Improved serological testing for bovine schistosomiasis in Eastern Africa

Background: In East Africa, bovine schistosomiasis, although common, is poorly appreciated and managed, detrimentally impacting upon livestock health. In certain settings, bovine schistosomiasis may be involved in zoonotic transmission of human schistosomiasis. Better disease management and more effective control of bovine schistosomiasis require the development of sensitive and specific serological screening and rapid diagnostic tools. 

Methods: We developed an enzyme-linked immunosorbent assay (ELISA) for Schistosoma bovis detection in cattle, utilizing nine shortlisted potential diagnostic protein targets. These shortlisted candidates, STI, IPP, OP, PGK1, COG, PDZ, and Sbp80 (as three fragments), were identified from Schistosoma japonicum homologs already reported with the highest diagnostic potential. In S. bovis, these proteins participate in various biological processes, including metabolic pathways, transcriptional regulation, glycolysis, phosphorylation, and cell signalling, although their real diagnostic potential has not been explored until now. 

Results: The ELISA was optimized using bovine blood serum samples from regions in Tanzania and validated for sensitivity and specificity. Two targets of specific focus, Conserved Oligomerix Golgi complex subunit 4 (COG) and a domain of the cysteine protease calpain (Sbp80), achieved the highest specificity and sensitivity among the recombinant proteins, with 92% and 88% sensitivity and 100% and 80% specificity, respectively. We further evaluated the COG-based and calpain-based ELISA on further “real-world” bovine serum samples from abattoir sites in Zanzibar, detecting S. bovis in 59.1% of tested animals. 

Conclusions: Both COG and calpain are promising candidates for serological screening and later inclusion in portable diagnostic tests for S. bovis infection in cattle. Such future diagnostic assays will enable better point-of-detection monitoring, and once scalable, aid in the control of disease in cattle.