الفهرس 
Historical BackgroundOnly 14 pages are availabe for public view
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Abstract
Trichinellosis caused by Trichinella species is a worldwide foodborne parasitic zoonosis. Infection occurs after eating undercooked or raw meat from pigs having infective Trichinella larvae (Yayeh et al., 2020). Clinical diagnosis of trichinellosis is difficult as it has no pathognomonic clinical presentation (Bruschi et al., 2019).
ELISA can offer relatively sensitive, specific, and reliable results (Wu et al., 2019). False-negative results are the main disadvantage of this method especially in the early stage of infection (Wang et al., 2017) as there is a window period between antibody positivity and Trichinella infection. Some studies have shown that T. spiralis adult worm crude antigens were recognized in the serum of mice on the 7th dpi (Wang et al., 2017). Coproantigen detection has an advantage over other diagnostic methods as it indicates only the current infection (Eckert, 2003).
With the increased applications of nanotechnology in biomedicines, nanoparticles have been studied intensively to improve the efficiency of diagnostic assay, such as ELISA (Tang et al., 2013). The gold nanoparticles are the most studied type of metal nanoparticles for their applications in immunoassays and PCR (Wu et al., 2019).
This study was designed to compare the performance of NGB-ELISA and the traditional sandwich ELISA for the early detection of T. spiralis crude excretory antigen (CEA) in serum and faecal samples of experimentally infected mice.
The present study was performed on 180 male Swiss albino mice aged 60 days. The animals were obtained from Theodore Bilharz Research Institute (Giza, Egypt) and were maintained according to the National Guidelines for Experimental Animal Welfare after the approval of the Ethical Committee of Faculty of Medicine Menofia University (IRB 4/2018 PARA15). They were divided into the three following
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groups: T. spiralis infected group in which, 108 mice were infected with T. spiralis at a dose of 300 T. spiralis ML. Mice from this group were subdivided according to the time of sacrification into 9 subgroups (12 mice each). Mice from these subgroups were sacrificed and the serum samples were collected on the 2nd, 4th, 6th, 8th, 10th, 12th, 14th, 21st, and 28th dpi, while stool samples were collected on the 2nd, 4th, 6th, 8th, and 10th dpi and prepared for further investigations then muscle samples were collected from mice sacrificed on the 28th dpi. Specificity control group in which 18 mice were gifted from other experiments running at the same time. This group included mice infected with Cryptosporidium, T. gondii, and S. mansoni (6 mice each). Mice were sacrificed at the end of each parasite cycle (30, 60, and 60 dpi respectively) and stool and sera were collected at the time of sacrification. Negative control group included 54 non infected mice that were subdivided according to the time of sacrification into 9 subgroups (6 mice each). Mice from each subgroup were sacrificed at the same schedule applied for T. spiralis infected group and stool and sera were collected as described for T. spiralis infected group (GI).
In this study, T. spiralis muscle larvae were detected microscopically in digested muscles of T. spiralis-infected mice sacrificed on the 28th dpi. In direct smear examination of stool samples, diagnostic stages of T. spiralis were not detected in all studied groups at any day of examination.
Regarding the merthiolate iodine formaldehyde concentration technique of stool samples, results showed that in T. spiralis-infected group, diagnostic stages (larvae and adults) were present in 5% of mice sacrificed on the 6th dpi. Faecal samples from specificity control and negative control groups were 100% negative during all days of examination.
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Results of this study demonstrated that there was a statistically highly significant difference between the number of positive samples for CEA in NGB-ELISA in serum of T. spiralis-infected group sacrificed on the 2nd, 4th, 6th,8th dpi when compared to traditional ELISA.
On comparing the performance of traditional ELISA and NGB-ELISA for the detection of CEA of T. spiralis in serum samples, results showed that the NGB-ELISA detected the T. spiralis CEA earlier than traditional ELISA (as early as the 2nd dpi versus 10th dpi). NGB-ELISA showed sensitivities of 33.33%, 66.67%, 91.67%, and 100% on days 2, 4, 6, and 8 pi compared to sensitivities of 0% on the same days for traditional ELISA. On the next days, NGB-ELISA continued to have a 100% sensitivity while the traditional ELISA started to display improving sensitivities of 66.67%, 75%, and 91.67% on the 10th, 12th, and 14th dpi and reached a 100% sensitivity on the 21st and the 28th dpi. Corresponding performance characteristics were detected for NPV and accuracy in both NGB and traditional ELISA for T. spiralis CEA in serum samples.
Regarding the specificity of NGB and traditional ELISA for T. spiralis CEA in serum samples, no false positive results were detected in the serum of the negative control group either by traditional ELISA or by NGB-ELISA, and the specificity was calculated to be 100% for both assays. However, in the specificity control group, the NGB-ELISA had a superior specificity (100%) in all subgroups while the traditional ELISA had an occurrence of false positive results in the T. gondii and S. mansoni subgroups with a specificity of 83.33% for both tests.
Results showed that both traditional and NGB- ELISA were able to detect CEA of T. spiralis in 100% of the examined stool samples of T. spiralis-infected mice as early as the 2nd dpi and on all subsequent days. On comparing the performance
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characteristics of traditional ELISA and NGB-ELISA for the detection of T. spiralis in faecal samples, there were no false positive results in stool samples of the negative control group either by traditional ELISA or by NGB- ELISA. So, the specificity was 100% for both tests. Sensitivity, PPV, NPV, and accuracy were 100 % for both ELISA tests throughout the experiment. Similarly, in the specificity control group, there were no false positive results in stool samples either by traditional ELISA or by NGB- ELISA. So, the specificity was 100% for both tests.