Salmon gill poxvirus disease in Atlantic salmon fry as recognized by improved immunohistochemistry also demonstrates infected cells in non-respiratory epithelial cells.

Gill diseases cause serious losses in farming of Atlantic salmon and the number of agents involved increases. Salmon gill poxvirus (SGPV) and the gill disease in causes where SGPV apparently was the only disease-causing agent were initially characterized. Recently, it was further shown that SGPV can be a common denominator in widely different multifactorial gill diseases. Here, we present the challenge of diagnosing gill disease with SGPV in salmon fry of 0,3-5 grams. Apoptosis of gill lamellar epithelial cells and hemophagocytosis was also observed in fry similar to findings in smolts and grow-out fish. Using our newly developed immunohistochemistry method, we further demonstrate that some of the apoptotic epithelial cells covering the oral cavity were positive for SGPV. Thus, SGPV is not restricted to respiratory epithelium alone and may infect the fish at very early life stages. Furthermore, as the cases examined here are from Norway, Faroe Island and Scotland, we show that SGPV is more widespread than previously reported.

Transition dynamics of HIV disease in a cohort of African prostitutes: a Markov model approach.

The progression of HIV-related disease from infection to death is represented as a staged Markov model. Transitions between stages are considered reversible. The model is fitted to data from a cohort of African prostitutes by means of maximum likelihood. It appears that the progression to symptomatic disease (Centers for Disease Control stage IV) in this population is considerably more rapid than that reported from studies in Western countries.

PIP: Identifying the incubation period of HIV infection is important for individual prognoses, for developing and testing intervention strategies, for determining the reproductive rate of the disease, and for prevalence of the disease. Mathematical modeling of HIV infection in Africa is necessitated because the disease is more widespread and the immune system is constantly active due to the exposure to diseases such as malaria and tuberculosis. The Markov model for this analysis was selected because parametric estimation is not based on the time a stage is entered, but on the duration between observations and the stages at the time of observation. The HIV infected female prostitutes in the Pumwani area of Nairobi, Kenya (a population primarily of Tanzanian origin) have been identified as a study population since 1985, and seen every 6 months in clinic, or as needed. Data are constricted by the movement out of the area in the end stage of disease, which is only partially solved by tracking with community health workers. The stages identified in incubation estimation are stage 1: seropositive but symptom free (CDC stage II); stage 2: generalized lymphadenopathy (CDC stage III); stage 3: symptomatic disease (CDC stage IV); and stage 4: death. Data reflect the movement back and forth between stage 1 and 2, between 2 and 3, so the model is not a pure Longini model but rather a timed homogeneous staged model with reversible stages called transition parameters computed in a numerical differentiation. The Fortran computer program for the analyses is available from the authors. The results suggest a quick transition between seroconversion and lymphadenopathy (2.4 months) and unlikely reversal, with the mean waiting time until passage to stage 3 is approximately 2.6 years and conversions are common. Since opportunistic infections are treatable, this makes sense. Assuming a correct model, the estimation of the transition time of 20 months of h34 value of .01 and .05, the mean passage time from stage 1, 2, 3 to 4 (death) is 9.1, 8.9, and 6.2 years 12.9, 12.7, and 10.1 years respectively. The implications are that 1) when infectiousness is hypothesized to be not uniform, peak infectivity occurs earlier in Africa than in the West at least among prostitutes, or 2) if infectivity is constant throughout the incubation period, then HIV transmission must be higher in Africa to explain the high rate of infection.

Dental caries in developing countries in relation to the appropriate use of fluoride.

Although it is widely believed that caries prevalence in developing countries is increasing rapidly, a review of studies from Africa and China provides equivocal evidence. Data from child and adult populations indicate that the disease is almost ubiquitous but with a slow rate of progression. Theoretically, administration of fluoride in such populations should result in reducing caries progression rates, but too little is known about the magnitude of the effect, and therefore about the cost-effectiveness of different methods of fluoride administration. The lack of a developed infrastructure and of trained personnel in many developing countries limits the applicability of many strategies. Methods of fluoride administration that minimize systemic exposure are to be recommended where affordable or practical. In the light of economic constraints and slow caries lesion progression rates, however, improvements in oral hygiene practices may be the most important method of controlling the disease whether or not fluoride is available or accessible.

Tooth mortality in an adult rural population in Kenya.

This paper reports on the pattern of tooth loss in a random sample of 1131 adults aged from 15 to 65 years in a rural area of Kenya in which access to formal dental care is minimal. We found that the majority of the population retained most of their dentition in a functional state even up to the age of 65 years: In all age groups, more than 50% had at least 26 teeth present, and more than 90% had at least 16 teeth present. The prevalence of edentulousness was less than 0.3%. The principal cause of tooth loss in all age groups was caries, and this was true for all tooth-types except incisors, for which periodontal disease was the main cause of tooth loss. The cultural practice of removing lower central incisors was observed only in those over 40 years of age. More teeth were lost due to caries among women than among men, while the reverse was true for teeth lost due to periodontal diseases. In view of the fact that most people retain most of their teeth throughout life, it is suggested that the most appropriate strategies for dental health care in this population should be those promoting self care, rather than the introduction of a formal treatment-oriented approach provided by dentists.

The nature and mechanisms of dental fluorosis in man.

Any use of fluorides, whether systemic or topical, in caries prevention and treatment in children results in ingestion and absorption of fluoride into the blood circulation. The mineralization of teeth under formation may be affected so that dental fluorosis may occur. Dental fluorosis reflects an increasing porosity of the surface and subsurface enamel, causing the enamel to appear opaque. The clinical features represent a continuum of changes ranging from fine white opaque lines running across the tooth on all parts of the enamel to entirely chalky white teeth. In the latter cases, the enamel may be so porous (or hypomineralized) that the outer enamel breaks apart posteruptively and the exposed porous subsurface enamel becomes discolored. These changes can be classified clinically by the TF index to reflect, in an ordinal scale, the histopathological changes associated with dental fluorosis. Compared with Dean's and the TSIF index, we consider the TF index to be more precise. Recent studies on human enamel representing the entire spectrum of dental fluorosis have demonstrated a clear association between increasing TF score and increasing fluoride content of the enamel. So far, no useful data on dose (expressed in mg fluoride/kg b.w.)-response (dental fluorosis) relationships are available. In this paper, we have, therefore, re-evaluated the original data by Dean et al. (1941, 1942), Richards et al. (1967), and Butler et al. (1985) from the USA, by applying the equation of Galagan and Vermillion (1957) which permits the calculation of water intake as a function of temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental fluorosis in an area of Kenya with 2 ppm fluoride in the drinking water.

We examined 102 children born and reared in an area of rural Kenya with 2 ppm fluoride in the drinking water for dental fluorosis, using the index developed by Thylstrup and Fejerskov (1978). The prevalence of dental fluorosis was 100%, 92% of all teeth exhibited a TFI score of 4 or higher, and 50% of the children had pitting or more severe enamel damage in at least half the teeth present. The fluorotic changes showed a high degree of bilateral symmetry. The intra-oral distribution of the changes corresponded to the pattern of fluoride-induced enamel changes reported by other investigators in high-fluoride areas. The high prevalence and severity of dental fluorosis in a 2-ppm-fluoride area is in accordance with recent observations on dental fluorosis being very prevalent in Kenya, even in low-fluoride areas (less than 1 ppm F). We are presently investigating the possible variables which may explain this unexpected susceptibility of large populations in Eastern Africa to fluorosis from exposure to low levels of fluoride.

The effect of sucrose on plaque pH in the primary and permanent dentition of caries-inactive and -active Kenyan children.

The hypothesis that the Stephan pH responses of dental plaque would be different in caries-active and -inactive individuals was tested in 20 seven-year-old and 19 14-year-old Kenyan children. In each age group, half the children had greater than or equal to 2 dentin cavities; the other half had no such lesions. With a palladium-touch microelectrode, interdental plaque pH was monitored between m1/m2 in each quadrant in the primary dentition and in the four molar/premolar regions in the permanent dentition. pH was also monitored in caries cavities in the occlusal surfaces of lower first molars and on the tongue. pH was measured before and up to 60 min after the children rinsed with 10 mL of 10% sucrose. Caries status of the individual was unrelated to plaque pH in comparable non-carious sites in both of the age groups. The pH minimum in the maxilla was about 0.5 pH units lower than that in the mandible. Active occlusal caries lesions had a resting pH value of about 5.5, about 1 pH unit lower than that of sound surfaces. The pH dropped to about 4.5 in caries lesions and recovered slowly. In sound occlusal sites, a pH drop to about 6.0 was followed by a relatively rapid return to the resting value. Thus, when the mean values were considered, the classic Stephan curve response was evident. However, when the pH changes at single sites were considered at various time intervals, a substantial, erratic fluctuation was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Associations between salivary levels of Streptococcus mutans, Streptococcus sobrinus, lactobacilli, and caries experience in Kenyan adolescents.

Salivary levels of mutans streptococci (S. mutans and S. sobrinus) and lactobacilli were determined in a random sample of rural Kenyans between 15 and 19 years of age (n = 149). It is possible for the natural history of dental caries in this population to be studied since it is characterized by a limited access to conventional dental treatment. Using a short set of biochemical tests, we identified from seven to ten presumptive mutans streptococcus colonies--cultured from the saliva of each individual--to differentiate between S. mutans and S. sobrinus. No colonies resembling S. rattus (S. mutans serotype b) were isolated. Lactobacilli were identified as Gram-positive, catalase-negative rods. The mean D1-4MFS and D3-4MFS were 7.03 +/- 6.43 and 1.46 +/- 3.44, respectively. The mean mutans streptococcus and lactobacillus levels were 8.7 x 10(4) and 6.7 x 10(4), respectively. The salivary mutans streptococcus and lactobacillus levels were significantly correlated (p less than 0.01). Of the subjects, 64% harbored only S. mutans, 4% only S. sobrinus, 30% both species, and 2% neither. Lactobacilli were ubiquitous. The caries experience of the group was significantly (p less than 0.001) correlated with both the total salivary level of mutans streptococci and the salivary S. mutans levels, but not with the salivary S. sobrinus level.

From development to sustained crisis: structural adjustment, equity and health.

We argue that the nature of the economic crises in sub-Saharan Africa cannot be understood outside the context of the legacy of colonialism and class formation. Structural adjustment programmes serve to exacerbate inequalities and threaten to reverse the social gains of the majority achieved through the struggle for independence, in the interest of the indigenous capitalist class. Under such circumstances social scientists have a social responsibility to take a stand against the current policies that have led to an unprecedented decline of the health status of the poor; their skills must be put at the disposal of the oppressed with a view to giving voice to the experiences and needs of the majority.

Inhibition of protease activities of periodontopathic bacteria by extracts of plants used in Kenya as chewing sticks (mswaki).

Extracts from five plants used as chewing sticks, and tannic acid, gallic acid and methyl ester of gallic acid, were tested for their ability to inhibit proteolytic activities of three strains of Bacteroides gingivalis, three strains of Bacteroides intermedius and two strains of Treponema denticola. Aqueous extract from the plants Rhus natalensis and Euclea divinorum were the most inhibitory of those tested, inhibiting by 50% the proteolytic activity of the test organisms, at concentrations of up to 200 micrograms/ml. Tannic and gallic acids had similar effects at concentrations of less than 10 micrograms/ml, while the methyl ester of gallic acid was less inhibitory. These findings suggest that extracts from plants used as chewing sticks may possess enough inhibitory components to interfere with the virulence and growth of periodontopathic bacteria in vivo, provided they are able to gain access to the subgingival sites such bacteria preferentially inhabit.

Dental caries in 12-year-old urban and rural children in Zimbabwe.

608 12-yr-old children in Harare, and 556 in rural areas of Mashonaland and Central Province, Zimbabwe, were examined for dental caries in 1985. 27.6% of children in the urban area, and 20.9% in the rural, had caries (P less than 0.01). The mean DMFT in urban and rural areas was 0.57 (+/- 1.13) and 0.49 (+/- 1.42), respectively (P = 0.29). Girls had higher levels of caries than boys. Most of the caries occurred on occlusal surfaces, and first molars were the most affected of all teeth. Caries experience was similar to that reported 10 yr previously in Zimbabwe, and similar to that found recently in 12-yr-olds in Kenya and Tanzania. The authors question whether in fact developing countries having high or increasing levels of caries in 12-yr-olds constitute the exception or the rule with regard to trends in dental caries prevalence.

A new approach to investigating associations in periodontal disease data.

This paper presents a method for the analysis of data originating from studies of destructive periodontal disease. The proposed method is an extension of the Mantel-Haenszel technique for the analysis of case-control studies and allows for expression of the site-specificity of destructive periodontal disease while maintaining the individual as the unit of analysis. Using data originating from a cross-sectional study of periodontal breakdown and oral hygiene parameters in a random sample of adult rural Kenyans, the proposed method is illustrated and the results compared with results obtained when two alternative analytical methods are used. The results demonstrate that the choice of analytical strategy may have profound implications for the conclusions to be drawn. Depending on the strategy chosen, one may draw conclusions which are qualitatively different and the present study indicates that the direction of these differences is not predictable.

Dental caries prevalence amongst 12-year-old urban children in East Africa.

It is commonly believed that the prevalence of dental caries in developing countries is increasing, though in Kenya and Tanzania there is insufficient information to confirm such trends. In order to test the hypothesis, therefore, 762 children in Dar es Salaam and 802 children in Nairobi aged 12 yr in 1984 were examined for dental caries as part of a baseline study to monitor changes of prevalence with time. Dental caries was recorded by surfaces using the criteria recommended by the WHO and examinations were performed by standardized examiners. The mean DMFT in Dar es Salaam of 0.67 (SD 1.20) was significantly higher than that for Nairobi, 0.51 (SD 1.23). No differences were found in the mean DMFS index. Nairobi children had a greater number of filled teeth and surfaces. Although a greater proportion of children were caries-free in Nairobi than in Dar es Salaam, amongst those with caries, Nairobi children had significantly higher DMFS scores, and a greater proportion with DMFS greater than 4. The possible reasons for such findings are discussed. The mean DMFT and DMFS reported here are amongst the lowest reported in the recent literature from both countries.

Tooth and surface patterns of dental caries in 12-year-old urban children in East Africa.

In this report on the findings of a baseline study designed to monitor changes in the prevalence of dental caries in 12-yr-old children in Dar es Salaam and Nairobi, the details relating to the pattern of carious attack on particular tooth and surface types are described. In both populations molars accounted for over 90% of all affected teeth and in both groups first molars were more affected than second molars. Very few anterior teeth were affected in either population, though caries of the incisors and canines accounted for a greater proportion of affected teeth in Nairobi (3.4%) than in Dar es Salaam (0.6%). Significantly more mandibular first and second molars were affected in Dar es Salaam than in Nairobi, though in Nairobi the maxillary first molars were more affected than in Dar es Salaam. Occlusal surfaces were the most common site for caries in both populations. With the exception of buccal surfaces, smooth surface caries tended to be higher in Nairobi than in Dar es Salaam. Dar es Salaam children had, however, a significantly higher mean DFS score for occlusal surfaces. The preponderance of occlusal caries indicates that relatively simple restorative care is required to meet the needs of the two populations, and it is suggested that such care could be largely provided by auxiliary dental personnel.

Validity of CPITN's assumptions of hierarchical occurrence of periodontal conditions in a Kenyan population aged 15-65 years.

In order to study the validity of the hierarchical principle of the CPITN we used data originating in a cross-sectional study of periodontal disease in a random sample comprising 1131 Kenyans aged 15-65 yr to determine, for each tooth present in each individual, the absence or presence of gingival bleeding, of dental calculus, of a pocket of 4-5 mm or a pocket of 6+ mm, such that each tooth had a separate recording for bleeding, calculus, pocket 4-5 mm and pocket 6+ mm. According to the hierarchical principle of CPITN a tooth with pockets as the most severe finding is assumed positive also for calculus and bleeding, and a tooth with calculus as the most severe finding is assumed positive also for bleeding. Our analysis showed that calculus as the most severe finding of a tooth overestimates the occurrence of bleeding by up to 18%, depending on age of the individuals and the set of teeth examined. Pockets as the most severe finding in a tooth overestimates the occurrence of bleeding by up to 13%, and overestimates calculus by up to 54%, most pronounced in the younger age groups. The effect of these overestimations on prevalence and severity estimates was the most pronounced for the severity measures, particularly regarding the severity of bleeding, whereas prevalence estimates remained relatively unaffected. Undoubtedly, this result should be seen in the light of a very high prevalence and severity of both bleeding and calculus in this population.

Influence of CPITN partial recordings on estimates of prevalence and severity of various periodontal conditions in adults.

This study compares the results of a full mouth examination with the results of examining only the CPITN selection of 10 index teeth 17/16, 11, 26/27, 47/46, 31 and 36/37 for estimates of prevalence and severity of the conditions assessed with the CPITN, i.e. gingival bleeding, dental calculus, pockets 4-5 mm deep and pockets 6+ mm deep. The mean number of sextants recorded with bleeding or with calculus was generally overestimated when examinations were based on the CPITN selection of index teeth, whereas the mean number of sextants with pockets, whether moderate or deep, were generally underestimated. Similarly, the prevalence of pockets, whether moderate or deep, was underestimated in virtually all age groups while the prevalence of calculus was overestimated in all age groups and the prevalence of bleeding was overestimated among persons below 30 yr of age. We conclude that the partial recording approach of the CPITN methodology is reasonably well suited for identifying persons who are relatively healthy according to the hierarchy of the CPITN parameters. There is, however, a considerable risk that persons presenting with the more severe conditions, i.e. pockets, will be overlooked if only partial recordings are performed.

A random effects model for some epidemiological features of dental caries.

We describe a random effects model for caries lesion development and progression based on considering the effects of the pH fluctuations over time in microbial dental plaque as a Wiener process with a single absorptive barrier. The model predicts that the period of greatest risk to developing caries occurs shortly after eruption, but thereafter the longer a surface survives without developing a lesion, the less likely will it be that a lesion will subsequently develop. The model is able to anticipate why the effect of water fluoridation on caries prevalence is most pronounced when caries is diagnosed at cavity level. This model offers one way in which the variability which characterizes the complex ecosystem associated with dental caries may be considered a subject of interest for enhancing our understanding of its pathogenesis and epidemiology.

Caries prevalence in Africa and the People's Republic of China.

Problems arise when attempting to compare caries data collected in both Africa and the People's Republic of China. These difficulties are not only the result of differences in the criteria used for the diagnosis of caries but are also due to the diversity of cultural and social conditions existing within each of the geographical areas. However, interpreted with caution, the data seem to suggest that caries experience among children is still fairly stable and at a low level, in contrast to the predictions of a decade ago. When comparing data from adult and elderly cohorts, however, caries is seen to be a widespread disease with continuing slow progression throughout life.

Fluctuation of fluoride concentrations in drinking waters: a collaborative study.

The aim of this study was to describe the variations with time in the concentrations of fluoride in drinking water sources in Greenland, Kenya, Greece, Denmark and Ireland. Water samples were collected monthly and shipped to laboratories in Aarhus for electrometric analyses. In Narssaq, Greenland the fluoride concentration of a single piped water supply ranged from 0.3 to 2.8 ppm, the variations being related to climate, precipitation and temperature over the year. Water from the Athi River, Kenya had a fluoride content ranging from 0.3 to 1.2 ppm, the higher concentrations being associated with the dry seasons. The fluoride concentration in piped water from mountain rivers in Mourjes, Greece, ranged over the year between 1.3 to 2.0 ppm, the changes being apparently unrelated to rainfall. Marked variations in fluoride concentrations from 0.5 to over 3.5 ppm were observed in water from artesian wells in Assiros, Greece. In drinking waters from boreholes in Boennerup Strand, Denmark, fluoride concentrations ranged with time from 1.4 to 2.4 ppm, the variations being unrelated to climate or precipitation, while little variation in fluoride concentrations was found in water from boreholes in either Roedvig or Egens, Denmark. Water obtained from two sources of artificially fluoridated water supplies from Ireland showed considerable variations with time, although pooled samples indicated relatively constant levels over the year. The study indicates that the results of single fluoride ion measurement from any given source should not be taken as being a reliable indicator of fluoride exposure from drinking water.(ABSTRACT TRUNCATED AT 250 WORDS)