Animal fascioliasis is a liver disease of ruminants which has been described in many parts of the world including a few African countries [1–5, 7–12]. Recently, human fascioliasis has also been described as a zoonosis acquired from domestic animals. Human fascioliasis is acquired by the ingestion of Fasciola metacercariae encysted on vegetables or in drinking water. The distribution of human fascioliasis has recently been reported in four African countries including; Egypt, Ethiopia, Cameroon and South Africa. In most rural African settings, domestic animals including cattle, sheep and goats are part of agricultural activities, for provision of meat, milk and hide. Similarly, in these settings, vegetables including lettuce, radishes, corncob, alfalfa, and amaranths are cultivated to provide vegetable food source. Rural and semi - rural African settings readily provide the environment suitable for the completion of the life cycle of animal fascioliasis, which includes infected animals that would release infective eggs into the environment and the subsequent development of cercariae within Lymnaea snails, up to development of metacercaria which encyst on vegetable leaves. When human and animal fascioliasis concur the transmission cycle of fascioliasis is amplified many fold.
The suburbs of Arusha city, where this study was conducted, provide a scenario described above for efficient transmission of animal fascioliasis to humans, i.e. the agricultural system in this area includes cattle, sheep and goats and vegetables are cultivated in abundance as an additional food source. Additionally, some of the inhabitants drink untreated water from natural streams.
In our case series, which involved 1460 persons over a 12 month period, 305 (21 %) were found to be infected with fascioliasis. Because Fasciola eggs are not detected during the acute infection, and because the disease has not been described before in Tanzania, it is likely that laboratory investigations intended to detect intestinal worm infections in stool would have missed the recognition of Fasciola eggs in the stool samples.
We also observed two distinct egg sizes on microscopic examination: large ovoid eggs mean 194.5 by 130.5 μm and smaller oval eggs mean 138.8 by 101 μm, which correspond to reported egg size ranges for fasciolid eggs [1, 5]. The eggs recovered in this study are notably wider than reported egg size ranges for both F. hepatica and F. gigantica from other reports [1, 21]. This could be due to preservation in 5 % formalin in saline (for 1 week) before measurements were taken. It could also be a slight variation is egg size for this region as no previous studies have reported the infection characteristics among humans, and egg sizes have been noted to vary according to geographical location [1, 5, 21]. The presence of two distinct egg sizes, sometimes recovered from stool samples of the same patient also point to possible co-infection by the different species, and may further insinuate the possibility of hybrid species [21, 22]. Although we were unable to speciate the causative parasite as being Fasciola hepatica or F. gigantica in this particular clinical study, other veterinary and malacology studies conducted in the region and East Africa in general [19, 22, 23] have shown the presence of both species. The climatic and demographic distribution of the two species has been highlighted [21–23] and of note is the presence of both species in certain geographical regions, subject to altitude and fresh water availability. Because Fasciola eggs have an inconspicuous operculum, it is difficult for the unsuspecting investigator to identify them with certainty, even in well documented endemic regions [1–3, 5–8].
Triclabendazole is the drug of choice for the treatment of both animal and human fascioliasis as noted in other studies [12, 18]. In this study, three patients were cleared of HF by a single dose of this drug. Use of Nitazoxanide did not clear all patients treated. This finding was consistent with some earlier reports.
This study has shown that more females than males are infected with HF and that fascioliasis is quite often associated with children below 12 years in both sexes. This finding is in agreement with what has been previously reported about the epidemiology of HF in some African and tropical countries [4, 6, 8–11]. The reasons for sex and age bias for HF could be because, at least in our settings, young girls and boys are culturally engaged as drawers of domestic water for house hold use. This practice would expose them more frequently to infection with HF than would adults. At TotalCare Medical Centre, records also indicated that there were more women and young children who visited the health centre than adult males.
Laboratory investigations including bilirubin levels indicated elevated serum and urinary bilirubin which is in agreement with findings by other studies on HF [7, 24]. Examination of blood films showed that most patients had marked eosinophilia, which is also of value in the diagnosis of HF during the acute phase of the disease . Clinically, fascioliasis patients present with fever and malaise, urticaria and swelling of lips during the acute stage of disease. In this study, pain at the upper right abdominal quadrant was a common clinical finding in most of the patients whose stools were found positive for Fasciola eggs. Pruritis was also reported by some of the patients and swelling of the lips was also seen. The latter three findings have also been described by other studies  as common findings associated with HF in the chronic, patent phase of the disease.