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Parasites and Conservation Biology
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Just as parasites can signal dangerous conditions, hosts can be used to monitor the presence of unwanted parasites. One recent study was interested in determining if the eggs of the dog-infecting nematode Toxocara canis eggs had contaminated a particular location. This is worth knowing because if the eggs of this parasite are ingested, they can cause visceral larval migrans, often with ocular complications in children. A flock of chickens was turned loose on the location and within 15 days had developed antibodies consistent with exposure to T. canis, indicative of the presence of its eggs in the soil. The use of sentinel hosts could prove to be an easier way to detect Toxcara than tedious methods to identify eggs in soil samples.
The Parasitic Protozoa and Helminth Worms
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Another disease that can occur in humans is visceral larval migrans caused by accidental infection with ascaridids of dogs and cats (Toxocara canis and Toxocara cati). These have life cycles similar to that of Ascaris lumbricoides. When ingested by humans, Toxocara eggs hatch but cannot develop into adult worms and continue to migrate throughout the body until they finally die. During this migration, larval antigens elicit various immune responses, including the production of IgE antibodies, resulting in eosinophilic granulomas around the larvae. Visceral larval migrans is most commonly seen in small children because of their closer association with cats and dogs and greater opportunity to ingest infective eggs.
Candida and parasitic infection: Helminths, trichomoniasis, lice, scabies, and malaria
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Toxocara canis (visceral larva migrans) is cosmopolitan, with dogs as the definitive host. The adult worms are 4 to 10cm long and inhabit dog intestines. Toxocara eggs are thick shelled and spherical. Humans are incidental hosts (32). Toxocara eggs pass into soil, mature, and are ingested by rodents. Upon ingestion, the larvae are released and migrate throughout the body. Dogs ingest infected meat, with release of larvae in the stomach and maturation in the intestine. Human infection, called visceral larva migrans, occurs via ingestion of infective eggs with subsequent larval release and migration (32). Clinical diagnosis is based on history of contact with a pet and clinical examination. Laboratory diagnosis can be made by serologic testing for larval antigens, but there is some cross-reactivity with Ascaris lumbricoides. Clinical diagnosis is considered sufficient for treatment.
Recurrent Bilateral Vasculitis without Granuloma in a Well-treated Neurotoxocariasis with Optic Neuritis
Published in Ocular Immunology and Inflammation, 2023
Maxime Nhari, Amina Rezkallah, Matthieu Gerfaud-Valentin, Pascal Seve, Laurent Kodjikian, Philippe Denis, Thibaud Mathis
Vasculitis has been described in animals with ocular toxocariasis, and was supposed to be caused by vascular infiltration of neutrophilic leukocytes.1,2 Despreaux et al., in a series of 14 patients with ocular toxocariasis found 57% of unilateral vasculitis, although bilateral vasculitis has been scarcely described in the literature.3 Optic neuritis has rarely been observed in association with nematode infection. Komiyama et al. reported a patient with eosinophilic meningoencephalomyelitis due to T. canis with retrobulbar optic neuritis.4 Herein, the patient developed a bilateral occlusive vasculitis without any retinal granuloma in a context of a confirmed neurotoxocariasis with optic neuritis. Moreover, the patient did not show hypereosinophilia in blood samples, as usually encountered in case of parasitic infection. However, Pawlowski has already reported that eosinophilic cell count might be normal in some clinical presentation5; for instance, 73% of covert toxocariasis, 9% of incomplete visceral larva migrans syndrome, and 81% of suspected ocular Toxocariasis did not show hypereosinophilia.
A Rare Case of Congenitally Acquired Ocular Toxocariasis in A Five-Week-Old Infant
Published in Ocular Immunology and Inflammation, 2021
Chris Or, James A. David, Munraj Singh, H. Sprague Eustis, D. Anthony Mazzulla, Stephen Hypes, Joseph Benevento
OT is usually diagnosed clinically and supported by serologic testing with an indirect enzyme-linked immunosorbent assay (ELISA) based on anti-Toxocara antibodies, although in ocular variants the ELISA may return negative depending on infectious load.1 Although visceral larva migrans (VLM) warrants anti-helminthic therapy, treatment for ocular toxocariasis is controversial. As humans are intermediate hosts and the larvae cannot multiply, steroids may be initiated without anti-helminthic therapy, but some question this monotherapy due to concern of immunosuppression and risk of larvae migration. For populations in endemic areas, primary prevention includes avoidance of disposal of pet litter by pregnant individuals, avoidance of ingestion of undercooked meats, and proper handwashing techniques.1 The range of infectivity of toxocariasis depends on the host’s inflammatory response to infection, the parasite load, and the migration of larvae.1
Keys to Unlock the Enigma of Ocular Toxocariasis: A Systematic Review and Meta-analysis
Published in Ocular Immunology and Inflammation, 2021
Milad Badri, Aida Vafae Eslahi, Meysam Olfatifar, Sahar Dalvand, Elham Houshmand, Amir Abdoli, Hamidreza Majidiani, Ali Eslami, Mohammad Zibaei, Morteza Ghanbari Johkool, Ali Taghipour, Sima Hashemipour
A broad range of zoonotic parasitic diseases are transmitted by animals, especially cats and dogs.1,2 Toxocariasis is an important neglected tropical disease with a worldwide distribution mainly caused by larvae of the Toxocara canis or Toxocara cati, which are intestinal ascarid nematodes of canids and felids, respectively.3–5 It is estimated that 19.0% (95%CI, 16.6–21.4%) of people worldwide is seropositive regarding Toxocara spp. infection.6 The eggs are excreted in the feces and they become infective after passing their incubation period in the soil under the favorable circumstances of humid temperate climate,5,6 which can ensure their survival for up to one year.7 Both definitive and paratenic hosts (chickens, ruminants, pigs, etc.) can be infected via swallowing embryonated eggs in soil or raw vegetables contaminated with the feces of dogs and cats.8,9 Humans also get infected via close contact with contaminated soil or consumption of raw/undercooked meat prepared from tissues of paratenic hosts.10–12 Humans act as an accidental host and larvae do not develop into adult worms. Ingested larvae penetrate the intestinal mucosa and migrate to various organs, such as liver, lungs, heart, brain, eyes, and skeletal muscle.13–15 There are different clinical types of human toxocariasis including visceral larva migrans (VLM), ocular larva migrans (OLM), neurotoxocariasis (NT), and covert toxocariasis (CT).15