Assessing S. mansoni prevalence in Biomphalaria snails in the Gombe ecosystem of western Tanzania: the importance of DNA sequence data for clarifying species identification

Table 1 The numbers of snails sampled from the Gombe ecosystem and analysed for trematode infections by cercarial shedding and PCR. Infection prevalence is expressed as percent of snails screened; also indicated is the prevalence of another trematode (family Derogenidae), with a 1000 bp PCR product

Village^a	No. of snails sampled	Prevalence S. mansoni (shedding)^b	No. of snails screened (PCR)^c	Prevalence (500 bp band)^c	Prevalence (1000 bp band)
Bugamba	23	0	23	34.8	26.1
Gombe	46	0	32	0.08	0
Kigoma	30	26.7	30	55.6	0
Kiziba	28	24.1	28	54.2	0
Mwamgongo	108	11.4	106	58.1	22.6
Total/average	235	12.4	219	46.9	13.8

^a Mtanga village has been excluded from this table, as no snails were found
^b All collected snails were tested for cercarial shedding and all shed cercaria confirmed to be S. mansoni based on morphology
^c Species confirmation through sequencing was made for 8 individuals from Mwamgongo village, one individual each from Kiziba and Bugamba and two individuals from Gombe National Park. For Kigoma municipality, all three products sequenced were from an unknown trematode rather than S. mansoni
Percentage prevalence based on PCR excludes individuals that did not show clear amplification of the snail band

ISSN: 1756-3305