Beneficial Use of Viruses
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
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.
An Introduction to Parasitism
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
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
Max J. Miller, E. J. Love in 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.
Parasitic infections of the gut in children
Published in Paediatrics and International Child Health, 2019
Parasitic infections of the gut are responsible for a very large burden of morbidity and mortality in tropical and low- and middle-income countries (LMIC). These infectious diseases, however, are not confined to LMIC. Cryptosporidiosis, for example, has caused massive outbreaks in the USA, and giardiasis is also globally distributed. Strictly speaking, a parasite is merely an organism which lives on or in another organism without conferring any benefit to the host, and usually to its disadvantage. In common medical usage, however, the term ‘parasite’ refers to protozoa, helminths or insects rather than bacteria or viruses. This article also includes some recognised fungal infections of the gut. Only the most important parasites are described, and for less prevalent pathogens more detailed articles should be consulted [1–3]. Life cycles and detailed parasitological descriptions will not be given here.
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
How could we forget immunometabolism in SARS-CoV2 infection or COVID-19?
Published in International Reviews of Immunology, 2021
The evolution of SARS-CoV2 is not clear yet. Either SARS-CoV2 has evolved in bats, itself under different host or environmental pressure capable of inducing genetic recombination events or specific mutations. Or it has entered the secondary reservoir through the food chain, for example, the horseshoe bats may have transferred the virus to secondary hosts while feeding on their blood or the secondary hosts have prayed on these bats. However, we still do not know the exact secondary host from which the infection has transferred to humans. But human to human transfer of the SARS-CoV2 has led to the induction of COVID-19 pandemic. The author has discussed the mysteries of SARS-CoV2 evolution and its transfer to humans somewhere else [9]. A recent study has indicated the transfer of SARS-CoV2 to farmed minks (Neovison vison) in a farm from humans that evolved in them and re-infected human population working there [10]. Hence, humans can transfer the SARS-CoV2 to other animals and can get back the infection. Type 1 interferons (IFNs) exert more potent antiviral action against SARS-CoV2 as compared to the SARS-CoV [11]. Thus to avoid this antiviral immune response SARS-CoV2 has developed different strategies to block the type 1 IFN generation, which are described by the author somewhere else [9].