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Biomedical subjects

G S Nelson

Publications and source records attributed to G S Nelson.

At least 37 records · Page 2Linked to original sources
PubMed1986

The identification of eggs of Echinococcus by immunofluorescence using a specific anti-oncospheral monoclonal antibody.

A relatively simple and specific test has been developed to distinguish eggs of Echinococcus from those of other morphologically identical taeniid species. A specific anti-Echinococcus oncosphere monoclonal antibody was produced which binds in an indirect immunofluorescence test to egg-derived oncospheres of E. granulosus but not to those of other taeniid species, such as Taenia hydatigena, T. saginata, T. pisiformis, T. ovis, T. multiceps, or T. taeniaeformis. Specific fluorescence was obtained with oncospheres of E. granulosus derived from either hatch/activated viable eggs using artificial intestinal fluid or from hypochlorite/detergent treated eggs. The potential use of this test in the study of the transmission of Echinococcus in Turkana, Kenya, is discussed.

Animals↗
PubMed1985

Immunity to Onchocerca lienalis microfilariae in mice. II. Effects of sensitization with a range of heterologous species.

The model of Onchocerca lienalis microfilariae (mff) injected into CBA and T.O. strains of mice has been used to examine immunity to skin-dwelling microfilariae following exposure to a range of species of helminths. Mice which had received a primary infection with O. cervicalis mff were significantly resistant to challenge with O. lienalis mff (58% reduction relative to challenge controls). Immunization with the uterine contents (eggs and mff) of O. lienalis, O. gutturosa or O. volvulus conferred equivalent levels of protection against challenge with O. lienalis mff (66 to 75%). Similar results were obtained with immunizations in mice that employed either fresh or freeze-killed eggs of O. gutturosa. Significant reductions in the recoveries of O. lienalis mff were also demonstrated following the intraperitoneal implantation of adult male worms of O. gutturosa (30 to 52%), the adults of either sex of Dipetalonema viteae (60%), or after infection with Trichinella spiralis (27 to 81%). Infections with the trematode, Schistosoma mansoni, had a negligible effect on mff recoveries. It is concluded that partial resistance in mice to Onchocerca mff may be stimulated by factors, yet to be determined, that are neither stage nor species-specific.

Animals↗
PubMed1983

Long-term infection of Schistosoma mansoni in a vervet monkey (Cercopithecus aethiops).

Schistosoma mansoni infection in Cercopithecus species monkeys has been previously monitored for up to five years. This is an account of observations made during an autopsy on a male vervet monkey which had harboured the parasite for 15 years. Viable eggs had been recovered from the faeces throughout the infection, being hatched to observe the emergence of miracidia. Apart from a nodular appearance of the liver capsule, which was noted before the perfusion, and localized haemorrhaging in the large bowel there was comparatively little pathology attributable to the parasite. 86 worms were recovered from the mesenteries by perfusion. The distribution of worm eggs in the tissues was mainly in these two organs, although with the remarkably low incidence of granuloma it is likely that the schistosome infection would have been overlooked in a routine autopsy. It is stressed that these observations have been made on an individual animal, but it is felt that there is real significance with respect to the aetiology of natural transmission.

Animals↗
PubMed1982

Morphological characteristics and isoenzyme patterns of an Onchocerca sp. found in cattle in Southern Mexico.

An Onchocerca sp. was isolated from the nuchal ligaments of 78 out of 79 naturally infected cattle in Southern Mexico. Infections were moderate to heavy, averaging 20-30 parasites per nuchal ligament. Microfilariae were concentrated in the skin of the head and neck, although small numbers were found in the skin of the withers, brisket and medial abdomen. High numbers of microfilariae were found in the skin around the eye, but not in the ocular tissues themselves a situation dissimilar to that found in human onchocerciasis. Morphologically, adult females, males and microfilariae were identified as being O. gutturosa. Analysis of the isoenzyme patterns of LDH, MDH, PGM, GPI, PGD and ES of adult female worms, showed the Mexican parasite to be the same as O. gutturosa from England and Australia.

Animals↗
PubMed1981

Issues in filariasis--a century of enquiry and a century of failure.

A great deal is known about the biology of the filarial parasites infecting man and of their transmission, their clinical manifestations, their treatment and their control but many more people are infected with Bancroftian filariasis and onchocerciasis today than more than 100 years ago when Manson discovered the first live cycle. There has been some success in the control of the Simulium vectors of onchocerciasis in parts of Africa and mass chemotherapy has helped to reduce Bancroftian filariasis in a few Pacific Islands but the main endemic areas have seen no benefit from all the advance in the techniques for controlling these diseases. There is an obvious need for more research to find better tools that are less hazardous to the environment and more acceptable to the affected communities. Fortunately the combined resources of the United Nations Development Programme, the World Bank for Development and the World Health Organization in the setting up of the Special Programme for Research and Training in Tropical Diseases has stimulated a renewed interest in these problems. An obvious area for further research is on the epidemiology of the disease with special emphasis on transmission of the parasites to help with the development of predictive models which might assist in the design and evaluation of control programmes. There is a need for novel approaches to kill the vectors and for the development of more effective and less hazardous drugs. There is a need for immunologists to try to produce vaccines which will help to consolidate other methods of control but of more immediate values will be the production of more specific immunological diagnostic tests and methods for modifying the immunopathology processes caused by the disease and accentuated by treatment. But whatever new tools are produced it is still true to say that control measures will be effective only if there is active cooperation by the affected communities. It is therefore essential that laboratory research is supplemented with research on human behaviour in relation to the transmission of the diseases and also on the acceptability of control measures if we are to avoid the disappointments of many other antiparasitic control campaigns.

Animals↗
PubMed1981

The effect of praziquantel on Schistosoma haematobium, S. japonicum and S. mansoni in primates.

Baboons infected with S. haematobium and vervet monkeys infected with S. japonicum were treated orally with different dosage regimens of 2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]isoquinolin-4-on e(praziquantel, EMBAY 8440, Biltricide) and were autopsied and perfused 3--4 months after treatment. The results suggest that a single oral dose of 75--100 mg/kg body weight is likely to be effective against S. haematobium in the baboon. Female worms of S. haematobium are apparently more susceptible to the compound than male worms. The classic hepatic shift of adult schistosomes was observed in all the primates, but histopathological studies showed that numerous worms also died in situ, only a few being found in the lungs. The results obtained with praziquantel against S. japonicum in the vervet monkey show that a complete cure was obtained in the animal given 50 mg/kg on five consecutive days. A predominant characteristic in the pathology of the animals given a curative dose of praziquantel was the total resolution of cellular reaction and fibrosis in the tissues containing known numbers of dead residual eggs. In the baboons infected with S. haematobium, the ureters and bladders had recovered their functional integrity and in the vervet monkeys infected with S. japonicum, a similar resolution of pathology in the liver and bowel was apparent.

Animals↗
PubMed1980

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. I. Epizootiological observations on Schistosoma bovis in the White Nile Province.

A 2-year epizootiological study was carried out on Schistosoma bovis in cattle in an enzootic area of the Sudan. The prevalence of infection, as judged by the Pitchford fecal egg counting technique, was very high, approaching 90% in 1.5-year-old animals. There was, however, a lower prevalence in older cattle, and this trend was also seen with the fecal egg counts. This suggests that the cattle gradually acquire resistance to reinfection, particularly since there seems to be little age-related variation in the amount of water contact. Monthly incidence rates, estimated from fecal examinations of initially uninfected "tracer" calves showed a marked seasonal pattern, being much higher in the hot summer months, and snail infection rates showed a similar seasonal pattern. In addition, both the monthly incidence measurements and the snail infection rates showed that transmission was much heavier in 1976 than in 1977. Epizootics such as those recorded previously in this area presumably arise from exceptionally intense transmission years.

Animals↗
PubMed1980

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. II. Experimental demonstration of naturally acquired resistance to Schistosoma bovis.

Epizootiological observations on Schistosoma bovis in cattle at Kosti, Sudan, showed a significant fall in age-specific prevalence and intensity with age, based on fecal egg count. To test the possibility that this is due to acquired resistance, Kosti cattle and a control group of cattle of similiar breed and age from a nonenzootic area were experimentally challenged with 70,000 S. bovis cercariae. Clinical observations showed very clearly that the Kosti cattle were able to withstand almost completely the effects of the challenge, whereas the controls developed lethal infections. Resistance was further demonstrated by clear differences between the two groups in terms of their body weights, hematological measurements, histopathological and pathophysiological responses, and worm and egg counts. The data suggested that the main basis of the resistance was a suppression of egg production by the worms from the challenge, rather than absolute prevention of their maturation. There was also evidence of a suppression of the fecundity of worms in the naturally infected Kosti cattle.

Animals↗
PubMed1980

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. III. Field testing of an irradiated Schistosoma bovis vaccine.

Previous work has shown that cattle can acquire a strong resistance to Schistosoma bovis infection following repeated natural exposure. Partial resistance to a laboratory challenge with S. bovis has also been demonstrated in calves after immunization with an irradiated schistosomular or cercarial vaccine. The aim of the present study was to see whether this type of vaccine could protect calves under the very different conditions of natural exposure to S. bovis in the field. Thirty 6- to 9-month-old calves were each immunized with 10,000 irradiated S. bovis schistosomula by intramuscular injection and 8 weeks later were released into an enzootic area along with 30 unvaccinated animals. The calves were followed up for 10 months, during which period protection was evidenced by a lower mortality rate, a slower rate of acquisition of infection, and lower fecal egg counts in the vaccinated calves. Necropsy of the survivors showed 60--70% reductions in worm and tissue egg counts of the vaccinated calves as compared to those not vaccinated.

Animals↗
PubMed1980

Schistosoma bovis in calves: the development and clinical pathology of primary infections.

The clinico-pathological effects of Schistosoma bovis were monitored in zebu calves for a year after exposure to 100 or 200 cercariae/kg body weight and were related to the number and reproductive activities of the parasites present. The disease was characterised by diarrhoea, weight loss or poor weight gain, anaemia, serum protein changes and eosinophilia. These changes were broadly related to the level of infection and were most prominent during the two months following patency when faecal egg counts were highest. Subsequently, the condition of most animals improved. This was associated with a marked reduction in faecal egg excretion which in turn was related to worm deaths, reduced worm fecundity and egg retention in the tissues.

Animals↗
PubMed1979

The prevalence and distribution of Mansonella ozzardi in coastal north Trinidad, W.I.

A day blood smear survey for Mansonella ozzardi in the north coast communities of Trinidad recorded a prevalence of 4.8% in 4,488 persons examined. Prevalence rates were highest in the four western-most communities, where the vector, Culicoides phlebotomus, is a severe nuisance problem. Prevalence rates increased with age and were higher in males than in females. Mean microfilaria densities were low in both sexes up to 50 years of age but in older males the density increased with age. Wuchereria bancrofti infections were detected in five of the ten communities surveyed.

Adolescent↗