A walk on the wild side: A review of the epidemiology of Toxocara canis and Toxocara cati in wild hosts

Park entrances, commonly contaminated with infective Toxocara canis eggs, present a risk of zoonotic infection and an opportunity for focused intervention

Toxocara canis and Toxocara cati, the common roundworms of dogs and cats respectively are commonly found in the soil of public parks. This zoonotic parasite can also infect humans causing difficult to diagnose diseases. Direct contact with contaminated soil is considered one of the primary routes of transmission from animals to humans with the contamination of public places common around the world. In this study we aimed to employ an easily repeatable soil sampling methodology to identify differences in contamination levels between and within parks. Egg density was found to differ significantly between parks and park entrances were the most heavily contaminated locations within parks, followed by playgrounds. Species confirmation by polymerase chain reaction was conducted on a proportion of the recovered eggs and identified most as T. canis (n=36) while three eggs were identified as T. cati. These results indicate that dogs are responsible for the majority of environmental contamination in Dublin City parks, with the highest levels of contamination found around park entrances. Concentration of preventive efforts on dog fouling at these sites is recommended to reduce risks of zoonotic disease transmission.

Morphological and molecular identification of Toxocara isolated from road-killed golden jackals in Northern Iran

BACKGROUND

Toxocariasis is caused by infection with Toxocara canis and Toxocara cati, common nematodes of canids and felids, respectively. Humans become infected after the accidental ingestion of embryonated eggs of Toxocara from the soil or the consumption of raw and undercooked meat containing Toxocara larvae. The aim of this cross-sectional study was to identify ascarid nematodes isolated from jackals in Guilan and Mazandaran provinces, based on morphological and molecular approaches.

METHODS

This cross-sectional study was conducted on 41 road-killed golden jackals collected from Guilan and Mazandaran provinces in northern Iran. At first, species identification was carried out based on morphological characterization. Genomic DNA was extracted from the isolates of Toxocara collected from jackals. PCR-RFLP of Ribosomal DNA regions (ITS) using RsaI endonuclease enzyme and PCR-sequencing were carried out to identify Toxocara species. The sequence data were aligned using Bioedit software and compared with published sequences in GenBank using the BLAST system. Phylogenetic analysis was performed using MEGA 5.0 software.

RESULTS

Eleven out of 41 road-killed golden jackals (26.8%) were infected with Toxocara nematodes. All the isolates were confirmed as T. canis based on morphological and molecular methods. A pairwise comparison of the sequences did not show any differences in nucleotide sequences within T. canis isolates, and the sequences were identical and exhibited 100% homology.

CONCLUSIONS

Considering the almost high prevalence of T. canis in golden jackals and its critical role in human toxocariasis, the identification of parasite species by molecular methods can be used to plan prevention and control programs in human and animal communities. Since, the ITS sequences of T. canis isolated from jackals in Iran were utterly similar to the ITS sequences of T. canis isolated from other hosts from different areas of the world, it is hypothesized that the type of host and geographical region do not affect the genetic diversity of the ITS region sequences of T. canis.

Role of sex hormones in the reactivation of Toxocara canis larvae in pregnant bitches

Based on an exhaustive review, a theory was proposed with an immunoendocrine perspective on the reactivation of dormant Toxocara canis larvae in pregnant bitches and their transmission to fetuses through the placenta, or milk and colostrum to puppies. A historical review was carried out on the reactivation of dormant larvae of T. canis in pregnant bitches which suggested that larval reactivation of T. canis is not solely the effect of a single hormone (prolactin) but is the result of a series of events triggered by progesterone, prolactin, and estrogens. In the first third of gestation, progesterone is capable of directly stimulating the reactivation of larvae through hormonal receptors, indirectly downregulating the granulomatous proinflammatory response around dormant T. canis larvae, and directing the response to a Th2 profile with increased levels of antibodies and blood eosinophils. After a time, when progesterone levels decrease, prolactin and estrogen maintain larval stimulation through hormonal receptors and downregulation of Th1 and the granulomatous proinflammatory response. Collectively, these hormones play major roles in the reactivation of T. canis larvae in pregnant bitches. The series of complex events that occur during larval reactivation is a clear example of transregulation, in which host hormones regulate the vital functions of the parasite to positively influence its establishment and/or proliferation. Understanding larval reactivation from an immunoendocrine perspective helps us to comprehensively understand the complex parasite-host relationship of T. canis.

The global prevalence of Toxocara canis among red foxes (Vulpes vulpes): A systematic review and meta-analysis

Red foxes play a crucial role in the life cycle and transmission of zoonotic pathogens, including Toxocara canis; however, comprehensive information on the prevalence of T. canis in red foxes (Vulpes vulpes) is lacking. In this meta-analysis we aimed to evaluate the global and regional prevalence of T. canis among red foxes. We searched PubMed, Scopus, and Google Scholar for studies reporting prevalence of T. canis in red foxes up to April 1, 2024. Using a random-effects model, we estimated pooled prevalences at global, regional, and national levels and assessed heterogeneity through subgroup and meta-regression analyses. The overall pooled global prevalence of T. canis infection in red foxes was 32.1% (95% CI, 28.5-35.6%), with the highest prevalence in Europe (34.6%, 30.9-38.3%) and the lowest in the Eastern Mediterranean (20.0%, 11.0-29.0%). In other regions, prevalences of Toxocara were as follows: Central Asia (33.1%, 26.8-39.4%), North America (23.6%, 10.6-36.6%), Western Pacific (21.3%, 5.2-37.4%), and Eastern Mediterranean & North Africa (20.0%, 11.0-29.0%). However, data from certain geographical regions are very limited (for example Greece, Austria, China and North Africa). Prevalence rates showed a decreasing trend over time. Subgroup analyses indicated higher prevalences in male red foxes (54.1%, 41.4-66.7%) compared to females (37.5%, 29.9-45.1%), and in juvenile red foxes (56.2%, 39.1-73.3%) compared to adults (33.4%, 23.2-43.6%). T. canis worm burdens were generally low, not exceeding an average of 4 worms per fox in most studies. Our findings reveal a substantial prevalence of T. canis infection in red fox populations worldwide (32.1%), highlighting their potentially significant role in perpetuating the transmission of infection to both companion animals and humans. Continued surveillance is essential to mitigate the risk of Toxocara transmission to companion animals and humans. However, a major remaining challenge is to assess the relative importance of the red fox as a contributor to environmental contamination with Toxocara ova. Further research is also needed to address study limitations and provide a complete global picture of T. canis epidemiology in red foxes and other wild animals, especially in underrepresented regions.

New records of endoparasites and ectoparasites in free-living road-killed wild animals in the Pampa biome, Southern Brazil

Wild animals host a wide variety of parasites, and the disorders caused by these parasites are among the most prevalent and significant infectious diseases affecting wildlife. The investigation of parasitic fauna is crucial for the conservation of wild animals, domestic populations, and humans. Therefore, the aim of the study was to survey endo- and ectoparasites in free-living wildlife in southern Brazil. Carcasses of road-killed wildlife were collected from highways in the Pelotas microregion, Rio Grande do Sul. All carcasses were necropsied, and endo- and ectoparasites were collected and identified. A total of 82 animals were examined; 87.80% were infected by helminths, 51.21% infested by ectoparasites, and 48.78% were affected by both types of parasites. This study presents the first records of parasitism by Rhipicephalus microplus in Ozotoceros bezoarticus in southern Brazil, and by Ancylostoma caninum in Leopardus geoffroyi worldwide. The study contributes to the knowledge about the parasitic fauna in wild animals of the Pampa biome. The presence of parasites in these threatened species underscores the need for further research into parasitism, which is crucial for their effective management and conservation.

Molecular identification of Baylisascaris melis (Gedoelst, 1920) from the Eurasian badger (Meles meles) and ascarids from other wild carnivores in Kazakhstan

Introduction

The presence of gastrointestinal nematodes, including zoonotic ascarids, in wild canids, felids and mustelids as definitive hosts in Central Asian countries has been documented in many studies based on traditional morphological methods. In contrast, relevant data for the badger are scarce. The aim of this study was the molecular identification of ascarid nematodes from five wild carnivore species in different regions of Kazakhstan.

Methods

A total of 211 adult ascarids were collected from gray wolves (Canis lupus, 8 of 83 infected with 2-6 Toxascaris leonina), red foxes (Vulpes vulpes, 26 of 53, with 2-8 Toxascaris leonina), corsac foxes (Vulpes corsac, 6 of 11, 3-6 Toxascaris leonina), lynx (Lynx lynx, 2 of 3, with 2-5 Toxocara cati) and badgers (Meles meles, 2 of 4, with 2-7 Baylisascaris melis). Genomic DNA was extracted from the worms and ribosomal DNA, including the first and second internal transcribed spacer genes, was amplified by polymerase chain reaction using specific oligonucleotide primers and then sequenced.

Results

Toxascaris leonina, but not Toxocara canis, was molecularly identified in the wild canids, Toxocara cati in the lynx and Baylisascaris melis in the badger. The maximum likelihood phylogenetic tree showed three distinct clades: the canid Toxascaris leonina was placed in one clade, Toxocara cati in another and Baylisascaris melis in a third.

Discussion

The study provides the world's first molecular data and phylogenetic analysis of Baylisascaris melis, identified for the second time since its description over 100 years ago. This species was shown to be genetically distinct from other Baylisascaris spp. (B. columnaris, B. procyonis, B. transfuga, B. devosi). The possible zoonotic significance of ascarids from wild carnivores is discussed in the light of conditions in Central Asia.

Epizootiological monitoring of wolf helminths in Northern and Central Kazakhstan

Background and Aim

Wolves (Canis lupus) play a role in nature, including the regulation of the number of ungulates and the use of dead animals. In addition, wolves are a natural link and carrier for the spread of many parasitic invasions. Hence, the main task in preventing the spread of parasitic invasions is to regulate the wolf population. This study aimed to monitor the endoparasitological fauna of wild wolves inhabiting Northern and Central Kazakhstan.

Materials and Methods

Overall, 81 wolves were investigated for parasitic worms using the K. I. Scriabin method. Wolf intestinal materials were collected from the following six regions: North Kazakhstan, Pavlodar, Kostanay, Akmola, Ulytau, and Karaganda. The genetic diversity of the parasites was identified using a polymerase chain reaction with specific primers. After data collection, a comprehensive statistical analysis was performed.

Results

Several helminth types were identified in wolves, including Echinococcus granulosus, Taenia hydatigena, Mesocestoides spp., Toxascaris leonina, Trichinella nativa, Alaria alata, and Dirofilaria repens. Based on the results of this study, young male wolves aged 1-4 years were the most vulnerable to helminthiasis. Wolves living in steppe and semi-desert regions are often exposed to helminth infections. The prevalence of T. nativa in the wolves was 20.4%. This study also revealed the presence of echinococcosis among wolf populations in Karaganda and Kostanay, with prevalence rates of 4.1% and 4.7%, respectively. The overall prevalence of tapeworms in wolves was 54.3%.

Conclusion

This study highlights the significance of understanding the potential risks associated with helminth infections in wild carnivores because helminths can act as disease reservoirs and pose a threat to humans, livestock, and other wild carnivores. These results can contribute to the development of effective control and management strategies for helminth infections in wolves, which can infect humans and livestock.

Quantifying the neglected: Initial estimation of the global burden and economic impact of human toxocariasis

Toxocariasis is a parasitic zoonotic infection caused by Toxocara spp., ascarid nematodes of companion animals (dogs and cats) affecting people in both high-income and low/middle-income countries. Toxocariasis can manifest as several distinct syndromes. The most frequent, often termed common toxocariasis, is a self-limiting and mild febrile illness. Ocular and visceral larva migrans are severe disease manifestations affecting the eye and other internal organs, respectively, but their reported occurrence is rare. The vast majority of symptomatic cases are thought due to common toxocariasis, which has also been associated with cognitive impairment in children. Few studies to date have sought to quantity the health burden of toxocariasis in humans. In this study we provide a preliminary estimation using the Disability-Adjusted Life Year (DALY) approach. We estimate a total of 23,084 DALYs are lost annually in 28 selected countries due to common toxocariasis. Extrapolating based on a global average seroprevalence rate of 19%, we estimate 91,714 DALYs per year are lost across all countries due to toxocariasis, of which 40,912 are attributable to less severe forms, i.e. common toxocariasis, and 50,731 to cognitive impairment in children. Clinically diagnosed and reported ocular and visceral larva migrans represent a small proportion of estimated total health burden. We also found a positive correlation at national level between prevalence in cats or dogs and seroprevalence in humans, but no correlation between estimated soil contamination and seroprevalence in humans. Finally, we estimate the potential economic impact of toxocariasis in selected countries at 2.5 billion USD per annum, from costs of medical treatment and lost income. These preliminary estimates should serve as a call to action for further research and evidence-based measures to tackle toxocariasis.

Toxocara cati Infection in Cats (Felis catus): A Systematic Review and Meta-Analysis

Introduction: Toxocariasis is an infection caused in canines, felines, humans, and other vertebrates by species of the genus Toxocara, such as T. canis and T. cati. The embryonated eggs of these parasites are the primary means of acquiring the infection for both definitive hosts, dogs and cats, respectively, and for intermediates, such as humans and other vertebrates. When deposited on park soils, environmental contamination becomes a risk to environmental, human, and animal health. Objective: To determine the global prevalence of Toxocara cati in cats (Felis catus). Methods: A systematic review of the literature was carried out in six databases (Scopus, PubMed, ScienceDirect, SciELO and Google Scholar) to evaluate the global prevalence of Toxocara cati in cats, defined by coproparasitological, histological, and molecular techniques. A meta-analysis was performed using a random effects model to calculate pooled prevalence and 95% confidence intervals (95% CI). A two-tailed 5% alpha level was used for hypothesis testing. Results: Two hundred and eighty-nine studies were included. The global pooled prevalence of Toxocara cati in cats using coproparasitological methods was 17.0% (95.0% CI: 16.2-17.8%). In the subgroup analysis according to country, Nepal had the highest prevalence of T. cati infection (94.4%; 95% CI 89.7-99.2%). The pooled prevalence of T. cati infection by PCR in four studies was 4.9% (95.0% CI: 1.9-7.9%). Conclusions: This systematic review underscores the need for preventive action against toxocariasis due to its widespread prevalence. The interplay between animal and human health should be emphasised, necessitating measures like deworming cats, hygiene practices, and public education to mitigate risks. Safeguarding feline health can also reduce human transmission, benefiting both species.