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Physiological tests of work performance and measurement of field productivity were made in 194 Sudanese cane cutters in order to study the effect of Schistosoma mansoni infection. The cane cutters were selected from two age ranges (16-24 and 25-45 years) and subdivided into three clinical groups: not infected, infected with, and infected without clinical signs of hepatosplenomegaly. Men infected with Schistosoma haemotobium, malaria (blood film), or with hemoglobin levels less than 10 g/100 ml were excluded. There was a statistically significant (P less than 0.002) higher mean hemoglobin concentration in those not infected but the mean difference was less than 1 g/100 ml. Submaximal responses to exercise on a stationary bicycle ergometer, oxygen intake, ventilation, tidal volume, cardiac frequency and estimated maximal aerobic power output calculated both in absolute terms and relative to lean body mass and leg volume were similar in the six groups of cane cutters. No significant differences were found in physique, body composition or in thermoregulatory function tests. The cane cutters were found to have little natural acclimatization to heat in terms of sweating capacity when compared with a group of fully acclimatized Sudanese soldiers. The mean productivity (mean daily weight of cane cut per man) was significantly correlated with the individual's estimated maximum aerobic capacity determined in the laboratory, but not with the degree of S. mansoni infection. The noninfected group was less "efficient" (mean productivity:oxygen intake) during cutting than the infected groups but a larger proportion of the noninfected were in their first season of cutting. There was a positive correlation between the number of seasons' cutting experience and the individual's age, degree of infection and mean productivity. Cane cutters studied in this investigation were a relatively fit, active population from whom the more seriously ill were excluded. These results do not, therefore necessarily reflect the effects of S. mansoni on physiological work capacity and productivity of more static populations in areas of high endemicity.
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PMID:Physiological performance and work capacity of Sudanese cane cutters with Schistosoma mansoni infection. 93 32

There have been few scientists who have had a greater impact on the history of vector biology than Sir Patrick Manson (1844-1922). By demonstrating that mosquitoes became infected with microfilariae in the process of taking a blood meal, he became the first to prove an association between insects and pathogens causing human and animal diseases. He also contributed substantially to the discovery of mosquito transmission of malaria parasites and was a principal force behind the founding of the London School of Tropical Medicine and the Royal Society of Tropical Medicine and Hygiene. Manson's career is reviewed in historical context as well as in relation to modern concepts of vector biology.
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PMID:Patrick Manson and the discovery age of vector biology. 140 56

The relationship between intensity of Schistosoma mansoni infection and the degree of related morbidity was suspected to differ locally within the Machakos district of Kenya. To test this possibility, prevalences of hepatomegaly and splenomegaly among 1483 school children were compared between 2 areas, Kangundo and Kambu, within this district. These areas, which were similar in many geographical and economic respects and populated by the same tribe (Akamba), had comparable levels of S. mansoni infection and no S. haematobium infection. A relationship was observed between the prevalence of hepatomegaly and intensity of S. mansoni infection, which showed no consistent difference between the 2 areas. In contrast, a relationship between the prevalence of splenomegaly and intensity of S. mansoni infection was observed only in the Kambu schools, and not in the Kangundo schools where the overall prevalence of splenomegaly was much lower. It was possible that part of the splenomegaly observed in Kambu was due to malaria. However, the observation that malaria and schistosomiasis in 2 Kambu schools were not positively correlated allowed approximations to be made of the relative contributions of each to the prevalence of splenomegaly. It was concluded that, in a school close to the river that formed the main transmission site of S. mansoni, schistosomiasis-related hepatosplenomegaly was present in at least 17% of children. The reason for the high prevalence in Kambu of hepatosplenic schistosomiasis remains uncertain, but it could include a synergistic interaction of schistosome infection with malaria.
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PMID:Differences in the rate of hepatosplenomegaly due to Schistosoma mansoni infection between two areas in Machakos District, Kenya. 175 56

Sensitivity, specificity and positive predictive values of selected clinical signs and symptoms in the diagnosis of Schistosoma mansoni infection were evaluated in 403 individuals (69% of inhabitants over 1 year of age) in an endemic area in Brazil (Divino). Highest sensitivity (13%) was found for blood in stools. Specificity over 90% was found for blood in stools, palpable liver with normal consistency and palpable hardened liver at middle clavicular (MCL) or middle sternal lines (MSL). Hardened liver at MSL (83%) or MCL (75%), and blood in stools (78%) presented higher positive predictive values for S. mansoni infection, while palpable liver with normal consistency at MCL (45%) or MSL (48%) presented smaller values. Enlarged liver without specification of its consistency has been traditionally used as an indicator of the infection in areas where malaria or Kala-azar are not endemic. Our results demonstrate that the probability that a person with blood in stools or hardened palpable liver is infected is higher than among those with palpable liver with normal consistency.
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PMID:Validity of selected clinical signs and symptoms in diagnosis of Schistosoma mansoni infection. 184 90

In the obscurity of Amoy, South China, Patrick Manson first recognized that a bloodsucking arthropod can harbor--and presumably transmit--organisms of human disease: in particular, that the house mosquito is an intermediary of the filarial parasite Wuchereria bancrofti. Manson published his find in 1878 and within two years discovered that the parasite's "embryos" (microfilariae) exhibit "nocturnal periodicity," i.e., they absent themselves from the blood during the day and reappear at night coincident with the vector's greatest biting activity. The historical sequence of Manson's two findings have been confused and reversed in the literature, and in this paper evidence is adduced that the sequence given above is correct. Until the turn of this century, zoologists thought that mosquitoes took one blood-meal and died on water a few days later. Manson theorized that filarial larvae escaped from the mosquitoes into water and that people ostensibly infected themselves by drinking the contaminated water. When, however, infective larvae were found in 1900 in the mouthparts of mosquitoes, the concept that transmission occurred by bite (malaria transmission was by then understood) proved unavoidable. Nevertheless, about 70 years after the demise of Manson's old concept, workers succeeded in transmitting several kinds of W. bancrofti-related filarial organisms by mouth to gerbils. This finding served to support Manson's speculations of 1878-1900, altered the views of the parasite group to which the filariae belong, and now raises the difficult question of whether oral infection of humans does or does not occur naturally.
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PMID:Sir Patrick Manson's studies on the transmission and biology of filariasis. 613 27

Serum immunoreactive prolyl hydroxylase protein, galactosylhydroxylysyl glucosyltransferase activity, and the aminoterminal propeptide of type III procollagen (S-Pro(III)-N-P) were measured in twenty patients with cirrhosis and ninety with various infectious diseases, and the values were compared with those in sixty apparently healthy Nigerians. The means for all three markers were elevated significantly in the patients with cirrhosis (P less than 0.001), acute viral hepatitis (P less than 0.001), amoebic liver abscess (P less than 0.001) and the early stages of Schistosoma mansoni infection (P less than 0.001 for S-Pro(III)-N-P, P less than 0.005 for the two other markers). The mean S-Pro(III)-N-P was also distinctly elevated during the early stages of Schistosoma haematobium infection (P less than 0.01) and filariasis (P less than 0.001), whereas none of the three markers was elevated during an acute attack of malaria. Significant correlations were found between the values for the three markers within the groups of patients with cirrhosis, amoebic liver abscess and schistosomiasis, the correlations for the pooled group of all patients being highly significant (P less than 0.001). The data suggest that elevated hepatic collagen formation is found not only in cirrhosis but also in several infectious diseases. The three serum markers may be useful for showing the stages of active collagen formation in various liver diseases and for predicting the development of fibrosis in acute cases if the values remain elevated.
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PMID:Three serum markers of collagen biosynthesis in Nigerians with cirrhosis and various infectious diseases. 632 66

The association between Schistosoma mansoni infection and kidney lesions was investigated in school children selected from three primary schools in Machakos District, Kenya, namely Miu (n = 159), Kitengei (n = 160) and Misuuni (n = 99) schools. The children were examined parasitologically for S. mansoni infection, clinically for enlargement of the liver and spleen, and biochemically for proteinuria and serum and urine creatinine. High prevalences of S. mansoni infection, ranging from 84-96%, were seen in all the schools, but the geometric mean intensity of egg excretion varied, being relatively low in Misuuni (31 eggs/g), medium in Miu (182 eggs/g) and high in Kitengei (413 eggs/g). The prevalence of pathological proteinuria (> or = 200 mg/l) in the schools ranged from 10.1% in Miu to 28.8% in Kitengei. No difference in the levels of proteinuria was noted between age or sex groups. No association between intensity of infection and pathological proteinuria was observed in any of the schools, nor was any correlation between organomegaly and proteinuria observed. However, significant correlations between malaria and organomegaly (p < 0.001) and between malaria and proteinuria (p < 0.05) were observed when pooling data from all schools. These findings suggest that S. mansoni induced nephrotic syndromes are not common in children from this highly endemic area of Kenya.
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PMID:A survey of Schistosoma mansoni induced kidney disease in children in an endemic area of Machakos District, Kenya. 786 51

George Carmichael Low, like so many early pioneers of Tropical Medicine, had his origin(s) in Scotland. Following a distinguished undergraduate (and early postgraduate) career, he joined Dr Patrick Manson at the newly established London School of Tropical Medicine in 1899. His first major contribution to the specialty (in 1900) was to demonstrate filariae in the proboscis sheath of mosquitoes which had been infected with Filaria bancrofti in Australia, using a technique recently learned in Heidelberg and Vienna. Shortly afterwards, he led an expedition to the Roman Campagna; this established beyond doubt mosquito-transmission of Plasmodium vivax infection to Homo sapiens. In 1901-1902, Low undertook a demanding tour of the Caribbean where he made important contributions to the understanding of the filariases, and assisted in malaria eradication. In 1902 he led a small team (the Royal Society's first sleeping sickness expedition) to investigate the 'negro lethargy' which had emerged in epidemic proportions on the northern shores of Lake Victoria in East Africa. This expedition narrowly failed to establish the aetiological agent (Trypanosoma sp.) of this disease. Following his return to London, Low became superintendent of the Albert Dock Hospital and from then onwards devoted most of his career to the London School of Tropical Medicine and the Hospital for Tropical Diseases (where he became senior physician). He wrote extensively, in addition to his clinical, teaching and administrative commitments. Perhaps Low's major contribution, however, was in establishing the Society (later Royal) of Tropical Medicine and Hygiene in 1907, with Mr (later Sir) James Cantlie.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Royal Society of Tropical Medicine and Hygiene meeting at Manson House, London, 10 December 1992. George Carmichael Low FRCP: twelfth president of the Society and underrated pioneer of tropical medicine. 824 57

Three years after intestinal schistosomiasis had been reported for the first time in the delta of the Senegal River Basin, an ultrasonographic study was conducted on 358 subjects of the community of Richard-Toll with a proven Schistosoma mansoni infection and compared with the findings from 352 uninfected subjects of a nearby town. Periportal thickening was found in 119 subjects (33%) in only one of whom it was greater than 10 mm; liver parenchyma lesions were found in 40 subjects (11%), at about the same rate in all age groups. No correlation was found between hepatomegaly and schistosomiasis. Frequency of thickening of the omentum was significantly higher in Richard-Toll than in the control group. 11% of the Richard-Toll subjects had portal vein diameters significantly larger than the values in the control group; of those, 6% had no periportal fibrosis sign in the liver. Significantly more splenomegaly was found in the infected group, though malaria as an aetiological agent cannot be ruled out. Based on periportal alterations and parenchyma lesions only, 141 (39%) subjects in the Richard-Toll group had alterations, corresponding to the World Health Organization proposed criteria for stage I; one subject had alterations corresponding to stage II. As S. mansoni infection is still new in this area, the patho-anatomical pattern is likely to change significantly in the future.
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PMID:Hepatosplenic alterations determined by ultrasonography in a population recently infected with Schistosoma mansoni in Richard-Toll, Senegal. 833 26

Ronald Ross is a brilliant and polyvalent mind. When orientated towards medicine he took the training amateurishly and ended up with a limited qualification. After 2 years as a ship doctor, he attended the compulsory complementary training in order to be admissible in the IMS, the garrison life left him with plenty of time to engage in his hobby's: painting for a short while, writing, poetry and mathematics. By the end of his first term he questioned the sense of his medical activities and decided, with a view to his career, to acquire a Public Health diploma and some complementary bacteriology. During his second term the malaria problem drew his attention. As he was unable to detect the parasite of Laveran in the blood of patients with malarial fevers he concluded that the parasite had been some lucky microscopic finding without any value and turned this parasite into ridicule. During his leave in 1894 he met Manson, who showed him the technique to put the parasite in evidence and convinced him to search for its vector which, to his opinion, should be a mosquito. Ross decided to follow this lead. With his minimal parasitological knowledge and an entomological background limited to the external appearance of mosquitoes he endeavoured to establish the life cycle of the malarial parasites. Notwithstanding some service bounded transfers, he followed the fate of the filaments of the crescents and discovered the parasite on the stomachwall of dapled-winged mosquitoes. During his special mission in Calcutta and in the absence of suitable malaria infections in man he shifted to bird proteosoma (now P. relictum) with a grey mosquito (culex) as vector. He demonstrated the complete life-cycle ending in the salivary glands of the mosquitoes and succeeded in transmitting this infection by mosquito-bites in healthy birds. This climax in his research was crowned by the attribution in 1902 of the Nobel Prize for Medicine. In the mean time he resigned from the IMS and was appointed as "Lecturer on Tropical Diseases" at the Liverpool School. He reoriented his activities to the prevention of malaria by control of the vector in its aquatic larval stage, which he tried out and promoted during his journeys to the West African Coast and other countries. His current were variegated but without salient details. Through the survey of the parasite index and the assessment of the spleen rate in children he founded the malariometry as a epidemiological tool, focussed attention on the relation of malaria and the community and on the complexity of the transmission dynamics. By handing in his resignation at the Liverpool School and moving to London he hampered further his scientific productivity. The tardy foundation of the Ross Institute did not stimulate a new impetus. He suffered a stroke which left him partially crippled an he died in his Institute.
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PMID:[Ronald Ross: a century of the transfer of malaria by mosquitoes]. 998 33


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