The effects of diabetes clubs on peer-support, disclosure of diabetes status, and sources of information regarding diabetes management: results of a pilot-intervention in rural Vietnam.

OBJECTIVES: To measure the effects of diabetes clubs on peer support, disclosure of diabetes status, and the source of information regarding the management of diabetes among persons living with type-2 diabetes (T2D) in rural Vietnam. STUDY DESIGN: A pre- and post-pilot intervention study was carried out in Thai Binh Province, Vietnam (n = 222). RESULTS: Post-intervention, 57.7 % reported using experiences shared by other persons with T2D during the diabetes club sessions. Compared to pre-intervention, there was an increase in the proportion of persons with T2D who disclosed their diabetes status to friends and/or community members (an increase of 15.3 and 13.8 percentage points, respectively). The proportion of persons who reported gathering their own information regarding diabetes management without any support from others decreased from 15.7 % to 6.3 %. Those who reported a relative inside their home or a relative outside their household as their primary source of T2D-relevant information increased from 10.8 % to 18.6 % and from 2.7 % to 9.5 %, respectively. Persons who mentioned that they did not have a need for further support for their diabetes care increased from 18.5 % to 32.0 %. Specific support regarding diabetes-related knowledge received from family members, friends, and/or community members increased from 27.5 % to 62.2 % CONCLUSIONS: These findings suggest a promising potential for the implementation of diabetes clubs to enhance diabetes-relevant knowledge and the quality of self-management among persons living with T2D diabetes in rural areas of Vietnam.

Postpartum depression and child growth in Tanzania: a cohort study.

OBJECTIVE: To examine the association between postpartum depression and child growth in a Tanzanian birth cohort. DESIGN: Prospective cohort study. SETTING: Moshi, Tanzania. POPULATION: Pregnant women over the age of 18 who sought antenatal care at two health clinics in Moshi, and the children they were pregnant with, were assessed for inclusion in this study. METHODS: The women were interviewed twice during pregnancy and three times after birth, the final follow up taking place 2-3 years postpartum. Signs of postpartum depression were assessed approximately 40 days postpartum with the Edinburgh Postnatal Depression Scale. MAIN OUTCOME MEASURES: Child growth was assessed with anthropometric measurements at 2-3 years of age and expressed as mean z-scores. RESULTS: In all, 1128 mother-child pairs were followed throughout the duration of the study. In total, 12.2% of the mothers showed signs of postpartum depression. Adjusted mean height-for-age z-score (HAZ) was significantly lower at 2-3 years follow up for children of mothers with postpartum depression than for children of mothers without (difference in HAZ: -0.32, 95% CI-0.49 to -0.15). Adjusted mean weight-for-height z-score (WHZ) was significantly increased for the children exposed to postpartum depression (difference in WHZ: 0.21, 95% CI 0.02-0.40), whereas there was no significant difference in adjusted weight-for-age z-score (WAZ; difference in WAZ: -0.04, 95% CI -0.20 to 0.12). CONCLUSIONS: We found that postpartum depressive symptoms predicted decreased linear height in children at 2-3 years of age and slightly increased weight-for-height. TWEETABLE ABSTRACT: Postpartum depression in Tanzanian mothers is associated with impaired child growth at 2-3 years of age.

Re-assessing community-directed treatment: evidence from Mazabuka District, Zambia.

Cross-sectional surveys with carers, health workers, community drug distributors (CDDs) and neighbourhood health committees were conducted to identify factors associated with utilization of community-directed treatment (ComDT) of soil-transmitted helminths in children aged 12-59 months in Mazabuka district, Zambia. The surveys took place in December 2006 and December 2007. In addition child treatment records were reviewed. The factors that were found to be significantly associated (p < 0.05) with treatment of children by the CDDs were: (1) the perception of soil-transmitted helminth infections as having significant health importance, (2) the community-based decision to launch and subsequently implement ComDT, (3) the use of the door-to-door method of drug distribution, (4) CDDs being visited by a supervisor, (5) CDDs receiving assistance in mobilizing community members for treatment, (6) CDDs having access to a bicycle and (7) CDDs having received assistance in collecting drugs from the health centre. Despite the effectiveness of ComDT in raising treatment coverage there are factors in the implementation process that will still affect whether children and their carers utilize the ComDT approach. Identification and understanding of these factors is paramount to achieving the desired levels of utilization of such interventions.

Socio-demographic factors associated with treatment against soil-transmitted helminth infections in children aged 12-59 months using the health facility approach alone or combined with a community-directed approach in a rural area of Zambia.

A health facility-based (HF) approach to delivering anthelminthic drugs to children aged 12-59 months in Zambia was compared with an approach where community-directed treatment (ComDT) was added to the HF approach (HF+ComDT). This paper reports on the socio-demographic factors associated with treatment coverage in the HF+ComDT and HF areas after 18 months of implementation. Data were collected by interviewing 288 and 378 caretakers of children aged 12-59 months in the HF+ComDT and HF areas, respectively. Bivariate and multivariate logistic regression analyses were used for data analysis. Statistically significant predictors of a child being treated were: a child coming from the HF+ComDT area, being 12-36 months old, the family having lived in the area for >20 years, coming from a household with only one under-five child and living ≤3 km from the health facility. It is concluded that socio-demographic factors are of public health relevance and affect treatment coverage in both the HF+ComDT and the HF approaches. The implementation and strengthening of interventions like ComDT that bring treatment closer to households will enable more children to have access to treatment.

Bancroftian filariasis in Tanzania: specific antibody responses in relation to long-term observations on microfilaremia.

Following a 16-year clinical and parasitologic follow-up survey for Bancroftian filariasis in three endemic communities in northeastern Tanzania, serum antibody responses were analyzed in selected individuals in relation to the long-term observations on microfilaremia. Comparison of responses in three categories of adults (microfilaria [mf] positive at both surveys, mf positive at first but mf negative at the second survey, and mf negative at both surveys, respectively) indicated no significant differences between the mean levels of filarial-specific IgG1, IgG2, IgG3, IgG4, or IgE (measured by ELISA). However, specific IgG2 to the sheath of Wuchereria bancrofti mf (measured by an indirect fluorescence antibody test [IFAT]) was detected only in the third category. Comparison of responses in two categories of children born around the time of the first survey (to mf-positive and mf-negative mothers, respectively) showed a significantly higher mean level of filarial-specific IgG4 in the first than in the latter category, whereas the mean levels of filarial-specific IgG1, IgG2, IgG3, and IgE, and the prevalences of IgG2 IFAT positivity were similar. The overall prevalence of IgG2 IFAT positivity was considerably higher in the child study population (45.5%) than in the adult study population (16.7%). In both populations, however, a clear association between IgG2 IFAT positivity and a negative microfilarial status and negative specific circulating antigen status was seen. The study suggests that specific anti-sheath-antibodies are associated with an immunologic resistance mechanism that in the endemic community is expressed with highest prevalence in young individuals before development of patent microfilaremia.

Selective diethylcarbamazine chemotherapy for control of Bancroftian filariasis in two communities of Tanzania: compared efficacy of a standard dose treatment and two semi-annual single dose treatments.

The efficacy of two strategies for control of Bancroftian filariasis using selective rather than community-wide diethylcarbamazine (DEC) chemotherapy was evaluated and compared in two endemic communities of north-eastern Tanzania, with pretreatment microfilariae (mf) prevalences of 22% and 38%, and geometric mean intensities (GMIs) of 668 mf/ml and 735 mf/ml of blood. All mf-positive cases in the first community were offered treatment with 6 mg of DEC/kg of body weight a day for 12 days (group 1), and those in the second community were offered treatment with two doses of 6 mg of DEC/kg of body weight at an interval of six months (group 2). The effect of treatment was followed both among those treated and at the community level. In treated individuals, there was a rapid decrease in the mf load that was significantly greater among those receiving the 12-day standard dose. One year after the start of treatment, the mf clearance rates were 59% and 39% and the GMIs were reduced by 99% and 97% among treated individuals in groups 1 and 2, respectively. However, at the community level, the mf prevalences were 16.3% and 27.9% (reduced by 27% and 26%) and the GMIs were 129 mf/ml and 224 mf/ml (reduced by 81% and 70%) one year after the start of treatment with the two regimens, respectively, suggesting that transmission continued at a significant level in the villages after treatment. The limitations of selective chemotherapy are discussed, and it is argued that strategies based on mass DEC chemotherapy would be more effective in reducing the microfilarial load in the community and thereby in reducing transmission.

Long-term effect of mass diethylcarbamazine chemotherapy on bancroftian filariasis, results at four years after start of treatment.

The long-term effect of 4 strategies for control of bancroftian filariasis using mass diethylcarbamazine (DEC) chemotherapy was assessed and compared in 4 endemic communities in Tanzania over a period of 4 years. The strategies were the standard 12 d treatment (strategy I), semi-annual single dose treatment (strategy II), monthly low dose treatment (strategy III), and DEC-medicated salt treatment (strategy IV). Treatment was given only during the first year. All strategies resulted in considerable reductions in microfilaraemia, with maximum effects occurring 1-2 years after start of treatment. At 2 years, the greatest reductions were seen for strategies III and IV, followed by strategy II and finally strategy I. The overall performance of the 4 strategies evaluated over the 4 years period followed the same sequence. Between the 2 years and 4 years follow-up surveys, a significant increase in microfilarial (mf) burden occurred in all 4 communities, but the mf geometric mean intensities (GMI) remained low. Thus, in individuals who were microfilaraemic before treatment, the rates of microfilaraemia were 66%, 44%, 34% and 43%, and the mf GMIs were 6.8%, 3.3%, 0.5% and 0.7%, of pre-treatment level, 4 years after start of treatment with strategies I, II, III and IV, respectively. Most individuals who developed microfilaraemia between the 2 years and 4 years follow-up surveys had been microfilaraemic before the start of treatment. Hence, the rate of development of microfilaraemia was much higher (18 times on average in the 4 communities) among those who were microfilaraemic before treatment than among those who were amicrofilaraemic. The long-lasting effect of treatment adds a promising potential to the use of mass DEC chemotherapy for the control of bancroftian filariasis.

Tolerance to diethylcarbamazine-medicated salt in individuals infected with Onchocerca volvulus.

The tolerance of Onchocerca volvulus-infected individuals to diethylcarbamazine (DEC)-medicated salt (0.33% w/w) was assessed in 1996 in Tanzania in a double-blind placebo-controlled hospital-based trial involving 4 groups, each of 10 adult males. Groups I and II had O. volvulus microfilariae (mf) only, group III had both O. volvulus and Wuchereria bancrofti mf, and group IV had W. bancrofti mf only. Groups I, III and IV received DEC-medicated salt, whereas group II was a control to group I and received normal cooking salt. Medication was given for 10 days. The most pronounced adverse reactions in groups I and III were mild-to-moderate itching and rash, beginning after 3-4 days and lasting for the remaining medication period. The reactions did not interfere with normal daily activities. By 20 days after the end of medication, adverse reactions had disappeared in all individuals. The low daily dose of DEC had no significant effect on the O. volvulus pre-medication mf geometric mean intensities (GMIs). In contrast, the medication significantly reduced the pre-medication W. bancrofti mf GMIs. The prospects for using DEC-medicated salt for control of bancroftian filariasis in areas where incidental infections with O. volvulus occur are discussed.

Mass diethylcarbamazine chemotherapy for control of bancroftian filariasis: comparative efficacy of standard treatment and two semi-annual single-dose treatments.

The efficacy of 2 strategies for control of bancroftian filariasis using mass diethylcarbamazine (DEC) chemotherapy was evaluated and compared in 2 endemic communities in Tanzania with pre-treatment microfilarial (mf) prevalences of 28.5% and 17.7%, and mf geometric mean intensities (GMI) of 588 mf/mL and 251 mf/mL, respectively. All individuals in the first community were offered DEC treatment with 6 mg/kg body weight given daily for 12 d (standard treatment). The second community was offered DEC treatment with 2 single doses of 6 mg/kg body weight given with an interval of 6 months (semi-annual single-dose treatment). Among those who were microfilaraemic before treatment, the mf clearance rates were 51.2% and 36.0%, and the mf GMIs were reduced by 98.6% and 92.2% one year after the start of the standard and the semi-annual regimens, respectively. At community level, the standard strategy and the semi-annual strategy reduced the mf prevalences to 15.1% and 11.6% (reductions of 47.0% and 34.5%) and the mf GMIs to 112 mf/mL and 102 mf/mL (reductions of 81.0% and 59.4%, respectively) one year after start of treatment. Both regimens resulted in remarkable improvements in small hydroceles among males presenting this condition before treatment. The lower efficacy of the semi-annual single-dose treatment in relation to the standard treatment in reducing microfilaraemias might be compensated for by continuing semi-annual treatments for a slightly longer period of time. Considering that the semi-annual treatment is easy to administer and more acceptable to the treated individuals, it may in the long run be a more feasible strategy for mass DEC chemotherapy than the standard treatment.

Mass diethylcarbamazine chemotherapy for control of bancroftian filariasis through community participation: comparative efficacy of a low monthly dose and medicated salt.

The efficacy of 2 strategies for the control of bancroftian filariasis using diethylcarbamazine (DEC) mass chemotherapy delivered through community participation was evaluated and compared in 2 endemic communities in Tanzania with pre-treatment microfilarial (mf) prevalences of 34.7% and 31.0%, and mf geometric mean intensities (GMI) of 1122 mf/mL and 933 mf/mL, respectively. In the first community, all individuals aged > or = 1 year were offered treatment for one year with a low monthly dose (50 mg DEC to children aged < 15 years and 100 mg DEC to adults aged > or = 15 years; given independently of body weight), and in the second community all households were offered 0.33% w/w DEC-medicated cooking salt for one year. Both treatment strategies resulted in dramatic reductions in the mf loads. Among those microfilaraemic before treatment, the low monthly dose and the DEC-medicated salt gave mf clearance rates of 55.3% and 92.1%, respectively, and the pre-treatment mf GMIs were reduced by 99.4% and 99.9%, respectively, one year after starting treatment. At community level, the mf prevalences were reduced to 15.8% and 2.4% (reductions of 54.5% and 92.3%) and the mf GMIs were reduced to 100 mf/mL and 32 mf/mL (reductions of 91.1% and 96.6%), one year after starting treatment with the low monthly dose and DEC-medicated salt respectively. Males with hydrocele before treatment improved remarkably one year after the start of treatment. Since both strategies were simple to administer and well accepted by the communities, they appear highly feasible for integration into large scale control programmes based on community participation.

Mass DEC chemotherapy for control of bancroftian filariasis: comparative efficacy of four strategies two years after start of treatment.

The efficacy of 4 strategies for control of bancroftian filariasis using mass diethylcarbamazine (DEC) chemotherapy was evaluated and compared in 4 endemic communities in Tanzania 2 years after the start of treatment. The strategies used were the standard 12 d treatment (strategy I), a semi-annual single dose treatment (strategy II), a monthly low dose treatment (strategy III), and DEC medicated salt (strategy IV). Treatment took place during the first study year, and no treatment was given during the second year. Among individuals who were microfilaraemic before treatment, the microfilaria (mf) clearance rates were 41.5%, 75.0%, 84.0% and 89.1%, and the pre-treatment mf geometric mean intensities (GMIs) were reduced by 97.1%, 98.9%, 99.8% and 99.8%, for strategies I, II, III and IV, respectively, 2 years after starting treatment. Statistical analysis indicated that strategies III and IV were equally effective, and superior in clearing microfilaraemias and in reducing mf GMIs compared to strategies I and II; strategy II was significantly more effective than strategy I. The rate of occurrence of new cases of microfilaraemia among individuals who were amicrofilaraemic during the pre-treatment surveys was negligible over the study period in all communities. In all the communities combined, 66.6% of males presenting hydrocele before treatment, and 61.5% of individuals presenting elephantiasis before treatment, showed improvements in these conditions 2 years after the start of treatment, either as a reduction in size or complete disappearance.

Bancroftian filariasis: the pattern of microfilaraemia and clinical manifestations in three endemic communities of Northeastern Tanzania.

Individuals from three villages in northeastern Tanzania, located 40 km inland from the Indian Ocean coast, were surveyed for parasitological and clinical evidence of bancroftian filariasis. Microfilarial (mf) prevalences ranged from 22.2 to 37.6%, and mf geometric mean intensities (GMI) ranged from 546 to 735 mf/ml blood, in the three villages. Microfilaraemia was rare in children below five years. The mf prevalences increased with age, reaching from 35.9 to 49.2% in individuals aged 45 years and above. No association between mf GMI and age was observed in any of the villages. Hydrocele was the most common chronic clinical manifestation, with prevalences ranging from 14.5 to 21.3% for all males, and from 52.9 to 62.1% for males aged 45 years and above. From 0.6 to 3.3% of the inhabitants in the three villages had elephantiasis, which most often affected the legs. Microfilaraemia was common in males with hydrocele, and in males of 45 years and above there was no significant difference in mf prevalence between males with (42.5%) and without (55.2%) hydrocele. In contrast, microfilariae were only detected in the blood from one of 18 individuals with elephantiasis. With respect to hydrocele, the present results do not support recently forwarded hypotheses assuming a general negative relationship between microfilaraemia and chronic clinical manifestations in bancroftian filariasis.

A review of the present status of lymphatic filariasis in Vietnam.

Establishing the current status of an infectious disease forms the starting point of any attempt at parasite control. Although data on the prevalence and distribution of lymphatic filariasis exist for Vietnam from the early 1900s, the present situation regarding the disease is less well-known. Here, we review the results of recent surveys conducted by the Institute of Malariology, Parasitology and Entomology, Hanoi, to update the existing information on filariasis epidemiology and distribution for this country. The present results are from surveys carried out on some 135,000 individuals in 24 provinces of Vietnam. The highest prevalences of microfilaraemia (primarily Brugia malayi ) are observed in lowland areas of the Red River Delta and in Quang-binh Province where the survey results show microfilaraemia (mf) prevalences in the range of 0.9-5.5%. The most common type of chronic clinical manifestation is shown to be leg elephantiasis. A significant finding is that an overall decrease in mf prevalence was observed to occur in five communities which were surveyed twice over an 11-21-year period, even though no interventions were carried out between the two surveys. The changes are probably caused by environmental changes, such as increased standards of housing and drainage. Studies on the effect of selective chemotherapy and mass chemotherapy using diethylcarbamazine showed reductions in community mf prevalences of 69 and 72-88%, respectively. Furthermore, cats do not appear to represent significant reservoirs of infection. These findings of geographical restriction of infection, effective and well-tolerated drug therapy, low significance of animal reservoirs, together with the existence of an effective national health network, suggest a good prognosis for the control of filariasis in this country.

Use of Complementary and Alternative Medicine among People with Multiple Sclerosis in the Nordic Countries.

Aims. The aim of the study was to describe and compare (1) the types and prevalence of complementary and alternative medicine (CAM) treatments used among individuals with multiple sclerosis (MS) in the Nordic countries; (2) the types of conventional treatments besides disease-modifying medicine for MS that were used in combination with CAM treatments; (3) the types of symptoms/health issues addressed by use of CAM treatments. Methods. An internet-based questionnaire was used to collect data from 6455 members of the five Nordic MS societies. The response rates varied from 50.9% in Norway to 61.5% in Iceland. Results. A large range of CAM treatments were reported to be in use in all five Nordic countries. Supplements of vitamins and minerals, supplements of oils, special diet, acupuncture, and herbal medicine were among the CAM treatment modalities most commonly used. The prevalence of the overall use of CAM treatments within the last twelve months varied from 46.0% in Sweden to 58.9% in Iceland. CAM treatments were most often used in combination with conventional treatments. The conventional treatments that were most often combined with CAM treatment were prescription medication, physical therapy, and over-the-counter (OTC) medications. The proportion of CAM users who reported exclusive use of CAM (defined as use of no conventional treatments besides disease-modifying medicine for MS) varied from 9.5% in Finland to 18.4% in Norway. In all five Nordic countries, CAM treatments were most commonly used for nonspecific/preventative purposes such as strengthening the body in general, improving the body's muscle strength, and improving well-being. CAM treatments were less often used for the purpose of improving specific symptoms such as body pain, problems with balance, and fatigue/lack of energy. Conclusions. A large range of CAM treatments were used by individuals with MS in all Nordic countries. The most commonly reported rationale for CAM treatment use focused on improving the general state of health. The overall pattern of CAM treatment use was similar across the five countries.

Bancroftian filariasis: house-to-house variation in the vectors and transmission -- and the relationship to human infection -- in an endemic community of coastal Tanzania.

The house-to-house variation in Wuchereria bancrofti vector abundance and transmission intensity, and the relationship of these parameters to human infection, were investigated in an endemic community in coastal Tanzania. Vector mosquitoes were collected in light traps set up in 50 randomly selected households once weekly for 1 year. They were identified, dissected and checked for filarial larvae. Vector densities and transmission potentials varied markedly between households, both for all vectors combined and for the individual vector species (Anopheles gambiae s.1., An. funestus and Culex quinquefasciatus), even between households located close to each other. The variation in vector abundance was probably mainly attributable to differences in the distance to breeding sites, to specific household features likely to ease mosquito entry and hiding, and to the number of household inhabitants. Household annual biting rates (ABR) correlated positively with household annual transmission potentials (ATP), indicating that intense vector biting led to a high transmission intensity. Intriguingly, however, the human filarial-infection status (as indicated by microfilaraemia or circulating filarial antigenemia) did not differ significantly between households with relatively high and lower ABR or ATP. Possible reasons for this result include the long time required for W. bancrofti infection to establish in humans, human behaviour affecting exposure, the sharing of mosquito populations between households, and differential susceptibility of humans to infection. The marked heterogeneity in exposure between households, and the lack of immediate relationship between transmission and detectable human infection at household level, should be taken into account when considering the transmission pattern of lymphatic filariasis.

Bancroftian filariasis: patterns of vector abundance and transmission in two East African communities with different levels of endemicity.

Intensive monitoring of Wuchereria bancrofti vector abundance and transmission intensity was carried out in two communities, one with high-level endemicity for bancroftian filariasis (Masaika, Tanzania) and the other with low-level (Kingwede, Kenya), on the East African coast. Mosquitoes were collected in light traps, from 50 randomly selected households in each community, once weekly for 1 year. They were identified, dissected and checked for parity and filarial larvae. Anopheles gambiae s. l., An. funestus and Culex quinquefasciatus transmitted W. bancrofti in the two communities but the importance of each of these taxa differed between the communities and by season. The overall vector densities and transmission intensities were significantly higher in Masaika than in Kingwede (the annual biting rate by 3.7 times and the annual transmission potential by 14.6 times), primarily because of differences in the available breeding sites for the vectors and in the vectorial capacity of the predominant vector species. A marked seasonal variation in vector abundance and transmission potential contributed to the complex transmission pattern in the communities. Generally, these indices were higher during and shortly after the rainy seasons than at other times of the year. Considerable differences in W. bancrofti transmission were thus observed between communities within a relatively small geographical area (mainly because of environmentally-determined differences in vector habitats), and these were reflected in the marked differences in infection level in the human populations. The variation in vector abundance, vector composition and transmission intensity in the two communities is discussed in respect to its cause, its effects, and its significance to those attempting to control bancroftian filariasis.

Efficacy of DEC against Ascaris and hookworm infections in schoolchildren.

Diethylcarbamazine (DEC) is an important drug for treatment and control of lymphatic filariasis. To assess its possible effect on Ascaris and hookworm infections, we conducted a double-blind two-armed study with children in Tanzania. Twenty six Ascaris-infected children were given a single dose of DEC (6 mg/kg body weight) and 25 were given a placebo. Twenty children in the treatment group and eighteen controls were also infected with hookworms. One month after treatment the geometric mean intensity (GMI) of Ascaris egg output was reduced by 60.2% in the treatment group; two children (7.7%) had stopped excreting Ascaris eggs, and some Ascaris worms were also expelled. In hookworm-infected children in the treatment group, the geometric mean intensity of hookworm egg output was reduced by 6.7% 1 month after treatment. Neither for Ascaris nor for hookworm, however, was the observed reduction in egg output at 1 month after treatment statistically significant. The treatment efficacy of a single dose of DEC (6 mg/kg) in these infections therefore was low.

A 26-year follow-up of bancroftian filariasis in two communities in north-eastern Tanzania.

The results of surveys, for human bancroftian filariasis, carried out in 1975 and 1991 in endemic communities in north-eastern Tanzania have already been reported. In 2001, all consenting individuals from two of these communities (Tawalani and Kwale) were re-surveyed, and many of the individuals examined in the earlier surveys were re-identified. The findings revealed an extraordinarily static pattern of infection and disease over the 26 years of follow-up. By 2001, despite brief interventions introduced after the first two surveys, the community prevalences and mean intensities of microfilaraemia had almost returned to pre-treatment levels. The majority of re-identified individuals who had been found microfilaraemic in 1975 and 1991 were also microfilaraemic in 2001. Being found microfilaraemic in the first survey was a highly significant risk factor for being found microfilaraemic in the subsequent surveys. These observations strongly indicate that re-infection with Wuchereria bancrofti commonly takes place, and that, compared with an individual who has never been infected, an individual who has been infected in the past has a much higher chance of acquiring a new, detectable infection. As most of the re-identified individuals who were amicrofilaraemic in 2001 but microfilaraemic in one or both of the earlier surveys were still positive for circulating filarial antigens in 2001, it seems that, once an infection has been acquired, the chance of ever becoming free of infection is small. No relationship between past microfilaraemia and the development of chronic filariasis was observed but the number of clinical cases seen in 2001, among the re-identified individuals, was low. The significance of these findings to our understanding of the natural history of W. bancrofti infection is discussed.

Bancroftian filariasis: analysis of infection and disease in five endemic communities of north-eastern Tanzania.

Clinical and parasitological surveys for bancroftia filariasis were carried out in five endemic communities in north-eastern Tanzania, covering a population of 3086 individuals. High microfilarial (mf) prevalences (17.7%-34.7%) and mf geometric mean intensities (251-1122 microfilariae/ml) were observed in the communities. The mf prevalence generally increased with age, but often levelled out in the older age groups. Larger variability was observed in individual mf intensities and no clear association between mf geometric mean intensity and age or sex was seen. Hydrocele was the most common clinical manifestation (with a prevalence of 30.2%-40.0% in male subjects aged > or = 20 years) followed by leg elephantiasis (with a prevalence of 2.0%-6.8% in all subjects aged > or = 20 years). In four of the five communities, there was no significant difference in mf prevalence in males aged > or = 20 years between those with and without hydrocele. In all the communities, the mf geomtric mean intensities in microfilaraemic males with and without hydrocele were not significantly different. The present study therefore did not indicate any association between hydrocele in males (the most common type of chronic clinical manifestation seen) and presence or absence of microfilaraemia. In contrast, only two (4.4%) of the 45 subjects with leg elephantiasis were microfilaraemic. In children aged 1-15 years, mf prevalence was significantly higher among those with microfilaraemic mothers (18.0%) than among those with amicrofilaraemic mothers (7.9%). The children of microfilaraemic mothers were therefore at 2.3-fold higher risk of becoming microfilaraemic than the children of amicrofilaraemic mothers. No relationship between the mf prevalence of the children and the mf status of their fathers was observed.

A 16-year follow-up study on bancroftian filariasis in three communities of north-eastern Tanzania.

The results of a 16-year, parasitological and clinical, follow-up study on bancroftian filariasis in three villages in north-eastern Tanzania are reported and analysed with respect to the long-term development of microfilaraemia and disease. The study revealed an extraordinary static situation, both at the community level and at the individual level. No significant differences were observed in any of the three villages, with respect to total or age-specific prevalences of microfilaraemia, hydrocele in males aged > or = 20 years or leg elephantiasis in all subjects aged > or = 20 years, when the results from 1975 were compared with those from 1991. Overall, 542 of the subjects (37.2% of the total) examined in 1975 were re-identified and re-examined in 1991. Of those microfilaraeic in 1975, 81.9% were also microfilaraemic in 1991. Similarly, 81.3% of those amicrofilaraemic in 1975 were also amicrofilaraemic in 1991. Thus, most subjects had the same microfilarial (mf) status at both surveys. The low mf loss rate indicates that re-infection of microfilaraemic individuals commonly takes place, and results in repeated sequences of microfilaraemia in the same individuals. The rate of gain of microfilaraemia was independent of age, thus indicating no age-related change in the examined population's susceptibility to develop or sustain microfilaraemia. Individual differences in susceptibility to develop mirofilaraemia therefore appear to be innately determined, or to be acquired in pre-natal or early post-natal life. Neither the presence of hydrocele in 1991, nor the development of new cases of hydrocele over the 16-year period were related to the mf status in 1975 or 1991, and no association between microfilaraemia and this chronic clinical manifestation was observed. The association between leg elephantiasis and mf status could not be analysed because of the small sample size.