Biomedical subjects
Publications and source records attributed to N O Nielsen.
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The relationship between HIV, lymphatic filariasis, malaria (Plasmodium falciparum) and intestinal helminths (Ascaris lumbricoides, Trichuris trichiura and hookworm) was assessed in a cross-sectional study conducted in 2002 among 907 adults in Tanga Region, Tanzania. Overall prevalences were 7.9% for HIV, 43.5% for Wuchereria bancrofti-specific circulating filarial antigen (CFA), 12.3% for P. falciparum, 1.2% for A. lumbricoides, 7.1% for T. trichiura and 75.7% for hookworm. Anaemia was assessed separately for males and females and was found to be more prevalent among females (58.8%) than males (34.8%). When sex and age were controlled for, there was a statistically significant positive association between HIV and W. bancrofti (CFA) infection and between malaria and HIV, but not between malaria and W. bancrofti (CFA) infection. Hookworm infection was positively associated with W. bancrofti (CFA) infection but, surprisingly, negatively associated with HIV. Infection with HIV and hookworms, but not malaria, was associated with a significant reduction in haemoglobin concentration. These associations are likely to reflect underlying mechanisms that need to be clarified to better understand the role of co-infections in HIV pathogenesis, and vice versa.
The promotion of human health must be embedded in the wider pursuit of ecosystem health. Interventions will be impaired if ecosystem-linked determinants of health are not taken into account. In the extreme case, if ecosystems lose their capacity for renewal, society will lose life support services. Essential features of ecosystem health are the capacity to maintain integrity and to achieve reasonable and sustainable human goals. An ecosystem approach to research and management must be transdisciplinary and assure participation of stakeholders. These requisites provide a means for science to better deal with the complexity of ecosystems, and for policy-makers and managers to establish and achieve reasonable societal goals. The ecosystem approach can determine links between human health and activities or events which disturb ecosystem state and function. Examples are: landscape disturbance in agriculture, mining, forestry, urbanization, and natural disasters. An understanding of these links can provide guidance for management interventions and policy options that promote human health. An ecosystem approach to management must be adaptive because of irreducible uncertainty in ecosystem function.
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A cross sectional study of the prevalence and intensity of Balantidium coli in pigs was carried out on a Danish research farm. The prevalence of B. coli infection increased from 57% in suckling piglets to 100% in most pig groups > or = 4 weeks old. The mean number of cysts per gram faeces (CPG) of pigs aged 12 weeks and younger were < or = 206, whereas pigs aged 28 weeks and > 52 weeks had significantly higher counts of > or = 865 CPG. Although some lactating sows had very high CPG's, no significant differences in CPG could be detected between the intensities of pregnant sows, lactating sows and empty and dry sows. No human cases of B. coli infection have been published in Denmark though it is zoonotic.
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The severity of lymphoproliferative disease associated with malignant catarrhal fever was extremely variable among 25 animals at the San Diego Wild Animal Park. Severe lymphoproliferative disease was seen in 3 of 10 Formosan Sika deer (Cervus nippon taiouanus), 3 of 6 Indian Axis deer (Cervus a axis), 3 of 6 Barasingha deer (Cervus d duvauceli), and 1 of 3 Nilgai (Boselaphus tragocamelus). Two Sika deer and 2 Barasingha deer had lesions morphologically indistinguishable from lymphosarcoma. Our findings were consistent with the hypothesis that alcelaphine herpesvirus-1 has oncogenic potential.
Nilgiri tahr (Hemitragus hylocrius) are native to India and are a rare zoo exhibit. This report describes an acute respiratory disease in tahr that caused the death of 15 of 16 animals in an extensive exhibit of about 35 acres where they were housed together with a variety of other exotic species of ruminants. The deaths occurred in two separate outbreaks and were associated with losses from malignant catarrhal fever in other ruminants in the exhibit. The most prominent clinical sign was severe dyspnea, and death occurred within five days. The principal lesions were an acute nonsuppurative inflammation of the respiratory tract and pulmonary vessels, lymphadenopathy and lymphoid cell infiltration in the organs of some animals. It was conjectured that the tahr died of a unique pneumonic form of malignant catarrhal fever. Attempts at viral isolation were negative.
Malignant catarrhal fever (MCF) was diagnosed in a 2-week-old Formosan sika deer. The fawn had been previously exposed to a clinically normal neonatal wildebeest calf from which alcelaphine herpesvirus-1 was isolated. Alcelaphine herpesvirus-1 was isolated from buffy coat leukocytes and nasal and ocular secretions of the fawn during the acute illness. The fawn clinically recovered after 3 weeks. Virus was not recovered from blood at this time. Dexamethasone, given 4 months after clinical recovery, resulted in reisolation of MCF virus from blood and recrudescence of clinical MCF. The deer was euthanatized. At necropsy, pathognomonic lesions of MCF, granulomatous disease, and malignant lymphoma were observed. Antibodies to bovine leukosis viral antigens were not detected in the serum. The epidemiologic and pathogenetic importance of the findings are discussed.
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The permeability of weanling swine small intestine was estimated using measurements of filtration coefficients and equivalent pore size. Hypertonic solutions of mannitol, erythritol and urea were used to calculate reflection coefficients in the duodenum, mid jejunum and distal jejunum. Estimated effective pore radius was 6.4-7.4, 5.6-7.2 and 4.7-4.9A degrees in the three respective regions. Similarly the filtration coefficient induced by hypertonic solutions of mannitol decreased significantly in the distal jejunal segments. The results show an aboral gradient of decreasing permeability along the small intestine of the weanling pig. In situ incubation of loops in the proximal jejunum with a heat stable Escherichia coli enterotoxin for one hour did not significantly change the effective pore size as calculated from reflection coefficients of hypertonic solutions of erythritol and urea. However, the filtration coefficients of loops exposed to the enterotoxin were significantly greater than control loops with hypertonic solutions of erythritol and urea but not mannitol. This suggests the occurrence of a slight reduction in epithelial porosity. The results support the hypothesis that intestinal secretion induced by heat stable E. coli enterotoxin is not the result of an increased mucosal permeability.
The effect of cholera toxin, heat labile and heat stable Escherichia coli enterotoxin on mucosal cyclic AMP concentrations was determined on the proximal jejunum of weanling pigs and young rabbits. Ligated loops were injected with solutions containing no enterotoxin for control and either cholera toxin, heat labile or heat stable E. coli enterotoxin. The loops were drained after either two, four or six hours incubation at which time accumulated fluid was recorded and mucosal samples removed for determination of cyclic AMP concentration. In the rabbit, cholera toxin and heat labile, but not heat stable E. coli enterotoxin stimulated intestinal secretion while in the pig all three enterotoxins induced net fluid accumulation. Cholera toxin and heat labile, but not heat stable E. coli enterotoxin elevated rabbit mucosal cyclic AMP concentrations. In the pig these enterotoxins had no significant effect on mucosal cyclic AMP concentrations. The results are inconsistent with the hypothesis that the adenyl cyclase system is an essential step for enterotoxin induced intestinal secretion. The activation of intestinal adenyl cyclase by bacterial enterotoxins may only be an associated and not a necessary event for the stimulation of intestinal secretion.
Glucose, l-alanine, l-aspartate, l-methionine and glycine enhanced net fluid and electrolyte absorption in acute isolated loops of the proximal jejunum of weanling swine. The effect of glucose on intestinal secretion induced by heat stable and heat labile Escherichia coli entero-toxin, cholera toxin and theophylline was examined in both the proximal and distal jejunum of weanling swine. In the proximal jejunum glucose enhanced the rate of net fluid and electrolyte absorption. This increase was accompanied by an increase in unidirectional dosium absorption. In loops exposed to either heat stable or heat labile enterotoxins, glucose significantly decreased the rate of net fluid and electrolyte secretion. The magnitude of glucose enhancement in loops exposed to heat stable and heat labile enterotoxins was similar to adjacent control loops. However, glucose enhancement did not occur in loops exposed previously to cholera toxin or concurrently to theophylline. Therefore, cholera toxin and theophylline may inhibit substrate dependent sodium absorption in the proximal jejunum. In the distal jejunum glucose enhancement did occur but the rate of enhancement was less than in the proximal jejunum. In this region glucose enhancement was not evident in loops exposed to either theophylline, heat stable, heat labile or cholera toxin.
The effect of heat stable and heat labile Escherichia coli enterotoxins or cholera toxin in combination with theophylline on net water, sodium and chloride and unidirectional sodium and chloride fluxes was examined in acute isolated loops of jejunum of weanling swine. The effect of heat stable enterotoxin in combination with theophylline was determined in loops located in the proximal jejunum, while combinations of theophylline and either heat labile enterotoxin or cholera toxin were studied in the distal jejunum. In each situation the addition of theophylline resulted in an additive rather than a synergistic increment of intestinal secretory activity. This study implies that the intestinal adenyl cyclase system and enterotoxin induced intestinal secretion may not be directly related in the swine small intestine.