A simple model is used to explore the extent to which the uniquely comprehensive studies of western equine encephalomyelitis in Kern County, California, by Reeves and his colleagues over many years, explain the dynamics and epidemiology of the infection. It is concluded that not only does this series of integrated field and laboratory studies successfully account for these phenomena, to an extent which is unlikely to be substantially improved upon, not least because of the inherent difficulties in measuring the key factors with greater precision; but it also provides a unique model of the dedication and ingenuity required if comparable levels of understanding of the ecology and epidemiology of other arbovirus infections are to be achieved.

Journal Article The London School of Hygiene and Tropical Medicine Get access C. E. Gordon Smith C. E. Gordon Smith London School of Hygiene and Tropical Medicine, London WC1E 7HT U.K. Search for other works by this author on: Oxford Academic PubMed Google Scholar Transactions of The Royal Society of Tropical Medicine and Hygiene, Volume 75, Issue Supplement_1, 1981, Pages 12–20, https://doi.org/10.1016/0035-9203(81)90456-9 Published: 01 January 1981

Developing countries are going to have to formulate their own development policies and establish their own core of national expertise on which they can draw. It is more appropriate that the policies spring from the needs and conditions of the country itself than from the direction of any donor country or agency. Self-reliance rather than self-sufficiency is what is being emphasized. Many of these developing countries are going to need international aid for their development programs for years to come. The programs derived from the needs of the country will have a greater chance to succeed, since they will be drawn in conjuncton with local customs, historical traditions, and ecological conditions. The national experts can be assembled in a scientific council, functioning across departmental lines. Each country will have to formulate policies which will enhance their experts' sense of job satisfaction and guard against the phenomenon of "brain drain."

The possible role of pigs as arbovirus maintenance hosts and their importance as amplifier hosts was studied. Blood samples from 464 pigs of all ages collected in 1962 and 1964 were tested against 10 arboviruses. Antibodies to Japanese encephalitis and Getah viruses were particularly prevalent and their calculated monthly infection rates were 19·5% and 13·3% respectively. In 1969, 447 pigs were bled monthly throughout the year and the infection rates for Japanese encephalitis virus were calculated in pigs during the first year of life. Infection rates were not uniform throughout the year; the rate increased as the pig grew older and there was a marked seasonal increase in the infection rate in the period from November to January. This coincided with the seasonal major population peak of Culex tritaeniorhynchus following intense breeding of this mosquito prior to rice planting. It is suggested that, in Sarawak, the pig acts as a maintenance host of Japanese encephalitis in a cycle involving C. gelidus mosquitoes and also acts as an important amplifier host towards the end of the year in a cycle involving C. tritaeniorhynchus. It is further suggested that Getah virus is maintained in a similar cycle between C. tritaeniorhynchus and pigs.

1.1.2,118 human sera collected from all age groups in a wide variety of ecological zones in Sarawak during December 1962 and January 1963, April-May 1964 and September-December 1966, were tested for haemagglutination-inhibiting and neutralizing antibodies to 9 arboviruses.2.2.Japanese encephalitis and dengue virus antibodies were prevalent in all areas. The estimated annual infection rate with Japanese encephalitis virus varied from about 2% to over 9% with a mean of 6%. Estimated dengue virus infection rates varied from less than 1 % to over 11% with a mean of just over 5% per annum.3.3.There was only slight evidence of infection with group A, Bunyamwera and other group B arboviruses.4.4.No significant differences in the prevalence of arbovirus infections could be distinguished between any of the ecological zones. The wide distribution of Japanese encephalitis and dengue virus infections matched the distribution of the principal arthropod hosts of the viruses, C. tritaeniorhynchus, C. gelidus and Ae. albopictus.5.5.The general trend of arbovirus infections in Sarawak was of highest infection rates in coastal, estuarine and inland forest areas. Urban areas had the lowest rates while rural areas of settled cultivation had intermediate rates of infection.

(1970). Arbovirus infections in Sarawak: The isolation of Kunjin virus from mosquitoes of the Culex pseudovishnui group. Annals of Tropical Medicine & Parasitology: Vol. 64, No. 3, pp. 263-268.

In the treatment of cancer, injection with viruses may have a beneficial effect. Possible mechanisms of action include direct cytolysis by virus multiplication, immunological cytolysis by both cell-mediated and humoral responses to " budding " viruses which incorporate cell membrane into their coat and confer virus antigen determinants on the surface of infected cells, and interference and the production of interferon by viruses.

55 viruses were isolated from approximately 174,300 mosquitoes collected in 2 areas of Sarawak between November 1968 and December 1969: 36 isolates, of which 4 have been provisionally identified as strains of Japanese encephalitis virus, came from C. tritaeniorhynchus and 7 isolates, of which 1 is a strain of Japanese encephalitis, from C. gelidus.

Cyclophosphamide altered not only the pathological picture of virus encephalitis, but also enhanced the invasiveness of viruses and produced fatal forms of disease to which monkeys were otherwise resistant. Normal patas monkeys infected either i.c. or intranasally (i.n.) with louping ill developed clinical encephalitis from which they recovered, but when cyclophosphamide was administered the disease proved fatal. Normal rhesus monkeys inoculated i.n. with virulent western equine encephalitis virus developed neither clinical disease nor CNS lesions, but after treatment with cyclophosphamide they developed fatal encephalitis. The viruses of louping ill, Venezuelan equine encephalitis and Western equine encephalitis when given without an immunosuppressant usually gave rise to acute inflammatory CNS pathology, but when the monkeys were given cyclophosphamide, the inflammatory reaction was replaced by a degenerative process causing both neuronal necrosis and spongy degeneration.

Summary1. When mice are infected intraperitoneally with Langat virus only a small proportion develop clinical encephalitis, but all mice have substantial titres of virus in the brain and also incontrovertible histological evidence of encephalitis.2. When specific antibody is given intraperitoneally or intravenously to mice during the first 3 days after intraperitoneal infection with Langat virus, the viraemia (normally maximal during this period) is depressed, the production of antibody is depressed or delayed, and the incidence of clinical encephalomyelitis is increased significantly.3. Specific antibody given intraperitoneally or intracerebrally before infection, protects the animals from encephalitis.4. These findings are discussed in terms of the histology of the central nervous system of the affected mice.We are very grateful to Miss S. J. Illavia, B.Sc., and to Miss G. E. Fairbairn for their skilled technical assistance; and to Mr S. Peto of the Microbiological Research Establishment for statistical advice.This work was made possible by a generous grant from the Wellcome Trust and the Endowment Funds of St Thomas's Hospital

Summary1. Irradiation in a whole body dose of 200 rads or more increased the sensitivity of mice to intraperitoneal infection with Langat virus so that the LD 50 was increased to about the intracerebral LD 50.2. In mice given 500 rads before infection: (a) viraemia was prolonged by about 5 days; (b) the IgM response was depressed; (c) the IgG response was delayed by about 3 days and depressed in titre; (d) virus concentration in the brain rose continuously until death on about the tenth day while in the controls it reached a peak on the fifth day then subsided; (e) histological changes in the CNS were delayed and minimal even at death; (f) irradiated mice died with little evidence of paralysis while the controls died with severe paralysis.3. In irradiated mice, protection was observed when antibody was administered on the third day following infection. Antibody given on the 3 days after infection to control mice aggravated the disease.4. The results in this and the preceding paper are discussed in relation to the pathogenesis of encephalitis. It is concluded that neuronal damage is caused both by virus multiplication in neurones and by damage superimposed by inflammatory changes with associated oedema and hypoxia. The inflammatory changes appear to be due to an allergic reaction to virus-antibody complexes formed in the circulation and in the central nervous system.We are grateful to Miss S. J. Illavia, B.Sc., and Miss G. E. Fairbairn for their skilled technical assistance; to the Department of Radiotherapy at St Thomas's Hospital for providing time and staff to help with the irradiation experiments; and to Mr S. Peto of the Microbiological Research Establishment for statistical advice.This work was made possible by a generous grant from the Wellcome Trust and the Endowment Funds of St Thomas's Hospital.

Sheep, after infection with louping ill virus and after re-infection with the same strain of virus 19–21 months later, were bled at intervals and their sera examined for neutralizing and haemagglutinin-inhibiting antibodies. Each antibody type was measured by the constant serum/variable virus and constant virus/variable serum methods. The persistence of each type of antibody and its significance in epidemiological studies is discussed. The relationship of antibody levels in ewes and their lambs was also examined.

DURING routine animal collections at Bukit Lanjan in the Sungai Buloh Forest Reserve about 7 miles west of Kuala Lumpur, ticks were collected off rodents. The reserve is small and is surrounded by young and old secondary growth in which much of the trapping was done by local aborigines. Two strains of virus were obtained, TP–94 and TP–123.

The director of the Microbiological Research Establishment at Porton describes some of the highlights of the work carried out during 1967.

Journal Article Arbovirus Infections in Sarawak: Further Observations on Mosquitoes Get access W.W. Macdonald, W.W. Macdonald Search for other works by this author on: Oxford Academic PubMed Google Scholar C.E.G. Smith, C.E.G. Smith Search for other works by this author on: Oxford Academic PubMed Google Scholar P.S. Dawson, P.S. Dawson Search for other works by this author on: Oxford Academic PubMed Google Scholar A. Ganapathipillai, A. Ganapathipillai Search for other works by this author on: Oxford Academic PubMed Google Scholar S. Mahadevan S. Mahadevan Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Medical Entomology, Volume 4, Issue 2, 1 May 1967, Pages 146–157, https://doi.org/10.1093/jmedent/4.2.146 Published: 01 May 1967