Molecular characterization and serodiagnostic evaluation of the Echinococcus ortleppi recombinant glutaredoxin 1 protein for cystic echinococcosis in buffalo (Bubalus bubalis)

Cystic echinococcosis (CE), caused by the metacestode of Echinococcus granulosus sensu lato (s.l.), adversely affects the physiology of the vital organs in which they grow. Condemnation of meat causes substantial economic loss to the livestock industry. Conventionally the infection is detected by necropsy as serological diagnosis of the infection in livestock is ambiguous. Identification of specific diagnostic antigens would be a substitute for the cyst fluid antigens which lack adequate diagnostic sensitivity and specificity. BLAST analysis supported by the negligible pairwise nucleotide distance of the 389 nt COX1, 489 nt NAD1, and 425 nt ITS1 with the related sequences of E. ortleppi ascertained the association of E. ortleppi with CE in buffaloes. Given the extensive distribution of glutaredoxin 1 in every developmental stage of Echinococcus granulosus s.l that makes it an ideal serodiagnostic antigen for CE, we expressed the 14 kDa E. ortleppi glutaredoxin 1 (rEoGrx1) protein in E. coli BL21 (DE3) and tested a total of 225 sera samples, including 126 sera samples from the necropsy-positive buffalo, by the rEoGrx1 IgG-ELISA. The ELISA could detect a total of 82/126 sera samples as positive. The diagnostic sensitivity and specificity of the rEoGrx1 IgG-ELISA were 65.1 % and 51.5 %, respectively. The protein showed serological cross-reaction against Fasciola gigantica, Toxoplasma gondii, and Sarcocystis sp. The in silico bioinformatics analysis of the E. ortleppi, F. gigantica, and T. gondii glutaredoxin sequences revealed fully conserved amino acids at positions 11 and 21, the substitution of conserved amino acids at positions 14 and 6, and semi-conserved substitutions at positions 3 and 4, respectively. The findings partly explain the molecular basis of the serological cross-reactivity of the protein.

Meta-analysis of the prevalence of bovine cystic echinococcosis in China during decade

BACKGROUND

Cystic echinococcosis (CE) is a zoonotic parasitic disease caused by Echinococcus granulosus sensu lato (E. granulosus s.l.) larvae. It is mainly prevalent in western agricultural and pastoral areas in China, seriously affecting the development of public health and animal husbandry.

METHODS

This study conducted a systematic evaluation and meta-analysis of bovine CE in China in the past 10 years (2011-2020). Five databases (PubMed, ScienceDirect, CNKI, Wanfang Data, VIP Chinese Journal Database) were used to collect the relevant references, and finally 77 published articles were obtained.

RESULTS

The total prevalence of bovine CE was estimated to be 9.62% during decade, and decreased year by year after reaching its peak in 2014 (18.75%). The highest E. granulosus s.l. infection rate was found in Qinghai province (14.79%). The infection rate of cattle >4 years old (15.84%) was significantly higher than that of other age groups, and cattle raised by grazing was significantly higher than that of other methods (17.00%). In the groups of geographical and climatic factors, the prevalence of CE was higher in regions with high-altitude (20.76%), cold (20.76%) and rainy areas (11.33%).

CONCLUSION

This study found that old age and grazing were two important factors for the high incidence of bovine CE. The prevalence of CE is higher in low temperature, rainy and high altitude areas, where may be more suitable for the survival of E. granulosus s.l. eggs.

Echinococcus granulosus sensu lato and Echinococcus multilocularis: A review

Echinococcus spp. have a global distribution and are found on every continent except Antarctica. Infections with these parasites are considered extremely serious, contributing to significant morbidity and mortality in addition to substantial economic losses to the livestock industry. Echinococcus granulosus sensu lato (s.l.) and Echinococcus multilocularis, causing cystic echinococcosis (CE) and alveolar echinococcosis (AE) respectively, are the two main species of interest from a human and veterinary perspective. This review collates the current state-of-the-art understanding of these two parasites within four key areas of relevance to human and veterinary professionals: transmission and epidemiology, clinical signs and pathogenesis, diagnosis, and treatment and prevention. This review should serve as a broad introduction to the most important Echinococcus spp. The reader is advised to seek out specific literature on individual diseases and their causative parasites for a deeper understanding.

New insights of the local immune response against both fertile and infertile hydatid cysts

BACKGROUND

Cystic echinococcosis is caused by the metacestode of the zoonotic flatworm Echinococcus granulosus. Within the viscera of the intermediate host, the metacestode grows as a unilocular cyst known as hydatid cyst. This cyst is comprised of two layers of parasite origin: germinal and laminated layers, and one of host origin: the adventitial layer, that encapsulates the parasite. This adventitial layer is composed of collagen fibers, epithelioid cells, eosinophils and lymphocytes. To establish itself inside the host, the germinal layer produces the laminated layer, and to continue its life cycle, generates protoscoleces. Some cysts are unable to produce protoscoleces, and are defined as infertile cysts. The molecular mechanisms involved in cyst fertility are not clear, however, the host immune response could play a crucial role.

METHODOLOGY/PRINCIPAL FINDINGS

We collected hydatid cysts from both liver and lungs of slaughtered cattle, and histological sections of fertile, infertile and small hydatid cysts were stained with haematoxylin-eosin. A common feature observed in infertile cysts was the disorganization of the laminated layer by the infiltration of host immune cells. These infiltrating cells eventually destroy parts of laminated layer. Immunohistochemical analysis of both parasite and host antigens, identify these cells as cattle macrophages and are present inside the cysts associated to germinal layer.

CONCLUSIONS/SIGNIFICANCE

This is the first report that indicates to cell from immune system present in adventitial layer of infertile bovine hydatid cysts could disrupt the laminated layer, infiltrating and probably causing the infertility of cyst.

Immunization of sheep against Echinococcus granulosus with protoscolex tegumental surface antigens

AIM

Cystic echinococcosis (CE) has potential economic effects to both animal products and human health. A vaccine to protect livestock against CE can be effective in reducing economic costs and increasing the livestock products. Protoscolex tegumental surface antigens (PSTSA) used to induce the production of specific antibodies against Echinococcus granulosus in sheep. The tegumental antigens were extracted from viable protoscolices by solubilization in sterile phosphate-buffered saline containing decanoyl-N-methylglucamine.

MATERIALS AND METHODS

Ten lambs which were infected with CE (positive control), 10 negative control, and 10 test groups of sheep were included in the study. 300 µg emulsion of purified-PSTSA was injected intramuscularly in a two-step immunization on the first and 30 days. Sera were collected immediately before immunization and 6 times with 10-day intervals until 60 days post immunization. Thereafter, the sera were tested for antibodies by indirect hemagglutination test in microtiter plate.

RESULTS

After two immunizations, all the infected animals in test group showed substantial increases in antibody titer. Statistical analysis showed a significant difference between the titer obtained in the test and negative control groups in both phases of immunization (p<0.05).

CONCLUSION

The results showed that the PSTSA is a promising immunogenic compound for immunization of sheep against CE.