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Biomedical subjects

D M Watts

Publications and source records attributed to D M Watts.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effect of temperature on the vector efficiency of Aedes aegypti for dengue 2 virus.

The effect of temperature on the ability of Aedes aegypti to transmit dengue (DEN) 2 virus to rhesus monkeys was assessed as a possible explanation for the seasonal variation in the incidence of dengue hemorrhagic fever in Bangkok, Thailand. In two laboratory experiments, a Bangkok strain of Ae. aegypti was allowed to feed upon viremic monkeys infected with DEN-2 virus. Blood-engorged mosquitoes were separated into two groups and retained at constant temperatures. Virus infection and transmission rates were determined for Ae. aegypti at intervals ranging from 4 to 7 days during a 25-day incubation period. Results of the first experiment for mosquitoes infected with a low dose of DEN-2 virus and maintained at 20, 24, 26, and 30 degrees C, indicated that the infection rate ranged from 25% to 75% depending on the incubation period. However, DEN-2 virus was transmitted to monkeys only by Ae. aegypti retained at 30 degrees C for 25 days. In the second experiment, the infection rate for Ae. aegypti that ingested a higher viral dose, and incubated at 26, 30, 32, and 35 degrees C ranged from 67% to 95%. DEN-2 virus was transmitted to monkeys only by mosquitoes maintained at greater than or equal to 30 degrees C. The extrinsic incubation period was 12 days for mosquitoes at 30 degrees C, and was reduced to 7 days for mosquitoes incubated at 32 degrees C and 35 degrees C. These results imply that temperature-induced variations in the vector efficiency of Ae. aegypti may be a significant determinant in the annual cyclic pattern of dengue hemorrhagic fever epidemics in Bangkok.

Aedes↗
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

Changing patterns in mosquito-borne arboviruses.

Research leading to the current state of knowledge on the epidemiology of La Crosse virus (LACV), Jamestown Canyon virus (JCV) and dengue (DEN) viruses is summarized in relation to the generally recognized criteria for incriminating vectors. The importance of vector biology and local ecological conditions is emphasized as is the necessity of a good balance between laboratory and field-based studies. The influence of human activity in shaping the epidemiological patterns of all three of these arboviruses is readily apparent.

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↗
PubMed1982

Epizootic of viral enteritis in dogs in Thailand.

An epizootic of enteritis occurred in dogs in Thailand during 1979. Observations were made on 44 dogs that had clinical signs of enteritis or had a recent history compatible with a clinical diagnosis of enteritis. Eight of the 44 dogs died. Gross and histopathologic examinations performed on these dogs revealed that the lesions were similar to those described for canine viral enteritis. Antigens that agglutinated rhesus macaque RBC were detected in feces from 4 of 20 dogs. Cytopathic effects were observed in canine A-72 cells after their inoculation with fecal suspensions from these 4 dogs and with a fecal suspension from another dog. Cell cultures inoculated with each of the suspensions produced antigens that agglutinated RBC. All hemagglutinating antigens were inhibited in the presence of feline panleukopenia virus antiserum. Using electron microscopy, parvovirus-like virions were observed in a fecal suspension from 2 dogs (1 dog that had antigen that agglutinated rhesus macaque RBC and 1 dog that was negative for feline panleukopenia virus). Canine parvovirus hemagglutination inhibition antibody was detected in sera from 33 of the 40 dogs examined, and canine coronavirus (CV) neutralizing antibody was found in 29 of 30 dogs. Antibody titer increases indicative of recent canine panleukopenia virus (CPV)-like virus and CV infections were observed in paired sera for 2 of 35 and for 5 of 30 of the dogs in Thailand were infected with CPV-like virus and a CV, and these viruses were most likely the cause of the epizootic of viral enteritis.

Animals↗
PubMed1979

Experimental infection of vertebrates of the Pocomoke Cypress Swamp, Maryland with Keystone and Jamestown Canyon viruses.

Experimental studies were conducted to assess the susceptibility of white-tailed deer (Odocoileus virginianus), gray squirrels (Sciurus carolinensis), and cottontail rabbits (Sylvilagus floridanus) to Jamestown Canyon (JC) and/or Keystone (KEY) virus infection. Viremia occurred in 5 of 6 deer inoculated with JC virus; however, all deer developed KEY virus neutralizing antibody. Based on the observation that antibody elicited by primary infection of deer with either KEY or JC virus exhibited partial heterologous neutralization in vitro, cross-challenge experiments were performed in these animals. Keystone virus failed to infect deer 30 days post primary JC virus infection; however, deer became infected when challenged with KEY virus 80 days after the initial JC virus infection as indicated by a substantial increase in antibody titer. Similarly, JC virus failed to produce viremia in immune animals infected with KEY virus 80 days previously, although 2 of the 3 animals challenged had serological evidence of infection. Three field-collected cottontail rabbits with no evidence of KEY antibody were readily susceptible to KEY virus infection and developed viremias of 1-4 days' duration; rabbits with KEY virus antibody did not develop viremia upon KEY virus challenge. Eight antibody-negative field-collected gray squirrels became viremic following injection with KEY virus; however, a comparable group of squirrels did not become viremic when injected with JC virus.

Animals↗
PubMed1976

Experimental transmission of trivittatus virus (California virus group) by Aedes trivittatus.

The mosquito, Aedes trivittatus, when fed through a membrane a trivittatus virus dosage of 10(3.4) to 10(5.5) suckling mouse LD50/0.03 ml of blood, transmitted the virus to suckling mice. Virus multiplication indicative of a biological vector occurred in this species. When Aedes vexans and A. triseriatus ingested similar doses of trivittatus virus, both the infection and transmission rates were low and virus multiplication was poor. These results, added to evidence based on virus isolations from mosqito populations in nature, indicate that A. trivittatus is the primary vector of trivittatus virus in the north central United States.

Aedes↗
PubMed1975

Transovarial transmission of LaCrosse virus in Aedes triseriatus.

As part of a continuing investigation on the ecology of LaCrosse virus in Wisconsin, field and laboratory studies were conducted to explore the possibility that the virus is transmitted transovarially in A. triseriatus mosquitoes. In laboratory experiments, A. triseriatus mosquitoes were infected by ingesting LaCrosse virus in defibrinated blood. LaCrosse virus was recovered from F1 eggs, larvae, and adults that originated from the infected parent mosquitoes. In a subsequent field study aimed at determining if transovarial transmission accounted for the survival of LaCrosse virus during the winter season, larvae that originated from overwintering A. triseriatus eggs were collected from a LaCrosse virus enzootic area in southwestern Wisconsin. LaCrosse virus was isolated from these larvae and from adult A. triseriatus that were reared from field-collected larvae. These findings strongly imply that A. triseriatus is the reservoir of LaCrosse virus and that transovarial transmission is the mechanism responsible for the maintenance of the virus during the winter season in the north central region of the United States.

Aedes↗