Dequalinium chloride vaginal tablets for recalcitrant Trichomonas vaginalis: A case report.

Treatment options for recalcitrant Trichomonas vaginalis (TV), when very high dose systemic 5-nitroimidazole plus intravaginal therapy for over 14 days has failed, are very limited. They have poor efficacy, unpleasant side effects, and are difficult and expensive to acquire. We report successful treatment with 24 weeks of daily dequalinium chloride vaginal tablets. Dequalinium is licensed in Europe where it is readily available and cheap. It offers a safe and pragmatic alternative for recalcitrant TV.

Feasibility and acceptability of sexually transmitted infection screening during antenatal care of women in Dhaka, Bangladesh.

BACKGROUND: Sexually transmitted infections (STIs) are a major public health concern worldwide. Untreated STIs may have serious sequelae, particularly in pregnant women. The objective of this study was to assess the feasibility and acceptability of screening and treating common STIs in women during pregnancy in Bangladesh. METHODS: Women were enrolled from four maternity clinics/hospitals serving the lower-middle class population in Dhaka, Bangladesh. The participants were interviewed, and vaginal swab samples were collected by clinical staff. Specimens were tested for Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis and high-risk Human Papilloma Viruses (HPVs) using GeneXpert (Cepheid, Sunnyvale, California). Women were informed of their test results and were provided treatment for curable infections. A test of cure was performed. RESULTS: Out of 1157 pregnant women approached, 1000 (86.4%) participated. Ninety-one percent women learned of their test results on the same day of testing. Out of the 996 valid results, 7 (0.7%) tested positive for Chlamydia trachomatis and 1 (0.1%) for Trichomonas vaginalis. There were no gonorrhoea cases. Out of the 971 women with valid results for high-risk HPVs, 46 (4.7%) tested positive. CONCLUSIONS: Screening women for STIs during antenatal care was highly feasible and well-accepted in Bangladesh. While the prevalence of common curable STIs was very low, hrHPV infection prevalence was moderately high. Our findings support period monitoring of STIs and continued prevention efforts for cervical cancer in Bangladesh.

Novel quinoline derivatives with broad-spectrum antiprotozoal activities.

Several quinoline derivatives incorporating arylnitro and aminochalcone moieties were synthesized and evaluated in vitro against a broad panel of trypanosomatid protozoan parasites responsible for sleeping sickness (Trypanosoma brucei rhodesiense), nagana (Trypanosoma brucei brucei), Chagas disease (Trypanosoma cruzi), and leishmaniasis (Leishmania infantum). Several of the compounds demonstrated significant antiprotozoal activity. Specifically, compounds 2c, 2d, and 4i displayed submicromolar activity against T. b. rhodesiense with half-maximal effective concentration (EC50) values of 0.68, 0.8, and 0.19 µM, respectively, and with a high selectivity relative to human lung fibroblasts and mouse primary macrophages (∼100-fold). Compounds 2d and 4i also showed considerable activity against T. b. brucei with EC50 values of 1.4 and 0.4 µM, respectively.

Therapeutic potential of antimicrobial peptides against pathogenic protozoa.

Protozoal infections cause significant morbidity and mortality in humans and animals. The use of several antiprotozoal drugs is associated with serious adverse effects and resistance development, and drugs that are more effective are urgently needed. Microorganisms, mammalian cells and fluids, insects, and reptiles are sources of antimicrobial peptides (AMPs) that act against pathogenic microorganisms; these AMPs have been widely studied as a promising alternative therapeutic option to conventional antibiotics, aiming to treat infections caused by multidrug-resistant pathogens. One advantage of AMP molecules is their adaptability, as they can be easily fine-tuned for broad-spectrum or targeted activity by changing the amino acid residues in their sequence. Consequently, these variations in structural and physicochemical properties can alter the antimicrobial activities of AMPs and decrease resistance development. This article presents an overview of peptide activities against amebiasis, giardiasis, trichomoniasis, Chagas disease, leishmaniasis, malaria, and toxoplasmosis. AMPs and their analogs demonstrate great potential as therapeutics, with potent and selective activity, when compared with commercially available drugs, and hold the potential to act as new scaffolds for the development of novel anti-protozoal drugs.

Primary amebic meningoencephalitis: a review of Naegleria fowleri and analysis of successfully treated cases.

Primary amebic meningoencephalitis (PAM) is a necrotizing and hemorrhagic inflammation of the brain and meninges caused by Naegleria fowleri, a free-living thermophilic ameba of freshwater systems. PAM remains a neglected disease that disproportionately affects children in tropical and subtropical climates, with an estimated mortality rate of 95-98%. Due to anthropogenic climate change, the average temperature in the USA has increased by 0.72 to 1.06 °C in the last century, promoting the poleward spread of N. fowleri. PAM is often misdiagnosed as bacterial meningitis or viral encephalitis, which shortens the window for potentially life-saving treatment. Diagnosis relies on the patient's history of freshwater exposure and the physician's high index of suspicion, supported by cerebrospinal fluid studies. While no experimental trials have been conducted to assess the relative efficacy of treatment regimens, anti-amebic therapy with adjunctive neuroprotection is standard treatment in the USA. We performed a literature review and identified five patients from North America between 1962 and 2022 who survived PAM with various degrees of sequelae.

The prevalence of sexually transmitted infections and their association with knowledge, attitudes, and practice in male street children in Indonesia.

BACKGROUND: Street children's level of knowledge, attitudes, and practice (KAP) regarding sexually transmitted infections (STIs) and HIV-related diseases remains a challenge since it is difficult to reach all key populations. This study aims to provide an overview of the findings of STI cases and their association with the KAP of street children in Jakarta and Banten. METHODS: We conducted a cross-sectional study on 259 male street children (aged 10 -21 years old). We collected the data through questionnaire interviews, history taking, physical examination, and specimen collection for STI and HIV testing. RESULTS: 5.8% (n = 15) STI cases were discovered, consisting of Hepatitis B (n = 6), Hepatitis C (n = 1), HIV (n = 2), Chlamydia (n = 3), Syphilis (n = 1), and Gonorrhea (n = 1). Buskers (44.4%) and other occupations like helping parents sell their wares, parking lot attendants, shoe shiners, or gathering (44.8%) dominated the sociodemographic characteristics. Condomless sex predominated risky sexual behavior, despite some subjects already having good knowledge. CONCLUSION: Sociodemographic characteristics and the KAP of street children in Indonesia are varied. The association between the KAP level and STI cases in street children is challenging to describe. Further studies covering more areas in Indonesia are required.

Multiple protozoal infections in a single immunocompromised patient: A case report.

Immunocompromised patients with human immunodeficiency virus (HIV) infection are prone to multiple infections, of which parasitic infections are an important cause. Parasitic protozoal infections - both by common and rare protozoa are documented in such patients. Here, we report a rare and interesting case of five protozoal infections affecting a single HIV-infected person at the same time of initial presentation. A 64-years-male came to us with complaints of chronic diarrhea for 6 months. He was investigated and found to be positive for HIV I. His stool examination revealed cysts of Entameba histolytica and Giardia lamblia and oocysts of Cryptosporidium species and Cystoisospora species. His toxoplasma IgG was also positive in high titer. The patient was medically diagnosed and was treated with medications as clinically prescribed - antiretroviral therapy was initiated and he was discharged in due course. A total of five protozoal infections were documented affecting a single person - newly diagnosed immunocompromised male, which by sheer qualitative count of patient case histories, indeed is a rare case reported in the medical literature.

Human protozoa infection and dysplasia in ulcerative colitis: a neglected aspect in a prominent disease.

The chance of getting colorectal cancer (CRC) is higher in people with chronic ulcerative colitis (UC). The impact of parasitic infections on UC is underappreciated. The purpose of this study was to look into the effect of intestinal protozoal infections on the dysplastic changes generated by UC. The research included 152 adult patients with histologically confirmed UC and 152 healthy controls. Fecal samples were examined for the presence of parasites and fecal calprotectin (FC). The enzyme-linked immunosorbent assay measured serum anti-p53 antibodies (p53Abs) and metallothioneins (MTs). The advanced oxidation protein products (AOPPs) and reduced glutathione (GSH) levels were measured by a spectrophotometric method in all subjects. Serum C-reactive protein (CRP) and IL-6 were also measured. In addition, histopathological and immunohistochemical investigations of intestinal tissue were done. Our results exhibited significant increases in FC and CRP, IL-6, AOPPs, MTs, and p53Abs in ulcerative colitis patients with parasitic infections compared to those without parasites. In contrast, GSH levels showed a significant decrease in the same group compared with other groups. Histopathological and immunohistochemical assessments of intestinal tissue signified severe inflammation and strong expression of PD-L1 in patients with parasitic infections compared to others without parasitic infections. Our research indicated a greater frequency of intestinal protozoa in UC patients with elevated inflammatory and dysplastic biomarker levels. This suggests that these parasites may be involved in the etiology of chronic UC and the associated carcinogenetic process. This is the first report of a link between parasitic infections and dysplastic alterations in UC patients.

Evaluation of real-time polymerase chain reaction for the diagnosis of protozoal myeloencephalitis in horses using cerebrospinal fluid.

BACKGROUND: Equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona remains an antemortem diagnostic challenge in some horses. Recent work suggested the use of real-time PCR (rtPCR) on cerebrospinal fluid (CSF) as a promising diagnostic tool. OBJECTIVE: To evaluate the sensitivity and specificity of S. neurona rtPCR on CSF for EPM diagnosis using horses with EPM and S. neurona-seropositive horses with other neurologic conditions. ANIMALS: Ninety-nine horses with neurologic disease that underwent complete neurologic examination, CSF collection, and, if euthanized, necropsy including the central nervous system (CNS). METHODS: Retrospective case-control study using banked CSF samples. Samples from horses with neurologic abnormalities and necropsy-confirmed EPM diagnosis, presumptive EPM diagnosis using strict criteria (SnSAG2/4/3 ELISA serum:CSF titer ratios <50) and horses diagnosed with other neurologic diseases were used. RESULTS: Fifty-two horses had EPM; 23 were confirmed on necropsy, and 29 were presumptive clinical diagnoses. The other 47 horses all had necropsy-confirmed diagnoses. Four of the 47 horses had normal neurologic findings on necropsy and the remaining 43 horses had neurologic diseases including equine degenerative myeloencephalopathy (EDM), cervical vertebral stenotic myelopathy, trauma, and other miscellaneous conditions. One CSF sample was weakly positive for S. neurona by rtPCR, this sample was obtained from a horse with confirmed EDM. Samples from the other 98 horses were negative for S. neurona by rtPCR. CONCLUSIONS AND CLINICAL IMPORTANCE: Our study contradicts previous conclusions that S. neurona rtPCR is potentially useful for EPM diagnosis, because our results indicate that the assay has a low sensitivity (0%) for EPM.

Intestinal Parasitic Infections in 2023.

Intestinal parasites include intestinal protozoa and intestinal helminths. Intestinal parasitic infections (IPIs) pose a global health problem affecting over one billion people worldwide. Although these infections are predominantly seen in the developing world, they are frequently seen in the developed countries, particularly in immunocompromised patients. Patients' clinical presentations generally include diarrhea, dysentery, abdominal pain, nausea, vomiting, nutritional deficiency, iron deficiency anemia, anal and perianal itching, and rarely intestinal obstruction. The intestinal parasites have similarities in their mode of transmission and life cycle. The stool test is the primary way of diagnosing IPIs. Treatment is given with various anti-parasitic agents. However, appropriate preventive measures are essential for successfully controlling the IPIs.

Trichomonas vaginalis infection is associated with increased risk of cervical carcinogenesis: A systematic review and meta-analysis of 470 000 patients.

BACKGROUND: Trichomonas vaginalis infection is the most prevalent non-viral sexually transmitted infection (STI) in women and has been suggested as a risk factor for developing cervical cancer. OBJECTIVE: We aimed to investigate the associations between T. vaginalis infection and cervical carcinogenesis. SEARCH STRATEGY: A comprehensive systematic search was conducted in five databases on 21 October 2021. SELECTION CRITERIA: Studies assessing the relationship between T. vaginalis infection, HPV co-infections, cervical dysplasia, and cervical cancer were found eligible. DATA COLLECTION AND ANALYSIS: Summary estimates for pooled odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated with a random-effects model. Statistical heterogeneity was measured with I2 and Cochran's Q tests. MAIN RESULTS: The 29 articles included 473 740 women, of whom 8518 were T. vaginalis-positive. Our results showed that T. vaginalis-infected women had 1.79 times higher odds of being diagnosed with HPV co-infection (95% CI 1.27-2.53; I2 95%). We also found that T. vaginalis infection was associated with high-grade squamous intraepithelial lesion diagnosis (OR 2.34, 95% CI 1.10-4.95; I2 75%) and cervical cancer (OR 5.23, 95% CI 3.03-9.04; I2 3%). CONCLUSIONS: Our results showed an association between T. vaginalis and cervical carcinogenesis in sexually active women.

Production, characterization, and dietary supplementation effect of rumen-protected fat on ruminal function and blood parameters of sheep.

Rumen-protected fat (RPF) was produced in the 1st experimental stage through melt-emulsification technique using buriti oil (BO) as core, at concentrations of 10% (BO10), 20% (BO20), and 30% (BO30) (w/w), and carnauba wax (CW) as encapsulant material. After obtention and characterization, protected fat microspheres were tested in a 2nd experimental stage on the sheep' diet using six castrated 2-year-old male Santa Ines with initial weight 48.9 ± 5.23 kg, fistulated in rumen and distributed in a double Latin square design with 3 treatments × 3 periods, to evaluate rumen pH, temperature, protozoal count, and blood parameters. There was no difference (P > 0.05) among RPF microspheres for microencapsulation yield. However, microencapsulation efficiency increased (P < 0.05) with BO addition ranging from 36 to 61.3% for BO10 and BO30, respectively. The inclusion of BO10 in the sheep's diet did not affect the ruminal dry matter degradability (DMD) of BO over time (P > 0.05); however, BO20 and BO30 had higher (P < 0.05) DMD values than BO10. No significant differences were observed among RPF for rumen pH and temperature (P > 0.05). There was an increase (P < 0.05) in the protozoal population in the rumen environment due to the microencapsulated BO30 inclusion. There was also increase (P < 0.05) in serum albumin, cholesterol, aspartate aminotransferase (ALT), and gamma-glutamyltransferase (GGT), and a reduction (P < 0.05) in serum triglycerides of the sheep when RPF microspheres increased in the diet. Melt-emulsification proved to be a good technique for microencapsulation of buriti oil into the carnauba wax matrix. RPF from buriti oil protected into carnauba wax is recommended for sheep diet because it increases energy density, without adverse effects on the protozoal populations and blood serum metabolites from the bypass effect in the rumen.

Trypanosoma cruzi Central Nervous System Infection-Pathogenesis, Clinical Manifestations, Diagnosis, and Treatment.

Purpose of Review: Chagas disease (CD) is a neglected tropical disease from the American continent that commonly causes cardiovascular disease. Some patients develop neurological manifestations. We discuss and summarize the pathogenesis, clinical characteristics, diagnosis, and treatment of the central nervous system manifestations of CD. Recent Findings: Cerebrospinal fluid quantitative polymerase chain reaction tests and next-generation sequencing in tissue samples have facilitated disease diagnosis and follow-up. Novel presentations, including retinitis, are now reported. A new MRI sign called "Bunch of açai berries appearance"-multiple hypointense nodular lesions-has been described recently. Treatment with benznidazole at higher doses and the role of therapeutic drug monitoring need to be further studied in this setting. Summary: A high suspicion index is paramount to diagnosing Chagas' central nervous system involvement. Standardized molecular diagnostics can aid in the initial workup. Future development of new therapeutic drugs is crucial because of the toxicity profile of the currently available medications.

Rhizobium pusense-Mediated Selenium Nanoparticles-Antibiotics Combinations against Acanthamoeba sp.

Severe ocular infections by Acanthamoeba sp. lead to keratitis, resulting in irreversible vision loss in immune-compromised individuals. When a protozoal infection spreads to neural tissues, it causes granulomatous encephalitis, which can be fatal. Treatment often takes longer due to the transition of amoeba from trophozoites to cyst stages, cyst being the dormant form of Acanthamoeba. A prolonged use of therapeutic agents, such as ciprofloxacin (Cipro), results in severe side effects; thus, it is critical to improve the therapeutic efficacy of these widely used antibiotics, possibly by limiting the drug-sensitive protozoal-phase transition to cyst formation. Owing to the biomedical potential of selenium nanoparticles (SeNPs), we evaluated the synergistic effects of ciprofloxacin and Rhizobium pusense-biogenic SeNPs combination. SeNPs synthesized using Rhizobium pusense isolated from root nodules were characterized using UV-Visible spectrophotometer, FT-IR, SEM with EDX, particle size analysis, and Zeta potential. The combination was observed to reduce the sub-lethal dose of Cipro, which may help reduce its side effects. The selenium and ciprofloxacin (SeNPs-Cipro) combination reduced the LC50 by 33.43%. The anti-protozoal efficacy of SeNPs-Cipro was found to transduce through decreased protozoal-cyst formations and the inhibition of the galactosidase and protease enzymes of trophozoites. Furthermore, high leakage of sugar, proteins, and amino acids during the SeNPs-Cipro treatment was one primary reason for killing the trophozoites. These experimental results may be helpful in the further pre-clinical evaluation of SeNPs-Cipro to combat protozoal infections. Future studies for combinations of SeNPs with other antibiotics need to be conducted to know the potential of SeNPs against antibiotic resistance in Acanthamoeba.

Inhibition studies of the protozoan α-carbonic anhydrase from Trypanosoma cruzi with phenols.

The α-class carbonic anhydrase (CA, EC 4.2.1.1) from the protozoan pathogen Trypanosoma cruzi, TcCA, was investigated earlier for its inhibition with anions, sulphonamides, thiols and hydroxamates, well-known classes of CA inhibitors (CAIs). Here we present the first inhibition study of this enzyme with phenols, which possess a diverse CA inhibition mechanism compared to the previously investigated compounds, which are all zinc binders. Indeed, phenols are known to anchor to the zinc coordinated water molecule within the enzyme active site. In a series of 22 diversely substituted phenols, the best inhibitors were simple phenol, pyrocatechol, salicylic acid, 3,5-difluorophenol, 3,4-dihydroxy-benzoic acid, 3,6- dihydroxy-benzoic acid, caffeic acid and its des-hydroxy analog, with KIs of 1.8 - 7.3 µM. The least effective TcCA inhibitor was 3-chloro-4-amino-phenol (KI of 47.9 µM). Although it is not yet clear whether TcCA can be considered as an anti-Chagas disease drug target, as no animal model for investigating the antiprotozoan effects is available so far, finding effective in vitro inhibitors may be a first relevant step towards new antiprotozoal agents.

Anti-protozoal activity and metabolomic analyses of Cichorium intybus L. against Trypanosoma cruzi.

Chagas disease, caused by the protozoa Trypanosoma cruzi, is a potentially life-threatening parasitic zoonosis infecting 6-7 million people worldwide, mainly in Latin America. Due to the limited numbers of drugs available against this neglected disease and their frequent adverse effects, novel anti-chagasic agents are urgently needed. Cichorium intybus L. (chicory) is a bioactive plant with potent activity against parasitic nematodes, but its effects on protozoans are poorly known and no studies have explored its trypanocidal potential. Here, we investigated the activity of C. intybus against extracellular and intracellular stages of T. cruzi, including the prediction of trypanocidal compounds by metabolomic analyses and bioactivity-based molecular networking. Purified C. intybus extracts were prepared from leaves and roots of five C. intybus cultivars (cv. 'Benulite', 'Goldine', 'Larigot', 'Maestoso' and 'Spadona'). All C. intybus extracts induced concentration-dependent effects against T. cruzi trypomastigotes. C. intybus leaf extracts had higher trypanocidal selectivity and lower cytotoxicity on mammalian cells than root extracts. The leaf extract of C. intybus cv. Goldine also significantly reduced the number of mammalian cells infected with T. cruzi amastigotes. Metabolomic and bioactivity-based molecular networking analyses revealed 11 compounds in C. intybus leaves strongly linked with activity against trypomastigotes, including the sesquiterpene lactone lactucin, and flavonoid- and fatty acid-derivatives. Furthermore, seven distinct C. intybus molecules (including two sesquiterpene lactone-derivatives) were predicted to be involved in reducing the number of mammalian cells infected with amastigotes. This is the first report of the anti-protozoal activity of C. intybus against trypanosomatid parasites and expands our understanding of the anti-parasitic effects of this plant and its bioactive metabolites. Further studies to elucidate the anti-protozoal compound(s) in C. intybus and their mode(s) of action will improve our knowledge of using this bioactive plant as a promising source of novel broad-spectrum anti-parasitic compounds with associated health benefits and biomedical potential.

The Effect of Phytonutrients in Terminalia chebula Retz. on Rumen Fermentation Efficiency, Nitrogen Utilization, and Protozoal Population in Goats.

The aim of this study was to investigate the effect of Terminalia chebula meal (TCM) supplementation on digestibility, rumen fermentation, nitrogen utilization, and protozoal population in goats. Eight goats with an initial body weight (BW) of 13 ± 3.0 kg were randomly assigned according to a double 4 × 4 Latin square design to receive different levels of TCM supplementation at 0, 8, 16, and 24 g/kg of total dry matter (DM) intake, respectively. The goats were fed with concentrate diets at 13 g/kg BW, while rice straw was used as a roughage source, fed ad libitum. The results revealed that the feed intake and the apparent digestibility of DM, organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were similar among the treatments (p > 0.05). However, crude protein (CP) digestibility decreased significantly (p < 0.05) when supplemented with TCM at 24 g/kg of total DM intake (p < 0.05). The addition of TCM did not change the ruminal pH and blood urea nitrogen concentrations (p > 0.05), whereas the concentration of NH3-N at 4 h post feeding was reduced with the inclusion of TCM at 16 and 24 g/kg of total DM intake. The total numbers of bacteria were enhanced by the addition of TCM, while the protozoal population, in both entodiniomorph and holotrich, was reduced (p < 0.05). The supplementation of TCM did not change the concentration of total volatile fatty acids (TVFA), acetic acid, or butyric acid, while the propionic acid concentration at 4-h post feeding increased significantly, especially when supplemented at 16 g/kg of total DM intake (p < 0.05. In addition, urinary nitrogen (N) excretion decreased, while fecal N excretion, N absorption, N retention, and the proportion of N retention to N intake increased with the inclusion of TCM at all levels. In summary, the inclusion of TCM could improve rumen fermentation efficiency and N balance without having an adverse effect on feed intake, nutrient digestibility, and rumen ecology; however, the protozoal population decreased. Therefore, this study suggests that TCM (16 g/kg of total DM intake) could be used as a plant source for rumen enhancement in goats fed a diet based on rice straw without having an adverse effect on feed intake or nutrient digestion. However, further studies on the production of types of meat and milk that have a long-term feeding trial should be carried out.

Successful Treatment of Primary Amoebic Meningoencephalitis Using a Novel Therapeutic Regimen Including Miltefosine and Voriconazole.

The genus Naegleria consists of free-living amoebae widely distributed worldwide in soil and freshwater habitats. Primary amoebic meningoencephalitis (PAM) is an uncommon and most likely fatal disease. The incubation period is approximately 7 days. The first symptoms are headache, nasal congestion, fever, vomiting, stiff neck within 3-4 days after the first symptoms, confusion, abnormal behavior, seizures, loss of balance and body control, coma, and death. We describe the case of a child who presented with PAM due to Naegleria sp., fully recovered from the infection without apparent sequels after treatment with a regimen that included miltefosine and voriconazole.

British Association for Sexual Health and HIV (BASHH) United Kingdom national guideline on the management of Trichomonas vaginalis 2021.

The main objective of this guideline is to assist practitioners in managing individuals diagnosed with Trichomonas vaginalis (TV). It offers recommendations on the diagnostic tests, treatment regimens and health promotion principles needed for the effective management of TV. It covers the management of the initial presentation, as well as how to prevent transmission and future re-infection. It is aimed primarily at people aged 16 years or older presenting to health care professionals, working in departments offering specialist care in sexually transmitted infection (STI) management within the United Kingdom. However, the principles of the recommendations are applicable across all levels of STI care providers (N.B. non-specialist services may need to develop, where appropriate, local care pathways).

How to get away with murder: The multiple strategies employed by pathogenic protozoa to avoid complement killing.

Parasitic protozoa are eukaryotic unicellular organisms that depend on a variety of living organisms and can develop intra- and extracellularly inside their hosts. In humans, these parasites cause diseases with a significant impact on public health, such as malaria, toxoplasmosis, Chagas disease, leishmaniasis and amebiasis. The ability of a parasite in establishing a successful infection depends on a series of intricate evolutionarily selected adaptations, which include the development of molecular and cellular strategies to evade the host immune system effector mechanisms. The complement system is one of the main effector mechanisms and the first humoral shield of hosts innate immunity against pathogens. For unicellular pathogens, such as protozoa, bacteria and fungi, the activation of the complement system may culminate in the elimination of the invader mainly via 1- the formation of a pore that depolarizes the plasma membrane of the parasite, causing cell lysis; 2- opsonization and killing by phagocytes; 3- increasing vascular permeability while also recruiting neutrophils to the site of activation. Numerous strategies to avoid complement activation have been reported for parasitic protozoa, such as 1- sequestration of complement system regulatory proteins produced by the host, 2- expression of complement system regulatory proteins, 3- proteolytic cleavage of different complement effector molecules, 4- formation of a physical glycolipid barrier that prevents deposition of complement molecules on the plasma membrane, and 5- removal, by endocytosis, of complement molecules bound to plasma membrane. In this review, we revisit the different strategies of blocking various stages of complement activation described for the main species of parasitic protozoa, present the most recent discoveries in the field and discuss new perspectives on yet neglected strategies and possible new evasion mechanisms.