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The Parasite's Way of Life
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Do other protozoa, long believed to replicate only asexually, also at least occasionally undergo sexual reproduction? For some of these parasites, the jury is still out. To cite one such ambiguous example (see the Chapter 2 web callout on Trypanosoma cruzi for another), Trichomonas vaginalis is the sexually transmitted flagellate causing trichomoniasis in humans. Responsible for 250 million new cases of the disease annually, T. vaginalis is the most common sexually transmitted eukaryote in humans. Recent evidence, including surprisingly high within-population genetic variability, is suggestive of sexual reproduction. The observation that many genes associated with meiosis are found in the T. vaginalis genome further supports the case that this protozoan also at least occasionally reproduces sexually, or did so in its recent evolutionary past.
Infectious Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Susanna J. Dunachie, Hanif Esmail, Ruth Corrigan, Maria Dudareva
Protozoa are unicellular organisms, some of which are important pathogens of humans. They include Plasmodium, the causative organism of malaria, which is responsible for around one million deaths each year worldwide. Some protozoa have a complex life cycle that includes a vector, whereas others spread from person to person by the faecal–oral route. Many protozoa such as Leishmania and Trypanosoma are adapted to an intracellular environment (Table 3.11).
Surgery
Published in Seema Khan, Get Through, 2020
The single-celled protozoan causes gastrointestinal symptoms, in particular watery diarrhoea, flatulence, abdominal cramps and nausea. Giardiasis is spread via the faecal – oral route and most people become infected by drinking contaminated water.
The management of Babesia, amoeba and other zoonotic diseases provoked by protozoa
Published in Expert Opinion on Therapeutic Patents, 2023
Clemente Capasso, Claudiu T. Supuran
Protozoa are simple eukaryotic organisms (monocellular organisms) that are diverse of plants, animals, or fungi and can live free or as parasites of other organisms [1,2]. Fecal-oral transmissions, food or water contaminated with the feces of infected animals, and person-to-person contact are the standard modes of transmission for intestinal pathogenic protozoa [1,2]. At the same time, the bite of a mosquito or sandfly (arthropod vectors) is responsible for the spread of protozoa residing in human or animal blood (or other tissues) [3]. Many asymptomatic animals can spread protozoal infections such as babesiosis, amebiasis toxoplasmosis, Chagas’ disease, and leishmaniasis, making them particularly pernicious [4–6]. Immunocompromised persons, especially the growing number of obese and/or diabetic patients, are at a considerably risk of developing such zoonosis [5]. Thus, these frequently ignored veterinary and human diseases for which few therapeutic options are available, should be considered in more detail both for their management with the few available drugs but also in the context of designing novel anti-protozoan agents with an enhanced efficacy and less side effects [7,8].
Systemic Miltefosine as an Adjunct Treatment of Progressive Acanthamoeba Keratitis
Published in Ocular Immunology and Inflammation, 2021
Andrea Naranjo, Jaime D. Martinez, Darlene Miller, Rahul Tonk, Guillermo Amescua
Acanthamoeba keratitis (AK) is one of the most challenging infections ophthalmologists encounter in practice due to its wide range of clinical manifestations, symptoms, delayed diagnosis, and frequent lack of response to standard medical treatment.1 These challenges drive the clinical and research interest in developing novel, effective therapies for the condition. Acanthamoeba spp. are protozoa that are ubiquitous in air, soil, dust, and water.2 Its virulence factors include the secretion of multiple proteases, which help it degrade the corneal stroma and reach deep into the cornea.3 The parasite is thought to feed on keratocytes and has the ability to form cysts when facing adverse environmental challenges. The cysts constitute the dormant form of the organism which are able to survive even under nutrient deficiency and exposure to noxious injury.4 Current medical treatment for Acanthamoeba includes biguanides (polyhexamethylene biguanide (PHMB) and chlorhexidine);4 diaminides such as propamidine isethionate, dibromopropamidine, and hexamidine;5 and others such as neomycin and/or oral voriconazole.6 Steroid use still remains controversial4,7: past studies have shown that steroid treatment prior to anti-acanthamoeba therapy is detrimental,8 but more recent work has suggested that steroids, when introduced after 2 weeks of anti-amoebic treatment, may aide with discomfort without impairing outcomes.7
Functional genetic evaluation of DNA house-cleaning enzymes in the malaria parasite: dUTPase and Ap4AH are essential in Plasmodium berghei but ITPase and NDH are dispensable
Published in Expert Opinion on Therapeutic Targets, 2019
Hirdesh Kumar, Jessica Kehrer, Mirko Singer, Miriam Reinig, Jorge M. Santos, Gunnar R. Mair, Friedrich Frischknecht
Malaria is a devastating parasitic disease killing around 400,000 people every year, mostly young children. The occurrence of drug resistance and the absence of an efficient vaccine demand a better understanding of the parasite’s biology to aid the identification of suitable and novel drug and vaccine targets [1–4]. Plasmodium, the causative agent of the disease, is haploid throughout most of its life cycle. This protozoan uses multiple rounds of endomitosis followed by cellular morphogenesis to produce unicellular progeny in a process called schizogony [5]. This strategy is employed by the parasite to increase the population at specific time points during its life cycle: in the red blood cell a single P. falciparum merozoite produces up to 32 daughter cells [6]; following transmission to the mosquito an oocyst can generate hundreds of sporozoites [7] while in the liver thousands of merozoites emerge from a hepatocyte infected with a single sporozoite [8]. During sexual development, the male gametocyte produces eight motile gametes in a matter of minutes following transmission to the mosquito vector [9].