Clinical signs and Symptoms of STH
Soil-transmitted helminthes (STH) is a common infectious disease and caused mainly by the members of helminthes family. It is global health disease and WHO has declared it as a neglected tropical disease. Tropical countries are the main sufferers of this disease. Asia, Central America, Sub-Saharan are the primary area of concern. In this report, the hyper- endemic nature of STH infection in Ethiopia is described. Along with this, the role of Ethiopian government is also highlighted.
The symptoms of STH is visible only when the infection is highly intense. The severity of the disease is associated with the number of worms within the body that means if the number of worms is very large, then the infection will be more severe(1). However, the symptoms are different from hookworm infections, Ascaris and Trichuris infections. Hookworm infections mainly occur by skin penetration. During the hookworm infections, the main clinical symptoms are itching and allergic symptoms like maculopapular rashes. Along with this, pulmonary symptoms are also seen such as pneumonia, sneezing, bronchitis, cough and these symptoms are seen when the larva travels into the lungs. In some cases gastrointestinal symptoms like diarrhoea and other abdominal diseases. In the intestine hookworm is responsible for the blood loss and erosion of mucosal wall. In case of heavy intensity infection anemia is also noted as a symptom of the STH (1). In children, it can cause protein energy malnutrition (PEM) along with anemia(22). The Ascaris infection is mainly associated with the weight loss of the children. The Trichuris infection is mainly caused due to consumptions of contaminated food items and water that contains embryonated eggs of Trichuris. After maturing in the intestine, the worms show the symptoms like abdominal colitis, abdominal bowel disease, and abdominal pain as well. The Trichuris infection results in growth retardation, anemia, clubbing of fingers in the children (2).
STH infections mainly occur due to infections from members of helminthes group such as Trichuris trichiura, Ascaris lumbricoides and by hookworm. The main species of hookworms, that causes STH, are Ancylostomata duodenale and Necator americanus . Children are mainly affected by the Trichuris and Ascaris whereas hookworm attacks both young adults and children(25). Therefore, it can be said that specific occupation is one of the major promoting factors of STH infection. Direct contact with soil promotes the STH infection directly. Influence the hyperactive endemic disease. STH infection is also promoted by the environment, poor sanitation and as well as by the economic condition of the population (3).The transmission of STH infection is transmitted though environment by the contaminated egg carrying faces. Lack of supply in purified water is also responsible for this infection also. Other various factors alternatively promote the infection of STH. In Ethiopia, the occupation of people is a disease-promoting factor. The people who are engaging in the agricultural occupation are more prone to the infection of hookworms as they are comparatively more exposed to the soil in a direct manner (4). The reservoir of this disease is mainly the school going children and have a prevalence rate for example the prevalence rate in North Gondar is 39.8%(7). Moreover,the lack of hygienic practice like washing hand enhances the chances of infection. As the Ascaris eggs have a unique feature that it can adhere to different elements of environment like fruit, door handle, vegetables and as well as dust. The adhesiveness property is due to the coating of mucopolysaccharide on the egg of Ascaris. The adhered eggs then transmitted when anyone touches those door handle or consumes those vegetables and fruits. The unhygienic practices have come from the lack of education in the population of Ethiopia and that ultimately results in a transmission of infection due to lack of proper knowledge about the transmission (5).
Causes of STH
In the transmissin of STH infection, the ecological factors play a crucial role. The sustainability of the helminthes are dependent on the environmental factors like acidity and alkalify of the soil, ambient temperature and moisture level of the soil. In this context the warmness of the weather, moisture in the air, adequate moisture in the soil is maintained by the huge rainfall and it is the common climatic symptoms of tropical countries and as a result the tropical countries are the main area of this endemic disease(6). The egg form of the Ascaris can overcome the adverse condition like dryness and in case of hookworm; it is the larvae, which is responsible for the disease. It stays under the soil to avoid the direct heat of sunlight, as due to heat they will face the morbidity. The temperature and moisture of the air are quite favorable for those parasites to survive. The ecological condition of this region promotes the parasites to survive in the winter and allow perusing the transmission of disease in summer and spring as well(21). As a result, they can transmit the disease throughout the year in their favorable condition. In cold weather, the parasites cannot survive and as a result in the prevalence of infection is low in the high altitude than in lower altitude. In lower altitude mainly at sea level, the higher ambient temperature helps in their transmission(21). Along with this, the rainy nature of mountains causes the washing out of the eggs from the soil. In the plain area, a higher percentage of rainfall creates a high moisture level in the soil and that allows more oxygen to enter the soil (7). The higher level of oxygen in the soil helps the larvae and along with this, the lesser number of pores in the soil allows more suitable transmission and locomotion of the larvae (7). The rainfall in the tropical countries allows some species to avoid the desiccation. On the other hand, less rainfall decreases the release of the larvae. This rainy condition maintains the moisture condition of the soil and as a result, the survival rate of the eggs increases (8). The moisture is very much crucial for the infectious third stage (L3) hookworm larvae and moisture allows them to survive in this condition. Moreover there are few parasites which are very much temperature sensitive and that shows the evolutionary strategies of the menthes family (20). A few species can survive in a high temperature whereas that optimum temperature is lethal for the other one. This indicates towards the fact that ecological factors are very much crucial for the transmission of this endemic disease (9).
Ecology of STH
STH is one of the most common diseases and it affects almost 1.7 billion people in the whole world. From a survey performed in 2003, showed that A.lumcricoides shows the most prevalence of the disease and that is almost 1.2 billion (10).
The contribution of T. trichiura was almost 795 million and the hookworm prevalence was about 740 million. Sub-Saharan Africa and China contribute half of the hook warm prevalence(11).
The highest prevalence rate is seen in Asia and which is about 67% of the total prevalence (11). Within Asia India holds the number one position regarding the contribution of the prevalence of STH. However, rural areas are more susceptible to STH infection than urban areas. In a study, it is seen that the rate of infection in rural areas is almost 20%, whereas this rate is reduced to 5% in case of urban areas (11).
Ethiopia holds the second position in the sub-Saharan Africa region in the context of Ascaris infection and it was almost 26 million (7). Almost 173 million infected population exists in Sub-Saharan Africa (7).STH infection is the most common epidemic disease in Ethiopia and the infection is uniformly distributed in both adults and children (12). Agriculture is a one of the most common profession of the Ethiopians and due to their profession, they are directly exposed to the soil. In rural farming villages, adults are infected by this disease because of their direct contact with the soil (25).
In a recent study, it is seen that in Ethiopia, the schoolchildren are mostly affected and it touches the number of more than 568 million and the infection is mostly in the rural area. 83% of local rural residents may be affected by this infection in Ethiopia (13). The overall prevalence of STH in Ethiopia is almost 54.0% and that indicates that it is a hyper endemic public health issue in Ethiopia(23). This data of South Ethiopia shows that this current prevalence rate is lower than the other part of Ethiopia like Segue peninsula having the prevalence rate of 69.1%, Zarima town having 82.4% of prevalence rate(24) and Northwestern Ethiopia having the prevalence rate of 66.4% (23). However if, the species wise prevalence rate is considered, then A.lumbricoides holds the top position with the prevalence rate of 21.7 %, next comes hookworm with the prevalence rate of 16.7% and finally T.trichiura have the prevalence rate of 7.2% (13). Recently in another study, a parasite named H.Nana was detected as a causal agent of helminthes disease and it had the prevalence rate of almost 4.8% (14). The STH mortality rate is very high in the children age group of 1-4 years for male child and the rate is 0.76 per 100,000 and in case of the female child the rate is 0.71 per 100,000 (15)
Epidemiology
The Ethiopian government has taken several measures like, WASH Programme and MDA Programme, to control and prevent the STH infection among the children and as well as in the adult. Sanitation has a major role in the transmission of STH in the population of Ethiopia. To address this problem the government has aimed to improve the sanitation by lowering the water and soil contamination. Along with this health, education is also very much important in the prevention of STH infection. To increase the rate of health education, the government provides health education in a very simple and economical manner so that maximum number of population can get the advantages of this. In health education programme, the hygienic behavior like the washing of hand ,latrine use is promoted to lower the rate of water and soil contamination. Ultimately, this will help in reducing the STH infection (16). In collaboration with World Health Organization ( WHO) Ethiopia had mapped the STH endemic areas and the Federal Ministry of Health had treated almost 19 million people in the endemic region in 2015 and WHO identified STH as a neglected tropical disease ( NTD)(17). The National control programme had initiated to achieve the deletion of the disease as a public health problem by 2020 and has targeted to achieve transmission break by 2025 to achieve short- term goals (17). In long-term goals, their aim is to abolish morbidity related to STH infection by 2020. Along with this WASH programme is promoted to reduce the prevalence of infection and the aim is to reduce the prevalence by 1%. Some of the short-term goals are to treat almost 75% of schoolchildren, enhance the treatment programme towards the adults, and to lower the rate of infection by 65-90%. Since November 2015, after introducing the programme, almost 19 million people were treated and they targeted to treat 25 million people in the second edition of the treatment programme (18). Federal Ministry of health has introduced another programme for STH infection and it is a Mass Drug Administration (MDA) programme. In MDA, safe, efficacious, inexpensive oral drug of the single dose is given to reduce the worm burden in a large scale and that ultimately reduces the morbidity. Regular treatment with Benzimidazole reduces the risk of infection by keeping the worm burden under the threshold level and this also improves the health condition of the children by maintaining their hemoglobin level in the blood. In the deworming sessions, the health workers cover almost 16.5 million schoolchildren having STH infection in 11 different regions of Ethiopia. The deworming programme should be continued with the sanitation and health literacy programme to abolish the disease (19). In between 1990 -2015, the age related mortality rate in Ethiopia due to STH has decreased by 70.1% (15).
Conclusion
In this report, the epidemic nature of the STH infection in Ethiopia is broadly discussed. Along with this the clinical symptoms, direct and supportive causal agent is depicted. The ecological nature that supports the transmission of the disease is highlighted. The government of Ethiopia along with WHO has taken several preventive measures and has launched various programme to fight this disease. They have various short term and long-term goal and the main target is to abolish the disease by 2025. Deworming programme became very effective as well. However to get success in this programme continuous monitoring is very much essential.
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