The influence of pregnancy on intestinal parasite infection in Thai women

Prevalence of intestinal parasitic infections among the pregnant women in South and South East Asian countries: A systematic review and meta-analysis

Intestinal parasitic infections (IPIs) are a major health concern in resource-limited countries of South/South-East Asian region. Despite posing a potential threat to maternal and fetal health, there is limited data available on the actual burden of IPI among pregnant women. Through this systemic review and meta-analysis, we sought to determine the pooled prevalence of IPI and species-specific prevalence among pregnant women in this region. Subgroup analysis was done by region, stool examination technique, and study settings. Among 220 retrieved studies, 21 studies from 8 countries across the region were found eligible and included in this study. The estimated overall pooled prevalence of IPIs among pregnant women was 43.15% (95% confidence interval: 30.66-56.10). The most prevalent IPI was Ascaris lumbricoides (25.14%) and predominant protozoa was Entamoeba histolytica/dispar (6.96%). In subgroup analysis, the estimated pooled prevalence of IPIs in Nepal, India, Thailand, and Thai-Burmese Border was 40.88%, 28.33%, 55.38%, and 23.78%, respectively. Studies using Kato-Katz technique for stool examination showed the highest estimated pooled IPI prevalence (62.70%). The prevalence of IPI was found to be lower in facility-based studies (38.12%) than that of studies done in the community (66.21%). Considering the high burden of IPI in pregnant women as estimated in our review and the already established impact of IPI infection on maternal health and fetal outcomes, we recommend implementation of the preventive chemotherapy during routine antenatal checkups.

Foodborne zoonotic parasites of the family Opisthorchiidae

Several foodborne zoonotic trematodes of the family Opisthorchiidae have been reported to infect people, specifically two genera, Clonorchis and Opisthorchis. Three species Clonorchis sinensis, Opisthorchis felineus and Opisthorchis viverrini are the most extensivley studied of the Opisthorchiidae. At least 680 million people worldwide are at risk of infection of these liver flukes through the consumption of raw or partially cooked freshwater cyprinid fish. An estimated 45 million people in Europe and Asia are currently infected with these liver flukes. Of these, the 35 million are infected with C. sinensis mainly in China, 10 million with O. viverrini in Southeast Asia, and 1.2 million with O. felineus in Eastern Europe and Russia. These liver flukes have been proven to be causative agents of bile duct cancer or cholangiocarcinoma (CCA). A multidisciplinary program should be implemented involving comprehensive research on molecular genetics, diagnosis, treatment, prevention, as well as educational and control programs should progressively be introduced and applied in endemic regions of O. viverrini, O. felineus and C. sinensis throughout their ranges, hence, opisthorchiasis and clonorchiasis free communities can be realised globally.

Old friends and friendly fire: Pregnancy, hookworm infection, and anemia among tropical horticulturalists

OBJECTIVES

Despite public health concerns about hookworm infection in pregnancy, little is known about immune profiles associated with hookworm (Necator americanus and Ancylostoma duodenale) infection during pregnancy. Fetal tolerance requirements may constrain maternal immune response to hookworm, thereby increasing susceptibility to new infections or increasing hemoglobin loss. To explore this possibility, we study systemic immune response and hemoglobin levels in a natural fertility population with endemic helminthic infection.

METHODS

We used Bayesian multilevel models to analyze mixed longitudinal data on hemoglobin, hookworm infection, reproductive state, eosinophils, and erythrocyte sedimentation rate (ESR) to examine the effects of pregnancy and hookworm infection on nonspecific inflammation, cellular parasite response, and hemoglobin among 612 Tsimane women aged 15-45 (1016 observations).

RESULTS

Pregnancy is associated with lower eosinophil counts and lower eosinophil response to hookworm, particularly during the second and third trimesters. Both hookworm and pregnancy are associated with higher ESR, with evidence for an interaction between the two causing further increases in the first trimester. Pregnancy is moderately associated with higher odds of hookworm infection (OR: 1.23, 95% CI: 0.83 to 1.83). Pregnancy and hookworm both decrease hemoglobin and may interact to accentuate this effect in the first-trimester of pregnancy (Interaction: β: -0.30 g/dL; CI: -0.870 to 0.24).

CONCLUSIONS

Our findings are consistent with a possible trade-off between hookworm immunity and successful pregnancy, and with the suggestion that hookworm and pregnancy may have synergistic effects, particularly in the first trimester.

Taxonomy, Ecology and Population Genetics of Opisthorchis viverrini and Its Intermediate Hosts

There have been considerable advances in our understanding of the systematics and ecology of Opisthorchis viverrini; however, this new knowledge has not only clarified but also complicated the situation. We now know that what was once considered to be a single species is, in fact, a species complex, with the individual species being confined to specific wetland areas. There is also a strong genetic association between the members of the O. viverrini species complex and their Bithynia snail intermediate hosts. Although this does not negate data collected before the recognition of this situation, it does lead to the caveat that regional and temporal variations in data collected may be related to the species examined. The advances in ecology have generally been spatially limited and have led, in part, to contradictory results that may well be related to nonrecognition of the species studied. It may also be related to natural temporal and spatial variation related, for example, to habitat characteristics. To understand the variation present, it will be necessary to conduct long-term (several years at least) sampling projects after defining the genetic characteristics of O. viverrini sensu lato and its Bithynia snail intermediate hosts.

Pregnancy and helminth infections

It has been proposed that helminth infection may be particularly detrimental during pregnancy, through adverse effects on maternal anaemia and on birth outcomes, and that anthelminthic treatment during pregnancy will therefore be particularly beneficial. However, the few treatment trials that have been conducted have given, but little support to this notion and further trials in settings of nutritional stress are needed. It has also been proposed that prenatal exposure to helminth infection has an important effect on the development of the foetal immune response. There is evidence that this may impact, long-term, upon responses to helminth and nonhelminth antigens, and to allergens. Exposure to helminths in utero may also have nonspecific effects that may modify the offspring's susceptibility to diseases mediated by inflammation, including metabolic disorders. The mechanisms of such effects are not known, but they deserve to be explored as current epidemiological findings suggest the possibility of primary prevention for inflammatory conditions such as allergy, through intervention during pregnancy.

Molecular analysis of echinostome metacercariae from their second intermediate host found in a localised geographic region reveals genetic heterogeneity and possible cryptic speciation

Echinostome metacercariae are the infective stage for humans and animals. The identification of echinostomes has been based until recently on morphology but molecular techniques using sequences of ribosomal RNA and mitochondrial DNA have indicated major clades within the group. In this study we have used the ITS2 region of ribosomal RNA and the ND1 region of mitochondrial DNA to identify metacercariae from snails collected from eight well-separated sites from an area of 4000 km² in Lamphun Province, Thailand. The derived sequences have been compared to those collected from elsewhere and have been deposited in the nucleotide databases. There were two aims of this study; firstly, to determine the species of echinostome present in an endemic area, and secondly, to assess the intra-specific genetic diversity, as this may be informative with regard to the potential for the development of anthelmintic resistance and with regard to the spread of infection by the definitive hosts. Our results indicate that the most prevalent species are most closely related to E. revolutum, E. trivolvis, E. robustum, E. malayanum and Euparyphium albuferensis. Some sites harbour several species and within a site there could be considerable intra-species genetic diversity. There is no significant geographical structuring within this area. Although the molecular techniques used in this study allowed the assignment of the samples to clades within defined species, however, within these groupings there were significant differences indicating that cryptic speciation may have occurred. The degree of genetic diversity present would suggest the use of targeted regimes designed to minimise the selection of anthelmintic resistance. The apparent lack of geographic structuring is consistent with the transmission of the parasites by the avian hosts.

Infections by food-borne trematodes are estimated to infect over 40 million people worldwide, although infections by echinostomes make up only a portion of these cases, usually in regions where their prevalence is high. In South East Asia and in the far east of Asia, human infection is associated with cultural and dietary factors and the prevalence of infection may reach 50% in parts of Thailand, Cambodia, and Laos. Treatment is generally dependent on the use of praziquantel or benzimidazole drugs but with the occurrence of anthelmintic resistance to these compounds it would be desirable to have an understanding of the diversity present in the echinostome populations within a given locality. This study deals with the systematics of echinostomes and informs various aspects of the epidemiology of echinostomiasis which may aid the development of future control strategies.

Helminthic infections rates and malaria in HIV-infected pregnant women on anti-retroviral therapy in Rwanda

Background

Within sub-Saharan Africa, helminth and malaria infections cause considerable morbidity in HIV-positive pregnant women and their offspring. Helminth infections are also associated with a higher risk of mother-to-child HIV transmission. The aim of this study was to determine the prevalence of, and the protective and risk factors for helminth and malaria infections in pregnant HIV-positive Rwandan women receiving anti-retroviral therapy (ART).

Methodology and principle findings

Pregnant females (n = 980) were recruited from health centres in rural and peri-urban locations in the central and eastern provinces of Rwanda. Helminth infection was diagnosed using the Kato Katz method whilst the presence of Plasmodium falciparum was identified from blood smears. The prevalence of helminth infections was 34.3%; of malaria 13.3%, and of co-infections 6.6%. Helminth infections were more common in rural (43.1%) than peri-urban (18.0%; p<0.0005) sites. A CD4 count ≤350 cells/mm³ was associated with a higher risk of helminth infections (odds ratio, 3.39; 95% CIs, 2.16–5.33; p<0.0005) and malaria (3.37 [2.11–5.38]; p<0.0005) whilst helminth infection was a risk factor for malaria infection and vice versa. Education and employment reduced the risk of all types of infection whilst hand washing protected against helminth infection (0.29 [0.19–0.46]; p<0.0005);). The TDF-3TC-NVP (3.47 [2.21–5.45]; p<0.0005), D4T-3TC-NVP (2.47 [1.27–4.80]; p<0.05) and AZT-NVP (2.60 [1.33–5.08]; p<0.05) regimens each yielded higher helminth infection rates than the AZT-3TC-NVP regimen. Anti-retroviral therapy had no effect on the risk of malaria.

Conclusion/significance

HIV-positive pregnant women would benefit from the scaling up of de-worming programs alongside health education and hygiene interventions. The differential effect of certain ART combinations (as observed here most strongly with AZT-3TC-NVP) possibly protecting against helminth infection warrants further investigation.

There is an overlap in the worldwide distribution of intestinal worms (helminths), malaria and HIV. Co-infections with helminth and malaria parasites cause a significant problem in the host, particularly in the presence of HIV infection. The aim of this study was to assess the prevalence of intestinal worm and malaria infection and co-infections and the associated risk factors among HIV-positive pregnant women that attended rural and peri-urban health centers in Rwanda. Our findings indicate that intestinal worms were more common among HIV-infected pregnant women in the rural than peri-urban settings. HIV-positive pregnant women who had lower CD4 cell counts were more at risk of being infected by intestinal worms and malaria. Malaria also increased the risk of being infected by intestinal worms and vice versa. Socio-economic factors such as lack of education and unemployment were among the risk factors for intestinal worm infections and malaria. Hand washing was found to reduce the risk for worm infections; whilst one particular ART combination (AZT-3TC-NVP) led to a reduced rate of helminth infections when compared to others.

Immunological footprint: the development of a child's immune system in environments rich in microorganisms and parasites

The shaping of a child's immune system starts in utero, with possible long-term consequences in later life. This review highlights the studies conducted on the development of the immune system in early childhood up to school-age, discussing the impact that environmental factors may have. Emphasis has been put on studies conducted in geographical regions where exposure to micro-organisms and parasites are particularly high, and the effect that maternal exposures to these may have on an infant's immune responses to third-party antigens. In this respect we discuss the effect on responses to vaccines, co-infections and on the development of allergic disorders. In addition, studies of the impact that such environmental factors may have on slightly older (school) children are highlighted emphasizing the need for large studies in low to middle income countries, that are sufficiently powered and have longitudinal follow-up components to understand the immunological footprint of a child and the consequences throughout life.

Influence of pregnancy on Trypanosoma cruzi parasitemia in chronically infected women in a rural Bolivian community

To determine the role of pregnancy on Trypanosoma cruzi parasitemia, a matched cohort study was carried out in a rural Bolivian community comparing parasite rates in gravidae, puerperae, and non-pregnant infected women. A selection of 67 chronically infected women, who delivered between March 2004 and May 2005, were initially evaluated during the third trimester of pregnancy and again after delivery. They were matched for age, parity, and location with 104 seropositive non-pregnant women, who likewise had submitted blood for microscopic examination for T. cruzi parasites in June 2005. Seroreactive pregnant women had a higher rate of T. cruzi parasitemia (14.9%) than matched non-pregnant infected women (2.9%; P = 0.004). After delivery, parasitemia significantly decreased during puerperium (1.5%) compared with the period of pregnancy (14.9%; P = 0.03). This study showed an increase of parasite loads in maternal peripheral blood, during the third trimester, and a significant decline after delivery.

Multiparasitism a neglected reality on global, regional and local scale

This review focuses on the issue of multiparasitism, with a special emphasis on its characteristics, its extent in eastern Asia and its significance for infectious disease control. Multiparasitism is pervasive among socially and economically disadvantaged or marginalised communities, particularly in tropical and subtropical areas. Intestinal parasites are the most numerous group, but an array of parasites is located elsewhere than in the human gastrointestinal tract. Although multiparasitism has been recognised for decades, in-depth studies are rare, and its public health and economic implications have yet to be fully elucidated. The assessment of multiparasitism is hampered by a lack of sensitive broad-spectrum diagnostic tools and the need to collect multiple biological samples for detailed appraisal. Non-specific symptoms and mainly subtle effects complicate the appreciation of its influence on cognitive and physical development, health, economic productivity and general well-being. Multiparasitism has been reported from virtually every eastern Asian country, and studies regarding the extent of multiparasitism and its effects on child health have been implemented in the region. However, new research is needed, as no comprehensive evaluations of multiparasitism in eastern Asia could be identified. Two case studies pertaining to multiparasitism at the local and regional scale are presented. Multiparasitism was rampant in an ethnic minority village in southern People's Republic of China where the challenges associated with its thorough evaluation are illustrated. The results from a cross-sectional survey covering 35 villages highlight the significance of its evaluation for the design of locally adapted and sustainable parasite control and poverty alleviation programmes. We conclude by listing a set of research needs for future investigations.

Risk factors for helminth, malaria, and HIV infection in pregnancy in Entebbe, Uganda

Background

Infections during pregnancy may have serious consequences for both mother and baby. Assessment of risk factors for infections informs planning of interventions and analysis of the impact of infections on health outcomes.

Objectives

To describe risk factors for helminths, malaria and HIV in pregnant Ugandan women before intervention in a trial of de-worming in pregnancy.

Methods

The trial recruited 2,507 pregnant women between April 2003 and November 2005. Participants were interviewed and blood and stool samples obtained; location of residence at enrolment was mapped. Demographic, socioeconomic, behavioral and other risk factors were modelled using logistic regression.

Results

There was a high prevalence of helminth, malaria and HIV infection, as previously reported. All helminths and malaria parasitemia were more common in younger women, and education was protective against every infection. Place of birth and/or tribe affected all helminths in a pattern consistent with the geographical distribution of helminth infections in Uganda. Four different geohelminths (hookworm, Trichuris, Ascaris and Trichostrongylus) showed a downwards trend in prevalence during the enrolment period. There was a negative association between hookworm and HIV, and between hookworm and low CD4 count among HIV-positive women. Locally, high prevalence of schistosomiasis and HIV occurred in lakeshore communities.

Conclusions

Interventions for helminths, malaria and HIV need to target young women both in and out of school. Antenatal interventions for malaria and HIV infection must continue to be promoted. Women originating from a high risk area for a helminth infection remain at high risk after migration to a lower-risk area, and vice versa, but overall, geohelminths seem to be becoming less common in this population. High risk populations, such as fishing communities, require directed effort against schistosomiasis and HIV infection.

Infections in pregnancy can cause miscarriage, stillbirth, maternal mortality, and low birth weight and have other long-term complications for mother and baby, although the full impact of many infections, particularly worm infections, is not yet fully understood. There is a high burden of infectious disease in many developing countries. In this analysis, we identified which factors put pregnant women in Entebbe, Uganda, at particular risk for worm infections, malaria, HIV, and, where possible, rarer infections including syphilis. The women in this study, and their children, will be followed up to determine the long-term effects of exposure of the fetus to these maternal infections on health during childhood. The findings of this baseline analysis will help in the interpretation of the long-term outcomes. The findings also highlight which groups are most at risk of each infection, and this may help in targeting interventions to prevent, treat, or mitigate the impact of infections in pregnancy.