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Parasite Versus Host: Pathology and Disease
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
As parasites migrate, develop, feed or reproduce, there are often damaging consequences for the host. Some of these changes are purely mechanical. The intestinal obstruction that can occur during an A. lumbricoides infection is an example. Mechanical insult is also behind some of the pathology caused by Taenia solium or Echinococcus spp. Like other tapeworms, both of these cestodes form cyst-like structures (see Section 3.3) in the tissues or organs of their intermediate hosts. These cysts can be quite large—large enough to impinge upon and damage adjacent tissue and organs. In the case of T. solium, the observed symptoms and severity of disease vary with the location, number and size of the tissue cysts (known as cysticerci). As the site of encystation is often the central nervous system, symptoms often include headaches, vision problems, dizziness and seizures. Occasionally, pressure exerted by the cyst leads to disturbance of cerebrospinal fluid circulation, which can cause dementia.
Neuroinfectious Diseases
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Jeremy D. Young, Jesica A. Herrick, Scott Borgetti
While in the vesicular stage, the parasite actively evades the host immune system via multiple mechanisms. Symptom onset begins when cysticerci can no longer evade the host immune response, signaled by lesions in the degenerating (nodular or colloidal) stages. These lesions typically enhance on contrast imaging and are frequently surrounded by perilesional edema.5 Cysts in this stage may leak antigenic material that induces an inflammatory response with subsequent cerebritis, ventriculitis, meningitis, and seizures.
Prospects for Vaccination Against Larval Cestode Infections
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
Resistance to challenge infection plays a central role in controlling the natural transmission of larval taeniid cestodes.1 Studies carried out in New Zealand during regional control campaigns for ovine cysticercosis due to Taenia ovis infection have highlighted the importance of immunity.2 Treatment of all dogs every 6 weeks to remove adult tapeworms substantially reduced the numbers of T. ovis cysticerci found in lambs killed in abattoirs. However, the reduced contamination of pasture resulted in a population of sheep with no immunity derived from natural infection, so that when an infected dog entered a “clean” district, severe outbreaks of cysticercosis occurred in the susceptible sheep in areas up to 30,000 ha around the focus of contamination. Because of the prolific egg production of all Taenia spp. in both man and animals, a vaccine to replace immunity conferred by natural infection is necessary to enable effective control of these parasites.
Taenia solium taeniasis/cysticercosis in Guatemala: a prevalent public health problem?
Published in Pathogens and Global Health, 2023
Roderico David Hernández-Chea, Paola Morales-Ramírez, Marisela Hernández, Andrea Toledo, Alejandro Hun, Edda Sciutto, Agnès Fleury
The life cycle of Taenia solium requires two hosts: humans, the only definitive host of the adult tapeworm, and pigs, the intermediate host of the larval stage, known as cysticerci [1]. Humans acquire T. solium infection (taeniasis) by ingesting raw or undercooked pork containing viable cysticerci. Pigs become infected (porcine cysticercosis) by ingesting viable T. solium eggs found in the feces of human tapeworm carriers. In humans, cysticercosis occurs when T. solium eggs are accidentally ingested; after hatching from the egg, the larval stage is lodged in various organs and tissues (brain, eyes, muscles, and subcutaneous tissue) [2]. Neurocysticercosis (NCC), a common cause of epilepsy, occurs when cysticerci are located in the central nervous system (CNS) [2]. Human cysticercosis is a major public health problem and results in economic losses in low-income areas of Latin America, Africa, and Asia, where poor sanitary conditions, poor hygiene, open defecation practices, free-roaming pigs, and poverty prevail [3,4]. According to the World Health Organization, cysticercosis was the leading cause of death out of all foodborne parasitic diseases in 2015, resulting in 2.8 million disability-adjusted life years (DALYs). It is also the leading cause of late-onset epilepsy in developing countries [5].
Inflammation in neurocysticercosis: clinical relevance and impact on treatment decisions
Published in Expert Review of Anti-infective Therapy, 2021
Pedro T Hamamoto Filho, Gladis Fragoso, Edda Sciutto, Agnès Fleury
When parasites are located in the subarachnoid compartment, lower levels of Th1/Th2 cytokines in periphery are found compared to the parenchymal presentation. These levels are as low that resemble to those from non-infected subjects. However, a stronger regulatory immune response is achieved when cells are stimulated with parasite antigens in vitro [44], a result that is in accordance with the increased levels of regulatory cytokines found in the CSF. Also, an increased number of CD4+/CD25 Treg cells without previous specific stimulation has also been observed in the periphery, closely correlating with the increased number of these cells in the CSF [46]. In contrast to P-NC, in EP-NC it is apparently rare for cysticerci to be damaged as part of the natural course of the disease, and the destruction generally requires cysticidal treatment [47]. In the CSF, increased levels of different pro-inflammatory cytokines, such as IL-6 and IL-1 [45,48] and Th1/Th2 cytokines and chemokines, such as IFNγ, IL-12p70, CXCL-10/IL-10, and IL-13 [49], have been reported. The increased levels of IL-10 and TGFβ may counteract the effect of inflammatory cytokines [50]. Moreover, this inflammatory profile is associated with an increase in the central number of Treg cells and a decrease in the number of CD4 and CD8 activated T cells [51]. This apparently tightly regulated response is accompanied by different degrees of disease severity, directly related to the degree of CSF inflammatory response.
Vaccine for a neglected tropical disease Taenia solium cysticercosis: fight for eradication against all odds
Published in Expert Review of Vaccines, 2021
Rimanpreet Kaur, Naina Arora, Suraj S Rawat, Anand Kumar Keshri, Shubha Rani Sharma, Amit Mishra, Gagandeep Singh, Amit Prasad
In a very early attempt to look for vaccination against taenia, nine piglets were infected with cysticercosis at the age of 2 months and four of them were challenged again after 2 months of the first infection. At the time of autopsy, the re-infected piglets had fewer cysticerci [33]. Although this experiment was crude in nature but has established that primoinfection accelerated cysticerci degeneration, it induced some degree of protection and vaccination of pigs against Taenia infection is possible. Later, it was found that the resistance developed by infecting pigs for cysticerci infection lasted for five months only [34], suggesting that deliberate re-infection is not a sustainable vaccination strategy. But this study opened the field for the development of a vaccine for this purpose and eventually lead to the development of some reliable and commercially available vaccines [35,36]. The different immunization techniques and proteins/peptides applied for pig vaccinations are discussed below and the same is depicted in Figure 2. Later, several vaccines for pig/mice have shown tremendous potential with acceptable efficacy. The list of antigens used as candidate vaccines along with their origin and route of administration and efficacy is given in Table 2.