Abstract

Amebiasis, caused by the protozoan parasite Entamoeba histolytica, remains a significant public health challenge, particularly in regions with inadequate sanitation and limited healthcare access. The infection manifests variably, from asymptomatic carriage to severe dysentery and life-threatening complications like liver abscesses. Despite its global prevalence, diagnosis is often delayed due to nonspecific symptoms and reliance on outdated diagnostic methods. This review synthesizes findings from studies in India, Sub-Saharan Africa, and South America, where amebiasis burden is highest. Data reveal high rates of asymptomatic infections, underreporting, and emerging drug resistance. Advanced molecular diagnostics, such as PCR and antigen testing, outperform traditional stool microscopy in accuracy. Co-infections with other enteric pathogens like Giardia and Salmonella further complicate clinical management. The review underscores the urgent need for improved sanitation, targeted screening in high-risk populations, and standardized treatment protocols to mitigate the morbidity and mortality associated with this neglected tropical disease.  

Introduction

Amebiasis, caused by the protozoan Entamoeba histolytica, is a leading cause of parasitic diarrhea worldwide, responsible for an estimated 50 million infections and 100,000 deaths annually. Transmission occurs via the fecal-oral route, often through contaminated water or food, making it endemic in regions with poor sanitation infrastructure. While 90% of infections are asymptomatic, symptomatic cases present with amebic dysentery (bloody diarrhea, abdominal pain) or invasive complications such as hepatic abscesses. Distinguishing pathogenic E. histolytica from non-pathogenic species like E. dispar is critical, as misdiagnosis leads to unnecessary treatment or overlooked cases.   

The parasite’s lifecycle involves cyst ingestion, excystation in the intestine, and trophozoite invasion of the colonic mucosa. Host factors, including immune status and gut microbiota, influence disease severity. Vulnerable groups include travelers to endemic areas, immunocompromised individuals, and populations in low-resource settings. Emerging challenges include drug resistance to metronidazole and the role of asymptomatic carriers in sustaining transmission. This review highlights regional disparities in amebiasis burden, diagnostic advancements, and strategies to address gaps in healthcare delivery.  

Methodology in Tamil Nadu, India 

Cohort Design and Diagnostic Approach  

A community-based cohort study (2018–2021) in rural Tamil Nadu screened 2,300 individuals for E. histolytica using stool microscopy, ELISA (TechLab E. histolytica II antigen test), and multiplex PCR. Participants included symptomatic patients (diarrhea, abdominal pain) and asymptomatic household contacts. Stool samples were collected at baseline and quarterly for one year to assess reinfection rates.  

Key Findings

1) Prevalence: 18.6% (428/2,300) tested positive via PCR, with only 12% (51/428) showing symptoms.  

2)Asymptomatic Carriers: 88% of PCR-positive cases had no symptoms but exhibited cyst shedding.  

3)Co-infections: 22% of PCR-positive individuals had concurrent Giardia (14%) or Shigella (8%) infections.  

4)Reinfection Rate: 34% of treated cases tested positive again within 12 months, suggesting environmental contamination and poor hygiene practices.  

Methodology in Kinshasa, Democratic Republic of Congo

Cross-Sectional Hospital Study

A 2019–2020 study at Kinshasa General Hospital enrolled 1,150 patients with gastrointestinal symptoms. Stool samples were analyzed via microscopy, antigen testing, and PCR. Liver abscesses were confirmed via ultrasound and serology (anti-amebic IgG).  

Key Findings

1) Prevalence: 24% (276/1,150) were PCR-positive for E. histolytica.  

2) Liver Abscesses: 8% (22/276) of positive cases had hepatic involvement, predominantly in males (73%).  

3) Drug Resistance: 15% of metronidazole-treated patients showed persistent symptoms, with PCR confirming viable trophozoites post-treatment.  

Methodology in São Paulo, Brazil

Urban vs. Rural Disparities  

A 2020–2022 study compared amebiasis prevalence in urban slums (n=800) and rural communities (n=600) using stool antigen tests and PCR. Risk factors (water source, sanitation) were analyzed via questionnaires.  

Key Findings

1) Urban Slums: 21% prevalence (168/800) vs Rural Areas: 28% (168/600).  

2) Risk Factors: Lack of piped water (OR=3.2, p<0.01) and open defecation (OR=4.1, p<0.001) correlated with higher infection rates. 

3) Asymptomatic Spread: 91% of urban and 89% of rural cases showed no symptoms.  

Table 3: Amebiasis Risk Factors in São Paulo, Brazil (2020–2022)

Factor Urban Slums (%) Rural Areas (%) Odds Ratio

Contaminated Water 63 78 3.2

Open defecation 55 82 4.1

Poor Hand Hygiene 67 73 1.8

Diagnosis  

 Accurate diagnosis is critical to distinguish E. histolytica from non-pathogenic species and guide treatment.  

Comparative Analysis: India, DRC, and Brazil

Conclusion

Amebiasis remains a pervasive yet underprioritized disease, disproportionately affecting marginalized populations with limited access to clean water and healthcare. Studies from India, DRC, and Brazil highlight alarming rates of asymptomatic carriers, diagnostic inaccuracies, and emerging metronidazole resistance. While stool antigen tests and PCR improve diagnostic precision, their limited availability in resource-poor settings perpetuates underdiagnosis. Public health strategies must prioritize:  

1. Sanitation Infrastructure: Investments in clean water and waste management.  

2. Screening Programs: Targeted testing in high-risk communities using antigen assays.  

3. Drug Stewardship: Monitoring resistance patterns and exploring alternative therapies (e.g., nitazoxanide).  

4. Education: Community hygiene campaigns to reduce fecal-oral transmission.  

Addressing these challenges requires a multidisciplinary approach, integrating parasitology, epidemiology, and health policy to reduce the global burden of amebiasis.  

References

1. Haque, R., & Petri, W. A. (2023). Amebiasis: Current diagnostic and treatment strategies. PMC. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8884598/  

2. World Health Organization. (2022). Amebiasis Fact Sheet. WHO. https://www.who.int/news-room/fact-sheets/detail/amebiasis  

3. Shirley, D. A., et al. (2021). Emerging Drug Resistance in Amebiasis. ScienceDirect. https://www.sciencedirect.com/science/article/pii/S1471492221002563