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Biomedical subjects

B K Johnson

Publications and source records attributed to B K Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1981

A seroepidemiological survey in the Gezira, Sudan, with special reference to arboviruses.

A serological survey in the Gezira area of the Sudan confirmed that malaria and schistosomiasis were highly endemic. Of other parasitic infections amoebiasis was common but Toxoplasma was less than found in a previous survey. Poliomyelitis and measles infection were universal and there was an extremely high incidence of infection with hepatitis B. Of arboviruses infection with flaviviruses was frequent and more than with alphaviruses.

Adolescent↗
PubMed1980

Arbovirus isolations from ixodid ticks infesting livestock, Kano Plain, Kenya.

In a study conducted on the Kano Plain, Kenya, virus isolation attempts were made on ixodid ticks collected, over a 14-month period, from livestock held in family enclosures (bomas) before releasing the animals for daily foraging. 8735 Amblyomma variegatum (Fabricius) were tested, 98.6% of which were taken from cattle, yielding 36 strains of Dugbe (DUG), four strains of Nairobi sheep disease (NSD), three strains of Bhanja (BHA), one strain of Thogoto (THO) and five strains of virus which could not be characterized. 6549 Rhipicephalus spp. ticks were collected (60.3% from cattle). NSD, DUG and BHA viruses were each isolated twice from ticks taken from cattle. One BHA virus strain was recovered from ticks from a sheep. One strain recovered from ticks on cattle could not be characterized.

Animals↗
PubMed1979

A comparative study of O'nyong nyong virus with Chikungunya virus and plaque variants.

Two plaque variants of Chikungunya (CHIK) virus were serologically compared with O'nyong nyong (ONN) virus in order to elucidate the reported one way antigenic relationships between the two viruses. Three different hypotheses are examined and evidence is shown to support one of them. Comparison of some biological properties of the viruses showed ONN to be distinct in some respects. All viruses and variants were found to replicate in Anopheles gambiae cells.

Arboviruses↗
PubMed1979

Cross-neutralization study of seven California group (Bunyaviridae) strains in homoiothermous (PS) and poikilothermous (XTC-2) vertebrate cells.

Antigenic relationships among seven California group strains were studied by a plaque-reduction neutralization test (PRNT). Cross-reactions occurred in most cases but three subgroups were noted: (1) the major serogroup contained the viruses of California encephalitis, LaCrosse, Snowshoe Hare and Trahyna (including the Lumbo strain) whereas (2) Jamestown Canyon and (3) Trivittatus viruses were distinct. There was no significant difference between the PRNT results in mammalian (PS) cells incubated at 37 degrees C and amphibian (XTC-2) cells incubated at 28 degrees C. Trivittatus virus failed to produce plaques in XTC-2 cells.

Animals↗
PubMed1979

Characterization of two Chikungunya virus variants.

The stability of virulence and plaque size of two variants of Chikungunya virus (genus Alphavirus) were examined. Mouse pathogenicity did not coincide with infective virus levels in the brain. An increase in the average survival times of mice receiving a lethal dose of the variant which allowed prolonged survival at high doses and harvested late after infection was observed. Studies in Vero cells suggested that the number of infective virus particles produced per cell was lower with the small plaque variant, though these cells were selective for this clone. On the other hand suckling mice or antisera favoured a more virulent large plaque variant.

Animals↗
PubMed1979

Investigation of the ecology of Soldado virus on Puffin Island, North Wales.

The prevalence of Soldado (SOL) virus and SOL virus antibodies was investigated on immature sea birds and the argasid tick Ornithodoros (Alectorobius) maritimus collected on Puffin Island, North Wales. No SOL virus was recovered from 133 bird sera, but 2 of the birds exhibited neutralizing antibodies against SOL virus. Nine of 27 tick pools (226 individuals) and 34 of 173 ticks tested individually proved to be infected with SOL virus.

Animals↗
PubMed1978

The isolation of a Bwamba virus variant from man in Western Kenya.

A bwamba group virus was isolated from the blood of a febrile child on the Kano Plain, Kenya. The isolate (NY-45), closely resembling Bwamba, established infection in both Anopheles gambiae and Mansonia uniformis. Neither the Bwamba nor the Pongola prototype strains grew in both species. In gel-diffusion tests NY-45 virus passaged through mosquitoes exhibited a line of identity with Pongola antiserum. In contrast no cross-reaction was observed with NY-45 virus which had not previously been passaged through mosquitoes.

Adult↗
PubMed1977

Arbovirus isolations from, and serological studies on, wild and domestic vertebrates from Kano Plain, Kenya.

Arbovirus infection and presence of haemagglutination-inhibiting antibodies in small mammals, birds and livestock were examined over a period of five years on the Kano Plain in western Kenya. Eleven isolations were made from mammals and birds. The viruses were identified as Arumowot and Germiston while three different agents could not be shown to be related to 188 African arboviruses. Prevalence of antibodies against arboviruses suspected of occurring in the area was generally low.

Animal Population Groups↗
PubMed1977

Arbovirus isolations from mosquitoes: Kano Plain, Kenya.

Arbovirus isolation attempts on 324,486 mosquitoes captured over a four-year period on the Kano Plain, Kenya, yielded 15 isolates including Pongola (six strains), Ilesha (three strains), Germiston (two strains), Sindbis (one strain), Barur (one strain) and two viruses which could not be characterized. Mansonia uniformis, Anopheles gambiae and Culex antennatus constituted 70% of the total collection and accounted for all of the isolates except one, which came from Anopheles funestus.

Animals↗
PubMed1976

Infection of an Aedes aegypti cell line with infectious arbovirus-antibody complexes.

Aedes aegypti cells exposed to infectious complexes of WN or YF virus and homologous antiserum produced lower yields of virus over a 10-day observation period than were produced by Aedes aegypti cells treated with a comparable dose of virus mixed with non-immune serum. When Ae. aegypti cells were infected with WN virus mixed with MVE, NTA, DEN-2 or YF antisera the virus yield over 10 days was lower than in cell cultures infected at similar titres with mixtures of WN virus with non-immune serum. If Ae. aegypti cell cultures were infected with mixtures of YF virus and WN or DEN-2 antiserum the resulting production of virus was lower over 10 days than in virus mixed with non-immune serum. Human serum samples from the field were tested for the presence of antibody by preincubation of the serum with WN virus prior to inoculation on to mosquito cell cultures. The results indicated that this method is as sensitive in detecting antibody as a mouse neutralization test using regression analysis of average survival time.

Aedes↗
PubMed1976

Antigenic relationships of alphaviruses by a simple micro-culture cross-neutralization method.

A cross-neutralization study of 22 alphaviruses disclosed two major antigenic complexes and two viruses that were distinct from all the others. Cross-reactions were common but were restricted within the complexes. Sub-groupings within a complex were also shown, and some viruses proved to be indistinguishable by neutralization testing. The results generally paralleled previously reported data. Investigations were carried out, using BHK 2I cells in a micro tissue-culture system, on all available alphaviruses.

Antigens, Viral↗
PubMed1975

Infection of the mosquito Aedes aegypti with infectious West Nile virus-antibody complexes.

Aedes aegypti fed through chick skin membranes on West Nile virus-homologous antiserum mixtures shown by an anti-globulin neutralization test to be highly infectious complexes (in terms of plaque formation in tissue culture) failed to become infected. Control mosquitoes fed on West Nile virus--normal rabbit serum mixtures containing similar or smaller amounts of infectious virus were shown to become infected. Mosquitoes ingesting suspensions of West Nile virus previously incubated with Murray Valley encephalitis or Ntaya antiserum became infected at significantly lower rates (P = less than 0-05) than controls ingesting West Nile virus-normal rabbit serum mixtures. West Nile virus--17D yellow fever or dengue--2 antiserum mixtures did not produce significantly reduced infection rates in Ae. aegypti when compared to controls.

Aedes↗