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Published on: February 14, 2020
A low-virulence Eimeria intestinalis isolate from rabbit (Oryctolagus cuniculus) in China: molecular identification,
Tuanyuan Shi1, Guolian Bao, Yuan Fu
1Department of Animal Parasitology, Institute of Animal Husbandry and Veterinary Medicine, Zhejiang Academy of Agricultural Science, Hangzhou, 310021, China, lstone2008@126.com.
Abstract:
An Eimeria intestinalis isolated from a rabbit in China was first identified by amplifying the 18S small subunit (SSU) ribosomal RNA gene. The size of the amplified fragment was 1521 bp. The 18S SSU RNA gene of the E. intestinalis isolate shared 99% sequence identity with E. intestinalis isolates from France and the Czech Republic, with 100 and 96% coverage, respectively. Then, the pathogenicity and immunogenicity of the E. intestinalis isolate were evaluated in specific pathogen free (SPF) rabbits. In the pathogenicity assay, SPF rabbits in four groups were infected with 5 × 10(3), 5 × 10(4), 5 × 10(5), and 0 sporulated oocysts, respectively. Clinical signs including diarrhoea, constipation, loss of appetite, and reduction of body weight gain were observed in rabbits inoculated with 5 × 10(4) and 5 × 10(5) oocysts. And one rabbit (25 %) inoculated with 5 × 10(5) oocysts died 15 days after the inoculation. In the immunogenicity assay, SPF rabbits in five groups (named B1, B2, B3, B4, and B5) were immunised with 5 × 10(1), 5 × 10(2), 5 × 10(3), 0, and 0 sporulated oocysts, respectively. All rabbits but the B5 group were challenged with 1 × 10(6) oocysts. After the challenge, no or slight clinical signs were seen in rabbits of the B2 and B3 groups. Compared with the control, a 69.6 and 84.5% reduction of oocyst output was observed in the B2 and B3 groups, respectively. The body weight gain of the two groups was obviously higher than that of the challenge control group. All the results show that the E. intestinalis isolate has low virulence but immunogenicity in rabbit.
Insights
A new Eimeria intestinalis rabbit isolate from China shows low virulence but significant immunogenicity. Vaccination with low doses protected rabbits against infection, reducing oocyst output and improving weight gain.
Area of Science:
- Veterinary Parasitology
- Molecular Identification of Protozoa
- Rabbit Immunology
Background:
- Eimeria intestinalis is a significant rabbit pathogen.
- Genetic characterization is crucial for understanding parasite isolates.
- Assessing pathogenicity and immunogenicity informs control strategies.
Purpose of the Study:
- To identify and characterize an Eimeria intestinalis isolate from China.
- To evaluate the pathogenicity of the isolate in specific pathogen-free (SPF) rabbits.
- To assess the immunogenicity and protective potential of the isolate in SPF rabbits.
Main Methods:
- 18S ribosomal RNA gene amplification and sequencing for identification.
- Pathogenicity assays involving varying oocyst doses in SPF rabbits.
- Immunogenicity assays with different vaccination doses followed by challenge infection.
Main Results:
- The isolate shared 99% sequence identity with known E. intestinalis strains.
- High oocyst doses (5x10^4, 5x10^5) caused clinical signs including mortality.
- Vaccination with 5x10^2 and 5x10^3 oocysts significantly reduced clinical signs and oocyst output post-challenge.
Conclusions:
- The Eimeria intestinalis isolate from China exhibits low virulence.
- The isolate possesses immunogenic properties, offering protection against homologous challenge.
- This study provides a foundation for developing Eimeria vaccines for rabbits.
