Clinical usefulness of Western blotting and ELISA avidity for the diagnosis of human toxocariasis

Who Let the Dogs Out? Unmasking the Neglected: A Semi-Systematic Review on the Enduring Impact of Toxocariasis, a Prevalent Zoonotic Infection

Toxocariasis remains an important neglected parasitic infection representing one of the most common zoonotic infections caused by the parasite Toxocara canis or, less frequently, by Toxocara cati. The epidemiology of the disease is complex due to its transmission route by accidental ingestion of embryonated Toxocara eggs or larvae from tissues from domestic or wild paratenic hosts. Even though the World Health Organization and Centers for Disease Control classified toxocariasis amongst the top six parasitic infections of priority to public health, global epidemiological data regarding the relationship between seropositivity and toxocariasis is limited. Although the vast majority of the infected individuals remain asymptomatic or experience a mild disease, the infection is associated with important health and socioeconomic consequences, particularly in underprivileged, tropical, and subtropical areas. Toxocariasis is a disease with multiple clinical presentations, which are classified into five distinct forms: the classical visceral larva migrans, ocular toxocariasis, common toxocariasis, covert toxocariasis, and cerebral toxocariasis or neurotoxocariasis. Anthelmintic agents, for example, albendazole or mebendazole, are the recommended treatment, whereas a combination with topical or systemic corticosteroids for specific forms is suggested. Prevention strategies include educational programs, behavioral and hygienic changes, enhancement of the role of veterinarians, and anthelmintic regimens to control active infections.

Western blotting: a powerful staple in scientific and biomedical research

Western blotting (WB), also known as immunoblotting, is a well-known molecular biology method that biologists often use to investigate many features of the protein, ranging from basic protein analysis to disease detection. WB is simple, unique, rapid, widely used routine tool with easy interpretation and definite results. It is being used in various fields of science, research and development, diagnostic labs and hospitals. The principle of WB is to accomplish the separation of proteins based on molecular weight and charge. This review addresses in detail the individual steps involved in the WB technique, its troubleshooting, internal loading controls, total protein staining and its diverse applications in scientific research and clinical settings, along with its future perspectives.

Dog and Cat Contact as Risk Factor for Human Toxocariasis: Systematic Review and Meta-Analysis

Toxocariasis, a neglected parasitic zoonosis with worldwide distribution, has been reportedly associated to different risk factors in several epidemiological and meta-analysis studies. However, dog and cat contact (environmental and animal exposure) as isolated associated risk factor for children and adults remains to be fully established. Accordingly, the present meta-analysis has aimed to directly assess dog and cat contact for toxocariasis seropositivity in under-18 and adult persons, using a survey strategy of PubMed/Medline, Embase, Scopus and Scielo Databases, from January 2009 to December 2021. A meta-analysis model of random effects was applied to estimate odds ratio (OR) with 95% Confidence Interval (CI). The statistical heterogeneity was evaluated by the Cochran Q-Test and I² values. A total of 41 transversal studies (n = 20.515 individuals) from different geographic regions (classified by the World Health Organization) were included herein. In overall, 1,882/13,496 (13.95%; 95% IC = 13.4–14.5) youngers and 513/7.019 (7.3%; 95% CI = 6.7–7.9) adults in contact with dogs or cats were serologically reagent for anti-Toxocara antibodies. Association of dog and cat contact was observed only in youngers, with both dogs (OR = 1.53; p < 0.0001) and cats (OR = 1.64; p = 0.0001). In addition, association of dog and contact and serology was statistically significant in populations of Americas (OR = 1.37; 95% CI = 1.1–1.7), Middle East (OR = 2.9; 95% CI = 1.6–5.1) and West Pacific (OR = 1.6; 95% IC = 1.3–1.9). In conclusion, contact with dogs and cats, particularly by younger individuals and in regions such as Americas, Middle East, and West Pacific, should be always a public health concern for toxocariasis. Moreover, dogs and cats should be periodically dewormed, washed and hair cleaned prior to contact with youngers. Finally, robust statistical results herein may serve as basis for future strategies and preventive measures for safer dog and cat contact.

Therapy and Prevention for Human Toxocariasis

For the last four decades, knowledge about human toxocariasis with regard to its epidemiology, pathophysiology, clinical spectrum, and imaging or laboratory diagnosis has substantially progressed. Knowledge about specific therapy with anthelmintics has lagged behind. To date, only four drugs are registered for human use, and their efficacy has rarely been assessed in prospective controlled trials. It is likely that the repurposing of potent anthelmintics from veterinary medicine will improve this situation. Due to its wide availability and a lack of major side effects during short regimens, albendazole has become the drug of choice. However, its efficacy should be more precisely assessed. The role of anthelmintics in the treatment of neurological or ocular toxocariasis remains to be clarified. Prophylactic measures in humans or companion animals are efficient and represent first-line treatments for the control of this zoonosis. Unfortunately, their implementation in areas or countries where toxocariasis epidemiology is driven by poverty is quite difficult or unrealistic.

Measurement of the IgG Avidity Index in the Diagnosis of Clinical Toxocariasis Patients

Toxocara spp. are parasitic nematodes responsible for human toxocariasis, a common zoonotic helminth infection. The five main features of human toxocariasis are the classical ocular toxocariasis and visceral larva migrans syndrome, followed by covert toxocariasis, common toxocariasis and neurotoxocariasis. The diagnosis of toxocariasis is feasible by considering clinical symptoms, anamnestic history and serology laboratory results; however, serological criteria cannot be used to distinguish active Toxocara infection from past exposure, which is an area of much discussion in clinical practice. In this context, we developed avidity tests (ELISA and immunoblotting) and evaluated their clinical usefulness in distinguishing past from active toxocariasis. Our study involved 46 patients divided into two groups: “active toxocariasis” (n = 14) and “chronic toxocariasis” (n = 32). According to the avidity indices obtained for both the chronic and active toxocariasis groups, we proposed two thresholds: first, an AI lower than 32% supports an active infection; secondly, a threshold above 42% can exclude an active infection. In order to use this assay in routine clinical practice, however, is still requires standardisation with regards to the method and threshold values, which can be established through studies involving larger populations.

Serosurvey of anti-Toxocara antibodies and risk factors in adolescent and adult pregnant women of southeastern Brazil

Toxocariasis is worldwide endemic parasitic anthropozoonosis with high risk to those in in vulnerable populations and particularly during pregnancy and childhood. Although the prevalence of anti-Toxocara spp. antibodies has been extensively studied, risk factors of pregnant women of different ages remains to be established. This study was designed to i) assess the presence of anti-Toxocara spp. antibodies in pregnant women that presented to the public health system in a city of southeastern Brazil, and ii) determine the risk factors for toxocariasis in adolescent and adult pregnant women. This cross-sectional study included 280 pregnant women (71 aged up to and including 17 years [adolescents] and 209 aged 18 years and older [adults]). Pregnant women voluntarily agreed to complete a socioeconomic questionnaire and provide serum samples. Anti-Toxocara IgG antibodies were screened by Enzyme-Linked Immunosorbent Assay (ELISA). Univariable and multivariable logistic regression models were performed to assess the risks for toxocariasis. Overall, 20.7% of pregnant women were seropositive (33.8% of adolescents and 16.3% of adults). Prevalence in pregnant adolescents was 2.6-fold higher than in adults (Odds ration [OR]: 2.63; 95% CI: 1.42-4.86, p = 0.003). Multivariate analysis revealed that contact with soil (p = 0.01; OR = 4.76) and being in the first trimester of pregnancy (p = 0.03; OR = 0.17) had significantly greater risk of toxocariasis for adolescents, and attainment of elementary through middle school education level (p = 0.05; OR = 8.33) was a risk factor in adult pregnant women. Toxocariasis is likely underreported and neglected in adolescent pregnant women; this age group should always be monitored for toxocariasis and correspondent clinical signs, particularly at late pregnancy.

Applications of western blot technique: From bench to bedside

Western blot (WB) or immunoblot is a workhorse method. It is commonly used by biologists for study of different aspects of protein biomolecules. In addition, it has been widely used in disease diagnosis. Despite some limitations such as long time, different applications of WB have not been limited. In the present review, we have summarized scientific and clinical applications of WB. In addition, we described some new generation of WB techniques.

Seroprevalence of Larval Toxocarosis in the Czech Republic

BACKGROUND

Larval toxocarosis (LT), a zoonotic disease transmitted by dogs, cats, and other carnivores, is caused by roundworms of the genus Toxocara. Humans become infected by ingesting embryonated eggs of this parasite. In this study, we present data on the seroprevalence of LT in the Czech Republic collected by the National Reference Laboratory for Tissue Helminthoses in 2012-2016.

METHODS

Using enzyme-linked immunosorbent assay, a total of 4428 adults and children with or without clinical symptoms were examined for the presence of IgG antibodies against Toxocara canis excretory-secretory antigens.

RESULTS

Of all the persons examined, specific Toxocara antibodies were detected in 160 (3.6%) individuals. There were, however, significant differences between various regions, with seropositivity rates ranging from 1.4 to 7.5%.

CONCLUSION

In comparison to studies from 1998 and 2004, our results suggest a decrease in overall Toxocara seroprevalence in the Czech population, whereby the rates are similar to or even lower than rates in some other Central European countries.

Serodiagnostic methods for diagnosing larval toxocariasis

Toxocariasis is a human infection primarily caused by larvae of Toxocara canis from dogs, and also by T. cati from cats. Children have a more significant risk of acquiring the infection due to their closer contact with pets, and greater chances of ingesting soil. Diagnosis of toxocariasis is based on clinical, epidemiological, and serological data. Indirect IgG ELISA is a widely used serodiagnostic method for toxocariasis, with native T. canis TES most commonly used as the antigen. Western blots, using the same antigen, can be used to confirm positive ELISA findings to reduce false-positive results. Improvements in Toxocara serodiagnosis include the use of recombinant TES antigens, simpler and more rapid assay formats, and IgG4 subclass detection. Also, incorporation of recombinant T. cati TES protein increases the diagnostic sensitivity. Development of antigen detection tests using polyclonal and monoclonal antibodies, nanobodies, or aptamers can complement the antibody detection assays, and enhance the effectiveness of the serodiagnosis.

Chickens bred extensively as sentinels from soil contamination by Toxocara

Environmental contamination by Toxocara spp eggs can be verified by parasitological techniques, which are mostly laborious, have low sensitivity, and may require repeated tests to establish the contamination status of a certain area. Given the significance of this parasite as an agent of infections in humans, that may cause blindness, especially in children, broilers chickens created extensively were evaluated as possible markers of parasite environmental contamination, through the detection of anti-Toxocara serum antibodies. Eighteen 15-day-old Label Rouge broilers were released on a farm with a history of dogs with Toxocara infection. At 0, 15 and 30 days after the release birds blood samples were taken, as well as soil samples. At the end of the experiment the birds were slaughtered, and the gastrointestinal tract was collected for coprological exams. The presence of anti-Toxocara antibodies resulted in increased reactivity indexes with time, and at 15 days five of the birds were positive and at 30 days, seven birds showed seroconversion. Examination of the soil samples by the centrifugation-flotation method in hyper saturated zinc sulfate solution revealed contamination by embryonated or infertile eggs of Toxocara at all times of collection, as well as the presence of Ascaridia eggs at 15 days after release of birds. Examination of bird's stool samples at the end of the experiment demonstrated 100% infection by Ascaridia galli, however there was no correlation between the counts of this parasite and the ELISA reactivity indices for anti-Toxocara antibodies. The results obtained allow us to infer the possibility of using anti-Toxocara spp-specific antibodies determination in birds raised extensively, which could then serve as sentinels of environmental contamination by this parasite.

Seroprevalence of human toxocarosis in Europe: A review and meta-analysis

Toxocarosis is distributed worldwide and represents the most prevalent zoonotic helminth infection in industrialized countries, thereby posing a substantial risk for public health. Thus, toxocarosis is one of CDC's Neglected Parasitic Infections that has been targeted for public health action. This systematic review and meta-analysis summarizes Toxocara seroprevalence in general populations from Europe, populations suspected of Toxocara infection and defined risk groups. Random-effects meta-analysis of proportions based on 41 publications resulted in an overall seroprevalence of 6.2% (95% CI: 4.7-8.3%) in the general population of Europe. Subgroup analysis according to decades (1970-2010s) revealed a significant increase in seroprevalence, with the highest value (12.4%; 95% CI: 6.5-22.3%) in the 2010s (χ²=17.87, df=4, P=0.001). There were no significant differences between pooled prevalence rates of European sub-regions (χ²=3.01, df=3, P=0.389). Furthermore, meta-analysis of seroprevalence according to age groups, based on data from 22 publications, indicated a significantly higher pooled seroprevalence of 14.9% (95% CI: 8.5-24.8%) in people more than 50 years of age than in younger age cohorts (χ²=8.33, df=2, P=0.016). Occupational groups exposed to contaminated soil and infected animals bear substantial risk for acquiring Toxocara infection. Due to the close link between animal infection and human Toxocara exposure, a "One Health" approach for the prevention of Toxocara infection in both humans and animals is required.

Toxocara infection in the differential diagnosis of multiple sclerosis in the Middle East

A critical step in the diagnosis of multiple sclerosis is to rule out a heterogeneous variety of multiple sclerosis mimickers, which is crucial in the era of powerful immune-modulator treatments. In this review, we discuss the background of toxocariasis in general, present central nervous system Toxocara infection as one of the multiple sclerosis mimickers in the Middle East, and share our experience about the diagnosis and management of this condition. This entity seems very relevant in a region such as the Middle East, where displacement of populations and conflict can result in non-hygienic food and water management bundles. The diagnosis should be entertained, especially when assessing patients with myelopathy. The presence of a single lesion in the spinal cord with inflammatory features should prompt serological testing for Toxocara IgG and IgM in serum and the cerebrospinal fluid. This infection is treatable, with the regimen of high-dose albendazole being one of the most accepted treatments. Although most cases exhibit a good prognosis, some have residual deficits localized to the affected spinal cord level.

Diagnosis of ocular toxocariasis by detecting antibodies in the vitreous humor

OBJECTIVES

To demonstrate the production of the local toxocara antibodies in the vitreous of patients with negative serology.

MATERIAL AND METHODS

Retrospective review of the medical records of patients seen in a Tertiary Referral Hospital, and at an Eye Institute, with an ocular diagnosis of toxocariasis who had a negative serology and positive titres in the vitreous.

RESULTS

After reviewing the medical records of 40 patients with a diagnosis of ocular toxocariasis, a total of six cases (15%) were found with a negative serology and a positive vitreous titre for toxocara antibody, both of them performed using an ELISA procedure. The mean age was 18 years, there were no differences observed between males and females. A peripheral granuloma was the most common clinic finding, and all patients underwent vitrectomy either to remove epiretinal membranes or to repair retinal detachments.

CONCLUSION

A negative serology does not rule out a diagnosis of ocular toxocariasis. Vitreous samples may be necessary to confirm a clinical diagnosis.

Potentiation of the humoral immune response elicited by a commercial vaccine against bovine respiratory disease by Enterococcus faecalis CECT7121

Vaccination against pathogens involved in bovine respiratory disease (BRD) is a useful tool to reduce the risk of this disease however, it has been observed that the commercially available vaccines only partially prevent the infections caused by Pasteurella multocida and Mannheimia haemolytica. Therefore, it is recommended to search for new adjuvant strategies to minimise the economic impact of this respiratory syndrome. A possibility to improve the conventional vaccine response is to modulate the immune system with probiotics, since there is accumulating evidence that certain immunomodulatory strains administered around the time of vaccination can potentiate the immune response. Considering veterinary vaccines are frequently tested in murine models, we have developed an immunisation schedule in BALB/c mice that allows us to study the immune response elicited by BRD vaccine. In order to evaluate a potential strategy to enhance vaccine efficacy, the adjuvant effect of Enterococcus faecalis CECT7121 on the murine specific humoral immune response elicited by a commercial vaccine against BRD was studied. Results indicate that the intragastric administration of E. faecalis CECT7121 was able to induce an increase in the specific antibody titres against the bacterial components of the BRD vaccines (P. multocida and M. haemolytica). The quality of the humoral immune response, in terms of antibody avidity, was also improved. Regarding the cellular immune response, although the BRD vaccination induced a low specific secretion of cytokines in the spleen cell culture supernatants, E. faecalis CECT7121-treated mice showed higher interferon-γ production than immunised control mice. Our results allowed us to conclude that the administration of E. faecalis CECT7121 could be employed as an adjuvant strategy to potentiate humoral immune responses.