Abstract
BackgroundSchistosomiasis japonica is a common zoonosis. Domestic animals are the primary source of infection and play an important role in disease transmission. The prevalence and infectivity of this disease in domestic animals in China have significantly decreased and, for this reason, diagnostics with a higher sensitivity have become increasingly necessary. It was reported that polymerase chain reaction (PCR)-based methods could be used to detect schistosome infection in humans and animals and presented a high sensitivity and specificity. The present study aimed to develop a PCR-based method for detection of Schistosoma japonicum infection in domestic animals.MethodsA specific nested-PCR assay was developed to detect S. japonicum infection in domestic animals via amplification of a 231-bp DNA fragment of retrotransposon SjR2. The developed assay was first used in sera and dry blood filter paper (DBFP) from goats and buffaloes at different time points of infection. Then, 78 DBFPs from 39 artificially-infected bovines at 14 and 28 days post-infection and 42 DBFPs from schistosome-negative bovines from the city of Huangshan in the Anhui province were used to evaluate the diagnostic validity. Furthermore, this assay was used to detect S. japonicum infection in domestic animals in Dongzhi and Wangjiang counties.ResultsThe expected PCR product was detected in eggs and adult worms of S. japonicum and blood samples from S. japonicum-infected goats and water buffaloes, but not from Fasciola and Haemonchus contortus worms. The nested-PCR assay could detect the target S. japonicum DNA in DBFPs from goats and buffaloes after day 3 post-infection. The sensitivity in buffaloes at 14 and 28 days post-infection was 92.30% (36/39) and 100% (39/39), respectively. The specificity was 97.60% (41/42). The positivity rates in Dongzhi and Wangjiang counties were 6.00% and 8.00% in bovines and 22.00% and 16.67% in goats, respectively. The positivity rates in goats in both counties were higher than those in bovines with a significant difference in Dongzhi County but not in Wangjiang County (P < 0.05 and P = 0.23, respectively).ConclusionsOur results suggest that the developed nested-PCR assay may be used for the diagnosis of S. japonicum infection in domestic animals, and the control of S. japonicum infection in goats should be paid more attention.
Highlights
S. japonicum DNA was detected in all dry blood filter paper (DBFP) but not in sera collected on Validity of nested-polymerase chain reaction (PCR) for diagnosis of bovine schistosomiasis We detected S. japonicum DNA in both DBFP and sera from six artificially infected buffaloes artificially infected with 3 000 cercariae at days 3, 7, 14, and 28 postinfection (Table 1)
The results indicated that the expected amplification product was detected in all DBFPs and sera 7 to 28 days post-infection
Total a multiple samples collected from two goats and 6 buffaloes at different time points are collectively presented here ;bThe samples were positive by using Miracidium hatching test (MHT); cThe samples were collected on days 25 to 37 post-treatment when the MHT results were negative but male worm infection examined by perfusion on final day miracidia in stools has a low sensitivity and antibody detection lacks specificity, which limits the determination of prevalence rates [14]
Summary
The prevalence and infectivity of this disease in domestic animals in China have significantly decreased and, for this reason, diagnostics with a higher sensitivity have become increasingly necessary. The present study aimed to develop a PCR-based method for detection of Schistosoma japonicum infection in domestic animals. Buffaloes, cattle, goats and sheep, are the primary sources of infection and play a vital role in disease transmission. Because of the comprehensive control strategy implemented in China from 2004 to block the transmission of S. japonicum from cattle/buffaloes and humans to snails [2], the prevalence and intensity of infection of domestic animals with S. japonicum decreased to low levels and reached 0.013% in 2014 at the national level [3].
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