China
Africa
Explore chapters and articles related to this topic
An Introduction to Parasitism
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
In some cases, the resource provided by a host may be more in the form of a safe haven, a place in which the parasite can persist and prolong its survival, thus increasing its likelihood of transmission to a new host. Thus many parasites exploit paratenic or transport hosts in which the parasite does not undergo further or necessary development. Paratenic hosts enable the parasite to bridge a trophic gap in its life cycle, thus making transmission more probable. Chickens become infected with the nematode Heterakis gallinarum when they ingest the parasite’s eggs on the soil. In some cases, though, earthworms eat the parasite eggs and although the eggs hatch in the earthworm, the nematode larvae that emerge from the eggs do not develop further. A sojourn in the paratenic earthworm host favors Heterakis in two ways, by prolonging its survival and by being packaged in a food item delectable to chickens.
Current Status of Paragonimus and Paragonimiasis
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
Lung flukes of the genus Paragonimus are found in mammalian hosts which feed on crabs or crayfish. Paragonimiasis in man is limited in its distribution to geographic areas where food habits make infection possible. Infection usually occurs through the ingestion of raw or insufficiently cooked crabs or crayfish. Another possible mechanism of infection is an accidental transfer of the metacercariae to the mouth through the handling of infected crabs when preparing them for crab soup or crab cake.8,9 Infection also occurs by eating the flesh of the paratenic hosts. This might be a factor in the natural infection of some of the larger carnivorous animals, such as the tiger. Recently, it was found that an outbreak of human paragonimiasis which occurred in Japan was due to the ingestion of raw flesh of wild boar that served as a paratenic host of P. westermani2 Regarding symptomatology, pulmonary paragonimiasis is usually insidious in its onset. There may be no symptoms other than occasional coughing up of rusty sputum. Survey and clinical studies of groups of individuals indicate that in most of the endemic areas of paragonimiasis, the majority of the infections are light or moderate, and the physical examinations of the patients are characterized by a healthy appearance, despite a history of cough and bloody sputum for years.
Paragonimus
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Pham Ngoc Doanh, Haruhiko Maruyama, David Blair, Yukifumi Nawa
Several species of Paragonimus exploit paratenic hosts, commonly rodents. Some birds (hens, ducks, and geese) have been reported as experimental paratenic hosts.1 Consumption of paratenic hosts is probably the route by which infection occurs in large carnivores.33 The role of wild boars as paratenic hosts and as a cause of human paragonimiasis was demonstrated in Japan.34 Surprisingly, human paragonimiasis cases due to consumption of shika-sashi, a venison version of sashimi, have also been reported in Japan.35,36 Living P. westermani juveniles were isolated from muscles of a sika deer, Cervus nippon, in Kagoshima Prefecture, Japan.37 Yoshida et al. indicated that the overall contribution of raw venison consumption to the occurrence of paragonimiasis infection in Japan was estimated to be around 10%–20% in some highly endemic areas.38 Presumably, herbivorous sika deer do not seek freshwater crabs for food, they just accidentally intake crabs with grass near marshes. This suggests that other herbivorous animals can serve as paratenic hosts of Paragonimus species. Eating raw meat of any animals in Paragonimus-endemic areas should be avoided.
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
Clinical Profile, Treatment, and Visual Outcome of Ocular Toxocara in a Tertiary Eye Care Centre
Published in Ocular Immunology and Inflammation, 2018
Ekta S. Sahu, Bikramjit Pal, Tarun Sharma, Jyotirmay Biswas
Helminthozoonoses are important public health issues in many tropical and subtropical countries, mainly in the developing world. The Tropic of Cancer passes through the middle of India and provides warm weather for most of the year throughout the country. The current study was performed in Chennai, which is situated on the south-east coast of India, which has a hot and humid climate, whereas the northernmost part of country, being hilly, is warm and occasionally cool. The optimal temperature and humidity provide an appropriate environment for nurturing the eggs of T. canis into infective embryonated eggs manifesting as disease in paratenic hosts.