Outbreak of Entamoeba histolytica and Giardia lamblia infections in travellers returning from the tropics

Review of zoonotic amebiasis: Epidemiology, clinical signs, diagnosis, treatment, prevention and control

Amebiasis is a disease caused by the protozoan parasite Entamoeba histolytica, which mainly shows symptoms of acute diarrhea, dysentery, amebic colitis, and amebic liver abscesses. As the fourth leading parasitic cause of human mortality, E. histolytica mainly infect children in developing countries, transmitted by food and water contamination. In the majority of infected individuals, Entamoeba sp. asymptomatically colonizes the large intestine and self-limiting, while in others, the parasite breaches the mucosal epithelial barrier to cause amebic colitis and can disseminate to soft organs to cause abscesses. Metronidazole (MTZ) is the recommended and most widely used drug for treating the invasive amebiasis. No amebiasis vaccine has been approved for human clinical trials to date, but many recent vaccine development studies hold promise. For the prevention and control of amebiasis, improvement of water purification systems and hygiene practices could decrease disease incidence. In this review, we focus on the epidemiology, transmission, clinical signs, pathogenesis, diagnosis, treatment, prevention and control of the zoonotic amebiasis.

Giardia duodenalis in the UK: current knowledge of risk factors and public health implications

Giardia duodenalis is a ubiquitous flagellated protozoan parasite known to cause giardiasis throughout the world. Potential transmission vehicles for this zoonotic parasite are both water and food sources. As such consumption of water contaminated by feces, or food sources washed in contaminated water containing parasite cysts, may result in outbreaks. This creates local public health risks which can potentially cause widespread infection and long-term post-infection sequelae. This paper provides an up-to-date overview of G. duodenalis assemblages, sub-assemblages, hosts and locations identified. It also summarizes knowledge of potential infection/transmission routes covering water, food, person-to-person infection and zoonotic transmission from livestock and companion animals. Public health implications focused within the UK, based on epidemiological data, are discussed and recommendations for essential Giardia developments are highlighted.

Entamoeba histolytica under Oxidative Stress: What Countermeasure Mechanisms Are in Place?

Entamoeba histolytica is the causative agent of human amoebiasis; it affects 50 million people worldwide and causes approximately 100,000 deaths per year. Entamoeba histolytica is an anaerobic parasite that is primarily found in the colon; however, for unknown reasons, it can become invasive, breaching the gut barrier and migrating toward the liver causing amoebic liver abscesses. During the invasive process, it must maintain intracellular hypoxia within the oxygenated human tissues and cellular homeostasis during the host immune defense attack when it is confronted with nitric oxide and reactive oxygen species. But how? This review will address the described and potential mechanisms available to counter the oxidative stress generated during invasion and the possible role that E. histolytica’s continuous endoplasmic reticulum (Eh-ER) plays during these events.

[Intestinal parasitoses in Argentina: major causal agents found in the population and in the environment]

Intestinal parasitic diseases are widely spread in the world, with the highest prevalence in developing countries. Children are mainly affected, showing a decrease in physical and mental development, as well as the expected manifestations of the disease. This situation can be greatly enhanced in children with poor nutritional status. The World Health Organization considers intestinal parasitic diseases a major cause of morbidity, closely linked to poverty and poor personal hygiene, inappropriate handling of raw food, lack of sanitation, lack of potable water supply, and environmental fecal contamination. Some parasitic diseases are cosmopolitan while others have variable geographic distribution, due to different factors such as the presence of exclusive intermediate hosts. In the past few years, globalization allowed the spread of certain parasites from endemic to non-endemic regions. Even though people's customs influence on the frequency of certain parasites, environmental conditions are a determinant factor for parasite survival. In our country, due to the variety of soils and climatic conditions, several causative agents of these parasitoses can be found. The aim of this work was to review the literature on the intestinal parasitic agents found in Argentina in human fecal samples and its environment, as parasitic contamination constitutes a direct indicator of the infection risk by intestinal parasites.

Evaluation of a real-time polymerase chain reaction assay for the laboratory diagnosis of giardiasis

A real-time polymerase chain reaction (PCR) assay was evaluated in comparison with the combination of conventional methods (microscopic examination and antigen detection assay) during the period 2006 to 2008 on 771 fecal samples belonging to 386 patients to assess its usefulness for an accurate laboratory diagnosis of giardiasis. The real-time PCR assay detected Giardia intestinalis DNA in 195 samples (106 patients), including 26 samples (21 patients) negative by the conventional assays. Among the 21 patients, in 8 cases, giardiasis was previously diagnosed also by conventional methods in additional samples of the same patients, whereas in 13, it would have been undiagnosed if real-time PCR assay was not used. The real-time PCR assay demonstrated a detection limit of 2 cysts per reaction and 100% specificity and sensitivity compared to conventional methods. A genotype analysis targeting the beta-giardin gene allowed to identify 53 samples (23 patients) containing genotype A and 59 samples (45 patients) containing genotype B.

Enteroparasitosis and their ethnographic relationship to food handlers in a tourist and economic center in Paraná, Southern Brazil

This study reports on the occurrence of enteroparasites based on data from an ethnographic study of food handlers in the city of Cascavel, Paraná, Brazil. Fecal material from 343 food handlers of both sexes, between 14 and 75 years of age, was analyzed using Lutz, modified Ritchie and Ziehl-Neelsen techniques. Ethnographic relationships were investigated by means of specific questionnaires. Positive fecal samples were found for 131 (38.2%) handlers. Endolimax nana (67.9%) was the predominant species, followed by Entamoeba coli (35.9%), Blastocystis hominis (28.2%), Entamoeba histolytica/dispar (10.1%) and Giardia duodenalis (8.4%). Protozoan infections were more common than helminth infections (p = 0.00). The positive results for some parasites were associated with the male sex, professional category, and the performance of other activities (p < 0.05). The high overall occurrence of enteroparasites found indicates improper hygiene and sanitation conditions. Effective educational measures should be implemented to prevent the transfer of pathogenic organisms to food via handling.

Jones J. Survey of obstetrician-gynecologists about giardiasis

Giardiasis is one of the most common parasitic diseases in the United States with over 15 400 cases reported in 2005. A survey was conducted by The American College of Obstetricians and Gynecologists (ACOG) in collaboration with the Centers for Disease Control and Prevention (CDC) to evaluate the knowledge of obstetricians and gynecologists regarding the diagnosis and treatment of giardiasis. The questionnaire was distributed to a random sample of 1200 ACOG fellows during February through June of 2006. Five hundred and two (42%) responded to the survey. The respondents showed good general knowledge about diagnosis, transmission, and prevention; however, there was some uncertainty about the treatment of giardiasis and which medications are the safest to administer during the first trimester of pregnancy.

Giardia and Cryptosporidium and public health: the epidemiological scenario from the Italian perspective

Giardia and Cryptosporidium spp. are protozoa that cause human and animal disease worldwide and often exhibit zoonotic transmission. This review gives ample information concerning the epidemiology of these parasites in Italy, i.e. prevalence data in humans, farm and pet animals, shellfish and aquatic environment. Moreover, it reports genotyping results obtained from different isolates, with particular emphasis on the spread of host-specific and zoonotic species/genotypes of various origin, and on molecular data that make the Italian situation different from that of other countries. Finally, possible explanations are given for the infrequent reports of Giardia and Cryptosporidium spp. outbreaks, despite widespread faecal contamination by these parasites.

Enteroparasitoses e onicomicoses em manipuladores de alimentos do município de Ribeirão Preto, SP, Brasil

A maioria das doenças veiculadas por alimentos de origem microbiana deve-se à manipulação inadequada dos mesmos. A identificação de manipuladores de alimentos portadores de agentes patogênicos que podem ser propagados para os alimentos é uma ferramenta útil na prevenção da contaminação dos mesmos. OBJETIVOS: Identificar a presença de enteroparasitoses e onicomicoses em manipuladores de alimentos de Ribeirão Preto, contribuindo assim com as ações de vigilância sanitária. MÉTODOS: Foram analisadas entre julho e novembro de 2000, 69 amostras de fezes e 23 de unhas de 23 manipuladores de alimentos de Ribeirão Preto. As fezes foram submetidas aos métodos de KATO e da sedimentação espontânea. Na análise micológica, cada amostra de raspado de unha foi submetida à clarificação com KOH 30% por 30 minutos para estudo microscópico (exame direto) e cultura em ágar Sabouraud acrescido de 100 mg/L de cloranfenicol e posterior incubação a 28(0) - 30(0)C por até 30 dias, verificando-se o crescimento semanalmente. RESULTADOS: Dos trabalhadores avaliados, 04 (17,4%) apresentaram parasitismo intestinal, 08 (34,8%) micoses e em 01 (4,3%) foi constatada infecção concomitante por enteroparasitas e micose. CONCLUSÕES: Para evitar as doenças transmitidas por alimentos é necessária a implementação conjunta de várias ações, incluindo a identificação dos portadores de agentes patogênicos que possam ser propagados para os alimentos através da manipulação.

Freezing: an underutilized food safety technology?

Freezing is an ancient technology for preserving foods. Freezing halts the activities of spoilage microorganisms in and on foods and can preserve some microorganisms for long periods of time. Frozen foods have an excellent overall safety record. The few outbreaks of food-borne illness associated with frozen foods indicate that some, but not all human pathogens are killed by commercial freezing processes. Freezing kills microorganisms by physical and chemical effects and possibly through induced genetic changes. Research is needed to better understand the physical and chemical interactions of various food matrices with the microbial cell during freezing and holding at frozen temperatures. The literature suggests that many pathogenic microorganisms may be sublethally injured by freezing, so research should be done to determine how to prevent injured cells from resuscitating and becoming infectious. Studies on the genetics of microbial stress suggest that the induction of resistance to specific stresses may be counteracted by, for example, simple chemicals. Research is needed to better understand how resistance to the lethal effect of freezing is induced in human pathogens and means by which it can be counteracted in specific foods. Through research, it seems possible that freezing may in the future be used to reliably reduce populations of food-borne pathogens as well as to preserve foods.

A political asylum seeker with an amoebic empyema in Birmingham

A previously well 21-year-old male non-smoker from Afghanistan was admitted with a 5- week history of right-sided pleuritic chest pain, weight loss, fever and night sweats. Two days before admission he developed a productive cough with frank haemoptyses. He had arrived into the UK 6 months previously as a political asylum seeker. On examination, he was unwell with an oral temperature of 39.0°C and tachypnoeic at 20 breaths per minute. Respiratory examination revealed signs consistent with a right basal consolidation and an effusion. Cardiovascular and abdominal examinations were unremarkable.

The microbiological quality of ice used to cool drinks and ready-to-eat food from retail and catering premises in the United Kingdom

A survey of 4,346 samples of ice from retail and catering premises examined 3,528 samples (81%) used to cool drinks and 144 samples (3%) from food displays. For 674 samples (15%), the origin was not recorded. Most samples of ice used to cool drinks or ready-to-eat food on displays did not contain coliforms, Escherichia coli, or enterococci. Of the ice used to cool drinks, 9% contained coliforms, 1% E. coli, and 1% enterococci in excess of 10(2) CFU/100 ml, and 11% had an aerobic plate count at 37 degrees C in excess of 10(3) CFU/ml. The microbiological quality of ice used to cool drinks was poorer when melt water was present in the ice buckets. Ice used in food displays was more contaminated than ice used to cool drinks, with 23% containing coliforms, 5% E. coli, and 8% enterococci at 10(2) CFU/100 ml or more. Twenty-nine percent of samples had an aerobic plate count greater than 10(3) CFU/ml. Ice that had been used to cool shellfish was of a lower microbiological quality than samples used to cool ready-to-eat fish, salads, or dairy produce. Samples of ice produced in commercial production facilities were of higher microbiological quality than samples of ice that were not. The microbiological quality of ice was dependent on the type of use, the type of premises, and the type and place of production. Although most ice samples were of acceptable microbiological quality, evidence from this study suggests that the microbiological quality of ice prepared and used at certain premises in the UK is a cause for concern.

Recent advances in amebiasis

Advancements in our understanding of amebiasis have been rapid over the decade that I have followed this field. What was identified morphologically for years as Entamoeba histolytica has been redescribed with modern techniques as a complex of two species, the commensal parasite E. dispar and the pathogenic parasite E. histolytica that is the cause of colitis and liver abscess. Antigen detection tests are now available for the rapid detection in stool of the pathogenic species E. histolytica. New understandings of the importance of luminal as well as tissue-active antimebic medications in the treatment of invasive disease have been reached. The groundwork is being laid for an understanding of the protective immune responses to infection, and at the lab bench DNA transfection of the parasite has opened studies of pathogenesis to genetic analysis. While necessarily an incomplete sketch of the field, I have attempted here to highlight some recent and important developments of interest to clinicians and microbiologists.