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Objectives: The presence of schistosomal eggs in the urine is a sufficient but not necessary condition for an individual to be diagnosed with urogenital schistosomiasis. The absence of eggs does not prove that a person is disease-free. Thus, when examining populations using egg occurrence, there is a real risk of underestimating the prevalence. The aim is to develop an easy to use model for improved prevalence estimates of urogenital schistosomiasis.

Design and methods: Urine samples were taken from 161 schoolchildren and 124 adults on three different days for each individual. The probands were recruited from two areas in northern Tanzania with varying prevalence of urogenital schistosomiasis. The presence of eggs by microscopy and haematuria by dipstick were recorded for each sample and the measurements combined using the discordance of the outcomes.

Result: As a consequence of applying the developed model, a substantial increase in the prevalence estimate was noted for groups displaying a low egg occurrence.

Conclusion: By using the biological relationship that exists between the presence of eggs and blood in urine of an infected individual, we provide a way of adjusting the prevalence estimates of urogenital schistosomiasis, using the observed prevalence of haematuria, in the absence of competing causes.

The thesis revolves around diagnosis and treatment of tungiasis (sand flea disease) and schistosomiasis haematobium. The causing parasites, Tunga penetrans and Schistosoma haematobium, both have the ability to penetrate intact skin.

Tungiasis is a neglected parasitic skin disease, prevalent in resource-poor communities in sub-Saharan Africa, South America and the Caribbean. Its global prevalence has never been properly assessed. The prevalence may be as high as 60 percent in resource-poor urban settings. Repeated infections result in disfigurement and mutilations foremost of the feet, eventually leading to impaired mobility. Schistosomiasis haematobium, or urogenital schistosomiasis, is prevalent above all in Africa with around 100 million infected individuals. It causes damage to internal organs and could lead to serious sequelae in the urogenital tract.

The aim is to examine aspects and prerequisites for control and elimination of the two diseases in an east African context. Even if both diseases are caused by a parasite and associated with poverty, they exhibit distinct differences for public health interventions, especially considering control and elimination.

The thesis contains a dialectic comparison of diagnoses and treatments problematising possibilities and hindrances for public health interventions in rural locations in Uganda, Kenya and Tanzania, from where the empirical data are collected in the four encompassing studies. Two deal with treatment of tungiasis, where the idea is to use silicon-based oils in order to suffocate the parasite. Rigorous clinical treatment trials on humans are so far lacking. The conclusion is that the tested substance works much better than current treatments. It is also shown that an efficient, yet parsimonious treatment procedure can be successful, even in resource-poor settings.

WHO promotes a dose-pole for determining the number of praziquantel tablets in mass treatment campaigns of schistosomiasis. An alternative dosage procedure is proposed to avoid side-effects and promote compliance. Since mass treatment campaigns currently target children and adults at risk in endemic areas, the choice of diagnostic method will have consequences. Prevailing parasitological methods for field surveys are not sensitive enough, especially where the prevalence is seemingly low. The suggested more sensitive diagnostic method, that detects the level of urogenital schistosomiasis in population groups, is a both affordable and manageable approach in resource-poor settings.

Is control or elimination possible for tungiasis and urogenital schistosomiasis? The conclusion is that elimination cannot be achieved without environmental interventions, use of repellants, vaccines and ultimately a fight against poverty. A multidisciplinary approach is needed to understand and sustainably resolve the problems. Important disciplines for this public health endeavour are epidemiology, sociology and ethics.

Background: Tungiasis (sand flea disease) is caused by the penetration of female sand fleas (Tunga penetrans, Siphonaptera) into the skin. It belongs to the neglected tropical diseases and is prevalent in South America, the Caribbean and sub-Saharan Africa. Tungiasis predominantly affects marginalized populations and resource-poor communities in both urban and rural areas. In the endemic areas, patients do not have access to an effective and safe treatment. A proof-of-principle study in rural Kenya has shown that the application of a two-component dimeticone (NYDA®) which is a mixture of two low viscosity silicone oils caused almost 80% of the embedded sand fleas to lose their viability within 7 days.

Methods: In this study we compared the efficacy of two distinct modes of application of NYDA®; one targeted application to the area where the parasite protrudes through the skin and one comprehensive application to the whole foot.

Results: Independent of the two modes of application, the dimeticone caused more than 95% of embedded sand fleas to lose all signs of viability within 7 days. The targeted application killed embedded sand fleas more rapidly compared to when the whole foot was covered. The proportion of viable lesions at day two were 7.0 versus 23.4% (p < 0.01) and at day five 3.9 versus 12.5% (p < 0.02).

Conclusions: Our findings suggest that the dimeticone could provide a safe and effective treatment for tungiasis in areas with difficult access to health care.

BACKGROUND: Clinical schistosomiasis in endemic countries is treated with a single dose of praziquantel per 40 mg/kg body weight. Treating according to weight, in resource-poor settings when thousands of doses are to be administered in mass treatment campaigns, is considered problematic. A calibrated dose-pole based on height was developed and is now used in mass treatment campaigns for determining the doses for schoolchildren. The dose-pole will generate dose errors since every child population contains individuals that are either short or tall for weight. The aim of this study is to explore whether the WHO praziquantel pole is a satisfactory dose instrument for mass treatment of S. haematobium.

METHODS: In 1996 and 2002, 1,694 children were surveyed in the Kilimanjaro Region, Tanzania. We compared doses given by weight to doses given by height using descriptive statistics and regression.

CONCLUSIONS AND INTERPRETATION: The WHO dose-pole for praziquantel is based on height of the patient; however, children with the same height will differ in weight. Our study shows that children with the same weight could qualify for up to four different dose levels based on their height. The largest variation of doses based on the WHO dose-pole will be found in children below 20 kg of bodyweight. Using bodyweight and tablet halves as the smallest tablet division unit to determine the doses of praziquantel, one only has to identify every 6th kilogram of bodyweight; the doses will then vary a lot less than when using the WHO dose-pole.

Tungiasis (sand flea disease) is a neglected tropical disease, prevalent in resource-poor communities in South America and sub-Saharan Africa. It is caused by an inflammatory response against penetrated female sand fleas (Tunga penetrans) embedded in the skin of the host. Although associated with debilitating acute and chronic morbidity, there is no proven effective drug treatment. By consequence patients attempt to remove embedded sand fleas with non-sterile sharp instruments, such as safety pins, a procedure that represents a health threat by itself. In this proof-of-principle study we compared the topical application of a mixture of two dimeticones of low viscosity (NYDA) to the topical application of a 0.05% solution of KMnO4 in 47 school children in an endemic area in rural Kenya. The efficacy of the treatment was assessed during a follow up period of seven days using viability signs of the embedded parasites, alterations in the natural development of lesion morphology and the degree of local inflammation as outcome measures. Seven days after treatment, in the dimeticone group 78% (95% CI 67-86%) of the parasites had lost all signs of viability as compared to 39% (95% CI 28-52%) in the KMnO4 group (p<0.001). In the dimeticone group 90% (95% CI 80-95%) of the penetrated sand fleas showed an abnormal development already after 5 days, compared to 53% (95% CI 40-66%; p<0.001) in the KMnO4 group. Seven days after treatment, signs of local skin inflammation had significantly decreased in the dimeticone group (p<0.001). This study identified the topical application of dimeticones of low viscosity (NYDA) as an effective means to kill embedded sand fleas. In view of the efficacy and safety of the topical treatment with dimeticone, the mechanical extraction of embedded sand fleas using hazardous instruments is no longer warranted.