Comparative analysis of host resistance to Sarcoptes scabiei var. cuniculi in two different rabbit breeds

Abstract

Background: Scabies, caused by infestation of the mite Sarcoptes scabiei, is one of the most severe ectoparasitic diseases in rabbits. Scabies seriously affects the commercial rabbit breeding, causing severe economic losses. Host resistance to S. scabiei is an important factor in further development of the rabbit industry. In the present study, we compared the host resistance to S. scabiei var. cuniculi of a new breed of domestic rabbit propagated by the Sichuan Animal Sciences Academy (QiXing rabbit, QX) compared with that of a traditional rabbit breed in the domestic rabbit industry (IRA rabbit, IRA).

Methods: Both QX and IRA rabbits were experimentally infested with live S. scabiei var. cuniculi mites for 48 h. Then, during the course of four-week experimental infestation period, the body weight of rabbits was recorded every two weeks for calculating body-weight variations in comparison to the non-infested control rabbits. Skin lesions in the foot area were assessed on weekly basis and serum samples were tested weekly for the estimation of changes in the total antibody levels (IgG, IgE and IgM). Moreover, DNA extracted from the blood samples was amplified for analysis of the genetic diversity in the major histocompatibility complex, class II, DQ Alpha (MHC-DQA) gene.

Results: Compared to the IRA rabbits, the QX rabbits showed a significantly higher (P < 0.05) relative body weight gain compared to the non-infested control rabbits and significantly lower (P < 0.05) scores for foot skin lesions and higher levels of IgG, IgE and IgM at weeks 1 to 4, week 2 and week 1 post-infestation, respectively. Furthermore, a polymorphism site at position 103 bp of exon two of MHC-DQA gene and a different gene frequency were found between two rabbit breeds, suggesting the genetic basis for the differential host resistance to the S. scabiei var. cuniculi between two rabbit breeds.

Conclusions: The QX rabbits showed higher host resistance to S. scabiei var. cuniculi compared to the IRA rabbits at the clinical, immunological and genetic levels. These results provide a reference for the breeding of rabbits with adequately improved and sustained host resistance to scabies in the domestic rabbit industry.

Keywords: Antibodies levels; Host resistance; MHC-DQA; Rabbit breeds; Sarcoptes scabiei.

Fig. 1

Assessment of the relative body weight gain (%) in two breeds of rabbit infested with the S. scabiei var. cuniculi and non-infested control. The body weight of each rabbit was recorded at weeks 0, 2 and 4 post-infestation (PI) and the relative body weight gain was assessed from the percentage increase in body weight of the experimentally infested and non-infested control rabbits at weeks 2 and 4 PI relative to the body weight at week 0 PI, which was calculated as [(Body weight at week 2/4 PI − Body weight at week 0 PI)/Body weight at week 0 PI] × 100%. Data points correspond to the mean of the percentage of the relative body weight gain for each group at a given time and the error bars represent the standard deviation (SD). Abbreviations: QX, QiXing rabbit propagated by the Sichuan Animal Sciences Academy, China; IRA, IRA rabbit breed; Exp, experimentally infested rabbits; Con, non-infested control

Fig. 2

Differential assessment of the skin lesions at each week post-infestation in two rabbit breeds infested with S. scabiei var. cuniculi. The assessment was made using the lesion score method. The lesion scores in the experimentally infested rabbits were recorded on weekly basis. Skin lesions were scored on a 0–5 grade based on the inflammatory reaction in toe area of the hind limb as well as the lesion areas of the experimentally infested rabbits. Histogram represents the mean of the lesion scores for each group at a given time and the error bars represent the standard deviation (SD). Asterisks indicate statistically significant differences in the lesion score between two different groups of rabbits (*P < 0.05). Abbreviations: QX, the QiXing rabbit propagated by the Sichuan Animal Sciences Academy, China; IRA, the IRA rabbit

Fig. 3

Differential assessment of serum total antibody levels at each week post-infestation in two rabbit breeds infested with S. scabiei var. cuniculi. The serum samples were collected from the experimentally infested rabbits on weekly basis for assaying the total antibody levels by an enzyme-linked immunosorbent assay (ELISA) using the commercial kits. a Average total IgG levels in experimentally infested rabbits in two breeds at each week post-infestation (g/l). b Average total IgE levels in experimentally infested rabbits in two breeds at each week post-infestation (μg/ml). c Average total IgM levels in experimentally infested rabbits in two breeds at each week post-infestation (μg/ml). The histogram represents the mean of the total antibody levels for each group at a given time and the error bars represent the standard deviation (SD). Asterisks indicate statistically significant differences in the total antibody levels between two different groups of rabbit (*P < 0.05) and ‘n.s.’ indicates non-significant differences. Abbreviations: QX, the QiXing rabbit propagated by the Sichuan Animal Sciences Academy, China; IRA, the IRA rabbit

Fig. 4

Agarose gel electrophoresis for the amplification and genetic diversity analysis of MHC-DQA gene. The blood samples were collected from the experimentally infested rabbits at week 4 post-infestation for amplification of MHC class II DQA gene by direct PCR, and the genetic diversity on the second exon of MHC-DQA gene between two breeds of rabbit were analyzed by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method with Mbo II enzyme. a Amplification of MHC-DQA gene in QiXing rabbits and IRA groups. Lane M: DL2000 DNA marker; Lanes 1–18: amplicons from experimentally infested rabbits in each group. b Analysis of genetic diversity in MHC-DQA gene by PCR-RFLP method with Mbo II enzyme. Lane M: D50 DNA marker; Lanes 1–18: amplicons from the experimentally infested rabbits in each group. Abbreviations: QX, the QiXing rabbit propagated by the Sichuan Animal Sciences Academy, China; IRA, the IRA rabbit