralgia and exanthema. No fatalities could be attributed to MAY virus infection. Arthralgia, accompanied by joint edema in 20% of cases, was a very prominent sign which caused temporary incapacity in many patients. Arthralgia was present in virtually all confirmed cases and persisted in some for at least 2 months, although with decreasing severity. Rash was present in two-thirds of the cases, and was either maculopapular or micropapular. The incidence of rash was higher in children than in adults. Contrary to arthralgia, which started with the onset of clinical illness, rash usually appeared on the 5th day and faded within 3-4 days. Fever, chills, headache, myalgia, lymph-adenopathy and other minor clinical manifestations were also recorded, and generally persisted for from 2-5 days. Leucopenia was a constant finding in all cases. Mild albuminuria was seen in four of 25 patients, and slight thrombocytopenia was seen in 10 of 20 cases. The fact that viremia levels higher tha 5.0 log10/1.0 ml of blood were recorded in 10 patients rises the possibility that man may have be an amplifying host in the MAY virus cycle. The MAY virus illness, as seen in Belterra, has clinical features similar to those observed in persons infected with chikungunya virus.

Alphavirus↗
PubMed1981

An outbreak of Mayaro virus disease in Belterra, Brazil. II. Epidemiology.

Epidemiological investigations of an outbreak of Mayaro (MAY) virus which occurred inthe rural village of Belterra, Pará, Brazil are reported. Human cases were first recorded in December 1977 and continued through June 1978. Approximately 20% of the more than 4,000 persons resident in Belterra were infected, and a very high proportion of those infected suffered overt clinical illness. Cases were identified in all areas of Belterra and among all age groups; however, the greatest number of cases was seen among those who resided in close proximity to the forests. Yellow fever (YF) virus was also active in Belterra concurrently with the MAY virus outbreak. Six human cases of YF were identified, of which five were fatal. The YF outbreak ended following YF vaccination of the human population.

Alphavirus↗
PubMed1981

An outbreak of Mayaro virus disease in Belterra, Brazil. III. Entomological and ecological studies.

Results in entomological and vertebrate host investigations made during dual outbreaks of Mayaro (MAY) and yellow fever (YF) viruses in Belterra, Pará, Brazil in 1978 are reported. Over 9,000 insects representing 26 species were assayed in 396 pools for the presence of arboviruses. Pools of Haemagogus janthinomys Dyar yielded the only isolates of either MAY or YF virus. The minimum field infection rate for nine isolates of MAY virus from Hg. janthinomys was 1:82, and for two isolates of YF virus was 1:368. Analysis of collection data showed Hg. janthinomys to be attracted to man as a blood source and present in all habitats sampled, although most abundant in the forest canopy. Twelve hundred bird sera and 584 mammal sera were tested by hemagglutination-inhibition (HI) tests for antibody to MAY virus. Highest MAY antibody prevalence rates were found among marmosets (Calithrix argentata, 32 positive of 119 tested, 27%). Mayaro virus was also isolated from the blood of a sylvan marmoset captured at the peak of the MAY virus outbreak. Experimental infection of marmosets with MAY virus confirmed that a substantial viremia follows infection with this virus. Marmosets were also found with HI antibody to YF virus (5/119, 4%). The results presented indicate that Hg. janthinomys was the principal vector of both MAY and YF viruses and that marmosets were the main amplifying hosts for MAY virus, and perhaps for YF virus as well.

Alphavirus↗
PubMed1978

Natural transmission of Keystone virus to sentinel rabbits on the Delmarva Peninsula.

Domestic rabbits were exposed in the Pocomoke Cypress Swamp from early May through October 1973, to act as sentinel indicators of Keystone (KEY) virus transmission on the Delaware-Maryland-Virginia (DelMarVa) Peninsula. Rabbits were bled weekly and their sera were tested for the presence of neutralizing antibody to both KEY and James-town Canyon (JC) viruses. Adult mosquito activity was monitored concurrently by CDC miniature light traps with Dry Ice. Of 100 rabbits exposed, 20 rabbits acquired neutralizing antibody to KEY virus as a result of their exposure; none acquired antibody to JC virus. Eighty-three percent of susceptible rabbits exposed converted immediately after the emergence of Aedes atlanticus adult mosquitoes in early September. Rabbit seroconversions were not limited to any particular habitat within the swamp. The conversion of a large proportion of sentinel rabbits immediately following emergence of A. atlanticus, and the previous demonstration of transovarial transmission of KEY virus by A. atlanticus, suggest that vertically infected individuals are capable of viral transmission at their initial engorgement. Such transmission provides the initial step in a vertebrate amplification cycle.

Aedes↗
PubMed1978

Towards a quantitative understanding of the epidemiology of Keystone virus in the eastern United States.

The implications of the Keystone virus--Aedes atlanticus transmission cycle are explored in the context of a quantitative model. Among the variables considered are the vertical transmission rate, the effect of the virus upon vector fertility and survival, vector densities and distributions, the proportion susceptible in the vertebrate population, the attractiveness of different vertebrates to the vector and vector survival rates. The logical relationships between these several variables are explored. It is concluded that the current view of Keystone virus maintenance is quantitatively feasible, and that certain predictions may be made as to the magnitude of several parameters which have not yet been measured. Such predictions allow direct testing of the model. The general structure of the model is such that it may prove useful in describing the epidemiology of other vector-borne infections in which vertical transmission is essential for infection maintenance at certain periods of the year.

Aedes↗
PubMed1975

Ecology of Keystone virus, a transovarially maintained arbovirus.

Our studies in the Pocomoke Cypress Swamp of Maryland have shown that KEY strain of CE is endemic and is carried by the floodwater mosquito A. atlanticus. The virus is transmitted transstadially in nature, as evidenced by our recovery of virus from larvae and males of this species. Serologic evidence, both here and elsewhere, indicates that vertebrates are infected with KEY, but their role in the transmission cycle remains unknown. We have found several animals, for example, the gray squirrel, that are potential vertebrate reservoirs for the virus. Gray squirrels possess antibodies to KEY in nature, are known to be fed upon by A. atlanticus females, and have been shown to circulate a high-titered viremia after experimental inoculation. Evidence from 1974 collections, however, indicates that A. atlanticus females ingested only a single blood meal during the period when adults were active. We will not be able to assess the relative importance of the vertebrate and mosquito cycles until much more work has been performed on vector-reservoir-virus dynamics.

Aedes↗
PubMedDate not supplied

Laboratory rat associated outbreak of haemorrhagic fever with renal syndrome due to Hantaan-like virus in Belgium.

Hantaan-like virus was identified as the cause of three cases of acute renal failure in staff handling laboratory rats on a Belgian university campus. Serological studies revealed infected rat strains at different sites on the campus and evidence of past and recent infections in 39 staff members and of infection in 50% of exposed staff. Hantaan-reactive antibody was very rare in control populations. Staff or rats at three other Belgian institutions had no signs of infection. The origin of the virus was not identified. Infected rats have been removed. These are the first confirmed cases, outside East Asia, of human illness due to rat-borne Hantaan-like virus, and of infection in laboratory rats. Surveillance of rat colonies is also recommended in countries which, like Belgium, have no previously recognised cases of haemorrhagic fever with renal syndrome.

Acute Kidney Injury↗
PubMedDate not supplied

Epidemiology of hemorrhagic fever viruses.

Twelve distinct viruses associated with hemorrhagic fever in humans are classified among four families: Arenaviridae, which includes Lassa, Junin, and Machupo viruses; Bunyaviridae, which includes Rift Valley fever, Crimean-Congo hemorrhagic fever, and Hantaan viruses; Filoviridae, which includes Marburg and Ebola viruses; and Flaviviridae, which includes yellow fever, dengue, Kyasanur Forest disease, and Omsk viruses. Most hemorrhagic fever viruses are zoonoses, with the possible exception of the four dengue viruses, which may continually circulate among humans. Hemorrhagic fever viruses are found in both temperate and tropical habitats and generally infect both sexes and all ages, although the age and sex of those infected are frequently influenced by the possibility of occupational exposure. Transmission to humans is frequently by bite of an infected tick or mosquito or via aerosol from infected rodent hosts. Aerosol and nosocomial transmission are especially important with Lassa, Junin, Machupo, Crimean-Congo hemorrhagic fever, Marburg, and Ebola viruses. Seasonality of hemorrhagic fever among humans is influenced for the most part by the dynamics of infected arthropod or vertebrate hosts. Mammals, especially rodents, appear to be important natural hosts for many hemorrhagic fever viruses. The transmission cycle for each hemorrhagic fever virus is distinct and is dependent upon the characteristics of the primary vector species and the possibility for its contact with humans.

Animals↗