Implications of asymptomatic infection for the natural history of selected parasitic tropical diseases

Abstract

Progress has been made in the control or elimination of tropical diseases, with a significant reduction of incidence. However, there is a risk of re-emergence if the factors fueling transmission are not dealt with. Although it is essential to understand these underlying factors for each disease, asymptomatic carriers are a common element that may promote resurgence; their impact in terms of proportion in the population and role in transmission needs to be determined. In this paper, we review the current evidence on whether or not to treat asymptomatic carriers given the relevance of their role in the transmission of a specific disease, the efficacy and toxicity of existing drugs, the Public Health interest, and the benefit at an individual level, for example, in Chagas disease, to prevent irreversible organ damage. In the absence of other control tools such as vaccines, there is a need for safer drugs with good risk/benefit profiles in order to change the paradigm so that it addresses the complete infectious process beyond manifest disease to include treatment of non-symptomatic infected persons.

Identification of Leishmania infantum in blood donors from endemic regions for visceral leishmaniasis

“…remains challenging, highlighting the need for a solution and evaluation of the different tools available (Pereira et al, 2014). To find a test that could better identify these individuals, as there is still no universally accepted gold standard for such cases (Alvar et al, 2020), our research group chose the available modern molecular biology techniques as tools. The molecular method of qPCR was selected because it has displayed better sensitivity and specificity than serological tests and other techniques (Reithinger and Dujardin, 2007;Ruiter et al, 2014;.…”

“…Asymptomatic individuals, especially those from endemic areas, show an immune response (production of specific antibodies or cellular) against Leishmania infantum ( L. infantum ) or presence of parasitic DNA in the peripheral blood, but remain healthy, without clinical presentation of the characteristic symptoms of the disease (Alvar et al ., 2020).…”

Trends of Seroprevalence of Chagas´s diseases in healthy blood donors, solid organ donors and heart transplant recipients: experience of a single health care center in Colombia.

“…As limitations, it can be said that the seroprevalence found in this study does not represent the real risk of transmission by these mechanisms, but confirms the importance of continuing to screen infection in organ transplant and blood donation. It is to be considered that 70–80% of those infected will develop indeterminate forms of the disease and will behave as reservoirs of the parasite [7, 28]. In addition, in the complex context of a transplant, complete information on epidemiological history may not be available at the time of donation, especially in the case of post-mortem donors.…”

“…The Americas region has the highest concentration of cases, especially in countries such as Colombia, where it is endemic [1][2][3][4]. Although in recent years the infection prevalence in the country has remained close to 1% thanks to vector control measures, it is considered to be re-emerging due to the constant migration of individuals who develop indeterminate forms of the infection and serve as parasite reservoirs [5][6][7][8].…”

Trypanosoma brucei gambiense-iELISA: A Promising New Test for the Post-Elimination Monitoring of Human African Trypanosomiasis

“…However, as long as tsetse populations subsist, gHAT may reappear in foci that are considered eliminated. Re-emergence of the disease may be caused by i) an animal reservoir, although the epidemiological role of animals is still under debate or ii) a human reservoir in the form of patients that are not picked up by active or passive surveys or asymptomatic carriers that harbour the infection for years or decades without developing the disease [7][8][9].…”