Predisposition to ascariasis: patterns, mechanisms and implications

Abstract

Ascaris lumbricoides, the human roundworm, is a remarkably infectious and persistent parasite. It is a member of the soiltransmitted helminths or geohelminths and infects in the order of 1472 million people worldwide. Despite, its high prevalence and wide distribution it remains along with its geohelminth counterparts, a neglected disease. Ascariasis is associated with both chronic and acute morbidity, particularly in growing children, and the level of morbidity assessed as disability-adjusted life years is about 10 . 5 million. Like other macroparasite infections, the frequency distribution of A. lumbricoides is aggregated or overdispersed with most hosts harbouring few or no worms and a small proportion harbouring very heavy infections. Furthermore, after chemotherapeutic treatment, individuals demonstrate consistency in the pattern of re-infection with ascariasis, described as predisposition. These epidemiological phenomena have been identified, in a consistent manner, from a range of geographical locations in both children and adults. However, what has proved to be much more refractory to investigation has been the mechanisms that contribute to the observed epidemiological patterns. Parallel observations utilizing human subjects and appropriate animal model systems are essential to our understanding of the mechanisms underlying susceptibility/resistance to ascariasis. Furthermore, these patterns of Ascaris intensity and re-infection have broader implications with respect to helminth control and interactions with other important bystander infections.

Effect of Deworming on Indices of Health, Cognition, and Education Among Schoolchildren in Rural China: A Cluster-Randomized Controlled Trial

“…The pattern of rapid reinfection after antihelminthic treatment (in our case, we tested the follow-up fecal samples 6 months after treatment) has been consistently identified in geographically diverse populations in both children and adults, 46 and was previously confirmed in our study area. 8,25 In our scenario, we surmise that children in the intervention group were cleared of STH infection after each of the two rounds of antihelminthic treatment, but experienced high rates of reinfection within the subsequent months leading up to postintervention evaluation.…”

Heavy metal intoxication compromises the host cytokine response inAscaris Suummodel infection

“…Reduced number of A. suum larvae in mice intoxicated with Cd suggests the importance of IFN-γ in larval destruction through macrophage activation (Jalčová & Dvorožnáková, 2014). We suppose that early stimulation of IFN-γ production activated hepatic infl ammatory mechanisms what contributed to the anti-parasite protection where hepatic/post-hepatic factors in protection against larval Ascaris migration from the liver to the lungs are also involved (Lewis et al, 2007;Holland, 2009). The protective immune response against the gastrointestinal helminths is characterized by Th2 response.…”

“…Nevertheless mercury pollution can also decrease parasitism but this was probably caused by the host physiological status, when weak and cachectic mice organisms with mixed Th2/Th1 cytokine production were not able to offer good conditions for the development of parasite infection. Heavily infected hosts are likely to suffer greater morbidity and mortality what make a greater presence of infective stages in the environment (Holland, 2009). Our results suggest the different effects of particular heavy metals on parasite host status in the polluted areas and on different risks of parasite infection depending on heavy metal pollution.…”

Geography of ascariasis in Belarus: cultural and anthropological aspectys (Part 2)

“…На сегодняшний день нет убедительных данных об отличиях в распространенности аскаридоза у представителей различных этнических групп на территории Европы, в то же время, неоднократно высказывалось мнение о существовании определённой предрасположенности к поражённости аскаридозом в различных популяционных группах [12,[15][16][17]. При этом в качестве потенциальных причин чаще рассматриваются отличительные генетические и иммунофизиологические характеристики.…”