A Systematic Review and Meta-analysis of Toxocariasis in Iran: Is it Time to Take it Seriously?

Understanding the research and practical needs required to control toxocariasis in Iran

Human toxocariasis (HT) is a widespread zoonotic infection globally, notably prevalent in tropical areas. Enhancing our understanding of toxocariasis can lead to increased attention towards the socioeconomic impact and control of this neglected zoonosis. We conducted a comprehensive review of all available articles and official documents on toxocariasis in Iran to identify research gaps and critical needs for its control. This review highlights that despite numerous studies exploring various aspects of toxocariasis in definitive and paratenic hosts, as well as humans and environmental contamination, significant data deficiencies and gaps persist across different regions in the country. These gaps involve investigating the worm burden and reinfection rates in definitive hosts, developing more sensitive methods to detect and differentiate of Toxocara species, and understanding the behavior of definitive host animals. Additionally, identifying potential paratenic hosts for HT and exploring the organ-specific affinity and survival duration of Toxocara larvae within these hosts are essential areas for exploration. It's also imperative to comprehend the sylvatic and domestic cycles of the parasite in paratenic hosts. Furthermore, assessing egg density in the environment, exploring potential new sources such as water, and identifying regions with optimal climatic conditions for the survival and development of Toxocara eggs are crucial for the formulation of effective prevention and control strategies. Identifying at-risk groups, developing early diagnosis techniques, employing imaging methods, and identifying long-term complications in humans are also crucial. Community health organizations should prioritize health education for the public and professionals. Furthermore, accurately estimating definitive host populations, monitoring and preventing their movements in public places, implementing regular deworming practices for pets and stray hosts, and recognizing the infection's significance as a health priority are critical. This comprehensive understanding advocates for a holistic "one health" approach to control of HT.

Parasites of Stray Cats in Iran: A Parasitological and Histopathological Study

Many zoonotic parasitic diseases, including Toxocara cati, may be spread by stray cat populations. This study aimed to determine the prevalence of parasites by performing parasitological and histopathological examinations on stray cats in Shiraz, Iran. A total of 106 stray cats from different geographical areas of Shiraz, southern Iran, were examined for the presence of parasites. The overall prevalence was found to be 83.02% (88/106), and eight parasites were found. The parasites included three genera of cestodes [Joyeuxiella echinorhynoides (52.83%), Taenia taeniaeformis (21.70%), and Dipylidium caninum (1.89%)], three nematodes [Physaloptera praeputialis (23.59%), Toxocara cati (15.09%), and Rictularia sp. (1.89%)], one protozoa [Isospora spp. (6.60%)], and one arthropod [Ctenocephalides felis (5.66%)]. The prevalence did not significantly differ between males and females. It did appear, nevertheless, that the age of cats may be regarded as a risk factor for these parasitic infections. Histopathological examination revealed some parasite-induced lesions in the intestine and stomach, including hyperemia, hemorrhage, mucosal destruction and inflammation. The lung tissues showed some histopathological lesions such as hemorrhage, edema, emphysema and mild inflammation, and dormant larvae were found in one tongue sample. The results of the present study showed that parasitic infections and, more importantly, T. cati are relatively prevalent in stray cats, and the people living in this area are at serious risk of this zoonotic disease. The cats in this region need to be monitored, and specific preventive measures should be developed by public health officials.

Seroprevalence and Potential Risk Factors of Toxocariasis among General Population in Southwest Iran: Implications on the One Health Approach

Toxocariasis is one of the most common zoonotic diseases distributed worldwide. This study aimed to estimate the seroprevalence of anti-Toxocara immunoglobulin G (IgG) antibodies and the associated risk factors among general populations living in urban and rural areas of Abadan and Khorramshahr cities in Khuzestan Province, Southwest Iran. This cross-sectional study was conducted between March and September 2022. There were 363 participants (190 females and 173 males) aged from <20 to ≥60 years old. Anti-Toxocara IgG antibodies in serum samples were measured using a commercially available enzyme-linked immunosorbent assay (ELISA). A structured questionnaire was employed to collect information regarding sociodemographic status and probable risk factors associated with toxocariasis. It was found that the seroprevalence rate in males (15.0%, 95% CI = 10.47-21.11) was higher than in females (10.5%, 95% CI = 6.92-15.70). Moreover, we observed that the seroprevalence was higher in participants at younger ages compared to other age ranges (COR = 2.55, 95% CI = 0.92-7.12, p =0.073). The findings of the univariate analysis revealed that residency in rural areas (p  < 0.001), using unpurified water (p  < 0.001), contact with dog (p =0.002), contact with soil (p  < 0.001), consumption of improperly washed vegetables (p  < 0.001), and history of drinking untreated water (p  < 0.001) were risk factors associated with toxocariasis. Further comprehensive studies with a focus on humans and animals should be designed in different areas of the Province. The data represented by the current study are useful to health policymakers to consider precise surveillance and effective prevention measures to control this zoonotic infection among general populations.

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.

Deglycosylation of Excretory-Secretory Antigens of the Second-Stage Larvae of Toxocara cati Improves Its Efficacy in the Diagnosis of Human Toxocariasis

Background

Toxocariasis is an important zoonotic infection, especially in tropical areas. One of the significant challenges in the serodiagnosis of human toxocariasis is the cross-reaction of Toxocara antigens with other parasites due to their relatively similar glycan structures. Removing the glycan structure from Toxocara excretory-secretory (TES) antigens may increase the efficacy of these antigens in the diagnosis of toxocariasis. The current study aimed to assess the efficacy of deglycosylated Toxocara cati excretory-secretory (dTES) antigens for the serodiagnosis of human toxocariasis.

Methods

Toxocara ES antigens were prepared from T. cati second-stage larvae and deglycosylated using sodium hydroxide (NaOH). The TES antigens, along with the dTES antigens, were used in an ELISA as well as a western blotting system for the detection of anti-Toxocara antibodies. Sera samples collected from 30 confirmed cases of toxocariasis, 30 patients with other diseases, and 30 healthy subjects were evaluated by both systems.

Results

The sensitivity of TES and dTES ELISA for the diagnosis of human toxocariasis was 96.67% (95% CI = 82.78-99.92) and 93.33% (95% CI = 77.93-99.18), respectively, while the specificity of dTES (88.33%; 95% CI = 77.43-95.18) increased significantly compared to the TES (80.00%; 95% CI = 67.67-89.22). The sensitivity of both antigens was 100% (95% CI = 88.43-100) by the western blotting system. Moreover, the specificity of TES and dTES antigens was 95% (95% CI = 86.08-98.96) and 98.33% (95% CI = 91.06-99.96), respectively, when using the western blotting system.

Conclusion

Results of the current study indicate that the chemical removal of the glycan epitopes of T. cati ES antigens significantly reduces cross-reactivity rates with other parasitic infections. Considering the findings of the present study, the dTES antigens seem to be suitable antigens for the serodiagnosis of human toxocariasis.

Seroprevalence of Toxocariasis and Its Associated Risk Factors among Adult Population in Kavar District, Fars Province, South of Iran: A Cross-Sectional Community-Based Seroepidemiological Survey

Toxocariasis as a common neglected disease is the culprit of infecting all age groups. The current cross-sectional study was designed to assess the seroprevalence of toxocariasis and risk factors associated with seropositivity of Toxocara infection among the general population of adults in the Kavar district, south of Iran. A total of 1060 participants with an age range of 35 to 70 years from the Kavar region entered the study. Manual ELISA was utilized to detect anti-Toxocara-specific antibodies in their serum samples. In addition, demographic information as well as risk factors related to toxocariasis was collected from individuals who participated in the survey. The mean age of the participants was 48.9 (±7.9) years old. Out of 1060 subjects, 532 (50.2%) were men, and 528 (49.8%) were women. The overall Toxocara seroprevalence was 5.8% (61/1060). The prevalence of Toxocara seropositive cases was significantly different between males and females (p = 0.023). The seropositive rate for Toxocara infection was also significantly higher in housewives (p = 0.003) and subjects with learning disabilities (p = 0.008). Multivariable logistic regression revealed that housewives (OR = 2.04, 95% CI: 1.18-3.51, p = 0.010) and subjects with learning disability (OR = 3.32, 95% CI: 1.29-8.52, p = 0.013) were at increased risk of Toxocara infection. The findings of the current study depicted a noticeable seroprevalence of Toxocara infection in the general population in the Kavar district, southern Iran. An increased risk of toxocariasis has been associated with learning disabilities and being a housewife. All of the toxocariasis-positive cases had contact with animals, at some point in their life. In perspective, it is necessary to raise awareness of this infection among the population while surveilling Toxocara infection in high-risk groups.

Seroprevalence of Toxocariasis Among Hypereosinophilic Children: A Single Center Study, Tehran, Iran

Background: Toxocariasis is a parasitic disease causing hypereosinophilia. This study aimed to investigate the serological prevalence of toxocariasis among hypereosinophilic children in Children’s Medical Center, Tehran, Iran, as well as to explore its relationship with epidemiological variables and some blood indices. Methods: This descriptive cross-sectional study was performed in 2020 on children referred to referral children hospital for routine tests. A total of 282 children diagnosed with hypereosinophilia were selected and included in the study, and then, their serum was collected. After obtaining informed consent from their parents, the parents were asked to fill out a questionnaire. The serological ELISA test was used to assess the anti-Toxocara IgG antibody. Data were analyzed using SPSS software 18. Results: Out of 282 hypereosinophilic children, 17 (6%) had serological results positive for anti-Toxocara antibody. The mean age of children with toxocariasis was higher than that of children without toxocariasis (P = 0.312). Furthermore, ESR and CRP variables were significantly higher in infected children than those in non-infected children (P < 0.05). Conclusions: The results of the present study confirmed the relationship between toxocariasis and hypereosinophilia. Since the symptoms of toxocariasis are non-specific and may go undiagnosed, it was found necessary to examine toxocariasis in cases of hypereosinophilic individuals.

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.

Toxocara Species Infection in Pet Dogs and Cats Ensured by Loop-Mediated Isothermal Amplification Assay

Background: Toxocariasis is a parasitic disease with global distribution. Many paratenic or transport hosts have been identified as the sources of infection, including vertebrates such as birds and humans. The definitive hosts of Toxocara are dogs and cats whose parasites live in their guts. Hence, the diagnosis of the disease in these animals is important. Objective: The present study was performed using the loop-mediated isothermal amplification (LAMP) method to diagnose toxocariasis. Materials and Methods: In the present study, 60 samples of pet feces were collected and subsequently evaluated by direct smear, formalin-ether, and LAMP. Results: Toxocara infection in dogs by microscopic and formal ether methods and LAMP method was 10% and 13.3%, respectively, while feline infection with this parasite was not observed either microscopically or molecularly. Conclusion: The present findings revealed that pet dogs can be considered as a source of infection for humans. Therefore, it is recommended that animal owners receive the necessary training to prevent the risks of transmitting zoonotic diseases.

High Seroprevalence of Toxocara Infection among Mentally Retarded Patients in Hormozgan Province, Southern Iran

Mentally retarded individuals are more likely to become infected with soil-transmitted infections including toxocariasis. The current study aimed to determine the serostatus of toxocariasis among institutionalized mentally retarded individuals in Hormozgan Province, in the south of Iran. Subjects of the study were 117 mentally disabled individuals, including children and adults, maintained in a charity-based institution. Three millilitres of venous blood was taken from each subject. While sampling, demographic features of the subject were documented in a questionnaire. An ELISA system based on Toxocara larvae excretory-secretory antigens (TES) was utilized to detect anti-Toxocara IgG antibodies in the sera of the patients. The mean age of the subject was 27.6 (±12.31) years and consisted of 55 (47%) males and 62 (53%) females. Out of 117 cases, 33 (28.2%) were seropositive for toxocariasis. The seroprevalence was higher in females (37.1%) than males (18.2%), and the difference was statistically significant (p < 0.05). Out of 117 subjects, 76 (64.9%) had severe and 41 (35.1%) had profound mental retardation. Anti-Toxocara antibodies were detected in 18 (23.7%) patients with severe and 15 (35.6%) patients with profound mental retardation. The highest seroprevalence rate of toxocariasis (44.4%) was observed in the age group of ≤10 years followed by 21–30 years old (36.7%). No statistically significant association was seen between the age and also the duration of residency in the care center and seropositivity of toxocariasis (p > 0.05). The current study represents the high prevalence of toxocariasis in mentally retarded patients in Hormozgan Province, southern Iran. The elevated seroprevalence rate of toxocariasis in the current study indicates that these subjects constitute a high-risk group for Toxocara infection, which may be attributed to their behavioral patterns.

Systematic review and meta-analysis on the risk potential of zoonotic toxocariasis from soil contamination of public places in India

Parasitic zoonoses despite of their potential threats to human health remain neglected especially in developing countries. Toxocara canis and Toxocara cati worms are considered important zoonotic parasites and the ability of their infective ova to sustain longer in suitable edaphic environments poses constant risk of infection to humans. This systematic review and meta-analysis aims to highlight the burden and importance of soil borne toxocariasis in India. A total of 14 primary prevalence studies spanned over a period from 1985 to 2017 were included in this study. Due to expected variation between studies, a random-effects model was applied by using MetaXL add-on. The apparent prevalence based on the soil samples tested positive was found in the range of 2.11 to 31.0% while the weighted pooled prevalence was estimated as 11.26 (95% CI 07.59 - 15.54%). A high heterogeneity between studies (I² = 93.39 and Q = 227.024, p = 0.00) confirmed the diversity of the populations under study. This meta-analysis highlights the need of more studies on soil transmission of zoonotic toxocariasis in India.

Spatial Distribution of Common Pathogenic Human Intestinal Protozoa in Iran: A Systematic Review

Background:

Pathogenic intestinal protozoa are considered as a serious public health problem in developing countries. This study aimed to elucidate the overall prevalence and spatial distribution of three common human pathogenic intestinal protozoan infections in Iran.

Methods:

Six English and Persian databases were explored for published papers on the prevalence of Entamoeba histolytica/dispar, Giardia lamblia, and Cryptosporidium spp. in the general population of Iran from 2000 to 2015. All eligible data were collected using a pre-designed data extraction form, and the overall prevalence was estimated using a random-effects meta-analysis model. We used ArcMap for mapping the prevalence of the studied protozoa and clustering analysis.

Results:

Altogether, 118 eligible papers from 24 provinces of Iran were included and analyzed. The weighted prevalence of E. histolytica/dispar, G. lamblia, and Cryptosporidium spp. infection among Iranian general population were calculated 1.3% (95% CI 1.1–1.5%), 10.6% (95% CI 9.6–11.5%) and 2% (95% CI 1.5–2.5%), respectively.

Conclusion:

Our findings indicated human intestinal protozoan infections caused by E. histolytica/dispar, G. lamblia, and Cryptosporidium spp. have still public health importance in some parts of Iran.

A systematic review and meta-analysis of Hymenolepis nana in human and rodent hosts in Iran: A remaining public health concern

Hymenolepis nana, as a neglected zoonotic helminth, naturally occurs in both humans and rodents. Herein, a systematic review and meta-analysis was carried out to estimate pooled prevalence of H. nana infection among human and rodent hosts for the first time in Iran. PubMed, Web of Science, Scopus, and Embase databases (English articles) and SID and Magiran databases (Persian articles) were systematically searched for relevant studies published from inception till May 24, 2020. Chi² and I² index were used to assess the heterogeneity of the included studies. Publication bias was assessed using Egger's intercept and visual inspection of the funnel plot. Pooled prevalence was estimated using random-effects model with 95 % confidence interval (CI) and depicted as a forest plot. STATA software was used for analysis. The overall pooled prevalence estimate of H. nana in humans included 1.2 % (95 % CI = 1.0-1.4%). Subgroup analysis revealed 2.2 % (95 % CI = 1.8-2.6%) and 0.5 % (95 % CI = 0.3 to 0.8 %) of H. nana infection among school children and food handlers, respectively. In terms of rodent hosts, the overall pooled prevalence of H. nana infection included 13 % (95 % CI = 9.3-16.6%). Subgroup analysis revealed the highest rate of the infection was in Rattus spp. (19.6 %; 95 % CI = 10.6-28.6%), a genus with synanthropic behavior. It seems, despite the advancement in sanitation infrastructure and hygiene status, the H. nana infection compares to other helminthic diseases remains a challenging public health problem in Iran.

Intestinal helminthic parasites of rodents in the central region of Iran: first report of a capillariid nematode from Dryomys nitedula

OBJECTIVES

Rodents play an important role to spread zoonotic diseases through society. The current study was carried out to collect informative data on the intestinal helminthic infections of wild rodents in Taleqan County, Alborz Province, the center of Iran, emphasizing their zoonotic aspects.

RESULTS

Sixty-two killed rodents by local farmers belonging to five species were collected, among which 24 were identified as Mus musculus, 15 as Meriones persicus, 12 as Meriones libycus, 10 as Apodemus witherbyi, and 1 as Dryomys nitedula. Of them, 30 (48.4%) were infected with at least one helminth species. Rodents were infected with Hymenolepis diminuta (42%), Syphacia obvelata (21%), Hymenolepis nana (17.7%), Heligmosomoides polygyrus (9.6%), Trichuris muris (8%), and as well as a capillariid nematode that was isolated for the first time from D. nitedula in Iran. The findings of the present study revealed a significant intestinal helminthic infection of rodents in Taleqan County. Improving hygiene practices, and making a preventive attitude can be helpful to reduce the hazards of rodent-borne diseases in the area where humans, livestock, and synanthropic rodents are living close to each other.