Recombinant GMA56 and ROP17 of Eimeria magna conferred protection against infection by homologous species

One of the most common rabbits coccidia species, Eimeria magna is mainly parasitic in the ileal and jejunal epithelial cells. E. magna infection can affect the growth performance of rabbits or cause other secondary diseases. Traditional methods of anticoccidial treatment typically result in drug resistance and drug residue. Therefore, vaccination is a promising alternative. Gametocyte antigen 56 (GAM56) and rhoptry kinase family proteins (ROPs) are involved in oocyst wall formation and parasite invasion, respectively. A virulence factor, ROP17 contains a serine/threonine kinase catalytic domain. In this study, recombinant E. magna GAM56 (rEmGAM56) and ROP17 (rEmROP17) proteins were obtained from a prokaryotic expression system and their reactogenicity was investigated with immunoblotting. To assess the potential of rEmGAM56 and rEmROP17 as coccidiosis vaccines, New Zealand White rabbits were subcutaneously immunized with 100 μg rEmGAM56 (rGC group) or rEmROP17 (rRC group) twice at 2-week intervals followed by homologous oocyst challenge. The rabbit serum was collected weekly to detect the specific antibody levels. The cytokine levels of pre-challenge serum were measured by enzyme-linked immunosorbent assay and the rabbits were observed and recorded post-challenge for the onset of clinical symptoms. The weight gain, oocyst output, and feed conversion ratio were calculated at the end of the experiment. The results showed that both rEmGAM56 and rEmROP17 had good reactogenicity. The rEmGAM56- or rEmROP17-immunized rabbits had milder clinical symptoms and feed conversion ratios of 3.27:1 and 3.37:1, respectively. The rEmGAM56-immunized rabbits had 81.35% body weight gain and 63.85% oocyst output reduction; the rEmROP17-immunized rabbits had 79.03% body weight gain and 80.10% oocyst output reduction. The ACI of rGC and rRC groups were 162.35 and 171.03, respectively. The specific antibody levels increased rapidly after immunization. Significantly increased interleukin (IL)-2, interferon (IFN)-γ, and IL-17 levels were evident in the rGC and rRC groups (p < 0.05). The rEmGAM56 and rEmROP17 elicited humoral and cellular responses, which protected against E. magna infection in rabbits. Thus, rEmGAM56 and rEmROP17 are potential vaccine candidates against E. magna, and rEmROP17 performed better than rEmGAM56.

Biochemical and Pathomorphological Investigations on Rabbits with Experimentally Induced Hepatic Eimeriosis

The present study aimed to evaluate the changes in concentrations of some biochemical parameters, as well as macro and microscopic alterations during Eimeria stiedae infection in rabbits. The experiment was performed using 12 three-month-old healthy rabbits, randomly allocated into 2 equal groups: G1 (controls, uninfected animals) and G2 (rabbits infected with E. stiedae). Blood samples were collected at time zero (prior to the infection), 6th, 24th, and 48th hours, and also 7th, 14th, 21st, 28th days after the infection. After sampling, the blood was centrifuged, plasma was separated and frozen at −20 ºC until analyzed. Thawed plasma was used for the quantitative determination of haptoglobin (Hp), total protein (TP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), total cholesterol (TC), total bilirubin (TBIL), urea, and creatinine (CREA). The results in infected rabbits revealed a significant increase in Hp, AST, ALT, GGT, TBIL, and TC levels, as well as a significant decrease in ALP and urea. A weak hyperproteinemia was also observed. There were no changes in CREA concentration. At the end of the clinical investigation, all rabbits were humanely euthanized and necropsied. The post-mortem examination of the infected group revealed hepatomegaly, multifocal yellowish nodules diffusely spread over the liver surface and in the parenchyma, considerably dilated bile ducts, and biliary hyperplasia. Given the results obtained from this experiment, it can be affirmed that hepatic eimeriosis in rabbits is a severe parasitic disease leading to significant disturbances of liver histology and resulting changes in the biochemical profile of infected rabbits.

Salix babylonica L. as a Natural Anticoccidial Alternative in Growing Rabbits

Coccidiosis in rabbit production is responsible for high morbidity, mortality, and economic losses. The use of natural antimicrobial substances in rabbits represents a promising way to improve their health and production. The aim of the present study was to assess the activity of Salix babylonica hydroalcoholic extract (SBHE) on the elimination of Eimeria spp. in rabbits. The phytochemical compounds and chemical composition of SBHE were determined. The cytotoxicity of SBHE was determined by a microwell assay using Artemia salina. Twenty-five New Zealand rabbits, 28 days old and 872 ± 171 g body weight (BW), were used in a completely randomized design. The rabbits were assigned to five groups of five rabbits, control group (A) received only basal diet (BD), B group received BD + 25 mg/kg BW of SBHE, C group received BD + 50 mg/kg BW of SBHE, D group received BD + 100 mg/kg BW of SBHE, and E group received BD + coccidiostat Baycox® (75 mg/kg body weight) for 28 days. Feces samples were collected at days 0, 7, 14, 21, and 28; morphological and morphometric identifications of Eimeria were carried out by the flotation technique and counting of oocysts by the McMaster technique. The rabbits were found naturally infected with Eimeria spp. The SBHE present phytochemicals with anticoccidial activity, and the cytotoxicity test indicate that this extract is nontoxic. This study demonstrates that oral administration of SBHE at 25 and 50 mg/kg BW reduced the release of oocysts per gram of feces. This effect was observed at day 14 and had the most significant effect at day 28 for both concentrations. The results indicate that SBHE could be a natural alternative for the control of coccidiosis in rabbit production.

Efficacy of Sulphachloropyrazine, Amprolium Hydrochloride, Trimethoprim-Sulphamethoxazole, and Diclazuril against Experimental and Natural Rabbit Coccidiosis

There are no anticoccidial drugs labelled for rabbits in Kenya and those available are used as extra labels from poultry. The drugs are used in rabbits with limited knowledge of their efficacy and safety. The aim of this study was to determine the efficacy of sulphachloropyrazine, amprolium hydrochloride, and trimethoprim-sulphamethoxazole relative to diclazuril when used curatively against experimental and natural rabbit coccidiosis. In a controlled laboratory trial, sixty (60) rabbits were randomly allocated to six treatment groups, namely, 1A, 2B, 3C, 4D, 5E, and 6F, each with 10 rabbits. Groups 2B, 3C, 4D, 5E, and 6F were experimentally infected with mixed Eimeria species while group 1A served as uninfected-untreated (negative) control group. Four of the infected groups were treated with sulphachloropyrazine (5E), amprolium hydrochloride (2B), trimethoprim-sulphamethoxazole (6F), and diclazuril (4D) using dosages recommended by manufacturers. Group 3C served as infected-untreated (positive) control. A field efficacy trial in naturally infected rabbits was then undertaken. The results revealed that sulphachloropyrazine and diclazuril were effective against rabbit clinical coccidiosis by significantly reducing oocyst counts from 149.00±110.39 x 10⁴ to 3.31±0.86 x 10⁴ Eimeria spp. oocysts per gram of feces (opg) and 59.70±12.35 x 10⁴ to 0.0±0.0 x 10⁴ opg, respectively, in the laboratory trial. Similarly, sulphachloropyrazine and diclazuril recorded reduced oocyst counts in the field trial from 280.33±44.67 x 10³ to 0.44±0.14 x 10³ opg and 473.44±176.01 x 10³ to 0.0±0.0 x 10³ opg, respectively. Still, sulphachloropyrazine and diclazuril showed superior efficacy by registering lesion scores and fecal scores close to those of uninfected untreated control group. Trimethoprim-sulphamethoxazole recorded a satisfactory efficacy in the field trial by recording reduced oocyst counts from 266.78±37.03 x 10³ to 0.75±0.11 x 10³ opg but was not efficacious in the laboratory trial. Amprolium hydrochloride was not efficacious against clinical coccidiosis in both the experimental and field trials.

Survey of coccidial infection of rabbits in Sichuan Province, Southwest China

Coccidiosis is a challenging disease of wild and domestic rabbits both, caused by Eimeria and thereby leads enormous economic losses at rabbit farms. The present study carried out to survey the prevalence and intensity of coccidial infection among the rabbits in Sichuan Province, southwest China. A total of 110 faecal samples were collected from 11 farms situated in eight main rabbits rearing administrative regions. Oocysts in faecal samples were purified, sporulated and identified according to morphological features. The overall prevalence of infection was 56.4 % (62/110), with prevalence of 64 % (47/75) for local meat breeds of rabbit and 51.4 % (18/35) for Rex Rabbits (local fur rabbits). Weanling rabbits had the highest prevalence (74 %, 37/50), followed by young rabbits (45 %, 13/29) and the adult rabbits showed the lowest prevalence (42 %, 13/31). Concurrent infection with two to seven Eimeria species was found. In total, 9 species of Eimeria were identified from oocyst-positive samples. E. perforans was the most prevalent specie (42.73 %), followed in order by Eimiera media, E. irresidua, E. magna, and E. intestinalis with prevalences of 35.45, 34.55, 31.82, and 23.64 %, respectively. Results of the present investigation indicated that the prevalence of coccidial infection is high among the rabbit population in southwest China. This study also elucidate about the coccidial infection and emphasis to adopt control strategies in commercial rabbitories.