Abstract
The cause of zoonotic schistosomiasis in the Philippines is Schistosoma japonicum, which infects up to 46 mammalian hosts, including humans and bovines. In China, water buffaloes have been identified as major reservoir hosts for schistosomiasis japonica, contributing up to 75% of human transmission. In the Philippines, water buffaloes (carabao; Bubalus bubalis carabanesis) have, historically, been considered unimportant reservoirs. We therefore revisited the possible role of bovines in schistosome transmission in the Philippines, using the recently described formalin-ethyl acetate sedimentation (FEA-SD) technique and a qPCR assay to examine fecal samples from 153 bovines (both carabao and cattle) from six barangays in Northern Samar. A high prevalence of S. japonicum was found using qPCR and FEA-SD in both cattle (87.50% and 77.08%, respectively) and carabao (80.00% and 55.24%, respectively). The average daily egg output for each bovine was calculated at 195,000. High prevalence and infection intensity of F. gigantica was also found in the bovines by qPCR and FEA-SD (95.33% and 96.00%, respectively). The identification of bovines as major reservoir hosts for S. japonicum transmission suggests that bovine treatment and/or vaccination, as one becomes available, should be included in any future control program that aims to reduce the disease burden due to schistosomiasis in the Philippines.
Highlights
Schistosoma japonicum, the cause of zoonotic schistosomiasis, infects more than 40 species of wild and domestic animals [1], complicating control efforts
Using quantitative real time polymerase chain reaction (qPCR) as the reference standard the formalin-ethyl acetate sedimentation (FEA-SD) had a sensitivity of 60.8% (Table 1) and specificity of 32.1% (95%CI 15.9–52.35)
Barangay prevalence ranged from 55.56%– 100% for qPCR and 53.3%– 80.0% for FEA-SD
Summary
Schistosoma japonicum, the cause of zoonotic schistosomiasis, infects more than 40 species of wild and domestic animals (including bovines, pigs, horses and goats) [1], complicating control efforts. Mathematical modelling predicts that up to 75% of S. japonicum transmission to humans is attributable to bovines in the lake and marshland areas of China [2]. This is due to the fact that infected water buffaloes and cattle excrete daily up to 60 kg of stool per individual [3,4,5]. With such a large volume of feces excreted daily, the potential number of eggs excreted is high. Water buffaloes habitually spend much of their time immersed in water bodies, such as rivers, lakes and water holes, into which they tend to defecate directly, so that if Oncomelania hupensis are present, the likelihood of transmission is high
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