RESUMO
BACKGROUND: Soil-transmitted helminths (STHs) comprise a group of helminth parasites that are included in the list of Neglected Tropical Diseases and require a passage through the soil to become infective. Several studies have detected that infection with STHs are associated with certain socioeconomic, environmental and soil characteristics. In Argentina, the presence of these parasites has been detected through a few point studies conducted in localities from 11 of the 23 provinces that comprise the country. METHODS/PRINCIPAL FINDINGS: The most important characteristics previously associated with the presence of STHs were identified and ranked through the use of an expert survey and the Analytical Hierarchy Process (AHP) in order to construct a risk map of STHs specific for Argentina. Prevalence data from previous studies was used to validate the generated risk map. The map shows that half of Argentina, from the Central provinces to the North, contains localities with the characteristics necessary for the development of these parasites. CONCLUSIONS/SIGNIFICANCE: The predicted map should serve as a useful tool for guiding the identification of survey areas for the generation of baseline data, detecting hotspots of infection, planning and prioritizing areas for control interventions, and eventually performing post-implementation surveillance activities.
Assuntos
Helmintíase/epidemiologia , Helmintíase/transmissão , Solo/parasitologia , Argentina/epidemiologia , Humanos , Prevalência , Fatores de RiscoRESUMO
BACKGROUND: Due to the recent increased use of the McMaster (MM) fecal egg counting method for assessing benzimidazole drug efficacy for treating soil-transmitted helminth (STH) infections, the aim of the current study was to determine the operational value of including the MM method alongside the Kato-Katz (KK) fecal thick smear to increase the diagnostic sensitivity when STHs are co-endemic with trematode helminths (e.g., Schistosoma mansoni). METHODS: A cross-sectional study was conducted in school-aged children aged 4-18 years in the northeastern region of the State of Minas Gerais (Brazil), where Necator americanus, Ascaris lumbricoides, Trichuris trichiura, and S. mansoni are co-endemic. One fecal sample from each participant was collected and transported to the field laboratory for analysis. Coprological diagnosis was performed on each fecal sample by three different methods: Formalin-Ether Sedimentation (FES), KK and the MM technique. The diagnostic sensitivity and negative predictive value (NPV) of each technique was calculated using the combination of all three techniques as the composite standard. In order to determine the agreement between the three techniques Fleiss´ kappa was used. Both the Cure Rate (CR) and the Fecal Egg Count Reduction (FECR) were calculated using the two quantification techniques (i.e., the MM and KK). RESULTS: Fecal samples from 1260 children were analyzed. The KK had higher diagnostic sensitivity than the MM for the detection of both A. lumbricoides (KK 97.3%, MM 69.5%) and hookworm (KK 95.1%, MM 80.8%). The CR of a single dose of mebendazole varied significantly between the KK and MM for both A. lumbricoides (p = 0.016) and hookworm (p = 0.000), with lower rates obtained with the KK. On the other hand, the FECR was very similar between both techniques for both A. lumbricoides and hookworm. CONCLUSION: The MM did not add any diagnostic value over the KK in areas where both STHs and trematodes were co-endemic. The lower sensitivity of the MM would have an important impact on the administration of selective school-based treatment in this area since if only the MM were used, 36 (13.9%) children diagnosed with A. lumbricoides would have gone untreated.
Assuntos
Helmintíase/diagnóstico , Solo/parasitologia , Adolescente , Brasil/epidemiologia , Criança , Pré-Escolar , Estudos Transversais , Doenças Endêmicas , Fezes/parasitologia , Feminino , Helmintíase/epidemiologia , Helmintíase/parasitologia , Helmintíase/transmissão , Humanos , Masculino , Contagem de Ovos de Parasitas/métodos , PrevalênciaRESUMO
BACKGROUND: Robust reference values for fecal egg count reduction (FECR) rates of the most widely used anthelmintic drugs in preventive chemotherapy (PC) programs for controlling soil-transmitted helminths (STHs; Ascaris lumbricoides, Trichuris trichiura, and hookworm) are still lacking. However, they are urgently needed to ensure detection of reduced efficacies that are predicted to occur due to growing drug pressure. Here, using a standardized methodology, we assessed the FECR rate of a single oral dose of mebendazole (MEB; 500 mg) against STHs in six trials in school children in different locations around the world. Our results are compared with those previously obtained for similarly conducted trials of a single oral dose of albendazole (ALB; 400 mg). METHODOLOGY: The efficacy of MEB, as assessed by FECR, was determined in six trials involving 5,830 school children in Brazil, Cambodia, Cameroon, Ethiopia, United Republic of Tanzania, and Vietnam. The efficacy of MEB was compared to that of ALB as previously assessed in 8,841 school children in India and all the above-mentioned study sites, using identical methodologies. PRINCIPAL FINDINGS: The estimated FECR rate [95% confidence interval] of MEB was highest for A. lumbricoides (97.6% [95.8; 99.5]), followed by hookworm (79.6% [71.0; 88.3]). For T. trichiura, the estimated FECR rate was 63.1% [51.6; 74.6]. Compared to MEB, ALB was significantly more efficacious against hookworm (96.2% [91.1; 100], p<0.001) and only marginally, although significantly, better against A. lumbricoides infections (99.9% [99.0; 100], pâ=â0.012), but equally efficacious for T. trichiura infections (64.5% [44.4; 84.7], pâ=â0.906). CONCLUSIONS/SIGNIFICANCE: A minimum FECR rate of 95% for A. lumbricoides, 70% for hookworm, and 50% for T. trichiura is expected in MEB-dependent PC programs. Lower FECR results may indicate the development of potential drug resistance.
Assuntos
Anti-Helmínticos/farmacologia , Doenças Endêmicas , Helmintíase/tratamento farmacológico , Helmintos/efeitos dos fármacos , Mebendazol/farmacologia , Adolescente , Albendazol/farmacologia , Albendazol/uso terapêutico , Animais , Anti-Helmínticos/uso terapêutico , Brasil , Camboja , Camarões , Criança , Pré-Escolar , Doenças Endêmicas/prevenção & controle , Etiópia , Fezes/parasitologia , Feminino , Helmintíase/prevenção & controle , Humanos , Masculino , Mebendazol/uso terapêutico , Contagem de Ovos de Parasitas , Solo/parasitologia , Tanzânia , Resultado do Tratamento , VietnãRESUMO
Hookworm disease from Necator americanus and Ancylostoma duodenale affects approximately 700 million people, with N. americanus being the predominant species. Unlike other pathogens (e.g., bacterial infections), where "virulence" is described in regards to acute pathogenesis and case-fatality, hookworms are well-evolved, multicellular parasites that establish long-term infections in their human hosts with a subtle and chronic, but insidious, pathogenesis, usually in the form of iron deficiency anemia from parasite blood feeding that, over time, has devastating effects on the human host especially when it involves children or women of child bearing years. As such, many of the typical terms for "virulence factors" used in other reviews in this special edition cannot be applied to hookworm (e.g., "colonization", "invasion", "or "toxicity"); rather the virulence of hookworm infection comes in terms of their ability to maintain a chronic blood-feeding infection in the lumen of relatively healthy human hosts, an infection that is usually measured in years but can sometimes be measured in decades. In the current manuscript, we describe the routes of invasion hookworms take into their human hosts and the means by which they modulate the human immune system to maintain this long-term parasitism. Little data on hookworm infection comes from actual human infections; instead, much of the data is derived from observations of laboratory animal models, in which hookworms fail to establish this distinctive "chronic infection," either due to physiological or immunological responses of these animal models. Hence, the mode and effects of chronic immunity must be extrapolated from this very different sort of infection to humans. Herein, we aim to synthesize immunological information from both types of models in the context of immune regulation and protection in order to identify future research focuses for the development of new treatment alternatives (i.e. drugs and vaccines).
Assuntos
Ancylostomatoidea/patogenicidade , Infecções por Uncinaria/parasitologia , Fatores de Virulência/fisiologia , Animais , Interações Hospedeiro-Parasita , HumanosRESUMO
BACKGROUND: The Kato-Katz thick smear (Kato-Katz) is the diagnostic method recommended for monitoring large-scale treatment programs implemented for the control of soil-transmitted helminths (STH) in public health, yet it is difficult to standardize. A promising alternative is the McMaster egg counting method (McMaster), commonly used in veterinary parasitology, but rarely so for the detection of STH in human stool. METHODOLOGY/PRINCIPAL FINDINGS: The Kato-Katz and McMaster methods were compared for the detection of STH in 1,543 subjects resident in five countries across Africa, Asia and South America. The consistency of the performance of both methods in different trials, the validity of the fixed multiplication factor employed in the Kato-Katz method and the accuracy of these methods for estimating 'true' drug efficacies were assessed. The Kato-Katz method detected significantly more Ascaris lumbricoides infections (88.1% vs. 75.6%, p<0.001), whereas the difference in sensitivity between the two methods was non-significant for hookworm (78.3% vs. 72.4%) and Trichuris trichiura (82.6% vs. 80.3%). The sensitivity of the methods varied significantly across trials and magnitude of fecal egg counts (FEC). Quantitative comparison revealed a significant correlation (Rs >0.32) in FEC between both methods, and indicated no significant difference in FEC, except for A. lumbricoides, where the Kato-Katz resulted in significantly higher FEC (14,197 eggs per gram of stool (EPG) vs. 5,982 EPG). For the Kato-Katz, the fixed multiplication factor resulted in significantly higher FEC than the multiplication factor adjusted for mass of feces examined for A. lumbricoides (16,538 EPG vs. 15,396 EPG) and T. trichiura (1,490 EPG vs. 1,363 EPG), but not for hookworm. The McMaster provided more accurate efficacy results (absolute difference to 'true' drug efficacy: 1.7% vs. 4.5%). CONCLUSIONS/SIGNIFICANCE: The McMaster is an alternative method for monitoring large-scale treatment programs. It is a robust (accurate multiplication factor) and accurate (reliable efficacy results) method, which can be easily standardized.