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Biomedical subjects

J F Bell

Publications and source records attributed to J F Bell.

At least 19 recordsLinked to original sources
PubMed1986

Blood selenium concentrations of sheep and goats from selected areas of Kenya.

A systematic mapping technique based on blood, forage and soil selenium levels was employed to locate areas of selenium deficiency, adequacy or excess in areas of Kenya where grazing of small ruminants predominates. A total of 1,478 blood samples from both sheep and goats, 180 forage samples and 90 soil samples were analysed for selenium levels. During the wet seasons 28% of the sheep and 15% of the goats had marginal to deficient blood selenium concentrations while during the dry season 20% of the sheep and 12% of the goats had marginal to deficient blood selenium concentrations. Forage samples had a range of 0.03 to 0.66 ppm selenium while soil samples had a range of 0.06 to 0.98 ppm selenium. Although many animals had blood selenium levels of less than 0.05 ppm, below which selenium deficiency signs might occur, none of the animals manifested these signs.

Animals↗
PubMed1985

Tick survey on goats and sheep in Kenya.

A tick survey was done on sheep and goats in Siaya and Kakamega Districts, Kenya between October 1980 and October 1981. Most of the animals were found to carry one to 10 ticks with no significant difference between sheep and goats. The most abundant species was R. appendiculatus followed by R. evertsi. There were more male than female ticks found on the animals. Thirty per cent of the farms visited practised the hand picking method of tick control while 14% regularly dipped their animals.

Animals↗
PubMed1983

Immunofluorescent examination of the skin of rabies-infected animals as a means of early detection of rabies virus antigen.

Correlations were made on immunofluorescence positivity to antirabies conjugate between cranium-derived nerve fibers in skin and traditional samplings of brain tissue from several species and illness categories of animals with naturally acquired rabies. The overall correlation of results from all categories was about 98% (n, 104) for those that were brain positive and 100% (n, 99) for those that were brain negative. Some animals that ultimately developed rabies were found to have immunofluorescence-positive results 2 or more days before the onset of clinical signs in both natural and experimental infections. The percentage of those with positive skin immunofluorescence results increased as the onset of symptoms approached. From the midcourse period of illness to death, the correlation between skin and brain approached 100%. Different vaccines, commonly given to prevent rabies and other diseases of dogs and cats, were administered to groups of mice and were found to not produce false-positive results when their skin was examined by immunofluorescence for rabies virus antigen. These data suggest that examination of surgical biopsy specimens by immunofluorescence for rabies virus antigen is a useful and reliable diagnostic tool to evaluate the rabies status of biting dogs or cats, or to confirm a clinical diagnosis of rabies in the species tested. The biopsy evaluation of any other species as a means of assessing bite risk is not suggested by these data.

Animals↗
PubMed1983

Quantum differences in oral susceptibility of voles, Microtus pennsylvanicus, to virulent Francisella tularensis type B, in drinking water: implications to epidemiology.

Shedding nephritis in voles with chronic tularemia is the probable source of frequent contamination of streams over wide areas of the northern hemisphere. However, voles inoculated parenterally with as few as one dex viable cells of Francisella tularensis palaearctica succumb uniformly to acute tularemia, whereas voles, beavers, and muskrats often thrive in waters contaminated with the organism. Nevertheless, water-borne epizootics do occur in these animals, and at these times streams are heavily contaminated. In attempts to determine the lethal dose, per os, of the bacteria to voles, it was found that there are stable, 'order-of-magnitude' differences in susceptibility of individual weaned voles reared under uniform conditions. Also, voles thus infected often became chronically infected with bacteriuria. It is proposed that the most susceptible voles are responsible for amplification of water contamination and thus for initiation of water-borne epizootics in hygrocolic mammals and for frequent mild infections in man.

Animals↗
PubMed1980

Experimental chronic rabies in the cat.

Two cats, inoculated with a street rabies virus strain, survived with only some progressive debility and atrophy of musculature in the injected limb for 136 weeks. They had continuously increasing titers of neutralizing antibody in serum and in cerebrospinal fluid, and terminally they had high antibody titers in the brain. Virus was isolated from two brain specimens of one cat obtained at necropsy; isolation was successful only by explant culture and inoculation of explanted tissue into mice. Virus antigen was detected in eight sites in the brain and spinal cord of the same cat by frozen-section immunofluorescence. Lesions in the central nervous system consisted of neuronal degeneration and neuronophagia, associated with the prescence of inclusion bodies and widespread inflammatory cell inflitration into brain and spinal cord parenchyma, perineuronal sites, and perivascular spaces. The inflitrates contained lymphocytes, monocytes-macrophages, and a high proportion of plasma cells. These experimental cases of chronic progressive rabies resembled more closely subacute sclerosing panecephalitis of man than the usual subacute fatal rabies encephalitis of man and other mammalian species.

Animals↗
PubMed1979

Allergic encephalitis, rabies antibodies, and the blood/brain barrier.

Similarity of the syndromes of rabies and of encephalomyelitis resulting from rabies vaccination poses a problem in differential diagnosis that has had tragic consequences. That difficulty may also be largely responsible for the traditional belief that rabies is inexorably fatal, in that recovery from paralysis is interpreted as evidence that the disease was postvaccinal encephalomyelitis rather than rabies. Diagnosis is additionally complicated by presence of rabies antibodies in serum in both conditions. However, we have found that rabies antibodies elicited by vaccination do not pass the blood/brain barrier to enter the fluids of the CNS in EAE, the experimental counterpart of postvaccinal encephalomyelitis; whereas antibodies are present in high titer as a result of production in situ after recovery from rabies. Therefore a ratio of antibody concentrations of greater than 1:10 in CSF and serum indicates chronic rabies or recovery from that disease.

Animals↗
PubMed1979

Resistance to tick-borne Francisella tularensis by tick-sensitized rabbits: allergic klendusity.

Mammals become hypersensitive to ticks that feed upon them. That hypersensitivity was thought responsible for an observation that a large number of Francisella tularensis-infected Dermacentor variabilis failed to infect a rabbit previously exposed to ticks of that species. In a series of tests of that hypothesis, rabbits sensitized to ticks were often significantly more resistant than control animals to tick-borne tularemia. The conditions that determine the klendusity are thought to be variable and complex but the phenomenon must be of importance in the epidemiology of some arthropod-borne agents.

Animals↗
PubMed1978

The continuing imperatives of diversity of rabies vaccine.

Current preoccupation with and enthusiasm for the human diploid cell rabies vaccine are reminiscent of the advent of duck embryo vaccine (DEV) a quarter of a century ago. Development of the latter vaccine, considered both potent and entirely safe at the time, had the effect of paralyzing development of other vaccines, at least in the United States. Subsequent experience has demonstrated the DEV is neither potent nor entirely safe, although its use is not attended by the trepidation that accompanied the use of older vaccines. Availability in the USA of only one vaccine licensed for human use has created a hardship on both patients and physicians in as much as a large percentage of vaccinated persons suffer side effects of various degrees that pose problems for continuation of treatment. Experience has shown that most of those problems can be resolved by simple substitution of vaccine of another kind. Data obtained thus far indicate the marked superiority of diploid cell vaccine over DEV in several respects but it is not yet evident that it is completely free of allergen. Moreover, purified preparations of antigenic fractions have been obtained, and other vaccines have been shown to benefit, in apparent potency, from their capability of eliciting interferon formation. Economic considerations cannot be overlooked, and the advantage, in this respect, of suckling mouse brain vaccine in some areas of greatest need is evident.

Humans↗
PubMed1978

Enigmatic resistance of sheep (Ovis aries) to infection by virulent Francisella tularensis.

Tularemia in range sheep is an occasional cause of severe economic loss from mortality and unthriftiness as well as a hazard to persons in contact with the animals. Epizootics are unpredictable and explosive, therefore, prophylaxis is more practical than therapy. Live vaccine of proven value in man and in beavers was inoculated into mature ewes and elicited antibodies without harm to the sheep. However, challenge of immunity was not possible because virulent Francisella tularensis in large doses did not cause significant mortality in healthy, well managed, unimmunized sheep. Evidence suggests that a complex of stresses such as inclement weather, lambing and concomitant ectoparasitism render sheep more susceptible to tularemia.

Animals↗
PubMed1977

Differences in efficiency of protective effect caused by high ambient temperature in mice infected with diverse substrains of rabies virus.

We have shown previously that a non-fatal outcome of infection with street rabies virus occurs more often when mice are exposed to a high ambient temperature (HAT = 35 degrees C) early in the course of the infection. To determine what influence the virus strain had on this protective effect of HAT, we have extended these observations to studies of a fixed rabies strain, CVS and several substrains of CVS virus derived from temperature-sensitive (ts) mutants. In all cases, mortality was reduced to some extent by exposure of the animals to HAT; however, dramatic strain-specific differences in the extent of the effect were noted. Although each of the virus substrains tested was revertant in the ts character (as tested in vitro using a non-permissive temperature of 40-5 degrees C), several substrains (ts 1, ts 4, RT51) caused disease that was sensitive (greater than 90% reduction in mortality) to HAT. Mortality induced by the parental CVS virus was reduced approx. 50% at HAT. A single CVS virus substrain, VSW89, caused disease that wal less affected by HAT than was disease induced by the parental strain. As in previous studies with street virus, the incubation periods for infection with CVS virus substrains were consistently prolonged at HAT.

Animals↗
PubMed1977

Antibody response to rabies virus in Syrian hamsters.

Syrian hamsters were injected with inactivated, attenuated, and virulent rabies virus (RV), and the antibody response was quantified by a neutralization test and the immunoglobulin class of the virus antibody was characterized by indirect fluorescent microscopy. Serum antibodies to RV were found to be predominantly of the immunoglobulin G2 (IgG2) class, although IgG1 anti-RV also were detected in high-titered sera obtained after secondary challenge. Brain extracts of hamsters inoculated intracerebrally with RV contained only IgG2 anti-RV. IgA and IgM anti-RV were not detected. The preferential IgG2 response to RV is in marked contrast to the isolated IgG1 response detected after inoculation of hamsters with soluble purified protein antigens.

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