Ecological and parasitological studies were conducted in four agrarian districts (Butalawa, Dalili, Kosawa, Sarkin Kura) of Kura Local Government Area of Kano State, Nigeria to determine species composition, abundance and natural infection of molluscs by parasitic trematodes in rice field ecosystems; as well as the prevalence and intensity of urinary schistosomiasis among rice farmers. Manual prospections for molluscs diversity were conducted and physicochemical conditions of their microhabitats in rice fields were determined in situ using HANNA (HI98129) multiparameter metre. A total of 1959 specimens of five species of molluscs were obtained from the rice fields, which included 39(1.99%) Bellamya crawshayi, 307(15.67%) Biomphalaria pfeifferi, 548(27.97%) Bulinusglobosus, 95(4.85%) Lymnaeanatalensis, and 970(49.52%) Melanoidesmaculata.Only four (0.73%), of the B.globosus shed cercariae of trematode, giving snail infection rate of 0.20%.Bellamyacrawshayi and L.natalensis occurred at low percentages and were found only in two of the four districts; but B. pfeifferi, B. globosus and M. maculata occu rred in all the four districts. Physicochemical conditions of the rice fields where the molluscs species occurred in water were pH (8.24-9.70), TDS (30.00-39.00ppm), EC (64-77┬Ás/cm) and temperature (24.00-27.50oC). The species specific physicochemical conditions of molluscs ̓micro habitats did not differ significantly (P > 0.05). District specific physicochemical parameters of rice fields ̓water differ significantly (P < 0.05) amongst the four districts. Very high positive and significant (r = 0.99; P < 0.05) correlation existed among the abundance of and both pH and temperature of rice fields ̓water in Dalili district ; and among B. pfeifferi abundance and temperature of rice fields‟ water in Kosawa district. An overall prevalence of urinary schistosomiasis of 211/420 (50.24%) was obtained in rice farmers in the study area; this ranged from 44/105 (41.90%) at Butalawa district to 63/105 (60%) at Sarkin Kura district. Prevalence of urinary schistosomiasis in the female rice farmers was 48/111 (43.24%), and was 163/309(52.75%) in the male rice farmers. Intensities of urinary schistosomiasis ranged significantly (P < 0.05) from 5.02(eggs per 10mL urine) in Butalawa district to 51.84 (eggs per 10mL urine) in Dalili district. Male rice farmers had significantly (P < 0.05) higher intensities of infection than their female counterpart at both Dalili and Sarkin Kura, but gender based differences in intensities were not significant (P > 0.05) at both Butalawa and Kosawa districts. A large majority (77.25%) of the rice farmers examined had light intensity of infection with 0-30eggs per 10mL urine. Acquisition of urinary schistosomiasis by the rice farmers was positively (OR > 1) but insignificantly (Lower CI < 1) associated with the male gender. Rice farmers that were 10 years of age and younger had the highest prevalence of 78.05% while those aged 41years and older were not infected by Schistosoma haematobium. Prevalence of urinary schistosomiasis in the rice farmers declined significantly (P < 0.05) with increasing age (declining from 78.05% in those aged 1-10years, to 19.35% in 31-40years group and nil in those aged 41years and older). Such epidemiologic risk factors as male gender, swimming and washing water contact activities, drinking from stream water, urination and or defaecation on rice farms, non-use of protective wears and lack of disease awareness were associated with the prevalence and transmission of urinary schistosomiasis among the rice farmers.


1.1       Background of the Study

Urinary schistosomiasis is a chronic human debilitating disease, caused by infection with the trematode Schistosoma haematobium (Ahmad et al.,2014).Schistosoma haematobium was first described by a German Pathologist, Theodore Maximilian Bilharz in 1851 during an autopsy on an Egyptian patient; and the common name for all forms of schistosomiasis is „bilharziasis‟ in honour of his discovery (Okpala, 2010).Schistosome infections caused mainly bySchistosoma haematobium were estimated to occur in Africa, accounting for more than 97% of the number of infections worldwide (Steinmannet al., 2006). Nigeria is one of the countries highly endemic for urinary schistosomiasis, where the disease has been unsystematically reported and large areas remain where the disease status is unknown (Anosike et al., 2001).While at least 258 million requires preventive treatment forschistosomiasis in 2014, more than 61.6million people were treated for schistosomiasis in 2014 (WHO, 2016). The transmission of Schistosomiasis has been reported for 78 countries, treatment is required in only 52 endemic countries with moderate to high transmissions (WHO, 2016).

The disease is characterized by haematuria in 50% of cases, inflammation of the bladder, increased frequency of passing urine (micturation) and reduced bladder capacity sometimes leading to death (Usaini et al., 2015).The urethral lumen becomes greatly closed, penis or scrotum may develop obstruction and fistulae may tear through the skin (Usaini etal., 2015).The intermediate hosts of schistosomes in Africa are freshwater pulmonate snails, which belong to the Planorbidae family. The snail hosts belong to two genera, namely Biomphalaria, hostfor S. mansoni, and Bulinus, host for S. haematobium and S. intercalatum (Ngeleet al.,
2012).Freshwater snails act as intermediate hosts, after being infected by schistosome “miracidia”(larvae thatemerge by the hatching of eggs found in human excreta or urine, deposited in the water), following developmental stages in the snails, cercariae are produced which are released into the body of water frequented by humans. As a result of contact with these cerceriae during water-based activities, the cerceriae penetrates the skin of the susceptible human hosts. The disease may cause damage to various tissues (the bladder, liver or the intestines) depending on the species. There are 16 different known species of Schistosoma, of which five are infective to man S. mansoni, S. haematobium, S. intercalatum,S. japonicum and S. mekongi. The species differ according to their snail intermediate hosts, egg morphology,final location of the adult worms in the human body, resulting symptoms, and their geographical distribution (Boelee and Madsen,2006).

The most common forms of the disease in Africa are: intestinal schistosomiasis, which is caused byS. mansoni; and urinary schistosomiasis, which is caused by S. haematobium.In sub-Saharan Africa, approximately 393 million people are at risk of infection from S. mansoni, ofwhich 54 million are infected. Those numbers for S. haematobium are estimated to be as high as436 million at risk, of which 112 million are infected (Van der Werf et al.,2003). Schistosomiasis is widespread, ranking second to malaria in term of socio-economic and public health significance in tropical and sub-tropical areas (Usaini et al., 2015). Up to 60.99% of rice farmers had urinary schistosomiasis in a focal survey within Kaduna State, Nigeria (Oguike, 2015).

The transmission of schistosomiasis is associated with water development projects such as dams for irrigation systems and fishing, as the snail intermediate hosts of the parasites breed in them and they encourage human water contact (Jeffrey et al., 2004)

Kura Local Government lies in the Sudan Savanna vegetation zone isthe most extensively irrigated Local Government Area in Kano State, Nigeria due to the introduction of irrigation system in the area. As an agricultural town Kura is known for the production of food and vegetable crops both during dry and rainy season. The dry seasons mostly start from October and ends in April, while the rainy season begins from May and ends in September; with an average annual rainfall of 134.4mm. The inhabitantsof the Local Government Area are 80% farmers who are engaged in mixed farming in both the seasons. Some of the crops produced in the area are rice, wheat, maize, millet, Guinea-corn, beans and tomatoes, of which rice is highly cultivated than other crops. Thus with the population of this community who are mostly farmers, this is a risk factor of schistosomiasis, which is commonly known as TSARGIYA in this community.Various forms of water contact activities such as swimming, playing,farming, laundryand bathing have been found to enhance the transmission of schistosomiasis (Ahmad et al., 2014). These activities were amongst those reported to be responsible for the transmission of the disease at RuwanSanyi dam site at Malumfashi in Northern Nigeria (Ahmad et al., 2014). In this study, boys of less than 21 years of age were found to account for more than 79% of the infected individuals (Bichi et al ., 2003). Also many such cases were reported in areas at close proximity to contaminated waters among this age group in some parts of Kano State Nigeria (Abdullahi, 2009; Ekpo et al., 2010).

1.2       Statement of the Research Problem.

Ecology of snails in rice field habitats is poorly understood in Nigeria despite the association of specific gastropod hosts of Schistosoma species with these habitats (Oguike, 2015).

Local rice production has received governmental impetus in Nigeria but the potential health risk and disease burden associated with rice farming are largely ignored.

Schistosomiasis is strongly associated with agrarian occupation but its prevalence and intensity amongst rice farmers in Nigeria are poorly investigated (Anosike et al.,2006; Etim et al., 2012; Oguike, 2015).

1.3       Justification

The Nigerian rice revolution can only succeed with healthy rice farmers and when the health challenges of productive farmers are assessed, appreciated and adequately tackled especially with the elimination of schistosomiasis risks.

Assessment of urinary schistosomiasis prevalence and intensity among rice farmers and snails‟ occurrence and infectivity with Schistosoma are important indices of water contact risks (Opisa et al.,2011).

Integrated schistosomiasis control is attainable through the strengthening of disease surveillance by monitoring of potential snail habitats and human cases (Li et al., 2007).

1.4       Aim of the Study

To conduct a malacological survey of rice fields and parasitological screening of rice farmers for urinary schistosomiasis.

1.5       Objectives of the study 
To determine:

i. Species composition, abundance and distribution of snail species in rice fields in Kura Local Government Area.

ii. The rate of cerceriae infection in snail species in rice fields in Kura Local Government Area.

iii. Physicochemical parameters of rice fields water in relation to snail occurrence in Kura Local Government Area.

iv. Distribution, prevalence and intensity of urinary schistosomiasis among rice farmers in some districts in Kura Local Government Area.

1.6 Research Hypotheses 
i. Snail species are neither present, abundant nor distributed in rice fields in Kura Local Government Area.

ii. Snail species are not infected by cerceriae in rice fields in Kura Local Government Area.

iii. Physico-chemical parameters of rice field water have no significant relationship with snail occurrence in Kura Local Government Area.

iv. Distribution, prevalence and intensity of urinary schistosomiasis among rice farmers in districts inKura Local Govermnent Area are low.

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