Browsing by Author "Plowright, W."

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Allerton-type Herpes Virus as a Cause of Lesions of the 'Alimentary Tract in a Severe Disease of Tanzanian Buffaloes (Syncerus caffer
(1971) Plowright, W.; Dr. Schiemann, B .
A severe outbreak of disease occurred in buffaloes in a part of the Serengeti National Park, Tanzania,in December, 1969, at the end of a prolonged and severe drought. There was a high mortality, particularly affecting animals up to about one year of age, and accompanied by heavy infestations with external and internal parasites. The clinical and post-mortem findings were described, the latter including erosions and ulcers of the mucosae of the upper alimentary tract. One animal had lesions of the tongue which were histologically typical of Allerton-type herpes virus infection. This agent was isolated from a tongue lesion and prescapular lymph node tissue, while neutral using antibody against it was found in 11 of the 13 buffalo sera damined.It was not considered that the Allerton-type virus was a primary cause of the morbidity or mortality, since serological evidence indicated that the infection was universal in East African buffalo populations, without evidence of overt pathogenicity elsewhere.
The Application of Monolayer Tissue Culture Techniques in Rinderpest Research
(1962) Plowright, W.
The second technique (II), described by Plowright and Ferris, was used to passage rinderpest virus of the Kabete « 0 » strain and ill the production of high-titre virus stocks. Experiments designed to ascertain some of the factors governing virus yield in culture and losses in freeze drying will be described elsewhere. Titrations were carried out in primary calf-kidney cultures using a technique similar to that described in the above reference. However, minor modifications were introduced during the last 2 years or so, so that each culture tube received 0.2m.l of virus inoculum instead of 0.1 ml and negative tubes were not discarded until after 11 or 12 days of observation, compared with the original 8 days. Normally 5 tubes were used per dilution but the number was increased to 10 when simultaneous titrations were performed in cattle and tissue cultures.
Cytopathogenic agents associated with lumpy skin disease of cattle
(1957) Alexander, R. A.; Plowright, W.; Haig, D. A.
Van den Ende, et at. (1948), reported the isolation in chick embryos of a filtrable virus from a calf naturally infected with lumpy-skin disease in the Western Cape Province of South Africa. Subsequent work has shown that this virus probably has no direct etiological relationship with the disease. In spite of numerous attempts neither the same nor any similar type of virus has since been isolated from lumpy-skin material in fertile hen's eggs.
The Epizootiology of African swine fever in Africa
(1969) Plowright, W.; Parker, J.; Pierce, M.A.; East African Veterinary Research Organisation, Muguga, Kabete, Kenya
The incidence of African swine fever virus in different body tissues in two populations of East African warthogs and the distribution of the virus in the tick population of Kenya, Tanzania and Uganda were studied. There was no evidence of transplacental infection or of excretion of the virus in the milk. In view of experimental evidence, infection by ingestion was improbable. Infected ticks were found in 40% of burrows in Kenya and Tanzania, but in none in Uganda. The highest rate of infection was in adult ticks, while no first-stage nymphs were infected. The virus recovered from ticks appeared to be similar to the typical field strain. Virus proliferation occurred in the ticks. Persistent infection with some strains of virus was acquired by laboratory ticks when fed on reacting pigs or infected blood in capillary tubes. The disease was transmitted by feeding for 18-34 weeks after the original infective feed. Trans-stadial transmission occurred regularly with the Uganda strain of virus but infrequently with the Tengani strain. Virus was excreted from the tick in the coxal fluid and probably also in the saliva. Relatively small doses of virus by the nasal and parenteral routes infected pigs regularly, while large doses by mouth failed to do so. Natural transfer of virus from wild to domestic pigs might take place when infected ticks are carried into piggeries. Although a large DNA virus, the African swine fever virus satisfied all the basic requirements for an arbovirus. -BMW.
Growth and Characterization of the Virus of Bovine Malignant Catarrhal Fever in East Africa
(1964) Macadam, R.F.; Armstrong, J.A.; Plowright, W.
A strain of bovine malignant catarrhal fever virus (MCF) recovered from the blood of a blue wildebeest was developed by passage in vitro to a stage where it could be propagated serially in primary thyroid cell cultures by inoculation of cell-free fluids. Released virus titers ranged from 103 .8 to 105 .8 50% tissue culture infectious doses/ml. This virus still caused fatal disease when inoculated to cattle, and was neutralized by antibody that appeared in the sera of cattle recovering from experimental infection. The principal cytopathic effects of the virus were the development of DNA containing intranuclear inclusions and syncytia; the inclusions became increasingly basophilic as they matured. The cytopathic effects were inhibited in the presence of 5-iodo-2' -deoxyuridine (IUDR), and infectivity of the virus was abolished by treatment with ether or chloroform. Electron microscopy of inoculated cell cultures showed intra nuclear, cytoplasmic and extracellular herpes-like virus particles. Suspensions of cell-free virus examined by negative-stain electron microscopy contained some particles of diameter 140 m,u-220 m,u, comprising an outer envelope and a central body or capsid; others consisted of only a naked capsid about 100 m,u in diameter. MCF virus is evidently a member of the herpes group, and has particular affinities to a subgroup which contains the agents of varicella, herpes zoster and the cytomegaloviru
The Growth of a Virulent Strain of African Swine Fever Virus in Domestic Pigs
(1968) Plowright, W.; Parker, J.; Staple, R.F.; Animal Virus Research Institute, Pirbright, Surrey, England
Pigs were infected by the intranasal instillation of a large dose (ca. 107·0 ID 50) of a highly virulent strain of African swine fever virus (ASFV) and the progress of the infection was studied by the ‘routine titration approach’ (Mims, 1964) using pig bone marrow cultures. Virus growth was established within 16–24 hr. in the retropharyngeal but not in the alimentary or nasal mucosae or the tonsils. By 24–40 hr. the virus was consistently present in the retropharyngeal lymph nodes, almost invariably the medials; titres in these nodes exceeded those in the associated mucosa by 48–72 hr. Generalization, presumed to have occurred via the tracheal lymph ducts and the blood stream, was generally demonstrable after 72 hr., i.e. by the time of the onset of pyrexia or 24 hr. prior to this. On average 11% of the total infectivity in the blood was present in the plasma, with the rest assumed to be cell-associated. A mean of about 45% of the total infectivity was recovered in erythrocyte fractions in which the concentration of leucocytes had been materially reduced; fractions with increased leucocyte counts contained relatively little virus and it was concluded that the great majority of circulating virus was closely associated with the erythrocytes. Adsorption of ASFV to normal pig erythrocytes was demonstrated in vitro. The greatest concentrations of virus were recorded in the lymph nodes, especially those of the cephalic region, and in the spleen, where titres commonly attained 108·0 to 109·0 HAD 50/g. and exceeded those in the blood. They were, therefore, thought to be the source of much circulating virus, although there was some evidence that the liver, lungs and bone marrow may also have contributed, at least in some animals. There was no evidence that the mucosae of the alimentary and respiratory tracts or the kidney, myocardium and brain were a source of significant amounts of virus. The virus demonstrable in Peyer's patches did not exceed that in the intervening ileal mucosa. Although contact transmission of ASF does not normally occur during the first 12–24 hr. of fever, considerable amounts of virus were usually present in the nasal and intestinal mucosae at 72 hr. It was probable that this infectivity was due to the blood content and that excretion did not occur until the epithelium was breached. Three pigs, all of which had lesions of a portal cirrhosis, showed a delayed or restricted generalization of virus, in comparison with the other twenty-eight animals which behaved according to a regular pattern.
The Growth of a Virulent Strain of African Swine Fever Virus in Domestic Pigs
(1968) Plowright, W.; Parker, J.; Staple, R.F.; Animal Virus Research Institute, Pirbright, Surrey, England
Pigs were infected by the intranasal instillation of a large dose (ca. 1070 ID 50) of a highly virulent strain of African swine fever virus (ASFV) and the progress of the infection was studied by the 'routine titration approach' (Mims, 1964) using pig bone marrow cultures.
The Growth of Virulent aml Attenuate(l Strains of Rinderpest Virus in Primary Calf Kidney Cells
(1963) Plowright, W.
Large tube cultures of calf kidney cell monolayers were inoculated with RGK/1, a recent isolate of moderately high cattle pathogenicity, a virulent RBOK strain, or the RBOK strain after 90 culture passages when it was non-pathogenic. When the tubes were harvested, the fluid was centrifuged and the resultant supernatant regarded as released virus (RV), while the cells were detached from the glass by 0.02% versene. This cell-containing versene soln. was centrifuged, the supernatant being titrated for virus removed by the versene; the deposited cells were subjected to ultrasonic disruption to obtain cell-associated virus (CAV). The CAV/RV ratio was investigated daily for each strain. The attenuated RBOK strain was more easily detached from cells by versene than was either of the virulent strains. RBOK and RGK/1. The CAV in versene detached cells was further reduced by l5 min. treatment with 0.01% trypsin; the reduction was 84-97% for RGK/1, 60-90% for attenuated RBOK. Very little (0.1-2.4%) of RGK/1 infectivity was recovered in the enzyme soln., whereas the recovery rate for attenuated RBOK was over 50%. Both strains were equally highly sensitive to 0.05% trypsin, it was concluded that rinderpest virus is usually completed and accumulated at the cell surface, and that the infective particles there can be subdivided into fractions showing a different sensitivity to removal by various agents. -A.W.J.
Immunisation of cattle against the herpesvirus of malignant catarrhal fever: failure of inactivated culture vaccines with adjuvant
(1975) Kalunda, M.; Plowright, W.; Rampton, C.S.; Herniman, K.A.J.; Jessett, D.M.
Attempts were made to immunise cattle against the herpesvirus of malignant catarrhal fever by inoculating living or formalinised preparations of the agent, propagated in cell cultures and combined with Freund's incomplete adjuvant.
Inter-Relationships Between Virus Infections of Game and Domestic animals
(1968) Plowright, W.
Before proceeding with my contribution, I should like to point out that I am hardly concerned at all with how meat from game animals could be utilized for human food. Neither am I greatly concerned with the zoonoses, a word much beloved by those who would magnify the importance of animal diseases which they study by stressing them communicability, potential or actual, to man.
Inter-Relationships Between Virus Infections Of game And Domestic Animals
(1968) Plowright, W.
Before proceeding with my contribution I should like to point out that I am hardly concerned at all with how meat from game animals could be utilized for human food. Neither am I greatly concerned with the zoo noses. a word much beloved by those who would magnify the importance of animal diseases which they study by stressing their communicability. Potential or actual. to man. In fact. this paper is wrongly placed and I would regard our own work primarily as contributing factual information to the problem of resolving conflicts between wildlife and domestic animals. in the grazing areas of East Africa. What I have to say would have been more appropriate in section 4 of these proceedings.
Investigations of Allerton-type Herpes Virus Infection in East African Game Animals and Cattle
(1971) Plowright, W.; Jessett, D.M.; East African Veterinary Research Organization, Muguga, P.O. Kabete, Kenya
Neutralization tests with a strain (BA) of Allerton-type herpes virus, derived from a buffalo (Syncenis caffer) were carried out on 924 sera from 17 species of E. African game animals and on cattle sera from Tanzania (2001), Kenya (792) and Uganda (410). Buffalo populations throughout E. Africa showed a very high rate of infection, with all animals over 2 years of age serologically positive. Antibody was present in some giraffe, waterbuck and hippopotamus sera and, less frequently, in impala, eland, bushbuck and oryx. Data are provided on the titres of positive samples; the mean titre of buffalo sera increased with age. Cattle in many localities of N. Tanzania and S. Kenya showed a very high rate of infection, 85–95% of sera from animals more than 2-years old containing antibody; the titres recorded were lower than those in buffaloes. Very high infection rates were also found in Karamoja and Teso (Uganda) and also in some other areas of Kenya, whilst a considerably lower incidence of infection was detected in W. Nile Province of Uganda and in central Tanzania. Differences in infection rates may have been related to herd size and husbandry practices. It was shown that a wave of infection was probably spreading through cattle in N. Tanzania at about the same time as an outbreak of disease occurred in buffaloes and it is suggested that virus transmission may have been by biting flies. No clinical signs attributable to the virus were reported in cattle but mouth lesions similar to those recorded in buffaloes, or nasal lesions, could have passed undetected. Allerton-type virus probably produces a range of clinical syndromes in cattle, closely resembling those associated with some herpes viruses in primates but infection is seldom related in the field to either pseudo-lumpy skin disease, mammillitis or stomatitis.
Investigations on the Incidence of Rinderpest Virus Infection in Game Animals of N. Tanganyika and S. Kenya 1960/63
(1967) Plowright, W.; McCulloch, B.; East African Veterinary Research Organization, P.O. Box 32, Kikuyu, Kenya. Veterinary Investigation Centre, Arusha, Tanganyika Territory
The incidence of rinderpest infection in game animals in selected localities of South Kenya and North Tanganyika was studied during the period 1960 to 1963. Serum samples from 590 wildebeest (Connochaetes taurinus), 48 eland (Taurotragus oryx), 65 Thompson's gazelle (Gazella thompsoni) and 39 Grant's gazelle (Gazella granti) were tested for rinderpest neutralizing antibody. Rinderpest infection was shown to have been very frequent in yearling wildebeest in the Mara area of Kenya in 1959/60, in the Serengeti National Park of Tanganyika in late 1960 and also in the Serengeti, and some adjacent areas, during the latter half of 1961. In the Ngorongoro Crater in 1961 infection was far less widespread, with only 11% of the yearling’s acquiring antibody, compared to 67% in the Serengeti. The infections in 1959 and 1960 were clinical epizootics, accompanied by a considerable mortality, whereas no overt disease was reported in the course of 1961. Eland were affected in a similar manner to wildebeest up to 1960 but only a low rate of serological conversion was demonstrated in 1961. Adult Thompson's gazelle showed a low rate (ca. 12%) of infection but no anti-body was detected in Grant's gazelle. Only a small proportion of the wildebeest calves born in early 1962 acquired antibody by mid-1963 and this was due, at least in part, to infection late in 1962; it was not clear, unfortunately, whether the positive animals belonged entirely to resident, as opposed to migratory, groups. No clinical signs or mortality were reported in this year. A low incidence of rinderpest infection in wildebeest was also demonstrated both before and after 1960 in the Kajiado district of Kenya, where disease of game has not been reported in recent years. It is possible that the positive animals, as also the 1962 cases in Tanganyika, acquired the virus from low-grade infections of cattle. The transmission of rinderpest antibody from wildebeest dam to calf, presumably via the colostrum, was demonstrated regularly, except in six calves about 1–2 weeks old. No completely satisfactory explanation was obtained for their failure to acquire passive antibody but it may have been due to abnormal disturbance in the herds, associated with the shooting. The antibody titres in calves were initially higher than those in the serum of their dams but by the end of the 3rd month this position had been reversed. Individual calves became serologically negative from about the 10th week of life and all were devoid of antibody by the 6th to 7th month. The half-life of passively-acquired antibody was 4·4 weeks.
The Isolation from an Eland of a Strain of Rinderpest Virus Attenuated for Cattle
(1959) Robson, J.; Arnold, R.M.; Plowright, W.; Scott, G.R.
An attenuated field strain of rinderpest virus isolated from an eland (Taurotragus oryx) was stable on serial passage in cattle. It infected zebu and grade cattle, hairy sheep and goats but not pigs, mice, g.pigs and rabbits. The disease in cattle was non-lethal, with mild but prolonged fever, mouth lesions and infrequent, transient diarrhoea. It spread readily, however, by contact amongst susceptible cattle. The strain therefore resembled the attenuated field strain isolated 10 years before in Tanganyika from infected crossbred Ankole-zebu cattle.
Long-term Studies of the Immunity in East African Cattle Following Inoculation with Rinderpest Culture Vaccine
(1976) Plowright, W.; Taylor, W.P.; East African Veterinary Research Organization, Muguga, P.O. Box 32, Kikuyu, Kenya
Virus-neutralizing antibody was investigated over periods of 24 to 50months in East African cattle which had been inoculated with culture attelluated rinderpest virus of 9I or more passages in calf kidney mono layers. The cattle were of 3 types, viz: Friesiall or Jersey grades, Borall (shorthorn zebu) and Allkole (longhorn).
Malignant Catarrhal Fever In East Africa
(1965) Plowright, W.; East African Veterinary Research Organization
The virus of malignant catarrhal fever (M.G.P. or 'snotsiekte') was sought in the tissues of blue wildebeest (Gorgon taurinus taurinus) which were killed or captured in 2 ecologically distinct areas of Kenya and Tanganyika. Two isolation techniques were employed:
Malignant Catarrhal Fever in East Africa: III. Neutralizing Antibody in Free-Living Wildebeest
(1967) Plowright, W.; East African Veterinary Research Organization, Muguga, P.O. Box 32, Kikuyu, Kenya
Serum samples from 181 East African wildebeest were inactivated at 56°C. for 30 min. and examined for neutralizing activity against the virus of malignant catarrhal fever (MCF or snotsiekte). All animals over the age of 7 months were serologically positive and the mean SN50 titre for those aged 3 years or more was 10-1·70. Half of 12 calves in the birth to 4 weeks age group possessed high-titre antibody, presumably acquired from the colostrum of their dam. The other 6 had no antibody, although their mother’s serum contained the usual quantities; the normal transmission of rinderpest antibodies, from dam to offspring, also did not occur in these instances. No explanation was found for the failure, which was probably limited to animals in this age group. The mean antibody titre fell continuously during the second to fourth months of life, but then increased steadily from a minimum of 10-1·19 to a peak of 10-2·29, in animals 13 to 18 months old. In the great majority of calves there was no period when passively-acquired antibody had reached very low levels and active “immunization” had yet to take place. Viraemia was detected in 12 of 43 animals aged from one to 20 weeks and 11 of them had circulating antibody at the time of sampling; yearlings and adults which were viraemic also had antibody in their serum. It was concluded that colostral antibody did not interfere significantly with active infection and the establishment of a permanent “immune” state. Although some wildebeest are probably infected congenitally with MCF virus, immunological tolerance does not develop to this agent.
A Microtitre Technique for the Assay of Malignant Catarrhal Fever Virus and Neutralising Antibody
(1979) Mushi, E.Z.; Plowright, W.; Royal Veterinary College, London
A microtitre technique for the quantal assay of a cell-free strain of malignant catarrhal fever virus was developed, using serially passaged bovine embryonic kidney cells. End-points were determined after 12 days’ incubation and the mean titre recorded for a single virus stock stored at −70°C over a six-month period was 105·5±0·2 (SD). In neutralisation tests serum/virus mixtures were best held at 37°C for 1 h in microtitre trays before the addition of cells; assays were highly reproducible, figures of 101·5±0·2 being obtained for a single reference serum.
Other Sensitivity of Some Mammalian Pox Viruses
(1959) Plowright, W.; Ferns, R. D.
Resistance to inactivation by ethyl ether is commonly regarded as a characteristic of the majority of mammalian and avian poxvirus (1, 2), exceptions being provided by myxoma (1,2) and fibroma U, 2) of the rabbit. We have recently investigated the ether sensitivity of four agents which in all probability belong to this group. These included a strain of sheep pox (SP) adapted to growth in sheep testis monolayers (4), a strain (Neethling) of virus belongings to group.
The Serial Cultivation of Calf Kidney Cells for Use In Virus Research
(1961) Ferris, R.D.; Plowright, W.; East African Veterinary Research Organization
Attempts to establish lines of cells from calf kidney mono layers are described in detail. Six of 9 culture series were maintained for periods of 11 to 24 weeks, involving 10 to 22 transfers; growth then failed rapidly and completely. Two further lines were passaged 50 and 66 times drying 21 and I7 months respectively; their growth remained satisfactory up to the 37th mid 41st in vitro generations, but thereafter was not sufficiently regular or vigorons to allow their satisfactory use ill virus investigations. No "transformed" or "altered" cell-type appeared in any of these cultures. The last line (BK/I65) was shown to be capable of sustained, rapid multiplication over more than 70 subcultures in a period of 18 months. This, also, was not a "transformed" type of cell. It was preserved ill glycerine-containing media at -700 C. for at least 10 months, with good retention of viability. All serially-cultivated calf kidney cells were highly susceptible to rinderpest virus passaged in primary calf kidney monolayers. Following a few serial passages in the "cell lines" good virus yields were not often obtained, but this eventually proved to be consistently possible with the line BK/I65. The latter was also found to be valuable for serial propagation of the virus of malignant catarrhal fever and susceptible to a bovine para-influenza virus.

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