Real-time single-base specific detection of the Haemonchus contortus S168T variant associated with levamisole resistance using loop-primer endonuclease cleavage loop-mediated isothermal amplification

Haemonchus contortus is a parasitic haematophagous nematode that primarily affects small ruminants and causes significant economic loss to the global livestock industry. Treatment of haemonchosis typically relies on broad-spectrum anthelmintics, resistance to which is an important cause of treatment failure. Resistance to levamisole remains less widespread than to other major anthelmintic classes, prompting the need for more effective and accurate surveillance to maintain its efficacy. Loop-primer endonuclease cleavage loop-mediated isothermal amplification (LEC-LAMP) is a recently developed diagnostic method that facilitates multiplex target detection with single nucleotide polymorphism (SNP) specificity and portable onsite testing. In this study, we designed a new LEC-LAMP assay and applied it to detect the levamisole resistance marker S168T in H. contortus. We explored multiplexing probes for both the resistant S168T and the susceptible S168 alleles in a single-tube assay. We then included a generic probe to detect the acr-8 gene in the multiplex assay, which could facilitate the quantification of both resistance markers and overall genetic material from H. contortus in a single step. Our results showed promising application of these technologies, demonstrating a proof-of-concept assay which is amenable to detection of resistance alleles within the parasite population, with the potential for multiplex detection, and point-of-care application enabled by lateral flow end-point detection. However, further optimisation and validation is necessary.

Relationship between circulating antigen level and morbidity in Schistosoma mansoni-infected children evaluated by ultrasonography

Ninety-eight Schistosoma mansoni-infected children from an endemic area in Sharkia Governorate, Egypt were evaluated by abdominal ultrasonography to determine liver and spleen sizes, grade of periportal fibrosis, and splenic vein diameter. Circulating antigen levels were measured using a double sandwich ELISA in which the sensitivity was 91.8% and specificity was > 99%, with no evidence of cross-reactivity with other parasites. No significant relationship was observed between antigen level and clinical stages of the disease as assessed by physical examination (P > 0.05). When ultrasound was used to stage disease, the mean antigen level was significantly higher among hepatosplenic cases than intestinal cases (P < 0.05). No difference in mean antigen levels were found between the splenic and hepatic cases. Furthermore, a direct correlation (P < 0.01) was observed between antigen level and disease severity as monitored by ultrasonography. Antigen level showed a positive correlation with the degree of periportal fibrosis (P < 0.05). Moreover, a significant increase in the percent of children who were antigen positive (> 80 ng/ml) was found in those with more severe periportal fibrosis (P < 0.001). The findings suggest that ultrasonography along with measurement of circulating antigen levels predict morbidity in schistosomiasis mansoni.

The importance of detecting circulating Toxoplasma antigens in human cases

This work was performed on 100 suspected toxoplasmosis cases including 75 females with complicated obstetric histories, 15 children presented with hydrocephalus, retino-chorditis and lymphadenitis and 10 children suffering from leukaemia. Also 40 age-matched controls were included in this study. Serum samples from all patients and controls were examined to detect anti-Toxoplasma IgG and IgM using indirect ELISA. Antiserum against Toxoplasma avirulent strain was prepared in New-Zealand white rabbit, then it was used after purification for detecting circulating Toxoplasma antigens in the sera of these studied groups using a double antibody sanwich ELISA technique. Positive anti-Toxoplasms IgG was detected in 45% of the female group while 19% were IgM positive. According to IgM/IgG ratio, 9 cases were considered as acutely infected-females and 25 as chronically infected ones. The mean optical density of both IgG and IgM among acutely and chronically infected females were found significantly higher than of the control groups. Ten non-leukaemic children were IgG and IgM positive cases and were considered as acutely infected patients. On the other hand, all children with leukaemia were negative for anti-Toxoplasma IgG and IgM. Eleven out of 19 acutely infected cases (58%) had positive Toxoplasma antigens, whereas, only one case (4%) with chronic infection had positive antigen level. The mean optical density of circulating antigen level was significantly higher among acutely infected females and children than chronically infected and control groups. No antigen level difference was found between chronically infected patients and control groups. Six children from leukaemic group (60%) had positive circulating Toxoplasma antigen levels with significantly higher mean optical density than control groups (P < 0.001). As a conclusion the results demonstrate that the detection of circulating antigens can aid in the diagnosis of infection by T. gondii in humans, specially in immuno-compromised patients whose serologic response can be impaired.