The epidemiology of soil-transmitted helminth and protozoan infections in south-west Cameroon

Immunological clues to sex differences in parasitic diseases

The effect of sex on the prevalence and severity of parasitic diseases is an emerging area of research. Several factors underlie sex-based differences, including sociocultural influences that affect exposure to parasites, and physiological disparities linked to biological sex. Hence, human studies must be interpreted cautiously; however, studies conducted under controlled laboratory conditions are important to validate findings in humans. Such research can more effectively elucidate the role of sex-determining physiological factors (particularly their impact on immune responses), as well as the role of sex-specific differences in resistance to, or severity of, parasitic diseases. This review focuses on the overarching impact of biological sex variables on immunity. Both human and rodent experimental data are discussed, with a focus on selected protozoan and helminth infections.

Telomere Length in a South African Population Co-Infected with HIV and Helminths

Biological ageing refers to the gradual decrease in physiological functions, resulting in immune senescence, cellular damage and apoptosis. Telomere length is a biomarker of biological ageing. Limited studies have associated shorter telomere length with HIV and parasite single infections, with no studies reporting the association of HIV and parasite co-infection with telomere length. The study aimed to investigate whether telomere length shortening is accelerated in a South African population co-infected with HIV and helminths compared to participants singly infected with either HIV or helminths. Additionally, telomere length data were compared with participants' biochemical and full blood count parameters. A total of 200 participants were in groups of uninfected control, HIV single infection, helminth single infection and HIV and helminth co-infection groups. Relative telomere length (RTL) was determined using Real-Time PCR and associated with biochemical and full blood count parameters using multivariate regression analysis models that were adjusted for confounders. The uninfected control group was used as a reference group. The uninfected control group had the highest mean RTL (1.21 ± 0.53) while the HIV-infected (0.96 ± 0.42) and co-infected (0.93 ± 0.41) groups had similar RTLs, and lastly, the helminth-infected group (0.83 ± 0.33) had the lowest RTL (p = 0.0002). When compared to the uninfected control group, a significant association between RTL and biochemical parameters, including blood iron (β = -0.48), ferritin (β = -0.48), transferrin saturation (β = -0.57), transferrin (β = -0.57), phosphate (β = -0.47), vitamin A (β = -0.49) and C-reactive protein (β = -0.52) were noted in the co-infected group (p < 0.05). In addition, a significant association between RTL and full blood count, including (β = -0.47), haematocrit (β = -0.46), mean corpuscular volume (β = -0.47), lymphocytes (β = -0.45), mean corpuscular haemoglobin concentration (β = -0.45), red cell distribution width (β = -0.47), monocytes (β = -0.45), eosinophils (β = -0.45), basophils (β = -0.44) and transferrin saturation (β = -0.57) were also noted in the co-infected group (p < 0.05). Accelerated biological ageing, as indicated by telomere length shortening, is associated with HIV and helminth co-infections.

Intestinal helminthiasis, anaemia and associated risk factors in a cross-section of the population of Melong, Littorial Region of Cameroon

Assessment of risk factors of intestinal helminths and anaemia in various geographical regions is important for the development of appropriate control strategies. This study aimed at determining the risk factors associated with intestinal helminths and anaemia in Melong, Cameroon. A total of 325 participants were recruited in this study between September-December 2021. Faecal samples were examined using the formol-ether sedimentation technique while haemoglobin level was measured using a HemoCue spectrometer. Data on demographic and behavioural factors was collected and used to determine the risk factors using a pretested structured questionnaire and analysed using SPSS. The overall prevalence of intestinal helminths was 24.6% (80/325). Helminths recovered from the study included hookworm (16%; 52/325), Schistosoma mansoni (10.8% 35/325) Ascaris lumbricoides (1.9%; 6/325), and Trichuris trichiura (0.6%; 2/325) with 15 participants having multiple infections (4.6%). The geometric mean egg density was 77epg and ranged from 20 to 560 epg of faeces. Males and age group ≤ 5 years had the highest parasite intensity (248epg). The overall prevalence of anaemia was 33.5% (109/325). Anaemia was significantly (p = 0.001) high at 48.8% (39/80) in those infected with intestinal parasites compared to non-infected individuals. Age group of 31-45 years; [3.42(1.05-11.21)] and > 65 years [6.21(1.75-12.47)], poor knowledge [0.41(0.67-6.07)], no regular deworming [0.70(1.76-21.96)], mud floors toilet [6.18(1.61-23.79)], toilets made of sticks [16.5(4.24-64.31)], and participants who did not have stomach/abdominal pains [0.22(0.07-0.67)] were significant predictors of helminth infections. Age group < 15 years [2.58(1.09-6.11)], geophagia [3.69(1.91-9.33)], hookworm infection [3.26(1.49-7.11)], S. mansoni [1.72 (1.16-3.41)] and those with multiple infections [1.76(1.04-2.88)] were identified as risk factors for anaemia. Risk factors identified in this study can be used to improve the control mechanism put in place by the government.

Effects of Soil-Transmitted Helminths and Intestinal Protozoan Infections on Haemoglobin Levels among School-Aged Children in Belo and Bui, North West Cameroon: A Cross-Sectional Study

Introduction. Soil-transmitted helminths (STH) remain a public health problem worldwide especially in low-income countries. Soil-transmitted helminths are known to affect both growth and haemoglobin levels. In this study, we determine the prevalence of intestinal parasites and explored its association with anaemia in school-aged children (SAC). Methodology. A cross-sectional study was carried out amongst pupils selected from 18 primary schools in four communities of the North West Region. Stool samples were examined using direct wet mount and formol-ether concentration techniques, while finger prick was performed for the measurement of haemoglobin with a haemoglobinometer. Results. The results showed significant variation of STHs, intestinal protozoan prevalence, and anaemia between age, sex, and communities. The prevalence of Ascaris lumbricoides, Trichuris trichiura, and hookworms was 15.1%, 0.8%, and 2%, respectively, with an overall STH prevalence of 18.3% across the four communities. Soil-transmitted helminths were more prevalent in Mbessa (30.2%) in comparison to Nkor (26.7%), Djottin (17.5%), and Kumbo (9.6%) communities. The prevalence of Entamoeba histolytica/dispar was 25.4% and Giardia duodenalis (6.9%), with an overall intestinal protozoa prevalence of 31% across the four communities. The prevalence of anaemia in the study population was 23.1%. Conclusion. Soil-transmitted helminths, intestinal protozoan infections, and anaemia are prevalent in the study area. Anaemia was observed to be associated with STH, intestinal protozoa, and the communities under study. This study recommends continuous deworming and health education on personal sanitation and environmental sanitation.

The immunoglobulin G antibody response to malaria merozoite antigens in asymptomatic children co-infected with malaria and intestinal parasites

Background

Co-infection with malaria and intestinal parasites is common in children in Africa and may affect their immune response to a malaria parasite infection. Prior studies suggest that co-infections may lead to increased susceptibility to malaria infection and disease severity; however, other studies have shown the reverse. Knowledge on how co-morbidities specifically affect the immune response to malaria antigens is limited. Therefore, this study sought to determine the prevalence of co-infection of malaria and intestinal parasites and its association with antibody levels to malaria merozoite antigens.

Methods

A cross sectional study was carried out in two villages with high transmission of malaria in Cameroon (Ngali II and Mfou) where mass drug administration (MDA) had been administered at ~6-month intervals (generally with albendazole or mebendazole). Children aged 1–15 years were enrolled after obtaining parental consent. A malaria rapid diagnostic test was used on site. Four (4) ml of peripheral blood was collected from each participant to determine Plasmodium falciparum infections by microscopy, haemoglobin levels and serology. Fresh stool samples were collected and examined by wet mount, Kato-Katz method and modified Ritchie concentration techniques. A Multiplex Analyte Platform assay was used to measure antibody levels.

Results

A total of 320 children were enrolled. The prevalence of malaria by blood smear was 76.3% (244/320) and prevalence of malaria and intestinal parasites was 16.9% (54/320). Malaria prevalence was highest in young children; whereas, intestinal parasites (IP+) were not present until after 3 years of age. All children positive for malaria had antibodies to MSP1₄₂, MSP2, MSP3 and EBA175. No difference in antibody levels in children with malaria-co infections compared to malaria alone were found, except for antibody levels to EBA-175 were higher in children co-infected with intestinal protozoa (p = 0.018), especially those with Entamoeba histolytica infections (p = 0.0026).

Conclusion

Antibody levels to EBA175 were significantly higher in children co-infected with malaria and E. histolytica compared to children infected with malaria alone. It is important to further investigate why and how the presence of these protozoans might modulate the immune response to malaria antigens.

Soil-transmitted Helminth infection in the Tiko Health District, South West Region of Cameroon: a post-intervention survey on prevalence and intensity of infection among primary school children

Introduction

Soil-transmitted helminths (STH) infection remains a public health problem in sub-Saharan Africa with children being most vulnerable. STH infection may result in impairment, permanent disability or death. Annual mass deworming has been implemented in the Tiko Health District (THD), however, no study has assessed the current prevalence of STH infection. This study aimed to determine the prevalence, intensity of STH infections and associated risk factors among school children.

Methods

Two months after the school deworming exercise, 400 children were sampled from 10 schools in THD. Stool samples were collected and analyzed using the Kato-katz technique. Data on socio-demographic and behavioral factors were collected using questionnaires. Data were analyzed using SPSS and intensity of infection categorized following WHO recommendations. Descriptive data were calculated with frequencies (n) and proportions (%), prevalence and 95% confidence interval calculated for gender and age respectively. Differences in prevalence for socio-demographic characteristics and behavioral variables were calculated with Chi square (χ²). Independent sample t-test was used to compare the means in the number of eggs in feces between male and female school children.

Results

The prevalence of STH was 1% (95% CI: 0.02-1.98). Ascaris lumbricoides was the only STH species detected and all cases were of low intensities. The arithmetic mean egg intensity was 3.1egg per gram of faeces. Rates of infection were similar between gender and age. Site of defecation showed an association with STH infection (χ² = 13.63, p=0.03).

Conclusion

These findings suggested a low prevalence of STH infection which could be explained by the prior deworming of children, modification in environmental and behavioral factors. Questions on effectiveness of annual mass deworming in achieving STH elimination targets need to be investigated further.

A Review of Medication Use as an Indicator of Human Health Impact in Environmentally Stressed Areas

We reviewed from literature the feasibility of medication use as an indicator of health outcomes in environmentally stressed areas, especially where a paucity of typical epidemiological and other risk-based data are encountered. The majority of studies reported were about medication use as an indicator of adverse respiratory effects from air pollution in developed countries. Studies to a lesser extent pointed to medication use as indicator of health outcomes associated with other environmental health stressors such as water, noise pollution, and habitat conditions. The relationship between environmental stressors and medication use strongly suggests that medication use could be used to measure the impact of environmental stressors that otherwise could not be measured by epidemiological or other impact assessment studies, typically in settings where morbidity and mortality data might not be not accessible.

Analysis of the population-level impact of co-administering ivermectin with albendazole or mebendazole for the control and elimination of Trichuris trichiura

Introduction

Soil-transmitted helminth (STH) infections are predominately controlled by providing children with preventive chemotherapy with either albendazole or mebendazole. However, neither has a high efficacy against Trichuris trichiura. This low efficacy limits the overall effectiveness of the current STH control programmes against T. trichiura. It has been demonstrated that co-administering ivermectin with albendazole or mebendazole significantly increases the efficacy of current treatments, which may increase the overall effectiveness of control programmes.

Methods

Using a STH transmission mathematical model, we evaluated the potential impact of co-administering ivermectin with albendazole or mebendazole to treat T. trichiura within a preventive chemotherapy programme targeting children (2–15 year olds). We evaluated the impact in terms of reduction in prevalent infections, mean worm burden, and prevalence of heavy infections.

Results

Although the current treatment strategy reduced T. trichiura worm burden and prevalence of heavy infections, due to their poor efficacy the long term impact of preventive chemotherapy for children was smaller compared to the other STH. Co-administering ivermectin increased the projected impact of the preventive chemotherapy programme in terms of all three of the explored metrics, practically in high transmission settings. Furthermore, ivermectin co-administration greatly increased the feasibility of and timeframe for breaking transmission.

Conclusions

Co-administering ivermectin notably increased the projected impact of preventive chemotherapy in high transmission settings and increased the feasibility for breaking transmission. This has important implications for control programmes, some of which may be shifting focus from morbidity control to interruption of transmission, and some of which may be logistically unable to provide preventive chemotherapy twice a year as recommended. However, the benefit of co-administering ivermectin is limited by the fact that 2–5 year olds are often ineligible to receive treatment.

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The impact of chemotherapy against Trichuris is smaller compared to what can be seen for the other soil-transmitted helminths.

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Co-administering ivermectin increases the projected impact of preventive chemotherapy.

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It also has the potential to interrupt transmission in some settings.

Helminth prevalence among adults in rural Kenya: a stool survey for soil-transmitted helminths and schistosomiasis in Nyanza province

BACKGROUND

Soil-transmitted helminth (STH) prevalence in children is high in rural southwestern Kenya, but adult prevalence data are scarce. A 2010 study of a village in Nyanza province found a pediatric STH prevalence of 44% using a direct stool-smear method. Adult STH prevalence and associated predictors was measured in the same village.

METHODS

Adults (≥18 years) presenting at the out-patient department of the small hospital or community outreach events completed a short questionnaire and provided stool samples. Light microscopy for ova and larvae was conducted using a stool concentration technique to improve sensitivity. Multivariable regression models were used to identify predictors of STH prevalence.

RESULTS

Among 344 adults, STH prevalence was 15.7% (54/344). Hookworm was most common (13.1%; 45/344), followed by Ascaris lumbricoides (6.1%; 21/344) and Trichuris trichiura (0.6%; 2/344). Twelve participants (3.5%; 12/344) had multiple STHs and three (0.9%; 3/344) had Schistosoma mansoni. Female sex, older age and lower education level were significant STH predictors.

CONCLUSIONS

Adult STH prevalence was lower than previous studies of children from the same village. Adults with the identified risk factors had a prevalence of ≥20%, which may warrant periodic, targeted deworming of adults with these risk factors given the low cost and low toxicity of anthelmintic drugs.

The aetiology of anaemia during pregnancy: a study to evaluate the contribution of iron deficiency and common infections in pregnant Ugandan women

Objective

To describe the aetiology of anaemia in pregnant Ugandan women and explore Fe deficiency and common infections as contributors to anaemia in this population.

Design

Cross-sectional study in which Hb, ferritin, transferrin receptor (sTfR), C-reactive protein, α-1 acid glycoprotein, hepcidin, malaria, hookworm infestation, syphilis and Helicobacter pylori infection were assessed.

Setting

Antenatal care clinic at Kawempe Health Centre, Kampala, Uganda.

Subjects

HIV-negative women (n 151) in their first or second pregnancy at 10–16 weeks’ gestation.

Results

The prevalence of anaemia was 29·1 %. Fe deficiency was 40·4 % and 14·6 % based on ferritin <30 μg/l and on adjusted ferritin <12 μg/l respectively, and 6·6 % based on sTfR >8·3 μg/ml. The prevalence of Fe-deficiency anaemia was 9·3 % based on ferritin <30 μg/l, 6·6 % based on adjusted ferritin <12 μg/l and 4·3 % based on sTfR >8·3 μg/ml. Hepcidin concentration was positively correlated with ferritin concentration (n 151, r=0·578, P<0·00001). H. pylori infection was highly prevalent (70 %) while malaria, hookworm infestation and syphilis were not common. Of all women, 60·3 % had α-1 acid glycoprotein >1 g/l and/or C-reactive protein >5 mg/l. Malaria parasitaemia (OR=6·85; 95 % CI 1·25, 37·41, P=0·026) and Fe deficiency defined using sTfR (OR=5·58; 95 % CI 1·26, 24·80, P=0·024) were independently and positively associated with anaemia. Population-attributable risk factors for anaemia for raised C-reactive protein, Fe deficiency defined by sTfR >8·3 μg/ml and presence of malaria parasites were 41·6 (95 % CI 11·1, 72·2) %, 13·5 (95 % CI 2·0, 25·0) % and 12·0 (95 % CI 1·4, 22·6) %, respectively.

Conclusions

Infections and inflammation are of greater significance than Fe deficiency in the aetiology of anaemia in pregnant Ugandan women during the first trimester.

Randomized, controlled, assessor-blind clinical trial to assess the efficacy of single- versus repeated-dose albendazole to treat ascaris lumbricoides, trichuris trichiura, and hookworm infection

In many regions where soil-transmitted helminth infections are endemic, single-dose albendazole is used in mass drug administration programs to control infections. There are little data on the efficacy of the standard single-dose administration compared to that of alternative regimens. We conducted a randomized, controlled, assessor-blinded clinical trial to determine the efficacies of standard and extended albendazole treatment against soil-transmitted helminth infection in Gabon. A total of 175 children were included. Adequate cure rates and egg reduction rates above 85% were found with a single dose of albendazole for Ascaris infection, 85% (95% confidence interval [CI], 73, 96) and 93.8% (CI, 87.6, 100), respectively, while two doses were necessary for hookworm infestation (92% [CI, 78, 100] and 92% [CI, 78, 100], respectively). However, while a 3-day regimen was not sufficient to cure Trichuris (cure rate, 83% [CI, 73, 93]), this regimen reduced the number of eggs up to 90.6% (CI, 83.1, 100). The rate ratios of two- and three-dose regimens compared to a single-dose treatment were 1.7 (CI, 1.1, 2.5) and 2.1 (CI, 1.5, 2.9) for Trichuris and 1.7 (CI, 1.0, 2.9) and 1.7 (CI, 1.0, 2.9) for hookworm. Albendazole was safe and well tolerated in all regimens. A single-dose albendazole treatment considerably reduces Ascaris infection but has only a moderate effect on hookworm and Trichuris infections. The single-dose option may still be the preferred regimen because it balances efficacy, safety, and compliance during mass drug administration, keeping in mind that asymptomatic low-level helminth carriage may also have beneficial effects. (This study has been registered at ClinicalTrials.gov under registration number NCT01192802.).

Intestinal parasites in HIV-seropositive patients in the Continental Region of Equatorial Guinea: its relation with socio-demographic, health and immune systems factors

BACKGROUND

Prevalence of intestinal parasitic infections in HIV-positive people and its association with clinical and socioeconomic factors has been investigated on the mainland of Equatorial Guinea, in order to define the precise measures for improvement of their quality of life.

METHODS

In August 2010, 273 HIV-positive and 60 HIV-negative were recruited. A sample of faeces, T-CD4+ cell counts, and clinical, socioeconomic and demographic data were collected from each patient. Stool samples were analysed by microscopy and immunochromatography. Data were analysed by Pearson's χ2 test and the risk of each factor was measured by odds ratio bivariate analysis.

RESULTS

Two hundred and ten (76.9%) HIV-positive participants were infected by intestinal parasites and 16 parasite species were identified; 246 (48.9%) were pathogenic helminths, 159 (22.9%) pathogenic protozoa and 142 (28.2%) opportunistic protozoa. Trichuris trichiura, Entamoeba histolytica/dispar/moshkovskii, Ascaris lumbricoides and Giardia duodenalis were the most prevalent parasites; 52 (86.7%) of HIV-negative participants were parasitized. HIV was related to co-infection by Entamoeba spp., E. nana and Blastocystis hominis.

CONCLUSIONS

The high rates of parasitic infections found highlights the urgent need of environmental sanitation, health education and water distribution actions, as well as early diagnosis and treatment of intestinal parasites.

Immunoregulation by Taenia crassiceps and its antigens

Taenia crassiceps is a cestode parasite of rodents (in its larval stage) and canids (in its adult stage) that can also parasitize immunocompromised humans. We have studied the immune response elicited by this helminth and its antigens in mice and human cells, and have discovered that they have a strong capacity to induce chronic Th2-type responses that are primarily characterized by high levels of Th2 cytokines, low proliferative responses in lymphocytes, an immature and LPS-tolerogenic profile in dendritic cells, the recruitment of myeloid-derived suppressor cells and, specially, alternatively activated macrophages. We also have utilized the immunoregulatory capabilities of this helminth to successfully modulate autoimmune responses and the outcome of other infectious diseases. In the present paper, we review the work of others and ourselves with regard to the immune response induced by T. crassiceps and its antigens, and we compare the advances in our understanding of this parasitic infection model with the knowledge that has been obtained from other selected models.

Characterization of Trichuris trichiura from humans and T. suis from pigs in China using internal transcribed spacers of nuclear ribosomal DNA

Trichuris trichiura and Trichuris suis parasitize (at the adult stage) the caeca of humans and pigs, respectively, causing trichuriasis. Despite these parasites being of human and animal health significance, causing considerable socio-economic losses globally, little is known of the molecular characteristics of T. trichiura and T. suis from China. In the present study, the entire first and second internal transcribed spacer (ITS-1 and ITS-2) regions of nuclear ribosomal DNA (rDNA) of T. trichiura and T. suis from China were amplified by polymerase chain reaction (PCR), the representative amplicons were cloned and sequenced, and sequence variation in the ITS rDNA was examined. The ITS rDNA sequences for the T. trichiura and T. suis samples were 1222–1267 bp and 1339–1353 bp in length, respectively. Sequence analysis revealed that the ITS-1, 5.8S and ITS-2 rDNAs of both whipworms were 600–627 bp and 655–661 bp, 154 bp, and 468–486 bp and 530–538 bp in size, respectively. Sequence variation in ITS rDNA within and among T. trichiura and T. suis was examined. Excluding nucleotide variations in the simple sequence repeats, the intra-species sequence variation in the ITS-1 was 0.2–1.7% within T. trichiura, and 0–1.5% within T. suis. For ITS-2 rDNA, the intra-species sequence variation was 0–1.3% within T. trichiura and 0.2–1.7% within T. suis. The inter-species sequence differences between the two whipworms were 60.7–65.3% for ITS-1 and 59.3–61.5% for ITS-2. These results demonstrated that the ITS rDNA sequences provide additional genetic markers for the characterization and differentiation of the two whipworms. These data should be useful for studying the epidemiology and population genetics of T. trichiura and T. suis, as well as for the diagnosis of trichuriasis in humans and pigs.