An increase in hookworm infection temporally associated with ecologic change

Do natural catastrophic events and exceptional climatic conditions also affect parasites?

Parasites and parasitologists have always lived together in good and bad luck in a sort of forced marriage. In recent times bad luck certainly prevailed, because of increasing man-made emergencies such as wars, chemical disasters, but also because of natural disasters, amplified by climate change, that condition more and more parasite–host equilibrium. The symposium at the National Congress of the Italian Society for Parasitology, was a first occasion for Italian parasitologists to reason about ‘disaster parasitology’ and researchers’ responsibilities. Extreme weather events and their impacts on parasites’ epidemiology are illustrated, comparing disasters that recently occurred in Italy with literature data. In particular, the Sardinian Island was hit subsequently by fires and floods exacerbating the effects on ecosystems and parasite–host-relationships. Examples of Cryptosporidium outbreaks in man and Fasciola hepatica infections in various hosts after heavy rains are reviewed and effects of droughts on pasture borne parasites, such as gastro-intestinal nematodes of ruminants are discussed. Heavy rains may also cause dissemination of toxic substances released accidentally from chemical plants as happened e.g. in Milan province (IT) after the dioxin hazard. The overlapping effects of strictly man-made disasters with climate change dependent extreme weather events is further challenging the understanding of what are the consequences of disasters on ecosystems and parasite epidemiology.GIS applications combined with AI programs may help to face the complex challenges, allowing the collection and analysis of spatial/temporal data at whatever level desired. Examples illustrated in the article suggest their employment also in a more systematic, prevention-oriented manner.

Why Are We Still a Worm World in the 2020s? An Overview of Risk Factors and Endemicity for Soil-Transmitted Helminthiasis

PURPOSE

Soil-transmitted helminthiasis (STH) is one of the most common chronic infections in developing countries associated with poor socioeconomic and sanitary conditions. The main objective of this overview was to evaluate the influence of environmental factors, risk factors related to the host, and control strategies on the prevalence of STH in different regions of the world.

METHODS

LILACS, PubMed, Web of Knowledge, Embase, the Cochrane Library, and Clinical Trials (gray literature) databases were used to obtain the systematic reviews published until December 2020. The methodological quality of systematic reviews was assessed using the standard criteria recommended by AMSTAR.

RESULTS

The initial results of the bibliographic search identified 1448 articles, of which 66 studies were read in full and 16 met the inclusion criteria. All the reviews included in this overview associated variations in the global prevalence of STH with at least one of the factors related to the environment, host, and/or control strategies. Climate, temperature, soil moisture, precipitation, mass drug administration, lack of access to water, sanitation and hygiene (WASH), and non-use of footwear were considered the main factors associated with the prevalence of STH. Socioeconomic factors, low educational level, and wearing shoes were universal factors related to prevalence, regardless of the location studied.

CONCLUSION

The combination of environmental factors, with factors associated with hosts that predispose infection and reinfection of helminths, as well as the adoption of control strategies based on the treatment of target populations instead of the entire population, influenced the prevalence of STH in all the continents evaluated.

Influence of extraordinary floods on wildlife parasites: the case of gastrointestinal helminths and protozoa of wild canids from the Iberá Ecoregion, Argentina

Parasites are natural components of ecosystems and play a significant role in the dynamics of wild animal populations. Although the environment of parasites is primarily defined by the host, most life cycles involve stages that must endure external conditions. Rainfall and flooding events are important factors that might influence the transport of parasitic stages, altering soil moisture levels, and resulting in a favorable environment for parasite survival and development. We assessed whether an extraordinary flood event modified the occurrence of gastrointestinal parasites (nematodes and protozoa) in wild canids in two protected areas in northern Argentina. From 2016 to 2018, we collected fecal samples of two fox species, Lycalopex gymnocercus and Cerdocyon thous, and examined the presence of nematodes and protozoa. We assessed changes in the occurrence of these parasites after a flood event, while adjusting for potential confounders (i.e., monthly average temperature, season, host species, site). In a second stage of the analysis, we evaluated whether part of the effect was caused by changes in soil moisture, by adding normalized difference water index as an independent variable. We found that the presence of nematodes in foxes was higher after flooding than before flooding, and this association was not explained by changes in the soil moisture. On the other hand, the flood event was not relevant for protozoa. Stronger and long-lasting flood events are expected due to the effect of global warming on El Niño events, and this may increase and intensify the spread of some parasites affecting wildlife, which could also be of public health concern.

Dietary intake, forest foods, and anemia in Southwest Cameroon

BACKGROUND

Forest cover has been associated with higher dietary diversity and better diet quality in Africa. Anemia prevalence among women of reproductive age in sub-Saharan Africa is very high and diet is one known contributor of a high prevalence rate. We investigated whether living in communities with high forest cover was associated with better diet quality and lower anemia prevalence among women of reproductive age in Southwest Cameroon.

METHODOLOGY

We conducted a cross-sectional survey of 247 women of reproductive age from four forest-based villages (n = 126) and four non-forest villages (n = 121). We assessed the Hemoglobin (Hb) levels, anthropometric status, and diet (by 24-hour recall), as well as anemia-related morbidity and socio-demographic characteristics. Differences between groups were assessed with Pearson's chi-square and independent T-tests. We used a number of multivariate regression models to estimate the impacts of forest proximity on adjusted hemoglobin status of women of reproductive age, as well as to identify the most likely pathway through which forest proximity was important.

RESULTS

We found that women living in forest communities had higher adjusted hemoglobin levels (mean hemoglobin concentration 11.10±1.53 g/dl vs.10.68±1.55g/dl; p = 0.03 for women forest and non-forest communities respectively). Moderate to severe anemia prevalence was significantly higher in women living in the non-forest villages compared to women in forest villages (forest 63% vs. 73%; p = 0.04). Compared with women from non-forest villages, women from forest-based villages had consumed significantly more vitamin A rich fruits and vegetables and animal source foods, and more of these came from the forest (as opposed to the farm or purchased sources). We found that the consumption of Gnetum africanum (Eru), a leafy green vegetable that grows in forests of the Congo Basis, was best able to account for the higher levels of adjusted hemoglobin in women in forest communities.

CONCLUSION

This study contributes to the growing evidence that in some circumstances, forests make important contributions to diet quality and nutrition. The results of this study suggest that plant foods from the forest may make important contributions to iron intake and reduce the risk of anemia in women. Efforts to prevent forest loss and maintain ecosystem services are warranted to enhance nutrition and health of forest-based communities.

Animals and Human Health

Human health and animal health are closely intertwined. We share hundreds of diseases with animals, and they are vectors for many diseases that assail humans—but, at the same time, they are essential to many treatments and cures. We discuss in this chapter various aspects of intimate relationship between human and animal health, giving examples of the importance of multidisciplinary studies in understanding these connections and the fundamental aspects of strategies for promoting the health and well-being of both groups.

Climate Change Contribution to the Emergence or Re-Emergence of Parasitic Diseases

The connection between our environment and parasitic diseases may not always be straightforward, but it exists nonetheless. This article highlights how climate as a component of our environment, or more specifically climate change, has the capability to drive parasitic disease incidence and prevalence worldwide. There are both direct and indirect implications of climate change on the scope and distribution of parasitic organisms and their associated vectors and host species. We aim to encompass a large body of literature to demonstrate how a changing climate will perpetuate, or perhaps exacerbate, public health issues and economic stagnation due to parasitic diseases. The diseases examined include those caused by ingested protozoa and soil helminths, malaria, lymphatic filariasis, Chagas disease, human African trypanosomiasis, leishmaniasis, babesiosis, schistosomiasis, and echinococcus, as well as parasites affecting livestock. It is our goal to impress on the scientific community the magnitude a changing climate can have on public health in relation to parasitic disease burden. Once impending climate changes are now upon us, and as we see these events unfold, it is critical to create management plans that will protect the health and quality of life of the people living in the communities that will be significantly affected.

Geohelminths distribution as affected by soil properties, physicochemical factors and climate in Sharkyia governorate Egypt

Soil-transmitted helminths are mainly a group of parasitic nematodes causing human infection through contact with parasite eggs or larvae; they survive in the warm and moist soil of the tropical and subtropical countries. This study was carried out in Sharkyia governorate from October, 2011 to October, 2013, to correlate between the prevalence and distribution of these parasites in the soil and the physicochemical factors affecting the examined samples of the soil. One hundred and twenty samples of different types of soil (clay, silt, sand) from different localities were collected and examined. Diagnosis of geohelminths was confirmed by the recovery of their eggs and larvae with other protozoa by different parasitological methods. The modified baermann method was found to be more efficient in detection of geohelminths larvae than charcoal culture method. Among the examined sites geohelminths were much more numerous in the soil of rural areas especially in the spring and summer seasons, while the contamination of canal banks by geohelminths was the worst (80 %). An insignificant correlation was reported between the soil texture and the number of positive samples in the examined areas while the relationship was directly proportional among (moisture, PH, organic). It appeared that the most common geohelminthic stage was Toxocara spp. eggs besides other types of protozoa especially Balantidium coli cysts. This suggests that factors other than soil texture are important in the prevalence of geohelminths in the soil e.g. temperature, moisture, PH and organic matter. So, to change some of these factors in a trial to control geoparasites transmission but with keeping the environment should be tried. These results also open the way to further studies to highlight the mutual affection between inhabitants of these sites and the prevalence of these geoparasites.

Longitudinal monitoring of the development of antifilarial antibodies and acquisition of Wuchereria bancrofti in a highly endemic area of Haiti

Antifilarial antibody testing has been established as a sensitive and specific method of diagnosing lymphatic filariasis. However, the development of serological responses to specific filarial antigens and their relationship to acquisition of infection is poorly understood. In order to evaluate whether the development of antigen specific antifilarial antibodies precedes microfilaremia and antigenemia, we compared the antibody responses of serum samples collected between 1990 and 1999 from a cohort of 142 Haitian children followed longitudinally. Antigen status was determined using the Og4C3 ELISA and the presence of microfilaremia was detected using microscopy. Antibody responses to Wb123, a Wuchereria bancrofti L3 antigen, were measured using a Luciferase Immunoprecipitation System (LIPS) assay. Antibody responses to Bm14 and Bm33, Brugia malayi antigens and to a major surface protein (WSP) from Wolbachia were analyzed using a multiplex bead assay. Over follow-up, 80 (56%) of the children became antigen-positive and 30 (21%) developed microfilaremia. Detectable antibody responses to Bm14, Bm33, Wb123, and WSP developed in 95%, 100%, 92%, and 29% of children, respectively. With the exception of WSP, the development of antibody responses generally preceded detection of filarial antigen. Our results show that antifilarial antibody responses can serve as an important epidemiological indicator in a sentinel population of young children and thus, may be valuable as tool for surveillance in the context of lymphatic filariasis elimination programs.

Programs to eliminate lymphatic filariasis (LF) are designed to interrupt transmission of the parasite by treating the human reservoir of infection. As infection levels decline, assessing infection and transmission levels becomes more and more challenging. In principle, measuring the level of antibody to filarial antigens in children may provide a sensitive measure of transmission intensity. Here, we used samples collected over time from 142 Haitian children living in an area of intense transmission of LF to determine when they first developed antibody responses to defined filarial antigens compared to when they became infected. Antibody responses were measured to several filarial antigens using sensitive assays based on multiplex and LIPS assay methods. Our results show that antibody responses developed before infection could be detected by conventional tests for the presence of microfilariae or antigen in the blood. These results support the idea that antibody tests can be used to monitor the impact of mass drug administration programs on transmission of LF and to carry out surveillance for LF after drug treatments have stopped.

Poly-helminth Infection in East Guatemalan School Children

BACKGROUND

Soil transmitted helminths (STH) remain a global public health concern in spite of occasional dosing campaigns.

AIMS

To determine baseline prevalence and intensity of STH infection in east Guatemalan school children, and describe the associated epidemiology of anemia, stunting, and wasting in this population.

SETTING AND DESIGN

Ten schools in Izabal province (eastern Guatemala) were identified, and 1,001 school children were selected for this study. Half of the schools were used as clinical testing sites (blood and stool).

MATERIALS AND METHODS

Anthropometric measures were collected from all children. Over 300 children were tested for anemia and 229 for helminth infection. Ova and parasite specimens were examined via Direct, Kato Katz, and McMaster techniques. Hemoglobin was measured from venipuncture following the hemacue system.

STATISTICAL ANALYSIS

Correlation between infection intensities and growth indicators were examined. Chi Square or t tests were used for bivariate analysis. Multiple logistic regression was performed on significant variables from bivariate techniques.

RESULTS

Over two-thirds of school children were positive for infection by any STH. Prevalence of Hookworm was 30%; Ascaris, 52%; and Trichuris, 39%, most as low-intensity infection. Over half of the children were co-infected. In bivariate analysis, anemia was significantly associated with polyparasitism.

CONCLUSIONS

For a Guatemalan child who experiences a unit decrease in hemoglobin, one expects to see a 24% increase in the odds of being infected with STH, controlling for age, sex, lake proximity, and growth characteristics. Infection with more than one STH, despite low intensity, led to a significant decrease in hemoglobin.

The control of hookworm infection in China

BACKGROUND

Hookworm is still one of the three main soil-transmitted helminths prevalent in China, and 39 million cases infected with hookworm were estimated in China in 2006.

RESULTS

The main approach to the control of hookworm infections in China consists of large-scale deworming, rebuilding sanitation systems in rural areas and health education. The availability of low-cost, safe and single-dose albendazole make large-scale deworming programs possible in China. Currently, sanitary latrines with three-cells are recommended by government for the control of soil-transmitted helminths, since 35% of helminth infections and 83% of worm eggs could be reduced after using this kind of sanitary latrine. In addition, economic prosperity contributes greatly to the reduction of hookworm prevalence, but the inequity of economic and social development among different regions of China provides a scenario that the worst threat of hookworm infection is located in the poorest areas of southern and central China. Therefore, it is necessary to put more investments into prophylaxis and treatment of hookworm in these poor regions.

CONCLUSION

Although the prevalence of hookworm infection has fallen significantly in the last 15 years in China, the current strategy for controlling hookworm infections still needs to be strengthened along with the three-pronged approach, e.g. distributing anthelmintic drugs in schools and undertaking large-scale of hookworm deworming, improving water supplies and sanitation, and proper health education.

Ecology of Increasing Diseases: Population Growth and Environmental Degradation

The World Health Organization (WHO) and other organizations report that the prevalence of human diseases during the past decade is rapidly increasing. Population growth and the pollution of water, air, and soil are contributing to the increasing number of human diseases worldwide. Currently an estimated 40% of world deaths are due to environmental degradation. The ecology of increasing diseases has complex factors of environmental degradation, population growth, and the current malnutrition of about 3.7 billion people in the world.

Wildlife trade and global disease emergence

The global trade in wildlife provides disease transmission mechanisms that not only cause human disease outbreaks but also threaten livestock, international trade, rural livelihoods, native wildlife populations, and the health of ecosystems. Outbreaks resulting from wildlife trade have caused hundreds of billions of dollars of economic damage globally. Rather than attempting to eradicate pathogens or the wild species that may harbor them, a practical approach would include decreasing the contact rate among species, including humans, at the interface created by the wildlife trade. Since wildlife marketing functions as a system of scale-free networks with major hubs, these points provide control opportunities to maximize the effects of regulatory efforts.